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Triassic is many times called "The Age of Reptiles". During this geological period, reptiles diversified in groups we know today. However there lived some peculiar genera.
Aetosauria[edit]
The only known "armoured reptiles". They were practically identical to ankylosaurs. The name "aetosaur" actually means "eagle lizard", because their skulls resemble those of predatory birds. They lived around the world, but most of their remains are concentrated in USA: New Mexico, Utah[1]
Size[edit]
Aetosaurs ranged in size from the smallest, such as Coahomasuchus or Aetosaurus, that were only 1.5 metres long, to giants such as Desmatosuchus, that was more than 5 metres. However, the average aetosaur size is 3.5 metres.
Armour[edit]
Aetosaurs were very different in shape. Some, like Typothorax and Paratypothorax[2], had turtle-like bodies[3]. Their bodies were usually robust and sturty, while others, like Desmatosuchus, had slenderer body design.
Armour of aetosaurs was embedded in the skin, as in ankylosaurs. However they do not have small osteoderms as dinosaurs do. They had bid bony plates on their backs. This decreased their speed, but increased protection.
Some species also had long shoulder spines (Desmatosuchus is a common example[4].
Posture[edit]
As all modern reptiles aetosaurs were low-browsers. Also they were affected by Carrier's constant. This means that in low-oxygen air they can't breathe and go at the same time. Perhaps, this was the reason for their vanishing during Triassic-Jurassic extinction event.
Phytosaurs[edit]
As most archosaurs they were apex predators of their time[5]. They resembled crocodiles, but had longer snouts and less powerful bites[6].
References[edit]
- ^ Heckert, AB, SG Lucas & JD Harris (1999), An aetosaur (Reptilia: Archosauria) from the Upper Triassic Chinle Group, Canyonlands National Park, Utah, in VL Santucci & L McClelland [eds.], Paleontology of the National Parks, Geologic Resources Division Technical Report NPS/NRGRD/GRDTR-99/03. Washington, D.C.: National Park Service.pp. 23-26
- ^ Long, R. A.; and Ballew, K. L. (1985). "Aetosaur dermal armor from the Late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park". Museum of Northern Arizona Bulletin
- ^ Martz, J.W. (2002). The morphology and ontogeny of Typothorax coccinarum (Archosauria Stagonolepididae) from the Upper Triassic of the American Southwest (M.Sc. thesis). Texas Tech University. http://www.miketaylor.org.uk/dino/nm/Martz2002-thesis.pdf. Retrieved 3 July 2010
- ^ Heckert, A. B.; and Lucas, S. G. (2002). "South American occurrences of the Adamanian (Late Triassic: Latest Carnian) index taxon Stagonolepis (Archosauria: Aetosauria) and their biochronological significance". Journal of Paleontology 76 (5): 852–863. doi:10.1666/0022-3360(2002)076<0852:SAOOTA>2.0.CO;2. http://www.24hourscholar.com/p/articles/mi_qa3790/is_200209/ai_n9124079?pi=scl.
- ^ Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". Bulletin of the American Museum of Natural History 352: 1–292. doi:10.1206/352.1. http://digitallibrary.amnh.org/dspace/bitstream/2246/6112/1/B352.pdf.
- ^ Parker, Bill (27 April 2011). "Dinosaurs Are Crurotarsans". Chinleana. Blogger. http://chinleana.blogspot.com/2011/04/dinosaurs-are-crurotarsans.html. Retrieved 27 April 2011