''Tatisaurus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

ornithischian Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the Early

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

from the

Lower Lufeng Formation The Lufeng Formation (formerly Lower Lufeng Series) is a Lower Jurassic sedimentary rock formation found in Yunnan, China. It has two units: the lower Dull Purplish Beds/Shawan Member are of Hettangian age, and Dark Red Beds/Zhangjia'ao Member ...

Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is ...

Province in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. Little is known as the remains are fragmentary. The type species is ''T. oehleri''.

Discovery and species

In 1948 and 1949 Father Edgar Oehler, a Catholic priest working for the

Fu Jen Catholic University Fu Jen Catholic University (FJU, FJCU or Fu Jen; or ) is a private Catholic university in Xinzhuang, New Taipei City, Taiwan. The university was founded in 1925 in Beijing at the request of Pope Pius XI and re-established in Taiwan in 1961 at ...

Beijing } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...

, excavated fossils near the village of Da Di in Yunnan. Among them was the jaw bone of a herbivorous dinosaur. In 1965 David Jay Simmons named and described it as the

type species In 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 species that contains the biological type specimen ...

''Tatisaurus oehleri''. The generic name is derived from Da Di, then more usually spelled as "Ta Ti". The specific name honours Oehler. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, FMNH CUP 2088, was found in the Zhangjiawa Beds of the

Lufeng Formation The Lufeng Formation (formerly Lower Lufeng Series) is a Lower Jurassic sedimentary rock formation found in Yunnan, China. It has two units: the lower Dull Purplish Beds/Shawan Member are of Hettangian age, and Dark Red Beds/Zhangjia'ao Member ar ...

, dating from the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...

. It consists of a partial left mandible with teeth. The lower jaw bone fragment is, lacking the tip, six centimetres long. The teeth are eroded. It is the only specimen known of the species. Simmons assigned ''Tatisaurus'' to the Hypsilophodontidae, though this group was seen by him as an

evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Definition An evolutionary grade is a group of ...

of "primitive" Ornithopoda, ancestral to several ornithischian groups. He felt that ''Tatisaurus affinities were with ''

Scelidosaurus ''Scelidosaurus'' (; with the intended meaning of "limb lizard", from Greek / meaning 'rib of beef' and ''sauros''/ meaning 'lizard')Liddell & Scott (1980). Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. is a gen ...

'' or the

Ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...

. Later, in 1990, the specimen was reviewed by

Dong Zhiming Dong Zhiming (Chinese: 董枝明, Pinyin: ''Dǒng Zhimíng''; born January 1937) is a Chinese vertebrate paleontologist formerly employed at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. He began working at the ...

, who noted it had similarities with ''

Huayangosaurus ''Huayangosaurus'' is a genus of stegosaurian dinosaur from the Middle Jurassic of China. The name derives from "Huayang" (華陽), an alternate name for Sichuan (the province where it was discovered), and "saurus", meaning "lizard". It lived ...

''. He placed the two genera in the same subfamily, the Huayangosaurinae, within the

Stegosauria Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe, ...

. Later still, in 1996, Spencer Lucas reclassified ''Tatisaurus oehleri'' as a species of ''Scelidosaurus'', ''S. oehleri'', in order to use ''Scelidosaurus'' for a

biochron A biochron (from the Greek ''bios'', life; and ''khronos'', time) is the length of time represented by a biostratigraphic zone. Biochrons are named after characteristic fossil organisms or taxa In biology, a taxon (back-formation from ''taxon ...

. In 2007, David B. Norman and colleagues regarded this as unfounded. They instead found ''Tatisaurus'' to be a

dubious Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty ...

basal

thyreophora Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. Thyreophorans are characterized by the presence of body ...

n, showing a single thyreophorean

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

; a ventrally deflected mesial end of the

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

. If considered a thyreophoran, it would be one of the oldest known members of the group. In 2019 a study concluded that ''

Bienosaurus ''Bienosaurus'' (meaning "Bien's lizard") is a genus of thyreophoran dinosaur from the Lower Jurassic (probably Sinemurian) Lower Lufeng Formation in Yunnan Province in China. Discovery and species In 1938, Bian Meinian, known in the W ...

'' was a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'', possibly identical to ''Tatisaurus'' from the same formation.Raven, T.J., Barrett, P.M., Xu, X., and Maidment, S.C.R. (2019). "A reassessment of the purported ankylosaurian dinosaur ''Bienosaurus lufengensis'' from the Lower Lufeng Formation of Yunnan, China". ''Acta Palaeontologica Polonica'' 64

References

Thyreophorans Ornithischian genera Early Jurassic dinosaurs of Asia Paleontology in Yunnan Nomina dubia Fossil taxa described in 1965 {{ornithischian-stub