Prehistorische roofvogel met giftanden ontdekt

[Two-of-2 Profiel]

prehistorische roofvogel met giftanden ontdekt

AMSTERDAM – Amerikaanse wetenschappers hebben giftanden ontdekt in een fossiel van een prehistorische roofvogel die ongeveer 128 miljoen jaar geleden in China leefde.

[Peter S Profiel]

Gezien de verwantschap tussen vogels en reptielen en de gezamelijke afstamming van de eerste dino's is dat eigenlijk niet zo verwonderlijk..

[Peter S Profiel]

What all this means is that the dogma on the Discovery Channel about toxic bacteria being responsible for the bite effects produced by Komodo Dragons (and other monitor lizards) has been wrong. Its been a venom all this time!

In the course of this study, we worked out that snakes and lizards share a common venomous ancestor, rather than venom evolving independently. As part of this, we showed that the iguanian lizards retain the very very primative form of the venom glands, as shown by this picture of the Eastern Bearded Dragon

In constrast, the varanids have developed the lower jaw gland into a very complex venom gland. It is hollow, stores liquid venom and there are garden hose like ducts leading to the big teeth on the lower jaw. Even just gently squeezing the gland results in pooling of venom at the base of the teeth!

Key to understanding all of this is that these gland are not salivary glands. There is no homologous structure elsewhere in nature. The glands were evolved from the ancestral mucus secreting cells, changed to become protein secreting instead. This is what is present in the iguania. The snakes and anguirmorpha (anguiids, heloderms, varanids etc.) independently eventually ended up favoring different regions. The advanced snakes turned the maxillary (upper jaw) gland into the venom gland ubiquitous in advanced snakes while the anguimorphs developed the lower jaw. The iguanians haven't done much at all with it.

Voor meer info:

http://www.evolutionbites.com

http://www.venomdoc.com