Polycotylidae
| Polycotylidae | ||||||||||||
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Live reconstruction of Edgarosaurus |
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| Temporal occurrence | ||||||||||||
| Cenomanium to Campanium ( Upper Cretaceous ) | ||||||||||||
| 99.6 to 70.6 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Polycotylidae | ||||||||||||
| Williston , 1909 |
The Polycotylidae ( synonyms : Dolichorhynchopidae, Trinacromeridae) are a family of Plesiosauria that was widespread worldwide in the Cretaceous Period . They are best known for partially and completely preserved skeletons from the Upper Cretaceous in North America. More fragmented fossils, 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 of the Polycotylidae were medium-sized, with the largest reaching nine meters in length. Compared to the length of the skull, they had a very elongated snout (rostrum) formed by long and slender premaxillaries and maxillaries . The premaxillary formed the anterior and upper borders of the nostrils, the maxillary formed the lower border. The premaxillary was elongated on top and met the parietal between the bony eye sockets . A thin ploughshare separated the premaxillary from a V-shaped slit that was perhaps the seat of a Jacobsonian organ . A tear bone was missing. The browbone delimited the top of the eye sockets and formed a bony eyebrow. The skull windows were very large and restricted the parietal to a high crest that covered the skull. The teeth were small and uniform. The replacement teeth grew in pits between the teeth in use.
Overall, their skulls resemble that of the ichthyosaurs . As they are mainly known from the late Cretaceous, they could have taken over the ecological niche of the ichthyosaurs after their extinction as fast-swimming hunters of small fish and cephalopods . Ammonite pine was found in their stomach region .
The Polycotylidae had 19 to 26 cervical vertebrae, about 20 trunk vertebrae and about 24 vertebrae supported the tail. The shoulder blades were separated by the arched collarbone. The pelvis was large, the ischium long. The humerus and femur were the same size. The outer bones of the limbs were very small.
Systematics
Most Polycotylidae resembled the pliosaurs to which they were counted first , with their short necks and elongated snouts . However, they shared some characteristics with the Cryptoclididae and the Elasmosauridae and thus belong to the plesiosaurs ie S. (Plesiosauroidea). These features included the shortness of the skull region behind the eye, the large eye sockets, the narrow snout, the small teeth, the crest of bone over the skull, and the shortness and width of the humerus and femur.
The fossil of Thililua, a polycotylid newly described in 2003, consists of the skull and 37 vertebrae, 30 of which are cervical vertebrae, an unusually high number for the Polycotylidae.
Genera
- Ceraumasaurus
- Dolichorhynchops
- Edgarosaurus
- Georgiasaurus
- Mauriciosaurus
- Polycotylus
- Thililua
- Trinacromerum
Individual evidence
- ↑ a b c d Pterosauria Translation and Pronunciation Guide by Ben Creisler ( Memento from November 9, 2007 in the Internet Archive )
- ^ A b Richard Ellis : Sea Dragons. Predators of the Prehistoric Oceans. University Press of Kansas, Lawrence KS 2003, ISBN 0-7006-1269-6 , p. 192.
- ↑ a b Palæos Polycotylidae
- ↑ Plesiosauria.com Polycotylidae ( Memento of the original from July 16, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Nathalie Bardet, Xabier Pereda Suberbiola, Nour-Eddine Jalil: A new polycotylid plesiosaur from the Late Cretaceous (Turonian) of Morocco. In: Comptes Rendus Palevol. Vol. 2, No. 5, 2003, ISSN 1631-0683 , pp. 307-315, doi : 10.1016 / S1631-0683 (03) 00063-0 .
