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C O U R S E 
Dinosaur Paleobiology
Philip John Currie, University of Alberta
C O U R S E   L E C T U R E 
Determining Dinosaur Appearance
Notes taken on August 15, 2016 by Edward Tanguay
museums often display fully fleshed-out models of dinosaurs
paleontologists have some methods to determine the appearance of some dinosaurs based on dry bone fossils
bones are hard, mineralized structures that rot away slowly
muscles, organs and skin decay quickly
they are seldom fossilized
however, sometimes paleontologists get a rare glimpse of a dinosaur's soft anatomy
footprint are natural molds of dinosaur feet
usually are no more than the sloppy outline of a dinosaur's toes
sometimes the tracks are so well preserved that they include impressions of the scales from the sole of a dinosaur's foot
in very rare cases dinosaurs were buried by mud soon after death
skin impressions formed in the mud before the flesh had time to rot away
sometimes true fossils of the skin, not just molds, can form
these are referred to as mummified
large regions of the skin hanging off the bones
Wyoming, 1910
claws, beaks, hairs and feathers are composed of keratin
harder than flesh and decomposes faster than bone
rarely fossilizing
integumentary structures, i.e. the organ system that protects the body from damage
fossilized remains of tall bristles along of tails
unclear what the bristles were for
many dinosaur bones were discovered with fossilized feathers
velociraptor has feathers
many dinosaur groups, not just birds, had feathers
bird fossils from early Cretaceous Period in China
claws of hand on wing
discoloration of the claw, where fingernail was
shows feathers around body
lake bed deposits
volcanic ash mixing in with silt
like mud it preserves detail
also alters the chemistry of the water
so where features such as feathers and fingernails would normally be destroyed by decomposition by bacteria, this bacteria can't live in water heavily altered by volcanic ash
as long as feathers are sandwiched between two layers of sediment
the feathers preserve as a corona or halo around the outside of the body
based on fossil record, the following dinosaurs should probably be displayed with feathers
definitely velociraptor since some skeletons have been found with fossilized feathers
Tyrannosaurus should probably be as well
we have no evidence that Tyrannosaurus had feathers
we have evidence that some ancestors of Tyranosaurus had feathers
therefore it's likely that the Tyrannosaurus kept these integumentary adaptations
many dinosaur fossils preserve scaly skin impressions
there are many Hadrosaur fossils with skin impressions
there are fossil from Stegasaurus which had scaly skin as well
the skins of Ankylosaurus and Stegosaurus
both have bones called osteoderms
skin bones
bones formed completely within the dermis, the lower layer of skin
some modern animals have osteoderms
some lizards such as the gila monster
turtle shells are not osteoderms, as they form through a different process
osteoderms are what give Ankylosaurs and Stegosaurus their spiky appearance
form the knob of bone on the tail
small and large spikes
form the giant plates on back and spikes on tail
growing these extra exterior bones uses up a great deal of energy but they are very useful
storing calcium
gathering heat from the sun
protection from biting and clawing predators
attract mates and intimidate rivals
feather colors
feather colors are not preserved in feather colors
in modern birds, feather color is caused by the shape and arrangement of pigment cells called eumelanosomes
long and narrow correspond to black and gray
short and wide correspond to brown and reddish brown
white feathers had no eumelanosomes
narrow aligned in the same direction lead to glossiness
some colors of some Theropods have been able to better determined by studying evidence of their eumelanosomes
the Dromaeosaur Microraptor was probably glossy black
the Archaeopteryx had at least some black feathers
we don't yet know of any fossil feathers that were blue, green, or red
Sinosauropteryx colors
we can study preserved melanosomes to better determine colors
red-brown with stripes most probable
skin colors
there is still no evidence regarding the color of dinosaur skin