| Avalonnectes | |
|---|---|
 | |
| Holotype ofAvalonnectes arturi | |
Scientific classification | |
| 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 anextinctgenus of small-bodiedrhomaleosaurid known from theEarly Jurassicperiod (most likely earliestHettangian stage) of the United Kingdom. It contains a single species,A. arturi.[1]
Avalonnectes is known from theholotype specimenNHMUK 14550, which consists of the posterior portion of askull, and a nearly complete, three-dimensionally preserved and articulatedpostcranialskeleton. Another partial postcranial skeleton which was referred to it isAGT uncatalogued. Both specimens were collected atStreet, ofSomerset, from the Pre-Planorbis beds of theBlue Lias Formation of theLower Lias Group. These beds likely occur below the first occurrence of the ammonitePsiloceras planorbis. Thus, they probably fall within the earliest HettangianP. tilmanni Chronozone, which is about 199.6-198 million years old, immediately following theTriassic–Jurassic Boundary. Plesiosaurs fossils which were discovered at Street represent the earliest known occurrence of thePlesiosauria. Hence,Avalonnectes is one of the oldest plesiosaurs to date.[1]
Avalonnectes is a small-bodied rhomaleosaurid, with a trunck length of 73.5 cm (2 ft 4.9 in) and a neck length of more than 67 cm (2 ft 2 in). The number ofdorsal vertebrae are about 18–19; this low number represents itsautapomorphy.[1]
Aphylogenetic analysis performed by Bensonet al. (2012) found it to be abasal rhomaleosaurid. Thecladogram below showsAvalonnectes phylogenetic position among other plesiosaurs following Bensonet al. (2012).[1]
Avalonnectes was first described and named byRoger B. J. Benson, Mark Evans andPatrick S. Druckenmiller in2012 and thetype species isAvalonnectes arturi. Thegeneric name is derived fromAvalon, an island from the legend ofKing Arthur, often identified withGlastonbury, near Street, and fromGreeknectes, meaning "swimmer". Thespecific name honors the paleontologistArthur 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.[1]
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