page_title: Beipiaosaurus
section_title: Paleobiology
hierarchical_section_title: Beipiaosaurus / Paleobiology
caption_attribution_description: English: Phosphatised soft tissues in non-avian maniraptoran dinosaurs and a basal bird. a–h Backscatter electron images of tissue in Confuciusornis (IVPP V 13171; a, e, f), Beipiaosaurus (IVPP V STM31-1; b, g), Sinornithosaurus (IVPP V 12811; c, h) and Microraptor (IVPP V 17972A; d). a–d Small irregularly shaped patches of tissue. e Detail of tissue surface showing polygonal texture. f Focused ion beam-milled vertical section through the soft tissue showing internal fibrous layer separating two structureless layers. g, h Fractured oblique section through the soft tissues, showing the layers visible in f.
context_page_description: Beipiaosaurus is a genus of therizinosauroid theropod dinosaurs that lived in Asia during the Early Cretaceous in the Yixian Formation. The first remains were found in 1996 and formally described in 1999. Before the discovery of Yutyrannus, they were among the largest dinosaurs known from direct evidence to be feathered. Beipiaosaurus is known from three reported specimens preserving numerous impressions of feather structures that allowed to determine the feathering color which turned out to be brownish.
  They were relatively small-sized therizinosaurs, measuring 2.2 m long and weighing about 45–91 kg in contrast to the advanced and giant Segnosaurus or Therizinosaurus. The necks of Beipiaosaurus were shorter than in most therizinosaurs, whose are characterized by elongated necks adapted for high-browsing. Also, their feet configuration differs from therizinosaurids, having a generic three-toed pes instead of four as seen in other members.
  The exact classification of therizinosaurs had in the past been hotly debated, since their prosauropod-like teeth and body structure indicate that they were generally herbivorous, unlike typical theropods.
context_section_description: In 2018, McNamara and colleagues discovered the fossilised remains of skin flakes from numerous feathered dinosaurs from the Jehol Biota and some bird species using scanning electron microscope on the preserved feather impressions. The analyzed fossil taxa consisted of  Confuciusornis, Beipiaosaurus, Microraptor and Sinornithosaurus. For Beipiaosaurus, the specimen STM 31-1 was analyzed.
  By exposing the skin flakes under an electron microscope they found corneocytes, which are cells rich in keratin. In order to make comparisons with extant feathered dinosaurs, they analyzed several bird taxa such as Anas, Lonchura and Taeniopygia and found similar cell structures, but the fossil dinosaur corneocytes were more densely packed with keratin and lacking lipids (fat), suggesting that Beipiaosaurus and co-analyzed taxa did not get as warm as modern birds, mainly because they were ground-dwelling animals not able to fly. In the case of the primitive birds Confuciusornis, they could not fly at all for long periods. In modern birds these structures, with the addition of fats, help to regulate body temperature during active flight.
  In addition, the identified corneocytes structures seem to indicate that non-avian dinosaurs had a similar way of shedding skin to extant birds and mammals. Unlike many reptiles alive today (lizards or snakes) which shed their skin as a single piece or as several large pieces, Beipiaosaurus and other non-avian dinosaurs shed their skin as dandruff, like Confuciusornis, modern birds or mammals.
caption: Phosphatised soft tissues in non-avian maniraptoran dinosaurs and a basal bird. Beipiaosaurus in b and g
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