In short: plesiosaurs were marine reptiles with four flippers that lived alongside, but were not, dinosaurs. Morocco has yielded plesiosaurs from two main settings: the Turonian rocks around Goulmima, about 94 to 90 million years old, and the much younger Maastrichtian phosphates of the Oulad Abdoun Basin, where Zarafasaura oceanis was found.
What was a plesiosaur?
Plesiosaurs were reptiles fully adapted to life in the sea. Instead of legs they had four large flippers, which they used like underwater wings. They breathed air, gave birth to live young and appear in the fossil record from the Late Triassic until the very end of the Cretaceous, about 66 million years ago.
Like mosasaurs, plesiosaurs were not dinosaurs. They belong to a separate group of marine reptiles that shared the Mesozoic seas with ichthyosaurs, turtles, sharks and, later, mosasaurs.
Long necks and short necks
Two body plans are found in Morocco:
- Elasmosaurids had small heads on extremely long necks, made of dozens of vertebrae. They probably fed on fish and other small prey.
- Polycotylids had shorter necks and longer, narrow skulls, a build closer to that of a fast pursuit predator.
Long-necked plesiosaurs are the source of the local name zarafa, the Arabic word for giraffe, which inspired the name Zarafasaura.
Zarafasaura oceanis: the phosphate plesiosaur
Zarafasaura oceanis was named in 2011 by Peggy Vincent and colleagues from a skull and lower jaw found in the Oulad Abdoun Basin near Khouribga. It is an elasmosaurid from the Maastrichtian, the last stage of the Cretaceous, which makes it one of the last plesiosaurs to have lived before the extinction event.
It shared the shallow phosphate sea with mosasaurs such as Prognathodon and Globidens, sharks and many kinds of fish. Read more about this environment in our guide to the Oulad Abdoun Basin.
The Goulmima plesiosaurs
Older plesiosaurs come from the Akrabou Formation near Goulmima, in southeastern Morocco. These Turonian limestone nodules have preserved some remarkably complete, three-dimensional skulls. Species described from this area include:
- Libonectes, a long-necked elasmosaurid;
- Thililua longicollis and Manemergus anguirostris, two short-necked polycotylids.
What plesiosaur fossils are found?
Most plesiosaur material from Morocco consists of isolated teeth and vertebrae. Plesiosaur teeth are long, slender and curved, with fine vertical ridges on the enamel. Vertebrae are often found in short series. Skulls, jaws, paddles and associated skeletons are much rarer and represent the most important specimens.
Reading a plesiosaur listing
When you look at a plesiosaur specimen, check the information given for:
- Identification: whether the fossil is identified to species, to genus, or only as plesiosaur.
- Locality and age: phosphate material is Maastrichtian; Goulmima material is Turonian.
- Association: whether vertebrae, paddle bones or skull elements come from one individual or have been assembled from several.
- Preparation, repairs and restoration: how much of the specimen is original fossil and what has been added or reconstructed.
If any of these points is not stated, ask before you buy.
Explore
Sources
- Vincent P. et al. (2011). Zarafasaura oceanis, a new elasmosaurid (Reptilia: Sauropterygia) from the Maastrichtian Phosphates of Morocco and the palaeobiogeography of latest Cretaceous plesiosaurs. Gondwana Research 19: 1062–1073.