Acynodon is an 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...

 of alligatoroid

Alligatoroidea

Alligatoroidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, it is defined as Alligator mississippiensis and all crocodylians more closely related to A. mississippiensis than to either Crocodylus niloticus or Gavialis gangeticus ....

 crocodilia

Crocodilia

Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...

n. When first described it was placed within the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Alligatoridae

Alligatoridae

Alligatoridae is a family of crocodylians that includes alligators and caimans.- True alligators :Alligators proper occur in the fluvial deposits of the age of the Upper Chalk in Europe, where they did not die out until the Pliocene age. The true alligators are now restricted to two species, A...

, but has since been reclassified as a globidonta

Globidonta

Globidonta is a clade of alligatoroids that includes alligators, caimans, and closely related extinct forms. It is defined as a stem-based clade including Alligator mississippiensis and all forms more closely related to it than to Diplocynodon...

n. It is the oldest and most primitive globidontan known to date, with fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s being found from France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Spain

Spain

Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

, Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, and Slovenia

Slovenia

Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...

. Acynodon first appeared during the early Campanian

Campanian

The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

 stage of the Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 and went extinct during the Cretaceous–Tertiary extinction event at the K–T boundary

K–T boundary

The K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...

. The skull of Acynodon is extremely brevirostrine; it had a very short and broad snout compared to other known alligatorids. Its dentition was quite derived

Derived

In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...

, with enlarged molariform

Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

 teeth and a lack of maxilla

Maxilla

The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

ry and dentary caniniform teeth, presumably an adaptation to feed on slow prey with hard shells. The paravertebral osteoderm

Osteoderm

Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...

s of Acynodon were distinctively double-keeled.