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museums often display fully fleshed-out models of dinosaurs

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paleontologists have some methods to determine the appearance of some dinosaurs based on dry bone fossils

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bones are hard, mineralized structures that rot away slowly

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muscles, organs and skin decay quickly

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they are seldom fossilized

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however, sometimes paleontologists get a rare glimpse of a dinosaur's soft anatomy

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footprint are natural molds of dinosaur feet

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usually are no more than the sloppy outline of a dinosaur's toes

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sometimes the tracks are so well preserved that they include impressions of the scales from the sole of a dinosaur's foot

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in very rare cases dinosaurs were buried by mud soon after death

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skin impressions formed in the mud before the flesh had time to rot away

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sometimes true fossils of the skin, not just molds, can form

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these are referred to as mummified

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large regions of the skin hanging off the bones

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Wyoming, 1910

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Hadrosaurs

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claws, beaks, hairs and feathers are composed of keratin

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harder than flesh and decomposes faster than bone

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rarely fossilizing

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integumentary structures, i.e. the organ system that protects the body from damage

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Psittacosaurus

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fossilized remains of tall bristles along of tails

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unclear what the bristles were for

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many dinosaur bones were discovered with fossilized feathers

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velociraptor has feathers

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many dinosaur groups, not just birds, had feathers

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bird fossils from early Cretaceous Period in China

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claws of hand on wing

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discoloration of the claw, where fingernail was

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shows feathers around body

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lake bed deposits

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volcanic ash mixing in with silt

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like mud it preserves detail

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also alters the chemistry of the water

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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

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as long as feathers are sandwiched between two layers of sediment

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the feathers preserve as a corona or halo around the outside of the body

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based on fossil record, the following dinosaurs should probably be displayed with feathers

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definitely velociraptor since some skeletons have been found with fossilized feathers

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Tyrannosaurus should probably be as well

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we have no evidence that Tyrannosaurus had feathers

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we have evidence that some ancestors of Tyranosaurus had feathers

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therefore it's likely that the Tyrannosaurus kept these integumentary adaptations

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many dinosaur fossils preserve scaly skin impressions

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there are many Hadrosaur fossils with skin impressions

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there are fossil from Stegasaurus which had scaly skin as well

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the skins of Ankylosaurus and Stegosaurus

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both have bones called osteoderms

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skin bones

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bones formed completely within the dermis, the lower layer of skin

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some modern animals have osteoderms

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armadillos

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crocodiles

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some lizards such as the gila monster

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turtle shells are not osteoderms, as they form through a different process

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osteoderms are what give Ankylosaurs and Stegosaurus their spiky appearance

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Ankylosaurus

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form the knob of bone on the tail

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small and large spikes

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Stegasaurus

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form the giant plates on back and spikes on tail

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growing these extra exterior bones uses up a great deal of energy but they are very useful

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storing calcium

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gathering heat from the sun

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protection from biting and clawing predators

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attract mates and intimidate rivals

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feather colors

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feather colors are not preserved in feather colors

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in modern birds, feather color is caused by the shape and arrangement of pigment cells called eumelanosomes

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long and narrow correspond to black and gray

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short and wide correspond to brown and reddish brown

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white feathers had no eumelanosomes

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narrow aligned in the same direction lead to glossiness

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some colors of some Theropods have been able to better determined by studying evidence of their eumelanosomes

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the Dromaeosaur Microraptor was probably glossy black

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the Archaeopteryx had at least some black feathers

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we don't yet know of any fossil feathers that were blue, green, or red

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Sinosauropteryx colors

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we can study preserved melanosomes to better determine colors

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red-brown with stripes most probable

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skin colors

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there is still no evidence regarding the color of dinosaur skin