Юра :

Интересно было бы узнать, кто это :

http://s53.radikal.ru/i142/0810/d6/ea75d963716f.jpg

Ага, точно Psephoderma alpinum, этот же экземпляр, длиной около 1,2 м, вид снизу


А этот побольше - 1,8 м, вид сверху


http://dipbsf.uninsubria.it/paleo/psephoderma1.htm

Вот Cyamodus

а вот Sinocyamodus

Glyphoderma kangi Zhao et al., 2008 (средний триас, провинция Юньнань, Китай)


A new armored placodont from the Middle Triassic of Yunnan Province, southwestern China

Placodont (Reptilia: Placodontia) from Upper Triassic of Guizhou, Southwest China

парочка работ посвященных сравнению плакодусов с сиренами:

A. Immigration of the “Triassic sea cows” Paraplacodus, Placodus and Cyamodus into the Germanic Basin and (B) distribution during Lower Muschelkalk times. C. With the Middle Muschelkalk regression placodontid populations must have been reduced. D. In the Upper Muschelkalk reptile bones were found all over the Basin, but the only articulated Placodus skeleton was discovered in fully marine deposits at Steinsfurt. Paraplacodus and Cyamodus skeletons are known from Monte San Giorgio

Palaeoecology of Placodus gigas (Reptilia) and other placodontids — Middle Triassic macroalgae feeders in the Germanic Basin of central Europe — and evidence for convergent evolution with Sirenia
http://www.sciencedirect.com/science/ar … direct.com.abstract

Fossil middle triassic “sea cows” – placodont reptiles as macroalgae feeders along the north-western tethys coastline with pangaea and in the germanic basin.pdf

Отредактировано zamolksis (14 November 2012 00:23:30)

Palaeoecology of Placodus gigas (Reptilia) and other placodontids — Middle Triassic
macroalgae feeders in the Germanic Basin of central Europe — and evidence for
convergent evolution with Sirenia   http://libgen.org/scimag4/10.1016/j.pal … 11.021.pdf   

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...Placodonts have a unique tooth replacement pattern and results follow a phylogenetic trend. The plesiomorphic Placodus species show many replacement teeth at various stages of growth, with little or no discernible pattern. On the other hand, the more derived cyamodontoids tend to have fewer replacement teeth growing at any one time, replacing teeth unilaterally and/or in functional units, thus maintaining at least one functional crushing area at all times. The highly derived placochelyids have fewer teeth and, as a result, only have one or two replacement teeth in the upper jaw. This supports previous suggestions that these taxa had an alternative diet to other placodonts. Importantly, all specimens show at least one replacement tooth growing at the most posterior palatine tooth plates, indicating increased wear at this point and thus the most efficient functional crushing area.

• Neenan J. M. et al. (2015): Unique method of tooth replacement in durophagous placodont marine reptiles, with new data on the dentition of Chinese taxa .pdf
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Отредактировано zamolksis (31 December 2015 00:36:39)