Leptictidium
Encyclopedia
Leptictidium is an extinct
genus
of small mammal
s; together with macropods and human
s, they are the only known completely bipedal mammals. Comprising five species, they resembled today's elephant shrew
s. They are especially interesting for their combination of characteristics typical of primitive eutheria
ns with highly specialized adaptations, such as powerful hind legs and a long tail which aided in locomotion. They were omnivorous, their diet a combination of insect
s, lizard
s and small mammal
s. One of the first branches to split from basal eutherians, they appeared in the Lower Eocene
, a time of warm temperatures and high humidity, roughly fifty million years ago. Although they were widespread throughout Europe
, they became extinct around thirty-five million years ago with no descendants, probably because they were adapted to live in forest
ecosystem
s and were unable to adapt to the open plains of the Oligocene
.
Leptictidium is a special animal because of the way its anatomy combines quite primitive elements with elements which prove a high degree of specialization. It had small fore legs and large hind legs, especially at the distal side (that further from the body). The lateral phalanges
of its forelegs (fingers I and V) were very short and weak, finger III was longer and fingers II and IV were roughly equal in size, and slightly shorter than finger III. The tips of the phalanges were elongated and tapered.
The ankle
s and the sacroiliac joint
were quite loosely fixed, while the pelvis
had a flexible joint with only one coccygeal
vertebra. The anteorbital muscle
fenestrae
in their crania suggest they probably had a long and mobile snout, similar to that of elephant shrews.
Leptictidium had wide diastemata
in the antemolar row, its upper molar teeth were more transverse than those of the North American leptictids
and its fourth premolar
s were molariform. Its C1 canines
were incisiviform. Its dentition
was quite small in comparison to the size of the mandible
and the animal as a whole.
It varied between 60 and 90 cm (24-36 in) in length (more than half of which belonged to the bald tail), and 20 cm (8 in) in height. It weighed a couple of kilograms. These sizes could vary from one specimen to another.
is used, it is probable that Leptictidium hopped along with its body tilted forward, using its tail as a counterweight. On the other hand, elephant shrew
s combine both types of locomotion
; they usually move on four legs
, but they can run on two legs to flee from a predator. Studies of the bone structure of Leptictidium have yielded contradicting information: its leg articulations appear too weak to have supported the shock of repeated jumps, but its long feet were obviously adapted for jumping rather than running.
Kenneth D. Rose compared the species L. nasutum with the leptictid
Leptictis dakotensis
. L. dakotensis had a series of traits which show it was a running animal which sometimes moved by jumping. Despite the marked similarities between Leptictis and Leptictidium, there are certain differences in their skeletons which prevent the example of Leptictis from being used to determine with certainty the way Leptictidium moved: the most important being that, unlike Leptictis, the tibia
and the fibula of Leptictidium were not fused together.
s of three different species of Leptictidium have been found in the Messel pit
in Germany
. The marks on their fur have been preserved, as well as their stomach
contents, which reveal Leptictidium were omnivore
s which fed on insect
s, lizard
s and small mammal
s. The holotype
of L. tobieni also had pieces of leaves
and notable amounts of sand in its abdomen, but it cannot be determined with certainty if the animal swallowed it.
Since Leptictidium young were very vulnerable to attacks of predators, it is probable that they were born quite developed and that they became independent when they were still quite young. From the behavior of today's elephant shrew, the possibility can be suggested that Leptictidium young went out to hunt with their mother, and that they learned to distinguish prey by licking their mother's mouth when she had just caught an animal, in order to know the flavor of food.
an subtropical forest
s of the Eocene
. From the beginning of this period, the temperature of the planet rose in one of the quickest (in geological
terms) and most extreme episodes of global warming in the geological record, termed Paleocene–Eocene Thermal Maximum. It was an episode of quick and intense (of up to 7°C in high latitudes) warming which lasted less than 100,000 years. The Thermal Maximum caused a great extinction which is used to distinguish the Eocene fauna
from that of the Paleocene
.
The global climate of the Eocene was probably the most homogeneous of the Cenozoic
; the temperature gradient
from the equator
to the poles
was half that of today's, and the deep ocean current
s were exceptionally warm. The polar regions were much warmer than today, maybe as warm as the Pacific Northwest
nowadays. Temperate forests reached the poles themselves, while rainy tropical climates reached 45º N. The greatest difference was in temperate latitudes; nevertheless, the climate at the tropics
was probably similar to today's.
In the Eocene, most of what today is Europe
, the Mediterranean
and south-west Asia
was submerged under the Tethys Sea. Both continent
s were separated by the Turgai Strait (an epeiric sea
). Due to high humidity and temperatures, most of the European continent was covered in vegetation
.
The region which today is Germany
was in a volcanically
active zone during the Eocene. It is thought that the Messel pit
could have been the old location of a volcanic lake saturated with CO2
. The lake would periodically release the gas it contained, creating a lethal cloud which would asphyxiate any animal in its path. This would explain the great number of non-aquatic species which have been found in the old lake-bed of the Messel pit.
In the lush forests of this region, Leptictidium shared its habitat with animals such as Godinotia
, Pholidocercus
, Palaeotis
or Propalaeotherium
. There were also predators: Asiatosuchus
, Lesmesodon, or the Messel giant ant
. The alpha predator was Gastornis
, a carnivorous bird almost two meters tall.
faunal stage. Tobien also uncovered a small skeleton he defined as a paratype
of the species, but Storch and Lister proved in 1985 that, in fact, the skeleton did not even belong to the genus
Leptictidium. It was the smallest species of all and was only sixty centimetres long. Several skeletons have been found at the Messel pit. Mathis
remarks the exceptional development of the paraconid (or mesiobucal cusp) of the lower P4 premolar
. Its premolars and molars were quite small in comparison to the dentition as a whole. The name of the species refers to the Roman
settlement of Auderia
.
in 1989. Fossils have been found in the lagerstätte at Robiac, Le Bretou, Lavergne, La Bouffie, Les Clapiès, Malpérié and Perrière (France
), in Upper Ludian strata. The mesostyle typical of the Leptictidium genus is not developed in this species. The species is dedicated to Léonard Ginsburg, French
paleontologist and deputy director of the Muséum national d'histoire naturelle
in París
.
strata. The tail of this species had 42-43 vertebrae, a number surpassed among mammal
s solely by the Long-tailed Pangolin
. Its premolar
and molar teeth were quite small in comparison to the dentition as a whole. The name of the species refers to the nose
of the animal. The holotype
is the complete skeleton of an adult specimen kept in the Forschungsinstitut Senckenberg in Frankfurt am Main.
in 1989. Fossils have been found in the lagerstätte at Sainte-Néboule, Baby, Sindou and Pécarel (France
), and it has a more primitive appearance than L. nasutum. It is known mainly from isolated teeth. It has a P4 with a much reduced paraconid, as well as very distinct entoconids and hypoconulids on M1 and M2. The species is dedicated to Bernard Sigé, French
paleontologist.
strata. The species is dedicated to Heinz Tobien, descriptor of the genus Leptictidium and promotor of research in the Messel pit during the 1960s. The holotype
is a complete and perfectly preserved skeleton of an adult specimen which was uncovered in September 1984 and which can be found at the Hessisches Landesmuseum Darmstadt. There is also a paratype; a non-complete and badly preserved specimen which can be found at the Institut Royal des Sciences Naturelles de Belgique.
It has a relatively robust mandible
with a relatively large mesostyle. The molariform premolar teeth are a characteristic of the Leptictidium genus as a whole which is very marked in the P4 premolars of L. tobieni. The well-developed mesostyle and the transversal configuration of the upper molars are other typical traits of this species.
s are specimens of the same species but of different age, or that two of these forms belonged to the same species with a marked sexual dimorphism
.
The Messel species developed very quickly a series of characteristic evolutionary traits, common to all of them, which separate them from the lagerstätte of Quercy
.
This table compares the size of different specimens of each species found in the Messel pit (sizes in millimetres).
† From the front edge of the orbit.
†† Above the incisura praeangularis.
paleontologist Christian Mathis
studied the evolutionary tendencies of the genus Leptictidium, based on comparison of the most primitive and the most recent species. From his observations, Mathis remarks:
Pseudorhyncocyon, the five Leptictidium species form the family Pseudorhyncocyonidae, one of the three which form the order Leptictida
. These families and genera are:
Order Leptictida
Because Leptictida is a paraphyletic group, this list does not take into account the families or genera with an uncertain or disputed affiliation.
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
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...
of small 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; together with macropods and human
Human
Humans are the only living species in the Homo genus...
s, they are the only known completely bipedal mammals. Comprising five species, they resembled today's elephant shrew
Elephant shrew
Elephant shrews or jumping shrews are small insectivorous mammals native to Africa, belonging to the family Macroscelididae, in the order Macroscelidea...
s. They are especially interesting for their combination of characteristics typical of primitive eutheria
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...
ns with highly specialized adaptations, such as powerful hind legs and a long tail which aided in locomotion. They were omnivorous, their diet a combination of insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s and small 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. One of the first branches to split from basal eutherians, they appeared in the Lower 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...
, a time of warm temperatures and high humidity, roughly fifty million years ago. Although they were widespread throughout 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...
, they became extinct around thirty-five million years ago with no descendants, probably because they were adapted to live in forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
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....
s and were unable to adapt to the open plains 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...
.
Description
Phalanges of the hand
The phalanges of the hand are commonly known as the finger bones. They are fourteen in number, three for each finger, and two for the thumb.Each consists of a body and two extremities....
of its forelegs (fingers I and V) were very short and weak, finger III was longer and fingers II and IV were roughly equal in size, and slightly shorter than finger III. The tips of the phalanges were elongated and tapered.
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...
s and the sacroiliac joint
Sacroiliac joint
The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...
were quite loosely fixed, while 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:...
had a flexible joint with only one coccygeal
Coccyx
The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...
vertebra. The anteorbital muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
fenestrae
Fenestrae
Fenestræ is a Latin word that means "window".* In histology, fenestræ are small pores in endothelial cells that allow for rapid exchange of molecules between sinusoid blood vessels and surrounding tissue...
in their crania suggest they probably had a long and mobile snout, similar to that of elephant shrews.
Leptictidium had wide diastemata
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:...
in the antemolar row, its upper molar teeth were more transverse than those of the North American leptictids
Leptictida
Leptictida is an extinct order of placental mammals. According to cladistic studies, they may be related to Euarchontoglires , although they are more often regarded as the first branch to split from basal eutherians.- Description :The leptictids are a characteristic example of the...
and its fourth premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s were molariform. Its C1 canines
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
were incisiviform. Its dentition
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
was quite small in comparison to the size of the mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
and the animal as a whole.
It varied between 60 and 90 cm (24-36 in) in length (more than half of which belonged to the bald tail), and 20 cm (8 in) in height. It weighed a couple of kilograms. These sizes could vary from one specimen to another.
Locomotion
One of the mysteries about Leptictidium is whether it moved by running or by jumping. Because there are very few completely bipedal mammals, it is difficult to find an appropriate living model to compare it with. If the kangarooKangaroo
A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...
is used, it is probable that Leptictidium hopped along with its body tilted forward, using its tail as a counterweight. On the other hand, elephant shrew
Elephant shrew
Elephant shrews or jumping shrews are small insectivorous mammals native to Africa, belonging to the family Macroscelididae, in the order Macroscelidea...
s combine both types of locomotion
Animal locomotion
Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...
; they usually move on four legs
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
, but they can run on two legs to flee from a predator. Studies of the bone structure of Leptictidium have yielded contradicting information: its leg articulations appear too weak to have supported the shock of repeated jumps, but its long feet were obviously adapted for jumping rather than running.
Kenneth D. Rose compared the species L. nasutum with the leptictid
Leptictida
Leptictida is an extinct order of placental mammals. According to cladistic studies, they may be related to Euarchontoglires , although they are more often regarded as the first branch to split from basal eutherians.- Description :The leptictids are a characteristic example of the...
Leptictis dakotensis
Leptictis
Leptictis is an extinct genus of mammal. It was related to the better-known Leptictidium.-References:*McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8...
. L. dakotensis had a series of traits which show it was a running animal which sometimes moved by jumping. Despite the marked similarities between Leptictis and Leptictidium, there are certain differences in their skeletons which prevent the example of Leptictis from being used to determine with certainty the way Leptictidium moved: the most important being that, unlike Leptictis, the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
and the fibula of Leptictidium were not fused together.
Behaviour
Perfectly preserved fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of three different species of Leptictidium have been found in the Messel pit
Messel pit
The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...
in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. The marks on their fur have been preserved, as well as their stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
contents, which reveal Leptictidium were omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
s which fed on insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s and small 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. 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...
of L. tobieni also had pieces of leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
and notable amounts of sand in its abdomen, but it cannot be determined with certainty if the animal swallowed it.
Since Leptictidium young were very vulnerable to attacks of predators, it is probable that they were born quite developed and that they became independent when they were still quite young. From the behavior of today's elephant shrew, the possibility can be suggested that Leptictidium young went out to hunt with their mother, and that they learned to distinguish prey by licking their mother's mouth when she had just caught an animal, in order to know the flavor of food.
Habitat
Leptictidium lived in the EuropeEurope
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...
an subtropical forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
s of the 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...
. From the beginning of this period, the temperature of the planet rose in one of the quickest (in geological
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
terms) and most extreme episodes of global warming in the geological record, termed Paleocene–Eocene Thermal Maximum. It was an episode of quick and intense (of up to 7°C in high latitudes) warming which lasted less than 100,000 years. The Thermal Maximum caused a great extinction which is used to distinguish the Eocene 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"...
from that of 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...
.
The global climate of the Eocene was probably the most homogeneous of the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
; the temperature gradient
Temperature gradient
A temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. The temperature gradient is a dimensional quantity expressed in units of degrees per unit length...
from the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
to the poles
Geographical pole
A geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation meets the surface of the body...
was half that of today's, and the deep ocean current
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
s were exceptionally warm. The polar regions were much warmer than today, maybe as warm as the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
nowadays. Temperate forests reached the poles themselves, while rainy tropical climates reached 45º N. The greatest difference was in temperate latitudes; nevertheless, the climate at the tropics
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
was probably similar to today's.
In the Eocene, most of what today is 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 Mediterranean
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and south-west 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...
was submerged under the Tethys Sea. Both continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
s were separated by the Turgai Strait (an epeiric sea
Epeiric Sea
An epeiric sea is a shallow sea that extends over part of a continent.Epeiric seas are usually associated with the marine transgressions of the geologic past, which have variously been due to either global eustatic sea level changes, local tectonic deformation, or both, and are occasionally...
). Due to high humidity and temperatures, most of the European continent was covered in vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...
.
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
was in a volcanically
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
active zone during the Eocene. It is thought that the Messel pit
Messel pit
The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...
could have been the old location of a volcanic lake saturated with CO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. The lake would periodically release the gas it contained, creating a lethal cloud which would asphyxiate any animal in its path. This would explain the great number of non-aquatic species which have been found in the old lake-bed of the Messel pit.
In the lush forests of this region, Leptictidium shared its habitat with animals such as Godinotia
Godinotia
Godinotia is an extinct genus of lemur-like prosimians belonging to the Adapidae family. It lived during the Eocene epoch , and its fossils have been found in the Messel Pit, Germany, showing that it already exhibited hominid features that would help make the primates such a successful group...
, Pholidocercus
Pholidocercus
Pholidocercus is an extinct monotypic genus of mammal related to and resembling the modern-day hedgehog with a single species Pholidocercus hassiacus. Like the hedgehog, it was covered in thin spines. Unlike hedgehogs, it had scales on its head in a helmet-like formation, and had a long, thick,...
, 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...
or Propalaeotherium
Propalaeotherium
Propalaeotherium was an early genus of perissodactyl ancestral to the horse endemic to Europe and Asia during the Middle Eocene.Its name means "before Palaeotherium", as it is the ancestor of Palaeotherium, another relative of early horses...
. There were also predators: Asiatosuchus
Asiatosuchus
Asiatosuchus is an extinct genus of large crocodilian. It is believed to have been a basal crocodile. Specimens have been found from Russia, Belgium, France, Germany, Mongolia, and possibly Pakistan. It existed from the Danian stage of the early Paleocene epoch to the Lutetian stage of the Eocene...
, Lesmesodon, or the Messel giant ant
Formicium
Formicium is an extinct collective genus of giant ants in the Formicidae subfamily Formiciinae. The genus currently contains three species, Formicium berryi, Formicium brodiei, and Formicium mirabile...
. The alpha predator was Gastornis
Gastornis
Gastornis is an extinct genus of large flightless bird that lived during the late Paleocene and Eocene epochs of the Cenozoic. It was named in 1855, after Gaston Planté, who had discovered the first fossils in Argile Plastique formation deposits at Meudon near Paris...
, a carnivorous bird almost two meters tall.
Leptictidium auderiense
Described by Heinz Tobien in 1962 based on a series of lower jaws from the LutetianLutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between and . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene subepoch...
faunal stage. Tobien also uncovered a small skeleton he defined as a paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
of the species, but Storch and Lister proved in 1985 that, in fact, the skeleton did not even belong to 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...
Leptictidium. It was the smallest species of all and was only sixty centimetres long. Several skeletons have been found at the Messel pit. Mathis
Christian Mathis
Christian Mathis is a French paleontologist. He mainly worked on the Lagerstätte of Robiac and Quercy in the South of France.Mathis described the following genus and species*Bouffinomus *Leptictidium ginsburgi*Leptictidium sigei...
remarks the exceptional development of the paraconid (or mesiobucal cusp) of the lower P4 premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
. Its premolars and molars were quite small in comparison to the dentition as a whole. The name of the species refers to the Roman
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....
settlement of Auderia
Dieburg
Dieburg is a town in southern Hessen, Germany. It was formerly the seat of the district of Dieburg, but is now part of the district of Darmstadt-Dieburg.-History:...
.
Leptictidium ginsburgi
Described by Christian MathisChristian Mathis
Christian Mathis is a French paleontologist. He mainly worked on the Lagerstätte of Robiac and Quercy in the South of France.Mathis described the following genus and species*Bouffinomus *Leptictidium ginsburgi*Leptictidium sigei...
in 1989. Fossils have been found in the lagerstätte at Robiac, Le Bretou, Lavergne, La Bouffie, Les Clapiès, Malpérié and Perrière (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...
), in Upper Ludian strata. The mesostyle typical of the Leptictidium genus is not developed in this species. The species is dedicated to Léonard Ginsburg, French
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...
paleontologist and deputy director of the Muséum national d'histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...
in París
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
.
Leptictidium nasutum
Described by Adrian Lister and Gerhard Storch in 1985. It was a middle-sized species which was seventy-five centimeters long. Several skeletons have been found in the Messel pit, in Lower LutetianLutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between and . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene subepoch...
strata. The tail of this species had 42-43 vertebrae, a number surpassed among 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 solely by the Long-tailed Pangolin
Long-tailed Pangolin
The Long-tailed Pangolin , also called the Black-bellied Pangolin or ipi, is an arboreal pangolin native to the sub-Saharan forests of Africa. Its common name is derived from its especially long tail...
. Its premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
and molar teeth were quite small in comparison to the dentition as a whole. The name of the species refers to the nose
Nose
Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the...
of the animal. 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...
is the complete skeleton of an adult specimen kept in the Forschungsinstitut Senckenberg in Frankfurt am Main.
Leptictidium sigei
Described by Christian MathisChristian Mathis
Christian Mathis is a French paleontologist. He mainly worked on the Lagerstätte of Robiac and Quercy in the South of France.Mathis described the following genus and species*Bouffinomus *Leptictidium ginsburgi*Leptictidium sigei...
in 1989. Fossils have been found in the lagerstätte at Sainte-Néboule, Baby, Sindou and Pécarel (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 it has a more primitive appearance than L. nasutum. It is known mainly from isolated teeth. It has a P4 with a much reduced paraconid, as well as very distinct entoconids and hypoconulids on M1 and M2. The species is dedicated to Bernard Sigé, French
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...
paleontologist.
Leptictidium tobieni
Described by Wighart von Koenigswald and Gerhard Storch in 1987. It was the largest species of all at ninety centimetres long. It is one of the species found in the Messel pit, in LutetianLutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between and . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene subepoch...
strata. The species is dedicated to Heinz Tobien, descriptor of the genus Leptictidium and promotor of research in the Messel pit during the 1960s. 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...
is a complete and perfectly preserved skeleton of an adult specimen which was uncovered in September 1984 and which can be found at the Hessisches Landesmuseum Darmstadt. There is also a paratype; a non-complete and badly preserved specimen which can be found at the Institut Royal des Sciences Naturelles de Belgique.
It has a relatively robust mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
with a relatively large mesostyle. The molariform premolar teeth are a characteristic of the Leptictidium genus as a whole which is very marked in the P4 premolars of L. tobieni. The well-developed mesostyle and the transversal configuration of the upper molars are other typical traits of this species.
Comparison of the Messel species
By observing the clear morphological differences in the dentition of the three species found in Messel, the possibility can be discarded that either the discovered fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s are specimens of the same species but of different age, or that two of these forms belonged to the same species with a marked sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
.
The Messel species developed very quickly a series of characteristic evolutionary traits, common to all of them, which separate them from the lagerstätte of Quercy
Quercy
Quercy is a former province of France located in the country's southwest, bounded on the north by Limousin, on the west by Périgord and Agenais, on the south by Gascony and Languedoc, and on the east by Rouergue and Auvergne....
.
This table compares the size of different specimens of each species found in the Messel pit (sizes in millimetres).
| Messel species comparison | |||||||
|---|---|---|---|---|---|---|---|
| species | L. auderiense | L. nasutum | L. tobieni | ||||
| specimens | LNK Me 418a |
SMF 78/1 |
SMF ME 1143 |
LNK Me 576 |
HLMD Me 8059 |
HLMD Me 8011a |
I. R. Sc. N. B. M1475 |
| Cranium | 67.4 | 67.2 | 88.2 | 89.8 | 88.6 | 101.1 | - |
| Head Head In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do.... +torso Torso Trunk or torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. The trunk includes the thorax and abdomen.-Major organs:... |
220 | 215 | 300 | 295 | 328 | 375 | - |
| Tail Tail The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds... |
(340) | 375 | 450 | 445 | 454 | 500 | - |
| Humerus Humerus The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.... |
31.8 | 32.3 | 41.9 | 41.9 | 43.1 | 45.7 | 46.6 |
| 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... |
29.4 | 31.8 | 45.6 | 44.2 | 45.3 | 51.2 | - |
| Radius Radius (bone) The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally... |
21.5 | 23.9 | 31.7 | 31.1 | 33.2 | 37.0 | 36.2 |
| 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:... |
54.5 | 56.5 | 77.8 | 77.1 | - | 85.7 | (82) |
| Femur Femur The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in... |
54.2 | 57.5 | 75.3 | 71.5 | 75.1 | 84.8 | (82) |
| Tibia Tibia The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones.... |
64.4 | 66.3 | 79.7 | 79.0 | 80.1 | 91.6 | 90.5 |
| Fibula | 57.4 | 58.7 | 75.2 | 72.3 | - | 86.6 | - |
| Calcaneus | 22.3 | 22.6 | 25.3 | 25.2 | - | 26.7 | 25.4 |
| Neurocranium † | 33.0 | 31.6 | 38.7 | 39.3 | 37.5 | 42.2 | 42.5 |
| Height of the lower jaw below M2 |
5.7 | 5.6 | 6.9 | 6.6 | 6.4 | 9.0 | 9.5 |
| Height of the mandibular ramus †† |
14.3 | - | 20.8 | 23.3 | 23.0 | 29.2 | 28.5 |
† From the front edge of the orbit.
†† Above the incisura praeangularis.
Evolutionary tendencies
In his work Quelques insectivores primitifs nouveaux de l'Eocène supérieur du sud de la France (1989), FrenchFrance
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...
paleontologist Christian Mathis
Christian Mathis
Christian Mathis is a French paleontologist. He mainly worked on the Lagerstätte of Robiac and Quercy in the South of France.Mathis described the following genus and species*Bouffinomus *Leptictidium ginsburgi*Leptictidium sigei...
studied the evolutionary tendencies of the genus Leptictidium, based on comparison of the most primitive and the most recent species. From his observations, Mathis remarks:
- an increase in size;
- a precocious merging of the hypoconulid and the entoconid on M3;
- a slight reduction of the width of the talonid on M3 in comparison to the anterior molars;
- the formation and development of a mesostile on the molariform jugal teeth P4-M3;
- the reduction of the parametastylar and metastylar regions of these same teeth (with some exceptions), in particular with a reduction of the parastylar lobe which rises less in the anterior part of M3 and possibly P4;
- a transverse shortening of the upper molarised teeth, which become more square;
- the development of accessory conuli on the preprotocrista and postprotocrista;
- the development of the postcingulum.
Related species
Together with the genusGenus
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...
Pseudorhyncocyon, the five Leptictidium species form the family Pseudorhyncocyonidae, one of the three which form the order Leptictida
Leptictida
Leptictida is an extinct order of placental mammals. According to cladistic studies, they may be related to Euarchontoglires , although they are more often regarded as the first branch to split from basal eutherians.- Description :The leptictids are a characteristic example of the...
. These families and genera are:
Order Leptictida
- Family Gypsonictopidae (Van Valen, 1967)
- Genus Gypsonictops (Simpson, 1924)
- Family Leptictidae (GillTheodore GillTheodore Nicholas Gill was an American ichthyologist, mammalogist, malacologist and librarian.Born and educated in New York City under private tutors, Gill early showed interest in natural history. He was associated with J...
, 1872)- Genus LeptictisLeptictisLeptictis is an extinct genus of mammal. It was related to the better-known Leptictidium.-References:*McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8...
(Leidy, 1868) - Genus Myrmecoboides (Gidley, 1915)
- Genus Ongghonia (Kellner & McKenna, 1996)
- Genus Palaeictops (Matthew, 1899)
- Genus Prodiacodon (Matthew, 1929)
- Genus Xenacodon (Matthew & Granger, 1921)
- Genus Leptictis
- Family Pseudorhyncocyonidae (Sigé, 1974)
- Genus Leptictidium (Tobien, 1962)
- Genus Pseudorhyncocyon (FilholHenri FilholHenri Filhol was a French medical doctor, malacologist and naturalist. He served as the expedition doctor and naturalist on the French 1874 Transit of Venus expedition to Campbell Island, New Zealand, with a peak on the island, Filhol Peak, being named after him...
, 1892)
Because Leptictida is a paraphyletic group, this list does not take into account the families or genera with an uncertain or disputed affiliation.