Saadanius
Encyclopedia
Saadanius is a genus
of fossil primate
dating to the Oligocene
that is closely related to the common ancestor
of the Old World monkey
s and ape
s, collectively known as catarrhines
. It is represented by a single species, Saadanius hijazensis, which is known only from a single partial skull tentatively dated between 29 and 28 mya (million years ago). It was discovered in 2009 in western Saudi Arabia
near Mecca
and was first described in 2010 after a comparison with both living and fossil catarrhines.
Saadanius had a longer face than living catarrhines and lacked the advanced frontal sinus
(airspaces in the facial bones) found in living catarrhines. However, it had a bony ear tube (ectotympanic
) and teeth comparable to those of living catarrhines. The discovery of Saadanius may help answer questions about the appearance of the last common ancestors of Old World monkeys and apes and help date the evolutionary split between these two primate groups.
, named "SGS-UM 2009-002", stored in Jeddah
, Saudi Arabia, at the Paleontology Unit of the Saudi Geological Survey
(SGS). Its type locality, or the place it was discovered, was on top of an oolitic
ironstone
fossil bed of the middle Shumaysi Formation located in the southwest corner of Harrat Al Ujayfa, in western Saudi Arabia, close to Mecca. The specimen was discovered in February 2009 by paleontologist Iyad Zalmout, who had traveled to the region to search for ancient whale
and dinosaur
fossils. While looking for dinosaur fossils in an area that, according to the maps he was working from, contained rock layers that dated to the Cretaceous
(145–65 mya), Zalmout found the jawbone of a hippo-like creature, called an anthracotheriid
(a close relative of whales and hippos), which dated to Eocene
or Oligocene. This indicated that the rock layers were much younger than what was dated on the maps. The following day, he noticed fossil teeth, which he immediately recognized as those of a primate. Zalmout emailed a photo of the teeth to paleontologist Philip D. Gingerich
, with whom he was working as a postdoctoral fellow. Gingerich, an expert on ancient primates and whales, confirmed that it was indeed a primate. Due to a tight schedule, Zalmout had to leave the exposed fossil embedded in the rock for the next few days because collecting it would require days of work. The fossil was soon recovered by a joint expedition involving the SGS and the University of Michigan
.
The fossil was not formally described until 2010 when its discovery was announced in the journal Nature
. The fossil was dated to about 28 or 29 million years ago based on comparisons of fossils of anthracotheriids and paenungulates
(members of the group that includes elephants and hyraxes) found nearby with fossils from similarly aged African deposits. However, the date has yet to be confirmed by other dating techniques. The genus
name, Saadanius, comes from the Arabic word, saadan , which is the collective term for apes and monkeys. The species name, hijazensis, is a reference to the al Hijaz
region, in which it was discovered.
s in appearance, although it was larger—possibly the size of a gibbon
. Its enlarged, deep-rooted canine teeth
, the diastema
(space) between its canine teeth and second incisor
s, and its sagittal crest
(ridge of bone running lengthwise down the top of the skull) suggest that the specimen was a male. These features are shared among male Old World monkeys. Saadanius lacks the advanced frontal sinus
found in living catarrhines, but it does possess an ectotympanic
, or bony ear tube, found in living catarrhines. Propliopithecoids, the oldest stem group of catarrhines, which date back 35 to 30 mya, lacked a fully developed ectotympanic.
The specimen had serious puncture wounds on the front of the skull, indicating that it had been preyed upon by a large carnivore
. One puncture wound was on the right side of the braincase and may have been the fatal blow. There was also a bite mark on the frontal trigon.
Like other catarrhine primates, Saadanius was probably a tree-dweller (arboreal
). During the time it would have lived, the Red Sea
had not yet formed, and new plant and animal species would have been arriving from nearby Eurasia
as it converged with the Afro-Arabian landmass.
and cladistic analysis
indicate that Saadanius is more closely related to the last common ancestor of crown
catarrhines than any other known fossil catarrhines, placing the common ancestry of Catarrhini in Arabia and Africa. Other stem catarrhines include propliopithecoids, such as Aegyptopithecus
, and pliopithecoids, such as Pliopithecus
. The closer similarities between Saadanius and crown catarrhines, particularly its ectotympanic, suggest Saadanius of all known fossil primates most closely resembled the last common ancestor of living catarrhines. Its discovery has provided new details about human evolution
, particularly the split between the Old World monkeys and the ape lineage that eventually led to humans.
The discovery of Saadanius provides new evidence for competing hypotheses about the facial appearance of the ancestral crown catarrhines, or common ancestor. One reconstruction is based on living catarrhine traits and predicts a short face and a rounded braincase, similar to that of a gibbon. Another reconstruction, based on the morphology
of early Miocene
apes and the basal
cercopithecoid Victoriapithecus, predicts that the last common ancestor had a projecting snout and tall face, like that of living baboon
s and the oldest fossil apes and Old World monkeys. The conservative features of Saadanius, similar to those of the older stem catarrhines, support the latter hypothesis, according to Zalmout et al. However, one palaeontologist, Eric Delson, has cautioned that geological pressure may have distorted the shape of the skull.
Saadanius may also help resolve the age of the hominoid–cercopithecoid split. Paleoanthropological
work has typically placed the divergence between 25 and 23 mya, but genetic-based estimates have placed it in the early Oligocene, approximately 33 mya. Despite the predictions from the genetic tests, little fossil evidence has been found for a last common ancestor between 30 and 23 mya, favoring a later split. Only isolated teeth of Kamoyapithecus
hinted at the existence of potential basal hominoids
in the late Oligocene (between 24 and 27.5 mya). With the discovery of Saadanius, Zalmout et al. suggested a later split than the genetic data, dating between 29–28 and 24 mya.
The fossil find has also been seen by the SGS as an important find for Saudi Arabia, because it enriches the fossil record for the region. As a result of the find, both the SGS and the University of Michigan are considering more collaborative field explorations in the country.
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...
of fossil primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
dating to 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...
that is closely related to the common ancestor
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....
of the Old World monkey
Old World monkey
The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous...
s and ape
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
s, collectively known as catarrhines
Catarrhini
Catarrhini is one of the two subdivisions of the higher primates . It contains the Old World monkeys and the apes, which in turn are further divided into the lesser apes or gibbons and the great apes, consisting of the orangutans, gorillas, chimpanzees, bonobos, and humans...
. It is represented by a single species, Saadanius hijazensis, which is known only from a single partial skull tentatively dated between 29 and 28 mya (million years ago). It was discovered in 2009 in western Saudi Arabia
Saudi Arabia
The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
near Mecca
Mecca
Mecca is a city in the Hijaz and the capital of Makkah province in Saudi Arabia. The city is located inland from Jeddah in a narrow valley at a height of above sea level...
and was first described in 2010 after a comparison with both living and fossil catarrhines.
Saadanius had a longer face than living catarrhines and lacked the advanced frontal sinus
Frontal sinus
Sinuses are mucosa-lined airspaces within the bones of the face and skull. The frontal sinuses, situated behind the superciliary arches, are absent at birth, but are generally fairly well developed between the seventh and eighth years, only reaching their full size after puberty...
(airspaces in the facial bones) found in living catarrhines. However, it had a bony ear tube (ectotympanic
Ectotympanic
The ectomtympanic is a bone that suspends the eardrum in mammals. It is homologus with the angular....
) and teeth comparable to those of living catarrhines. The discovery of Saadanius may help answer questions about the appearance of the last common ancestors of Old World monkeys and apes and help date the evolutionary split between these two primate groups.
Discovery
Saadanius is known from a single specimen, the holotypeHolotype
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...
, named "SGS-UM 2009-002", stored in Jeddah
Jeddah
Jeddah, Jiddah, Jidda, or Jedda is a city located on the coast of the Red Sea and is the major urban center of western Saudi Arabia. It is the largest city in Makkah Province, the largest sea port on the Red Sea, and the second largest city in Saudi Arabia after the capital city, Riyadh. The...
, Saudi Arabia, at the Paleontology Unit of the Saudi Geological Survey
Saudi Geological Survey
The Saudi Geological Survey is the national geologic survey of the Kingdom of Saudi Arabia and was established as an independent entity attached to the Ministry of Petroleum and Mineral Resources following a Council of Ministers Decision in 1999...
(SGS). Its type locality, or the place it was discovered, was on top of an oolitic
Oolite
Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic word òoion for egg. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks composed of ooids larger than 2 mm are called pisolites...
ironstone
Ironstone
Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical repacement, that contains a substantial proportion of an iron compound from which iron either can be or once was smelted commercially. This term is customarily restricted to hard coarsely...
fossil bed of the middle Shumaysi Formation located in the southwest corner of Harrat Al Ujayfa, in western Saudi Arabia, close to Mecca. The specimen was discovered in February 2009 by paleontologist Iyad Zalmout, who had traveled to the region to search for ancient whale
Evolution of cetaceans
The cetaceans are marine mammal descendants of land mammals. Their terrestrial origins are indicated by:* Their need to breathe air from the surface;* The bones of their fins, which resemble the limbs of land mammals...
and dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
fossils. While looking for dinosaur fossils in an area that, according to the maps he was working from, contained rock layers that dated to 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...
(145–65 mya), Zalmout found the jawbone of a hippo-like creature, called an anthracotheriid
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...
(a close relative of whales and hippos), which dated to 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...
or Oligocene. This indicated that the rock layers were much younger than what was dated on the maps. The following day, he noticed fossil teeth, which he immediately recognized as those of a primate. Zalmout emailed a photo of the teeth to paleontologist Philip D. Gingerich
Philip D. Gingerich
Philip D. Gingerich is a Professor of Paleontology, Professor of Geological Sciences, Professor of Biology, Professor of Anthropology and Director, Museum of Paleontology at the University of Michigan. His research focus is in vertebrate paleontology, especially the Paleocene-Eocene transition and...
, with whom he was working as a postdoctoral fellow. Gingerich, an expert on ancient primates and whales, confirmed that it was indeed a primate. Due to a tight schedule, Zalmout had to leave the exposed fossil embedded in the rock for the next few days because collecting it would require days of work. The fossil was soon recovered by a joint expedition involving the SGS and the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
.
The fossil was not formally described until 2010 when its discovery was announced in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
. The fossil was dated to about 28 or 29 million years ago based on comparisons of fossils of anthracotheriids and paenungulates
Paenungulata
Paenungulata is a taxon that groups some remarkable mammals, including three orders that are extant: Proboscidea , Sirenia , and Hyracoidea . At least two more orders are known only as fossils, namely Embrithopoda and Desmostylia...
(members of the group that includes elephants and hyraxes) found nearby with fossils from similarly aged African deposits. However, the date has yet to be confirmed by other dating techniques. 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...
name, Saadanius, comes from the Arabic word, saadan , which is the collective term for apes and monkeys. The species name, hijazensis, is a reference to the al Hijaz
Hejaz
al-Hejaz, also Hijaz is a region in the west of present-day Saudi Arabia. Defined primarily by its western border on the Red Sea, it extends from Haql on the Gulf of Aqaba to Jizan. Its main city is Jeddah, but it is probably better known for the Islamic holy cities of Mecca and Medina...
region, in which it was discovered.
Type specimen
Saadanius had a longer face than living catarrhines, more closely resembling New World monkeyNew World monkey
New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...
s in appearance, although it was larger—possibly the size of a gibbon
Gibbon
Gibbons are apes in the family Hylobatidae . The family is divided into four genera based on their diploid chromosome number: Hylobates , Hoolock , Nomascus , and Symphalangus . The extinct Bunopithecus sericus is a gibbon or gibbon-like ape which, until recently, was thought to be closely related...
. Its enlarged, deep-rooted canine teeth
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
, the diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
(space) between its canine teeth and second incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s, and its sagittal crest
Sagittal crest
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull of many mammalian and reptilian skulls, among others....
(ridge of bone running lengthwise down the top of the skull) suggest that the specimen was a male. These features are shared among male Old World monkeys. Saadanius lacks the advanced frontal sinus
Frontal sinus
Sinuses are mucosa-lined airspaces within the bones of the face and skull. The frontal sinuses, situated behind the superciliary arches, are absent at birth, but are generally fairly well developed between the seventh and eighth years, only reaching their full size after puberty...
found in living catarrhines, but it does possess an ectotympanic
Ectotympanic
The ectomtympanic is a bone that suspends the eardrum in mammals. It is homologus with the angular....
, or bony ear tube, found in living catarrhines. Propliopithecoids, the oldest stem group of catarrhines, which date back 35 to 30 mya, lacked a fully developed ectotympanic.
The specimen had serious puncture wounds on the front of the skull, indicating that it had been preyed upon by a large 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...
. One puncture wound was on the right side of the braincase and may have been the fatal blow. There was also a bite mark on the frontal trigon.
Like other catarrhine primates, Saadanius was probably a tree-dweller (arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...
). During the time it would have lived, the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
had not yet formed, and new plant and animal species would have been arriving from nearby Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
as it converged with the Afro-Arabian landmass.
Phylogeny and significance
Comparative anatomyComparative anatomy
Comparative anatomy is the study of similarities and differences in the anatomy of organisms. It is closely related to evolutionary biology and phylogeny .-Description:...
and cladistic analysis
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
indicate that Saadanius is more closely related to the last common ancestor of crown
Crown group
A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...
catarrhines than any other known fossil catarrhines, placing the common ancestry of Catarrhini in Arabia and Africa. Other stem catarrhines include propliopithecoids, such as Aegyptopithecus
Aegyptopithecus
Aegyptopithecus zeuxis means “linking Egyptian ape”. It was discovered by E. Simons in 1965. There is controversy over whether or not Aegyptopithecus should be a genus on its own or whether it should be moved into the genus Propliopithecus. If Aegyptopithecus is placed in its own genus, then there...
, and pliopithecoids, such as Pliopithecus
Pliopithecus
Pliopithecus is a genus of extinct primates of the Miocene and Pliocene. It was discovered in 1837 by Édouard Lartet in France, with fossils subsequently discovered in Switzerland and Spain....
. The closer similarities between Saadanius and crown catarrhines, particularly its ectotympanic, suggest Saadanius of all known fossil primates most closely resembled the last common ancestor of living catarrhines. Its discovery has provided new details about human evolution
Human evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
, particularly the split between the Old World monkeys and the ape lineage that eventually led to humans.
The discovery of Saadanius provides new evidence for competing hypotheses about the facial appearance of the ancestral crown catarrhines, or common ancestor. One reconstruction is based on living catarrhine traits and predicts a short face and a rounded braincase, similar to that of a gibbon. Another reconstruction, based on the morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of early Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
apes and the basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
cercopithecoid Victoriapithecus, predicts that the last common ancestor had a projecting snout and tall face, like that of living baboon
Baboon
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...
s and the oldest fossil apes and Old World monkeys. The conservative features of Saadanius, similar to those of the older stem catarrhines, support the latter hypothesis, according to Zalmout et al. However, one palaeontologist, Eric Delson, has cautioned that geological pressure may have distorted the shape of the skull.
Saadanius may also help resolve the age of the hominoid–cercopithecoid split. Paleoanthropological
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...
work has typically placed the divergence between 25 and 23 mya, but genetic-based estimates have placed it in the early Oligocene, approximately 33 mya. Despite the predictions from the genetic tests, little fossil evidence has been found for a last common ancestor between 30 and 23 mya, favoring a later split. Only isolated teeth of Kamoyapithecus
Kamoyapithecus
Kamoyapithecus was a primate that lived in Africa during the late Oligocene period, about 24.2-27.5 million years ago. First found in 1948 as part of a University of California, Berkeley expedition, it was at first thought to be under a form of Proconsul by C.T...
hinted at the existence of potential basal hominoids
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
in the late Oligocene (between 24 and 27.5 mya). With the discovery of Saadanius, Zalmout et al. suggested a later split than the genetic data, dating between 29–28 and 24 mya.
The fossil find has also been seen by the SGS as an important find for Saudi Arabia, because it enriches the fossil record for the region. As a result of the find, both the SGS and the University of Michigan are considering more collaborative field explorations in the country.
External links
- A piece in the monkey puzzle – A short video from Nature explaining the Saadanius discovery and its significance.