Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods

Abstract

International audienceSpinosaurs were large theropod dinosaurs showing peculiar specializations, including somewhat crocodile-like elongate jaws and conical teeth. Their biology has been much discussed, and a piscivorous diet has been suggested on the basis of,jaw as well as tooth morphology and stomach contents. Although fish eating has been considered plausible, an aquatic or semiaquatic lifestyle has seldom been suggested because of the apparent lack of corresponding adaptations in the postcranial skeleton of spinosaurs, which on the whole is reminiscent of that of other large terrestrial theropods. On the basis of the oxygen isotopic composition of their phosphatic remains compared with those of coexisting terrestrial theropod dinosaurs and semiaquatic crocodilians and turtles, we conclude that spinosaurs had semiaquatic lifestyles, i.e., they spent a large part of their daily time in water, like extant crocodilians or hippopotamuses. This result sheds light on niche partitioning between large predatory dinosaurs, since spinosaurs coexisted with other large theropods such as carcharodontosaurids or tyrannosaurids. The likely ichlhyophagy and aquatic habits of spinosaurids may, have allowed them to coexist with other large theropods by reducing competition for food and territory

Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates

“…E-mail: Romain.amiot@univ-lyon1.fr. of bones are smaller and less densely intergrown than those of enamel (14), even though several case studies have shown that the original oxygen isotope composition can be preserved in Mesozoic reptile remains (7)(8)(9)(15)(16)(17). Although no method is available to demonstrate definitely whether or not the oxygen isotope composition of fossil vertebrate phosphate was modified by diagenetic processes, several ways to assess the preservation state of the primary isotopic record have been proposed [e.g., (14,(18)(19)(20)(21)].…”

A new sauropod dinosaur from the Early Cretaceous of Tunisia with extreme avian-like pneumatization

“…Diverse vertebrate faunas are known from calcareous platforms, islands and xeric coastal plains, often inhabited by endemic forms. Although the fossil record from these deposits consists mostly of incomplete specimens, diagnostic elements document unique characters interpreted as a reflection of special adaptations to exceptional combinations of ecological and climatic factors 2,7,[12][13][14] .…”

Estimating marine resource use by the American crocodile Crocodylus acutus in southern Florida, USA

“…In wild and captive crocodylians, Amiot et al (2007) O-depleted relative to ocean water by up to 5 ‰, although values greater than 0 ‰ can occur in tropical and subtropical surface waters that experience strong evaporative water loss (reviewed by Gat 1996). These isotopic differences between fresh water and seawater, and the fact that they are recorded in bioapatite, have been used to study habitat use and drinking water sources in aquatic and semi-aquatic fossil vertebrates (Thewissen et al 1996, 2007, Roe et al 1998, Clementz et al 2003, 2006, BillonBruyat et al 2005, Amiot et al 2010). …”