Ohmdenosaurus
Encyclopedia
Ohmdenosaurus is the name given to a genus
of herbivorous dinosaur
from the Early Jurassic
. It was a very small (four meters long) perhaps vulcanodontid
sauropod which lived in Germany
. Only a couple of fragmentary leg bones were found.
In the seventies German palaeontologist Rupert Wild, visiting the Urwelt-Museum Hauff at Holzmaden
, noticed a fossil in a display labelled as a plesiosaur
which he recognised to be a dinosaur bone instead. It proved to be impossible to establish the exact provenance of the remains. In 1978 it was named and described by him as the type species
Ohmdenosaurus liasicus. The generic name refers to Ohmden
, a town in Baden-Württemberg
near the quarry the remains were probably found in. The specific name refers to the Lias
, an old name for the Early Jurassic.
The holotype
, which lacked an inventory number, was apparently found in the famous Posidonia Shale
, marine strata dating from the middle Toarcian
, as can be established from the presence of the snail
Coelodiscus
in the matrix rock containing the only partially prepared bones. It consists of a tibia
, an astragalus
and a calcaneus. The bones, disarticulated in the fossil, show signs of weathering, evidence that the animal died on land and that only later its bones were washed into the sea. The tibia is only 405 millimetres long, indicating a remarkably small individual for a sauropod.
The shape of the fourteen centimetres wide astragalus, like that of a sandal and not convex on top as with the derived Neosauropoda
, proves that Ohmdenosaurus is a very basal sauropod. In 1990 John Stanton McIntosh classified Ohmdenosaurus in the Vulcanodontidae
but that concept then functioned as a waste-basket taxon for all kinds of unrelated basal sauropods. It has not been confirmed by an exact analysis as a vulcanodontid in the modern sense.
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 herbivorous 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...
from the Early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
. It was a very small (four meters long) perhaps vulcanodontid
Vulcanodontidae
The Early Jurassic sauropod dinosaurs Zizhongosaurus, Barapasaurus, Tazoudasaurus, and Vulcanodon may form a natural group of basal sauropods called the Vulcanodontidae. Basal vulcanodonts include some of the earliest known examples of sauropods. The family-level name Vulcanodontidae was erected by...
sauropod which lived 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...
. Only a couple of fragmentary leg bones were found.
In the seventies German palaeontologist Rupert Wild, visiting the Urwelt-Museum Hauff at Holzmaden
Holzmaden
Holzmaden is a town in Baden-Württemberg, Germany that lies between Stuttgart and Ulm.The ground in and around the city contains rich layers of well preserved fossils of the Jurassic period. The fossils are found in the 160 million year old Posidonia Shale and displayed in the local Museum Hauff...
, noticed a fossil in a display labelled as a plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
which he recognised to be a dinosaur bone instead. It proved to be impossible to establish the exact provenance of the remains. In 1978 it was named and described by him as the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
Ohmdenosaurus liasicus. The generic name refers to Ohmden
Ohmden
Ohmden is a town in the district of Esslingen in Baden-Württemberg in Germany....
, a town in Baden-Württemberg
Baden-Württemberg
Baden-Württemberg is one of the 16 states of Germany. Baden-Württemberg is in the southwestern part of the country to the east of the Upper Rhine, and is the third largest in both area and population of Germany's sixteen states, with an area of and 10.7 million inhabitants...
near the quarry the remains were probably found in. The specific name refers to the Lias
Lias
Lias may refer to:*In geology:**The Lias Group, a group in the stratigraphy of Great Britain, formed during the Late Triassic to Early Jurassic epochs. It includes the Blue Lias and White Lias...
, an old name for the Early Jurassic.
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...
, which lacked an inventory number, was apparently found in the famous Posidonia Shale
Posidonia Shale
The Posidonia Shale is a Lower Jurassic geological formation famous for its exceptionally well-preserved complete skeletons of fossil marine fish and reptiles. The Posidonienschiefer as German paleontologists call it, takes its name from the ubiquitous fossils of Posidonia bronni that characterize...
, marine strata dating from the middle Toarcian
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age or stage in the Early or Lower Jurassic. It spans the time between 183.0 Ma and 175.6 Ma...
, as can be established from the presence of the snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
Coelodiscus
Coelodiscus
Ceolodiscus is a genus in the gastropod family Euomphalidae from the Lower and Middle Jurassic of Europe. The shell is small but stocky; involute or with a slightly protruding spire. Whorls are generally smooth, evenly rounded and slightly overlapping; umbilicus deep, aperture ovate.-References:*J....
in the matrix rock containing the only partially prepared bones. It consists of a 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....
, an astragalus
Astragalus
Astragalus is a large genus of about 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae, subfamily Faboideae. The genus is native to temperate regions of the Northern Hemisphere...
and a calcaneus. The bones, disarticulated in the fossil, show signs of weathering, evidence that the animal died on land and that only later its bones were washed into the sea. The tibia is only 405 millimetres long, indicating a remarkably small individual for a sauropod.
The shape of the fourteen centimetres wide astragalus, like that of a sandal and not convex on top as with the derived Neosauropoda
Neosauropoda
Neosauropoda is a division-level clade of sauropods within Dinosauria, and consists of the group leading to Diplodocoidea and Macronaria. Haplocanthosaurus was a typical basal neosauropod from around 150 million years ago, in the Late Jurassic...
, proves that Ohmdenosaurus is a very basal sauropod. In 1990 John Stanton McIntosh classified Ohmdenosaurus in the Vulcanodontidae
Vulcanodontidae
The Early Jurassic sauropod dinosaurs Zizhongosaurus, Barapasaurus, Tazoudasaurus, and Vulcanodon may form a natural group of basal sauropods called the Vulcanodontidae. Basal vulcanodonts include some of the earliest known examples of sauropods. The family-level name Vulcanodontidae was erected by...
but that concept then functioned as a waste-basket taxon for all kinds of unrelated basal sauropods. It has not been confirmed by an exact analysis as a vulcanodontid in the modern sense.
External links
- Ohmdenosaurus in The Dinosaur Encyclopaedia, at Dino Russ's Lair