''Technosaurus'' (meaning "Tech lizard", for

Texas Tech University Texas Tech University (Texas Tech, Tech, or TTU) is a public university, public research university in Lubbock, Texas, United States. Established on February 10, 1923, and called Texas Technological College until 1969, it is the flagship instit ...

) is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of silesaurid dinosauriforms, from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

Cooper Canyon Formation ( Dockum Group) of

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, United States. For about 20 years after its description, it was thought to be a basal ornithischian dinosaur, but better remains of other Triassic archosaurs have cast doubt on this interpretation. As named, it was a chimera of different animals.

Description and history

''Technosaurus'' is based on TTUP P9021, which initially consisted of a

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

(tip of the upper jaw), two lower jaw pieces, a back

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

, and an

astragalus Astragalus may refer to: * ''Astragalus'' (plant), a large genus of herbs and small shrubs *Astragalus (bone) The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...

. ''Technosaurus'' and its

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''T. smalli'', were named by Sankar Chatterjee in 1984. He described it as a fabrosaurid, a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of small, early ornithischians now considered to have been an artificial grouping. Material from the quarry where P9021 was found is disassociated and comes from a variety of Late Triassic animals, which would prove problematic. The genus was reviewed in 1991 by

Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago who has discovered several new dinosaur species on several continents, including at sites in Inner Mongolia, Argentina, Morocco and Niger. ...

, who interpreted the premaxilla and a fragment from the front of the lower jaw as pertaining to a hatchling

prosauropod Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the Sauropoda, sauropods and their ancestral relatives. Sauropods generally grew to very large siz ...

, and found the vertebra to be indeterminate and the astragalus an unidentifiable fragment. Thus, he restricted the remains to be considered ''Technosaurus'' to the second lower jaw piece, a posterior fragment. Further review in the light of new remains spurred re-evaluation of purported Triassic dinosaurs, particularly ornithischians named from tooth or jaw material. Irmis ''et al.'' (2007) agreed with the removal of the vertebra and astragalus, but found no characteristics that were unambiguously dinosaurian in the skull fragments. They noted similarities to ''Silesaurus'' in the jaw fragments Sereno had excluded, and themselves excluded the posterior fragment as actually belonging to the unusual

rauisuchia "Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians ...

n '' Shuvosaurus''. These authors would later restate their case, concluding that ''Technosaurus'', defined only by the premaxilla and non-''Shuvosaurus'' lower jaw fragment, was a valid, diagnostic genus, but could not be definitely classified beyond

Archosauriformes Archosauriformes (Ancient Greek, Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing Archosaur, archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemmin ...

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'', and was unlikely to be either an ornithischian or

sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lo ...

dinosaur.

References

{{Taxonbar, from=Q682358 Silesauridae Norian genera Late Triassic reptiles of North America Triassic geology of Texas Paleontology in Texas Fossil taxa described in 1984 Taxa named by Sankar Chatterjee