''Protognathosaurus'' (meaning "early jaw lizard") 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 herbivorous

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

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

. It was a

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

found at

Dashanpu The Shaximiao Formation () is a Middle Jurassic, 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 ...

Sichuan Sichuan is a province in Southwestern China, occupying the Sichuan Basin and Tibetan Plateau—between the Jinsha River to the west, the Daba Mountains to the north, and the Yunnan–Guizhou Plateau to the south. Its capital city is Cheng ...

in what is present-day

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 ...

History

In 1988 Zhang Yihun named and described 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 ...

''Protognathus oxyodon''. The generic name was derived from Greek πρῶτος, ''protos'', "first", and γνάθος, ''gnathos'', "jaw". The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

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 fa ...

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

, ''Protognathus'' (Basilewsky, 1950) which is considered a synonym of ''

Pseudognathaphanus ''Pseudognathaphanus'' is a genus in the beetle family Carabidae. There are about 10 described species in ''Pseudognathaphanus''. Species These 10 species belong to the genus ''Pseudognathaphanus'': * '' Pseudognathaphanus dekkanus'' Andrewes, 1 ...

'' (Schauberger, 1932). The species was therefore renamed into the ''

combinatio nova In biological taxonomy, a combinatio nova (abbreviated comb. nov. or n. comb.) refers to the formal renaming of an organism's scientific name when it is transferred to a different genus, reclassified within a different species, or its taxonomic ...

'' ''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 (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 ...

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 (geology), age and stage (stratigraphy), stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 annum, Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds ...

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 165.3 ± 1.1 Ma (million years ago) and 161.5 ± 1.0 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 jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

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 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 ...

''.

References

Sauropoda Dinosaur genera Callovian dinosaurs Shaximiao Formation Taxa named by George Olshevsky Fossil taxa described in 1991 Dinosaurs of China {{Sauropodomorph-stub