Archaeothyris

Archaeothyris

• Cape Breton Island ( Nova Scotia, Canada)

• Archaeothyris florensis

Archaeothyris is a genus previously synapsider amniotes ( " Pelycosaurier "). It was discovered in sedimentary rocks of the Upper Carboniferous of Nova Scotia ( " Scotia " ) and represents, with a geological age of about 306 million years, the previously oldest known unequivocal representatives of those amniotes development line leading to mammals.

Etymology and history

The genus name is derived from the ancient Greek words ἀρχαῖος ( archaios, ancient ',' original ') and θυρίς ( thyristor, ' window ' ), thus means something like, old window '. It refers to the fact that Archaeothyris is the oldest evidence of amniotes with temporal window. It was named and described Archaeothyris and whose only species A. florensis ( the kind epithet refers to the locality Florence ) in 1972 by Canadian paleontologist Robert Reisz. The excavations, in which the material was collected, to which the first description of A. florensis based, but have been carried out in 1956 under the leadership of the famous Alfred Romer.

Features

Archaeothyris reached a length of about 50 centimeters and was outwardly similar to a lizard, probably resembled a modern-day lizard away. His skull is preserved only incomplete and unassembled. Nevertheless, it was found relatively reasonable doubt that he, like the skull of all early synapsids, a single temporal window having that offered more space and approach area for the jaw muscles and others. The snout was slender and elongated. The teeth showed essentially all the same shape ( Homodontie ), they were small and pointed cone. However, was striking a pair of large canine teeth in the front of the upper jaw. The rest of the skeleton is obtained or incomplete.

Way of life

Archaeothyris lived in the tropical coal - swamp forests of present-day North America. His teeth with pointy teeth showed that Archaeothyris probably predatory lived and fed on insects and small terrestrial vertebrates. The temporal window allowed that the jaw muscles strongly developed and so was strong enough, despite a relatively long row of teeth and a large opening angle of the jaw to generate sufficient biting and explosive strength.

Reference

Archaeothyris is only known from a single locality, a coal mining in Florence in Nova Scotia ( eastern Canada ). The findings come from the layers in the region of the so-called Lloyd Cove coal seam of the Morien Group. The Lloyd Cove seam is placed in the lower Westphalian D (Des -Moines - stage in North America, Kasimov stage of the international time scale) and is thus about 306 million years old. The area was then dominated by forests and wetlands and the climate was warm and humid. The remains of Archaeothyris are preserved in the hollow trunks of fossil club moss trees of the genus Sigillaria. In the same reference the remains of Paleothyris, one of the oldest known sauropsids and possible prey of Archaeothyris were found.

System

Archaeothyris is the earliest representative of the safer Ophiacodontidae family, where it is one of the original ( " primitive " ) families of synapsids. The original of the Carboniferous and early Permian synapsids are also called " Pelycosaurier ". With 306 million years Archaeothyris is not only the oldest but also Ophiacodontide the oldest known representatives of all synapsids.

The Ophiacodontiden are not the most original Synapsidengruppe and their skulls, including the skull of Archeothyris, have some new features that are not found in the more primitive Synapsidengruppen ( Caseasauria and Varanopseidae ). However, the oldest finds of these primitive groups are geologically younger than Archaeothyris. This means that although Archaeothyris is the oldest known Synapside, but that still more original Synaspsiden must have lived before the Westphalian D. This is supported by the findings of Hylonomus, an original representative of sauropsids, the sister group of synapsids, the Westphalian A of Nova Scotia.