Researchers have found the largest Ichthyosaurus specimen in fossil record. Analysis revealed that the prehistoric marine reptile was pregnant when it died.
Ichthyosaurus belongs to a group of dolphin-like reptiles. They successfully thrived during the Jurassic and early Cretaceous era and died out with the dinosaurs about 90 million years ago. They are usually mistaken as seagoing dinosaurs and emerged before the first dinosaurs evolved.
The specimen, described in the journal Acta Palaeontologica Polonica on Aug. 28, measures between 3 and 3.5 meters long. It is relatively small when compared with the largest species of ichthyosaur that grew to more than 20 meters in length, but it is to date the largest known Ichthyosaurus specimen found.
The fossil, which was found in the Somerset coast in the mid-1990s, comes from the Early Jurassic and is estimated to be about 200 million years old.
"Regardless of the incomplete preservation, the estimated total length of this individual, based on the skull and precaudal length, is between 300 and 330 cm and it is thus the largest unequivocal example of the genus Ichthyosaurus," the researchers wrote in their study.
The Ichthyosaurus somersetensis specimen was housed in the Lower Saxony State Museum in Germany, where it was found by Sven Sachs, a paleontologist from Germany's Bielefeld Natural History Museum. Sachs and ichthyosaur expert, Dean Lomax, from University of Manchester, examined the specimen early this year and identified it as a new species of ichthyosaur.
Third Known Embryo For Ichthyosaurus
The embryo that the specimen bears is only the third known embryo for Ichthyosaurus and the first to be identified to the species level. In 2014, researchers also reported the discovery of another mother Ichthyosaur. Paleontologists who were looking for Saurichthys fossils in China accidentally discovered the fossilized remains of the Ichthyosaur that died while giving birth about 248 million years ago.
The embryo of the new specimen was incomplete and only a part of the backbone, ribs, a forefin, and some other bones were preserved. Its bones were not fully ossified, or turned into bony tissue, which means that it was still developing at the time of its mother's death.
Tail Taken From Another Ichthyosaur
The researchers also discovered that the tail of the specimen is not originally part of the rest of the skeleton. A tail taken from another ichthyosaur was added to the skeleton so it can appear more complete and look better when displayed.
"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," Lomax said.