Pleistocene Survivors: The Amphibians

Extant species of amphibians not only survived the Pleistocene, but ancestral species withstood environmental changes that occurred in the Pliocene, Miocene, Oligocene, Eocene, Paleocene, Cretaceous, Jurrassic, and Triassic.  They may be physiologically primitive, but they’re adaptable.  Part of their ability to endure gross environmental change may be their habit of becoming dormant during unfavorable conditions such as drought or cold weather.  Amphibians can burrow into mud or forest litter, under rocks, or at the bottom of a pond and are thus protected, even if the atmosphere cooks following an extraterrestrial impact.

Amphibian fossils of extant species occur in some Georgia fossil sites.  Cavers and scientists found and identified 17 species of amphibians in Kingston Saltpeter Cave, Bartow County.  Amphiuma fossil bones associated with mammoth and bison fossils were among the treasures of the Clark Quarry fossil site near Brunswick.  Numerous fossil localities in South Carolina’s coastal plain, some dating back to the Pliocene, also are home to amphiuma fossils.  Incidentally, genetic tests determined all 3 amphiuma species descend from an ancestral species that lived 4-10 million years ago.

While reviewing existing amphibian species in Georgia along with the Pleistocene fossil record, I didn’t gain any surprising ecological insights, as I frequently do with mammals and birds.  Not many, if any, amphibian species in Georgia became extinct at the end of the Pleistocene.  However, the fossil record is incomplete, and therefore deceiving.  Reference sources on this subject are limited to a difficult to obtain academic book written by the late Alan Holman, but I’m pretty sure amphibians didn’t take the big hit that the Pleistocene megafauna did.  In any case it’s obvious that western spadefoot toads were once a continuous population with the eastern spadefoot toad.  Speciation probably occurred some time during the early Pleistocene.  And northern leopard frogs must have had a more southerly range because their present day range was under glacial ice during the Wisconsinian Ice Age.

Here’s a review of every known amphibian species in Georgia.

The Giant Salamander Family

Hellbender–Cryptobranchus allegheniensis

—Also known as devil dog, it’s restricted to fast moving mountain streams here in Georgia.  A Japanese cousin of this species grows to 5 feet long.  Wow!

The Siren Family

Dwarf siren–Pseudobranchus striatus

Lesser siren–Siren intermedia

Greater siren–Siren lacertina

—During droughts, these eel-shaped creatures encase themselves in mud and become dormant.  They “yelp” when captured.  They’re restricted to the coastal plain in state.

The Newt Family

Striped newt–Notophthalmus perstriatus

Eastern newt–Notophthalmus veridescens

The eastern is interspersed throughout the state.

The Mudpuppy/Waterdog Family

Alabama waterdog–Necturus alabamensis

Mudpuppy–Necturus maculosus

Dwarf waterdog–Necturus punctatus

Mudpuppies live in mountain streams; Alabama waterdogs live in the western part of Georgia; dwarf waterdogs live in the southeastern part of the state.

The Amphiuma Family

Two-toed amphiuma–Amphiuma means

One-toed amphiuma–Amphiuma pholeter

Three-toed amphiuma–Amphiuma triactylum

The species that lives in Georgia can grow to almost 4 feet long.  These slippery, eel-shaped animals, bite when handled.

Photo from google images.  Note the vestigial limb.

The Mole Salamander Family

Flatwoods salamander–Ambystoma cingulatum

Jefferson salamander–Ambystoma jeffersonianon

Spotted salamander–Ambystoma maculatum

Marbled salamander–Ambystoma opacum

Mole salamander– Ambystoma talpoideum

Tiger salamander–Ambystoma tigrinum

—The flatwoods salamander lives in wet pine savannahs and is often found in crayfish burrows. 

–Jefferson’s salamander doesn’t currently live in Georgia but may have occurred here during the Ice Age because most of its current range was under glacial ice. 

–Spotted salamanders live underground on forested hillsides near pools of water. 

–Marbled salamanders lay eggs when their nests fill with rain water. 

— Tiger salamanders frequently are found in my yard.  They feed upon insects, worms, mice, and other amphibians.

The Lungless Salamanders

Green salamander–Aneidas aenus

Seepage salamander–Desmognathus aenus

Southern dusky salamander–Desmognathus auriculatus

Dusky salamander–Desmognathus fuscus

Imitator salamander–Desmognathus tutor

Seal salamander–Desmognathus monticola

Mountain dusky salamander–Desmognathus ochrophaeus

Black bellied salamander–Desmognathus quadramaculatus

Two-lined salamander–Euricea blisineata

Long-tailed salamander–Eurycea longicauda

Cave salamander–Euricea lucifoga

Dwarf salamander–Euricea quadridigitata

Tennessee cave salamander–Gyrinophilus palleucus

Spring salamander–Gyrinophilus porphyriticus

Georgia blind salamander–Haideotriton wallaces

4-toed salamander–Hemidactylium scutatum

Shovel-nosed salamander–Levrognathus marmoratus

Zig Zag salamander–Plethrodon dorsalis

Slimy salamander–Plethrodon glutinosus

Appalachian woodland salamander–Plethrodon jordani

Southern red-backed salamander–Plethrodon serratus

Mud salamander–Pseudotriton montanu

Red salamander–Pseudotriton ruber

Many lined salamander–Sterechilus marginatus

—Southern dusky salamander can change color like anole lizards.

–Black bellied salamanders originally were restricted to the mountain region, but their use as fish bait has expanded their range to include an irregular inhabitation of the piedmont.

–Cave salamanders have a prehensile tail and forage in cave crevices.

–Georgia blind salamanders live in ground water in southwest Georgia.

–Slimy salamanders secrete a glue-like substance difficult to remove.

Photo from google images of a Georgia blind salamander.  They live in well water.

Burrowing Toad Family

Eastern spadefoot toad–Scaphiobus holbrooki

–This animal can survive light brush fires.

The True Frog Family

Crawfish frog–Rana areolata

Bullfrog–Rana catesbeiana

Green frog–Rana clamitans

Pig frog–Rana grylia

River frog–Rana heckscher

Pickeral frog–Rana palustrus

Northern leopard frog–Rana pipiens

Southern leopard frog–Rana sphenocephala

Wood frog–Rana sylvatiea

Carpenter frog–Rana virgatipes

—Bullfrogs eat birds, mice, other frogs, crayfish, insects, and minnows.  Their croak sounds like a cow lowing.

Photo from google images of a bullfrog.

–Green frog croaking sounds like a banjo twang.

–Pig frog croaking sounds like pigs grunting.

–River frogs and pickeral frogs have a toxic skin secretion that repels snakes.

–Southern leopard frogs escape predation by leaping into the water, making a sharp right turn, and emerging in vegetation close to shore.

–Northern leopard frogs no longer occur in state but I suspect they did during the Ice Age.

–Wood frogs live as far north as Alaska where they survive being frozen in winter.  In Georgia they live in the northern part of the state.

–Carpenter frog croaking sounds like the hammering of carpenters.

The Narrow-mouthed Frog Family

Eastern narrow-mouthed frog–Gastrophryne carolinensis

–The narrow-mouthed frog’s croaking sounds like a sheep bleating.

The Toad Family

Oak toad–Bufo quericicus

Southern toad–Bufo terrestis

Fowler’s/Woodhouse Toad–Bufo woodhousei

–The southern toad likes sandy soil in oak scrub habitat.

The Tree Frog Family

Northern cricket frog–Acris crepitans

Southern cricket frog–Acris gryllus

Pine barrens tree frog–Hyla andersoni

Bird-voiced tree frog–Hyla avivoca

Cope’s gray tree frog–Hyla chrysoscalis

Common gray tree frog–Hyla versicola

Green tree frog–Hyla cinerea

Spring peeper–Hyla crucifera

Pine woods tree frog–Hyla femoralis

Barking tree frog–Hyla gratiosa

Squirrel tree frog–Hyla squirella

Little grass tree frog–Limnaoedus ocularis

Mountain chorus frog–Pseudacris brachyphone

Brimley’s chorus frog–Pseudacris brimleys

Southern chorus frog–Pseudacris nigrita

Ornate chorus frog–Pseudacris ornata

Chorus frog–Pseudacris triseriata

–Pine forest tree frog croaking sounds like a chorus of typists.  They live at the tops of trees in open pine savannahs.

Photo from google images of a pine forest tree frog.

–Barking tree frogs have scattered relic populations.  They probably had a continuous range during warm interglacials.

–Brimley’s tree frog changes color for camouflage.

Reference:

Behler, John; and F. Wayne King

The Audubon Society field guide to Reptiles and Amphibians

Knopf

 

 

Advertisement

Tamias aristus, the Extinct Kicked-up Version of the Eastern Chipmunk

Ladds Mountain, located in northwestern Georgia, is perhaps one of the best Pleistocene fossil sites in the state and yields the most mammalian species of any, though not many are of the famous large species.  Many caves and fissures pockmarked the mountain.  During their existence, these caves afforded dens for the animal life of the time, but eventually they collapsed and eroded.  Fortunately for fascinated scientists, the calcareous flowstone mixed with red clay to preserve the fossils.

I took this photo of Ladds Mountain, Bartow County, Georgia.  A fence prevents honest people like me from trespassing to hunt for fossils.

The numerous fossils of small species found here provides intriguing clues about the paleoenvironmental conditions at the time they lived.

One of the interesting small species was the giant or noblest chipmunk (Tamis aristus).  Its anatomical characteristics were exactly the same as those of the living eastern chipmunk (Tamias straiatus) with the exception of a notable size difference–the extinct species was 10%-30% larger.

Skull comparison between the two species of chipmunks from a paper written by Clayton Ray.  Tamias aristus was larger but otherwise they’re similar.  I also notice a suture on top of the skull of the larger species that doesn’t appear on the specimen of the smaller species.

Photo of an eastern chipmunk from google images.  I chose this one because it shows the species in its favored habitat–in a rocky woodlot.  Chipmunks store food in cheek pouches and carry it to tunnels under boulders and tree roots where they hoard the food.  They become dormant during bad weather.  I believe this is why they survived the Ice Age while its larger cousin did not.  During the last interglacial it co-existed with its larger cousin.

Clayton Ray first studied the fossil remains of the giant chipmunk in the 1960’s.  He tentatively decided that it was a distinct extinct species, though he believed it may have merely been a larger subspecies of the still extant eastern chipmunk.  Today, the eastern chipmunk reaches its southernmost range limit in central Georgia.  They live around Atlanta and Athens but are absent in Augusta.  There are more rocky boulders and crevices in the piedmont than there are in the coastal plain. Chipmunks like to tunnel and den in and around big rocks.  The coastal plain is also a tad warmer, allowing chipmunk-eating snakes to be active for a longer time period of the year.  I consider these two factors to be the reasons chipmunk ranges are limited in the south to the piedmont and mountain regions.

Tamias aristus is not common in the fossil record, though that doesn’t necessarily mean it wasn’t successful and abundant for a time.  Fossil specimens have only been recovered from one site other than Ladds–Arredondo IIA, located in north central Florida.  Fossils from Arredondo IIA are thought to be Sangamonian in age.  The Sangamonian was a warm interglacial period lasting from ~132,000-~118,000 years BP.  No good radiometric dates from any of the fossils found at Ladds have ever been recorded, indicating the fossils were too old for carbon dating (carbon dating isn’t possible for fossils older than 50,000 years).  As far as I know uranium series dating and pottasium-argon dating have never been attempted or aren’t possible here.  However, fossil specimens of the extinct giant tortoise (Hesperotestudo crassicutata) and the Florida red-bellied turtle (which today only occurs in Florida) were recovered from Ladds–evidence that the fossils accumulated here during a period of time when the climate was much warmer than that of today.  This also fits Ladds in with a Sangamonian interglacial age along with Arredondo IIA.

Conversely, a few species found at the site indicate cooler climate as well, but it’s not a convincing list–none are definitively dependent on a cooler climate–and it’s unclear whether fossils of different ages are mixed here.  The late Dr. Alan Holman, North America’s foremost authority on Pleistocene reptiles and amphibians, studied the cold blooded vertebrates found at Ladds, and he determined the all lived here during the same phase of climate.  In my opinion  based on the preponderance of temperate and warm weather species, the Ladds fauna is probably from a full blown interglacial period.

Dr. Alroy tackled the problem of determining the age of fossil sites hampered by the lack of quality radiometric dating.  Using the known ages of species appearances and disappearances in the fossil record as a kind of index, he estimates the ages of sites.  He calls this “appearance event ordination” or AEO.  This method is necessarily a very rough and inexact estimate.  Nevertheless, he estimated the age of the fossils found at Ladds to be about 300,000 years old.  One of the species he uses as an index for Ladds is the Vero tapir.  He placed the Vero tapir as existing until 300,000 years BP, but I believe he made a mistake.  Bjorn Kurten considered the Vero tapir to be the common southeastern species of tapir until the megafauna extinction of ~12,500 years BP.  Moving the disappearance date of the Vero tapir changes the estimated date of Ladds fossils.  I have no way of knowing for sure, of course, but because the species of fossils here are so similar to those at Arredondo IIA, I suspect it’s also Sangamonian in age.  I’m more certain that the animals here did live during an interglacial of some kind, if not the Sangamonian, than the Yarmouthian (~200,000 BP) or the Aftonian (~300,000).

Tamias aristus  apparently co-existed with Tamias striatus because the fossils of both are found at Ladds.  They obviously share a common ancestry, probably evolving from the same species.  I hypothesize that their ancestor evolved along two lines:  the larger species grew bigger because it foraged year round, while the smaller species became dormant during bad weather.   Both species did well in the rich oak and chestnut forests of the interglacial age and perhaps well into the early Wisconsinian Age when the climate was still mild.  But as the climate became drier and cooler, grassland replaced forests.  The remaining forested areas provided limited habitat, and the smaller chipmunk adapted better.  I believe the smaller chipmunk had a survival advantage because it became dormant during the bad weather of the Ice Age.  The larger chipmunk could function year round–an advantage in a warm climate.  But it lost that advantage during the Ice Age and instead became victim more frequently to hungry predators in winter, while its smaller cousin stayed hidden and safe during times of the year when food became scarce for carnivores.

Here’s the list of mammalian species found at Ladds and Arredondo IIA.  Notice the striking similarities.  Note: there were other species living near these sites that never perchance left fossil evidence at either one. 

* denotes species found at both sites.  X denotes extinct species.

Mammalian species found at Ladds

*opposum

masked shrew

smoky shrew

*short tailed shrew

*eastern mole

little brown bat (cf)

gray myotis

eastern pipistrelle

big brown bat

*X Jefferson’s ground sloth (probably)–Ray refers to it as species indetermined

*X beautiful armadillo

* New England cottontail–I think it a rather dubious feat to be able to determine subspecies based on a few fossil bones.  This may have been a large subspecies of interglacial rabbit that grew this size due to high quality foraging in a rich forest

*X Noblest chipmunk

Eastern chipmunk

woodchuck

beaver

* rice rat

deer mouse

white footed mouse

X unnamed extinct species of mouse in the Peromyscus genus

* cotton rat

*woodrat

*Florida muskrat

muskrat

southern bog lemming

meadow jumping mouse

*X dire wolf (probably)–Based on one tooth, Clayton Ray considered it to compare favorably to the gray wolf.  Dr. Nowak, the foremost authority on Pleistocene canids, later looked at this tooth, and wrote that it did fall within the size range of dire wolf.  Because Ladds probably dates to the Sangamonian interglacial, it must belong to a dire wolf because gray wolves didn’t colonize North America yet.

*gray fox

black bear

X Florida spectacled bear

raccoon

fisher

* long tailed weasel (cf)

spotted skunk

striped skunk

hog-nosed skunk

river otter

* jaguar

cougar

* bobcat

X river cat–Scientists are unsure whether this was a distinct extinct species, a margay, or a jaguarundi. 

*X Vero tapir

horse

*X long nosed peccary

*X flat-headed peccary

* white tailed deer

X at least one species of unidentified ungulate, the teeth were in too bad a condition to determine the species

5 species of birds left fossils here too, including turkey, black duck, ruffed grouse, passenger pigeon, and a perching song bird

Dr. Holman recoded 22 species of reptiles and amphibians

Mammalian species found at Arredondo IIA

*Opposum

*X Jefferson’s ground sloth

*X beautiful armadillo

* short-tailed shrew

* eastern mole

least shrew

northern yellow bat

southeastern myotis

X Pleistocene vampire bat

eastern pocket gopher

southeastern pocket gopher

southern flying squirrel

*X noblest chipmunk

gray squirrel

*Florida muskrat

Florida mouse

cotton mouse

old field mouse

woodland vole

meadow vole

X Florida bog lemming

harvest mouse

* cotton rat

* rice rat

* wood rat

golden mouse

* rabbit in the cottontail genus

* long tailed weasel

*dire wolf

*gray fox

* jaguar

* bobcat

*X Vero tapir

*X long-nosed peccary

*X flat-headed peccary

* white tailed deer

X upland bison–Bison antiquus

X long-necked llama

X big headed llama

The paleodatabase lists 15 amphibians but just one reptile as being recovered here.  I think this is incomplete.  I believe more reptiles than that were found here but just haven’t been listed on that source.  42 species of birds, including 3 extinct kinds were found here, but again, they’re not listed on the paleodatabase.

The predominant environment at both sites during the Sangamonian interglacial was probably a rich oak and chestnut hardwood forest interspersed with small prairies and dotted with swamps and marshes.

References

Holman, Alan

“The Herpetofauna of Ladds Quarry”

National Geographic Research 1 (3) 1985

Ray, Clayton

“Pleistocene Mammals from Ladds, Bartow County, Georgia

Bulletin of the Georgia Academy of Science 25 (3) 1968

The paleodatabase.

(I’m still trying to get my hands on a copy of Clayton Ray’s 1965 paper devoted exclusively to the extinct chipmunk.  If I do, I’ll write another entry with any new details I learn.)