Terrestrisuchus

Terrestrisuchus

Terrestrisuchus Fossil range: Late Triassic
Scientific classification
Suborder:	Sphenosuchia
Family:	Saltoposuchidae
Genus:	Terrestrisuchus
Species:	T. gracilis

Terrestrisuchus ('land crocodile') is an extinct genus of early crocodylomorph that was about 50 cm (1 ft 8 in) long. Fossils have been found in Wales and date from the Late Triassic.

Description

Terrestrisuchus was a small, thin, lizard-like creature with long legs, bearing little to no resemblance to modern crocodiles, which are its distant relatives. The shape of the legs suggests that it was able to run fast. Its tail was particularly long, about twice the length of the head and body combined, and may have been used as a balance allowing the animal to rear up and run on its hind legs alone for brief periods.

The legs were positioned directly beneath the body, meaning ancestral crocodiles such as Terrestrisuchus were cursorial and thus, their legs worked as pairs for galloping. Pseudo-galloping can be seen in modern crocodiles as they are known to use paired walking in rare but speed-dependent situations. Fossil evidence also shows that they were digitigrade, supporting their weight on only digits, or fingers.

History of discovery

The first fossils of Terrestrisuchus were discovered by Professor K. A. Kermack and Dr. P. L. Robinson in the spring of 1952, recovered from the Pant-y-ffynon Quarry located near Cowbridhe, Glamorgan in South Wales. Their finds were presented by Kermack to the Linnean Society of London on October 8, 1953, and was recognised belonging to a "primitive crocodile or crocodile ancestor". No osteoderms had been identified yet at the time, which Kermack regarded as representing a "missing link" between modern crocodilians and the Triassic "thecodonts". The fossils included several well-preserved articulated partial skeletons and various isolated bones. Kermack refrained from naming the animal or nominating a type specimen, as preparation of the fossils was still ongoing. The specimens were eventually named and thoroughly described by P. J. Crush in 1984, with the generic name Terrestrisuchus chosen to emphasise the terrestrial lifestyle of this crocodylomorph, and the specific name from the Latin gracilis for its light, graceful build.

The Pant-y-ffynnon Quarry is composed mostly of Carboniferous limestone, but the fossils of Terrestrisuchus were recovered from Triassic sedimentary rocks that were deposited within fissures in the limestone (such as sandstones and marls). The age of the deposits has been historically debated, with older literature suggesting a Carnian to Norian age. However, palynological data has been used to determine a younger Rhaetian age, close to the very end of the Triassic. This estimate has been corroborated by Rhaetian index fossils such as conchostracans and geomorphological data.

Additional material attributed to Terrestrisuchus has been discovered in other Late Triassic fissure deposits in South Wales and Bristol, including the Ruthin Quarry in Wales and the Tytherington and Cromhall quarries near Bristol, as well as a possible specimen from Durdham Down. The fossils of Terrestrisuchus were originally housed at University College, London before being transferred to the Natural History Museum in London where they are currently stored.