Eremopezus
Encyclopedia
Eremopezus is a prehistoric bird
genus
. It is known only from the fossil
remains of a single species
,
the huge and presumably flightless Eremopezus eocaenus. This was found in Upper Eocene Jebel Qatrani Formation
deposits around the Qasr el-Sagha escarpment
, north of the Birket Qarun lake near Faiyum in Egypt
. The rocks its fossil
s occur in were deposited in the Priabonian
, with the oldest dating back to about 36 million years ago (Ma) and the youngest not less than about 33 Ma.
It is not precisely known from which strata
the first few remains of this bird were collected. They were formerly considered of Early Oligocene age—some 33-30 Ma—but this is now assumed incorrect, as only the upper and not the entire Jebel Qatrani Formation is of Oligocene age. It is also possible that they are from the slightly older Qasr el-Sagha Formation, but as both this and the Oligocene parts of the Jebel Qatrani Formation were laid down in an ecosystem
markedly different from that of the Eocene Jebel Qatrani Formation, it is nowadays assumed that all material of E. eocaenus is from the lowest rocks of the Jebel Qatrani Formation.
piece (specimen BMNH
A843); a toe
phalanx bone found soon thereafter was tentatively assigned to this bird. Eremopezus was initially believed a ratite
and loosely allied with the elephant bird
s of Madagascar
. Thus, when a piece of tarsometatarsus
shaft was found some time later north of the ruins of Dimeh (Dimê
; itself a bit north of the Birket Qarun) this was described as Stromeria fajumensis; though it had a size to match the holotype
tibiotarsus it was thought to resemble an elephantbird even more. The shaft (specimen BSPG 1914 I 53) has a prominent plantar (backside) ridge also found in Mullerornis betsilei, and this was used to ally the fossil bone with this rather small and gracile elephant bird. The Eremopezus specimen on the other hand has deep ligament
al pits on the lateral and medial
sides of the distal condyles, which are not found in the elephant birds proper. These pits together with a crisply defined ridge held a sling of ligament
, which in turn—in place of the bony
supratendinal bridge found in some other birds—kept the ankle
tendons from dislocating. The tarsometatarsus is also more similar to that of an unspecific ratite, such as an emu
, ostrich
or rhea
, rather than to the apomorphic one of the elephantbirds.
Almost 100 years after the discovery of the holotype, more Eremopezus fossils were unearthed from the famous quarry
L-41 at Tel Akgrab near 29°36′20"N 30°30′00"E. These are also all leg
and foot
bones, namely specimens DPC 20919 (a distal right tibiotarsus and its entire tarsometatarsus), DPC 5555 (the lower half of a left tarsometatarsus) and DPC 18309 (the distal end of a left tarsometatarsus).
Some fossil eggshell
s from the Maghreb
, described as Psammornis and resembling those of ratite eggs, were assigned to Eremopezus by various authors. They were at first believed to date form the Paleogene
also, but today are generally considered far younger (of late Neogene
age, probably less than 5 Ma) and indeed to have been laid by ostriches or close relatives thereof.
The scientific name Eremopezus eocaenus is rather ambiguous in meaning; a possible translation is "walking hermit from the Eocene". Eremos (ἐρῆμος) is an Ancient Greek
term signifying a lonely or solitary place or person: a hermit
, a desert
or a wasteland. Yet while Faiyum is located at the edge of the Libyan Desert
, it is a well-vegetated location even today; some 35-30 MA it was a lush region and teemed with life. On the other hand, is it not at all likely that such a large and quite likely predatory bird like E. eocaenus was in any way gregarious or occurred at high population densities. It might therefore be described as a "hermit" with some justification, but certainly not as a "desert-dweller". pezus is Latin
ized Greek from pezós (πεζός), "someone who walks". eocaenus refers to the bird's age; as noted, the initial 1904 assessment of C. W. Andrews was indeed correct. Stromeria fajumensis was named in honor of the paleontologist Ernst Stromer von Reichenbach, and the bone's place of discovery.
es and elephant bird
s (the only ratites biogeographically close to Eremopezus). Moreover, the prehistoric bird had several peculiar traits not at all found in ratites, but present in certain neognaths: its toes were widely divergent and could flex through a wide range of positions, while strong tendon
s gave the bird a firm grip. In the associated anatomical details, E. eocaenus resembled the Secretarybird (Sagittarius serpentarius) and the Shoebill
(Balaeniceps rex), two rather singular Africa
n endemics.
The Secretarybird is a bird of prey
that can fly well, but prefers to walk around on its long legs, especially when foraging. It uses its flexible toes to grab prey—large arthropod
s and small to mid-sized terrestrial
vertebrate
. It throws the prey around and kicks it forcefully, smashing it to death or breaking its spine
. The Shoebill, meanwhile, for lack of a better theory was long considered a large aberrant stork
relative in the Ciconiiformes
. This eventually proved incorrect. While B. rex is indeed a member of the same group of "higher waterbirds" as are storks and heron
s, it is closely related to pelican
s and thus came to be included in the Pelecaniformes
—which are not monophyletic as described in old times, however, and whose small core group, for simplicity, is included in the Ciconiiformes by some recent authors. Insofar, the Shoebill is today recognized as the formerly missing link
uniting pelicans and storks. Like the pelicans, it uses its massive bill and throat sac to catch large fish
and similar aquatic
vertebrates, but unlike them it is a wading, not a swimming bird, and correspondingly has long legs like a stork. It clambers through reedbeds in search of good fishing spots, and uses its flexible toes to firmly hold on to such uncertain substrate
as heaps of wind-blown vegetation at the edge of the open water or roots and logs of tree
s.
But this does not mean that Eremopezus was a close relative of either Secretarybird or Shoebill. Even though modern taxonomy
generally tries to avoid using monotypic
families as much as possible, its placement in a distinct family Eremopezidae may well be warranted, as its closest relatives remain completely obscure.
For the birds of prey, a Paleocene
(perhaps even Late Cretaceous
) origin seems most likely; the first fossils of the present-day lineages (and some entirely extinct forms) are abundant in Eocene
strata of the Holarctic
, particularly Europe
. The falcon
s seem to have rapidly spread throughout the Americas
, where the plesiomorphic caracara
s are found. The other diurnal raptors, family
Accipitridae
—by some considered more distinct, as core group of an order
Accipitriformes –, apparently diversified eastwards into Asia
and eventually into Africa.
As regards the Secretarybird, the genus
Pelargopappus occurred at about the same time as E. eocaenus in today's France
, separated from the site of Faiyum by more than 1,500 km of the shrinking Tethys Sea. The Maghreb
was closer to Europe however, not more than today's Mediterranean where it is widest, and numerous bird lineages are known to have occurred in Africa as well as in Europe during the Eocene. Pelargopappus seems to be an ancient secretarybird, not an ancestor of the living species but not far removed from the last common ancestor either. Its remains, and how they differ from secretarybirds, give an idea how the Sagittariidae of that time looked like. So even though Pelargopappus has not yet been directly compared to the African fossil in a cladistic analysis, the pronounced differences between Eremopezus and Sagittarius and the biogeography
of Pelargopappus suggest that Eremopezus was not especially close to the Secretarybird's lineage. Thus, even if it belongs with the Falconiformes
(or Accipitriformes), it would probably remain in its distinct family.
The same is true if it were placed in the Pelecaniformes. For as it seems, Goliathia andrewsi, an ancestral shoebill that was slightly larger and presumably far less apomorphic than the living species, lived at about the same time and in the same region as E. eocaenus. It is only known from a single ulna
, which proves however that it was far less in bulk than Eremopezus and certainly able to fly well.
But all things considered, very little can be said about the affiliations of Eremopezus. As ratites are nowadays presumed to have evolved from flying paleognaths similar to tinamou
s after the Cretaceous
—see also Palaeotis
—the Egyptian fossil may be a distinct lineage of ratites after all, and is sometimes allied with the Paleocene
Remiornis from France
. And indeed, as noted by the first scientists that studied it, its known bones—in particular the distal tarsometatarsus—are more similar to those of ratites in general shape and in some details than to other birds. The details (such as lack of the supratendinal bridge) may however be simply plesiomorphies, while the overall resemblance might be the result of convergent evolution
—for the autapomorphies of its toes are starkly unlike those found in any ratite. Thus, it is was a ratite, it probably was the most unusual ratite known to date (while the hardly better-known Remiornis may very well have been a rather conventional proto-ostrich).
As far as can be told however, ratites did never evolve gripping feet like seen in the fossils, and neither did they fare very successfully in wetland habitat as represented in the Jebel Qatrani Formation
. The latter holds true for Galliformes
, which are ancient neognaths of the fowl clade
(Galloanserae). Anseriformes
, the other living member of this group, include the typical waterfowl
such as duck
s, and many of them independently evolved flexible toes, giving them the ability to perch
despite having only a vestigial hallux (see also Cairinini). The Anseriformes also contain the gigantic flightless mihirungs (Dromornithidae) of Australia
(which were, at first, also believed ratites). It is not inconceivable that E. eocaenus was a more aquatic African equivalent of these.
Thus, until more fossils are found, all that can be said is that Eremopezus is unlikely to have been a galliform or a member of the "near passerine
s" group (in the strict sense—perching birds and their immediate allies); these latter orders are generally smallish, live in trees, and probably evolved even later than the birds of prey. But beyond that, it cannot even be ruled out with reasonable certainty that the initial assessment—however lacking by the standards of today's scientific method
—was correct and that E. eocaenus was indeed a highly apomorphic paleognath.
length is not precisely known; if it had the proportions found in elephant bird
s and moa
, it would have been 80–90 cm long. But there is no real reason to assume that Eremopezus, living in wetlands rich in predators, was similar to these bulky lumbering insular
ratites. The tibiotarsus of DPC 20919 preserves most of the bone and is as long as the complete tarsometatarsus
already (34 cm); an overall tibiotarsus length of c.40–50 cm, as found in the small slow-moving elephantbird Mullerornis agilis and the nimble emu
, is a reasonable estimate.
The tarsometatarsus had a small hypotarsus with a single simple crest and devoid of foramina for tendon
s. The ankle joint consists of a sizeable midward and an even larger outward groove. The conspicuous ridge on the backside of the tarsometatarsus is formed by the third toe's midfoot bones, which are set to the plantar side in respect to their neighbors, with which they are fused. This is particularly noticeable in the lower part of the bone, where a corresponding groove is present on the dorsal
side. This smoothens out proximad, with the proximal half of the bone—which is not known from an unflattened specimen to date—probably oval or triangular (with the point backwards) in cross section
.
As regards the length and stoutness of the lower leg and the foot, E. eocaenus would probably have been similar to a good-sized American Rhea
(Rhea americana) in measurements. Its toes, however, differed vastly in shape and posture from those of this ratite (and most other birds). Above the tibiotarsal trochlea
e of the African bird, the bone was considerably wider than the ankle, among ratites being matched by some moa and the Dwarf Cassowary
(Casuarius bennetti). Thus, towards its toes the midfoot bone must have flared outwards, resulting in an overall wide-footed appearance. It is notable that while elephant birds have toes that are only a little more flaring than those of rhea
s, those of fast-running long-legged birds (ratites and others, like seriema
s and some Charadriiformes
) generally tend bunch together in a narrower angle, with the most extreme situation found in the ostrich
. This suggests that wherever Eremopezus did walk, it indeed walked or trotted and ran only in dire need—if it could run quickly at all, which is by no means certain.
It is also notable that the attachment point of the tibiotarsal trochlea
e was flattened in Eremopezus, leaving little room for a bulky pad where the toes joined. In cursorial
birds, this area is typically wide, to provide space for a large cushioning pad where the toes join, which improves balance during walking or running. The structure in E. eocaenus, by contrast, must have allowed a much better toe-flexing ability. The shallow grooves on the trochleae allowed for considerable sideways mobility of the toes; if the single phalanx bone known is assigned correctly to this species (it is the best match in size by far), it is very wide at the proximal end and tapers noticeably distad. The third (middle) toe was the most robust and largest. The inner toe was about as large as the outer one, and attached noticeably more proximal on the tibiotarsus. There is a single foramen
on the dorsal side of the tarsometatarsus, with a plantar exit hole between the third and fourth metacarpal's distal ends (presumably for the outer toe's adductor tendon) and another (presumably for nerve
s and blood vessel
s) on the plantar surface of the tarsometatarsus. The outer sides of the outer trochleae hava a hook at their backward end, which together with deep pits for ligament
s nearby must have served to hold strong tendons. Its hallux
was vestigial, as is typical for birds that move about on foot a lot; it even cannot be ruled out that the hallux was entirely missing (as in ratites).
s, Eremopezus was probably lighter than it, especially if it retained the air-filled bones of flying ancestors. From the ground to the pelvis
, it stood probably as high as a large rhea or small emu—slightly less than one meter in all probability –, though the robust bones of the prehistoric bird appear to have supported a larger bulk than those of the fleet-footed ratites. Altogether, even if it was not particularly long-necked Eremopezus must have stood about as high as an average adult human. It weighed probably less than 50 kg—slightly more than a large emu—and more than 10 kg—slightly more than the largest living storks (which reach over 150 cm in height) and the Shoebill.
The general limit for weight in flying birds is at about 25 kg, the exceptional Argentavis magnificens with its size and weight of a good-sized adult human nonwithstanding as it evolved under unusual ecological conditions. Large males of the Kori Bustard
(Ardeotis kori) and Great Bustard
(Otis tarda) are perfectly capable of flight, while weighing in excess of 20 kg. A wing loading
of c.25 kg/m2 is the known limit for bird flight under normal circumstances; thus, a case could be made for Eremopezus to have been capable of flight. Paleontologists do not consider this likely however, due to the stoutness of the bones, which in such a degree is only known from birds that were certainly flightless. The Secretarybird's tarsometatarsus, for example, is only some 20% shorter but more than 60% slimmer than that of E. eocaenus. Thus, its wing
s and arm
bones were probably reduced, a process known to have taken as little as 10,000 years in some island
rail
s.
s soon lose the barbule hooks that keep them in shape, becoming more hair-like; when flight performance is of no significance anymore, this can improve the insulating
properties of the plumage
. Nothing is known about the plumage color of Eremopezus; it was presumably not very gaudily colored as it had to avoid apex predator
s, but little else can be inferred. Perhaps most likely it had any or all of white, black and grey feathers with at least some eumelanin but little carotenoid
s and phaeomelanins, as usual among the "higher waterbirds" in general, and specifically those that inhabit similar habitat. But as its long as its relationships are unresolved, there is no reason to rule out that it might have been some sort of brown for example. The hair-like plumage of flightless birds does not allow for bright structural colors; birds like the Kākāpō
(Strigops habroptila) and the Takahē
(Porphyrio hochstetteri) show that anything beyond olive drab and dusky blue is physically impossible as soon as the feathers start to lose their structure.
If it was a terrestrial animal, it might have been fairly short-necked; if it inhabited wetlands, its neck was probably not short and quite possibly rather long. The bill
of Eremopezus was of unknown shape, but must in some way have been adapted to its feeding. Even if not a predator, being as it seems a member of the Neoaves its not-too-distant ancestors probably fed on animals. If it fed on terrestrial
prey, it might have had the hooked bill of a bird of prey, but this is very specialized. Among the "higher waterbirds" that variously consume aquatic
and/or terrestrial large invertebrates and small vertebrates, a spear
-like pointed bill seems to have proven most apt for the task. The Pelecaniformes
in particular have a distinct hook or "nail" on the billtip, which is even present in the otherwise plesiomorphic bill of the Hammerkop
(Scopus umbretta). If E. eocaenus was a pelecaniform, it probably also possessed this "nail", but apart from that its bill might just as well have evolved autapomorphies as bizarre as those of the pelican
s.
The Jebel Qatrani Formation
is mainly composed of sandstone
s and mudstone
s, which were laid down as point bar
and overbank
s of meander
ing freshwater
rivers, which drained the northeastern tip of Africa
westwards into a depression
just inland from the Tethys Sea shores, and at least in the wet season must have expanded into large shallow lakes. The entire region was low-lying, and only a few million years (Ma) before Eremopezus inhabited these lands—and when sea level
s were higher—submerged under the ocean. The climate was warmer than today, and the region probably was tropical with abundant rainfall during the monsoon
season, as indicated by the paleosol
s formed from alluvial sediment
s and traces of buttress root
s. Altogether, the habitat
must have resembled the Niger Delta
of our time. The Eremopezus fossils dated with confidence are from a time when there was apparently more forest and less grassland in the region than half a dozen million years later. The reed
grass
es of the subfamily Arundinoideae
were probably far less widespread in Africa 35 million years ago (Ma) than they are today, but it is fairly likely that other Poales
reeds—Cyperaceae
(maybe including the ancestors of the Papyrus Sedge Cyperus papyrus), Juncaceae
and Typhaceae
—grew in aquatic
habitats back then already.
The terrestrial fauna
in the habitat of Eremopezus consisted mainly of the ancestors of animals occurring in Africa today; among mammals particularly Afrotheria
were present. Some entirely extinct lineages were also found, e.g. Anthracotheriidae
and Creodonta
. As regards bird
s, fossils are only plentiful from some Ma later; as mentioned above, they generally represent the Paleogene
avifauna found around the shores of the shrinking Tethys Sea, whose descendants nowadays live in tropical Africa. In quarry L-41, remains of a large ancestral stork
(presumably Palaeoephippiorhynchus dietrichi
) were present, indicating that two or three E. eocaenus (one right and two left feet were found) died in or next to a slow-moving or stagnant watercourse. This agrees with the view that the birds actually lived in such habitat, rather than their carcasses having been transported there by a flood or similar.
E. eocaenus might have been a frugivore
or even herbivore
of swamp forests, but the early Neoaves (to which it probably belonged) are generally predatory. As a predator, it would have fed mainly on mid-sized terrestrial
vertebrate
s—for example large reptile
s or smallish mammal
s. Alternatively—depending on its preferred habitat—it could have eaten mainly aquatic
vertebrates. It cannot be ruled out that it was a filter feeder
like flamingo
s (as of 2008 tentatively considered highly specialized "higher waterbirds") or most Anseriformes
. In any case, it would need to roam a considerable range to find enough food, and thus population density
was likely low. Unmated birds were probably solitary. Mated pairs might have stayed together for life, as they often do in birds.
Large hyaenodontid
creodonts—Akenatenavus cf. leptognathus and possibly Metapterodon—shared the habitat with E. eocaenus, and these pack-hunting carnivore
s, larger than the average dog, could well have included it among their prey. Flightless or at least not quick in taking off, and not well-adapted to running away from threats either, retreating into the swamplands or reed belt would habe provided a means of escape for the large birds. Here too, the highly mobile toes would have proven useful. While near the water, Eremopezus would have had to watch out for the basal crocodile
"Crocodylus" megarhinus
, the aquatic apex predator of Late Eocene Faiyum. On the other hand, the long-snouted gavialid Eogavialis africanum
makes a rather unlikely predator of the giant bird, but feeding on large fish and other mid-sized vertebrates (like the False Gharial
Tomistoma schlegeli of the present time), it would probably have competed with E. eocaenus for food to some extent if the bird indeed was a carnivorous semi-aquatic species.
As only tentative inference
s can be made about the habits of Eremopezus, it is not clear why it became extinct. Still, nothing even remotely resembling a possible descendant is known or inferred, making it rather likely that its lineage did not progress very far. It is sometimes believed that flightless birds cannot compete with carnivorous mammals, but the Phorusrhacidae
prove that even carnivorous flightless birds can very well thrive in the presence of mammalian competitors. However, the rather comprehensive ecological data indicates that habitat in the Faiyum region changed at the start of the Oligocene
: for some time, savanna
dominated by true grass
es (Poaceae) and shrubland
seem to have displaced the swamp forest to a considerable extent, creating a habitat similar to that found at the less humid regions along the lower Sénégal River
. When the forest expanded again, different mammal
s—an abundance of monkey
s but far fewer of the huge Pliohyracidae hyrax
es—inhabited it. In general, the emerging picture is one of an economic upheaval that lasted for perhaps 10 million years, and during which the Paleogene ecosystem at Faiyum with its numeous now-extinct lineages gave way to a more modern one, inhabited by the ancestors of animals that live in tropical Africa today. If Eremopezus was indeed a swamp forest bird, it may well have succumbed to this change. In that respect, it is notable that the "African" fauna found in Europe was replaced by animals originating in Asia
starting at about the same time.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. It is known only from the fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains of a single species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
,
the huge and presumably flightless Eremopezus eocaenus. This was found in Upper Eocene Jebel Qatrani Formation
Jebel Qatrani Formation
The Jebel Qatrani Formation is a palaeontological formation located in Egypt. It dates to the Eocene-Oligocene period....
deposits around the Qasr el-Sagha escarpment
Escarpment
An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
, north of the Birket Qarun lake near Faiyum in Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
. The rocks its fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s occur in were deposited in the Priabonian
Priabonian
The Priabonian is, in the ICS's geologic timescale, the latest age or the upper stage of the Eocene epoch or series. It spans the time between and...
, with the oldest dating back to about 36 million years ago (Ma) and the youngest not less than about 33 Ma.
It is not precisely known from which strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
the first few remains of this bird were collected. They were formerly considered of Early Oligocene age—some 33-30 Ma—but this is now assumed incorrect, as only the upper and not the entire Jebel Qatrani Formation is of Oligocene age. It is also possible that they are from the slightly older Qasr el-Sagha Formation, but as both this and the Oligocene parts of the Jebel Qatrani Formation were laid down in an ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
markedly different from that of the Eocene Jebel Qatrani Formation, it is nowadays assumed that all material of E. eocaenus is from the lowest rocks of the Jebel Qatrani Formation.
Material, taxonomy and systematics
It was originally described from a distal left tibiotarsusTibiotarsus
The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.A similar structure also occurred in the Mesozoic Heterodontosauridae...
piece (specimen BMNH
BMNH
BMNH may refer to:*British Museum of Natural History, commonly known as Natural History Museum, in London, the United Kingdom*Beijing Museum of Natural History, in Beijing, China...
A843); a toe
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...
phalanx bone found soon thereafter was tentatively assigned to this bird. Eremopezus was initially believed a ratite
Ratite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
and loosely allied with the elephant bird
Elephant bird
Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.-Description:...
s of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. Thus, when a piece of tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
shaft was found some time later north of the ruins of Dimeh (Dimê
Dime
Dime may refer to:Currency* Dime * Dime Media and entertainment* Dime , by Guardian* "Dime" , by Beth* The Dimes, a musical group* Dime novel, a type of popular fictionSports* Dime...
; itself a bit north of the Birket Qarun) this was described as Stromeria fajumensis; though it had a size to match the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
tibiotarsus it was thought to resemble an elephantbird even more. The shaft (specimen BSPG 1914 I 53) has a prominent plantar (backside) ridge also found in Mullerornis betsilei, and this was used to ally the fossil bone with this rather small and gracile elephant bird. The Eremopezus specimen on the other hand has deep ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
al pits on the lateral and medial
Medial (disambiguation)
Medial has several meanings:* In mathematics, a medial is a set with a binary operation satisfying certain properties, see medial.* In anatomy, a medial is an adjective describing structures near the midline of an animal, see anatomical terms of location or Human Anatomical Terms#Anatomical...
sides of the distal condyles, which are not found in the elephant birds proper. These pits together with a crisply defined ridge held a sling of ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
, which in turn—in place of the bony
Bony
Bony may refer to:* Adjective related to bone* Bony, a commune of the Aisne département, in France* Bőny, a village in Hungary* A nickname for Napoleon Bonaparte* The Bank of New York...
supratendinal bridge found in some other birds—kept the ankle
Ankle
The ankle joint is formed where the foot and the leg meet. The ankle, or talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot...
tendons from dislocating. The tarsometatarsus is also more similar to that of an unspecific ratite, such as an emu
Emu
The Emu Dromaius novaehollandiae) is the largest bird native to Australia and the only extant member of the genus Dromaius. It is the second-largest extant bird in the world by height, after its ratite relative, the ostrich. There are three subspecies of Emus in Australia...
, ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
or rhea
Rhea (bird)
The rheas are ratites in the genus Rhea, native to South America. There are two existing species: the Greater or American Rhea and the Lesser or Darwin's Rhea. The genus name was given in 1752 by Paul Möhring and adopted as the English common name. Möhring's reason for choosing this name, from the...
, rather than to the apomorphic one of the elephantbirds.
Almost 100 years after the discovery of the holotype, more Eremopezus fossils were unearthed from the famous quarry
Quarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
L-41 at Tel Akgrab near 29°36′20"N 30°30′00"E. These are also all leg
Leg
Łęg may refer to the following places in Poland:*A former name for the town of Ełk *Part of the Czyżyny district of Kraków*Łęg, Pleszew County in Greater Poland Voivodeship...
and foot
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
bones, namely specimens DPC 20919 (a distal right tibiotarsus and its entire tarsometatarsus), DPC 5555 (the lower half of a left tarsometatarsus) and DPC 18309 (the distal end of a left tarsometatarsus).
Some fossil eggshell
Eggshell
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats.- Insect eggs :Insects and other arthropods lay a variety of styles and shapes of eggs. Some have gelatinous or skin-like coverings, others have hard eggshells. Softer shells are mostly protein....
s from the Maghreb
Maghreb
The Maghreb is the region of Northwest Africa, west of Egypt. It includes five countries: Morocco, Algeria, Tunisia, Libya, and Mauritania and the disputed territory of Western Sahara...
, described as Psammornis and resembling those of ratite eggs, were assigned to Eremopezus by various authors. They were at first believed to date form the Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
also, but today are generally considered far younger (of late Neogene
Neogene
The Neogene is a geologic period and system in the International Commission on Stratigraphy Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago...
age, probably less than 5 Ma) and indeed to have been laid by ostriches or close relatives thereof.
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
term signifying a lonely or solitary place or person: a hermit
Hermit
A hermit is a person who lives, to some degree, in seclusion from society.In Christianity, the term was originally applied to a Christian who lives the eremitic life out of a religious conviction, namely the Desert Theology of the Old Testament .In the...
, a desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
or a wasteland. Yet while Faiyum is located at the edge of the Libyan Desert
Libyan Desert
The Libyan Desert covers an area of approximately 1,100,000 km2, it extends approximately 1100 km from east to west, and 1,000 km from north to south, in about the shape of a rectangle...
, it is a well-vegetated location even today; some 35-30 MA it was a lush region and teemed with life. On the other hand, is it not at all likely that such a large and quite likely predatory bird like E. eocaenus was in any way gregarious or occurred at high population densities. It might therefore be described as a "hermit" with some justification, but certainly not as a "desert-dweller". pezus is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
ized Greek from pezós (πεζός), "someone who walks". eocaenus refers to the bird's age; as noted, the initial 1904 assessment of C. W. Andrews was indeed correct. Stromeria fajumensis was named in honor of the paleontologist Ernst Stromer von Reichenbach, and the bone's place of discovery.
Systematics
Careful study of the remains suggests that their apparent similarity to ratites is misleading. They actually combine a number of traits not found in any known ratite lineage, and in particularly not in the ostrichOstrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
es and elephant bird
Elephant bird
Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.-Description:...
s (the only ratites biogeographically close to Eremopezus). Moreover, the prehistoric bird had several peculiar traits not at all found in ratites, but present in certain neognaths: its toes were widely divergent and could flex through a wide range of positions, while strong tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
s gave the bird a firm grip. In the associated anatomical details, E. eocaenus resembled the Secretarybird (Sagittarius serpentarius) and the Shoebill
Shoebill
The Shoebill also known as Whalehead or Shoe-billed Stork, is a very large stork-like bird. It derives its name from its massive shoe-shaped bill. The adult bird is tall, long, across the wingspan and weighs . Their beaks have an average length of length of . The adult is mainly grey while the...
(Balaeniceps rex), two rather singular Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n endemics.
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
that can fly well, but prefers to walk around on its long legs, especially when foraging. It uses its flexible toes to grab prey—large arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s and small to mid-sized terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
. It throws the prey around and kicks it forcefully, smashing it to death or breaking its spine
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
. The Shoebill, meanwhile, for lack of a better theory was long considered a large aberrant stork
Stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family Ciconiidae. They are the only family in the biological order Ciconiiformes, which was once much larger and held a number of families....
relative in the Ciconiiformes
Ciconiiformes
Traditionally, the order Ciconiiformes has included a variety of large, long-legged wading birds with large bills: storks, herons, egrets, ibises, spoonbills, and several others. Ciconiiformes are known from the Late Eocene...
. This eventually proved incorrect. While B. rex is indeed a member of the same group of "higher waterbirds" as are storks and heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
s, it is closely related to pelican
Pelican
A pelican, derived from the Greek word πελεκυς pelekys is a large water bird with a large throat pouch, belonging to the bird family Pelecanidae....
s and thus came to be included in the Pelecaniformes
Pelecaniformes
The Pelecaniformes is a order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such names as totipalmates or steganopodes...
—which are not monophyletic as described in old times, however, and whose small core group, for simplicity, is included in the Ciconiiformes by some recent authors. Insofar, the Shoebill is today recognized as the formerly missing link
Missing Link
Missing link is a nonscientific term for any transitional fossil, especially one connected with human evolution; see Transitional fossil - Missing links and List of transitonal fossils - Human evolution.Missing Link may refer to:...
uniting pelicans and storks. Like the pelicans, it uses its massive bill and throat sac to catch large fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and similar aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
vertebrates, but unlike them it is a wading, not a swimming bird, and correspondingly has long legs like a stork. It clambers through reedbeds in search of good fishing spots, and uses its flexible toes to firmly hold on to such uncertain substrate
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
as heaps of wind-blown vegetation at the edge of the open water or roots and logs of tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s.
But this does not mean that Eremopezus was a close relative of either Secretarybird or Shoebill. Even though modern taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
generally tries to avoid using monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
families as much as possible, its placement in a distinct family Eremopezidae may well be warranted, as its closest relatives remain completely obscure.
For the birds of prey, a Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
(perhaps even Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
) origin seems most likely; the first fossils of the present-day lineages (and some entirely extinct forms) are abundant in Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
strata of the Holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
, particularly Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. The falcon
Falcon
A falcon is any species of raptor in the genus Falco. The genus contains 37 species, widely distributed throughout Europe, Asia, and North America....
s seem to have rapidly spread throughout the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, where the plesiomorphic caracara
Caracara
Caracaras are birds of prey in the family Falconidae. They are traditionally placed in the subfamily Polyborinae, but are sometimes considered part of their own subfamily, Caracarinae, or members of the true falcon subfamily, Falconinae...
s are found. The other diurnal raptors, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Accipitridae
Accipitridae
The Accipitridae, one of the two major families within the order Accipitriformes , are a family of small to large birds with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a...
—by some considered more distinct, as core group of an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Accipitriformes –, apparently diversified eastwards into Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and eventually into Africa.
As regards the Secretarybird, the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Pelargopappus occurred at about the same time as E. eocaenus in today's France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, separated from the site of Faiyum by more than 1,500 km of the shrinking Tethys Sea. The Maghreb
Maghreb
The Maghreb is the region of Northwest Africa, west of Egypt. It includes five countries: Morocco, Algeria, Tunisia, Libya, and Mauritania and the disputed territory of Western Sahara...
was closer to Europe however, not more than today's Mediterranean where it is widest, and numerous bird lineages are known to have occurred in Africa as well as in Europe during the Eocene. Pelargopappus seems to be an ancient secretarybird, not an ancestor of the living species but not far removed from the last common ancestor either. Its remains, and how they differ from secretarybirds, give an idea how the Sagittariidae of that time looked like. So even though Pelargopappus has not yet been directly compared to the African fossil in a cladistic analysis, the pronounced differences between Eremopezus and Sagittarius and the biogeography
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
of Pelargopappus suggest that Eremopezus was not especially close to the Secretarybird's lineage. Thus, even if it belongs with the Falconiformes
Falconiformes
The order Falconiformes is a group of about 290 species of birds that comprises the diurnal birds of prey. Raptor classification is difficult and the order is treated in several ways.- Classification problems :...
(or Accipitriformes), it would probably remain in its distinct family.
The same is true if it were placed in the Pelecaniformes. For as it seems, Goliathia andrewsi, an ancestral shoebill that was slightly larger and presumably far less apomorphic than the living species, lived at about the same time and in the same region as E. eocaenus. It is only known from a single ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
, which proves however that it was far less in bulk than Eremopezus and certainly able to fly well.
But all things considered, very little can be said about the affiliations of Eremopezus. As ratites are nowadays presumed to have evolved from flying paleognaths similar to tinamou
Tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....
s after the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
—see also Palaeotis
Palaeotis
Palaeotis is a genus of paleognath bird from the middle Eocene epoch of central Europe. One species is known, Paleotis weigelti. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect described it as an extinct bustard , and gave it its consequent name . After a suggestion by...
—the Egyptian fossil may be a distinct lineage of ratites after all, and is sometimes allied with the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
Remiornis from France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. And indeed, as noted by the first scientists that studied it, its known bones—in particular the distal tarsometatarsus—are more similar to those of ratites in general shape and in some details than to other birds. The details (such as lack of the supratendinal bridge) may however be simply plesiomorphies, while the overall resemblance might be the result of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
—for the autapomorphies of its toes are starkly unlike those found in any ratite. Thus, it is was a ratite, it probably was the most unusual ratite known to date (while the hardly better-known Remiornis may very well have been a rather conventional proto-ostrich).
As far as can be told however, ratites did never evolve gripping feet like seen in the fossils, and neither did they fare very successfully in wetland habitat as represented in the Jebel Qatrani Formation
Jebel Qatrani Formation
The Jebel Qatrani Formation is a palaeontological formation located in Egypt. It dates to the Eocene-Oligocene period....
. The latter holds true for Galliformes
Galliformes
Galliformes are an order of heavy-bodied ground-feeding domestic or game bird, containing turkey, grouse, chicken, New and Old World Quail, ptarmigan, partridge, pheasant, and the Cracidae. Common names are gamefowl or gamebirds, landfowl, gallinaceous birds or galliforms...
, which are ancient neognaths of the fowl clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
(Galloanserae). Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
, the other living member of this group, include the typical waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
such as duck
Duck
Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...
s, and many of them independently evolved flexible toes, giving them the ability to perch
Perch
Perch is a common name for fish of the genus Perca, freshwater gamefish belonging to the family Percidae. The perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning spotted, and the...
despite having only a vestigial hallux (see also Cairinini). The Anseriformes also contain the gigantic flightless mihirungs (Dromornithidae) of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
(which were, at first, also believed ratites). It is not inconceivable that E. eocaenus was a more aquatic African equivalent of these.
Thus, until more fossils are found, all that can be said is that Eremopezus is unlikely to have been a galliform or a member of the "near passerine
Near passerine
Near passerine or higher land-bird assemblage are terms often given to arboreal birds or those most often believed to be related to the true passerines due to ecological similarities; the group corresponds to some extent with the Anomalogonatae of Garrod All near passerines are land birds...
s" group (in the strict sense—perching birds and their immediate allies); these latter orders are generally smallish, live in trees, and probably evolved even later than the birds of prey. But beyond that, it cannot even be ruled out with reasonable certainty that the initial assessment—however lacking by the standards of today's scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
—was correct and that E. eocaenus was indeed a highly apomorphic paleognath.
Description
While the rest of the bird can only be tentatively inferred, the "legs" (the lower leg to midfoot actually) of this gigantic bird are rather well-known today and their details yield some rather robust information on the habits of E. eocaenus.Feet
Its tibiotarsusTibiotarsus
The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.A similar structure also occurred in the Mesozoic Heterodontosauridae...
length is not precisely known; if it had the proportions found in elephant bird
Elephant bird
Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.-Description:...
s and moa
Moa
The moa were eleven species of flightless birds endemic to New Zealand. The two largest species, Dinornis robustus and Dinornis novaezelandiae, reached about in height with neck outstretched, and weighed about ....
, it would have been 80–90 cm long. But there is no real reason to assume that Eremopezus, living in wetlands rich in predators, was similar to these bulky lumbering insular
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
ratites. The tibiotarsus of DPC 20919 preserves most of the bone and is as long as the complete tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
already (34 cm); an overall tibiotarsus length of c.40–50 cm, as found in the small slow-moving elephantbird Mullerornis agilis and the nimble emu
Emu
The Emu Dromaius novaehollandiae) is the largest bird native to Australia and the only extant member of the genus Dromaius. It is the second-largest extant bird in the world by height, after its ratite relative, the ostrich. There are three subspecies of Emus in Australia...
, is a reasonable estimate.
The tarsometatarsus had a small hypotarsus with a single simple crest and devoid of foramina for tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
s. The ankle joint consists of a sizeable midward and an even larger outward groove. The conspicuous ridge on the backside of the tarsometatarsus is formed by the third toe's midfoot bones, which are set to the plantar side in respect to their neighbors, with which they are fused. This is particularly noticeable in the lower part of the bone, where a corresponding groove is present on the dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
side. This smoothens out proximad, with the proximal half of the bone—which is not known from an unflattened specimen to date—probably oval or triangular (with the point backwards) in cross section
Cross section (geometry)
In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc...
.
American Rhea
The Greater Rhea, Rhea americana, is a flightless bird found in eastern South America. Other names for the Greater Rhea include the Grey, Common, American Rhea, ñandú or ema . One of two species in the genus Rhea, in the family Rheidae, the Greater Rhea is endemic to Argentina, Bolivia, Brazil,...
(Rhea americana) in measurements. Its toes, however, differed vastly in shape and posture from those of this ratite (and most other birds). Above the tibiotarsal trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
e of the African bird, the bone was considerably wider than the ankle, among ratites being matched by some moa and the Dwarf Cassowary
Dwarf Cassowary
The Dwarf Cassowary, Casuarius bennetti, also known as the Bennett's Cassowary, Little Cassowary, Mountain Cassowary, or Mooruk, is the smallest of the three species of cassowaries.-Taxonomy:...
(Casuarius bennetti). Thus, towards its toes the midfoot bone must have flared outwards, resulting in an overall wide-footed appearance. It is notable that while elephant birds have toes that are only a little more flaring than those of rhea
Rhea (bird)
The rheas are ratites in the genus Rhea, native to South America. There are two existing species: the Greater or American Rhea and the Lesser or Darwin's Rhea. The genus name was given in 1752 by Paul Möhring and adopted as the English common name. Möhring's reason for choosing this name, from the...
s, those of fast-running long-legged birds (ratites and others, like seriema
Seriema
The seriemas are the sole extant members of the small and ancient family Cariamidae, which is also the sole surviving family of the Cariamae. Once believed to be related to cranes, they have been placed by one recent study near the falcons, parrots and passerines, as well as the extinct terror birds...
s and some Charadriiformes
Charadriiformes
Charadriiformes is a diverse order of small to medium-large birds. It includes about 350 species and has members in all parts of the world. Most Charadriiformes live near water and eat invertebrates or other small animals; however, some are pelagic , some occupy deserts and a few are found in thick...
) generally tend bunch together in a narrower angle, with the most extreme situation found in the ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
. This suggests that wherever Eremopezus did walk, it indeed walked or trotted and ran only in dire need—if it could run quickly at all, which is by no means certain.
It is also notable that the attachment point of the tibiotarsal trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
e was flattened in Eremopezus, leaving little room for a bulky pad where the toes joined. In cursorial
Cursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
birds, this area is typically wide, to provide space for a large cushioning pad where the toes join, which improves balance during walking or running. The structure in E. eocaenus, by contrast, must have allowed a much better toe-flexing ability. The shallow grooves on the trochleae allowed for considerable sideways mobility of the toes; if the single phalanx bone known is assigned correctly to this species (it is the best match in size by far), it is very wide at the proximal end and tapers noticeably distad. The third (middle) toe was the most robust and largest. The inner toe was about as large as the outer one, and attached noticeably more proximal on the tibiotarsus. There is a single foramen
Foramen
In anatomy, a foramen is any opening. Foramina inside the body of humans and other animals typically allow muscles, nerves, arteries, veins, or other structures to connect one part of the body with another.-Skull:...
on the dorsal side of the tarsometatarsus, with a plantar exit hole between the third and fourth metacarpal's distal ends (presumably for the outer toe's adductor tendon) and another (presumably for nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s and blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s) on the plantar surface of the tarsometatarsus. The outer sides of the outer trochleae hava a hook at their backward end, which together with deep pits for ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
s nearby must have served to hold strong tendons. Its hallux
Hallux
In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals...
was vestigial, as is typical for birds that move about on foot a lot; it even cannot be ruled out that the hallux was entirely missing (as in ratites).
Size and flightlessness
E. eocaenus was somewhat ponderous, at about the body size of Mullerornis betsilei. As this was one of the heavy-boned elephant birdElephant bird
Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.-Description:...
s, Eremopezus was probably lighter than it, especially if it retained the air-filled bones of flying ancestors. From the ground to the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
, it stood probably as high as a large rhea or small emu—slightly less than one meter in all probability –, though the robust bones of the prehistoric bird appear to have supported a larger bulk than those of the fleet-footed ratites. Altogether, even if it was not particularly long-necked Eremopezus must have stood about as high as an average adult human. It weighed probably less than 50 kg—slightly more than a large emu—and more than 10 kg—slightly more than the largest living storks (which reach over 150 cm in height) and the Shoebill.
Kori Bustard
The Kori Bustard is a large bird native to Africa. It is a member of the bustard family. It may be the heaviest bird capable of flight....
(Ardeotis kori) and Great Bustard
Great Bustard
The Great Bustard is in the bustard family, the only member of the genus Otis. It breeds in southern and central Europe, where it is the largest species of bird, and across temperate Asia...
(Otis tarda) are perfectly capable of flight, while weighing in excess of 20 kg. A wing loading
Wing loading
In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. The faster an aircraft flies, the more lift is produced by each unit area of wing, so a smaller wing can carry the same weight in level flight, operating at a higher wing loading. Correspondingly,...
of c.25 kg/m2 is the known limit for bird flight under normal circumstances; thus, a case could be made for Eremopezus to have been capable of flight. Paleontologists do not consider this likely however, due to the stoutness of the bones, which in such a degree is only known from birds that were certainly flightless. The Secretarybird's tarsometatarsus, for example, is only some 20% shorter but more than 60% slimmer than that of E. eocaenus. Thus, its wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
s and arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...
bones were probably reduced, a process known to have taken as little as 10,000 years in some island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
rail
Rallidae
The rails, or Rallidae, are a large cosmopolitan family of small to medium-sized birds. The family exhibits considerable diversity and the family also includes the crakes, coots, and gallinules...
s.
Plumage and beak
As birds become flightless, their featherFeather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s soon lose the barbule hooks that keep them in shape, becoming more hair-like; when flight performance is of no significance anymore, this can improve the insulating
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...
properties of the plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
. Nothing is known about the plumage color of Eremopezus; it was presumably not very gaudily colored as it had to avoid apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...
s, but little else can be inferred. Perhaps most likely it had any or all of white, black and grey feathers with at least some eumelanin but little carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
s and phaeomelanins, as usual among the "higher waterbirds" in general, and specifically those that inhabit similar habitat. But as its long as its relationships are unresolved, there is no reason to rule out that it might have been some sort of brown for example. The hair-like plumage of flightless birds does not allow for bright structural colors; birds like the Kākāpō
Kakapo
The Kakapo , Strigops habroptila , also called owl parrot, is a species of large, flightless nocturnal parrot endemic to New Zealand...
(Strigops habroptila) and the Takahē
Takahe
The Takahē or South Island Takahē, Porphyrio hochstetteri is a flightless bird indigenous to New Zealand and belonging to the rail family. It was thought to be extinct after the last four known specimens were taken in 1898...
(Porphyrio hochstetteri) show that anything beyond olive drab and dusky blue is physically impossible as soon as the feathers start to lose their structure.
If it was a terrestrial animal, it might have been fairly short-necked; if it inhabited wetlands, its neck was probably not short and quite possibly rather long. The bill
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
of Eremopezus was of unknown shape, but must in some way have been adapted to its feeding. Even if not a predator, being as it seems a member of the Neoaves its not-too-distant ancestors probably fed on animals. If it fed on terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
prey, it might have had the hooked bill of a bird of prey, but this is very specialized. Among the "higher waterbirds" that variously consume aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
and/or terrestrial large invertebrates and small vertebrates, a spear
Spear
A spear is a pole weapon consisting of a shaft, usually of wood, with a pointed head.The head may be simply the sharpened end of the shaft itself, as is the case with bamboo spears, or it may be made of a more durable material fastened to the shaft, such as flint, obsidian, iron, steel or...
-like pointed bill seems to have proven most apt for the task. The Pelecaniformes
Pelecaniformes
The Pelecaniformes is a order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such names as totipalmates or steganopodes...
in particular have a distinct hook or "nail" on the billtip, which is even present in the otherwise plesiomorphic bill of the Hammerkop
Hammerkop
The Hamerkop , also known as Hammerkop,Hammerkopf, Hammerhead, Hammerhead Stork, Umbrette, Umber Bird, Tufted Umber, or Anvilhead, is a medium-sized wading bird...
(Scopus umbretta). If E. eocaenus was a pelecaniform, it probably also possessed this "nail", but apart from that its bill might just as well have evolved autapomorphies as bizarre as those of the pelican
Pelican
A pelican, derived from the Greek word πελεκυς pelekys is a large water bird with a large throat pouch, belonging to the bird family Pelecanidae....
s.
Ecology
Jebel Qatrani Formation
The Jebel Qatrani Formation is a palaeontological formation located in Egypt. It dates to the Eocene-Oligocene period....
is mainly composed of sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s and mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s, which were laid down as point bar
Point bar
A point bar is a depositional feature of streams. Point bars are found in abundance in mature or meandering streams. They are crescent-shaped and located on the inside of a stream bend, being very similar to, though often smaller than towheads, or river islands.Point bars are composed of sediment...
and overbank
Overbank
The term overbank describes the type of alluvial geological deposit or sediment that is deposited on the flood plain of a river. Because it occurs outside the main channel, away from faster flow, the deposit tends to be fine-grained....
s of meander
Meander
A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the...
ing freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
rivers, which drained the northeastern tip of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
westwards into a depression
Depression (geology)
A depression in geology is a landform sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms.Structural or tectonic related:...
just inland from the Tethys Sea shores, and at least in the wet season must have expanded into large shallow lakes. The entire region was low-lying, and only a few million years (Ma) before Eremopezus inhabited these lands—and when sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
s were higher—submerged under the ocean. The climate was warmer than today, and the region probably was tropical with abundant rainfall during the monsoon
Monsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
season, as indicated by the paleosol
Paleosol
In the geosciences, paleosol can have two meanings. The first meaning, common in geology and paleontology, refers to a former soil preserved by burial underneath either sediments or volcanic deposits , which in the case of older deposits have lithified into rock...
s formed from alluvial sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s and traces of buttress root
Buttress root
Buttress are large roots on all sides of a big bottomed tree or shallowly rooted tree. Typically, they are found in nutrient-poor rainforest soils and do not penetrate to deeper layers. They prevent the tree from falling over while also gathering more nutrients...
s. Altogether, the habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
must have resembled the Niger Delta
Niger Delta
The Niger Delta, the delta of the Niger River in Nigeria, is a densely populated region sometimes called the Oil Rivers because it was once a major producer of palm oil...
of our time. The Eremopezus fossils dated with confidence are from a time when there was apparently more forest and less grassland in the region than half a dozen million years later. The reed
Reed bed
Reed beds are natural habitats found in floodplains, waterlogged depressions andestuaries. Reed beds are part of a succession from young reed colonising open water or wet ground through a gradation of increasingly dry ground...
grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es of the subfamily Arundinoideae
Arundinoideae
The Arundinoideae is a subfamily of the true grass family Poaceae, including giant reed and common reed.-Genera:Tribe AmphipogoneaeAmphipogonDiplopogonTribe AristideaeAristidaSartidiaStipagrostiTribe ArundineaeArundo...
were probably far less widespread in Africa 35 million years ago (Ma) than they are today, but it is fairly likely that other Poales
Poales
Poales is a large order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges. Sixteen plant families are currently recognized by botanists to be part of Poales....
reeds—Cyperaceae
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
(maybe including the ancestors of the Papyrus Sedge Cyperus papyrus), Juncaceae
Juncaceae
Juncaceae, the rush family, are a monocotyledonous family of flowering plants. There are eight genera and about 400 species. Members of the Juncaceae are slow-growing, rhizomatous, herbaceous plants, and they may superficially resemble grasses. They often grow on infertile soils in a wide range...
and Typhaceae
Typhaceae
Typhaceae is the botanical name for a family of flowering plants. Such a family has been recognized by most taxonomists.The APG II system, of 2003 , also recognizes this family, and assigns it to the order Poales in the clade commelinids, in the monocots...
—grew in aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
habitats back then already.
The terrestrial fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
in the habitat of Eremopezus consisted mainly of the ancestors of animals occurring in Africa today; among mammals particularly Afrotheria
Afrotheria
Afrotheria is a clade of mammals, the living members of which belong to groups from Africa or of African origin: golden moles, sengis , tenrecs, aardvarks, hyraxes, elephants and sea cows. The common ancestry of these animals was not recognized until the late 1990s...
were present. Some entirely extinct lineages were also found, e.g. Anthracotheriidae
Anthracotheriidae
Anthracotheriidae is a family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, Elomeryx, first appeared during the Middle Eocene in Asia...
and Creodonta
Creodonta
The creodonts are an extinct order of mammals that lived from the Paleocene to the Miocene epochs. They shared a common ancestor with the Carnivora....
. As regards bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, fossils are only plentiful from some Ma later; as mentioned above, they generally represent the Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
avifauna found around the shores of the shrinking Tethys Sea, whose descendants nowadays live in tropical Africa. In quarry L-41, remains of a large ancestral stork
Stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family Ciconiidae. They are the only family in the biological order Ciconiiformes, which was once much larger and held a number of families....
(presumably Palaeoephippiorhynchus dietrichi
Palaeoephippiorhynchus
Palaeoephippiorhynchus is an extinct genus of large stork from the Oligocene and Miocene. There are two recorded species, P. dietrichi from early Oligocene of Egypt and P. edwardsi from Miocene of Libya.-References:...
) were present, indicating that two or three E. eocaenus (one right and two left feet were found) died in or next to a slow-moving or stagnant watercourse. This agrees with the view that the birds actually lived in such habitat, rather than their carcasses having been transported there by a flood or similar.
E. eocaenus might have been a frugivore
Frugivore
A frugivore is a fruit eater. It can be any type of herbivore or omnivore where fruit is a preferred food type. Because approximately 20% of all mammalian herbivores also eat fruit, frugivory is considered to be common among mammals. Since frugivores eat a lot of fruit they are highly dependent...
or even herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
of swamp forests, but the early Neoaves (to which it probably belonged) are generally predatory. As a predator, it would have fed mainly on mid-sized terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s—for example large reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s or smallish mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s. Alternatively—depending on its preferred habitat—it could have eaten mainly aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
vertebrates. It cannot be ruled out that it was a filter feeder
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
like flamingo
Flamingo
Flamingos or flamingoes are gregarious wading birds in the genus Phoenicopterus , the only genus in the family Phoenicopteridae...
s (as of 2008 tentatively considered highly specialized "higher waterbirds") or most Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
. In any case, it would need to roam a considerable range to find enough food, and thus population density
Population density
Population density is a measurement of population per unit area or unit volume. It is frequently applied to living organisms, and particularly to humans...
was likely low. Unmated birds were probably solitary. Mated pairs might have stayed together for life, as they often do in birds.
Hyaenodontidae
Hyaenodontidae is a family of the extinct order Creodonta, which contains several dozen genera.The Hyaenodontids were important mammalian predators that arose during the late Paleocene and persisted well into the Miocene...
creodonts—Akenatenavus cf. leptognathus and possibly Metapterodon—shared the habitat with E. eocaenus, and these pack-hunting carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s, larger than the average dog, could well have included it among their prey. Flightless or at least not quick in taking off, and not well-adapted to running away from threats either, retreating into the swamplands or reed belt would habe provided a means of escape for the large birds. Here too, the highly mobile toes would have proven useful. While near the water, Eremopezus would have had to watch out for the basal crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
"Crocodylus" megarhinus
Crocodylus megarhinus
"Crocodylus" megarhinus is an extinct species of crocodile from the Eocene of Egypt. A partial skull was found by British paleontologist Charles William Andrews in the Fayum Depression. Andrews named Crocodylus megarhinus in 1905 on the basis of the holotype skull...
, the aquatic apex predator of Late Eocene Faiyum. On the other hand, the long-snouted gavialid Eogavialis africanum
Eogavialis
Eogavialis is an extinct gavialoid. It superficially resembles Tomistoma schlegelii, the extant false gharial, and consequently material from the genus was originally referred to Tomistoma...
makes a rather unlikely predator of the giant bird, but feeding on large fish and other mid-sized vertebrates (like the False Gharial
False gharial
The false gharial , also known as the Malayan gharial, false gavial, or Tomistoma is a freshwater crocodile of the Crocodylidae family with a very thin and elongated snout...
Tomistoma schlegeli of the present time), it would probably have competed with E. eocaenus for food to some extent if the bird indeed was a carnivorous semi-aquatic species.
As only tentative inference
Inference
Inference is the act or process of deriving logical conclusions from premises known or assumed to be true. The conclusion drawn is also called an idiomatic. The laws of valid inference are studied in the field of logic.Human inference Inference is the act or process of deriving logical conclusions...
s can be made about the habits of Eremopezus, it is not clear why it became extinct. Still, nothing even remotely resembling a possible descendant is known or inferred, making it rather likely that its lineage did not progress very far. It is sometimes believed that flightless birds cannot compete with carnivorous mammals, but the Phorusrhacidae
Phorusrhacidae
Phorusrhacids , colloquially known as "terror birds" as the larger species were apex predators during the Miocene, were a clade of large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2 million years ago. They were roughly 1–3 meters tall...
prove that even carnivorous flightless birds can very well thrive in the presence of mammalian competitors. However, the rather comprehensive ecological data indicates that habitat in the Faiyum region changed at the start of the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
: for some time, savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
dominated by true grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es (Poaceae) and shrubland
Shrubland
Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...
seem to have displaced the swamp forest to a considerable extent, creating a habitat similar to that found at the less humid regions along the lower Sénégal River
Sénégal River
The Sénégal River is a long river in West Africa that forms the border between Senegal and Mauritania.The Sénégal's headwaters are the Semefé and Bafing rivers which both originate in Guinea; they form a small part of the Guinean-Malian border before coming together at Bafoulabé in Mali...
. When the forest expanded again, different mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s—an abundance of monkey
Monkey
A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...
s but far fewer of the huge Pliohyracidae hyrax
Hyrax
A hyrax is any of four species of fairly small, thickset, herbivorous mammals in the order Hyracoidea. The rock hyrax Procavia capensis, the yellow-spotted rock hyrax Heterohyrax brucei, the western tree hyrax Dendrohyrax dorsalis, and the southern tree hyrax, Dendrohyrax arboreus live in Africa...
es—inhabited it. In general, the emerging picture is one of an economic upheaval that lasted for perhaps 10 million years, and during which the Paleogene ecosystem at Faiyum with its numeous now-extinct lineages gave way to a more modern one, inhabited by the ancestors of animals that live in tropical Africa today. If Eremopezus was indeed a swamp forest bird, it may well have succumbed to this change. In that respect, it is notable that the "African" fauna found in Europe was replaced by animals originating in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
starting at about the same time.
See also
- Flexiraptor, Australian prehistoric bird of prey with a gripping foot