''Protognathosaurus'' (meaning "early jaw lizard") is a

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 nom ...

of herbivorous

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 Middle Jurassic. It was a sauropod found at

Dashanpu The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around th ...

Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of the ...

in what is present-day China. In 1988 Zhang Yihun named and described 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 specime ...

''Protognathus oxyodon''. The generic name was derived from Greek πρῶτος, ''protos'', "first", and γνάθος, ''gnathos'', "jaw". The specific name is derived from Greek ὀξύς, ''oxys'', "sharp", and ὀδών, ''odon'', "tooth". However, the generic name was preoccupied, already in use, by a genus of

carabid Ground beetles are a large, cosmopolitan family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it is one of the 10 most species-rich animal fam ...

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

, ''Protognathus'' (Basilewsky, 1950) which is considered a synonym of '' Pseudognathaphanus'' (Schauberger, 1932). The species was therefore renamed into the '' combinatio nova'' ''Protognathosaurus oxyodon'' by George Olshevsky in 1991.Olshevsky, G., 1991, ''A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. Mesozoic Meanderings 2'', iv + 196 pp ''Protognathosaurus'' is known only from a fragmentary lower jaw,

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 sever ...

CV 00732 (= ChM V732) found in a layer of the

Shaximiao Formation The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around the ...

dating from the

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. Str ...

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

. The fragment consists of the front left

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 teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

and shows eighteen tooth positions, some still containing sharp replacement teeth, after which the genus was named. Most researchers consider ''Protognathosaurus'' to be a '' nomen dubium''.

References

Middle Jurassic dinosaurs of Asia Sauropods Fossil taxa described in 1991 Fossil taxa described in 1988 Taxa named by George Olshevsky Paleontology in Sichuan Nomina dubia {{Sauropodomorph-stub