28 November 2019

Utrecht student identifies rare long-necked marine reptile from age of dinosaurs

Fossils of plesiosaurs are extremely rare in the Netherlands: until recently, only a handful of teeth and just seven vertebrae, all belonging to different individuals, have been found. But with the discovery of a tail bone of a young plesiosaur, a new fossil can be added to the collection. The discovery was made during work in a subterranean quarry in the village of Sibbe in southern Limburg. When it was found, it was unclear as to which animal species the fossil belonged to. Utrecht student Feiko Miedema determined that it does indeed belong to a plesiosaur. The new discovery was presented at an international symposium in Maastricht on Saturday, 30 November.

The fossil was uncovered during quarry work by the firm Mergelbouwsteen Kleijnen, which donated it to Maastricht Natural History Museum without hesitation. Around that time, Feiko Miedema, a biology student with a special interest in fossil life, asked palaeontologist Anne Schulp whether he could suggest any interesting thesis topics. “Anne Schulp was already in contact with Maastricht, and brought up the new find. It was my job to find out which animal we were dealing with.”

Mergelblok met fossiele staartwervel plesiosaurus
Limestone block containing the fossilised tail vertebra of the plesiosaur (photo: Feiko Miedema)

Juvenile

The research primarily involved ruling out other possibilities. “We compared it to the potential candidates that lived during the same era, such as turtles or  mosasaurs, but the vertebra they found didn’t look like it belonged to those animals.” A study of the scientific literature pointed in the direction of a plesiosaur. “And since it wasn’t a full-grown vertebra, it’s highly probable that we’re dealing with a young individual.” The ‘juvenile’ animal still measured from one to five meters in length, however.

Zwemmende plesiosauriërs (afbeelding: N. Tamura)
Impression of two swimming plesiosaurs (drawing: N. Tamura/Wikipedia)

Not dinosaurs

Plesiosaurs were marine reptiles that lived from around 240 million to 66 million years ago, during the Jurassic and Cretaceous eras. They ate fish and squid, and could grow to lengths of 15 meters, much of which was due to their extremely long necks. Although the species’ name ends in ‘-saur’ and it lived during the age of dinosaurs, plesiosaurs are in no way related to dinosaurs.

Cretaceous sea

Paleontologists have sought intensively for fossils in the limestone around Maastricht for more than 250 years, but only a handful of plesiosaur fossils are known to have been found. That makes this discovery even more unique. “It’s more proof that no matter how thoroughly an area has been excavated, there’s literally always something else to find.” The plesiosaurs flourished at the end of the Cretaceous period, especially in coastal regions without a continental shelf, such as California, Morocco, etc. In these areas, cold currents from the depths circulated to the warmer surface waters, which was ideal for the production of plankton: the perfect conditions for a rich ecosystem with schools of fish for the plesiosaurs to eat. These conditions were not present in the shallow sea that produced the Maastricht Formation, however. The plesiosaurs found in southern Limburg may have been lone migrants or cadavers that had been carried by the currents from their usual habitat.

Fossiele staartwervel plesiosaurus
De gevonden staartwervel (afbeelding afkomstig uit artikel in Netherlands Journal of Geosciences))

Partnerships with amateurs

Miedema’s plesiosaur research rounded off his Bachelor’s degree in Biology, after which he enrolled in the Earth, Life and Climate Master’s programme at the Faculty of Geosciences. He is almost finished now, and will soon begin his PhD research at the Staatliches Museum für Naturkunde in Stuttgart, where he will study the development of ichthyosaurs and other extinct reptiles. “It’s fantastic work, but we lab palaeontologists don’t have many opportunities to get out in the field. So it’s even more special when we get our hands on finds like the one from Sibbe or from the many amateur geologist clubs. They do some extremely important work.” John Jagt, palaeontology curator at the Maastricht Natural History Museum, concurs. “Without them, we would never be able to fill our specimen drawers. Many new species have been named in honour of the collectors who found them, and many more will follow in the future.”

Presentation

Maastricht Natural History Museumhas officially presented the fossil on 30 November, when honorary curator Eric Mulder explained it and other rare plesiosaur fossils at the Chalk & Flint symposium. The symposium has been organised by the museum in collaboration with the Paleobiologische Kring and the University of Maastricht.

Article

Feiko Miedema conducted his research under the supervision of Anne Schulp and his colleagues at the Maastricht Natural History Museum. For a scientific description of the tail bone, see: Miedema F, Schulp AS, Jagt JWM, and Mulder EWA, ‘New plesiosaurid material from the Maastrichtian type area, the Netherlands’, Netherlands Journal of Geosciences, Volume 98, e3 (2019), https://doi.org/10.1017/njg.2019.2