Ichthyosaurus

Ichthyosaurus was the first ichthyosaur named and thus gave rise to the family name Ichthyosauridae. Ichthyosaurus like most ichthyosaurs is often misidentified as a 'swimming dinosaur', although ichthyosaurs were not dinosaurs they were marine reptiles, though superficially they resemble dolphins and sharks. Ichthyosaurus is one of the most commonly known marine reptiles in the U.K. (though tentative material has been assigned to the genus outside of the UK) especially I. communis, the most common of the Ichthyosaurus species. I. intermedius is a dubious species and currently a nomen dubium, it is largely based on a difference in tooth morphology, which has been disputed.

Fossilised gastric contents (stomach material) have even been discovered with ichthyosaur specimens, here the remnants of an ichthyosaur's last meal before it died can be found. The most common remains include tiny ‘hooks’; that belonged to squid (on their tentacles) and fish scales. However, fragments of bone and isolated teeth have also been discovered in ichthyosaur coprolites.

I

Name

Ichthyosaurus communis

Authority

Conybeare, 1822

Meaning of generic name

"Fish Lizard"

Meaning of specific name

The most common species of Ichthyosaurus

Size

Length: 8.2 ft (2.5 m) perhaps largest 3-5 m

Remains

Holotype lost Neotype: BMNH R1162 Almost complete skeleton at the BMNH London. Numerous complete and partial skeletons.

Age and Distribution

Horizon: (1)Schlotheimia angulata to Arnioceras semicostatum zones Blue Lias Formation Early Jurassic (Upper Hettangian - Lower Sinemurian) (2)Psiloceras planorbis zone Uppermost Triassic (Rhaetian) and Early Jurassic (Lower Hettangian) (3)Early Jurassic (Upper Sinemurian) (4) Beggingen Member Semicostatum zone Early Jurassic (Lower Sinemurian)

Locality: (1)Lyme Regis, Dorset (2)Street, Somerset (3)Belgian Lorraine (Belgium) (4)Canton Aargau Switzerland

Classification

Ichthyopterygia IchthyosauriaThunnosauria

Further Reading

McGowan, C. 1974. A revision of the Latipinnate ichthyosaurs of the Lower Jurassic of England. Life Sciences Contribution 100, Royal Ontario Museum, 30 pp.

Lomax, D. R. 2010. An Ichthyosaurus (Reptilia, Ichthyosauria) with gastric contents from Charmouth, England: First report of the genus from the Pliensbachian. Paludicola 8(1):22-36 September 2010 © by the Rochester Institute of Vertebrate Paleontology

Lydekker, R. 1889. Catalogue of the fossil Reptilia and Amphibia in the British Museum (Natural History), Cromwell Road, S.W. Part II. Containing the Orders Ichthyopterygia and Sauropterygia. British Museum, Natural History), London.

Godefroit, P. 1995. Un crane d’ichthyosaurus communis (Reptilia, Ichthyosauria) du Sinemurian superieru de Lorrain Belge. Bulletin de la Société belge de Géologie 104:77-89.

Maisch, M. W., A. G. Reisdorf, R. Schlatter, and A. Wetzel 2008. A large skull of Ichthyosaurus (Reptilia, Ichthyosauria) from the Lower Sinemurian (Lower Jurassic) of Frick (NW Switzerland). Swiss Journal of Geoscience 101: 617-627.

Synonyms

Ichthyosaurus chiropolyostius, Hawkins 1834

Images by Nobu Tamura (click to enlarge)

Ichthyosaurus communis [March 1, 2009]:

[January 11, 2010]:

II

Name

Ichthyosaurus 'intermedius'

Authority

Conybeare, 1822

Meaning of specific name

intermediary

Size

Skull length: Less than 40 cm Length: 5.2 ft (1.6 m?)

Remains

Partial skeletons, of which some include skulls.

Age and Distribution

Horizon: Lower Jurassic (Hettangian or Sinemurian)

Locality: Lyme Regis, Dorset & Street, Somerset and possibly from the Lower Jurassic of Whitby

Further Reading

McGowan, C. 1974. & Lydekker, R. 1889. Ut supra.

Maisch, M. W. and A. T. Matzke 2000. The Ichthyosauria Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 298: 1-159.

Synonyms

Ichthyosaurus chiroparamecostius, Hawkins 1834

III

Name

Ichthyosaurus breviceps

Authority

Owen, 1881

Meaning of specific name

Named after the length of the skull?

[Actually ending -ceps means taking, so either stride with legs or bite, unless Latin has been remodelled here. Bite would be more appropriate for a fish like creature. And from image of Nobu Tamura it seems snout is considerably shorter]

Size

Length: 4.9 ft (1.5 m)

Remains

Holotype: BMNH 43006 A complete specimen. Several referable specimens including skull and post cranial material are assignable to this species.

["Are assignable"! What wisdom, not as "are actually definately assigned"!]

Age and Distribution

Horizon: Schlotheimia angulata to Arnioceras semicostatum zones Blue Lias Formation Early Jurassic (Upper Hettangian - Lower Sinemurian) & (Lower Sinemurian, Bucklandi Zone)

Locality: Lyme Regis, Dorset

Further Reading

McGowan, C. 1974. Ut supra.

Image by Nobu Tamura (click to enlarge)

Ichthyosaurus breviceps:

IV

Name

Ichthyosaurus conybeari

Authority

Lydekker, 1888

Meaning of specific name

Named after famous palaeontologist William Daniel Conybeare

Size

Length: 87 cm (2.8 ft)

Remains

Holotype: BGS GSM 956 A beautifully preserved, complete skeleton comprising a skull

Age and Distribution

Horizon: Schlotheimia angulata to Arnioceras semicostatum zones Blue Lias Formation Early Jurassic (Upper Hettangian - Lower Sinemurian)

Locality: Lyme Regis, Dorset U.K.

Further Reading

McGowan, C. 1974. Ut supra.

Creationist suspicion I

Ichthyosaurs, known to give birth to live offspring [from fossile also proving rapid burial], are dolphins - rejected by one expert I asked:

Correspondence de / of / van Hans-Georg Lundahl : Are Ichthyosauri Dolphins? I Asked Benjamin Moon
[of Bristol University, and one of the team behind the original palaeocritti site, see links in name of animal]
http://correspondentia-ioannis-georgii.blogspot.com/2013/12/are-ichthyosauri-dolphins-i-asked.html

Creationist suspicion II

Ichthyosaurus conybeari could be a juvenile of other species - supposing them to be really different ones.