''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 th ...

'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 nom ...

of marine prehistoric reptiles ( ichthyosaurs) 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 and ...

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

. It is characterized by the extreme elongation of the

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

, with the lower jaw about three-fourths of the length of the upper jaw, giving the animal a swordfish-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 sever ...

, 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 , lord_ ...

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 characteristi ...

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 ''Leptonectes'' is a genus of ichthyosaur that lived in the Late Triassic to Early Jurassic (Rhaetian - Pliensbachian). Fossils have been found in Belgium, Germany, Switzerland, Spain and the United Kingdom.Maisch MW, Matzke AT. 2000. The Ich ...

'' from the Rhaetian (Late

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

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

Eurhinosaurus ''Eurhinosaurus'' (Greek for 'well-nosed lizard'- eu meaning 'well or good', rhino meaning 'nose' and sauros meaning 'lizard') is an extinct genus of ichthyosaur from the Early Jurassic (Toarcian), ranging between 183 and 175 million years. Foss ...

'' 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 Toarcian ...

(Early Jurassic) of

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

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