Avalonnectes

Avalonnectes Temporal range: Early Jurassic,
Holotype of Avalonnectes arturi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Family:	†Rhomaleosauridae
Genus:	†Avalonnectes Benson, Evans & Druckenmiller, 2012
Type species
†Avalonnectes arturi Benson, Evans & Druckenmiller, 2012

Avalonnectes is an extinct genus of small-bodied rhomaleosaurid known from the Early Jurassic period (most likely earliest Hettangian stage) of the United Kingdom. It contains a single species, A. arturi.

Discovery

Avalonnectes is known from the holotype specimen NHMUK 14550, the posterior portion of the skull, and a nearly complete, three-dimensionally preserved and articulated postcranial skeleton. Another partial postcranial skeleton which was referred to the it is AGT uncatalogued. Both specimens were collected at Street, of Somerset, from the Pre-Planorbis beds of the Blue Lias Formation of the Lower Lias Group. These beds likely occur below the first occurrence of the ammonite Psiloceras planorbis. Thus, they probably fall within the earliest Hettangian P. tilmanni Chronozone, which is about 199.6-198 million years old, immediately following the Triassic–Jurassic Boundary. Plesiosaurs fossils which were discovered at Street represent the earliest known occurrence of the Plesiosauria. Hence, Avalonnectes is one of the oldest plesiosaurs to date.

Description

Avalonnectes is a small-bodied rhomaleosaurid with 18–19 dorsal vertebrae. This low number represents its autapomorphy. A phylogenetic analysis performed by Benson et al. (2012) found it to be a basal rhomaleosaurid. The cladogram below shows Avalonnectes phylogenetic position among other plesiosaurs following Benson et al. (2012).

Plesiosauria	Neoplesiosauria  Pliosauridae Plesiosauroidea  Rhomaleosauridae  Stratesaurus taylori Macroplata tenuiceps Avalonnectes arturi Eurycleidus arcuatus Meyerasaurus victor Maresaurus coccai "Rhomaleosaurus" megacephalus Archaeonectrus rostratus Rhomaleosaurus cramptoni Rhomaleosaurus thorntoni Rhomaleosaurus zetlandicus

Etymology

Avalonnectes was first described and named by Roger B. J. Benson, Mark Evans and Patrick S. Druckenmiller in 2012 and the type species is Avalonnectes arturi. The generic name is derived from Avalon, an island from the legend of King Arthur, often identified with Glastonbury, near Street, and from Greek nectes, meaning "swimmer". The specific name honors the paleontologist Arthur Cruickshank (1932–2011), who with M. A. Taylor initiated the restudy of British Lower Jurassic plesiosaurians in the 1990s. It is also a reference to the legendary King Arthur of British folklore.