Archive for the ‘Pleistocene Mammals’ Category

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
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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.

 

 

The Sitzkrieg Hypothesis

November 21, 2017

The authors of a new statistical analysis of megafauna extinctions boast their method is superior to previous efforts, and they can’t reject human interactions as a cause of the extinctions.  However, they also can’t rule out climate change as a factor, so despite their supposed superior method, their new study (referenced below) resolves nothing.  The statistical method they used is known as kriging, a kind of interpolated algorithm.  The data included 95 of the last radiocarbon dates of megafauna species and 75 of the earliest dated archaeological sites in North America.  They then mapped the last appearance dates of the megafauna with the earliest archaeological evidence of humans.  They concluded climate change caused the extinction of mastodons in Alaska because this species disappeared there long before humans colonized the region, but humans may have been a factor causing extinctions at lower latitudes.  Megafauna persisted until the very end of the Pleistocene in some regions including Mexico, Texas, Tennessee, and the Great Lakes region.  Humans may have overlapped in these regions for as long as 3000 years.  The study doesn’t find much evidence for the blitzkrieg (rapid overhunting) model of extinction, though there may have been “localized” examples of this in western North America.  But it is possible humans gradually disrupted ecosystems in a way that was detrimental to megafauna populations.  This is known as the sitzkrieg model of extinction, and it is the scenario that makes the most sense to me.

There is a major flaw in the reasoning behind the conclusions of this study.  The authors of this study equate the regional disappearance of a species with its extinction.  For example mastodons became extirpated in Alaska about 30,000 years ago, but they did not become extinct.  Populations remained robust south of the ice sheet until about 13,000 years ago.  If man never colonized North America, it seems likely mastodons would have re-colonized Alaska and Canada during the present day interglacial.  Habitat in present day Canada and Alaska is very much like that of some Ice Age regions mastodons formerly inhabited before their extinction.  Mastodons were a wetland species, and aquatic habitats have greatly expanded in Canada and Alaska since the end of the Ice Age.  (During the Last Glacial Maximum Canada was covered by ice sheets and Alaska was an arid grassland–both unsuitable environments for mastodons.)  Climate change may have driven the redistribution of megafauna geographic ranges, but that is not the same as extinction.  During climate phases that favored the expansion of grassland, woodland species were forced to migrate farther to find suitable habitat, and vice versa.  Again, this is not extinction…it is a species adjusting to a new range map.

I’m convinced man, and man alone, is responsible for the extinction of the Pleistocene megafauna.  These wide-ranging species (some occurred all across the continent) were adaptable species that survived dozens, if not hundreds, of dramatic climatic swings over hundreds of thousands of years.  But when man begins to appear in the archeological record, they disappear permanently.  There is no way that can be coincidental. I think man disrupted the ecological balance through a combination of overhunting, increased fire frequency, and interdiction of migratory corridors.  It took a few thousand years, but when human populations reached a certain level, most species of megafauna could not adapt.  They required an ecosystem with low levels of people and did even better with no humans on the landscape at all.

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Graph of average annual temperatures over the past 150,000 years based on data from Greenland ice cores.  Note all of the dramatic climate fluctuations.  Megafauna species survived these climate fluctuations but became extinct in North and South America within a few thousand years of when man entered the continents.

Reference:

Weatherall, M.; Brianna McHorse, and E. Davis

“Spatially Explicit Analysis Sheds New Light on the Pleistocene Megafaunal Extinctions in North America”

Paleobiology November 2017

The Eurasian and North American Scimitar Cats may have been the Same Species

November 1, 2017

The scimitar cat roamed Eurasia and North America for millions of years until its extinction about 11,000 years ago.  This apex predator sported fangs and was about the size of a lion.  Evidence from Friesenhahn Cave in Texas suggests it preyed upon juvenile mammoths and mastodons as well as peccaries.  A study of bone chemistry in Europe indicates 1 specimen ate yaks.  The scimitar cat is not as well known as the more robust saber-toothed cat (Smilodon fatalis) that apparently was restricted to North and South America.  Another species of saber-toothed cat (S. populator) occurred in eastern South America.  Remains of scimitar-toothed cats are uncommon in the fossil record.  Entire skeletons were found in Friesenhahn  Cave, but elsewhere, if evidence is excavated of scimitar cat, it is usually just a single bone or tooth.  This reflects low populations compared to the prey species it fed upon.  Generally, large carnivores are less common at fossil sites than the species they depended upon for food because predators are necessarily less abundant than their prey.  This low population caused an huge gap in the fossil record of Eurasian scimitar-toothed cats.  There was no evidence of scimitar-toothed cats in Eurasia after 300,000 years BP until the jaw bone of 1 individual was netted by a fishing boat in the North Sea a few years ago. (Much of the North Sea was above sea level during Ice Ages.)  This new specimen dates to 28,000 years BP.  There is also 1 stone statuette that may or may not be of a scimitar-toothed cat–the identification is unclear.  Thousands of generations of this species lived on the continents of Europe and Asia, but this is all the evidence we have of scimitar-toothed cats living there during the late Pleistocene.

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Illustration of scimitar cat.

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This Pleistocene-aged stone statuette may be a representation of a lion or a scimitar-toothed cat.  The deep chin, evolved to protect the fangs, and the bob-tail are evidence it represents Homotherium.  However, the absence of fangs and straight back (Homotherium had a sloping back) indicate it represents a lion.  Unfortunately, this artifact was lost a century ago.

Scientists analyzed the DNA from the North Sea specimen and compared it with the DNA from specimens of scimitar-toothed cats from the Yukon, Canada and some specimens of South American Smilodon populator. They determined the lineage of scimitar-toothed cats (Homotheridae) diverged from the lineage of saber-toothed cats (Smilodontheridae) 18 million years ago.  Despite their similar convergent appearance they were about as closely related to each other as house cats are to tigers.  The genetic study also suggests the Eurasian scimitar-toothed cats (Homotherium latidens) and the North American scimitar-toothed cat (H. serum) should be considered the same species.  The authors of the study found “low genetic diversity despite wide geographical occurrence.”  However, the specimens the scientists used in the study were north and west of the ice sheet that cut most of North America off from Beringia and Eurasia.  Scientists need to study DNA from specimens south of the ice sheet to conclusively show H. latidens = H. serum. A previous genetic study of lions (Panthera spelea, P. leo, and P. atrox) determined North American lions south of the ice sheet were a different species than those north of it.

Reference:

Anton, Mauricio; et. al.

“Soft Tissure Reconstruction of Homotherium latidens (Mammalia, Carnivora, Felidae): Implications for the Possibility of Representation in Paleolithic Art”

Geobios  42 (5) 2009

Paijmans, Johanna; et. al.

“Evolutionary History of Saber-toothed Cats Based on Ancient Metagenomes”

Current Biology (in press)

 

The North Charleston Mastodon

October 8, 2017

Construction workers digging a foundation for a building in North Charleston, South Carolina 5 years ago uncovered the remains of a mastodon.  Bones including a partial tusk, femur, vertebrae, jaw, ribs, and feet were excavated.  One scientist also examined the surrounding sediment for pollen and plant remains. Apparently, the site was riverbank, and the mastodon likely was covered in flood-borne sediment.  I hope a paper is published detailing the information yielded by this site.  So far, all the information I can find comes from 2 abstracts that described poster presentations of the find at scientific meetings.  The authors didn’t even put the posters on the internet.

One presentation compared the pollen found here to that from other Pleistocene-aged sites located near the present day coast–St. Catherine’s Island, Reid’s and Bell’s Bluff, and a site along the Georgia-Florida border.  All of these sites were farther inland during Ice Ages.  Like these other sites, the North Charleston locality had a strange admixture of species presently found at higher latitudes with those still found in the region.  Water milfoil, an aquatic plant, occurred here.  This is not surprising because mastodons were semi-aquatic.  Hickory pollen was “unusually” abundant, indicating a moist temperate climate, but the pollen of red pine, a northern species, was found in association with sub-tropical Spanish moss.  Other Pleistocene sites in the region yield hemlock, basswood, and walnut–species no longer found this far south.  However, I’m skeptical about the identification of supposed red pine pollen.  This species currently occurs in New England, a region that was under glacial ice for much of the Ice Age when its range was forced south.  I doubt it occurred as far south as South Carolina though because there are no relic populations in the southeast.  Red pine pollen is distinguished from pollen of southern pines on the basis of size.  Pollen grains under 43 micrometers in size are classified as northern species of pine, while those over 43 micrometers are thought to be from southern pines.  Shortleaf pine is a common southern species of pine whose pollen grains overlap in size with red pine pollen grains.  Moreover, under the atmospheric conditions of low CO2 as occurred during Ice Ages, shortleaf pine pollen grains may have been slightly smaller than those of the present day.  In my opinion they look identical as the below photos show.  I believe pollen classified as red pine in the below reference and several other studies is from shortleaf pine which is still widespread in the region.

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Shortleaf pine pollen grains average a “maximum” 50-75 micrometers in size.

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Photos of northern species of pine pollen grains including red pine (Pinus resinosa), jack pine, and white pine.  Red pine and white pine pollen grains easily overlap in size with shortleaf pine.  Therefore, I’m not convinced of palynologists’ claim that red pine occurred in the southeast during Ice Ages.

Reference:

Rich, Fred

“The North Charleston Mastodon Site–New Insights Drawn from Paleoecological Synthesis”

The Geological Society of America: Southeastern Section–64th annual meeting

 

New Species of Late Pleistocene Ground Sloth and Peccary Discovered on Yucatan Peninsula

September 13, 2017

My ongoing mission to catalogue the faunal composition of piedmont Georgia as it was during the late Pleistocene is but an educated guess.  I base my guess on the lone fossil site in the region plus fossil sites located to the north, south, and west of the piedmont.  (See for my list: https://markgelbart.wordpress.com/2013/12/27/if-i-could-live-during-the-pleistocene-part-xii-my-mammal-checklist/ ) I think I know most of the mammal species that occurred here during the Pleistocene, but there were probably species living in the region I never would have guessed.  Even in regions with many Pleistocene-aged fossil sites, scientists are still discovering the presence of new species.  Within the last 5 years paleontologists identified giant short-faced bear (Arctodus simus) and collared peccary (Tayassu tajacu) specimens in Florida where these species were not formerly known.  The dhole (Cuon alpinus) crossed the Bering land bridge sometime during the Pleistocene, yet the only fossil specimens of this species in North America were found at 1 site in Mexico.  This means all the dholes that lived between Alaska and Mexico left zero fossil evidence, or at least none that has been found to date.  And now, just within the last 2 years, scientists have identified 2 new species of large mammals that lived on the Yucatan peninsula during the late Pleistocene.

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Map of the Quintana Roo province on the Yucatan Peninsula.  Evidence excavated from sinkhole caves indicates an unique fauna resided here during the late Pleistocene.

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Skull of Xibalbaonyx oviceps found in Yucatan sinkhole.

The Yucatan peninsula is dotted with numerous sinkholes and caves because rain water unevenly dissolves underlying limestone bedrock.  The sinkholes and caves preserve remains of animals for tens of thousands of years.  Cave divers have discovered the bones of gompotheres, glyptodonts, ground sloths, llamas, horses, tapirs, peccaries, spectacled bears, saber-tooths, bobcats, rabbits, fruit bats, and humans in these subterranean spaces.  (I’m aware of 4 mostly complete human skeletons found in Yucatan sinkholes and caves–1 dating to the incredibly early date of 14,350 calendar years BP.)  Bones of Shasta ground sloths and collared peccaries are among the specimens recovered here, but relatives of each, previously unknown to science, have recently been described in the scientific literature.  The new ground sloth species was identified from a specimen found in the Zapote sinkhole.  It was a mostly complete skeleton of a sub-adult that weighed at least 500 pounds when it was alive.  It is thought to have been adapted to a desert grassland environment.  Scientists gave it the unpronounceable scientific name–Xibalbaonyx oviceps.  It was closely related to Jefferson’s ground sloth (Megalonyx jeffersonii), a species that occurred all across North America from Florida to Alaska.  Perhaps X. oviceps was a desert offshoot of Jefferson’s ground sloth.  The new species of peccary was given the more pronounceable scientific name of Mucknalia minimas. I haven’t been able to obtain a copy of either paper describing the new species.  When I do I may write an addendum to this blog entry.

The presence of 2 species seemingly endemic to the Yucatan peninsula indicates the region was ecologically unique.  The area around the Hoyo del Negro fossil site (See: https://markgelbart.wordpress.com/2015/08/08/the-hoyo-negro-fossil-site-in-yucatan-mexico/ ) was a mix of tropical forest, thorny scrub, and wetland; but further inland desert grassland predominated.  I think small sinkhole lakes, like oases, probably existed in drier areas.

Who knows?  Maybe the piedmont region of southeastern North America hosted endemic large mammal species during the Pleistocene that are currently unknown to science.  Unfortunately, the lack of sites suitable for fossil preservation in the region could keep them cloaked in mystery for eternity.

On an unrelated note: While researching this blog entry, I learned about a llama specimen (the extinct  Hemiauchenia macrocephela) found in a Yucatan cave that was apparently butchered, cooked, and eaten by humans.  This information doesn’t seem to be generally known in the archaeological literature.

References:

Gonzalez, Arturo: et. al.

“The Arrival of Humans on the Yucatan Peninsula. Evidence from Submerged Caves in the State of Quintana Roo, Mexico”

Current Research in the Pleistocene January 2008

Stinnesbeck, S.; et. al.

“A New Fossil Peccary from the Pleistocene-Holocene Boundary of the Eastern Yucatan Peninsula, Mexico”

Journal of South American Earth Science 2016

Stinnesbeck, S. et. al.

“Xibalbaonyx oviceps, a New Megalonychid Ground Sloth (Folivora: Xenarthan) from the Late Pleistocene of the Yucatan Peninsula, Mexico and its Paleogeographic Significance”

Palz 91 June 2017

 

How Far South did the Wolverine (Gulo gulo) Range during Ice Ages?

September 7, 2017

The voracious wolverine preys upon deer, caribou, and even moose when these much larger mammals flounder in deep snow.  The padded paws of the wolverine allow them to stay on top of the snow while the heavy hooved deer sink, making it easy for the wolverine to lock their jaws on a throat. The wolverine also preys on smaller animals and will eat insects and berries.  They live in remote wilderness areas, preferring high elevations with deep snow and plenty of tree or shrub cover.   Wolverines benefit from the presence of other large predators because they are just as much scavenger as predator.  During summer and fall wolverines are too clumsy to actively chase deer but will drive off much larger predators from their kills.  After they consume as much as they can eat, they spray musk on the remains, and it become unpalatable for other carnivores.  Wolverines store caches of dead meat during winter and are ideally suited to survive in cold unproductive natural communities.

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Historical range of the wolverine.  Camera traps suggest they have recently recolonized northern California. They also live in Eurasia.  During Ice Ages, wolverines probably ranged along the southern Appalachians perhaps as far south as north Georgia and Alabama.

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Male wolverines reach weights of 60 lbs but can drive away bears, cougars, and wolf packs. Wolverine cubs sometimes fall victim to the latter 2.

Wolverines occupy very large territories.  Males in Montana patrol 162 square miles on average, while male Yellowstone wolverines average a territory of an astounding 307 square miles.  Wolverines  live in low densities in boreal forests, and this makes their remains rare in the fossil record.  Nevertheless, subfossil remains of wolverines, dating to the Pleistocene, have been excavated from Maryland, Pennsylvania, Wyoming, Colorado, Nevada, Romania, Italy, Germany, France, and the United Kingdom.  (The wolverine is an Holarctic animal, living on both sides of the Arctic Circle.)  The specimen from Cumberland, Cave, Maryland is the southernmost known record of the wolverine in eastern North America and this is south of their known historical range during colonial times.  I hypothesize wolverines ranged into the southern Appalachians as far south as north Alabama and north Georgia during Ice Ages.  The key is deep snow–any climatic phase when deep snow regularly occurred at high elevations in the southern Appalachians would have been an invitation for wolverine range expansion south.  Other boreal species of mammals are found in the fossil record this far south including caribou, fisher, pine marten, porcupine, bog lemming, and red-backed vole.  Wolverine skeletal evidence is probably absent because they lived in low population densities at high elevations in forested environments where fossil preservation is rare.  Historical wolverine range is closely correlated with regions where snow stays on the ground through a good portion of spring.  Undoubtedly, spring snow cover existed in the southern Appalachians during the coldest stages of Ice Ages.

Most of the wolverine’s present day range was covered by glacial ice during Ice Ages, so it seems likely their range shifted south, like that of so many other species then.  How far south did this range shift?  We can only speculate.  But this is an animal that requires deep wilderness, and North America was nothing but deep wilderness before man.  Wolverines won’t cross clear-cuts or burned over land.  The main factor restricting wolverine range before man were the extensive grasslands that likely formed an ecological barrier to their expansion below the southern Appalachians.

References:

Hornocker, M; and H. Hash

“Ecology of the Wolverine in Northwestern Montana”

Canadian Journal of Zoology 59 (7) 1981

Inman, R.

“Wolverine Ecology and Conservation in the Western U.S.”

Swedish University Doctoral Thesis 2013

http://www.paleobiologydatabase.com

 

 

Pleistocene Saiga Antelopes

August 31, 2017

The saiga antelope (Saiga tatarica) ranged from western Europe to Alaska and the Yukon during some climate phases of the late Pleistocene.  This range closely corresponds with an environment known as the mammoth steppe.  This paleoenvironment was similar to the present day central Asian steppe but was more productive, hosting a greater variety of plants and microhabitats that included scrub, woodland, and wetland embedded in a sea of grass.  Summers were cool, winters were long, wind was constant, and precipitation was infrequent.  The bulbous nose of the saiga antelope is an adaptation for living in this kind of environment.  It helps warm frigid air and filter the dust in a dry windy climate.  The range of the saiga antelope has been greatly reduced since the late Pleistocene due to changes in the environment and overhunting by man.  Nevertheless, saiga antelope occurred in eastern Europe as late as the 17th century, indicating they are not a relict species confined to steppe grasslands.  A recent scientific study examining the bone chemistry of subfossil and extant saiga antelope specimens concluded this species can survive on a greater variety of plant foods than present day populations consume.

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Saiga antelopes are critically endangered today but lived from the British Isles to the Yukon, Canada during the late Pleistocene.

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Present day saiga antelope range.  During the Pleistocene they occurred from western Europe to Alaska.

This study found the diet of the saiga antelope overlapped with that of the caribou (Rangifer sp.) in southwestern Europe between 20,000 years BP-15,000 years BP.  It seems likely both species were subsisting upon lichen during winters when other plant foods were scarce.  Pleistocene saiga antelope apparently had a greater flexibility in their diet than present day populations.  The authors of this study suggest saiga antelope could potentially be introduced outside their present day range.  Poaching and disease outbreaks are endangering the surviving remnants of saiga antelope populations, so it could prove beneficial to establish new populations outside their present day range.  However, it’s possible some Pleistocene populations of saiga antelope may have been a distinct now extinct species with different dietary tolerances.  Some Russian paleontologist noted some morphological differences in saiga antelope specimens found outside their present day range, and they proposed a new species–Saiga borealis. Other paleontologists don’t accept this designation.  So far, no genetic studies have solved this difference of opinion.

The saiga antelope is considered a distant sister clade to the springbok-gerenuk clade.  They are the sole survivors of antelopes that roamed Europe before Ice Ages began to occur.  None of their closest relatives were able to evolve fast enough to survive deteriorating climatic conditions.

Reference:

Jurgensen, J.; at. al.

“Diet and Habitat of the Saiga Antelope during the Late Quaternary Using Stable Carbon and Nitrogene Isotope Ratios”

Quaternary Science Review March 2017

Extant South American Canids are Ancient Relics

August 16, 2017

Several species of medium-sized canids native to South America descend from species that formerly occupied North America.  The extant bush dog (Speothos vunaticus), maned wolf (Chrisocyon brachyuras), and the recently extinct Falkland Islands wolf (Dusicyon australis) are (or were) similar to primitive dogs that occurred across North America during the late Miocene and Pliocene.  The emergence of the Canis genus (wolves and coyotes) early during the Pleistocene competitively excluded these primitive dogs from North America, but their ancestors pushed through the jungles of Central America, and they colonized South America where they still thrive today when not persecuted by man. The tropical rain forests of Central America served as a geographical barrier that prevented Canis species from following their primitive relatives.  Though Canis species may be more adaptable overall, their primitive relatives were better able to withstand tropical conditions, a factor that saved them from extinction.

The South American bush dog is a widespread but uncommon pack-hunter that preys on large rodents, peccaries, and rheas.  One genetic study suggests they are most closely related to maned wolves, but another more recent genetic study determined they are most closely related to African hunting dogs.  A species similar to the African hunting dog lived in North America as late as the mid-Pleistocene, so the bush dog may very well be an offshoot of this canid line.  The maned wolf is a solitary species, not a pack-hunter–additional evidence supporting a closer evolutionary link between bush dogs and pack-hunting African dogs, rather than the maned wolf.  The bush dog was known from fossil evidence found in a Brazilian cave before it was recognized as an extant species.

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South American bush dogs.  They are descended from primitive dogs that roamed North America before the Canis genus dominated that continent.

The Falkland Islands wolf was the only mammal species native to the Falkland Islands.  It was a completely naïve species, unafraid of man, and was hunted to extinction by the late 19th century.  Settlers coveted its furry coat and were afraid it would kill their sheep.  Actually, the diet of this species is unknown, but it probably subsisted on penguins, geese, and sea shore scavenging.  How this species colonized the Falkland Islands, located 285 miles from the mainland of South America, was a mystery until recently.  Geologists discovered underwater ridges connected to the mainland that were above sea level during Ice Ages.  A narrow 20 mile straight between the ridges and the Falkland Islands froze into solid ice during winters of the Last Glacial Maximum (~16,000 years ago), allowing the canids to cross.  They may have been hunting penguins on the ice, leading them to the islands.  No other mammal found motivation to cross the ice bridge.

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Extinct Falkland Islands Wolf.  Unfortunately, they had no fear of people.

Genetic evidence suggests the Falkland Island and maned wolves are most closely related to false foxes (Lycalopex sp.), 6 species of which are found in South America today.  However, the Tibetan fox is the maned wolf’s closest living relative.  The Tibetan fox is likely related to the ancestors of all false foxes.  An extinct species of maned wolf (C. nearctus) lived in North America during the Pliocene.  Fossil evidence of this species has been found at sites in Arizona, California, and northern Mexico.  The maned wolf has long legs that help it look over tall grass for rodents–its main prey item.  Genetic evidence shows maned wolf populations increased during Ice Ages when grasslands expanded and contracted during interglacials.  Pliocene environments were often dry and included an expansion of prairie habitat, so it’s likely the North American maned wolf also had long legs.  The fossil evidence of C. nearctus is limited to lower jaws and teeth, so it’s not known how long its legs were.  Maned wolves are omnivorous, and they are important dispersers of seeds.  They often defecate on leafcutter ant nests, and the ants move the viable seeds, helping them germinate.

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Maned wolf.  Maned wolves lived in North America during the Pliocene.

The maned wolf grows to about 50 pounds, but a larger genus of primitive dogs lived in North America until the early Pleistocene.  Theriodictis hunted megafauna in Florida.  Species from the Canis genus outcompeted them in North America, but they continued to thrive in South America until the late Pleistocene extinctions of the megafauna.

Reference:

Nyakatura, K.; et. al.

“Updating the Evolutionary History of Carnivora (Mammalia): A New Species Level Super Tree Complete with Divergence Time Estimates”

BMC Biology 10 (12) 2017

Tedford, Richard; X. Wang, B. Taylor

“Phylogenetic Systematics of the North America Fossil Caninae”

Bulletin of the American Museum of Natural History 2009