Antetonitrus
Encyclopedia
Antetonitrus is the oldest known genus
of sauropod dinosaur
, living during the Late Triassic Period of southern Africa
. It was a quadruped
al herbivore
, like many of its later relatives, although it was far smaller than some of them. Antetonitrus was the largest animal in its environment, reaching up to 33 feet (10 m) long and weighing up to two tons, but still shows some primitive adaptations to use the forelimbs for grasping, instead of purely for weight support.
n expert on early sauropodomorphs, named Antetonitrus in a 2003 report co-authored by South Africa
n James Kitching
. The name is derived from the Latin
ante- ("before") and tonitrus ("thunder"), which refers to its existence, before other known sauropods, specifically Brontosaurus
("thunder lizard"). Brontosaurus is actually a junior synonym of Apatosaurus
, but the name is still used in popular culture, and sauropods are sometimes called "thunder lizards" in vernacular
terms. The one known species of Antetonitrus is called A. ingenipes, from the Latin ingens ("massive") and pes ("foot"), because its shows the beginning of the development of feet designed solely to support weight.
The fossil
s now known as Antetonitrus were actually discovered by Kitching in 1981 in the Free State
of South Africa, and were stored in the Bernard Price Institute where they were labeled as Euskelosaurus
. Yates recognized them as a separate taxon and published a description several years later. The holotype
, or original specimen, consists of several vertebrae and numerous bones from both forelimb and hind limb, all presumed to be from one individual. Five more limb bones from another smaller individual were also referred to the genus.
sauropods, the wrist bones are large and thick, arranged in such a way as to lock the hand into a permanently pronated
position for full-time weight support, and the hand is incapable of grasping.
sauropod, occupying a position between more derived animals such as Isanosaurus
or Vulcanodon
, and more basal sauropods like Melanorosaurus
. The back vertebrae are extremely similar to Lessemsaurus
from South America, while the limb bones are similar to Blikanasaurus
, another stocky early sauropod from South Africa. However, these animals were not included in a cladistic analysis with Antetonitrus because they are poorly known (Yates & Kitching, 2003).
While Antetonitrus is not the earliest sauropod from a phylogenetic standpoint, it currently the oldest known sauropod chronologically
, or rather tied for that distinction with other early sauropods from the same formation, like Melanorosaurus and Blikanasaurus. Fossils of these animals were recovered from the Lower Elliot Formation, which dates to the Norian
stage of the Late Triassic
, or approximately 221 to 210 million years ago. Before Antetonitrus and the other Lower Elliot animals were recognized as sauropods, the oldest known sauropod had been Isanosaurus from the Rhaetian
stage, a slightly younger segment of the Triassic, of Thailand
(Buffetaut et al., 2000).
Early sauropods and their prosauropod relatives were found around the world as all of the continents were at the time united into the single supercontinent, Pangaea
, which made dispersal
across the entire terrestrial world possible.
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 sauropod 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...
, living during the Late Triassic Period of southern 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...
. It was a quadruped
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"...
al 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...
, like many of its later relatives, although it was far smaller than some of them. Antetonitrus was the largest animal in its environment, reaching up to 33 feet (10 m) long and weighing up to two tons, but still shows some primitive adaptations to use the forelimbs for grasping, instead of purely for weight support.
History
Adam Yates, an AustraliaAustralia
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...
n expert on early sauropodomorphs, named Antetonitrus in a 2003 report co-authored by South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
n James Kitching
James Kitching
James William Kitching was a South African vertebrate palaeontologist and regarded as one of the world’s greatest fossil finders.-Career:...
. The name is derived from the 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...
ante- ("before") and tonitrus ("thunder"), which refers to its existence, before other known sauropods, specifically Brontosaurus
Apatosaurus
Apatosaurus , also known by the popular but scientifically deprecated synonym Brontosaurus, is a genus of sauropod dinosaur that lived from about 154 to 150 million years ago, during the Jurassic Period . It was one of the largest land animals that ever existed, with an average length of and a...
("thunder lizard"). Brontosaurus is actually a junior synonym of Apatosaurus
Apatosaurus
Apatosaurus , also known by the popular but scientifically deprecated synonym Brontosaurus, is a genus of sauropod dinosaur that lived from about 154 to 150 million years ago, during the Jurassic Period . It was one of the largest land animals that ever existed, with an average length of and a...
, but the name is still used in popular culture, and sauropods are sometimes called "thunder lizards" in vernacular
Vernacular
A vernacular is the native language or native dialect of a specific population, as opposed to a language of wider communication that is not native to the population, such as a national language or lingua franca.- Etymology :The term is not a recent one...
terms. The one known species of Antetonitrus is called A. ingenipes, from the Latin ingens ("massive") and pes ("foot"), because its shows the beginning of the development of feet designed solely to support weight.
The fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s now known as Antetonitrus were actually discovered by Kitching in 1981 in the Free State
Free State
The Free State is a province of South Africa. Its capital is Bloemfontein, which is also South Africa's judicial capital. Its historical origins lie in the Orange Free State Boer republic and later Orange Free State Province. The current borders of the province date from 1994 when the Bantustans...
of South Africa, and were stored in the Bernard Price Institute where they were labeled as Euskelosaurus
Euskelosaurus
Euskelosaurus was a semi-bipedal dinosaur from the Late Triassic. It was a prosauropod that lived in the Late Triassic Period, in present-day South Africa, Lesotho, and Zimbabwe. It was first described by Thomas Henry Huxley in 1866 as Euskelesaurus brownii based on holotype BMNH R1625, limb and...
. Yates recognized them as a separate taxon and published a description several years later. 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...
, or original specimen, consists of several vertebrae and numerous bones from both forelimb and hind limb, all presumed to be from one individual. Five more limb bones from another smaller individual were also referred to the genus.
Description
Antetonitrus shows several features which appear to be approaching those of sauropods, but still retains some primitive features. Unlike most of its smaller and more lightly built ancestors, Antetonitrus was primarily quadrupedal. Like sauropods, its forelimbs were much longer relative to its hind legs than earlier animals, and the wrist bones were broader and thicker to support more weight. However, the first digit of the hand, also called the "thumb" or pollex, was still twisted and flexible, capable of grasping against the hand. In more derivedDerived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
sauropods, the wrist bones are large and thick, arranged in such a way as to lock the hand into a permanently pronated
Anatomical terms of motion
The movement of body structures is accomplished by the contraction of muscles. Muscles may move parts of the skeleton relatively to each other, or may move parts of internal organs relatively to each other. All such movements are classified by the directions in which the affected structures are moved...
position for full-time weight support, and the hand is incapable of grasping.
Classification
A cladistic analysis recognizes Antetonitrus as a basalBasal (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:...
sauropod, occupying a position between more derived animals such as Isanosaurus
Isanosaurus
Isanosaurus was one of the first true sauropod dinosaurs, with all four legs always on the ground. It lived 210 million years ago in Thailand. The type species is Isanosaurus attavipachi...
or Vulcanodon
Vulcanodon
Vulcanodon was a relatively small early sauropod dinosaur genus from the Early Jurassic of southern Africa. About 6.5 metres long, Vulcanodon was herbivorous and had unusually long bones of the first toe and large claws on the inside toes. The type species, V. karibaensis, was formally...
, and more basal sauropods like Melanorosaurus
Melanorosaurus
Melanorosaurus , is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. A herbivore from South Africa, it had a large body and sturdy limbs, suggesting it moved about on all fours...
. The back vertebrae are extremely similar to Lessemsaurus
Lessemsaurus
Lessemsaurus is an extinct genus of sauropodomorph dinosaur named for the writer of popular science books Don Lessem. The type species, L. sauropoides, was formally described by José Fernando Bonaparte in 1999...
from South America, while the limb bones are similar to Blikanasaurus
Blikanasaurus
Blikanasaurus was a genus of sauropodomorph dinosaur found in Lower Elliot Formation rocks from the Late Triassic in what is now South Africa's Cape Province. Known from a left lower limb only, it has been variously classified as a prosauropod or basal sauropod...
, another stocky early sauropod from South Africa. However, these animals were not included in a cladistic analysis with Antetonitrus because they are poorly known (Yates & Kitching, 2003).
While Antetonitrus is not the earliest sauropod from a phylogenetic standpoint, it currently the oldest known sauropod chronologically
Chronology
Chronology is the science of arranging events in their order of occurrence in time, such as the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events".Chronology is part of periodization...
, or rather tied for that distinction with other early sauropods from the same formation, like Melanorosaurus and Blikanasaurus. Fossils of these animals were recovered from the Lower Elliot Formation, which dates to the Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
stage of the Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
, or approximately 221 to 210 million years ago. Before Antetonitrus and the other Lower Elliot animals were recognized as sauropods, the oldest known sauropod had been Isanosaurus from the Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...
stage, a slightly younger segment of the Triassic, of Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
(Buffetaut et al., 2000).
Early sauropods and their prosauropod relatives were found around the world as all of the continents were at the time united into the single supercontinent, Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
, which made dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
across the entire terrestrial world possible.
External links
- National Geographic article about the discovery of Antetonitrus.
- Post about Antetonitrus on the Dinosaur Mailing List, written by Adam Yates.