Ichthyotitan
| Ichthyotitan Temporal range: Late Triassic (Rhaetian), ~
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| Life restoration of Ichthyotitan severnensis with Birgeria fish used for size comparison. | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Ichthyosauria |
| Family: | †Shastasauridae (?) |
| Genus: | †Ichthyotitan |
| Species: | †I. severnensis
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| Binomial name | |
| †Ichthyotitan severnensis Lomax et al., 2024
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Ichthyotitan (meaning "giant fish lizard") is an extinct genus of probable shastasaurid ichthyosaur from the Late Triassic (late Rhaetian) Westbury Mudstone Formation of Somerset, United Kingdom. The genus contains a single species, I. severnensis, known from two surangular bones. It may have had a body length near 25 metres (82 ft), making it the largest marine reptile currently known.
Discovery and naming
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The first specimen that would later be referred as Ichthyotitan, BRSMG Cg2488 (the "Lilstock specimen"), was found in 2016. It consists of a partial left surangular measuring 96 centimeters (3.15 ft) long. In 2018, Dean Lomax, de la Salle, Judy Massare, and Ramues Gallois identified the Lilstock specimen as belonging to a shastasaurid.[1]
The Ichthyotitan holotype specimen, BRSMG Cg3178, was discovered in sediments of the Westbury Formation near Blue Anchor in Somerset, UK. The first fragment was found in 2020, with subsequent expeditions until 2022 revealing additional pieces. The specimen consists of fragments of a right surangular. Histological features suggest that the specimen was still growing, so was either a subadult or a young adult.[2]
In 2024, Lomax et al. described Ichthyotitan severnensis as a new genus and species of probable shastasaurid ichthyosaur based on BRSMG Cg3178 and BRSMG Cg2488. The generic name, Ichthyotitan, combines a reference to Ichthyosaurus—whose name means "fish lizard", combing the Greek words "ichthys", meaning "fish", and "sauros", meaning "lizard"—with the Greek suffix "-titan", meaning "giant". The specific name, severnensis, references the Severn Estuary near the type locality.[2]
Other fragmentary remains of giant ichthyosaurs of a similar age to Ichthyotitan have also been reported from Germany (Bonenburg) and France (Autun).[3]
Description
While its incompleteness made the size of the animal difficult to determinate, it was clearly very large. Using Shonisaurus sikanniensis as a model, the researchers estimated the ichthyosaur to have been around 26 meters (85 ft) long, nearly the size of a blue whale. Scaling based on Besanosaurus, however, found a shorter length estimate of 22 meters (72 ft).[1] The 2024 study describing Ichthyotitan provided a similar revised length estimate of 25 metres (82 ft), making it one of—if not the—largest marine reptiles ever described.[2]
References
- ^ a b Lomax, Dean R.; De la Salle, Paul; Massare, Judy A.; Gallois, Ramues (2018-04-09). Wong, William Oki (ed.). "A giant Late Triassic ichthyosaur from the UK and a reinterpretation of the Aust Cliff 'dinosaurian' bones". PLOS ONE. 13 (4): e0194742. Bibcode:2018PLoSO..1394742L. doi:10.1371/journal.pone.0194742. ISSN 1932-6203. PMC 5890986. PMID 29630618.
- ^ a b c Lomax, D. R.; de la Salle, P.; Perillo, M.; Reynolds, J.; Reynolds, R.; Waldron, J. F. (2024). "The last giants: New evidence for giant Late Triassic (Rhaetian) ichthyosaurs from the UK". PLOS ONE. 19 (4). e0300289. doi:10.1371/journal.pone.0300289.
- ^ Perillo, Marcello; Sander, P. Martin (2024-04-09). "The dinosaurs that weren't: osteohistology supports giant ichthyosaur affinity of enigmatic large bone segments from the European Rhaetian". PeerJ. 12: e17060. doi:10.7717/peerj.17060. ISSN 2167-8359.
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