Dyrosauridae

Dyrosauridae is a family of extinct neosuchian crocodyliforms that lived from the Campanian to the Eocene. Dyrosaurid fossils are globally distributed, having been found in Africa, Asia, Europe, North America and South America. Over a dozen species are currently known, varying greatly in overall size and cranial shape, though typically with an elongate gharial-like snout. A majority were aquatic, some terrestrial and others fully marine with species inhabiting both freshwater and marine environments. Ocean-dwelling dyrosaurids were among the few marine reptiles to survive the Cretaceous–Paleogene extinction event.

Dyrosaurids were medium-to-large sized animals, with many of them reaching lengths past 6 metres (20 ft), Based on bone tissue evidence, it has been hypothesized that they were slow-growing near-shore marine animals with interlocking closed jaws, with a considerable ability to move the head upwards and downwards, able to swim as well as walk on land. External nostrils at the posterior end of its snout and an internal naris in its pterygoid indicated a habit of hunting while swimming with the top of the head above the water, enabling it to breathe while stalking prey.

Overview

Jouve et al. (2005) diagnose Dyrosauridae as a clade based on the following seven synapomorphies or shared characters:

Posteromedial wing of the retroarticular process dorsally situated ventrally on the retroarticular process

Occipital tuberosities small

Exoccipital participates largely to the occipital condyle

Supratemporal fenestra anteroposteriorly strongly elongated

Symphysis about as wide as high

Quadratojugal participates largely to the cranial condyle for articulation with the jaw

4 premaxillary teeth

Dyrosaurids are known to have a very characteristic skull shape with a long and thin gharial-like snout that is approximately 68% of the total skull length. The most anterior part of the skull and snout is the external naris followed posteriorly by two premaxillae bones until they reach two maxillae bones separated by a single nasal bone.