Cretaceous Dinosaur Fossils Discovered in Georgia and Alabama

A fiery extraterrestrial object cooked the atmosphere and caused the extinction of all vertebrates not in the safety of water or in underground burrows 65.5 million years ago.  This event ended the reign of the dinosaurs which had been the dominant large animals for 140 million years and probably would still be today, if not for the evolutionary altering armageddon.  During this 140 million year period, thousands of species of dinosaurs evolved, became extinct, and were replaced with other dinosaur species.  Most of the evidence has vanished, destroyed by earth’s tectonic forces.  Evidence of Jurassic and Triassic age dinosaurs is absent in southeastern North America.  Though there are Jurassic outcroppings in the piedmont region of Georgia, none are fossiliferous.  However, a small piece of the state does yield Cretaceous age dinosaur fossils.  Dr. David Schwimmer, a geologist teaching at Columbus State, combed Hannahatchee Creek, a tributary of the Chattahoochee River, and in 1979 discovered a number of dinosaur fossils–a first for Georgia.  He’s returned to this site numerous times, and he frequently discovers disarticulated dinosaur remains though fossil shark teeth, fish bones, and turtle shells are far more common.  Hannahatchee Creek cuts through a Cretaceous lag deposit.  A lag deposit forms when an impediment on the ocean bottom collects bones drifting with the tides and currents.  Fossils accumulate in this same place and are cemented together.  The creek has since eroded through the deposit.

Cretaceous Georgia was much different than modern Georgia.  Half of what’s now the state was under a shallow sea, south along a line from Augusta to Macon to Columbus.  A vast saltmarsh existed adjacent to the coast.  Inland habitats consisted of deep swamp with a few high and dry pine forests.  Grass had not evolved yet.  The climate was like a muggy July heat wave…year round.  There was no change of seasons.

The following is a list of species that have left fossil evidence in Georgia and Alabama.

Appalachiosaurus montgomeriensis

Fossil replica of the Appalachian tyrannosaur, one of at least two species of tyrannosaur that lived on the Appalachian side of North America. I photographed this replica at the McWane Science Center in Birmingham, Alabama.

It’s likely there was at least one other tyrannosaur on the Appalachian side of North America which was then split into three continents separated by a vast inland sea.  Neither grew as big as Tyrannosaurus Rex which lived on the western part of North America.  Along the coast of Appalachia, tyrannosaurs were not top predators–the giant crocodylian, Deinosuchus was.

This and the next two images are from  “A New Genus of Tyrannosauroid from the late Cretaceous (Middle Campanian) Demopolis Formations of Alabama” by Thomas Carr, Thomas Williamson, and David Schwimmer, JVP 25 (1) pp. 119-143 March 2005.  This illustration show which parts of the specimen were recovered.

Photos of actual Appalachiosaurus skull bones found in Alabama.

Illustrations comparing different species of tyrannosaur.  One of the ways to determine the anatomical difference between species of tyrannosaur is to compare the maxillary finestra.  This is a hole in the skull of tyrannosaurs found below the eye socket.  This hole is of a different size and shape in different species of tyrannosaurs.

Velociraptor sp.

Most velociraptors probably had feathers or protofeathers.  Most scientists believe they’re ancestral to birds. Illustration from google images.

Only one tooth of a velociraptor has ever been discovered on the Appalachian side of North America.  Nevertheless, they probably were common.  They’re almost invisible in the fossil record of eastern North America because they lived in upland habitats where the processes of fossilization were rare.

Hadrosauridae

Illustration from google images.

Large herds of this communally nesting dinosaurs roamed Georgia.  These herbivorous giants ecologically replaced the famous sauropods.  They were able to chew their food–a big evolutionary advance.

Ornithomimids

Though they were birdlike, this is not the line considered ancestral to birds.

Nodosaurs

These vegetarians must have been tough nuts for predators to crack.

Pterosaurs

Most pterosaurs probably had feathers or protofeathers.  A recent study suggests they took a couple hops and used all 4 limbs to leap into the air commencing flight, a method unlike any flying animal existing today.  Pterosaurs weren’t dinosaurs but rather flying reptiles.  Most probably ate fish.

References

Carr, Thomas; Thomas Williamson, and David Schwimmer

“A New Genus of Tyrannosauroid from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama”

Journal of Vertebrate Paleontology 25 (1) 118-143 March 2005

www.auburn.edu/~kingdat/dinosaur_webpage.htm

www.palaeos.com/vertebrates/Lists/Glossary/

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One Response to “Cretaceous Dinosaur Fossils Discovered in Georgia and Alabama”

  1. Surprise: A Cretaceous Ice Age « GeorgiaBeforePeople Says:

    [...] http://markgelbart.wordpress.com/2011/02/04/cretaceous-dinosaur-fossils-discovered-in-georgia-and-al… [...]

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