Cretaceous Birds Lacked In Diversity

[Oxytropidoceras]

Ancient Fossils of Prehistoric Birds Reveal a Stunning

Lack of Diversity, Science World Report, May 28, 2014‎

http://www.scienceworldreport.com/articles/15038/20140528/ancient-fossils-prehistoric-birds-reveal-stunning-lack-diversity.htm

Prehistoric Birds Lacked in Diversity, University of Chicago

http://www.newswise.com/articles/view/618372?print-article

http://www.newswise.com/articles/prehistoric-birds-lacked-in-diversity

Mitchell, J. S., and P. J. Makovicky, 2014, Low ecological

disparity in Early Cretaceous birds. Proceedings of the

Royal Society B. vol. 281 no. 1787 20140608

http://rspb.royalsocietypublishing.org/content/281/1787/20140608

Yours,

Paul H.

[Auspex]

From the time when birds themselves were barely more than examples of diversity in theropods, this is not too surprising.

[FossilDAWG]

I'm skeptical of the argument that they "hadn't had time to diversify". Radiation into unoccupied niches tends to quite rapid, especially in species with short generation times. I suspect the issue was that many of the niches currently occupied by birds were already occupied by pterosaurs, and even small dinosaurs on the ground. Also angiosperms had only recently evolved and so seeds may have been significantly less abundant and diverse (especially in size) than they are today. Finally, there were flying insects in the early Cretaceous, but the lepidopterans were small and not diverse (the group really diversified later in the Cretaceous, probably driven by diversification of seed plants). From the perspective of birds, flying insect prey was probably more limiting than today.

Don

[Auspex]

Exactly; the niches hadn't opened up yet.

In fact, I think that the evolving class itself was a factor in creating their expanding niche (ever the ecologist).

[dinosaurbero]

Most likely true: The modern birds (Neornithes) started to diversify rapidly in the empty postcataclysmic niches of Paleocene and Eocene.

[Auspex]

Aves branched early on, quite possibly before they could confidently be called avian. The initially very successful Enantiorthinines underwent fairly limited evolutionary radiation, but the Euronithians were in position to take over when the world changed late in the Cretaceous. They are todays dinosaurian legacy.