Sea-surface temperatures and palaeoenvironments of dolichosaurs and early mosasaurs

Abstract

The north-central Texas Cretaceous section and its contained fossils, as compared to sections at 'Ein Yabrud in the eastern Mediterranean region, demonstrate that dolichosaurs and primitive mosasaurs inhabited marine environments at least from the intertidal zone to <100 m in depth. The small body size of dolichosaurs and primitive mosasaurs, and the association of Haasiasaurus with marine snakes at 'Ein Yabrud, suggest similar temperature requirements to modern sea snakes and marine iguanas (Amblyrhynchus cristatus), specifically sea-surface temperatures between approximately 20° and 30° C. The Cenomanian and Turonian stages are characterised by widespread shallow seas with relatively high sea-surface temperatures extending to at least 45° N and 65° S latitude. The distribution of dolichosaurs, mosasaurs and snakes during this interval contradicts palaeoclimate models that predict high (>30° C) equatorial sea-surface temperatures and a steep latitudinal temperature gradient in the Northern Hemisphere.