Cordicephalus gracilis is the only species in the extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Cordicephalus, a genus of prehistoric frogs. Fossils of C. gracilis were found in a lacustrine

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 deposit in Makhtesh Ramon

Makhtesh Ramon

Makhtesh Ramon is a geological feature of Israel's Negev desert. Located at the peak of Mount Negev, some 85 km south of the city of Beersheba, the landform is not actually an impact crater from a meteor, but rather is the world's largest makhtesh. The crater is 40 km long, 2-10 km wide and 500...

 called "Amphibian Hill" and it is believed they lived during the Lower Cretaceous.

When first described by Eviatar Nevo of the University of Haifa

University of Haifa

The University of Haifa is a university in Haifa, Israel.The University of Haifa was founded in 1963 by Haifa mayor Abba Hushi, to operate under the academic auspices of the Hebrew University of Jerusalem....

 (in 1968) the genus Cordicephalus was thought to contain two species, C. gracilis and C. longicostatus. Since then it was redescribed and it was determined that C. gracilis was the only species in the genus.

Etymology

The genus' name derives from the Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 cordi (cor meaning heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

) and cephalus (meaning head). The name comes from the heart-like shape of its skull. The species name, gracilis, comes from the Latin for slender.

Description

Like its close relatives, C. gracilis was fairly small, about 30 millimetres (1.2 in) in length. It had a flat skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 which was almost as wide as it was long, features usually found in aquatic animals. Other features that support that view that C. gracilis had a mainly aquatic lifestyle is its short axial column as well as large foot bones

Metatarsus

The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...

which may imply extensive webbing.