''Thadeosaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ...

reptile belonging to the family

Younginidae Younginidae is an extinct family of neodiapsid reptiles from the Late Permian and Early Triassic. In a phylogenetic context, younginids are near the base of the clade Neodiapsida. Younginidae includes the species '' Youngina capensis'' from th ...

. Fossils have been found in the

Lower Sakamena Formation Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Gloucestershire, England See also *Nizhny Nizhny (russian: Ни́жний; masculine), Nizhnyaya (; feminine), or Nizhneye (russian: Ни́� ...

(

Sakamena Group Sakamena is a village near Betroka in the region of Anosy in Madagascar. Sakamena is also the name of a Permian sedimentary geological formation that has yielded many vertebrate fossil, including Triadobatrachus (the first lissamphibian), Claudio ...

) of the

Morondava Basin Morondava Basin is one of the major sedimentary basins of Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island co ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

1981 Events January * January 1 ** Greece enters the European Economic Community, predecessor of the European Union. ** Palau becomes a self-governing territory. * January 10 – Salvadoran Civil War: The FMLN launches its first major off ...

, and date to the late

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...

to the early

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

period.

Description

''Thadeosaurus'' was a

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia al ...

-like animal, with a remarkably long tail that comprised about two thirds of the animal's total length of . It also had long toes, especially on the hind legs, which would have given it a powerful stride, since the toes would still touch the ground while the foot was being raised. Combined with a strong

breast bone The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...

to increase the strength in the forelimbs, this means that ''Thadeosaurus'' was probably a good runner. Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

from Reisz ''et al.'' (2011) showing the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

position of ''Thadeosaurus'' among other early diapsids:

References

Prehistoric neodiapsids Prehistoric reptile genera Lopingian reptiles of Africa Early Triassic reptiles of Africa Changhsingian genus first appearances Induan genus extinctions Fossils of Madagascar Permian Madagascar Triassic Madagascar Fossil taxa described in 1981 {{permian-reptile-stub