Archive for February, 2013

Sabertooth Cave in Citrus County, Florida

February 28, 2013

 

Location of Citrus County, Florida.  My late grandparents used to live in Inverness located on the eastern side of the county.  The Sabertooth Cave fossil site is located near the center of the county.

My late grandparents lived in Citrus County, Florida for about 5 years during the mid-1970’s.  A manmade freshwater canal flowed past the property line of their backyard.  Developers probably dug the canal to connect residential properties with a large natural lake.  If a resident felt like boating on the lake, they had direct access to the water.  I recall enjoying many adventures when our family visited Inverness.  I caught chain pickerel and bullhead catfish in the canal.  I remember being so thrilled that I jumped up and down after landing the pickerel.  For a 10 year old with a self-esteem not unlike that of the comic strip character, Charlie Brown, successfully catching a fish was a big deal.  One day, my father and I paddled a canoe to an island in the middle of the canal.  We disembarked to do some exploring, and I almost stepped on an alligator’s head.  It hissed at me and retreated into the water.  On another occasion my grandfather took the whole family in his big new boat, and it started taking on water.  My mom nervously urged him to turn the boat around.  On my own I explored old grapefruit orchards, and the huge natural lake nearby.  I saw lots of wildlife including ospreys, limpkins, coots, anhingas, a large soft-shelled turtle, and a Florida muskrat which scolded me as I walked along the edge of the canal.

This area of Florida has always been a great place for a boy’s adventure.  In 1928 a group of boys found a natural trap cave not far from Lecanto, a town located in the center of the county.  They explored it, and 1 of the boys found a complete upper left canine of a Smilodon fatalis.  The cave was given the name Sabertooth Cave based on that specimen.

Photo of Sabertooth Cave.  I wonder how the boys explored it.  They must have used a ladder because the shaft is vertical.

The cave is actually a sinkhole trap created when acidic rainwater dissolved underlying limestone causing the ground to collapse underneath.  Animals sporadically fell inside and some birds nested in the sheltered trap, accounting for the fossil accumulation.  By 1928 the cave was accessible to the surface through 2 vertical shafts ranging from 25-40 feet deep.  George Simpson excavated the fossils that same year and catalogued them in the below referenced paper.

I’m researching for a future essay about Pleistocene deer, so I was interested in 1 particular specimen excavated from this site.  The only fossil of a species closely related to the South American marsh deer (Blastocerus dichotomous) was found here.  Based on a lower jaw,  Simpson declared it was a new species–Blastocerus extraneous.  However, in his book Fossil Vertebrates of Florida, Dr. Richard Hulbert expressed doubt that it was a valid species because no more marsh deer bones in North America had been discovered since.  I compared the illustration of the supposed marsh deer jaw bone with 1 from a photo of a white tail deer jaw bone I found on google images.  They look like an exact match.  I inquired about this species on The Fossil Forum website, and an anonymous expert informed me that Simpson didn’t have access to Key deer material for comparison.  The anonymous poster claimed that he did collect road-killed Key deer material for paleontological comparisons, and that the specimen from Sabertooth Cave was from that small subspecies of white-tail deer, not a marsh deer.  Apparently, there was a great divergence in size within the local population of white-tails as early 130,000 years ago.  During this time period marine highstands flooded the keys, and surviving Key deer must have mixed with the general population of deer. The problem with this explanation of the specimen is that marsh deer are slightly larger than white tail deer, not smaller.  Though it would be interesting if South American marsh deer once lived in Florida, I’ve concluded that Simpson was wrong, and the jawbone is just from a regular old white-tail deer.  Judge for yourself from the following images.

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An illustration of the jawbone that I believe George Simpson misidentified as coming from a species closely related to the South American marsh deer.  I just don’t see what he was seeing.  Click to enlarge.

Jawbone from a white tail deer.  Looks like a match with Simpson’s illustration.

The specimen Simpson mistakenly thought was from a South American marsh deer, possibly may  be from a Key deer, a small subspecies of white tail deer that mixed in with the general population during marine highstands when small areas of land across the state became isolated from  flooding.  Though the small subspecies often became genetically swamped, the genes for dwarfism remained in the population, allowing the subspecies to become re-established on keys .

Although I think the marsh deer specimen was a bust, Sabertooth Cave produced many exciting fossils typical of the late Pleistocene–Wheatley’s (or Jefferson’s) ground sloth, giant armadillos (pampatheres), mastodon, llama, long-nosed peccary, white tail deer, horse, tapir, capybara, saber-tooth cat, and dire wolf were the large mammal species found.  The smaller mammal species included opposum, beautiful armadillo, mole, marsh rabbit, cottontail rabbit, cotton rat, rice rat, Florida muskrat, gray fox, bobcat, and striped skunk.  Sabertooth Cave is the type locality where fossils of the Florida bog lemming (Synaptomys australis) were first found.  The Florida bog lemming may simply be a large extinct subspecies of the southern bog lemming (Synaptomys cooperi). Scientists aren’t sure. On islands large ungulates become dwarfs, while some rodents grow larger.  It’s possible during marine highstands there were many isolated  islands within vast wetlands.  That would account for key deer and large lemmings in a site located so far inland. Another interesting find at this site was the apparent co-existence of the western species of pocket gopher (Thomomys sp.) with the eastern species (Geomys pinestis).

A western species of pocket gopher from the Thomomys genus.  It lived in Florida during the Pleistocene.

Southeastern pocket gopher.  I think my cat killed 1 of these once but she wouldn’t let me take a close look at it.

Bird fossils unearthed at Sabertooth Cave were diagnosed as being those of a lesser scaup aka bluebill duck, turkey vulture, black vulture, bald eagle, sparrow hawk, barred owl, barn owl, screech owl, bobwhite quail, and turkey.  Some of these birds may have roosted here and dropped prey in the cave.  I think the vultures and eagle were attracted to animals that fell in the cave and died, and the scavenging birds in turn became trapped.  Somehow alligators and turtles fell inside the cave as well.

The species composition shows that the surrounding landscape consisted of freshwater marsh, woodland swamp, and some meadows–similar, if not exactly, the same environment that existed here til the 20th century when man ruined it.  As far as I know, scientist haven’t attempted to date the fossils found here, but most suspect they date to the Sangamonian Interglacial ~132,000-~118,000 BP.

Sabertooth canine from whence this nice fossil site got its name.

Reference:

Simpson, George

“Pleistocene Mammals from a Cave in Citrus County, Florida”

American Museum Novitas 328 October 26, 1928

http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/3110//v2/dspace/ingest/pdfSource/nov/N0328.pdf?sequence=1

The Real Turok Son of Stone

February 24, 2013

Baby boomers enjoyed reading comic books about dinosaurs when we were kids, and Turok Son of Stone served as the ultimate fulfullment of our fetish for this genre.  Turok Son of Stone featured 2 Indian brothers trapped in a lost valley where dinosaurs still roamed.  It was a flimsy excuse to show Indians with bows and arrows battling dinosaurs and on occasion cave men.  The brothers always got close to escaping the valley but their hopes were dashed at the end of each issue, usually with an avalanche of rocks.  The title must have been quite successful–the series ran from 1956-1982 and was later revived for over 4 years in the mid-1990s.  The premise, of course, is scientifically untenable.  Dinosaurs became extinct millions of years before hominids evolved, and there were no lost valleys where they could have survived.  The writers of the mid-1990’s revival series realized the unlikely science behind this and at least made the explanation that the valley existed in a repeating time loop.  In reality humans never battled dinosaurs.  However, Australian aborigines did encounter and apparently conquer very large reptiles when they colonized that island continent.

Cover illustration from the once long-running and popular Turok Son of Stone comic book.

The Australian aborigine was the real Turok Son of Stone.  They conquered and drove into extinction 3 species of monstrous reptiles.  The man on the left has a boomerang; the man on the right has an atlatl or throwing spear.  They could kill anything with a dart from a throwing spear.

Australian aborigines proved that a man with a projectile weapon can kill any animal that ever lived on earth.  The aborigines first arrived on Australia ~40,000 years ago.  They likely came from India and New Guinea and were familiar with such dangerous animals as large monitor lizards, salt water crocodiles, and sharks.  Tribal memories must have included lions, tigers, leopards, bears, and wolves as well.  When they started exploring the strange land of Australia they were prepared to battle all manner of beast.  They slew megalania (Varanus priscus), a terrifying real life dragon that reached lengths of 25 feet and had a venomous bite.  The Komodo dragon is megalania’s closest living relative, and they seldom grow to more than 6 feet long.  They have been known to kill people.  Komodo dragons also sport a venomous bite fatal to buffalo, hogs, and deer.  Imagine how dangerous a 25 foot long monitor lizard would have been.  I’m sure aborigines suffered a steady casualty rate before hunting megalania into extinction. 

Some aborigines also probably lost family members to Quinkana fortirostrum, a land crocodile that grew to about 20 feet long.  Unlike modern crocodiles, it was equipped with long legs and chased its prey down.  It had knife-like teeth built for tearing prey apart.  The quinkana is named for the aborigine legend of spirits that hide in crevices but come out at night to feast on human fat.  It’s more likely real life quinkanas attacked people during the day when the cold-blooded monsters were more active.  Neither megalanias (also known as giant ripper lizards) nor quinkanas had any fear of man, explaining why they became extinct.  For millions of years neither species had to fear any animal other than larger members of their own species.  Quinkana fortirostrum evolved 24 million years ago, though similar species of land crocodiles are even older than that and co-existed with the dinosaurs.  Quinkanas were a successful predator for 24 million years, yet, they disappeared at the exact time man first appears in the fossil record of Australia.  That’s just too much coincidence for any alternative explanation of extinction. They just lost too many conflicts with men who also probably dug up their eggs every chance they got.  Megalania existed for at least 6 million years, but it too became extinct when man arrived on the scene.  A 3rd large reptile, an 18 foot long snake known as Wonambi naracoortensis, also succombed to man.

Top: Size comparison between Megalania and modern day soldier.  Bottom: Quinkana, the extinct land crocodile.  Australian aborigines rapidly wiped out both animals, neither of which probably ever learned to fear man.  Animals that don’t fear man generally become extinct.  Imagine the bravery required to hunt these with a throwing spear.

Aborigines also drove most of Australia’s large mammals and birds into extinction.  Stirton’s thunderbird, a 1000 pound moa, and Genyornis newtoni, a 90 pound flightless chicken, both disappeared shortly after man colonized the continent.  The “duck of doom” is only known from a single 6 foot long femur.  Men must have found a giant flightless duck to be easy pickings.  The goliath kangaroo, a 400 pounder, couldn’t withstand the onslaught of man, and neither could Diprotodon australis,  a 4000 pound wombat.  Zygmaturas trilobus was an aquatic marsupial that occupied a niche similar to hippos and capybaras.  Men must have found them easy to ambush at water holes.  A tapir-like marsupial, Palorchocter azael, didn’t fare any better.  Men dug up, killed, and roasted too many Megalibigullia camgayis, an 150 pound echidna.  Man dethroned the marsupial lion, Thylacinus cynocephalox, as king of the beasts here. Propleopus oscellans, a large carnivorous kangaroo, was just as unsuccessful in its competition with man.

Illustration of an extinct species of carnivorous kangaroo.  It had wolf -like canines and ran rather than hopped.

Thylacines and a large subspecies Tasmanian devil survived the initial extinction event.  The former survived on Australia until about 3000 years ago, and the latter lasted until approximately 300 years ago.  These smaller predators could survive on the smaller game left after man wiped out the slower breeding megafauna, but competition with dingos, which were introduced to the continent about 5000 years ago, likely led to their demise.

Many people are under the false impression that marsupials survived on Australia for so long because they were isolated from placental mammals, and never had to compete with them until man arrived. This is not true.  Both placental and marsupial mammals originally co-existed on Australia, Eurasia, and the Americas.  Placental mammals did outcompete marsupials on 4 of these 5 continents, but marsupials did win Australia.

The Extinct Corkscrew Beavers of the Miocene

February 20, 2013

Corkscrew beavers gnawed through the earth instead of wood.  They made verticle corkscrew-shaped burrows with side nesting chambers and other compartments used as latrines or for water drainage.  Upon abandonment, tree roots grew into the spiral-shaped burrows and later fossilized.  Dr. Edwin Barbour first discovered these fossilized burrows in 1891.  He thought they were the remains of extinct, giant, freshwater sponges.  He referred to them as “Devil’s Corkscrews” because of the shape and the direction–8 feet deep, straight into the ground.  Within a decade, however, other scientists recognized the structures were made by extinct species of terrestrial beavers, whose bones were often found inside the burrows.  During the 1970’s a paleontologist, Larry Martin, determined the beavers used their teeth to gnaw through the hard-packed earth and then used their claws and limbs to kick the loosened dirt out of the chamber.

Paleocastors used their teeth to gnaw through hard-packed earth instead of wood.

Fossil of a corkscrew-shaped burrow made by a Paleocastor.  Note the side living chamber.

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Photo of paleocastor burrows.  Paleocastors lived in colonies similar to modern day prairie dogs.

Corkscrew beavers lived during the late Oligocene to the late Miocene (~27 million-~7 million years BP).  They occupied the early grasslands that first appeared on the landscape then.  Though most of North America and Eurasia consisted of tropical to semi-tropical forest during this era, there were some arid grasslands in parts of the west such as Nebraska and Kansas where these burrows have been found.  Corkscrew beavers lived in colonies much like modern day prairie dogs.  They suffered predation from a commensal carnivore known by the scientific name, Zodiolestes daimonelixensis.  One source refers to Zodiolestes as an extinct relative of the raccoon while another claims it was in the mustelid (weasel) family.  So I don’t know the correct classification, but in any case, it occupied a niche similar to that of the black-footed ferret which lives in prairie dog colonies and regularly preys on them.  Fossils of Zodiolestes have only been found in corkscrew beaver burrows.  Incidentally, the scientific name, daimonelix, is the Latin word for devil’s corkscrew.

There are 4 known species of corkscrew beavers–Paleocastor magnus, P. fossa, P. penninsulus, and Pseudopaleocastor barbosi.  They disappear from the fossil record during the late Miocene.  This is when climate changed from year round equible to cycles of wet and dry seasons.  Perhaps corkscrew beavers were unable to survive long draughts. 

No fossils of corkscrew beavers have been found in southeastern North America.  Southeastern North America was mostly forested and probably didn’t provide favorable habitat for them.  But who knows?  Maybe some day someone will find their fossils somewhere in the region.

Paleocastors were not ancestral to modern day aquatic beavers.  There was an aquatic species of beaver (Agnotocastor) that also lived in North America during the Miocene but it was not ancestral to modern day beavers either.  Modern day beavers are descended from Eurasian beavers that crossed the Bering landbridge at the beginning of the Pleistocene 2 million years ago.

See also https://markgelbart.wordpress.com/2012/10/10/some-giant-ground-sloths-dug-long-burrows/

References:

Lugn, Alvin

“The origin of Daemonelix”

Papers in the Earth and Atmosphere Sciences of the University of Nebraska

Martin, Larry

“The Devil’s Corkscrew”

Natural History 103 (4) April 1994

Beavers Create 9 Different Kinds of Habitat in the South

February 15, 2013

The beaver (Castor canadensis) impacts the natural environment of North America more than any other vertebrate species, besides man.  Joel Snodgrass surveyed beaver-created patches on the Savannah River Site during the 1990’s and documented 9 different kinds of habitats.  He began his study by examining aerial photographs of the SRS.  Beavers had been extirpated from the region by 1950, the year they were first protected by law.  Photos from 1950 showed no beaver activity or presence at all.   But beavers recolonized the site, and aerial photos from 1978 showed 24 active beaver ponds and 27 patches of land influenced by beavers.  Beaver populations continued to rise and photos from 1992 showed 37 active dams and 49 patches of beaver-created habitat.  Beavers so successfully recolonized Georgia and South Carolina that they were removed from protected status in 1983, and their populations are now controlled to prevent the flooding of roads, residences, and valuable timber.

The following is a list of beaver-created habitat recognized by Joel Snodgrass in his study of the SRS.

1. Flooded hardwoods–When beavers first dam a stream the impounded water floods such bottomland species as tulip, sweetgum, red maple, and tupelo.

2. Open water–Eventually the trees die and sunlight feeds aquatic plants such as pondweed, water milfoil, and bladderwort (a carnivorous plant).  Smartweed and arrow arum (duck potato) attract ducks.  Charles Wharton studied a 3 pond beaver complex in Fayette County near the Flint River and recorded a variety of fish including bowfin, pickerel, creek chubsucker, mosquito fish, shiners, small mouth buffalo, crappie, largemouth bass, bream, and darters.  He also found frogs, salamanders, snakes, 5 species of turtles, King and Virginia rails, bitterns, green herons, red-winged blackbirds, warblers, ducks, muskrats, raccons, rice rats, and swamp rabbits.  A hunter told him he’d seen at least 1000 ducks on the pond during hunting season.

Beaver pond and standing dead wood at Cobb Creek, Toombs County.  Beaver ponds are habitat for many species of aquatic wildlife.  Photo by Alan Cressler.

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Aerial photo of 3 pond complex created by beavers near the Flint River from Charles Wharton’s book The Natural Environments of Georgia.  He found these rich in aquatic wildlife.

3. Emergent marsh–Sediment gradually builds in the pond and rushes (Juncus sp.) and bulrushes establish a foothold.

4. Wet shrub–More sediment leads to a growth of shrubs such as buttonbush, alder, and Virginia sweetspire.  Buttonbush and alder formed an important part of the mastodon’s diet in the south when that extinct species used to live in the region.  A study of fossil mastodon dung found in the Aucilla River, Florida  found buttonbush (Cephalanthus occidentalis) to be the leading item in its diet along with cypress twigs.

Buttonbush.  A favorite food of the mastodon.  It’s a dominant plant in some stages of beaver pond succession.

5. Wet meadow–Eventually sediment completely fills the pond and beavers remove most of the trees in the vicinity, allowing panic grasses, bluestem grasses, and sedges to dominate.  During the Pleistocene mammoths, bison, and horses would have been attracted to beaver-created meadows.

Beaver pond.  Meadow stage.

Beaver pond.  Shrub stage.

6. Dry meadow–The wet meadow dries and bluestem grasses, daiseys, and blackberry brambles take over.

7. Dry shrub–Buttonbush, wax myrtle, alder, and Virginia sweetspire dominate this stage of succession.

8.  Dry dead hardwoods–Stands of dead tulip, red maple, sweetgum, and tupelo occur when beavers flood and kill the trees and something (a predator or human trapper) removes the beaver after just a short period of maintenance.

9. Early forest succession–Dry meadows and dry shrubs eventually give way to pioneer red maple, tulip, alder, and Virginia sweetspire.

On the SRS 2/3rds of the streams beavers dam are considered second order streams.  Geologists rank streams from smallest (first) to largest (twelfth).  2nd order streams are located near the headwaters and usually have just 1 tributary.  They flow into larger streams.  Beavers do sometimes dam larger streams, but most simply dig tunnel dens in the sides of larger bodies of water, such as rivers.

A >40,000 year old fossil beaver dam was found in a kaolin clay mine in Deepstep, Georgia.  Most of the cut wood was from cypress trees.  Castor canadensis co-existed for 2 million years with a much larger species of beaver–Casteroides ohioensis.  Fossil evidence of both species has been unearthed in Tennessee, Alabama, Georgia, South Carolina, and Florida.  The giant beaver grew to more than 300 pounds.  It was not ancestral to the modern beaver.  Scientists don’t know whether or not the giant beaver also built dams.  The evidence against is based on dental morphology.  The giant beaver mostly ate succulent aquatic vegetation, and its teeth were not as well suited to gnawing wood as the modern beaver.  However, Natalia Rybczinski, a Canadian paleontologist, studied the teeth of Dipoides, an extinct Pliocene-aged beaver found associated with a fossil beaver dam, and she told me its teeth were even less suited for gnawing wood than those of Casteroides ohioensis; yet fossils of this species were found associated with a beaver dam and lodge with marks from cut wood matching its teeth.  She thinks dam and lodge-building are activities so instinctive in the beaver family that all extinct aquatic species of beaver must have built dams and lodges to some degree, though the modern extant beavers have more efficient teeth for this purpose.

Almost every paper on Casteroides includes the phrase, “there’s no evidence giant beavers built dams like their modern cousins.”  I recently discovered this isn’t true.  A fossil skull of Casteroides was discovered in a fossil beaver lodge found in New Knoxville, Ohio, and the find was documented in a Geology Bulletin published in 1905.  It’s possible the giant beaver was using a lodge built by its smaller cousin.  (Whoever discovered this site didn’t think to compare the marks on the cut wood with giant beaver teeth to see if they matched. The skull is housed at the Cleveland Museum.  The fossil wood’s probably been lost.)  Nevertheless, I think that it’s pretty good evidence giant beavers built dams and lodges like their modern cousins.  I think giant beavers did build dams and lodges but weren’t as dependent upon them for survival as their smaller cousins and could survive in wetlands that were sparsely wooded because their greater size allowed them to fight off predators with more success.

Modern beaver colonies abandon their lodges after a decade because they deplete their food supply.  They can’t risk long overland journeys for wood because it puts them in danger of being killed by predators.  They may return to abandoned ponds after enough woody shrubs grow back.  During the Pleistocene, megafauna grazing and browsing probably delayed the return of the woody shrub stage, keeping the patch as a perpetual grassy marsh likely favored by the giant beaver.  I think humans overhunted giant beavers to extinction, but it could be that the extinction of mastodons and mammoths caused a collapse in the ecological interplay between Castor canadensis and the megafauna in creating the kind of habitat giant beavers required.

Illustration of giant beaver and size comparison between Casteroides ohioensis and Castor canadensis.  I think the greater size of the giant beaver lessened its dependence upon trees and dam-making, though it did build dams on occasion.

References:

Snodgrass, Joel

“Temporal and Spatial Dynamics of Beaver-Created Patches as Influenced by Management Practices in Southeastern North America”

Journal of Applied Ecology 34 1997

Wharton, Charles

The Natural Environments of Georgia

Georgia Department of Natural Resources 1978

Williamson, C.W.

“History of Ohio and Anglaize County”

Geological Survey of Ohio 16 19o5 (cited erroneously as 1912 in another paper)

Castoroides.jpg

The American Dingo

February 11, 2013

The famous dingo of Australia is an ancient breed of dog that has gone feral.  Aborigines colonized Australia ~40,000 years ago–probably before man domesticated dogs–and there is no evidence they brought dogs with them.  Instead, some humans from the subcontinent of India apparently brought dogs with them to Australia about 5,000 years ago.  The Indians assimilated with the aborigines, and many of the dogs they brought reverted to a wild state and became a top predator on the island continent.  Asians also brought this ancient breed of dog with them when they colonized America.  Scientists don’t know exactly when the ancestors of modern dogs were first domesticated, but it was probably about 12,000 years ago.  (Some genetic studies suggest dogs began to evolve from wolves as long as 100,000 years ago, but many of those early lineages died out.)   In America, just as in Australia, this ancient breed of dog goes feral.  The circumstances likely varied.  If a tribe died out naturally or was destroyed by another tribe, dingos were capable of reverting to a wild state and surviving without their human masters.  On occasion some may even have purposefully escaped captivity.  In any case American dingos weren’t recognized as a distinct wild canid until the 1970’s.  Dr. Lehr Brisbin jr., a research ecologist for the University of Georgia at the Savannah River Ecology Lab, first noticed them running wild at the Savannah River Site in South Carolina.  This area itself  reverted to wilderness when the federal government purchased the land surrounding a nuclear reactor.  Dingos have since been discovered on the Fort Gordon army base in Georgia and other lightly populated areas across the south.  Dr. Brisbin has given tame American dingos the common name of Carolina dog.

An American dingo.  Adults weigh between 40-60 pounds.  They’re an ancient breed of dog capable of surviving without humans.  Tame dingos are known as Carolina dogs.  A Korean dog, the chindo-ka, is probably the same ancient breed.

I’m not sure what scientific name to give the American dingo.  When adopted, wild puppies make good pets, though they require 24 hour companionship and attention.  And they breed with other dogs.  In human households and backyards, they can be given the scientific name Canis familiaris–the domestic dog.  Australian dingos are given the scientific name Canis lupus dingo–and are considered a subspecies of wolf.  Wolves and dogs can interbeed and produce fertile offspring as well, and some scientist give dogs a wolf subspecies status with the name Canis lupus familiaris.  But others consider dogs a separate species based on differences in behavior patterns and some slight physical differences.  The classification of species is an invention of man and in this case murky.

Wild dingos reproduce faster than domesticated dogs.  It’s thought that they breed rapidly to overcome natural mortality from parasites, such as heartworm.  They are much better hunters than domesticated dogs.  They instinctively know how to pounce on mice and shrews with their forepaws.  They are snake-killing specialists.  Dingos bite the snake and whip their neck around, cracking the snake’s vertebrae.  Domesticated dogs don’t know how to do this.  Dingos form packs and also hunt raccoon, rabbit, and probably deer.   Nursing dingos bury their feces and dig numerous small pits around their dens. The dens are burrows they dig themselves or take from other animals.  These behaviors also differentiate them from domesticated dogs.

Young pups from a wild dingo are easily domesticated and reportedly make good pets, but they require constant care.  Dingos follow their human masters everywhere and, if escape from an enclosure is possible, they will figure out how immediately.  They are an intelligent breed.

Dingos are probably the oldest breed of domesticated dog still extant and are more closely related to wolves than other breeds.  This would explain their ability to survive in the wild without people.  When native Americans were forced to leave southeastern North America, they must have left many of their dogs behind.  An increased wild dingo population must have already been established by the 1830s because Indian tribes had been decimated by European diseases.  In the mid-19th century there were still hundreds of square miles of wilderness in the south where humans and domesticated dogs were scarce, and dingos could thrive.  Then, following the Civil War, vast acreages of agricultural land were abandoned.  American dingos served as top predators in these “waste” places after cougars and wolves were exterminated by settlers.  Many settlers adopted dingos, and this is the breed of dog celebrated in the famous children’s novel, Old Yeller, by Fred Gipson.  It’s kind of surprising they weren’t recognized as a wild canid until recently, but most people that saw them probably thought they were just somebody’s dogs that got loose.

Today, the American dingo is in danger of becoming extinct in the wild.  Increasing conversion of abandoned farmland to suburbs is bringing them into contact with domesticated dogs, causing them to become genetically swamped when they interbreed.  And coyotes may be outcompeting them.  Both coyotes and dingos occupy the same niche–marginal wilderness habitats where larger predators are rare or have been eliminated by man.

The University of Florida Museum of Natural History database lists 9 specimens of Canis familiaris from the late Pleistocene fossil record found in Florida.  This is evidence the Paleo-indians brought dogs with them somewhat earlier than scientists think dogs were domesticated.  The breed they brought with them was most likely the dingo.  For a few millennia wild dingos likely shared the landscape with Pleistocene megafauna.

References:

Brisbin jr., I.L.; and T.S. Risch

“Primitive Dogs, their Ecology and Behavior: Unique Opportunities to study the Early Development of the Human-Canine Bond”

Journal of American Veterinary Medical Association 210 April 1997

Pigoch, Iris; et. al.

“Genome-wide Dates Substantiate Holocene Gene Flow from India to Australia”

PNAS 110 (5) Jan 2013

Some Remarkable Pre-Historic Snakes

February 6, 2013

Earth suffered a miserably hot climate during the Paleocene Epoch (65 million-55 million years BP).  The average annual temperature, not the average high, but the average temperature in South America near the equator was 91 degrees F.  Rainfall totals were higher than they are today as well.  Just imagine the humidity of a 110 degree afternoon after a mid-day shower.  Humans and most modern species of mammals would find such conditions unbearable.  But it was a perfect environment for the titanic snake (Titanoboa cerregonensis).

The bones of 24 titanic snakes were found at the Cerrejon open pit coal mine, the largest strip mine in the world.  It’s located in Colombia, South America.  It’s the only fossil site on that continent, yielding vertebrate bones from the Paleocene Epoch.  

The titanic snake grew to 45 feet long and weighed 2500 pounds.  This replica is displayed at the University of Florida Museum of Natural History.  Note the crocodiliforme in its mouth.

Jon Bloch holding Titanoboa vertebrae compared to modern snake. Florida Museum photo by Jeff Gage.

Not only was the titanic snake long but it was massive.  In this photo its vertebrae is compared to that from an anaconda which reaches lengths of  17 feet.

The largest extant species of snake in the world today is the reticulated python (Python reticulatus) which reaches lengths of 23  feet.  The titanic snake was double the length and much more massive.  It too killed its prey using constriction.  It likely preyed upon crocodiliformes, primitive mammals, and ground nesting birds.  South American animal life from the Paleocene epoch is poorly known.  The Cerrejon coal mine is the only Paleocene vertebrate fossil site known on the entire South American continent.  The ribs and vertebrae (but no skulls so far) from at least 24 individual titanic snakes were found here along with remains of 7 foot long crocodiliformes (Cerrojenisuchus improcerus), and a 5 foot wide turtle (Puentomys mushaisaensis).  Crocodiliformes are an extinct family offshoot of the ancestors of modern crocodiles and alligators.  Scientists believe the wide rounded shell of the turtle species they found evolved as a defense mechanism against the titanic snake.  The shape would have made them difficult for the snake to swallow.  The titanic snake was probably the top predator in its environment.  The Paleocene began after the K-T impact annihilated all the non-avian dinosaurs.  Reptiles rapidly replaced ecological niches left vacant after the demise of the dinosaurs.

The titanic snake became extinct long before man evolved, but Australian aborigines did co-exist for a while with the rainbow serpent (Wonambi naracoortensis).  The rainbow serpent reached lengths of 18 feet and lived as an ambush predator of kangaroos when they went to drink at waterholes.  It constricted its prey to death.  The Wonambi is named after the rainbow serpent of Australian aborigine legend.  Supposedly, the rainbow serpent is what is visible when sunlight shines on water at an angle that produces shimmering lights from the color spectrum.  The rainbow serpent is regarded as the guardian of water holes.  Aborigines still will not let young children play near waterholes for fear of the snakes.  Scientists speculate the legend may be based on tribal memories of the Pleistocene species of Wonambi because, if the snake preyed upon kangaroos, it was surely capable of taking a small child.

Replica of the rainbow serpent.  It’s extinct, so the actual color pattern is unknown.

Reptiles were the top predators in Australia until man colonized the continent ~40,000 years ago.  Rainbow serpents along with Megalania, a 23 foot long monitor lizard, and Quinkana, a 21 foot long land crocodile, ruled the food chain. (See also https://markgelbart.wordpress.com/2010/03/31/the-real-dragon-of-the-pleistocene-megalania/) Overhunting by man drove almost all of Australia’s megafauna into extinction.  The giant predatory reptiles became extinct when giant kangaroos, 3 ton rhino-like wombats, marsupial lions, 150 pound echidnas, and ostrich-sized birds all disappeared within a few thousand years of man’s initial appearance.  Some scientists proposed that anthropogenic fires transformed the landscape and contributed to these extinctions, but the latest studies show these fires occured a century after the Australian megafauna became extinct.  These findings are consistent with studies of megafauna extinction in North America and Madagascar. The increase in pyrogenic habitat was likely a consequence of megaherbivore extinction.  After man killed much of the megafauna, flammable plant material accumulated to a greater degree than formerly.

Southeastern North America was home to a remarkable prehistoric snake–the Chocktaw giant sea snake (Pterosphenus schucherti).  It lived during the Eocene (55 million-33 million years BP) when the coastal plain of the south was  a shallow ocean.  Pterosphenus grew to 18 feet long, double the size of the largest species of modern sea snake.

Photo of a yellow sea snake (Hydrophis spiralis), the largest species of extant sea snake.  It grows to 9 feet long, half the size of pterosphenus.  Sea snake lungs are almost as long as their bodies, giving them an impressive capacity for storing air.  They also can fulfill 25% of their respiratory needs through their skin.

All 62 extant species of sea snakes have a venomous bite, so it’s probable pterosphenus did as well.  Sea snake venom is the most deadly snake venom in the world, and it causes instant death for fish.  A quick-working venom is an evolutionary advantage, especially in a watery environment where a snake-bitten fish could swim far enough away that the snake couldn’t find it.  Most species of sea snake don’t bite men, and they can’t even coil and strike, so about the only way for a man to get bitten would be to grab it by the head.  The below map shows the fossil distribution of the Chocktaw giant sea snake.  Note all these localities were underwater then.  The type specimen was discovered in Chocktaw, Alabama, hence the name.  In Georgia a pterosphenus back bone was found in the Hardie Kaolin Clay Mine located in Wilkinson County.  The snake lived in bays and open ocean.

Georgia Eocene Chalk Prairies

February 1, 2013

Georgia Eocene Chalk Prairies are a variation of the blackland prairies that are found in a narrow belt across the southeast.  Most blackland prairies are dominated by 2 species of grass–Indian grass (Sorghastram nutans) and little bluestem grass (Schizachium scoparium), but Georgia Eocene Chalk Prairies are considered unique because little bluestem is absent and deceptive bluestem (Andropogen virginicus) occurs as a dominant instead.  Prairie clovers, a common component of most blackland prairies, are absent here as well.  Botanists recently recognized and designated Georgia Eocene Chalk Prairies as a unique and rare environment.

Location of Houston (pronounced howston) County in Georgia.  The Oaky Woods Wildlife Management Area is in the southeastern part of the county.  Remnant blackland prairies occur within this WMA.

Canebreaks 003

Map of Blackland Prairies from the below reference.  Georgia Eocene Chalk Prairies are a disjunct from the more extensive areas located to the west of the state.  They host hundreds of plant species found in the south, the west, and nowhere else on earth.

Blackland prairies exist within forested zones because the qualities of the soil allow grass to outcompete trees.  During the Cretaceous and Eocene epochs, the ocean inundated the coastal plain of southeastern North America.  Feldspar-laced sediment from the piedmont washed down the rivers into the ocean where it accumulated along the marshy shorelines.  This sediment eventually became kaolin clay.  Limestone formed from sea shells and coral and mixed with the clay, making it alkaline.  This combination of shrink-swell clay and an alkaline ph favors grass over trees.

This is a photo on google images I found of a blackland prairie in Mississippi.

A Georgia Eocene Chalk Prairie.

Shrink-swell clay soil.

Botanists surveyed 6 tracts totaling 106 acres of Georgia Eocene Chalk Prairie located in the Oaky Woods and Ocmulgee Wildlife Management Areas, and they found 351 species.  Characteristic species of Georgia Chalk Prairies include Indian grass, deceptive bluestem, old field goldenrod, globular cone flower, diamond flower, coralbeads, milkpea, dropseed, panic grass, sages, asters (49 species such as sunflowers and rosinweed), hawthorn, persimmon, redbud, chinquapin oak, bastard oak, dogwood, elm, and southern black haw.  The site hosts western species, southern species, and species found nowhere else (endemics).  Rare species such as wedgeleaf draba, heartleaf noseburn, and Durands skullcap are found here.  Bastard oak (Quercus sinuata) is an example of a species that is common in the west, especially in Texas, but occurs as a disjunct relic in Georgia’s chalk prairies.  Kudzu, Japanese honeysuckle, Johnson grass, and white clover are problematic invasive species.

Diamond flower (Houstonia nigricans) occurs with dropseed (Sporobolus vaginaflorus) in disturbed areas of the prairies.

Coralbeads (Cocculus carolinus) is common.  Birds like the berries which may be poisonous to humans.

Globular Prairie Coneflower (Ratibida pinnata).  Perhaps the most beautiful flower here. 

Redbud (Cercis canadensis).  This is in the legume family.  A caterpillar that feeds upon this plant is known as the catalpa worm.  It’s a popular fishbait.

Fringed campion (Silene catesbaei).  This is a rare plant found in only a few locations in the entire world.

Last year, the state of Georgia protected this unique environment when the legislature moved to stop a real estate developer from building a 20,000 home subdivision in the middle of the Oaky Woods Wildlife Management Area.  The Nature Conservancy offered to help fund the purchase of the land in 2002 but that deal fell through and some asshole was going to dam Big Grocery Creek, creating a lake that would have flooded 3 state record trees, centuries-old oaks and beeches, and Eocene fossils found on the exposed creek bed.  The development would have greatly fragmented the last population of black bears in the entire piedmont region of southeastern North America.  But an outcry from outdoorsmen stopped that travesty.  It ended up costing the state a lot more than it would have, if they’d made the original deal with the Nature Conservancy.  Unfortunately, the Georgia DNR opened a hunting season on the 300 black bears still living here, and 10% were killed on the first day of the hunt.  I think the Oaky Woods WMA was saved from developers, so rednecks could shoot bears and wild boars.  I guess rednecks are the lesser of 2 evils.

I would like to visit Oaky Woods, but my wife and daughter are not enthusiastic about a potential trip there.  It’s called Oaky Woods because a lush forest of upland hardwoods grows on rich soil in a geographcal region otherwise dominated (formerly) by open pine savannah and floodplain forests.  (Of course, today it’s surrounded mainly by tree farms and agricultural fields.)  12 species of oaks grow in Oaky Woods, and a southern disjunct population of chestnut used to be a component, as evidenced by still sprouting stumps. Weyerhauser used to own the land, and they grew pine trees on the uplands, but the area around Big Grocery Creek had not been logged in over 80 years, and it was never clear cut, so there are some trees as old as 150 years there.  Big Grocery Creek cuts through an Eocene fossil deposit that contains 40 million year old shark’s teeth, whale bones, sea shells, and sand dollars.  I’m sure glad it wasn’t destroyed by some greedy real estate developer.

Reference:

Echols, Lee; and Wendy Zomlefer

“Vascular Plant Flora of the Remnant Blackland Prairies in Oaky Woods Wildlife Management  Area, Houston County, Georgia”

Castanea 75 (1) March 2010