Posts Tagged ‘Isle of Hope site’

The Isle of Hope Fossil Site in Chatham County, Georgia

July 6, 2014

I’ve mentioned the Isle of Hope fossil site numerous times on this blog, but I recently realized I’ve never featured it.  In my opinion it is the 3rd or 4th best Pleistocene fossil site in Georgia, ranking behind Ladds, Kingston Saltpeter Cave, and perhaps Yarbrough Cave.  More vertebrate fossils were discovered here than at any other coastal fossil site in Georgia.  Most other coastal fossil sites were discovered in the 18th or 19th centuries before paleontologists screen-washed sediment for smaller bones, and accordingly the earlier scientists only collected bones of the largest species.  The more recently discovered Clark Quarry near Brunswick may rival the Isle of Hope for best coastal site, but despite the publication of a preliminary report in 2005, the finds at this site have yet to be thoroughly and systematically reviewed in a scientific journal.

The Isle of Hope is an elite neighborhood in Savannah, Georgia.  At high tide, it is separated from the mainland by a small tidal river.  Vertebrate fossils of Pleistocene age have been collected from this river.

The Isle of Hope fossil site was a deposit that occurred on both sides of a small tidal river within the city limits of Savannah.  During high tide this rivulet separates the island from the mainland.  The fossil site was discovered in the early 1980s during construction of a boat pier.  The landowners, and John Heard, an amateur hobbyist, collected the fossils, and later, paleontologists from Georgia Southern also collected specimens from the site.  Most of these specimens are housed at the Georgia Southern Museum.  One side of the site has been “covered in riprap and is no longer accessible for collection.”   However, I suspect this entire tidal river has potential for a hobbyist prospecting for fossils  Tidal action has likely distributed specimens in both directions away from the deposit.  If I lived in Savannah, I’d definitely search for fossils here.

Uranium-series dating and fossil composition suggest the fossils were deposited during a warm interglacial climate phase between ~132,000 BP-~75,000 BP.  Every single species of mollusc and fish found in the fossil deposit still occurs in the region today–evidence water temperatures during this climatic stage were similar to those of today. 

The dwarf surf clam was the most common bivalve species found at the Isle of Hope site.  It is still the most numerically common clam in Georgia tidal inlet channels.

user posted image

Fossil brown-banded wettletraps were found at the Isle of Hope site.

Atlantic sharpnose shark

The Atlantic sharp-nosed shark.  Fossils of this species were the most common fish remains found at the Isle of Hope site.  It’s still the most common shallow water shark found in the region today.

Amazingly, the fishing in coastal Georgia 100,000 years ago would have resulted in the same species typically caught from a modern day pier–sharp-nosed sharks, stingrays, moray eels, sheepshead, black drum, toad fish, and puffers.  Schools of mullet would have been seen swimming by, and little killifish swarmed the shallows.

Eastern mud turtle.  Mud turtles were the most common reptile specimens found at the Isle of Hope site. 

 Photo of Salt Marsh Vole. Photo courtesy of USFWS/Photo by Michael Mitchell.

The meadow vole was the most common small mammal living in coastal Georgia during the Pleistocene.  This species no longer occurs this far south aside from a relic population that lives in a salt marsh in Levy County, Florida.  

There has been an interesting change in the small mammal fauna of coastal Georgia since the Pleistocene.  Then, the most common rodents were the arvicolines, including the meadow vole, southern bog lemming, and Florida muskrat.  The sigmodontine rodents (cotton rat, rice rat, wood rat, and old field mouse) were present but less common.  Today, the 3 arvicoline rodents mentioned above are absent from coastal Georgia while the sigmodontine rodents are common.  The bog lemming no longer occurs this far south.  The meadow vole also doesn’t occur this far south with the exception of a relic population that lives in a salt marsh in Florida.  The Florida muskrat no longer occurs this far north.  Scientists believe the intermingling of warm and cold climate species during the Pleistocene is evidence that climate then was more equible than it is today because formerly winters were warmer and summers were cooler.  I have a different explanation for the co-existence of warm and cold climate species during the Pleistocene.

During some climatic phases, average temperatures were less extreme than they are today, but overall climatic fluctuations were formerly more drastic.  These dramatic climatic fluctuations created more varied habitats that supported a wider array of fauna, especially of small mammals. I think the relatively stable climate of the past 10,000 years is the cause of the more zonal distribution of small mammal species today.  The change in temperature ranges between the Pleistocene and Holocene haven’t been large enough to entirely explain the disappearance of arvicolines from coastal Georgia.  Instead, I think a shift to a more stable climate pattern is a better explanation.  For example, during the Pleistocene a shift to a sudden cold pattern with snowy conditions would have benefited meadow voles over cotton rats because the former are better adapted to living under snow.  A subsequent shift to warm climate would have favored cotton rats, but during Ice Ages the warm climatic phases didn’t last long enough to completely extirpate the cold climate species.  Changes in species composition lagged behind the rapid climatic changes. But over the past 10,000 years, a warm climatic phase that has lasted quite a while, meadow voles did not enjoy the benefits of a sudden shift to cold climate in the south and have mostly disappeared from the region.  Only species adapted to warm climate have been able to continue living in the south.

Perhaps the most mysterious mammal to have lived in Georgia 100,000 years ago was a small cat.  (See https://markgelbart.wordpress.com/2013/05/09/the-mystery-cat-of-pleistocene-georgia/).  A jaw bone of this species was found at this site but not enough skeletal material has been found to determine what species this cat was.  Despite the genus name, Leopardus, it was not closely related to the leopard as some sources have erroneously and carelessly reported (See Roadside Geology of Georgia).  Instead, it was closely related to the margay and ocelot.

White-tailed deer fossils were the most abundant large mammal specimens found here.  Deer may have been more common in Pleistocene Georgia than other species of now extinct megafauna, contrary to other areas such as Florida.  However, specimens of long-nosed peccary, bison, horse, tapir, and mastodon have been found here, showing they did share the environment with deer.  I think if this tidal river were more throughly investigated, fossils of more species would be  discovered, including those of large carnivores which are so far lacking completely from coastal Georgia sites.

Eremotherium laurillardi, the giant ground sloth.  It was common on the Georgia coast during the last interglacial but disappeared from North America some time during the following Ice Age.

Below is a list of all the species found at the Isle of Hope site as reported in the reference cited at the bottom.  I had fun translating the Latin names to English.  Just 1 species of shellfish stymied my attempt to translate them all.

Isle of Hope Species List

Knobbed whelk (Busycon carica)

Brown-banded wettletrap (Epitonium rupicola)

Sea snail (Eupleura caudata)

Lettered olive (Oliva sayana)

Sea snail (Polinices duplicatus)

Eastern auger (Terebra dislocata)

Small white clam (Abra aequalis)

Incongruous ark clam (Anadara brasiliana)

Blood ark clam (Anadara ovalis)

Transverse ark clam (Anadara transversa)

Common jingle shell (Anomia simplex)

? (Divaricella quadrisulcata)

Coquina clam (Donax variabilis)

Dwarf surf clam (Mulinia lateralis)

Ponderous ark clam (Noetia ponderosa)

Atlantic nut clam (Nucula proxima)

3-toothed Cardita (Pleuromeris tridentata)

Nurse shark (Ginglymostoma cirratum)

Sand tiger shark (Carcharias taurus)

Tiger shark (Galeocerdo cuvier)

Bull shark (Carcharhinus leucas)

Dusky shark (Charcharhinus obscurus)

Lemon shark (Negaprion brevirostris)

Sharp-nosed shark (Rhizoprionodon terranovae)

Hammerhead shark (Sphyrna tiburo)

Stingrays (Dasayatidae)

Spotted eagle ray (Aetobatus narinari)

Eagle rays (Myliobatidae)

Gar (Lepisosteus sp.)

Lady fish (Elops saurus)

Moray eels (Muraenidae)

Shad (Alosa sp.)

Herrings (Clupeidae)

Hard-nosed catfish (Arius felis)

Lizard fish (Synodus sp.)

Toadfish (Opsanus sp.)

Ray-finned fish (Batrachoididae)

Killifish (Fundulus sp.)

Sea robins (Prionatus sp.)

Cutlass fish (Trichiurus sp.)

Pinfish (Lagodon rhomboides)

Sheepshead (Archosargus probatocephalus)

Silver Perch (Bairdella cf chrysoura)

Black drum (Pogonias cromis)

Red drum (Scianops ocellata)

Mullets (Mugil sp.)

Barracudas (Sphyraena sp.)

Flounders (Bothidae)

Boxfish (Lactophrys sp.)

Puffer fish (Tetraodontidae)

Porcupine fish (Diodontidae)

Siren (Siren intermedia)

Red Spotted Newt (Notophthalmus viridescens)

Conger Eel (Amphiuma means)

Spotted Salamander (Ambystoma cf maculatum)

Toads (Bufo sp.)

Chorus frog (Pseudacris ornata)

Bullfrog (Rana catesbeiana)

Snapping Turtle (Chelydra serpentina)

Mud Turtles (Kinosternon sp.)

Musk Turtles (Sternotherus)

Soft Shelled Turtle (Apalone ferox)

Box turtle (Terrapene carolina)

Chicken turtle (Deirochelys reticularian)

Slider (Pseudemys cf concinna)

Pond slider (Trachemys scripta)

Gopher tortoise (Gopherus polyphemus)

Extinct Intermediate Tortoise (Hesperotestudo incisa)

Extinct Giant Tortoise (H. crassicutata)

Black Racer (Coluber constrictor)

Bull Snake (Pituophis melanoleucas)

Water snake (Nerodia fasciata)

Queen snake or other Crayfish snake (Regina sp.)

Garter snake (Thanophis sirtalis)

Hog-nosed snake (Heterodon sp.)

cottonmouth water moccasin (Agkistrodon piscivorus)

unidentified rattlesnake (Crotalus sp.)

Unidentified duck (Anas sp.)

Opposum (Didelphis virginiana)

Beautiful armadillo (Dasypus bellus)

Giant ground sloth (Eremotherium laurillardi)

Harlan’s ground sloth (Paramylodon harlani)

Short-tailed shrew (Blarina brevicauda)

Southeastern shrew (Blarina carolinensis)

Eastern mole (Scalopus aquaticus)

Unidentified bear (Ursidae)

Raccoon (Procyon lotor)

River otter (Lutra canadensis)

Margay-like cat (Leopardus sp.)

Bobcat (Lynx rufus)

Southern flying squirrel (Glaucomys volans)

Gray squirrel (Sciurus carolinensis)

Beaver (Castor canadensis)

Rice rat (Orzomys palustris)

Cotton rat (Sigmodon hispidus)

Wood rat (Neotoma floridana)

Old-Field Mouse (Peromyscus polionotus)

Florida muskrat (Neofiber alleni)

Southern bog lemming (Synaptomys australis)

Meadow vole (Microtus pennsylvanicus)

Pine vole (M. pinetorum)

Cottontail rabbit (Sylvilagus floridanus)

Marsh rabbit (S. palustris)

Long-nosed peccary (Mylohyus fossilis)

Bison sp. (Bison sp.)

White-tailed deer (Odocoileus virginianus)

Tapir (Tapirus veroensis)

Horse (Equus sp.)

Mastodon (Mammut americanum)

Reference:

Hulbert, Richard; and Ann Pratt

“New Pleistocene (Rancholabrean) Vertebrate Faunas from Coastal Georgia”

Journal of Vertebrate Paleontology 18 (2) June 1998

 

 

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Bull Sharks (Carcharhinus leuceus) in Fresh Water Rivers

August 29, 2012

Not long ago, Noel Todd caught an 8 foot long, 368 pound bull shark in Shell Creek which is located in Valona, Georgia.  Shell Creek is a brackish stream not far from the coast, so it’s not shocking that a shark  might be found here.  However, bull sharks have been sighted 2500 miles up the Amazon River.  The North American inland shark-catching record was set in 1937 when 2 fishermen caught a bull shark in the Mississippi River next to Alton, Illinois.

Lapshark?

“Nearly comatose” bull shark discovered in Lake Pepin, Minnesota which is connected to the Mississippi River.  This is the lake where Laura Ingalls’ father (of Little House on the Prairie fame) used to fish.  Bull sharks are tropical to semi-tropical species, not well adapted to such cold waters.  I discovered 15 months after posting my article that this photo is an APRIL FOOLS JOKE.  I was fooled and I apologize to my readers.

The bull shark that Noel Todd caught in Valona, Georgia in a  brackish water tidal inlet.

In Georgia before the dam that created Lake Seminole was built, bull sharks used to congregate in the Chattahoochee River adjacent to a beef processing plant above Albany where the factory dumped the offal into the water.  Bull sharks are common in 2 freshwater lakes that have access to an oceanic outlet–Lake Nicaragua in Central America and Lake Pontchartrain, Louisiana.

Unlike most species of sharks, bull sharks are capable of living in freshwater because their kidneys with the aid of a special gland help them retain salt.  Most other species of sharks don’t have the physiology to be able to withstand long exposure to freshwater.  Other species of sharks would suffer cell edema if trapped in freshwater, and they would die.  The ability to survive in freshwater gives bull sharks a tremendous advantage over other shark species.  Bull sharks are a shallow water species that live in coastal waters.  The females give birth to 1-13 live pups which often travel to freshwater rivers where they immediately become a top predator.  Instead of being vulnerable prey like most juvenile marine life, they top the food chain.  They simultaneously avoid predators, while gaining access to a bounty of prey items.  This may also help them avoid cannabilistic adults of their own kind.  Most of the young pups stay in brackish waters and return to the ocean when they grow larger.  Scientists don’t know why a few swim great distances up freshwater rivers, but I believe that behavior is influenced by a random mutation that could potentially lead to a beneficial adaptation.

Bull sharks account for more attacks on man than any other shark species, probably because they’re a coastal species more likely to come into contact with people.  It was probably this species that inspired Peter Benchley to write Jaws. Five shark attacks that occurred along the New Jersey coast in 1916 provided the plotline for his classic story.  Two of the shark attacks occurred in Matewan Creek–16 miles inland. 

Bull sharks get their name from their habit of attacking and eating other sharks, making them a bully among sharks.  They also feed upon fish, rays, shrimp, crabs, sea snails, turtles, carrion, and garbage.  They’re considered a near threatened species which is not surprising since the entire ocean has pretty much been overfished.

Bull sharks are not the only primarily salt water species of fish found way up freshwater rivers.  Flounder, hogchokers, mullet, tarpon, and needlefish expand their range from brackish water and swim into the freshwater of the middle Savannah River basin every summer.  I’ve never had the opportunity to fish in a brackish segment of the a river but it must be interesting.  Largemouth bass, gar, and catfish are common freshwater species found in brackish waters where they swim alongside bullsharks, mullets, and flounder.

Hog chokers, a type of flounder, swim into the middle Savannah River every summer.

Needlefish–another saltwater species that spends summer vacations in the middle portion of Georgia’s freshwater rivers.

Mullet–a great tasting meaty fish that schools up freshwater rivers.  I used to catch these with a cast net in the ocean off Harbor Island, South Carolina.

The pristine waters of the Pleistocene must have held exponentially more fish then those of today, but modern day damming, overfishing, and pollution have decimated fish populations.  Bull sharks likely swam way up freshwater rivers during the Pleistocene, but the odds of finding a fossil bull shark’s tooth hundreds of miles inland must be very low.  Bull shark’s teeth have been found at the Pleistocene-aged Isle of Hope site but this is on the coast in Chatham County.

Pleistocene Bears of Southeastern North America

March 10, 2011

Nothing demonstrates wilderness more than a robust population of free roaming bears.  During the Pleistocene before people were around to kill them and destroy their habitat, there must have been tens of thousands of bears living within the boundaries of what today is Georgia.  It’s possible that 5 different species could have been found here in the same time span, though we can be more sure there were at least 3 sharing the same range.  Today, only 1 species of bear resides in Georgia–an estimated 5100 black bears still roam the mountains, the Okefenokee Swamp, the Altamaha and Ocmulgee river bottoms, and Houston County.  Occasional stragglers leave these last strongholds and raid urban dumpsters and suburban bird feeders, but these occurrences are rare.  One study of Georgia bears determined that suitable habitat can support 1 bear for every 3 square kilometers.  That means ideally, Pleistocene Georgia hosted a population of 30,000-40,000 bears.  (*Georgia is about 60,000 square miles. 1.86 square miles =3 square kilimeters.  Moreover, during stadials Georgia’s land mass increased by about 10,000 square miles due to the fall in sea level.)

Here’s a review of every known bear species that lived during the Pleistocene in southeastern North America.

Black bear–Ursus americanus

Photo from google images of a black bear in the Okefenokee Swamp.

Ursus abstruscus is the probable evolutionary ancestor of American and Asian black bears which once consisted of a geographically continuous population.  Glacial ice separated the two populations at the beginning of the Pleistocene, resulting in two different species.  Bjorn Kurten notes that Pleistocene black bears grew as large as modern day grizzlies.  I believe Pleistocene black bears were larger and fiercer than their modern day descendents because they had to survive confrontations with saber-tooths, giant panthers, jaguars, and packs of dire wolves.  Cavers and scientists discovered black bear fossils at Ladds and Kingston Saltpeter Cave in Bartow County, and the Isle of Hope Site in Chatham County.  They’re also commonly found in Florida fossil sites but only a few have been recorded from South Carolina.

Florida spectacled bear–Tremarctos floridanus

Photo of a spectacled bear, Tremarctos ornatus,  from google images.  This is the only living species from the once widespread short-faced bear family.  It is a close relative of the extinct Tremarctos floridanus.  Of course, scientists have no way of knowing whether Tremarctos floridanus was also spectacled, but they call it that anyway.

Now extinct, this was likely the second most common species of bear in southeastern North America during the Pleistocene.  Only 1 specimen has ever been recovered in Georgia (at Ladds), but its fossils have commonly been found in Florida and South Carolina.  It’s thought of as primarily a vegetarian, but a recent study of Pleistocene bears concluded that all were opportunistic omnivores that would eat anything they could obtain.  Tremarctos’s range in the late Wisconsinian Ice Age seems to have been restricted to the southeast.  During warm interglacials it expanded as far north as Kentucky.  It probably just lived in the coastal plain of Georgia and South Carolina as well as Florida during colder climatic stages.

Lesser short-faced bear–Arctodus pristinus

Photo of a fossil jaw bone of Arctodus pristinus from Additions to the Pleistocene Mammal Fossils of South Carolina, North Carolina, and Georgia by Albert Sanders.

Photo of fossil bear teeth from the above mentioned publication.

It’s unclear from the fossil record whether this species co-existed with its larger cousin, the giant short-faced bear, or was simply ancestral to it.  Its fossils have only been recovered from a few eastern sites in Florida, South Carolina, Maryland, and West Virginia.  Teeth attributed to this species overlap in size with those of Arctodus simus.  Florida fossils of this species, including those from Leisey Shell Pit, indicate this animal lived from the early to mid-Pleistocene (~1.8 million-300,000 BP), whereas giant short-faced bear fossils in Florida date to the late Pleistocene (~300,000-~11,000 BP).  However, fossils of the lesser short-faced bear were found in South Carolina sediments thought to date from the Sangamonian Interglacial (~132,000-~118,000 BP) which is also considered late Pleistocene.  These South Carolina specimens haven’t been radiometrically dated, so no one knows exactly how old they are.  Perhaps this species did survive as a relic species in some geographical locations until the megafauna extinction.  Arctodus pristinus is considered more of a general feeder; Tremarctos floridanus a more herbivorous species; Arctodus simus a more carnivorous bear.

Giant short-faced bear–Arctodus simus

Dan Reed’s photo-shopped reconstruction of a giant short-faced bear.   

The giant short-faced bear ranks up there with mammoths, mastodons, ground sloths, and saber-tooths as among one of the most spectacular creatures of this era.  Studies suggest it lived by aggressive scavenging.  It’s extremely acute sense of smell detected blood from a great distance.  Then, the beast would relentlessly trot toward the source of the appetizing odor, and its sheer size would intimidate the partially satiated carnivore that actually made the kill into surrendering the carcass.  Arctodus simus fossils are more common in western fossil sites, but a few have been discovered in the southeast, proving it did occur here, at least sporadically.  An Arctodus simus skeleton rested in the Fern Cave system in Jackson County, Alabama which borders northwestern Georgia, until it was discovered by cavers in 1970.  In addition a number of teeth from this species have recently been discovered in north Florida fossil sites, and some Arctodus simus material was also discovered in Virginia.

Grizzly bear–Ursus arctos

Photo of a grizzly bear and cub from google images.

Welsh cave in Kentucky yields grizzly bear fossils dating to about 12,000 BP.  This is the easternmost known occurrence of this species.  Grizzly bears roam hundreds of miles, so it’s likely if they lived in Kentucky then that they must have entered Tennessee.  But the lack of grizzly bear fossils in other southeastern states suggests they never penentrated the region in significant numbers.  Still, I believe a few irregular stragglers may have wandered into what’s now north Georgia.  It may be that the existence of 3 or 4 other species of bears prevented grizzly bears from colonizing much of the southeast during the Pleistocene, and then man arrived, creating another obstacle blocking their migration into the region.  Grizzly bears are a relatively recent addition to North America’s mammalian fauna, but they did live on the continent prior to the LGM, 30,000 years BP.  They’re the same species as the Eurasian and Alaskan brown bears.

If I could live in the Pleistocene (part 4).

For those unfamiliar with this blog, I occasionally fantasize living during the Pleistocene but with modern conveniences, such as an adobe house with woodstoves, solar heating, electricity, and a time tunnel that connects me to the modern world.

I’ve thought of a simple way to observe bears from my abode.  Connected to my Pleistocene house is a 5 story watchtower designed in the shape of a lighthouse in which I can view the surrounding landscape.  I would take a barbecue grill to the fifth story which has a canopy but an open window stretching for 360 degrees around.  There, I would grill meats.  The aroma should attract bears and other carnivores from miles around.  A bear could potentially climb up the side of a light-housed shaped building, so I would have to have some kind of designed guards that would prevent this. 

I would avoid hunting bears, if possible.  I think modern hunters who kill bears are jerks.  I can understand why the pioneers did it.  They didn’t have grocery stores and had to eat and make use of what they could obtain.  But there is no reason to hunt bears today, unless they prove a danger to tourists.  They don’t reproduce as rapidly as deer, and it’s just not ecologically necessary to hunt them.

Bears were a valuable source of meat and fat for early settlers.  Early accounts reveal an important dish of the Indians.  The Indians frequently diced up venison (which is very lean) and fried it in bear fat.  Bear fat was also the number one source of cooking fat in New Orleans in 1800.  It was gradually replaced by lard as the settlers brought in hogs.