Bringing Dinosaurs Back to Life PDF

Bringing dinosaurs back to life BI2CV1 Comparative Vertebrate Biology Dr Manabu Sakamoto [email protected] Dinosaurs were living animals …but all we have are fossilized bones.. How do we know how dinosaurs were like? Dinosaur postures Feathers Dino...

Bringing dinosaurs back to life BI2CV1 Comparative Vertebrate Biology Dr Manabu Sakamoto [email protected] Dinosaurs were living animals …but all we have are fossilized bones.. How do we know how dinosaurs were like? Dinosaur postures Feathers Dinosaur postures Defining features of dinosaurs Kangaroo or Godzilla? Classic 19th-20th Century mounts were upright What do the fossils say? Articulated specimens show rigid, straight tails What do the fossils say? Victorian palaeontologists broke tail bones in ‘Iguanodon’ to reconstruct them in upright postures! What do the fossils say? Modern skeletal reconstructions and mounts are more accurate to the fossil evidence Upright legs, but horizontal backs Dinosaurs held their backs and tails horizontal Upright legs, but horizontal backs Dinosaurs held their backs and tails horizontal Hand and foot postures Non-plantigrade foot postures Dinosaurs are the only groups of animals to evolve non- plantigrade feet aside from mammals Digitigrady Mammals Dinosaurs Unguligrady? Ankylosaurs Stegosaurs Sauropodomorphs Foot postures and locomotion Dinosaurs were either bipedal or quadrupedal and each with associated hands/feet adaptations. Unguligrade-like elephantine hands/feet Quadrupeda l + graviportal Digitigrade tridactyl (three-toed) feet ?? ? Bipedal Quadruped vs biped Were ornithopod dinosaurs quadrupedal or bipedal? Quadruped vs biped: fossil evidence Fossil ornithopod trackways show both manus (hand) and pes (foot) prints. Ornithopods also have hooved manual unguals (distal-most phalanx) Quadruped vs biped: fossil evidence Camptosaur us Senter 2012. Palaeontol Electron 15 Range of motion in Camptosaurus show: No pronation (palms face inward not backward) Rigid wrists Rotational motion Carpenter and Wilson. 2008. Ann Carnegie Mus 76: 227–63 Verdict Ornithopods were quadrupeds Triceratops forelimb posture Sprawled vs upright Articulation of forelimb elements indicates Triceratops may have held their forelimb in a semi- sprawled manner. If manus points forwards, then elbow must point outwards! Triceratops forelimb posture Sprawled vs upright …but I thought dinos had upright limbs! …so, which one is it?  Triceratops forelimb posture Evidence from fossil Fossil trackways are narrow- trackways gauged, consistent with an upright posture. Narrow gauge trackways  Triceratops forelimb posture Evidence from fossil trackways Outward-facing manus prints 5 …but how can 2 3 4 the manus point outwards if the forelimb is held upright? Triceratops forelimb posture Evidence from forelimb articulation It’s only outward- facing in relation Remember, dinosaurs 3 2 to the palm 1 can’t pronate their 4 wrists! National Science Museum, Tokyo 1 5 4 3 2 Triceratops forelimb posture Digit III pointing Digit II pointing outwards forwards 2 3 4 1 5 3 1 2 Elbow pointing Palm facing backwards inwards and back Triceratops forelimb posture Feathers How do we know dinosaurs were feathered? How do we know dinosaurs were feathered? Even in the 1980s there was strong evidence to indicate a theropod origin for birds. Dromaeosaurs (e.g., Velociraptor) were noted for bird-like features. But fossil feathers were only known in fossil birds, e.g., Archaeopteryx. Birds Feathery integuments in non-avian theropods First discovery of feathery integuments in non-avian theropods was in 1996 Sinosauropteryx When did feathers appear? Our knowledge of feathers in 1996. Sinosauropteryx is a ‘compsognathid’-grade basal coelurosaur Birds Feathery integuments in non-avian theropods Tyrannosauroidea Yutyrannus Large (9m) tyrannosaur with filamentous integument associated with the tail Feathery integuments in non-avian theropods Dromaeosauridae Hello, my name is: ‘Dave’ the fuzzy Sinornithosaurus raptor Filamentous feathery integuments Feathery integuments in non-avian theropods Oviraptorosaur Caudipteryx Small oviraptorosaur Symmetric primary feathers on forelimb Tail feathers formed a fan Primary flight feathers Velociraptor Fossil evidence of primary feathers in theropods Quill knobs Microraptor Primary flight feathers Fossil evidence of primary feathers in theropods Microraptor Asymmetric flight feathers Asymmetric flight feathers  Primary flight feathers Not even clear whether these are non-avian theropods or birds! Anchiornis When did feathers appear? Our knowledge of feathers in 2021. Feathery integuments are known from all major lineages within Coelurosauria Flight feathers in Paraves Feathery integuments Symmetric primary feathers Flight feathers Birds Was T. rex feathered? Obviously, the most pressing matter of the day… Was T. rex feathered? Fossil evidence of scales in tyrannosaurs Feathery integuments Scaly face? Loss of feathery integuments? Was T. rex feathered? A good compromise? Scaly face Partially covered in filamentous integuments? Scaly underside