Lesson 2: Death and Fossilization Flashcards
What is taphonomy?
the study of all natural processes that involve an organism after it dies
this includes how it decays, is scavenged by other organisms, becomes fossilized and erodes
How could a dead dinosaur’s body have been moved from the area where it originally died?
predators and scavengers may carry a carcass to their dens or some other more secure feeding area
the bloat-and-float phenomenon
What is the bloat-and-float phenomenon?
shortly after death, decay may cause a body to swell with putrid gasses, and this may cause the carcasses of even large animals to float easily and to be transported by shallow and weakly flowing water
What are the many taphonomic factors that can contribute to the disarticulation of a skeleton?
partial consumption by carnivores
carcasses that have rotted for some time may be easily broken apart if swept away by rivers or flood waters
water currents may also carry different portions of a skeleton to different locations, based on the weight and shape of the different bones
prolonged exposure to sunlight gradually weakens and disintegrates bone
skeletons that become only partially buried will eventually lose their exposed portions
portions of skeletons may also be trampled by animals or have their mineral content leached away by the roots of plants
What is disarticulation?
A skeleton that is separated into its various components
What is plastic deformation?
occurs when pressure causes the shape of of a buried fossil to be changed such that, even when pressure is later removed, the fossil does not return to it’s original shape
it is an important process to understand and be mindful of
otherwise, plastically deformed fossils may be incorrectly assumed to display their true original shapes
How can a bone become buried?
burial can occur if an animal dies in its own burrow, if it galls into a sinkhole, or if it, or one of its bones, is buried by a predator
most often, burial occurs when water washes sand or mud over a carcass
In what types of locations is fossilization most common?
more common in wet environments than in dry environments, where there is no water to help bury the carcass
also more common at low elevations, where sand and mud carried in by water are able to build up, than at high elevations, where sand and mud are often carried away by erosion before they can build up and bury a carcass
therefore, most often dinosaur skeletons are found in ancient river, stream, and lake deposits
What are fluvial deposits?
river and stream deposits
What do animals preserved in lakes have a better chance of?
they have a better chance of preserving soft tissues like hair and feathers in the fossil
this is because there is very little water movement in the lake to disrupt the skeleton, and the sediments laid down in lakes are very fine-grained
it’s easier to preserve impressions of feathers in mud than in sand
What are lacustrine deposits?
lake deposits
Why don’t we find dinosaurs in sediments representing ancient deserts?
because there wasn’t enough sediment being deposited to preserve the skeleton
How were fossils able to form in the rocky regions of Mongolia?
during the Cretaceous much of what is now Mongolia was a sand swept desert, but it was not all dry
a river also coursed through the desert and the river formed a large deltaic plain that created a huge oasis
in this deltaic plain, many desert animals, including large dinosaurs, had a chance to be buried by the sediments that were deposited by the river
How can sand dunes create fossils?
sand dunes suddenly collapsed onto the still living animal
this can happen when dunes suddenly become wet and saturated, as during a heavy rainstorm
What are sedimentary rocks?
rocks that form when mineral and organic particles accumulate and become either cemented or compacted together
