''Euclastes'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 ...

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...

s that survived the Cretaceous–Paleogene mass extinction. The genus was first named by

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested ...

in 1867, and contains three species. ''E. hutchisoni'', was named in 2003 but has since been reassigned to the genus ''

Pacifichelys ''Pacifichelys'' is an extinct genus of sea turtle from the Miocene, Middle Miocene of Peru (Pisco Formation) and California (Temblor Formation).Mexichelys coahuilaensis'' in 2010.

Description

Unlike the sea turtles ''

Toxochelys ''Toxochelys'' () is an extinct genus of marine turtle from the Late Cretaceous period. It is the most commonly found fossilized turtle species in the Smoky Hill Chalk, in western Kansas. Description ''Toxochelys'' was about 2 m (6 ft ...

'' and ''

Eochelone ''Eochelone'' is an extinct genus of sea turtle from the late Eocene. It was first named by Dollo in 1903. Its type species is ''E. brabantica''. References Professor Paul's Guide to Reptiles''Eochelone''in the Paleobiology Database The Paleo ...

'', ''Euclastes'' has a

secondary palate The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medi ...

. However, the secondary palate of ''Euclastes'' is not as extensive as it is in ''

Ctenochelys ''Ctenochelys'' is an extinct genus of marine turtle (Cryptodira, Pancheloniidae), which existed during the Cretaceous period, and lived in the shallow waters of the Western Interior Seaway. Its fossils have been found in the Ripley Formation a ...

'' and ''

Angolachelys ''Angolachelys'' is an extinct genus of African eucryptodiran turtle which existed in Angola during the Turonian stage of the Late Cretaceous. The type species is ''Angolachelys mbaxi''. The type MGUAN-PA includes skull, jaw, and postcranial frag ...

''. The genus can be distinguished by later sea turtles based on its broad, low skull; broad, flat palate; wide, flat

dentary bone 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 ...

with an elongated

symphysis A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together ...

; and low tomial ridge on the beak. The widened palate and dentaries give ''Eochelone'' wide, flat jaws suitable for crushing hard-shelled organisms.

Classification

Species

* †''E. acutirostris'' * †''E. platyops'' * †''E. wielandi''

Phylogeny

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 d ...

based on Lynch and Parham (2003) and Parham and Pyenson (2010):

Distribution

Fossils of ''Euclastes'' have been found in: ;Maastrichtian * Bentiaba, AngolaMateus, O., M. J. Polcyn, L. L. Jacobs, R. Arujo, A. S. Schulp, J. Marinheiro, B. Pereira and D. Vineyard. 2012. Cretaceous amniotes from Angola: dinosaurs, pterosaurs, mosasaurs, plesiosaurs, turtles. Actas de V Jornadas Internacionales sobre Paleontologia de Dinosaurios y su Entorno, Salas de los Infantes, Burgos 71-105 *

Quiriquina Formation The Quiriquina Formation is a geological formation in Chile whose strata date back to 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. ...

, Chile * Hornerstown and

Navesink Formation The Navesink Formation is a 66 to 70 mya greensand glauconitic marl and sand geological formation in New Jersey. It is known for its Cretaceous period fossil shell beds and dinosaur bones. Description The Navesink Formation, named after Navesin ...

s, New Jersey ;Paleocene * Jagüel and Roca Formations, Argentina * Aquia and Brightseat Formations, Maryland * Sidi Chennane and Couche 2 Formation, Morocco ;Eocene * Parkers Ferry Formation, South Carolina

References

External links

www.scistp.org
{{Taxonbar, from=Q5406057 Chelonioidea Prehistoric turtle genera Cretaceous–Paleogene boundary Maastrichtian genus first appearances Eocene genus extinctions Cretaceous turtles Paleocene turtles Eocene turtles Late Cretaceous reptiles of Africa Fossils of Angola Late Cretaceous reptiles of North America Cretaceous United States Fossils of the United States Late Cretaceous reptiles of South America Cretaceous Chile Fossils of Chile Paleogene reptiles of Africa Fossils of Morocco Paleogene reptiles of North America Paleogene United States Paleogene reptiles of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 1867 Taxa named by Edward Drinker Cope