Archive for December, 2017

Pleistocene Fish of the Tennessee River System

December 28, 2017

Many Italians like to celebrate Christmas Eve with the feast of the 7 fishes.  I’m not Italian, but I like to eat seafood during the holiday season too, though my immediate family is small, and we enjoy the feast of the 2 fishes.  I wonder what species would’ve composed a feast of fishes for Paleo-Indians when they first entered the Tennessee River Valley.  Fish populations were much higher in the pristine pellucid waters of all southeastern rivers before man began destroying the environment, but the composition of species is poorly known because fish remains that old are rarely preserved.  A new study of fish remains excavated from Bell Cave partially unveils this mystery.  Bell Cave in Colbert County, Alabama overlooks the Tennessee River and floods periodically stranded fish inside the cave from ~13,000 calendar years BP-~30,000 calendar years BP.  Predators carried fish into the cave as well.  Scientists collected vertebrate bones from this cave between 1984-1987, but no one identified the fish remains and published the data until 2016.  This study also catalogued fish remains from other sites near the Tennessee River including Baker Bluff Cave, Beartown Cave, Guy Wilson Cave, Cheekbend Cave, Dust Cave, Little Bear Cave, Appalachian Caverns, and Saltville.

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Map of the Tennessee River.

The authors of this study identified 41 taxa and 38 species that lived in the Tennessee River during the late Wisconsin Ice Age.  The number of species they identified is a subset of the population that actually swam in the river because, by chance, many species just never got trapped in the cave or were too decayed to be identified.  This is especially true for smaller species.  Almost all of the species they identified still live in the Tennessee River system today, but there are 3 exceptions.  Northern pike (Esox lucius) no longer naturally occurs this far south, although man has introduced this species into some bodies of water.  (Muskellunge, a related species, surprisingly still occurs in the Tennessee River.  Fossil evidence suggests they were fairly common here during the Ice Age.)  Northern madtom (Noturus stigmosis), a small species of catfish, also no longer occurs this far south. The harelip suckerfish (Moxostoma lacerum) became extinct during the late 19th century.  This species required very clear water with gravel bottoms, but deforestation and agriculture caused erosion that muddied its spawning grounds.  Pleistocene rives were clear enough for this species.

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Northern pike.

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Northern madtom.

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Harelip sucker.

Rock bass were the most commonly represented fish from the Centrarchidae family catalogued in this study, but curiously they found not a single specimen of sunfish.  Bluegill sunfish are 1 of the most common fish in the Tennessee River today because they thrive in manmade reservoirs, but that kind of environment was rare before man began impounding rivers.  Sunfish probably lived in oxbow lakes that weren’t close enough to caves where their remains could’ve been preserved.

A Paleo-Indian trapping fish in the Tennessee River could’ve enjoyed a feast of 7 fishes consisting of sturgeon, northern pike, walleye, sauger, freshwater drum, bullhead catfish, and eel.  These were probably the best tasting fish available to them then.

Reference:

Jacquemin, S.; J. Ebersole, W. Dickinson, G. Ciampaglio

“Late Pleistocene Fishes of the Tennessee River Basin: an Analysis of a Late Pleistocene Freshwater Fish Fauna from Bell Cave (site Acb-2) in Colbert County, Alabama”

Peer J 2016

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The Presence of Caribou in Southeastern North America during the Pleistocene and it Paleoecological Implications

December 19, 2017

 

The reindeer, legendary conveyor of Santa’s sleigh, is an Holarctic animal, meaning it lives south of the Arctic Circle in both North America and Eurasia.  In North America the reindeer is more commonly known as caribou.  When Europeans colonized the New World caribou lived as far south as upstate New York, but today their range in North America is restricted to Canada and Alaska.  During Ice Ages, however, almost all of their present day range was under glaciers–unsuitable habitat even for such a cold hardy animal.  Caribou range shifted south then, and caribou fossil material has been found at numerous southeastern sites including Bell Cave in Alabama, Yarbrough Cave in Georgia, 3 caves in Tennessee, off the North Carolina coast, off Myrtle Beach, and in Charleston, South Carolina (the most southeastern known occurrence).  Apparently, caribou occurred at least as far south as the piedmont region.

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Reindeer and Caribou are the same species.
Caribou fossils have been found associated with an interesting mix of species at the above-mentioned fossil sites, though it’s unclear if they all lived at those localities during the same climatic phases.  Cave and offshore sites can collect the bones of animals from many different time periods.  Nevertheless, caribou bones have been found with the remains of giant beavers, flat-headed peccary, long-nosed peccary, woodland muskox, white tail deer, stag-moose, horse, tapir, mastodon, ground sloth, jaguar, and dire wolf.  Pleistocene caribou in eastern North America likely preferred open spruce woodlands interspersed with prairies.  This habitat would have also been favorable for horse, flat-headed peccary, bison, and mammoth.  By chance caribou remains haven’t been found with the latter 2, but they probably co-occurred at some locations.  Dire wolves, habitat generalists, likely co-occurred with caribou as well and probably preyed on them.
Baker Bluff Cave in northeastern Tennessee has well stratified deposits that contain many vertebrate bones from 2 different climate phases.  Information from this site can help determine the faunal composition that co-occurred with caribou.  The oldest deposits at Baker Bluff Cave are interpreted as representing a temperate forest consisting of oak, northern pine, birch, beech, etc.  Gradually, this environment gave way to the open spruce woodland/prairie as the climate became colder and drier during the Last Glacial Maximum.  White-tailed deer remains are abundant throughout all layers of the deposit, and they co-occur with caribou in Canada today, so undoubtedly they were a contemporary of Pleistocene caribou.  Long-nosed peccary, a forest edge species, like white-tail deer, likely co-occurred with caribou as well.  Mastodon, giant beaver, and stag-moose inhabited wetland environments adjacent to caribou habitat, and I’m certain they were contemporaries with caribou.  Woodland musk-ox, another likely contemporary, foraged in shrub habitat near caribou range.
A jaguar tooth found at Baker’s Bluff Cave was excavated from the lowest oldest level.  This is evidence Pleistocene jaguars inhabited cool temperate forests, but it seems unlikely they survived in the region when the forest gave way to boreal environments.  However, caribou may have also occurred in the southeast during interstadials.  (Good carbon-dating of regional caribou fossils has yet to be conducted.)  It’s impossible to determine from available data whether jaguars inhabited the same range as caribou.  The same can be said for the tapir, a species that preferred thick forest.
Cave deposits contain an even greater abundance of small vertebrate fossils.  Most smaller animals are more restricted to certain environments than larger species, and their composition better reveals what natural communities of this locality were like.  The Baker Bluff Cave deposits are particularly interesting.  Fossil material of species still found in the region today (gray squirrels, eastern chipmunks, southern flying squirrels) were present throughout the deposit but were less common during the open spruce woodland/prairie phase.  By contrast some species that today live to the north and west of the region (13-lined ground squirrels, least chipmunks, northern flying squirrels, badgers, pine martens, fishers, magpies) were also found throughout the deposit but were less common during the cool temperate forest stage.  Red squirrels were also less common during this phase but more common after the landscape changed.  Fossil remains of 13-lined ground squirrels have been excavated from sites throughout the southeast but no longer occur east of the Mississippi.  Fossil material of birds that prefer open spaces such as upland sandpiper and prairie chicken were excavated from Bell Cave and Yarbrough Cave.  The presence of these species is evidence prairie habitat was common in the region during Ice Ages.  Pine marten specimens, dating to the Pleistocene, were discovered as far south as northern Alabama, and Pleistocene fisher specimens turned up in northern Alabama and north Georgia.  This is evidence of boreal environments in the upper south.
I hypothesize Ice Age ecosystems in southeastern North America were more diverse than they are today due to rapid climate fluctuations.  Climate phases of warm wet interstadials (but cooler on average than today) and cold arid stadials alternated but the response of the floral and faunal composition to these rapid climate changes lagged behind.  Some climate phases lasted for a few thousand years or perhaps just centuries or even decades.  They weren’t long enough to completely eliminate habitat for species with warm temperate affinities, nor did they last long enough to extirpate habitat favorable for species with boreal affinities.  This explains why eastern chipmunks co-occurred with least chipmunks, and why caribou may have shared the range with jaguars and tapirs.  During cold phases though prairie and boreal forest expanded, oak woodlands persisted on some tracts of land, especially south-facing slopes.  During warm phases oak woodlands expanded, but spruce forests persisted on north facing slopes.
Herds of caribou formerly wandered through Georgia followed by packs of dire wolves and prides of lions.  The herds traveled through fingers of prairie between open woods consisting of pine and spruce and oak where turkeys foraged on the ground and fishers chased gray squirrels through the tree tops.  Landscapes of present day Georgia are unrecognizable by comparison.
Reference:
Guilday, John; H. Hamilton, E. Anderson, and P. Parmalee
“The Baker Bluff Cave Deposit, and the Late Pleistocene Faunal Gradient”
Bulletin of the Carnegie Museum 1978

The Large Otter (Enhydritherium terraenovae) of Miocene North America

December 13, 2017

A large otter lived across North America during the Miocene and early Pliocene from at least 6.5 million years BP to about 4.5 million years ago.  Fossils of this extinct species weren’t discovered until 1985 at a site known as Palmetto Mine located in Florida.  Scientists examined the material (a jaw and teeth) and gave it the scientific name Enhydritherium terranovae.  They assumed this species of otter subsisted mostly on marine shellfish because its teeth resembled that of the extant sea otter (Enhydra lutra).  Though sea otters eat some fish and cephalopods, a great part of their diet consists of shellfish. However, a nearly complete skeleton was later discovered at the Moss Acres Race Track site located about 75 miles from where the coastline was when the specimen died.  A concentration of fish bones, otherwise rare at the site, was found in the matrix alongside the otter specimen.  Scientists interpreted the concentration of fish bones as the stomach contents of this particular otter.  This species ate fish and shellfish.  Scientists now believed Enhydritherium occupied both fresh and salt water habitats, but still thought of it as a coastal species.  Fossil remains of Enhydritherium have been discovered at 8 sites in Florida and 3 in California, so scientists wondered how a coastal species dispersed from Florida to California.  A recent discovery of Enhydritherium bones in Mexico about 125 miles from the Gulf of Mexico (and even farther from the Pacific) solves this mystery. Enhydritherium was not a coastal species, but instead occurred in freshwater habitats well inland.  Enhydritherium likely followed river systems and could travel overland for considerable distances between water sheds much like modern day river otters (Lontra canadensis) do.  I’ve seen road-killed river otters and beavers many miles from the nearest creek.

Enhydritherium exceeded the size of all extant species of otter.  They averaged 50-100 lbs.  By contrast sea otters and the giant otter of South America (Pteronura brasiliensis) normally reach maximum weights of 75 lbs. Enhydritherium also differed from modern otters in the way they swam.  Modern otters use all 4 limbs but rely primarily on their legs when they swim.  Enhydritherium had robust forelimbs, and most of their propulsion came from their arms instead of their legs.

At the Moss Acres Race Track site the Enhydritherium skeleton was found in association with the bones of rhino, horse, gompothere, and borophagine dog.  Rhinos became extinct in North America about the same time Enhydritherium did.  This faunal turnover occurred when Ice Ages began cycling.  Nevertheless, Florida, southern California, and Mexico remained subtropical during Ice Ages. Pollen evidence from the Moss Acres Race Track included oak, pine, and grass; but no tropical species.  The reason for the end of Miocene faunal turnover is unknown and probably complex.  Perhaps ecological changes caused by climate change and competition with new species were factors.

Today, there are 13 species of otters in the world.  The North American river otter and the Eurasian otter (Lontra lutra) probably descend from an extinct genus known as Satherium which was widespread during the Pliocene.  Several South American species may also descend from this genus, but genetic analysis suggests the giant otter of Brazil is most closely related to the smooth-coated otter of the Far East.  Evidentally, there was more than 1 otter dispersal from Eurasia to the Americas.

River otter fossil material is fairly common at Pleistocene-aged fossil sites in southeastern North America including Ladds, Bartow County, Georgia.  They thrive wherever they can find enough fish to eat.  Presently in Georgia, river otters are most abundant in coastal plain rivers and salt marshes, but their population gradually decreases upriver until they are rare but present in the mountain region.  I’ve been seeing more road-killed otters in recent years.  Maybe it is coincidence, but I believe fur-trapping in going out of style, and river otters are on the increase as a result.

References:

Lambert, W.D.

“The Osteology and Paleoecology of the Giant Otter Enhydritherium terraenovae”

Journal of Vertebrate Paleontology 17 1997

Tseng, Jack Z.; et. al.

“Discovery of the Fossil Otter (Enhydritherium terranovae) Carnivora; Mammalia in Mexico Resolves a Paleoecological Mystery

Biology Letters 13 (6) June 2017

https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/enhydritherium-terraenovae/

 

Capybaras and Hippos Take II

December 6, 2017

(Note: I tried publishing this post yesterday but due to undetermined technical difficulties the text disappeared.  Hopefully, this entry will have text.)

I planned on writing a blog article about Pleistocene capybaras of southeastern North America, but when I began researching the topic on google I discovered I’d already written a pretty good essay 2 years ago.  (See: https://markgelbart.wordpress.com/2015/12/07/megafauna-habitat-modification-and-pleistocene-capybaras-in-southeastern-north-america/https://markgelbart.wordpress.com/2015/12/07/megafauna-habitat-modification-and-pleistocene-capybaras-in-southeastern-north-america/ ) I’ve written 601 articles for my blog, and it’s hard for me to remember everything I’ve already covered.  Much to my disappointment, there has been little recent academic research about the extinct species of capybaras.  There were 2 species that lived in Florida, Georgia, South Carolina, and probably the Gulf States during the Pleistocene–Neochoerus pinkneyi  and Hydrochoerus holmesi.  Both were more than twice as large as the 2 extant species of capybaras that are presently confined to Central and South America near the equator.  I hypothesize the extinct species could endure somewhat colder air temperatures than their modern day kin due to their larger size.  Nevertheless, they probably extended their range during warmer wetter climate cycles. In my previous blog entry linked above  I think I mentioned how capybaras occupy an ecological niche similar to that occupied by African hippos.  Both are aquatic species that graze adjacent water’s edge marshes into lawn-like environments.  But I didn’t note the remarkable evolutionary convergence in the physical appearance between the 2 unrelated animals.

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Capybara and young.

Convergent evolution is when 2 unrelated organisms evolve similar characteristics to adapt to similar environments.  Capybaras and hippos have similar height to weight ratios.  They also share other characteristics such as small round ears, short necks, square faces, and thick hides.

Hippos remind me of ancient extinct animals from earlier ages…like the kind of monstrous beasts of the Miocene or Eocene.  They should be appreciated for their resemblance to primitive extinct evolutionary dead-ends and ancestral species.  Hippos are most closely related to whales, having shared a common ancestor 28 million years ago known as Epirigenys lokonensis. Hippos resemble the primitive ancestors of whales.

Several extinct species of hippos were widespread in Europe during the Pleistocene but disappeared during the Last Glacial Maximum when available habitat shrank into small refugia where they were more easily hunted into extinction by man. Several species of hippos were also driven into extinction when man colonized Madagascar.  Dwarf species of hippos lived on the Mediterranean Islands of Crete, Cyprus, Sicily, and Malta until man discovered those places.  Just 2 extant species of hippo remain —Hippopotamus amphibious and Hexaprotodon lieberiensis. 

Hippos are the most dangerous non-human vertebrate in Africa.  They are responsible for an average of 2900 deaths every year.  However, mosquitoes and flies spread tropical diseases that kill about 655,000 people annually.  Paradoxically, these tiny pests are a greater hazard than a 2 ton hippo.