''Excalibosaurus'' (meaning "

Excalibur Excalibur () is the legendary sword of King Arthur, sometimes also attributed with magical powers or associated with the rightful sovereignty of Britain. It was associated with the Arthurian legend very early on. Excalibur and the Sword in t ...

's lizard") is a monotypic

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of marine prehistoric reptiles (

ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...

s) that lived during the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian an ...

stage (approximately 196.5 ± 2 Ma to 190.8 ± 1.0 Ma (million years ago)) of the

Early Jurassic The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma ...

period in what is now

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

. It is characterized by the extreme elongation of the rostrum, with the lower jaw about three-fourths of the length of the upper jaw, giving the animal a

swordfish Swordfish (''Xiphias gladius''), also known as broadbills in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are a popular sport fish of the billfish category, though elusive. Swordfi ...

-like look. The only known species is ''Excalibosaurus costini''.

History of research

This relatively rare animal is known from two skeletons. 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 seve ...

, discovered in 1984 near a beach on the

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 , lor ...

coast, consists of the skull, forefin, part of the pectoral girdle and some

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...

e and ribs. It has been described in 1986 by Christopher McGowan. The

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

is hosted in the

Bristol City Museum and Art Gallery Bristol Museum & Art Gallery is a large museum and art gallery in Bristol, England. The museum is situated in Clifton, about from the city centre. As part of Bristol Culture it is run by the Bristol City Council with no entrance fee. It holds ...

. The second specimen is an almost complete skeleton collected in the same area in 1996, and was purchased by the Royal Ontario Museum. It was described again by McGowan in 2003.

Description

The holotype specimen has a skull length of , while the largest specimen has a skull length of . It is estimated that this specimen would have belonged to an individual measuring approximately long and weighing . ''Excalibosaurus'' is related to two other genera of ichthyosaurs, '' Leptonectes'' from the

Rhaetian The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest ...

(Late

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 ...

) to the Sinemurian (Early Jurassic) of England and '' Eurhinosaurus'' from the

Toarcian The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarc ...

(Early Jurassic) of

Germany Germany, officially the Federal Republic of Germany (FRG),, is a country in Central Europe. It is the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the sou ...

. The three genera are grouped in the family Leptonectidae and the suborder

Eurhinosauria Leptonectidae is a family of ichthyosaurs Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation ...

. It was once thought that ''Excalibosaurus'' was a junior synonym of ''Eurhinosaurus'', but the description of the 1996 specimen show many morphological differences such as the shape of the forefin (much shorter and broader in ''Excalibosaurus''), the slender shape of the body, that clearly differentiate the two genera.

References

{{Taxonbar , from=Q137451 Early Jurassic ichthyosaurs Ichthyosaurs of Europe Ichthyosauromorph genera

History of research

Description

See also

References