Buried at Sea

One of the most interesting Early Cretaceous marine beds is the Paja Formation in central Colombia, dating back between 125 and 113 million B.C.E. Among the notable finds described from here include South American species of Kronosaurus and Platypterygius -- both better known from fossils in Australia -- an elasmosaurine plesiosaur called Callawayasaurus, and Desmatochelys padillae, described only this year and currently the oldest known sea turtle. Another surprise from this site, though, were ten tail vertebrae belonging to a brachiosaur, later named Padillasaurus. These sauropods are the tallest known dinosaurs, and until this year were only known from North America, Europe, and Africa. Ironically, most sauropods were regarded as amphibious, with legs too weak to support their bulk on land and high nostrils to allow them to breath while submerged. Both of these ideas have since been rejected, so the Padillasaurus probably died on land and had its remains washed out to sea.

Padillasaurus is hardly the first dinosaur to be buried at sea. The type of Archaeopteryx, one of the most famous fossils of all time, was excavated from the Late Jurassic Solnhofen Limestone in Bavaria, alongside fossilized ichthyosaurs, fish, and brittle stars. The carcasses of the ankylosaur Aletopelta and the hadrosaur Lophorhothon were both carried to sea between 80 and 75 million B.C.E (to Pacific and the Caribbean, which then covered northern Alabama, respectively).

One of the more recent and complete dinosaurs found in marine beds is Tethyshadros, uncovered in northern Italy and named for the ocean that covered most of Europe during the Late Cretaceous. This species is one of a handful of hadrosaurs known from Europe, and may have been a dwarf genus, just like the contemporaneous dinosaurs from Hațeg Island, now in modern Romania.