Helveticosaurus
The holotype of Helveticosaurus - zollingeri in Zurich Paleontological Museum
- Monte San Giorgio ( Switzerland )
- Helveticosaurus zollingeri Peyer, 1955
Helveticosaurus is a fossil genus wasserbewohnender reptiles. Helveticosaurus was a kurzschnäuziges reptile with long, sharp teeth, and elongated body. All findings are from the bitumen layers of Swiss Monte San Giorgio, which are dated to the Middle Triassic Anisian or Ladinian and thus are approximately 242 million years old. Helveticosaurus inhabited a shallow shelf sea, where he may stalked fish and mollusks. His body had adapted to life in water, but also allowed ashore.
The only species of the genus, Helveticosaurus zollingeri, was discovered in the 1930s in the Swiss Ticino and described in 1955 by Bernhard Peyer. He arranged to Placodontiern, meanwhile Helveticosaurus but is considered Archosauromorpher with unclear relationships.
- 5.1 Literature
- 5.2 External links
- 5.3 Notes and references
Features
Helveticosaurus zoellingeri was approximately 2 m long. The species had a short, compressed by the high muzzle acting skull. The mandible, which probably corresponded to the entire skull in length, measured 21.5 cm. The jaws were covered with long, slightly curved teeth. The teeth were blunt at the tip and had no sharp edges on. In the front part of the upper jaw H. zollingeri had a significantly longer tooth, which is reminiscent of the canine teeth of predators. The gear change took place from the outside to the inside, a variant that is more the exception among reptiles and otherwise known only from ichthyosaurs, snakes and crocodiles. Helveticosaurus zollingeri had at least 40 lying in front of the sacral vertebrae. The ribs of the chest increased in size from front to back to the tail had at least at the base of ribs. About the sturdy shoulder belt of the type can not make reliable statements because it is not, or only very fragmented preserved in the fossils found so far. Previously drawn comparisons to Placodus gigas can not be maintained likely. The Interclaviculum was probably around 130 mm wide, the clavicles had approximately the same length. The shoulder blades were arranged approximately at right angles to Interclaviculum and about 190 mm high. The hip bones were not built particularly strong for an animal of this size. Foot and wrist were greatly reduced. Both the front and the rear feet reported additional phalanges ( Hyperphalangie ) on: The Phalangenformel the front feet was at least 2-3-4-6-3, so they had compared to the original Phalangenformel the Archosauromorpha ( 2-3-4-5 - 4) at least one additional element. In the hind feet the Hyperphalangie was even more pronounced here dismissed the second toe at least five, the four outermost toes together at least 19 members on what compared to the original formula, three or more additional members. The feet were probably transformed into fins.
Localities and stratigraphy
All finds of Helveticosaurus come from the Besano lineup of Monte San Giorgio on the southern shore of Lake Lugano. This is also known as bitumen zone boundary layer originates from the transition between the late Anisian and early Ladinian and has an estimated age of about 242 million years. Bernhard Peyer rule out any amount exceeding this locality distribution, since localities of similar age and similar facies world's rare and findings are unlikely elsewhere for this reason.
Way of life
The development of additional phalanges in Helveticosaurus is typical of aquatic tetrapods and indicates an aquatic lifestyle and locomotion of Helveticosaurus. Its habitat was a shelf sea of Tethys. Since the skeleton neither a special adaptation to rowing showed for some undulations to Helveticosaurus move likely to continue with a mixture of both types. The robust shoulder girdle indicates that the type occasionally went ashore, where especially the forelimbs bore the weight of the body. A strong muscling, especially of the neck allowed the animals to raise his head to land on the ground. Bernhard Peyer suspected that Helveticosaurus went about to lay their eggs on land. His tooth shape he interpreted as an adaptation to a predatory diet. As prey sharks and Knorpelganoide, but especially mollusks such as belemnites had come into question.
Taxonomy and Research History
Fund History and Description
From Helveticosaurus been three fossils were discovered. The first specimen was recovered in 1933 in the gallery Arnaldo in the Cava Tre Fontane, where the bitumen of the Fund layer was then removed industrially. This first fossil comprised a relatively complete, but highly fragmented skeleton of Helveticosaurus. The disorder among the fossil bone was mainly before the sedimentation of the carcass through processes of decay. Later tectonic layer and compressive forces contributed by the fossilization to a further deformation at. The host rock of the fossils - dolomite - proved difficult to prepare, which is why the scientific description of the findings went. Two years later it was found in the same place another fossil that was far better preserved: The bone formation was largely intact, though the skull was smashed and the tail of the animal was missing the rear end. The Swiss paleontologist Bernhard Peyer chose this fossil as holotype for his first description, but this had to revise again, as in 1937 an excavation, a snout fragment of the same kind appeared. After extensive preparation a piece of the maxilla with a number of teeth could be reconstructed.
In 1955 appeared the first description of the genus and the type species Helveticosaurus Helveticosaurus zoellingeri under the title The Triassic fauna of the Ticino Alps. XVIII. Helveticosaurus zoellingeri ngn sp., It was the Swiss Palaeontological it printed treatises one years in the band 72. Peyer chose Helveticosaurus as a generic name to express the Swiss origin of the reptile ( Helvetia ). The specific epithet honors zollingeri Walter Zollinger, the Board President of the Georges- and - Antonia - Claraz - donation, which had financed the scientific exploration of the Monte San Giorgio significantly since 1924.
System
Bernhard Peyer classified Helveticosaurus in its first description as a very basal ( original ) Representatives of Placodontia, a group within the fin lizards ( Sauropterygia ). Peyer put on a new submission within the Placodontia, those who Helveticosaurus contained " Helveticosauroidea " as a single representative. Recent studies have come to the conclusion that this species is not likely attributable to Placodontia. Instead, it could be an early and unusual representative of Archosauromorpha.