''Avalonnectes'' is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus of small-bodied
rhomaleosaurid known from the
Early Jurassic period (most likely earliest
Hettangian
The Hettangian is the earliest age and lowest stage of the Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (My ...
stage) of the United Kingdom. It contains a single species, ''A. arturi''.
Discovery
''Avalonnectes'' is known from the
holotype specimen
NHMUK
The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum (Lo ...
14550, which consists of the posterior portion of a
skull, and a nearly complete, three-dimensionally preserved and articulated
postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated s ...
l
skeleton
A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...
. Another partial postcranial skeleton which was referred to it is
AGT uncatalogued. Both specimens were collected at
Street
A street is a public thoroughfare in a built environment. It is a public parcel of land adjoining buildings in an urban context, on which people may freely assemble, interact, and move about. A street can be as simple as a level patch of dirt, ...
, of
Somerset, from the Pre-''Planorbis'' beds of the
Blue Lias Formation
The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassi ...
of the
Lower Lias Group. These beds likely occur below the first occurrence of the ammonite ''
Psiloceras planorbis
''Psiloceras'' is an extinct genus of ammonite. ''Psiloceras'' is among the earliest known Jurassic ammonites, and the appearance of the earliest ''Psiloceras'' species form the definition for the base of the Jurassic. Unlike most earlier ammonit ...
''. 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 a truck length of and a neck length of more than . The number of dorsal vertebrae are about 18–19; this low number represents its autapomorphy.[
]
Classification
A phylogenetic analysis performed by Benson ''et al.'' (2012) found it to be a basal
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
rhomaleosaurid. The cladogram below shows ''Avalonnectes'' phylogenetic position among other plesiosaurs following Benson ''et al.'' (2012).[
]
Etymology
''Avalonnectes'' was first described and named by Roger B. J. Benson
Roger is a given name, usually masculine, and a surname. The given name is derived from the Old French personal names ' and '. These names are of Germanic origin, derived from the elements ', ''χrōþi'' ("fame", "renown", "honour") and ', ' ...
, Mark Evans and Patrick S. Druckenmiller Patrick may refer to:
*Patrick (given name), list of people and fictional characters with this name
*Patrick (surname), list of people with this name
People
*Saint Patrick (c. 385–c. 461), Christian saint
* Gilla Pátraic (died 1084), Patrick o ...
in 2012
File:2012 Events Collage V3.png, From left, clockwise: The passenger cruise ship Costa Concordia lies capsized after the Costa Concordia disaster; Damage to Casino Pier in Seaside Heights, New Jersey as a result of Hurricane Sandy; People gather ...
and the type species is ''Avalonnectes arturi''. The generic name is derived from Avalon, an island from the legend of King Arthur
King Arthur ( cy, Brenin Arthur, kw, Arthur Gernow, br, Roue Arzhur) is a legendary king of Britain, and a central figure in the medieval literary tradition known as the Matter of Britain.
In the earliest traditions, Arthur appears as a ...
, often identified with Glastonbury, near Street, and from Greek ''nectes'', meaning "swimmer". The specific name Specific name may refer to:
* in Database management systems, a system-assigned name that is unique within a particular database
In taxonomy, either of these two meanings, each with its own set of rules:
* Specific name (botany), the two-part (bino ...
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.[
]
See also
* Timeline of plesiosaur research
* List of plesiosaur genera
References
{{Taxonbar, from=Q367526
Early Jurassic plesiosaurs of Europe
Fossil taxa described in 2012
Fossils of Great Britain
Rhomaleosaurids
Sauropterygian genera