''Tatisaurus'' is a

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 ornithischian

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

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 143.1 Mya. ...

from the Lower Lufeng Formation in

Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

Province in

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. 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 education, private Catholic university in Xinzhuang District, Xinzhuang, New Taipei City, Taiwan. The university was founded in 1925 in Beijing at the request of Pope Pius XI and ...

Beijing Beijing, Chinese postal romanization, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's List of national capitals by population, most populous national capital city as well as ...

, 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 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 ...

''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 (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

, FMNH CUP 2088, was found in the Zhangjiawa Beds of the Lufeng Formation, dating from the

Sinemurian In the geologic timescale, the Sinemurian is an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic epoch (geology), Epoch or series (stratigraphy), Series. It spans the time between 199.5 ±0.3 annu ...

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

Ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the clade 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 language, Chinese: 董枝明, Pinyin: ''Dǒng Zhimíng''; January 1937 – 20 October 2024) was a Chinese vertebrate paleontologist formerly employed at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) ...

, who noted it had similarities with '' Huayangosaurus''. He placed the two genera in the same subfamily, the Huayangosaurinae, within the

Stegosauria Stegosauria is a group of Herbivore, herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous Period (geology), periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere (North America, Europe a ...

. Later still, in 1996, Spencer Lucas reclassified ''Tatisaurus oehleri'' as a species of ''Scelidosaurus'', ''S. oehleri'', in order to use ''Scelidosaurus'' for a biochron. In 2007, David B. Norman and colleagues regarded this as unfounded. They instead found ''Tatisaurus'' to be a dubious basal thyreophoran, showing a single thyreophorean

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...

; a ventrally deflected mesial end of the dentary. If considered a thyreophoran, it would be one of the oldest known members of the group. In 2019 a study concluded that '' Bienosaurus'' 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 ...

'', 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

{{Taxonbar, from=Q1955108 Thyreophora Dinosaur genera Sinemurian dinosaurs Lufeng Formation Fossil taxa described in 1965 Dinosaurs of China