.Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolutionPhil R. Bell, Nicolás E. Campione, W. Scott Persons, Philip J. Currie, Peter L. Larson, Darren H. Tanke, Robert T. Bakker
Abstract
Recent evidence for feathers in theropods has led to speculations that the largest tyrannosaurids, including Tyrannosaurus rex, were extensively feathered. We describe fossil integument from Tyrannosaurus and other tyrannosaurids (Albertosaurus, Daspletosaurus, Gorgosaurus and Tarbosaurus), confirming that these large-bodied forms possessed scaly, reptilian-like skin. Body size evolution in tyrannosauroids reveals two independent occurrences of gigantism; specifically, the large sizes in Yutyrannus and tyrannosaurids were independently derived. These new findings demonstrate that extensive feather coverings observed in some early tyrannosauroids were lost by the Albian, basal to Tyrannosauridae. This loss is unrelated to palaeoclimate but possibly tied to the evolution of gigantism, although other mechanisms exist.
Our results, therefore, reveal an intriguing counterintuitive pattern between size and integumentary evolution within Tyrannosauroidea that can only be tested by future fossil discoveries.
In fact, the early tyrannosauroids did not have feathers either.
They had bristles.
