Ophiacodontidae
| Ophiacodontidae | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Upper Carboniferous to Lower Permian ( Kungurium ) | ||||||||||||
| 311.3 to 272.5 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Ophiacodontidae | ||||||||||||
| Nopcsa , 1923 |
The Ophiacodontidae are a related group of the pelycosaurs , a group of terrestrial vertebrates, which is placed to the synapsids . They were at least partially aquatic animals that ate meat and possibly fish. The Ophiacodontidae family existed from 311 to 273 million years ago.
features
The main feature of the Ophiacodontidae was their primary cranial window in the temple region (temple or temporal window) behind the eye socket.
Her skull was elongated, in later members of the group it was huge and massive compared to the body. The base of the skull was relatively deep. The frame around the eye socket was very high on the skull. The bones of the brain skull were generally less fused together than in other Eupelycosauria .
The pointed snout contained numerous (more than 40) uniform ( homodontal ) teeth that were small and pointed and suitable for grasping prey. A well-formed mandibular window sat in a notch in the lower jaw. There was a protruding protrusion on the upper jaw above the canines . The tear bone was elongated. The postdorsal processes of the premaxilla were elongated and thin, separated from the anterior process of the nasal bone at the midline. The Angular had a well developed ventral keel. The lower edge of the postorbital skull was concave and enclosed the zygomatic bone . The tabular showed a large medial extension.
The shoulder and pelvic girdles were well developed, the fingers were flattened and used in some modes of movement in the water, and the carpal and tarsal bones were only slightly ossified.
Ophiacodontidae had long tails. The vertebral bodies were shorter than those of the Sphenacodontidae and Edaphosauridae .
The Ophiacodontidae varied considerably in size. While early representatives were only around 50 centimeters long, later genera such as Ophiacodon reached up to 4 meters in length.
Autapomorphies
The ophiacodontidae were characterized by the following autapomorphies from
- The antorbital area of the skull was twice as long as that behind the eye socket (in other synapsids it is considerably shorter).
- The nasal bone was longer than the frontal bone and almost twice as long as the parietal bone (it is shorter in other synapsids).
- The paraoccipital process on the occiput was short and did not reach the zygomatic bone (in other synapsids it is longer and reaches the square or scale bone ).
- The tabular expanded in the ventral direction only to the supraoccipital (in other synapsids it extends much further down).
Occurrence and spread
The earliest representative of this group was Archaeothyris , which is also the oldest animal that undoubtedly belongs to the synapsids . He lived in the Pennsylvania ("Upper Carbon", Wende Moskovian / Kasimovian ) about 311 to 305 million years ago. Fossil evidence of this genus has been found in the Morien Group in the Canadian province of Nova Scotia .
Also Clepsydrops was an early genus of ophiacodontidae. The eponymous genus Ophiacodon is occupied by several species from the late Carboniferous and Lower Permian .
In the Middle Permian ( Artinskian ) the Ophiacodontidae became extinct.
Locations
Fossils of these animals are so far mostly only from North America demonstrates the exception of Stereorhachis that only in Europe occurs and ophiacodon that may occur in Europe.
North America:
- Canada :
- United States :
Europe:
Way of life
The fact that the Ophiacodontidae were semi-aquatic fish-eaters is not recognized by all scientists (see for example Reisz).
Systematics
The Ophiacodontidae, together with the Edaphosauridae and the Sphenacodontia (which included Dimetrodon ), form a common taxon that is characterized by various features in the structure of the skull. This taxon is further developed within the Pelycosaurier in contrast to the Caseidae or Varanopseidae . Nevertheless, the oldest known synapsid, Archaeothyris, is also classified in the Ophiacodontidae. The exact lineages within these animals have therefore not yet been clarified beyond doubt.
According to Carroll (1988) the following genera are assigned to the Ophiacodontidae:
- Archaeothyris Reisz, 1972 (Middle Pennsylvania)
- Baldwinonus Romer & Price, 1940 (early Permian)
- Clepsydrops Cope 1875 (late Pennsylvania)
- Ophiacodon Marsh 1878 (late Pennsylvania and early Permian)
- Protoclepsydrops (Early Pennsylvania) - Controversial. If recognized, this taxon would be the oldest known synapsid.
- Stereophallodon Romer 1937 (early Permian)
- Stereorhachis Gaudry 1880 (late Pennsylvania)
- Varanosaurus Broili 1904 (Early Permian) - disputed
Archaeothyris
Ophiacodon retroversus
literature
- Robert L. Carroll: Vertebrate Paleontology and Evolution , WH Freeman & Co., New York 1988. ISBN 0-7167-1822-7
- TS Kemp: The Origin & Evolution of Mammals. Oxford University Press, Oxford 2005. ISBN 0-19-850761-5
- Michael J. Benton : Paleontology of the vertebrates . Publishing house Dr. Friedrich Arrow. Munich, 2007 ISBN 3-89937-072-4
Individual evidence
- ↑ Autapomorphies in the main groups of synapsids
- ↑ Reisz, RR & Berman, VS (1986), Ianthosaurus hardestii n. Sp., A primitive ephadosaur (Reptilia, Pelycosauria) from the Upper Pennsylvanian Rock Lake Shale near Garnett, Kansas. Can. J. Earth Sci. 23: 77-91.
