Largest Ichthyosaurus Was Pregnant Mother

The new specimen is estimated to be between 3 and 3.5 m long and is an adult female. Ichthyosaurs were a highly successful group of sea-going reptiles that became extinct about 90 million years ago. Often misidentified as swimming dinosaurs, these reptiles appeared before the first dinosaurs had evolved. The largest species of ichthyosaur grew to over 20 m in length.

The new specimen was originally discovered on the Somerset coast, during the mid-1990s, and is from the Early Jurassic, roughly 200 million years old. However, the specimen remained unstudied until it wound up in the collections of the Lower Saxony State Museum in Hannover, Germany.

Palaeontologist Sven Sachs of the Bielefeld Natural History Museum (Germany) first saw the specimen in August 2016, whilst on a routine visit. He informed University of Manchester palaeontologist and ichthyosaur expert, Dean Lomax, and together, the pair examined the new specimen in early 2017. They identified it as an example of an Ichthyosaurus somersetensis, a new species that Dean and another colleague, Prof. Judy Massare, had previously identified.

Dean said “It amazes me that specimens such as this [the biggest] can still be ‘rediscovered’ in museum collections. You don’t necessarily have to go out in the field to make a new discovery. This specimen provides new insights into the size range of the species, but also records only the third example of an Ichthyosaurus known with an embryo. That’s special”

The embryo is incomplete and preserves only a portion of the back bone, a forefin, ribs and a few other bones. The preserved string of vertebrae is less than 7 cm long. The bones of the embryo are not fully ossified, meaning that the embryo was still developing.

Artist impression of pregnant Ichthyosaurus.

Credit: copyright of Joschua Knüppe.

Credit: © Dean R. Lomax