Archaeothyris
| Archaeothyris | ||||||||||||
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Archaeothyris |
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| Temporal occurrence | ||||||||||||
| Upper Carboniferous ( Moskovium ) | ||||||||||||
| 308 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Archaeothyris | ||||||||||||
| Reisz , 1972 | ||||||||||||
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Archaeothyris is a genus of early synapsid amniotes (" pelycosaurs "). It was discovered in sedimentary rocks of the Upper Carboniferous of Nova Scotia ("Nova Scotia") and represents, with a geological age of around 308 million years, the oldest known undoubted representative of the amniote line of development that leads to mammals .
Etymology and history
The generic name is made up of the ancient Greek words ἀρχαῖος ( archaios , 'ancient', 'original') and θυρίς ( thyris , 'window'), which means something like 'old window'. He refers to the fact that Archaeothyris is the oldest evidence of an amniote with a temporal window . Archaeothyris and its only species A. florensis (the species epithet refers to the location Florence) was named and described in 1972 by the Canadian paleontologist Robert Reisz . The excavations, during which the material was collected, on which the first description of A. florensis is based, were carried out in 1956 under the direction of the famous Alfred Romer .
features
Archaeothyris reached a length of around 50 centimeters and was outwardly similar to a lizard , presumably resembling a modern monitor lizard . His skull is incomplete and has been preserved in individual parts. Nevertheless it could be established with relative certainty that, like the skull of all early synapsids, it had a single temporal window, a. offered more space and attachment surface for the jaw muscles. The muzzle was slender and elongated. The teeth were essentially all of the same shape ( homodontics ), they were small and acutely conical. A pair of large canines in the front part of the upper jaw was noticeable, however . The rest of the skeleton is even less complete.
Way of life
Archaeothyris lived in the tropical coal swamp forests of what is now North America. Its pointy set of teeth indicated that Archaeothyris probably lived predatory and fed on insects or smaller terrestrial vertebrates. The temple window allowed the jaw muscles to be strongly developed and therefore strong enough to generate enough bite and speed force despite a relatively long row of teeth and a large opening angle of the jaws.
Reference
Archaeothyris is so far only known from a single site, an open pit coal mine near Florence on Cape Breton Island ( Nova Scotia , Canada ). The finds come from the layers in the area of the so-called Lloyd Cove coal seam of the Morien group. The Lloyd Cove seam is placed in the lower Westfal D (Des Moines stage of North America, Moskov stage of the international time scale) and is therefore around 308 million years old. At that time the area was characterized by forests and swamps and the climate was warm and humid. The remains of Archaeothyris are preserved in hollow fossilized trunks of club moss trees of the genus Sigillaria . The remains of Paleothyris , one of the oldest known sauropsids and possible prey of Archaeothyris , were also found in the same site .
Systematics
Archaeothyris is considered to be the earliest certain representative of the family Ophiacodontidae , which is one of the most original (“primitive”) families of the synapsids . The original synapsids of the Carboniferous and Early Permian are also called " pelycosaurs ". At 306 million years old, Archaeothyris is not only the oldest ophiacodontid, but also the oldest known representative of all synapsids.
The ophiacodontids are not the most primitive synapsid group and their skulls, including the skull of Archeothyris , have some new features that are not found in the more primitive synapsid groups ( Caseasauria and Varanopseidae ). The oldest finds of these more pristine groups, however, are geologically younger than Archaeothyris . This means that Archaeothyris is the oldest known synapsid, but that even more primitive synapsids must have lived before the Westphalian D. This is supported by the finds of Hylonomus , an original representative of the Sauropsiden, the sister group of the Synapsids, in the Westphalian A of Nova Scotia.
literature
- TS Kemp: The Origin & Evolution of Mammals. Oxford University Press, Oxford 2005. ISBN 0198507615
Individual evidence
- ^ A b Robert R. Reisz: Pelycosaurian Reptiles from the Middle Pennsylvanian of North America. Bulletin of the Museum of Comparative Zoology. Vol. 144, No. 2, 1972, pp. 27-60 ( full text on BHL ).
- ^ Robert Lynn Carroll , Pamela Gaskill: The Order Microsauria. Memoirs of the American Philosophical Society. Vol. 126. The American Philosophical Society, Philadelphia, PA, 1978, ISBN 0-87169-126-4 .