''Genyodectes'' ("jaw bite", from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

words ''genys'' ("jaw") and ''dektes'' ("bite")) 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 ...

ceratosaur Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earliest ...

ian

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur from the Lower

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

(

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

) of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. 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 ...

material (MLP 26–39, Museo de La Plata,

La Plata La Plata () is the capital city of Buenos Aires province, Argentina. According to the 2022 Argentina census, census, the La Plata Partido, Partido has a population of 772,618 and its metropolitan area, the Greater La Plata, has 938,287 inhabit ...

, Argentina) was collected from the

Cerro Barcino Formation The Cerro Barcino Formation (also known as the Gorro Frigio Formation) is a geological Formation (geology), formation in South America whose strata span the Early Cretaceous to the earliest Late Cretaceous. The top age for the formation has been e ...

, Cañadón Grande, Departamento Paso de Indios in the

Chubut Province Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and consists of an incomplete snout, including the

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 ...

e, portions of both

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

s, the right and 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 ...

, many

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

, a fragment of the left

splenial The splenial is a small bone in the lower jaw of reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology ...

, and parts of the supradentaries. These elements are generally poorly preserved and some are in articulation. The premaxilla of ''Genyodectes'' possesses relatively large and protruding teeth, similar to those of ''

Ceratosaurus ''Ceratosaurus'' (from Greek 'horn' and 'lizard') is a genus of carnivorous theropod dinosaur that lived in the Late Jurassic period (Kimmeridgian to Tithonian ages). The genus was first described in 1884 by American paleontologist Othni ...

''. The specific name, ''serus'', means "late". In 2016 it was estimated to be in length and in weight.

Taxonomy and phylogeny

The

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

has long been considered 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 ...

, owing to its fragmentary nature and some doubt as to its precise geographic and

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

origins (see Tykoski et Rowe, 2004, p. 50).Tykoski, R.S., and Rowe, T. (2004). Ceratosauria. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (Eds.). ''The Dinosauria'' (2nd edition). University of California Press:Berkeley. . However, a recent redescription of the type material by Rauhut (2004) has shed some light on these questions and seems to establish the

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

validity of ''Genyodectes serus'', the only species referred to the genus.Rauhut, O.W.M. (2004). Provenance and anatomy of ''Genyodectes serus'', a large-toothed ceratosaur (Dinosauria: Theropoda) from Patagonia. ''Journal of Vertebrate Paleontology'' 24(4):894-902. English

paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

Sir Arthur S. Woodward described ''Genyodectes'' in 1901,Woodward A. S. 1901. On some extinct reptiles from Patagonia, of the genera ''

Meiolania ''Meiolania'' is an extinct genus of meiolaniid stem-turtle native to Australasia throughout much of the Cenozoic. ''Meiolania'' was a large turtle, with the shell alone ranging from in length. Four species are currently recognized, although the ...

'', ''

Dinilysia ''Dinilysia'' (meaning "terrible ilysia") is an extinct genus of snake from the Late Cretaceous (Coniacian) of South America. ''Dinilysia'' was a relatively large ambush predator, measuring approximately long. The skull morphology of ''Dinilysia ...

'', and ''Genyodectes''. ''Proceedings of the Zoological Society of London'' 1901:169-184. and, after ''

Loncosaurus ''Loncosaurus'' (meaning uncertain; either Araucanian "chief" or Greek "lance" "lizard"Norman, D.B., and Weishampel, D.B. 1990. Iguanodontidae and related ornithopods. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). ''The Dinosauria ...

'' ( Ameghino, 1899; ''nomen dubium''), Ameghino, F. (1899). Nota preliminar sobre el ''

Loncosaurus argentinus ''Loncosaurus'' (meaning uncertain; either Araucanian "chief" or Greek "lance" "lizard"Norman, D.B., and Weishampel, D.B. 1990. Iguanodontidae and related ornithopods. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). ''The Dinosauria ...

'', un representante de la familia de los Megalosauridae en la Republica Argentina. ''Anales de la Sociedad Cientifica Argentina'' 47:61-62. it is the second non- avian dinosaur described from the South American

continent A continent is any of several large geographical regions. Continents are generally identified by convention (norm), convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as ...

, and it remained the most completely known South American theropod until the 1970s. Over the last decade, the holotype has been variously referred to as a

megalosaurid Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs. They were a relatively ...

, a

tyrannosaurid Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera ...

, Theropoda ''

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 a possible

abelisaurid Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are foun ...

(perhaps even a

senior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of ''

Abelisaurus ''Abelisaurus'' (; "Abel's lizard") is a genus of predatory abelisaurid theropod dinosaur alive during the Late Cretaceous Period (geology), Period (Campanian) of what is now South America. It was a bipedal carnivore that probably reached about ...

''). However, the recent removal of the holotype from the "artificial matrix" in which it had long been displayed has permitted a reevaluation of the specimen. Rauhut (2004, p. 900) concluded that the specimen lacks important abelisaurid and tyrannosaurid

synapomorphies 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 ...

, but found many neoceratosaurian traits. This would seem to imply ''Genyodectes'' was closer to ''Ceratosaurus'' than the more derived abelisaurs (that also descended from animals like ''Ceratosaurus''). Also, by studying historical records and preservation of the bones, Rauhut (2004, p. 894) concluded that the specimen was likely collected from the Cerro Castaño Member of the

(

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

Diagnosis

Rauhut diagnoses ''Genyodectes serus'' as follows:Rauhut, O.W.M. (2004) Provenance and anatomy of ''Genyodectes serus'', a large-toothed ceratosaur (Dinosauria: Theropoda) from Patagonia. Journal of Vertebrate Paleontology 24(4):895-895 "Differs from all theropods with the possible exception of ''

'' in that the premaxillary teeth are arranged in an overlapping ''en-echelon'' pattern and the longest maxillary tooth crowns are longer apicobasally than the minimal dorsoventral depth of the mandible. Differs from ''Ceratosaurus'' in the presence of four, as opposed to three, premaxillary teeth."

References

{{Taxonbar, from=Q134643 Ceratosauria Dinosaur genera Aptian dinosaurs Cerro Barcino Formation Fossil taxa described in 1901 Taxa named by Arthur Smith Woodward Dinosaurs of Argentina