''Genyodectes'' ("jaw bite", from the Greek words ''genys'' ("jaw") and ''dektes'' ("bite")) 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 ...

of ceratosaurian theropod dinosaur from the Lower

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

(

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

) of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. 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 ...

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

La Plata La Plata () is the capital city of Buenos Aires Province, Argentina. According to the , it has a population of 654,324 and its metropolitan area, the Greater La Plata, has 787,294 inhabitants. It is located 9 kilometers (6 miles) inland from th ...

, Argentina) was collected from the Cerro Barcino Formation, Cañadón Grande, Departamento Paso de Indios in the

Chubut Province Chubut ( es, Provincia del Chubut, ; cy, Talaith Chubut) is a province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa Cruz Province), the Andes ra ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

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 mammal has b ...

e, portions of both

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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 t ...

s, the right and left dentary, 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, 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''. The specific name, ''serus'', means "late". In 2016 it was estimated to be 6.25 meters in length and 790 kg in weight.

Taxonomy and phylogeny

The

taxon In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...

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 s ...

, owing to its fragmentary nature and some doubt as to its precise geographic and stratigraphic 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 Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

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 palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

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

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 ''Dinilys ...

'', 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 Avian may refer to: *Birds or Aves, winged animals *Avian (given name) (russian: Авиа́н, link=no), a male forename Aviation *Avro Avian, a series of light aircraft made by Avro in the 1920s and 1930s *Avian Limited, a hang glider manufacture ...

dinosaur described from the South American

continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...

, 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 relative ...

, a

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

, Theropoda '' incertae sedis'', and a possible abelisaurid (perhaps even a senior synonym of ''

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

''). 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 have ...

, 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 Cerro Barcino Formation (

- Albian).

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 '' Ceratosaurus'' 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 Ceratosaurs Aptian life Early Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Cerro Barcino Formation Fossil taxa described in 1901 Taxa named by Arthur Smith Woodward