''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
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of small-bodied
rhomaleosaurid
Rhomaleosauridae is a family of plesiosaurs from the Earliest Jurassic to the latest Middle Jurassic ( Hettangian to Callovian stages) of Europe, North America, South America and possibly Asia. Most rhomaleosaurids are known from England, man ...
known from the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
(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
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
specimen
NHMUK 14550, which consists of the posterior portion of a
skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
, 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 sk ...
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
( en, All The People of Somerset)
, locator_map =
, coordinates =
, region = South West England
, established_date = Ancient
, established_by =
, preceded_by =
, origin =
, lord_lieutenant_office =Lord Lieutenant of Somerset
, lord_ ...
, 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
The Lias Group or Lias is a lithostratigraphic unit (a sequence of rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, sha ...
. 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
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
–
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 (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
Boundary. Plesiosaurs fossils which were discovered at Street represent the earliest known occurrence of the
Plesiosauria
The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Plesiosaurs first appeare ...
. 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
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
are about 18–19; this low number represents its autapomorphy
In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...
.[
]
Classification
A phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analysis performed by Benson ''et al.'' (2012) found it to be a basal rhomaleosaurid. The cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
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 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
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
is ''Avalonnectes arturi''. The generic name is derived from Avalon
Avalon (; la, Insula Avallonis; cy, Ynys Afallon, Ynys Afallach; kw, Enys Avalow; literally meaning "the isle of fruit r appletrees"; also written ''Avallon'' or ''Avilion'' among various other spellings) is a mythical island featured in the ...
, 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
Glastonbury (, ) is a town and civil parish in Somerset, England, situated at a dry point on the low-lying Somerset Levels, south of Bristol. The town, which is in the Mendip district, had a population of 8,932 in the 2011 census. Glastonbury ...
, near Street, and from Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
''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
Arthur is a common male given name of Brythonic origin. Its popularity derives from it being the name of the legendary hero King Arthur. The etymology is disputed. It may derive from the Celtic ''Artos'' meaning “Bear”. Another theory, more ...
(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
This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles that flourished duri ...
* List of plesiosaur genera
This list of plesiosaurs is a comprehensive listing of all genera that have ever been included in the order Plesiosauria, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered inv ...
References
{{Taxonbar, from=Q367526
Early Jurassic plesiosaurs of Europe
Fossil taxa described in 2012
Fossils of Great Britain
Rhomaleosaurids
Sauropterygian genera