Cricosaurus
Skull of Cricosaurus suevicus in the State Museum of Natural History Stuttgart.
Cricosaurus is an extinct genus meeresbewohnender crocodile relative from the family of Metriorhynchidae. The genus was described in 1858 by Johann Andreas Wagner basis of three skull finds from the Tithonian ( Upper Jurassic ) of Germany. The term Cricosaurus means " ring lizard" and is derived from the Ancient Greek forth.
Fossil specimens of Cricosaurus have been handed down from the Upper Jurassic of England, France, Switzerland and Germany. In addition, remains in Argentina, in Mexico. been and Cuba, have been found.
History of discovery and classification
Cricosaurus was reclassified from Wagner in 1858, after he had already described another specimen in 1852.
Since then, a number of other species have been named, including C. suevicus by Fraas in 1901, which was previously found to Geosaurus. The originally described by Wagner in 1858 also kind, C. medius, was reclassified later as a junior synonym of Rhacheosaurus gracilis.
The original three skulls, which were all assigned to different species were insufficiently known, so that the genus in the past by various paleontologists was regarded as a junior synonym of Metriorhynchus, Geosaurus or Dakosaurus. Several phylogenetic analyzes could not confirm the monophyly of the genus Cricosaurus. However, a more comprehensive study, in 2009 show that the species of the genus Cricosaurus described were valid and in addition, some species with long snouts, which had previously been classified as the genera Geosaurus, Enaliosuchus and Metriorhynchus belonging, in fact more closely related to the type species of Cricosaurus were. These species were therefore assigned to the genus Cricosaurus.
A total of eight valid species have been described:
- C. elegans (Wagner, 1852) ( type species )
- C. gracilis (Philips, 1871)
- C. macrospondylus ( Koken, 1883)
- C. suevicus ( Fraas, 1901)
- C. schroederi ( Kuhn, 1936)
- C. araucanensis ( Gasparini & Dellapé, 1976)
- C. vignaudi ( Frey et al. 2002)
- C. saltillense ( Buchy et al. 2006)
Enaliosuchus is a synonym of Cricosaurus macrospondylus.
Cladogram after Cau & Fanti (2010).
C. sp.
C. suevicus
C. saltillense
C. elegans
C. vignaudi
C. gracilis
C. araucanensis
C. schroederi
C. macrospondylus
Paleobiology
All currently known species had a length of three meters or less. Compared to recent crocodiles reached Cricosaurus small to medium sizes. The body of the animal was streamlined, and besides, it had a tail fin, making it a more efficient swimmer than modern crocodiles.
Salt glands
Recent studies of the fossil specimens of Cricosaurus araucanensis have shown that both juvenile and adult animals had well-developed salt glands. This means that the animals from birth were able, salt water "drink" and to eat prey, which had the same Ionia concentration, as the sea water surrounding it ( eg cephalopods ) without becoming dehydrated. Adult specimens of Metriorhynchus also had well-developed salt glands.
Niche partitioning
Several types of Metriorhynchidae are from the Moernsheim Formation ( Solnhofen limestone, early Tithonian ) in Bavaria known: Dakosaurus maximus, Geosaurus giganteus, Cricosaurus suevicus and Rhacheosaurus gracilis. It is the thesis have been prepared that ecological niches there several types of crocodile relatives allowed to coexist in the same habitat. The top predators of this formation appear to have been Dakosaurus and G. giganteus, which were very large and occupied with serrated teeth short mouth possessed. The different types of Cricosaurus ate with their long mouths probably mainly of fish, although the lightly built Rhacheosaurus may have specialized on small prey. In addition to these four types of metriorhynchids existed a medium -sized species of Teleosauridae Steneosaurus the same time.
From the Nusplingen Plattenkalk slightly older (upper Kimmeridgian ) in southern Germany are both C. suevicus and Dakosaurus maximus known. As in Solnhofen, C. malnourished suevicus of fish, while Dakosaurus maximus stood at the top of the food chain.
Evidence
- Extinct crocodile
- Crocodilia
- Crocodiles