Liopleurodon

In 1905, John Frederick Blake described two teeth from Rushden, England, similar to those of other Liopleurodon ferox specimens, though from older strata than those from Peterborough. He noted that the teeth were quite different from those of Pliosaurus, while the bones were dissimilar to those of Polyptychodon. Since the species couldn't be assigned to either genus, he recommended reinstating the name Liopleurodon.^[17] After considering Liopleurodon to be a subgenus of Pliosaurus, N. Bogolubov also listed the two genera as distinct in 1912.^[4]

When Lydekker had first visited the collection of Alfred Leeds (known as the Leeds Collection), the only remains of Liopleurodon in his collection were teeth.

Hermann Linder also described specimens of Liopleurodon ferox in 1913. One of these was a poorly preserved partial skeleton excavated from the Oxford Clay of Fletton, England, housed in Institut für Geowissenschaften, University of Tübingen. The skeleton was mounted and missing regions were restored with material from other Liopleurodon specimens. Like Andrews, Linder also considered L. ferox to be a species of Pliosaurus. Additionally, Linder described some skulls from Fletton housed at both the University of Tübingen and the State Museum of Natural History Stuttgart as specimens of P. grandis. Linder also assigned a nearly complete paddle to Pliosaurus sp.^[20] All of these specimens have since been assigned to Liopleurodon with varying degrees of confidence, though the skull Linder attributed to P. grandis that was housed in Stuttgart was destroyed during World War II.^{[1]: 28, 63, 114} In 1934, Friedrich von Huene described a partial skeleton from Swabia, Germany. He also used Pliosaurus ferox instead of Liopleurodon ferox.^{[4][1]: 297} In 1939, Alexandre Bigot used Pliosaurus ferox as well, assigning some teeth from France to this species.^[4][1]: 32

Lambert Beverly Halstead, then known as Tarlo, published a review of Upper Jurassic pliosaurid taxonomy in 1960. He considered Liopleurodon to be distinct from Pliosaurus, noting major differences between the mandibles of the two genera. In addition to the type species L. ferox, Tarlo also considered Pliosaurus pachydeirus to be a valid species within Liopleurodon, L. pachydeirus, noting that the two species had differences in their teeth and cervical vertebrae. L. grossouvrei was not considered valid, though it was tentatively retained for teeth from the Kellaways Formation.^[4] In 1971, Halstead published another paper about Jurassic pliosaurids, this time focusing on Pliosaurus rossicus, a species he was formerly unwilling to consider valid, due to a lack of information. After reviewing its anatomy, he considered it valid, though assigned it to Liopleurodon instead, based on its short mandibular symphysis. Halstead also considered Pliosaurus macromerus, which he had previously considered to belong to its own genus, Stretosaurus, to instead be a species of Liopleurodon, despite its irregularly-shaped scapula (although this was later discovered to be an ilium).^[21][7] In 1992, Martill identified a fragmentary specimen belonging to a young adult individual, PETCM R.296, as cf. Liopleurodon sp.; the specimen was found to have at least 7 gastroliths in its stomach and soft tissues, although the specific features of the latter cannot be observed due to poor preservation.^[22]

In a 2001 dissertation, Leslie F. Noè argued that L. pachydeirus was not diagnostic, and that L. ferox was the only valid species of Liopleurodon. The teeth of mounted skeleton in Tübingen, which Tarlo had attributed to L. pachydeirus, showed distinctive characteristics of L. ferox, indicating that cervical vertebrae are not useful for differentiating species, as argued by David S. Brown in 1981.^[23] While Tarlo had considered differences in tooth morphology to be diagnostic, Noè instead considered it to be individual variation. Noè also removed L. macromerus and L. rossicus from the genus, citing differences in tooth shape and mandibular symphysis length. The former species was tentatively placed back in Pliosaurus, while the latter was thought to warrant a new genus.^{[1]: 26, 172–175}

Liopleurodon fossils have been found mainly in England and France. Fossil specimens that are contemporary (Callovian-Kimmeridgian) with those from England and France referrable to Liopleurodon are known from Germany.

Liopleurodon ferox first came to the public attention in 1999 when it was featured in an episode of the BBC television series Walking with Dinosaurs, which depicted it as an enormous 25 m (82 ft) long and 150 t (330,000 lb) predator; this was based on very fragmentary remains, and considered to be an exaggeration for Liopleurodon,^[29] with the calculations of 20-metre (66 ft) specimens generally considered dubious.^[30]

Estimating the size of pliosaurs is difficult because not much is known of their postcranial anatomy. The palaeontologist L. B. Tarlo suggested that the pliosaurs’ total body length can be estimated from the length of their skull which he claimed was typically one-seventh of the former measurement.^[29] Additional Kronosaurus specimens^[29] and a skeleton of L. ferox, GPIT 1754/2, show that the pliosaurs’ skulls were actually about one-fifth of their total body length.^[31] One large skull specimen of L. ferox, CAMSMJ.27424, has an estimated total body length of 6.39 m (21.0 ft).^[31] McHenry estimated that smaller individuals measuring about 4.8–5.7 m (16–19 ft) long would have weighed around 1–1.7 t (2,200–3,700 lb) based on the specimen NHM R2680.^[32]

Some researchers propose larger estimates of over 10 m (33 ft). Tarlo applied the aforementioned one-seventh ratio of skull length to body length, estimating that the largest known specimen of L. ferox was a little over 10 m (33 ft), though a more typical size range would be from 5 to 7 m (16 to 23 ft).^[29] In the 2023 book Ocean Life in the Time of Dinosaurs, Bardet and colleagues also claimed that some individuals could reach lengths of over 10 m (33 ft).^{[33]: 158, 160}

Classification

Liopleurodon belongs to clade

Liopleurodon was one of the basal taxa from the Middle Jurassic. Differences between these taxa and their relatives from the Upper Jurassic include alveoli count, smaller skull and smaller body size.^[35]

An analysis in 2013 classifies Liopleurodon,

The cladogram below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, and reduced to genera only.^[37]

Pliosauroidea	Rhomaleosauridae Anningasaura "Plesiosaurus" macrocephalus Archaeonectrus Macroplata Atychodracon Eurycleidus Rhomaleosaurus Meyerasaurus Maresaurus Pliosauridae Thalassiodracon Hauffiosaurus Attenborosaurus BMNH R2439 (?Peloneustes) Marmornectes "Pliosaurus" andrewsi Eardasaurus Peloneustes Simolestes Liopleurodon Pliosaurus Megacephalosaurus[38] Brachauchenius Kronosaurus

Palaeobiology

Four strong paddle-like limbs suggest that Liopleurodon was a powerful swimmer. Its four-flipper mode of propulsion is characteristic of all plesiosaurs. A study involving a swimming robot has demonstrated that although this form of propulsion is not especially efficient, it provides very good acceleration—a desirable trait in an ambush predator.^[39][40] Studies of the skull have shown that it could probably scan the water with its nostrils to ascertain the source of certain smells.^[41]

A fragmentary specimen possibly belonging to a young adult individual, PETCM R.296, contained numerous hooklets of teuthoid

vestibular labyrinth) which are known to occur in the gut of cetaceans, fish may not have been an important part of its diet. The other possibility is that the pliosaur fed on large cephalopod-feeders, with the hooklets representing the residues of the stomach contents of the pliosaur's prey, but there is no firm evidence to this claim. It is also notable that this specimen preserved at least 7 gastroliths, which probably weren't used for grinding based on the well-preserved conditions of the hooklets. It is possible either that the pliosaur accidentally swallowed the stones and they remained in its gut, or that the stones represent the "acid resistant residue from carbonate cemented sandstone."^[22]

See also

• List of plesiosaur genera
• Timeline of plesiosaur research

Notes

References

1. ^ ^{a b c d e f g h i} Noè, L. F. (2001). A taxonomic and functional study of the Callovian (Middle Jurassic) Pliosauroidea (Reptilia, Sauropterygia) (Thesis). Chicago: University of Derby.
2. ^ Meyer, H. v. (1841). "Thaumatosaurus oolithicus der fossile Wunder-Saurus aus dem Oolith". Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde: 176–184.
3. ^ Meyer, H. v. (1856). "Thaumatosaurus oolithicus aus dem Oolith von Neuffen". Palaeontographica. 6: 14–18.
4. ^ ^{a b c d e f g h i j k} Tarlo, L. B. (1960). "A review of the Upper Jurassic pliosaurs". Bulletin of the British Museum (Natural History). 4 (5): 145–189.
5. ^ Wagner, J. A. (1952). "Neu-aufgefundene Saurier-Überreste aus den lithographischen Schiefern und dem obern Jurakalke". Abhandlungen der Bayerischen Akademie der Wissenschaften, München. 6: 663–710.
6. ^ Conybeare, W. D. (1824). "On the discovery of an almost perfect skeleton of the Plesiosaurus". Transactions of the Geological Society of London. 2 (2): 381–389.
7. ^ ^{a b} Knutsen, E. M. (2012). "A taxonomic revision of the genus Pliosaurus (Owen, 1841a) Owen, 1841b" (PDF). Norwegian Journal of Geology. 92: 259–276.
8. ^ von Meyer H. (1838).  Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde. Jahrgang 1838:413-418
9. ^ Meyer, H. v. (1856). "Ischyrodon meriani aus dem Oolith im Frickthale". Palaeontographica. 6: 19–21.
10. ^
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11. ^ Sauvage, H. E. (1873). "Notes sur les reptiles fossiles". Bulletin de la Société Géologique de France. Series 3. 1: 377–380.
12. ^ Sauvage, H. E. (1880). "Synopsis des poissons et des reptiles des terrains jurassiques de Boulogne-sur-Mer". Bulletin de la Société Géologique de France. 3 (8): 524–547.
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14. ^ ^{a b} Seeley, H. G. (1869). Index to the fossil remains of Aves, Ornithosauria, and Reptilia, from the secondary system of strata arranged in the Woodwardian Museum of the University of Cambridge. Cambridge, Deighton, Bell, and co. p. 118.
15. ^ Lydekker, R. (1889). Catalogue of the Fossil Reptilia and Amphibia in the British Museum (Natural History). Vol. 2. London: The British Museum (Natural History).
16. ^ Kiprijanoff, W. (1883). "Studien über die Fossilen Reptilien Russlands. Group Thaumatosauria n. aus der Kreide-Formation und dem Moskauer Jura". Mémoires de l'Académie impériale des sciences de St.-Pétersbourg. 7 (31): 1–57.
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18. ^ Andrews, C. W. (1910). A descriptive catalogue of the marine reptiles of the Oxford clay. Based on the Leeds Collection in the British Museum (Natural History), London. Vol. 1. London: British Museum.
19. ^ Andrews, C. W. (1913). A descriptive catalogue of the marine reptiles of the Oxford clay. Based on the Leeds Collection in the British Museum (Natural History), London. Vol. 2. London: British Museum.
20. ^ Linder, H. (1913). "Beiträge zur Kenntnis der Plesiosaurier-Gattungen Peloneustes und Pliosaurus". Geologische und Palaeontologische Abhandlungen (in German). 11: 339–409.
21. ^ Halstead, L. B. (1971). "Liopleurodon rossicus (Novozhilov): A pliosaur from the lower Volgian of the Moscow Basin". 14. 14 (4): 566–570.
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23. ^ Brown, D. S. (1981). "The English Upper Jurassic Plesiosauroidea (Reptilia) and a review of the phylogeny and classification of the Plesiosauria". Bulletin of the British Museum (Natural History) Geology. 35 (4): 253–347.
24. ^ Sachs, S. (1997). "Mesozoische Reptilien aus Nordrhein-Westfalen." Pp. 22-27 in Sachs, S., Rauhut, O.W.M. and Weigert, A. (eds.), Terra Nostra. 1. Treffen der deutschsprachigen Paläoherpetologen Düsseldorf.
25. ^ Sachs, Sven; Christian Nyhuis (2015). "Belege für riesige Pliosaurier aus dem Jura Deutschlands" (PDF). Der Steinkern. 21: 74–82.
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27. ^ Barrientos-Lara, J. I.; Fernández, M. S.; Alvarado-Ortega, J. (2015). "Kimmeridgian pliosaurids (Sauropterygia, Plesiosauria) from Tlaxiaco, Oaxaca, southern Mexico". Revista Mexicana de Ciencias Geológicas. 32 (2): 293–304.
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29. ^ ^{a b c d} Forrest, Richard (20 November 2007). "Liopleurodon". The Plesiosaur Site. Archived from the original on 15 July 2011. Retrieved 7 June 2009.
30. ^ "Re: Liopleurodon size". Archived from the original on 25 April 2021. Retrieved 26 October 2014.
31. ^
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32. hdl:1959.13/935911
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33. ISBN 9780691243948
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34. S2CID 19710180
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35. PMID 23741520
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36. S2CID 19710180
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37. ^ Hilary F. Ketchum; Roger B. J. Benson (2011). "A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids". Special Papers in Palaeontology. 86: 109–129.
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40. ^ "Swimming Robot Tests Theories About Locomotion In Existing And Extinct Animals". ScienceDaily. 30 May 2006. Retrieved 7 June 2009.
41. ^ Carpenter, K. (1997). "Comparative cranial anatomy of two North American Cretaceous plesiosaurs." Pp. 191–216 in Callaway, J.M. and Nicholls, E.L. (eds.), Ancient Marine Reptiles. Academic Press.

External links

Wikimedia Commons has media related to Liopleurodon.

• Liopleurodon information and photos, The Plesiosaur Directory
• Article on the giant pliosaur skull once assigned to Liopleurodon, Tetrapod Zoology