Isolated dinosaur teeth from the Lower Cretaceous Shahai and Fuxin formations of northeastern China
Résumé
Isolated dinosaur teeth recovered from seven localities near Fuxin (western Liaoning Province, northeastern China) are described. They come from sediments belonging to the Shahai and Fuxin formations, considered to be Aptian to Albian in age. Seven taxa have been recognized. They include the oviraptorosaur Incisivosaurus, dromaeosaurid theropods, Euhelopus-like sauropods, as well as indeterminate nodosaurid, ankylosaurid, iguanodontoid and basal neoceratopsian ornithischians. The Shahai and Fuxin dinosaur faunas show the persistence of some Jehol biota taxa such as the highly specialised Incisivosaurus, basal titanosauriform sauropods, basal neoceratopsians and some dromaeosaurids, and the addition of more derived iguanodontoids and ankylosaurians. The persistence of some dinosaurs of the Jehol Biota into the Shahai and Fuxin formations suggests a long term stability of Liaoning terrestrial environments during the Early Cretaceous. Despite sampling bias and the rather small sample that must be taken into account, teeth abundances show a significant compositional difference between the localities of the Shahai and Fuxin formations, neoceratopsian teeth representing one third of dinosaur tooth remains in the Shahai Formation whereas they are totally absent in the Fuxin Formation. Ankylosaur teeth, in contrast, represent 3% of total remains in the Shahai Formation, whereas they seem to be the only herbivorous dinosaurs in the Fuxin Formation with 40% of the total number of teeth (the rest being theropod dinosaur teeth). Although a difference in micro-environmental conditions between Shahai and Fuxin localities may at least partly explain such pattern, the unusual and unbalanced faunal composition of Fuxin localities remains enigmatic and will need further field collecting in order to be clarified.