Simolestes Explained

Simolestes (meaning "snub-nosed thief") is an extinct pliosaurid genus that lived in the Middle to Late Jurassic.^[1] The type specimen, NHMUK PV R 3319 is an almost complete but crushed skeleton diagnostic to Simolestes vorax, dating back to the Callovian of the Oxford Clay formation, England. The genus might also be known from the Tithonian Bhuj Formation of India (S.indicus),^[2] however the referral of this species to Simolestes is dubious. S.keileni from France was moved to the new genus Lorrainosaurus in 2023.^[3]

Description

Simolestes possessed a short, high, and wide skull which was built to resist torsional forces when hunting.

The largest specimens of S.vorax reached approximately 4.6m (15.1feet) in length, if a head to body ratio similar to Liopleurodon is applied.^[4]

Palaeobiology

Like most pliosaurs, Simolestes possessed salt secreting glands, which would have enabled the animal to maintain salt balance and drink seawater.^[5] Recent studies on plesiosaur locomotion indicate that Simolestes, like other plesiosaurs, possessed a unique bauplan for movement, which differs from modern organisms in similar niches.^[6]

Feeding habits

Simolestess exact feeding habits are unclear. The current consensus, however, is that the genus was primarily teuthophagous, consuming belemnites, soft teuthoids and ammonites. It is possible Simolestes was also ecologically separated from other contemporary pliosaur genera such as Liopleurodon and Pachycostasaurus by hunting in deeper waters or at night, as modern cephalopods exhibit diurnal feeding cycles, spending daylight in deeper, safer waters, and rising at night to feed.

Classification

The cladogram below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, and reduced to genera only.^[7]

Notes and References

1. 10.1007/s00114-008-0402-z. 18523747. The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: Implications for plesiosaur phylogenetics. Naturwissenschaften. 95. 10. 975–80. 2008. Smith. Adam S.. Dyke. Gareth J.. 2008NW.....95..975S. 12528732.
2. R. Lydekker. 1877. Notices of new and other Vertebrata from Indian Tertiary and Secondary rocks. Records of the Geological Survey of India 10(1):30-43
3. Godefroit, P. (1994). Simolestes keileni sp. nov., un Pliosaure (Plesiosauria, Reptilia) du Bajocien supérieur de Lorraine (France). Bulletin des Académie et Société Lorraines des sciences,, 1994, tome 33, n°2, p. 77-95. 33. .
4. Noe. Leslie F. . Jeff Liston . Mark Evans. The first relatively complete exoccipital-opisthotic from the braincase of the Callovian pliosaur, Liopleurodon. Geological Magazine. 140. 4. 479–486. 2003. 10.1017/S0016756803007829. 2003GeoM..140..479N . 22915279 .
5. Noè, L. F. (2001). A taxonomic and functional study of the Callovian (Middle Jurassic) Pliosauroidea (Reptilia, Sauropterygia). Chicago
6. Muscutt . Luke E. . Dyke . Gareth . Weymouth . Gabriel D. . Naish . Darren . Palmer . Colin . Ganapathisubramani . Bharathram . The four-flipper swimming method of plesiosaurs enabled efficient and effective locomotion . Proceedings of the Royal Society B: Biological Sciences . 2017 . 284 . 1861 . 20170951 . 10.1098/rspb.2017.0951. 28855360 . 5577481 .
7. 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 .