RE: Polish find in Nature

["Choo, Brian" <bchoo@museum.vic.gov.au>]

>How reliable is the trackway dating?

Unambiguously lower Eifelian. (refs 40-45 in the Nature Paper)

>How reliable is the dating of tiktaalik?

Unambiguously Frasnian based on palynomorph data. Plus it should be noted that 
more derived (tetrapod-like) fishapod Livonia existed long before Tiktaalik.

>It seems odd to me that tiktaalik would exist in the presence of fishapods 
>with better developed limbs, but that may just be >my inability to conceive of 
>a niche that would favor the development of stubby leg like fins over "true" 
>limbs or "true" fins.

Not just "fishapods with better-developed limbs" - full blown 
look-at-my-fingers Tetrapoda were crawling about out of the water in the 
earliest Mid Devonian. Note that the Wojciechowice trackways are in a very 
different depositional setting to all other fishapod and Famennian 
stem-tetrapod sites - a marine tidal flat environment devoid of terrestrial 
vegetation as opposed to a swampy, vegetation-rich freshwater setting (ie. 
Middle Devonian tetrapods occupied different niches to Middle Devonian 
fishapods). There is no evidence as yet for tetrapods in freshwater habitats 
until at least Givetian and they did not become common until the Famennian 
leaving plenty of room for Tiktaalik and kin.

Cheers
Brian

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