A team of paleontologists have announced the discovery of a partial skeleton of a 180 million year old ichtyosaurus, with the remains of six to eight embryos found between her ribs.
Ichtyosauruses were aquatic reptiles which dominated the Jurassic seas. They measured on average between one and ten meters long, and they were piscivorous (fish eating) and viviparous (carrying and giving birth to live young). They fed on other reptiles, fish and marine invertebrates such as belemnitida (an extinct species similar to squid). Ichtyosaurus fossils are quite common in the United Kingdom. However, only five specimens of ichtyosaurus have previously been found in the UK with embryos “inside them” (and none have ever been found with so many).
This new specimen, the first icthyosaurus with embryos ever to be registered in Yorkshire, is also geologically the youngest British embryo-carrying specimen, coming from the Toarcian stage of the Jurassic, aged around 180 million years old (the others date back to around 190 to 200 million years ago). The fossil has been kept since 2010 by a fossil collector, Martin Rigby, who, suspecting the presence of embryos, made a call to paleontologists Mike Boyd and Dean Lomax of the University of Manchester.
The specimen is cut in two, exposing several large ribs (belonging to the mother) and several remains of vertebrates and various small indeterminate bones. The researchers believe that there are at least 6 embryos present among these little bones, but probably eight. “We have also envisaged the possibility that the miniscule remains could be contents of the stomach, although it seems highly unlikely than an ichtyosaurus swallowed six to eight aborted embryos or newborn ichtyorsauruses at the same time”, notes Mike Boyd. It does not appear to have been the case, because the embryos do not present with any erosion from gastric acid, and the embryos are not mixed with any of the stomach contents typical of early Jurassic ichtyosauruses, such as belemnitida remains.
Eight different specimens of ichtyosaurus have been documented via the embryos. The ichtyosaurus most commonly found with embryos is the Stenopterygius. More than a hundred of these specimens have been found with embryos (from 1 to 11) in the area of Holzmaden and its surrounds in Germany.