Polycotylidae

Live reconstruction of Edgarosaurus

• Europe
• North and South America
• East Asia, Australia, New Zealand

The Polycotylidae (synonyms: Dolichorhynchopidae, Trinacromeridae ) are a family of Plesiosauria, which was widespread in the Cretaceous world. They are mainly known for partially and fully -preserved skeletons from the Upper Cretaceous of North America. More fragmented fossils, which are assigned to the Polycotylidae come from Europe, South America, East Asia, Australia and New Zealand. They had a relatively short neck and a long snout.

Features

Most Polycotylidae were medium in size, the largest reached a length of nine meters. They had a very elongated compared to skull length, formed by long and slender premaxilla and maxilla snout ( rostrum ). The premaxilla formed the front and upper limit of the nostrils, the maxilla of the bottom. The premaxilla was oberseits extended and hit the parietal between the bony orbits. A thin vomer separating the premaxilla of a V -shaped slot, which was perhaps the seat of a Jacobson 's organ. A lacrimal bone was missing. The prefrontal limited the eye sockets above and formed a bony eyebrow. The cranial window were very large and limited the parietal on a high, the skull covering comb. The teeth were small and uniform. The replacement teeth grew in pits between the teeth in use.

Overall, similar to her skull where the ichthyosaur. Since they are mainly known from the Late Cretaceous, they could have taken over the ecological niche of the ichthyosaur after their extinction as fast floating hunters of small fishes and cephalopods. In its stomach region was found ammonite jaw.

The Polycotylidae had 19 to 26 cervical vertebrae, 20 dorsal vertebrae and about 24 vertebrae supported the tail. The shoulder-blades separated by said arc-shaped clavicle. The pool was great, the ischium long. Humerus and femur were equal. The outer bones of the limbs were very small.

System

Most Polycotylidae aligned with their short neck and long extended snout to Pliosauriern to which they were numbered first. However, they shared some features with the Cryptoclididae and Elasmosauridae and are therefore among the plesiosaurs in the narrow sense ( Plesiosauroidea ). These features included the brevity of the region of the skull behind the eye, the large eye sockets, the narrow snout, small teeth, the bone crest on the skull and the shortness and breadth of the humerus and femur.

The fossil of a Thililua Polycotyliden newly described in 2003, consists of the skull and 37 vertebrae, of which 30 cervical vertebrae, are an unusually high number for the Polycotylidae.

Genera

• Ceraumasaurus
• Dolichorhynchops
• Edgarosaurus
• Georgiasaurus
• Polycotylus
• Thililua
• Trinacromerum