ICHTHYOSAURUS
By: Heidi Fourie, Curator, DITSONG: National Museum of Natural History
In 1811, eleven-year-old Mary Anning and her brother Joseph were collecting shells and fossils for their widowed mother to sell in her tourist store in Lyme Regis, in southern England, when they found the skull of a five-metre fossil sea reptile later named Ichthyosaurus (Dixon 1988).
In December 2019 the first known case of the coronavirus disease (Covid-19) was announced in Wuhan in China. It eventually resulted in a world lockdown. At the same time researchers from Wuhan found a new species of ichthyosaur in the Guangxi Province, southwest China. This three-metre-long Mesozoic marine reptile was named Baisesaurus robustus.
Baseiasaurus is from the Lower Triassic. Most ichthyosaurs come from China. Icthyosaurs are mostly small (about 1 m long). This specimen is incomplete lacking the rear part of the skeleton. It has several features that are unique to this genus, amongst others the fact that it is 3 m long. The robust radius facilitated strong swimming abilities.
During the Triassic Period, dolphin-like carnivorous ichthyosaurus swam in the oceans. They are known as fish lizards and lived well into the Cretaceous Period. They gave birth to their young live and could grow up to 9 m (Rhodes et al. 1962) and are highly adapted for an aquatic lifestyle. The earliest forms date back to the late Triassic Period. They became very abundant in the Jurassic Period and can be found in the late Cretaceous as well. Several species are known, such as Mixosaurus, Temnodontosaurus and Ophthalmosaurus. Their heads are drawn out into a thin long snout fringed with small spiky teeth, the eyes are unusually large, the body is smooth and streamlined and a neck is absent. The limbs are modified into paddles and the tail is long and tapering. They fed on cephalopods, fish and occasionally pterosaurus (Norman 1985).
Three specimens are present in the Palaeontology collection at DITSONG: National Museum of Natural History with one a framed slab with a skeleton of an ichthyosaur with skull; and the other two are skulls. It is from the Jurassic Period Germany (no catalogue number). In appearance they had four paddles or flippers and a vertical tail fin.
Figure 1: Photographs of specimen on display at the DITSONG: National Museum of Natural History.
References:
DIXON, D. 1988. The Illustrated Dinosaur Encyclopedia.Hamlyn, London, UK. Page 144.
NORMAN, D. 1985. The Illustrated Encyclopedia of Dinosaurs. Salamander, London, UK. Page 208.
RHODES, F.H.T., ZIM, H.S. and SHAFFER, P.R. 1962. Fossils: A Guide to Prehistoric Life. Golden Press, New York. Page 160.
