Unexpected resilience of species with temperature-dependent sex determination at the Cretaceous–Palaeogene boundary
Sherman Silber1,*, Jonathan H. Geisler2 and Minjin Bolortsetseg3
-Author Affiliations
1Infertility Center of Saint Louis, St Luke's Hospital, Saint Louis, MO 63017, USA
2New York College of Osteopathic Medicine, Old Westbury, NY 11568, USA
3Institute for the Study of Mongolian Dinosaurs, Ulaanbaatar 14201, Mongolia
* Author for correspondence (sharon@infertile.com).
Abstract
It has been suggested that climate change at the Cretaceous–Palaeogene (K–Pg) boundary, initiated by a bolide impact or volcanic eruptions, caused species with temperature-dependent sex determination (TSD), including dinosaurs, to go extinct because of a skewed sex ratio towards all males. To test this hypothesis, the sex-determining mechanisms (SDMs) of Cretaceous tetrapods of the Hell Creek Formation (Montana, USA) were inferred using parsimony optimizations of SDMs on a tree, including Hell Creek species and their extant relatives. Although the SDMs of non-avian dinosaurs could not be inferred, we were able to determine the SDMs of 62 species; 46 had genotypic sex determination (GSD) and 16 had TSD. The TSD hypothesis for extinctions performed poorly, predicting between 32 and 34 per cent of survivals and extinctions. Most surprisingly, of the 16 species with TSD, 14 of them survived into the Early Palaeocene. In contrast, 61 per cent of species with GSD went extinct. Possible explanations include minimal climate change at the K–Pg, or if climate change did occur, TSD species that survived had egg-laying behaviour that prevented the skewing of sex ratios, or had a sex ratio skewed towards female rather than male preponderance. Application of molecular clocks may allow the SDMs of non-avian dinosaurs to be inferred, which would be an important test of the pattern discovered here.
Cretaceous, temperature-dependent sex determination, extinction
Received September 23, 2010.
Accepted October 7, 2010.
This Journal is © 2010 The Royal Society
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