Henodus

Fossil of Henodus chelyops in the Paleontological Collection of the University of Tübingen

• Southern Germany

Henodus is a genus of living amphibian reptile from the group of Placodontia from the early Carnian ( Upper Triassic ) of Europe. Fossils of Henodus were found in gypsum deposits of the Keuper, the uppermost of the three lithostratigraphic groups of the Germanic Triassic, in Tübingen -Lustnau in southern Germany. The only known species is Henodus chelyops ( " schildkrötenkopfiger single tooth ").

Features

Henodus was about a meter long and had a wide, very flat body. His skull was broad and nearly rectangular, the eyes and the nostrils stood close together, near the front close to the tip of the snout. Viewed from the side of the front head is bent downward, so that the eyes and nose openings face forward. The dentition was reduced to a pair of teeth on the back of the palate bone and one in the lower jaw. Along the edges of the upper and lower jaw, there are groove-like depressions in which possibly horny pine strips similar to the turtles or beard -like growths were anchored. The premaxillary bones ( premaxilla ) had a downward, sharp outgrowth, who owned a series of tooth-like denticles on its outer edge. The lower jaw was strongly built, but the low ramus shows that the bite of Henodus was not as strong as the other Placodontier. The visible to the bone muscle insertions indicate that the jaw muscles was adapted quickly to open their mouths, while the large hyoid speaks for an extensible throat. Roughly triangular scales, the number and shape differ individually, can be found on the rear edge of the skull. While the pace Supra Ralf Rochester, the upper cranial window is normally developed in the temporal region, in other Placodontiern, it was secondarily closed at Henodus, so that the skull as that of the turtles is closed and has no windows. The turtle -like armored hull of Henodus roughly corresponded to that of Cyamodus, the tank was only much broader. It was formed by a mosaic of numerous, polygonal osteoderms, which were apparently covered by an epidermal layer. The trunk vertebrae were fused to the tanks and reduced in number. In addition, the sides were protected and a plastron ( plastron ) was present.

Way of life

Fossils of Henodus come from lagoonal deposits that formed under brackish or freshwater conditions. This Henodus is the only known Placodontier from a non-marine ecosystem. Previously it was assumed that Henodus like other Placodontier of crustaceans lived. Because of its jaw anatomy is rather assumed today that Henodus was a filter feeder, the filtered bodenbewohnede invertebrates from the mud or fed on floating invertebrates such as jellyfish. Maybe he had to scrape algae or other vegetation of rocks in the situation, with occupied with tooth-like denticles premaxilla.

System

Henodus 1936 was described by German paleontologist Friedrich von Huene vertebrate scientifically for the first time, in his time the leading expert on fossil reptiles in Europe. The Placodontier ( plaster tooth lizards ), in which this species is found are among the Sauropterygia ( " lizard flippers "). Within the Placodontia Henodus is placed in the monotypic family Henodontidae and is most closely related to Cyamodus. Along with this is the group of Henodus Cyamodontida within the Placodontia.