Aegisuchus
| Aegisuchus | ||||||||||||
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The holotype of Aegisuchus witmeri , a skull fragment in different views |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous ( Cenomanium ) | ||||||||||||
| 98 to 93 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Aegisuchus | ||||||||||||
| Holliday & Gardner , 2012 | ||||||||||||
| species | ||||||||||||
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Aegisuchus witmeri is an extinct species of archosaurs . The only known representative of the genus Aegisuchus was a very large crocodile relative with a flat head, strong jaw and head shield. In the late Cretaceous period he lived in what is now Morocco in a swampy area, where he possibly ate fish.
Aegisuchus witmeri was first described by Casey Holliday and Nicholas Gardner in 2012 . Together with the genus Aegyptosuchus , Aegisuchus is part of the family Aegyptosuchidae , the sister group of the crocodiles (Crocodylia). The presence of aegisuchus - fossils in the Upper Cretaceous of North Africa presents hypotheses in question, after which the modern crocodiles in Laurasia have developed.
features
Aegisuchus was a very large crocodile relative with an estimated body length of about 15 m. The length of the skull was between 2.1 and 2.9 m. According to the underlying model calculations, Aegisuchus was not only larger than Purussaurus , Sarcosuchus or Deinosuchus , it also had the largest brain of all known species with a volume of 40 cm³. However, since the estimated length is based on the brain volume, it is also possible that Aegisuchus was smaller than expected and only had a disproportionately large brain.
At the back of his head, Aegisuchus had a wrinkled head shield made of heavily thickened skin. In the neck it formed a transition to the back and had two finger-like extensions on the sides. Its function is believed to be in courtship rituals and exhibition fights. The muzzle and skull were severely flattened; Aegisuchus probably had a very flat upper jaw, the shape of which resembled a duck's beak . The eyes had no bulges, but lay flat in the skull. Due to the shape of the head and snout, the animals had relatively strong jaw and neck muscles. They allowed Aegisuchus to move their head relatively generously.
Diffusion and Stratigraphy
Aegisuchus has so far only been found in the North African Kem-Kem Formation in southeast Morocco . The formation comes from the Upper Cretaceous Cenomanium ; the stratum in which Aegisuchus was found is 93 to 98 million years old.
ecology
The habitat of Aegisuchus was an extensive swamp landscape along a river. The waters and the adjacent areas were inhabited by numerous different species of fish, amphibians and larger reptiles such as plesiosaurs , theropods and sauropods . As with the morphologically similar genera Laganosuchus and Stomatosuchus , it is also assumed that Aegisuchus mainly fed on lazy fish such as coelacanth , lungfish or pike fish . Terrestrial vertebrates may also have made up part of the diet as occasional prey.
Systematics
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The genus Aegisuchus was established in 2012 by Casey Holliday and Nicholas Gardner with A. witmeri as the only species. The holotype ( ROM 54530), a partially preserved cranium , was found by commercial fossil collectors in the Kem-Kem Formation and sold to the Royal Ontario Museum in Toronto . Holliday and Gardner chose the generic name (aegis, Greek for shield; souchus, Greek for crocodile) based on the animal's head shield. The specific epithet honors Lawrence M. Witmer for his contribution to the study of the skull anatomy of archosaurs .
The two authors classified Aegisuchus due to its head shield as a sister taxon of the likewise Cenomanian genus Aegyptosuchus from the Egyptian Bahariija formation . Both genera together form the family Aegyptosuchidae , an assessment that was supported by a morphological analysis of 45 Crocodyliformes taxa. Accordingly, Aegisuchus and Aegyptosuchus together form the sister group to the modern crocodiles (Crocodylia). The existence of such a modern group of crocodile relatives contradicts hypotheses that assume the origin of the recent crocodiles in western Laurasia (now North America). Instead, they make a radiation in the area of the Tethys Sea appear plausible.
literature
- L. Cavin, H. Tong, L. Boudad, C. Meister, A. Piuz, J. Tabouelle, M. Aarab, R. Amiot, E. Buffetaut, G. Dyke, S. Hua, J. Le Loeuff: Vertebrate Assemblages from the Early Late Cretaceous of Southeastern Morocco: An Overview. In: Journal of African Earth Sciences 57, 2010. doi: 10.1016 / j.jafrearsci.2009.12.007 , pp. 391-412. ( Full text )
- Casey M. Holliday, Nicholas M. Gardner: A New Eusuchian Crocodyliform with Novel Cranial Integument and Its Significance for the Origin and Evolution of Crocodylia . In: PLOS ONE . tape 7 , no. 1 , 2012, p. e30471 , doi : 10.1371 / journal.pone.0030471 , PMID 22303441 (English).
Web links
Individual evidence
- ↑ Holliday, Gardner : PLOS ONE. 2012, p. 4.
- ↑ Holliday, Gardner : PLOS ONE. 2012, pp. 4–8.
- ^ A b Holliday, Gardner : PLOS ONE. 2012, p. 1.
- ↑ Cavin et al. : Journal of African Earth Sciences. 57, 2010, pp. 395-399.
- ↑ Holliday, Gardner : PLOS ONE. 2012, pp. 9-10.
- ^ A b Holliday, Gardner : PLOS ONE. 2012, p. 2.
- ↑ Holliday, Gardner : PLOS ONE. 2012, p. 11.