Posts Tagged ‘Smilodon fatalis’

6 Scariest Species to have Ever Lived in Georgia

October 30, 2016

6. The Hell Pigs

Vicious entelodonts lived on earth from the late Eocene to the mid Miocene (for over 20 million years).  They were 4 feet tall and reached weights of 930 pounds.

Entelodonts are known as hell pigs because their fossil remains represent a once terrifying animal that resembled a giant pig.  They occurred across most of the Northern Hemisphere, and there were many species over time.  Entelodonts existed between 37.2 million years BP-16.3 million years BP.  Although they resembled pigs, anatomical evidence suggests they were more closely related to the common ancestor of hippos and whales.  Enteledonts were 4 feet tall and weighed up to 930 pounds.  They were fast runners, and paleontologists believe they rammed into their prey, knocking their victims down and biting them until their bones were broken, probably similar to the way hippos kill humans in Africa today.  Fossil evidence of enteledonts has been found in Twiggs and Houston Counties in Georgia.  The tooth found in Houston County compares favorably with Archaeotherium, a once widespread species of enteledont.

Picture

Entelodont tooth found in Bonaire, Georgia.  I am not the author who took a photo of this tooth. This photo was made by Thomas Thurman and it’s from his http://www.georgiasfossils.com website.

4. (tie) The Giant Short-faced Bear (Arctodus simus) and the Saber-toothed Cat (Smilodon fatalis)

I can’t decide which 1 of these was more frightening.  Giant short-faced bears were on average as large as Kodiak bears–the largest subspecies of brown bear ( Ursus arctos ).  However, they probably made a lot of noise and could be easily detected and avoided.  Saber-tooths were ambush predators and could sneak up on prey in the dark or in thickly vegetated habitat.  Arctodus was much larger, weighing about 1000 pounds compared to ~350 pounds for Smilodon.  But the latter was very powerful and sported fangs.  Fossil evidence of this big cat has been found in all of the states bordering Georgia.  Fossil evidence of Arctodus has turned up in an Alabama county adjacent to Georgia as well as several sites in Florida.  Both undoubtedly once ranged into Georgia.

Image result for arctodus simus

Giant short-faced bear and saber-toothed catThe illustration of this saber-tooth is inaccurate.  Smilodon had a bob-tail and their forelimbs were much more powerfully built than depicted here.

3. Appalachiosaurus

 

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Appalachiosaurus terrorized upstate Georgia during the late Cretaceous.

Appalachiosaurus was a species of tyrannosaur that lived on the eastern side of the Western Interior Seaway during the late Cretaceous (~80 million years BP-65 million years BP).  They were the top land predator, probably hunting hadrosaurs or anything else they could catch.  Fossil evidence of this species has been excavated from Hannahatchee Creek near Columbus, Georgia.  The type specimen, a nearly complete skeleton, was found in Alabama.

2. Deinosuchus rugosus

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Evidence suggests Deinosuchus rugosus ate tyrannosaurs.

This extinct crocodylian, a relative of alligator ancestors, grew to an estimated 36 feet long and weighed up to 17,000 pounds.  They were large and powerful enough to seize and drag a tyrannosaur into the water, and there is some fossil evidence they preyed upon them.  They likely ate dinosaurs as a significant part of their diet.  Fossil evidence of this species has also been found in Hannahatchee Creek as well as the Chattahoochee River in Georgia.

1. Man (Homo sapiens)

Image result for atomic bomb mushroom cloud

Homo sapiens is clearly the scariest species to have ever walked on earth.  Here is a photo of an atomic bomb mushroom cloud.  Humans can wipe out entire cities with nuclear weapons.

Human beings construct weapons of mass destruction capable of turning livable habitat into uninhabitable wasteland.  I can’t think of anything scarier than that.

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New Species of Early Pliocene Saber-tooth (Rhizosmilodon fiteae) Discovered in Florida

January 8, 2014

Phosphate mining requires the removal of 50 feet of soil, resulting in severe environmental degradation.  By law, mining companies must restore the land following completion of mineral extraction, but it will be centuries before anyone can honestly say the eyesore has been returned to a pristine condition.  Strip mining operations are bad for the environment, but they often expose fossiliferous strata, much to the delight of paleontologists.  Fossil hunters prospecting the spoil piles of the Fort Meade phosphate mine in Polk County, Florida found the remains of 70 species of vertebrates (from thousands of specimens)  dating to the early Pliocene (~4-5 million years BP).

Map of Florida highlighting Polk County

Polk County, Florida–the location of the Fort Meade Mine where many early Pliocene fossils were found.

Fort Meade Mine in Florida.  Scientists discovered an early Pliocene fauna of fossils here in the excavated spoil piles.  

Periodic sea level transgressions explain why marine fossils were found mixed with fossils of land mammals at this site.  Shark’s teeth, including those of the extinct Hemipristis, along with gar and barracuda remains, turtle shells, and fossils of alligators, seals, and whales were found next to the bones of many species of mammals known to have lived in North America during the early Pliocene, just before Ice Ages began occurring.  This was the final age of the hippo-like rhino (Teleoceras), a beast that was about to become extinct after being the most common large mammal here for millions of years.  Several species of 3-toed horses, as well as long-necked camels and llamas browsed the subtropical vegetation.  Eocoileus, the earliest known ancestor to the modern white tail deer and probably the first deer species to live in North America, was part of the fauna then.  Two elephant-like animals–a gompothere and Matthew’s Mastodon–trudged through the forests.  There were 2 types of short-faced bears, a flat-headed peccary, a ground sloth, and a bobcat (Lynx rexroadensis) that were all probable ancestors to the more recent and better known Pleistocene forms.  However, it was the last stand for the extinct bone-eating dog (Borophagus).  This carnivore left no descendents.  Altogether, this list of species is known as the Whidden Creek Local Fauna which corresponds to the regional Palmetto Fauna.

Perhaps the most interesting fossils from the Whidden Creek Local Fauna were the 2 species of saber-tooth cat.  Machairodus colorodensis was a lion-sized saber-tooth that may have been top predator here then.  Scientists at first misidentified the smaller jaguar-sized saber-tooth.  All they found was 1 jaw and based on that specimen it was thought to belong to a Megantereon hesperus, a species known to have ranged well to the north and west of Florida.  However, scientists later found a few more jaws and leg bones assumed to originate from the same species.  Based on this material, they determined the fossils were from a previously unknown species.  They named this new species Rhizosmilodon fiteae.  They believe this new species was ancestral the the early Pleistocene species Smilodon gracilis which was in turn ancestral to 2 late Pleistocene species–Smilodon fatalis and Smilodon populator. The former ranged across North America, while the latter lived in South America.

Figure 1 Examples of the Palmeto Fauna machairodont.

Jaw and leg bones of Rhizosmilodon fiteae–a probable ancestor to Pleistocene species of Smilodon.

There are several anatomical characteristics that differentiate Rhizosmilodon from its later descendents: It has more minor serrations on its canines, a less developed mandibular flange, larger lower canines, and a lower premolar that is absent or reduced in Pleistocene species of Smilodons.  The mandibular flange is the recess in the lower jaw that acted as a space for the large upper canines when the jaw was shut.

The scientists who identified Rhizosmilodon believe it is a related sister species to Megantereon hesperusRhizosmilodon and Megantereon likely co-occurred temporally but in different geographical ranges.  Rhizosmilodon’s ancestors spread throughout North America, while Megantereon’s ancestors dispersed to Asia, Europe, and Africa.  Rhizosmilodon is the oldest known ancestor to Smilodon and suggests a North American origin of the genus.

Refererence:

Wallace, Steven; and Richard Hulbert

“A New Machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with comments on the origin of the Smilodontii (Mammalia, Carnivora, Felidae)

Plos One March 2013

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0056173

Fangs!

October 28, 2013

This year, I’m devoting my annual Halloween essay to fangs, those scary anatomical structures that have evolved independently among many unrelated groups of ambush predators.  Some of the earliest placental mammals to evolve fangs were the nimravids and barbourofelids.  These 2 families of carnivores were formerly thought to be closely related, and some scientists still classify them as such.  There are 9 known species of nimravids and 7 known species of barbourofelids.  Both families had representative species that lived from the late Eocene (~40 million BP) to the late Miocene (~9 million BP).

Illustration of Barbourofelis fricki, also known as the false saber-tooth.  It was a very large carnivore that may have preyed upon rhinos, the most abundant large prey species of the Miocene.  The background environment of this illustration is likely not accurate.  Forested environments predominated during the Miocene.

Illustration of Hoplophoneus, a nimravid that grew to about 320 pounds.

The nimravids and the barbourofelids were formerly thought to have been ancestral to the cat family–they have similar builds and likely occupied similar ecological niches.  However, fundamental differerences in the auditory bulla (an inner ear bone) distinguish cats from nimravids and strongly sugggest nimravids could not be of ancestral lineage to cats.  NImravids and barbourofelids also walked flat on their feet, like bears, whereas cats walk on their toes.

direwolfmorphology 002

Click to enlarge the image.  Cats have multi-chambered auditory bulla.  Nimravids had a single chamber in some species, and in others the structure was made out of cartilage.  This is evidence that nimravids were not ancestral to cats, despite the similarity in appearance.  Click to enlarge.  This illustration is from a page in the book The Big Cats and their Fossil Relatives by Alan Turner and illustrated by Mauricio Anton.

Cats ecologically replaced nimravids.  Whether they outcompeted them or took advantage of their extinction due to other causes is unknown.  There were 2 species of fanged cats during the late Pleistocene of North America–the famous saber-tooth (Smilodon fatalis) and the lesser known scimitar-tooth (Dinobastis serus).

Illustration of Smilodon fatalis.

An extinct species of vampire bat (Desmodus stocki) fed upon the blood of megafauna during the Pleistocene.  It ranged all across the continent of North America.  See (https://markgelbart.wordpress.com/2011/10/24/the-pleistocene-vampire-bat-desmodus-stocki/)

Photo of 1 of the 3 species of extant vampire bats which live in South America.

A person doesn’t have to go far to find a creature with fangs.  Most suburban yards host a plethora of wolf spider species.  Venomous fangs help subdue dangerous prey, such as bees and wasps, quickly.  Wolf spider venom is not hazardous to people.  Venom also helps protect rattlesnakes.  Venomous snakes withdraw after injecting their venom with a quick strike, so they avoid injury while the victim struggles in its death throes.  They don’t begin swallowing prey until it has been immobilized by venom.

Illustration showing how snake fangs work.

Wolf spider (Lycosidae) fangs.

There was even a family of saber-toothed salmon swimming in the Western Interior Seaway that separated Eastern and Western North America during the Cretacous age of the dinosaurs.

enchodus saber toothed herring

Illustration of the extinct saber-toothed salmon (Enchodus sp.) that swam in the seas when dinosaurs roamed the earth.

There is a clear evolutionary advantage in the repeated occurrence of fangs in the animal world.  Individuals that carry the mutation for fangs are more likely to be able to subdue their prey without sustaining injury, and therefore are more likely to pass that gene mutation to their offspring.  Although there are no large mammalian predators with fangs today, it’s possible and likely a big cat with fangs could evolve again…if man allows enough of the natural world to exist.

Logical Flaws in Studies of Pleistocene Carnivore Tooth Wear

January 17, 2013

Van Valkenburgh co-authored a study comparing rates of broken teeth suffered by large modern carnivores with those experienced by fossil carnivores excavated from the Rancho La Brean tar pits.

http://www.cof.orst.edu/leopold/class-reading/Van%20Valkenburgh%20and%20Hertel%201993.pdf

She found that large carnivores from the La Brean tar pits suffered 3 times as many broken teeth as modern day carnivores.  The fossils she examined from the pits included saber-tooth (Smilodon fatalis), American lion (Panthera atrox), cougars (Puma concolor), bobcats (Lynx rufus), dire wolves (Canis dirus), and coyotes (Canis latrans).  The modern species that she compared them to were lions, jaguars, leopards, cheetahs, bobcats, timber wolves, hyenas, and African hunting dogs.  The specimens from the tar pits dated to between ~36,000 BP-~12,000 BP.  She concluded that competition for prey was more fierce then than it is among modern large carnivores.  She believed increased competition for food forced large carnivores to utilize more of the carcass, and this led to more broken teeth from gnawing on bone.  She dismissed the alternate explanation that the higher rates of broken teeth among large Pleistocene carnivores were the result of attempting to take down larger prey than modern carnivores usually attack.  Dr. Valkenburgh suggested the larger size of the Pleistocene carnivores compensated for the larger size of the prey.

I never paid much attention to this study because using rates of durophagy as a proxy for carnivore competition seemed like a dubious assumption.  (Durophagy is just a fancy word for bone-eating.)  I think different species either eat more bone than other species because they have different nutritional needs, or they eat more for some other unknown reason that has nothing to do with competition.

Last year, a new study was published that completely contradicts Dr. Valkenburgh’s study.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0052453

Several scientists looked at teeth from Rancho La Brean predators and extant carnivores using Dental Microwear Textural Analysis (DMTA).  DMTA requires a lot of fancy equipment and procedures including a white light confocal profilometer, a scale sensitive fractal analysis, and a scanning electron microscope.  The scientists are able to see the teeth on a computer screen in 3D.  This eliminates observer measurement error.  Carnivores that avoid bone, such as cheetahs and lions, have different types of microwear on their teeth than those that eat a lot of bone, such as African hunting dogs and hyenas.

This is the equipment used to look at tooth wear in animals.

These scientists found little difference in rates of durophagy between the extinct and extant carnivores, meaning the competition between predators in the late Pleistocene in this region was no more or less fierce than that of today’s Africa.  Of course, I don’t buy the whole proxy assumption in the first place.  Most of the broken teeth were canines rather than molars.  Canines are more likely to break when taking down prey; molars are more likely to break when chewing bones, therefore they conclude the larger size of prey was the factor that explains the higher incidence of broken teeth among large Pleistocene carnivores.

One of the conclusions of this more recent study has a logical flaw.  The scientists authoring this 2nd study used DMTA to look at the teeth of Smilodon and Panthera atrox over time.  Different tar pits hold fossils of different spans of time ranging from ~36,000 BP-~12,000 BP, so they looked at 5 specimens of each species from pits of chronologically different ages.  They found no difference in tooth wear between the older specimens and the young specimens that dated closer to the time of extinction.  Many scientists think large Pleistocene carnivores became extinct because the animals they preyed upon became extinct.   They expected evidence of increased durophagy among the most recent saber-tooths and lions as they were forced to utilize more of the carcass.  But they found no evidence of this.  I think this doesn’t disprove the likelihood that carnivores did die out because their prey disappeared.  The final sentence in the abstract seems to imply that it does though.  It states : “The difference in DMTA attributes from older to younger deposits offers little evidence that declining prey resources were a primary cause of extinction for these large cats.”  Brian Switek, who writes an online blog for National Geographic, discussed this study and even goes so far as to ask what caused the extinctions of large Pleistocene carnivores, as if this study somehow disproves declining populations of suitable prey was the cause.  In my opinion this is flawed thinking.  Besides the dubious assumption that certain species of carnivores utilize more bone if prey is scarce, it seems unreasonable to expect to find the last nutritionally-stressed members of a population to be represented in the fossil record.  The odds of an animal becoming fossilized is so rare that it’s extremely unlikely that a member of the last remnant of a species headed for extinction would become fossilized.  The sample size–just 5–is also way too insignificant to detect whether or not this was occurring.  Moreover, big cats that eat mostly meat and organs and avoid bone are more likely to die of starvation before they chew on many bones.

I contacted the main author of this study, Dr. Larisa Desantis, and pointed out the logical flaws of this conclusion but she never responded.  I tried to comment on Brian Switek’s blog but he wouldn’t even allow my comment to be published.

I believe competition with humans drove saber-tooths and American lions to extinction.  Humans directly hunted them and overhunted their prey, and it was this combination that made it impossible for these species to survive.  To expect to find evidence of this by looking at a handful of fossil teeth under a microscope is ridiculous.

Pleistocene Fossil Felid Ratios from the University of Florida Database

January 16, 2012

I followed the same procedure from last week’s study but counted the number of cat fossils in the University of Florida’s Natural History Museum database instead of dog fossils.  I only counted fossils dating from the Rancholabrean Land Mammal Age 300,000 BP-11,000 BP.  The results may be off a little because I was scrolling down while looking at a computer screen.  The results may also be misleading because many specimens may come from just 1 individual.   Nevertheless, I think the data reveals a good estimate of the ratio of species composition during the Pleistocene.

Listed on the University of Florida Museum of Natural History database, I counted 46 jaguar (Panthera onca) specimens, 21 giant panther (Panthera atrox) specimens, 42 saber-tooth (Smilodon fatalis) specimens, 6 scimitar-tooth (Dinobastis serum) specimens, 41 cougar (Puma concolor) specimens, 46 bobcat (Lynx rufus) specimens, 12 river cat (Leopardus amnicola or weidii) specimens and 1 ocelot (Leopardus pardalis) specimen.

The results are similar to those reported by the amateur fossil collectors who post on the fossil forum.  The most significant difference between their reports and database information is abundance of jaguar to saber-tooth abundance.  Amateur fossil collectors claim jaguar fossils are much more common in Florida than saber-tooth, though they do collect the latter and some have found scimitar-tooth specimens as well which are rare in the database.  It may be that the UF database includes a skeleton of a saber-tooth accounting for multiple specimens from 1 individual.

Dire wolves accounted for 64 specimens in my previous study, making them 33% more common, at least in the fossil record than any single species of big cat.  Overall, big cats combined outnumbered dire wolves 156 to 64, making large felines more than twice as common as dire wolves.  Perhaps there was less competition among species of canids, but more among felids.

Pleistocene habitats favorable to various species of big and small cats varied widely.  Mesic oak forests and cypress swamps, which expanded during warm interglacials and interstadials, favored jaguars, river cats, and ocelots.  Jaguars are adabtable enough to live in desertlike brush conditions which were common during cold arid stadials.  Cougars and bobcats thrive in many different types of environments.  The exact environments favored by giant panthers, saber-tooths, and scimitar-tooths is unknown, but it’s likely they were capable of adapting to many different ecotones.

Saber-tooths were evidently one of the most common large carnivores south of the ice sheets in North America.  They were actually no larger than a modern day jaguar.  Saber-tooths never colonized Eurasia, but a distant cousin, the scimitar-tooth had close relatives that did live from the southern tip of Africa to Alaska.  Scimitar-tooths also had longer front legs but these were more slender than those of the saber-tooth.  Their fangs were also smaller and more curved.  In Africa, Asia, and Europe scimitar-tooths became extinct much earlier than saber-tooths did in America.  I suspect they never learned to fear man, explaining their earlier extinction.  I suggest fanged cats didn’t often back down from anything.  Scimitar-tooths probably colonized southeastern North America during stadials when grasslands expanded due to dry climate which in turn caused an increase in the populations of ungulates. 

Giant panthers probably resembled large maneless lions.  True lions did live in Alaska and across Eurasia.  But south of the ice sheets in North America, the common ancestor split into 2 different species–Panthera atrox and Panthera onca.

8 cat 10 Biggest Cats in the History

This image comparing Pleistocene jaguars with modern jaguars may be a slight exaggeration, but jaguars did grow bigger during the Pleistocene because they preyed on larger mammals and had more competition among carnivores.

I’ll write more about the presence of margays and ocelots in Pleistocene Florida in my next blog entry.

Here are some related articles about big cats from my archives.

“Panthera atrox! What Kind of Cat was it?”– https://markgelbart.wordpress.com/2010/07/28/panthera-atrox-what-kind-of-cat-was-it/

“Why did fanged cathttps://markgelbart.wordpress.com/tag/saber-tooth/s have sloping backs and large forelimbs?”–

“Two new studies of saber-tooths.”– https://markgelbart.wordpress.com/2011/07/08/two-new-studies-of-sabertooth-smilodon-fatalis-anatomy/

“Cougars vs. jaguars”–https://markgelbart.wordpress.com/2010/07/08/cougars-vs-jaguars/

Top Ten Pleistocene Animals I would bring back to the Present, if I could

December 23, 2010

(Warning: I’m jumping on my soapbox for this blog entry.)

Merry Christmas?  I say bah humbug!  Christmas is an ancient pagan holiday celebrating the winter solstice–the shortest day of the year–with a festival of artificial lights.  The Romans knew how to party, and they turned this festival into a drunken orgy known as Saturnalia.  They gave toys to their kids to distract them, so the children wouldn’t be aware that their parents were engaged in a little joyful wife and servant swapping.  The Catholic Church gained political power in the 4th century, but the hierarchy was unable to stop the alcoholic sex-crazed fun.  Instead, they incorporated the holiday and falsely claimed it to be the birthday of Jesus, the invisible Jewish rabbi who the psychotic founders of Christianity believed was the son of God, after God supposedly deposited his sperm into Mary’s vagina without breaking her hymen.

Pious Christians tried to break the real spirit of what the winter solstice should be about, but they haven’t ruined it nearly as much as the oppressive rulers of today’s American society have.  Big corporations and monstrous merchants have transmogrified this glorified sex orgy into a psychological compulsion for working class people to waste money on a bunch of junk they don’t need, so that wealth is transferred from the poor to greedy merchants.  Clueless economists make the ridiculous claim that this is good for the economy.  In reality it’s only beneficial for credit card-owning banks who for the rest of the year use this expensive spending orgy to drain working class people’s money, like vampires sucking the blood of sheep.

I’m not interested in material objects, but I do have a Christmas wish that a magic Santa could transport live specimens of extinct Pleistocene animals to the present so scientists could study the beasts, and zoos could display them.  Here’s my top ten wish list:

Photo of a replica skeleton of Ermeotherium that I took at the Skidaway Island museum.

1. Eremotherium laurillardi–a giant ground sloth.  There’s nothing like this beast living today.  Diminutive South American tree sloths are the closest living relative, but c’mon, there’s just no comparison.  This massive beast lived on Georgia’s coastal plain until about 30,000 years ago which is the time the last glacial maximum began.  The climate became too cold for them in North America, but they persisted in South America until about 11,000 years ago.

2. Smilodon fatalis–the saber-toothed cat.  There’s nothing like this alive today either.  Maybe we could lead a horse or cow into its cage and solve the mystery, once and for all, how it killed its prey.

3. Glyptotherium floridanum–Glyptodont.  A mammal built like a turtle and the size and shape of a Volkswagon.  Who wouldn’t want to see this in person?

4. Mammut americanum–Mastodon.  I’d pick mastodon over mammoth.  Mammoths are closely related to extant living Asiatic elephants, but mastodons were much more primitive and were related to an ancient order close to the evolutionary foundation of elephant-like animals.

5. Megalonyx jeffersonii–Jefferson’s ground sloth  This was a smaller ground sloth about the size of an ox.  For ecological reasons I believe this was the most common kind of ground sloth found in Georgia during most of the Pleistocene.  It preferred forested environments and was better adapted to colder temperatures, living as far north as Canada.

6.  Glossotherium harlani–Harlan’s ground sloth. Co-existed with Jefferson’s ground sloth, but apparently preferred open meadows as opposed to the forested conditions frequented by the other.

7. Mammuthus colombi–Columbian mammoth.  An elephant adapted for living in a temperate region.  Definitely unique enough to make my Christmas wish list.

8. Dinobastis serum–Scimitar-toothed cat.  Not as famous as Smilodon but equally as fascinating.  Got to give it the edge over other mammals left off the top ten list such as the Pleistocene vampire bats, extinct javelinas, and extinct llamas.  Though interesting, those other species do have similar living relatives, but there are no species of fanged cats left on the planet.

9. Terratornis sp.–The terratorn.  It’s a condor with a 14 foot wingspan.

10. Hesperotestudo crassicutata–This giant tortoise lived on Georgia’s coastal plain during warm interglacials and interstadials.  It grew as big as modern day Galapagos Island tortoises, but was closely related to extant gopher tortoises.

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The nature lover in me did get a real gift this year in time for Christmas.  The state of Georgia is going to purchase 15 square miles of Oaky Woods in Houston County.  Currently, it’s being managed as a wildlife management area, but real estate developers were threatening to destroy it.  Oaky Woods is a unique wilderness.  It’s the last stand of the black bear in the piedmont region of Georgia, and it’s home to 4 state record trees.  The landscape consists of mature stands of mixed pine and oak as well as rare remnants of blackbelt prairie, a probable relic habitat dating back to the Pleistocene.  Moreover, there is some good fossil-hunting ground there.  Eocene marine fossils are commonly found on this piece of land.

See www.saveoakywoods.com

Augusta radio talk show host, Austin Rhodes, suggested I go live in a tree when I brought this subject up on the Augusta Chronicle message board.  What a jerk!  The site is now protected, however, no thanks to shmucks like him.

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My next entry will be about ice berg keel scours off the coast of South Carolina. 

Cool.

Why did Fanged Cats have Long Forelimbs and Sloping Backs?

October 8, 2010

Until about 13,000 calender years ago, two species of large, powerful, fanged cats stalked the beautiful forests and plains of southeastern North America.

Smilodon depicted in top illustration; Dinobastis on the bottom.

The more famous saber-tooth (Smilodon fatalis) is well known from the thousands of specimens found in the La brae tar pits in California, but many have also been discovered in Florida, and some fossils of them have turned up in Alabama, Tennessee, and South Carolina.  Fossils of the scimitar-tooth (Dinobastis serus) are less common–nearly complete skeletons in North America only being discovered in Friesenhahn Cave, Bexar County, Texas, though individual specimens have been found in Oklahoma, Tennessee, Florida, and some western states, such as Alaska.  This latter species had a worldwide distribution, leaving fossils in what today is England as well as Africa.

Sketch of skull found in Friesenhahn Cave from The Bulletin of the Texas Memorial Museum number 2 September 1961.

The skulls of both species of fanged cats are similar, but the two differ greatly in dentition.  The scimitar-tooth had larger incisors, but its fangs or canines were shorter and smaller.  Smilodon’s fangs were serrated in front; Dinobastis’s were serrated on both sides. When Smilodon closed its mouth, the fangs extended lower than the jaw, while Dinobastis’s fangs only reached the bottom of the jaw.

Both species had longer forelimbs than hindlimbs.  The scimitar-tooths had even longer forelimbs than the saber-tooth’s, but they weren’t quite as heavily built.

Based on anatomical characteristics, scientists believed saber-tooths and scimitar-tooths were closely related, and a recent study of DNA supports this hypothesis.  They are considered a sub-family within the Felidae.  The fanged cats are in the Machairodontinae, while all other cats, including every extant species, are considered to be in the Felinae.  See: http://www.adelaide.edu.au/acad/publications/papers/SmilodonFinal.pdf

The fanged cats had a sloping back, much like modern day hyenas (Crocuta crocuta), and likely ran about in a gait that would have resembled that of a hyena.  I’ve often wondered why they were built like this.  Some scientists speculate the longer forelimbs gave them an advantage when hunting juvenile proboscideans.  But it occurred to me after watching videos of a hyena fighting off a pack of wild African hunting dogs, that perhaps this build made it easier for them to do battle with packs of wild canids, such as their most important ecological competitor, the dire wolf, though dholes or red Indian dogs also occurred in the central part of North America during the Pleistocene, and were probably an important competitor there as well.

http://www.youtube.com/watch?v=YiqAxa1tJ5g

Perhaps with a sloping back, it was easier for the fanged cats to sit on their haunches and use their paws and fangs to defend themselves against packs of wolves that would’ve tried to nip them from behind and even bite their hamstrings.

Cats are distantly related to hyenas.  The cat branch on the evolutionary tree is placed next to the hyena branch, and the machairodontinae sub-family is the closest cat related to the hyenas.  The trait of a sloping back and longer forelimbs evolved millions of years before the Pleistocene, perhaps originating with some common ancestor of hyenas and cats.

Friesenhahn Cave in Bexar County, Texas

This is a really nice sketch of Friesenhahn Cave from the previously mentioned periodical.  The artist’s name isn’t given.

A sinkhole on a cattle ranch in south central Texas opens to an ancient cave where thousands of Pleistocene age fossils have been preserved.  Two nearly complete skeletons of the scimitar cat were discovered here about fifty years ago, along with the skeletons of two scimitar cat kittens.  This species periodically must have used the cave as a den for millennia.  The Pleistocene-age fossils are dated from between 19,000-17,000 years BP.  Some other fossils in the cave date to 9,000 BP, and some are even more recent, dating to less than 300 years BP.   Scientists believe the surrounding environment was mostly arid grassland, but occasional heavy rains (due to the drastically fluctuating Ice Age climate) caused flash floods that washed sediment into the cave, burying the bones of dead animals.  Later, the cave entrance collapsed, sealing the bones from the atmosphere.  Moreover, the limestone in the soil contributed to the preservation of the fossil material.  The sinkhole formed recently, providing the opportunity for people to discover the cave.

Thousands of baby mammoth teeth were recovered here–evidence that scimitar cats ambushed them and dragged them in the cave.  Though a pond that existed in the cave may have attracted herbivores seeking drinking water, the sheer number of individual baby mammoth specimens that accumulated here must have been the result of scimitar-tooth cat predation.  Scimitar-tooth cats must have specialized in preying on juvenile proboscideans–baby mastodon teeth were found here too.  How they successfully hunted baby mammoths, guarded by adults, is a mystery.  I assume they ambushed ones that wondered too far from the herd.

In addition to the scimitar cat fossils, the cave was the final resting place for many other Pleistocene animals.  One tooth of the other fanged cat, Smilodon fatalis, was found here along with many coyote fossils, and some of black bear.  Other remains include mammoth, mastodon, ground sloth, deer, bison, horse, camel, tapir, long-nosed peccary (a nearly complete skeleton), flat-headed peccary, black-tailed jack rabbit, cottontail rabbit, eastern chipmunk, pocket gopher, bog lemming, pine vole, eastern mole, short-tailed shrew, desert shrew, giant tortoise, box turtle, aquatic turtles, toads, snakes, and lizards.  There may be some human artificats, but nothing definite because it’s sometimes difficult to distinguish natural artifacts from manmade ones.

Scientists think the Pleistocene environment that existed at the time the specimens were deposed is one that no longer occurs anywhere.  They believe that what was to become Bexar County was mostly an arid grassland interspersed with riparian woodlands consisting of deciduous trees.  It is strange that the desert shrew, a species of the southwest desert, lived near the eastern chipmunk which lives in moist woodlands.  And indeed grassland species (bison, horse, camel, mammoth) and woodland species (mastodon, deer, long-nosed peccary, tapir) both found suitable habitat near the cave.