Henodus
Henodus | ||||||||||||
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Fossil of henodus chelyops in the Palaeontological Collection of the University of Tuebingen |
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Temporal occurrence | ||||||||||||
Carnium (Upper Triassic) | ||||||||||||
235 to 228 million years | ||||||||||||
Locations | ||||||||||||
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Systematics | ||||||||||||
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Scientific name of the family | ||||||||||||
Henodontidae | ||||||||||||
Huene , 1948 | ||||||||||||
Scientific name of the genus | ||||||||||||
Henodus | ||||||||||||
Huene, 1936 |
Henodus is a genus of amphibious reptiles from the Placodontia group from the early Carnian ( Upper Triassic ) of Europe. Fossils of henodus were in gypsum deposits of the Keuper , the highest of the three lithostratigraphic groups of Germanic Trias , in Tuebingen - Lustnau found in southern Germany. The only known species is Henodus chelyops ("turtle-headed one-tooth").
features
Henodus was about three feet long and had a broad, very flat body. His skull was broad and almost rectangular, the eyes and nostrils were close together, near the tip of the snout. Viewed from the side, the front skull is bent downwards so that the eyes and nostrils point forward. The dentition was reduced to one pair of teeth on the posterior palatine bone and one in the lower jaw. Along the edges of the upper and lower jaw there are channel-like depressions in which horny jaw ridges similar to that of turtles or whiskers were anchored. The intermaxillary bone (premaxillary) had a downwardly directed, sharp-edged outgrowth, which had a series of tooth-like denticles on its outer edge . The lower jaw was strongly built, but the low branch of the lower jaw shows that Henodus' bite was not as strong as that of other placodon animals. The muscle attachments visible on the bones indicate that the jaw muscles were capable of opening the mouth quickly, while the large hyoid bone suggests an expandable throat. Approximately triangular scales, the number and shape of which differ individually, are found on the rear edge of the skull. While the supratemporal window, the upper cranial window in the temporal region, is normally developed in other placodont animals, in Henodus it was closed secondarily, so that the skull, like that of the turtles, is closed and windowless. The turtle-like armored hull of Henodus was roughly the same as that of Cyamodus , the carapace was only much wider. It was formed by a mosaic of numerous, polygonal osteoderms , which were apparently covered by an epidermal layer. The torso vertebrae were fused with the armor and reduced in number. In addition, the sides were protected and a belly armor (plastron) was available.
Way of life
Henodus fossils come from lagoon deposits formed in brackish or fresh water conditions. This makes Henodus the only known placodon animal from a non- marine ecosystem . It was previously believed that Henodus, like other placodon animals, lived on crustaceans. Because of its jaw anatomy, it is now more likely that Henodus was a filter feeder , filtering bottom -dwelling invertebrates out of the mud or feeding on swimming invertebrates such as jellyfish . Possibly he was also able to scrape algae or other vegetation from rocks with the premaxillary covered with tooth-like denticles.
Systematics
Henodus was first described scientifically in 1936 by the German vertebrate paleontologist Friedrich von Huene , the leading expert on fossil reptiles in Europe at the time. The Placodontier (plaster tooth lizards), in which this genus is placed, belong to the Sauropterygia ("fin lizards"). Within the Placodontia, Henodus is placed in the monotypic family Henodontidae and is closely related to Cyamodus . Together with this, Henodus forms the group of Cyamodontida within the Placodontia.
literature
- Robert L. Carroll : Paleontology and Evolution of the Vertebrates. Thieme, Stuttgart et al. 1993, ISBN 3-13774-401-6 .
- Cajus G. Diedrich: Fossil middle triassic "sea cows" - placodont reptiles as macroalgae feeders along the north-western tethys coastline with pangea and in the germanic basin. In: Natural Science. Vol. 3, No. 1, 2011, ISSN 2150-4091 , pp. 9-27, doi : 10.4236 / ns.2011.31002 .
- Walter Fischer: About new dinosaur finds in Lustnau. . In: Tübinger Blätter. Vol. 42, 1955, ISSN 0930-3642 , p. 21, digitized .
- Darren Naish: Fossils explained 48: Placodonts. In: Geology Today. Vol. 20, No. 4, 2004, ISSN 0266-6979 , pp. 153-158, doi : 10.1111 / j.1365-2451.2004.00470.x , online .
Web links
- Henodus in The Paleobiology Database.
- Henodus chelyops , Huene 1936 in Palaeos.com
- Henodus , filter-feeding Triassic marine reptile article by Darren Naish at scienceblogs.com
- Live reconstruction in Dinosoria.com