User:Amirani1746/sandbox7

Not to be confused with Tenontosaurus.

Amirani1746/sandbox7 Temporal range: Hettangian-Toarcian
Mounted skeleton of T. trigonodon in metal frame at the State Museum of Natural History Stuttgart, Germany
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Family:	†Temnodontosauridae McGowan, 1974
Genus:	†Temnodontosaurus Lydekker, 1889
Type species
†Temnodontosaurus platyodon Conybeare, 1822
Other species
List Recognized species † T. trigonodon von Theodori, 1843 † T. crassimanus Blake, 1876 † T. zetlandicus Seeley, 1876 † T. nuertingensis von Huene, 1931 Disputed species † T.? eurycephalus McGowan, 1974 † T.? azerguensis Martin et al., 2012

Temnodontosaurus (meaning "cutting-tooth lizard") is an extinct genus of large ichthyosaurs that lived during the Lower Jurassic in what is now Western Europe and possibly Chile. The first known fossil is a specimen consisting of a complete skull and partial skeleton discovered on a cliff by Joseph and Mary Anning around the early 1810s in the Dorset county, England. The anatomy of this specimen was subsequently analyzed in a series of articles written by Everard Home between 1814 and 1819, making it the very first ichthyosaur to have been scientifically described. In 1822, the specimen was assigned to the genus Ichthyosaurus by William Conybeare, and more precisely to the species I. platyodon. Noting the large dental differences with other species of Ichthyosaurus, Richard Lydekker suggested in 1889 moving this species into a separate genus, which he named Temnodontosaurus. While many species have been assigned to the genus, only five are currently recognized as valid, the others being considered as synonymous, doubtful or possibly belonging to other taxa.

Research history

Other species

Dubious species

Holotype skull and life restoration of T. eurycephalus.

In 1881, Owen attributed a large isolated skull discovered at Lyme Regis, cataloged as NHMUK PV R1157, to the newly erected species of the genus Ichthyosaurus, I. breviceps. In 1922, von Huene moved this species to the genus Eurypterygius, a taxon which is itself recognized as a junior synonym of Ichthyosaurus. Although I. breviceps is still recognized as belonging to this genus, the large skull historically attributed to the species has large differences with the holotype specimen. Noting this, McGowan redescribed this specimen in more detail and made it the holotype of an entirely new species of Temnodontosaurus, T. eurycephalus. The specific name comes from the Ancient Greek ευρύς (eurús, "broad"), and κεφαλή (kephalế, "head"), all meaning "broad head", in reference to the cranial morphology of the taxon.

In 1984, an almost complete skeleton of a large ichthyosaur was discovered in the Lafarge quarries in the French commune of Belmont-d'Azergues, located near Lyon. Although the specimen is mentioned in a detailed biostratigraphic analysis of the Lafarge quarries published in 1991, it was in 2012 when the fossil, uncatalogued but stored in the Saint-Pierre-la-Palud local mining museum, was officially designated as the holotype of the new species T. azerguensis by Jeremy E. Martin and his colleagues in 2012. The specific name comes from the Azergues, a river located near the site of the discovery.

In 2014, the American paleontologist Darren Naish expressed doubts in a blog in the journal Scientific American about the attribution of these two species to Temnodontosaurus, noting their large anatomical differences highlighting the need for a taxonomic revision of this genus. A similar observation is shared in the study describing T. zetlandicus in 2022, with the authors mentioning these two species as too phylogenetically unstable to be included in a monophyletic grouping of Temnodontosaurus.

Description

Temnodontosaurus, like other ichthyosaurs, had a long, thin snout, large eye sockets, and a tail fluke that was supported by vertebrae in the lower half. Ichthyosaurs were superficially similar to dolphins and had flippers rather than legs, and most (except for early species) had dorsal fins. Although the colour of Temnodontosaurus is unknown, at least some ichthyosaurs may have been uniformly dark-coloured in life, which is evidenced by the discovery of high concentrations of eumelanin pigments in the preserved skin of an early ichthyosaur fossil.

Size

Size of T. platyodon compared to a human

Temnodontosaurus is one of the largest ichthyosaurs identified to date, although the different species that make up the genus are not as imposing like the Triassic forms Shonisaurus, Himalayasaurus, Cymbospondylus or Ichthyotitan. It nevertheless represents the largest known ichthyosaur of the parvipelvian group. The most complete known specimens of the type species T. platyodon, MHMUK PV R2918 and MHMUK PV R2003, measure 6 m (20 ft) and 6.8 m (22 ft) long respectively. However, based on an imposing skull cataloged as NHMUK PV R1155, McGowan sets the maximum body length of this species at 9 m (30 ft) for a skull 1.5 m (4 ft 11 in) long. With a skull measuring a maximum of 1.8 m (5 ft 11 in) long and a little over 9 m (30 ft) in total length, T. trigonodon is view as the largest species of the genus. The ‘Rutland Sea Dragon’, a possible specimen of T. trigonodon discovered in January 2021 in the Rutland Water, is estimated to be slightly over 10 m (33 ft) long. Although incomplete, the holotype skeleton of T. crassimanus has a body length estimated at around 9 m (30 ft) for a skull approximately 1 m (3 ft 3 in) long. No body length estimates for T. zetlandicus and T. nuertingensis have currently been given. However, the measurement of their skull, reaching respectively 1 to 1.3 m (3 ft 3 in to 4 ft 3 in) in length, suggests that they are smaller representatives when compared to the three species previously mentioned.

Individual bones suggest that Temnodontosaurus may have grown to a larger size. In his extensive revision published in 1922, von Huene described a series of very imposing vertebrae from Banz Abbey, Germany, the largest of them measuring 22 cm (8.7 in) high. In 1996, McGowan nominally assigned the specimen to Temnodontosaurus sp.. Based on SMNS 50000, a nearly complete skeleton of T. trigonodon, the author estimated the size of Banz's specimen at 16 m (52 ft) long, as Huene initially suggested. However, the estimate he proposes turns out to be exaggerated, given that the source of its size is incorrect based on the actual measurements of the specimen SMNS 50000, which is of a shorter length.

See also

• List of ichthyosaurs
• Timeline of ichthyosaur research

References

Bibliography

• Liddell, Henry G.; Scott, Robert (1980) [1871]. A Greek-English Lexicon (abridged ed.). Oxford: Oxford University Press.
• Owen, Richard (1881). A monograph of the fossil Reptilia of the Liassic formations, Part III, Ichthyopterygia. London: Printed for the Palæontographical Society. pp. 83–134. OCLC 6930920.
• Nicholson, Henry A.; Lydekker, Richard (1889). "Palaeozoology; Vertebrata". A manual of palaeontology for the use of students with a general introduction on the principles of palaeontology. Vol. 2. Edinburgh and London: William Blackwood and Sons. p. 889–1464. OCLC 7919973.
• von Huene, Friedrich (1922). Die Ichthyosaurier des Lias und ihre Zusammenhänge [The Ichthyosaurs of the Lias and their connections] (in German). Berlin: Verlag von Gebrüder Borntraeger. OCLC 19870277.
• McGowan, Christopher (1992). Dinosaurs, spitfires, and sea dragons. Cambridge: Harvard University Press. ISBN 978-0-6742-0770-7.
• Cadbury, Deborah (2000). The Dinosaur Hunters : A True Story of Scientific Rivalry and the Discovery of the Prehistoric World. London: Fourth Estate. ISBN 978-1-85702-963-5.
• Maisch, Michael W.; Matzke, Andreas T. (2000). "The Ichthyosauria". Stuttgarter Beiträge zur Naturkunde, Serie B. 298: 1–159.
• McGowan, Christopher; Motani, Ryosuke (2003). Handbook of Paleoherpetology Part 8: Ichthyopterygia. Vol. 1. Munich: Verlag Dr. Friedrich Pfeil. ISBN 978-3-899-37007-2. OCLC 469848769.
• Ellis, Richard (2003). Sea Dragons: Predators of the Prehistoric Oceans. Lawrence: University Press of Kansas. ISBN 978-0-7006-1394-6.
• Maisch, Michael W. (2010). "Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art" (PDF). Palaeodiversity. 3: 151–214.
• Wolniewicz, Andrzej S. (2017). The Anatomy, Taxonomy and Systematics of Middle Triassic–Early Jurassic Ichthyosaurs (Reptilia: Ichthyopterygia) and the Phylogeny of Ichthyopterygia (PhD). University of Oxford.
• Swaby, Emily J. (2020). A revision of Temnodontosaurus crassimanus (Reptilia: Ichthyosauria) from the Lower Jurassic (Toarcian) of Whitby, Yorkshire, UK (PDF) (MPhil). University of Manchester.

External links

Paleontological videos

• Attenborough, David (7 January 2019). "Meet a Jurassic Killer: Temnodontosaurus". Nature on PBS. Archived from the original on 29 May 2024 – via YouTube.