Sonntag, 10. April 2011

A palaeodictyopteran and other relics from Madygen

Béthoux, O., S. Voigt, and J. W. Schneider. 2010. A Triassic palaeodictyopteran from Kyrgyzstan. Palaeodiversity 3: 9-13. [pdf 1.5 Mb]

Despite the substantial collection and study of insect fossils from the Madygen Formation (see overview in Shcherbakov 2008a) there are still unkown elements of the entomofauna left. Béthoux et al. (2010) describe a wing of a not yet reported group of insects from lacustrine shales of the northwestern ouctrop area of the Madygen Fm. (which also yielded Sharovipteryx and Longisquama).

Ruling out all alternatives on the basis of wing venation data, they come to the conclusion that reliquia spec. nov. was a late member of Palaeodictyoptera, an order-rank group according to conventional classification schemes that was previously thought to have died out during the Middle or Late Permian.

Béthoux et al. suggest that the disappearance of ancient insect groups in equatorial realms is linked to the Late Paleozoic aridisation in these areas that triggered the migration to wetter higher latitude ecosystems, such as the Madygen lake environment. The relatively late occurence of paleodictyopterans in Madygen is also in agreement with Shcherbakov's (2008b) hypothesis that the renewal of Triassic entomofaunas was asynchronous, starting in the lower latitudes and spreading to the higher latitudes.

Other Madygen relics?

Apart from modern groups, such as dipterans and hymenopterans among insects as wells as lissamphibians and archosaurs among tetrapods there are further relict forms, such as the choniosuchian Madygenerpeton or the basal cynodont Madysaurus. As hinted by Béthoux et al. the question to what degree and why Madygen functioned as a refugium is still to be answered.