''Hylaeochampsa'' is an extinct

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 ...

eusuchia Eusuchia is a clade of crocodylomorphs that first appeared in the Early Cretaceous with '' Hylaeochampsa''. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades ...

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cro ...

s. It is known only from a partial skull recovered from

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is precede ...

-age rocks of the

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...

Vectis Formation The Vectis Formation is a geological formation on the Isle of Wight and Swanage, England whose strata were formed in the lowermost Aptian, approximately 125 million years ago."Magnetostratigraphy of the Lower Cretaceous Vectis Formation (Wealden ...

( Wealden Group) of the

Isle of Wight The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...

. This skull, BMNH R 177, is short and wide, with a eusuchian-like

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...

and inferred enlarged posterior teeth that would have been suitable for crushing.Owen, R. (1874). Monograph on the fossil Reptilia of the Wealden and Purbeck formations. Supplement no. V. Dinosauria (''

Iguanodon ''Iguanodon'' ( ; meaning ' iguana-tooth'), named in 1825, is a genus of iguanodontian dinosaur. While many species have been classified in the genus ''Iguanodon'', dating from the late Jurassic Period to the early Cretaceous Period of Asia, ...

''). ealden and Purbeck. ''The Palaeontographical Society, London'' 1873:1-18 ''Hylaochampsa'' was described by Richard Owen in 1874, with ''H. vectiana'' as 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 ...

. It may be the same genus as the slightly older '' Heterosuchus'', inferred to have been of similar

evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Definition An evolutionary grade is a group of sp ...

, but there is no overlapping material as ''Heterosuchus'' is known only from

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e. If the two could be shown to be synonyms, ''Hylaeochampsa'' would have priority because it is the older name. ''Hylaeochampsa'' is the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

of the family

Hylaeochampsidae Hylaeochampsidae is an extinct family of basal eusuchian crocodylomorphs thought to be closely related to the order Crocodylia. Classification Hylaeochampsidae was first constructed by Charles William Andrews in 1913 to include just one membe ...

, which also includes '' Iharkutosuchus'' from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the ...

. James Clark and Mark Norell positioned it as the sister group to

Crocodylia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest living ...

. ''Hylaeochampsa'' is currently the oldest known unambiguous eusuchian. The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

below results from a 2011 Buscalioni ''et al.''

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

study:

References

Early Cretaceous reptiles of Europe Early Cretaceous crocodylomorphs of Europe Neosuchians Prehistoric pseudosuchian genera {{paleo-archosaur-stub