Posts Tagged ‘Cretaceous’

Second Elasmosaurus Fossil Skeleton Found in Alabama

August 6, 2013

Most schoolteachers and students don’t realize they are writing with fossils when they use chalk.  Chalk consists of plankton, especially coccoliths, that mixed with mud millions of years ago.  This lime-mud eventually fossilized, turning to stone.  Chalk that became exposed to heat and pressure when buried deep under sediment metamorphized into marble–perhaps the most beautiful of natural building materials.  The majority of chalk on earth formed during the late Cretaceous and early Paleocene between 100 million to 60 million years ago.  Chalky soils are abundant in Mississippi and Alabama where the shrink-swell properties of this type of dirt help grass outcompete trees in black belt prairies.  Parts of this black belt prairie extend into Georgia (See https://markgelbart.wordpress.com/2013/02/01/georgia-eocene-chalk-prairies/ ).  Many Cretaceous-age vertebrate fossils are found in the black belt prairie region because it is located near the shoreline of what was the Western Interior Seaway, a body of water that existed during the Cretaceous and well into the Eocene era.  An educational program in Alabama allows high school and middle school students to help paleontologists collect fossils there.  Noah Taylor, a teenaged assistant, pointed out what he thought was a rock in a quarry paleontologists were excavating.  It was more than just a rock–it was the backbone of an elasmosaurus.

Location of Greene County, Alabama where a skeleton of an elasmosaurus was recently found.  The only fossil of a velociraptor found on the Appalachia side of the Western Interior Seaway was discovered here too.

Artist’s rendition of a couple elasmosaurii.

Paleontologist Dana Ehret holds one of several Elamosaur fossils discovered by 14-year-old Noah Taylor and paleontologist Takehito “Ike” Ikejiri. (Photo: Dusty Compton / Tuscaloosa News)

Scientist holding a bone of an elasmosaurus found by Noah Taylor.  The caption of this photo from a news account claimed this was a backbone.  I believe this is an error.  It doesn’t look like a backbone but rather a limb bone.

This is what an elasmosaurus backbone looks like.  All backbones look similar to this.

Map of North America during the Cretaceous.  North America was separated into 3 island continents by shallow seas.

The Demopolis Chalk Formation in Greene County, Alabama usually yields marine fossils including those of turtles, crocodilians, sharks, fish, and sea shells.  But occasionally a dinosaur died and was swept out to sea where its bones mixed with remains of marine organisms.  Marine reptiles such as mososaurs and pleisiosaurs were predators and thus less common in the environment, explaining why their fossils are found but rarely.  The elasmosaurus was a type of long-necked pleisiosaur.  Its very long neck acted almost like a fishing pole.  Its large body was probably camouflaged to look like the color of the sea, and its head, well away from its body, could rest patiently until an unwary fish swam close.  Or perhaps they used their large body and paddles to herd fish toward their head.  We’ll never know their exact hunting technique.

At this recent dig scientists found 15 out of the 70 vertebrae that made up the long neck of the elasmosaurus, and they also excavated paddle bones, though it’s not clear from news reports exactly how much of the long dead animal was recovered.  No scientific paper about this find has been written yet.  This is the second elasmosaurus skeleton found in Alabama; the other having been excavated in 1969.

The earth was a much different world during the Cretaceous. 85% of the planet was underwater.  Frosts rarely, if ever, occurred anywhere.  Everyday was like the hottest July day in Georgia.  I sometimes fantasize about jumping in a time machine to live during the Pleistocene, but I would not want to live during the hellish Cretaceous.

Shit-eating Sharks and Fish of the Cretaceous

October 15, 2010

To keep abreast of the latest paleontological finds in Georgia, I often check the Georgia Journal of Science.  The March 2010 volume has a couple of fascinating articles.  The first is “Coprolites of Deinosuchus: Late Cretaceous Estuarine Crocodylian Feces from West Georgia,” by Samantha Harrell and David Schwimmer.

Deinosuchus rugosus may have been the most powerful predator to ever live in what’s now Georgia.  This monstrous crocodylian grew to 36 feet long, weighed 12,000 pounds, and had a bite force of 13,000 newtons, perhaps the hardest bite of any land animal to ever live.  It dominated the salt marshes of Cretaceous North America (salt marshes were the most widespread ecotone of its time) even seizing and killing dinosaurs such as hadrosaurs and tyrannosaurs.  Its most common prey, however, were turtles that it crushed in its deadly jaws.  It survived as a species from 84 million to 77 million years BP, and left many fossils on the West Georgia/East Alabama border along Hanahatchee Creek near Columbus.  It was neither alligator nor crocodile but is thought to be related to an ancestor of the former.  Dr. Schwimmer, a professor from Columbus College, has been studying dinosaurs in Georgia for almost 30 years, and he wrote an excellent book devoted to the ecology of this fearsome creature.

Part of the dust cover of Dr. Schwimmer’s excellent book about Deinosuchus.

Dr. Schwimmer and Samantha Harrell now believe they’ve identified coprolites originally excreted by Deinosuchus which they found associated with its fossils in west Georgia. 

Picture of Deinosuchus coprolites from Dr. Schwimmer’s book.

Surprisingly, fossil shark and fish teeth are occasionally found on the outside of these coprolites.  These are not interpeted to have been prey of Deinosuchus.  Instead, the scientists believe it’s evidence that the sharks and fish were feeding on its feces.  It’s thought that the strong digestive juices would’ve destroyed and rendered unrecognizable the shark’s teeth, if they had been eaten by Deinosuchus, but the ones they found are identifiable as those from crow sharks (Squalicorax) http://www.oceansofkansas.com/sharks/Kansas/s-kaup1.jpg , an extinct scavenging species.  See the link for a picture of a crow shark’s tooth.  Other crocodylian coprolites discovered in Georgia are thought to belong to another extinct crocodylian–Borealosuchus.

Coprophagy, or the eating of feces, is not that unusual in the animal world.  Box turtles eat deer feces.  Crows and ravens eat crap of all kinds.  Dogs fed dry dog food crave their own feces.  Rabbits and rats must reconsume their own feces for nutrient extraction.  Foals must consume the mama horse’s feces in order to obtain the bacteria they need to digest the plants they will eat as adults.  Some snails depend entirely on fish feces.  And many insects such as butterflies and dung beetles are all attracted to shit…like flies, as the old cliche` goes.

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The second interesting article from the March volume of the GJS is a “Preliminary Description of Pleistocene Rodents from Clark Quarry, Brunswick, Georgia,” by Ray Cornay and A.J. Mead who is from Georgia College in Milledgeville.  Clark Quarry is a productive fossil site, yielding adult and juvenile mammoth skeletons, the complete skull of a long-horned bison which I discussed in an earlier blog entry, and many other large and small mammal, bird, reptile, amphibian, and fish fossils.  Here’s the list of rodents found at this fossil site:

Woodchuck–Marmota monax

Bog lemming–Synaptomys cooperi

Capybara–Hydrochoeris holmesi

Florida or round-tailed muskrat–Neofiber alleni

Rice rat–Oryzomys palustris

Cotton rat–Sigmodon hispidus

Harvest mouse–Reithrodontomys

The first two species on this list no longer range this far south.

Current range of the woodchuck.  This map is a little off.  I’ve seen woodchucks in Lafayette, Georgia.  Notice how far south Clark Quarry is compared to this species’ present range.

Current range of the bog lemming.

The Florida muskrat ranges just a little south of Brunswick today by only a few miles.  This species was more widespread during the Pleistocene, but today is restricted to Florida and extreme south Georgia.  Rice rats, cotton rats, and harvest mice still live in the region.  The species of capybara found as fossil specimens here is, of course, extinct.

The presence of woodchucks and bog lemmings is evidence of much cooler summers than those of today’s south Georgia, but the other species indicate winters at least as mild as those of today.  Scientists believe a warm thermal enclave existed near the south Atlantic coast during the Ice Age, and many believe temperatures were more equable.  I think temperatures were more equable during some climate phases of the Ice Age, but not all the time.

Woodchucks and bog lemmings both prefer to inhabit meadow/forest edge habitat which was probably a predominant ecotone of the late Pleistocene southeastern coastal plain where a mixture of open forests, prairie and wetlands existed rather unlike the closed canopy forests of today.  Fire, megafauna grazing, passenger pigeon mast consumption, locust infestations, and rapid climate fluctuations created a dynamic habitat where the ratio of woodlands to grasslands waxed and waned.  Florida muskrats (which aren’t closely related to the common muskrat–Ondatra) like open marshes, and capybaras thrive in flooded grasslands, so I believe wet prairies must have been one of the common environments in this region during the late Pleistocene.