A extinção no fim do período Devoniano e um 'gargalo de garrafa' na evolução primeva dos vertebrados com mandíbulas modernos

terça-feira, maio 18, 2010

End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates

Lauren Cole Sallan a,1 and Michael I. Coates a,b

-Author Affiliations

aDepartment of Organismal Biology and Anatomy and

bCommittee on Evolutionary Biology, University of Chicago, Chicago, IL 60637

Edited by Jennifer Clack, Cambridge University, Cambridge, United Kingdom, and accepted by the Editorial Board April 21, 2010 (received for review December 4, 2009)


The Devonian marks a critical stage in the early evolution of vertebrates: It opens with an unprecedented diversity of fishes and closes with the earliest evidence of limbed tetrapods. However, the latter part of the Devonian has also been characterized as a period of global biotic crisis marked by two large extinction pulses: a “Big Five” mass extinction event at the Frasnian-Famennian stage boundary (374 Ma) and the less well-documented Hangenberg event some 15 million years later at the Devonian-Carboniferous boundary (359 Ma). Here, we report the results of a wide-ranging analysis of the impact of these events on early vertebrate evolution, which was obtained from a database of vertebrate occurrences sampling over 1,250 taxa from 66 localities spanning Givetian to Serpukhovian stages (391 to 318 Ma). We show that major vertebrate clades suffered acute and systematic effects centered on the Hangenberg extinction involving long-term losses of over 50% of diversity and the restructuring of vertebrate ecosystems worldwide. Marine and nonmarine faunas were equally affected, precluding the existence of environmental refugia. The subsequent recovery of previously diverse groups (including placoderms, sarcopterygian fish, and acanthodians) was minimal. Tetrapods, actinopterygians, and chondrichthyans, all scarce within the Devonian, undergo large diversification events in the aftermath of the extinction, dominating all subsequent faunas. The Hangenberg event represents a previously unrecognized bottleneck in the evolutionary history of vertebrates as a whole and a historical contingency that shaped the roots of modern biodiversity.

gnathostome    Hangenberg    macroevolution    paleontology   Romer’s gap


1To whom correspondence should be addressed. E-mail:lsallan@uchicago.edu.

Author contributions: L.C.S. designed research; L.C.S. performed research; L.C.S. analyzed data; and L.C.S. and M.I.C. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission. J.C. is a guest editor invited by the Editorial Board.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.0914000107/-/DCSupplemental. [14 MB]

Freely available online through the PNAS open access option.