Morganucodon
| Morganucodon | ||||||||||||
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Live reconstruction |
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| Temporal occurrence | ||||||||||||
| Upper Triassic to Lower Jurassic | ||||||||||||
| 205 to 190 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Morganucodon | ||||||||||||
| Kühne , 1949 | ||||||||||||
Morganucodon is one of the oldest representatives of mammals or mammalian-like animals ( Mammaliaformes ). The small animal lived in the Upper Triassic and Lower Jurassic and is known from Western Europe, China and North America.
description
Morganucodon was about 10 centimeters long and should have resembled a shrew on the outside. In its physique it shows some transitional features between the synapsid mammalian ancestors and the actual mammals. It had a double temporomandibular joint, in addition to the secondary temporomandibular joint typical of mammals , the reptilian primary temporomandibular joint is also present between the articular and quadratum bones. The lower jaw also consisted of several bones.
On the other hand, the four different types of teeth and the one-time change of teeth were typical of mammals. Morganucodon had four incisors per jaw , the canines were medium-sized. There were five upper and four lower premolars and three molars in each half of the jaw . These each had three sharp cusps that fit well with the opposing teeth ( occlusion ).
The rest of the physique indicates a nimble, ground-dwelling animal. The diet probably consisted of insects and other small animals.
Discovery and systematics
From 1949 on, numerous teeth, jaws and other fossils were found in Glamorgan (Wales), which for the first time provided evidence of early mammals. The name Morganucodon was coined for these finds ; it is derived from the Latinized Welsh name of Glamorgan, Morgannwg, and the Greek word for tooth ( odon ). As early as 1941, two isolated teeth of a genus that were initially called Eozostrodon were discovered in Somerset (England) . Presumably it is the same genus, but since the individual teeth were insufficient for a description, the name Morganucodon is preferred today . Later finds were found in other places in Western Europe as well as in China and North America.
On the basis of preliminary work by the geologist Ferdinand Schalch , Bernhard Peyer began excavations in Hallau in 1942 , and the animal's teeth were found; William A. Clemens was able to fully identify them in 1978/79 .
Morganucodon is classified with some related genera in the group of Morganucodonta , which occurred almost worldwide from the Upper Triassic to the Lower Jurassic. Whether this group is already classified in the mammals in the broader sense ( sensu lato ) or in the mammal-like animals ( Mammaliaformes ) is controversial and largely a question of definition. In any case, they already showed advanced mammal-like features, but still differed in details from today's mammals.
literature
- Thomas S. Kemp: The Origin & Evolution of Mammals . Oxford University Press, Oxford 2005, 331 pages, ISBN 0-19-850761-5 .