Archive for the ‘Pleistocene Mammals’ Category

2 New Studies of Pleistocene Lions

January 6, 2019

There were 3 species of lions living on earth during the late Pleistocene.  The African lion (Panthera leo) is the only species still extant.  The cave lion (P. spelaea) ranged across Eurasia from Britain to Beringia which included Alaska and Yukon above the Canadian Ice Sheet.  The giant American lion (P. atrox) lived in North America south of the Ice Sheet from California to Florida.  Some taxonomists formerly thought the 3 lions were the same species, but recent analysis of anatomy and genetics determined they were 3 distinct species.

2 new studies of Pleistocene lions were published last year.  The first study described an unusually large lion skull found in Natodermi, Kenya.  This specimen is estimated to be 196,000 years old. On average cave lions and giant American lions were larger than African lions.  P. atrox was the largest species of lion, averaging 25% larger than African lions, and 1 specimen is estimated to have weighed over 1000 pounds.  (See https://markgelbart.wordpress.com/2017/01/31/panthera-atrox-the-1007-pound-giant-lion/ )   However, the specimen described in this new paper (catalogued as #KNM-ND59673) belonged to an individual that may have been larger than any cave lion specimen ever described and even larger than all but 2 known American lion specimens.  The size comparison estimates in this paper were based on dental dimensions.  The authors of this paper believe this individual was part of an extinct population that grew to a larger size because they hunted an extinct species of large buffalo (Syncerus antiquus).  They think it was a subspecies of African lion related to the ancestors of the 2 regional haplotypes of lion that still occur today.  Genetic evidence suggests northern lions diverged from an ancestral population of lions 147,000 years ago, while southern lions diverged 189,000 years ago.  This specimen was found on the border between the 2 modern haplotypes.  Although they don’t think it was a distinct species, they can’t completely rule it out–there just isn’t enough evidence.  It seems likely some Pleistocene African lions were just as large as the other 2 species.  Lions originally evolved in Africa but fossil evidence from that continent is more rare than in Eurasia and North America.

 

196,000 year old African lion skull.

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Pleistocene lions may have grown larger in Africa to help them bring down this large extinct species of buffalo.

The 2nd study described 4 specimens of cave lion found in Medvedia Cave located in the Zapadne Tatry Mountains.  These mountains border northern Slovakia and southern Poland. Referring to this species as the “cave” lion is misleading.  Most individuals never went inside a cave during their entire life.  A cave environment is just 1 of the rare places where their remains could be preserved.  Medvedia Cave is the highest altitude that a lion fossil has ever been found.  The authors of this paper think lions searched through caves for hibernating bears, and groggy bears may have been an important part of high altitude lions’ diets because other substantial prey was scarce here.  Some scientists think cave lions were solitary hunters or perhaps hunted in pairs, unlike social African lions that live in large prides.  I disagree with this notion.  Adult male lions grow too large and bulky to hunt prey effectively, and they depend upon females to bring them food.

Lions were more widespread during the Pleistocene because human populations were sparse.  Humans have outcompeted lions since then.  If not for the rise of humans, lions would still be just as widespread as they used to be.

Reference:

Manth, F. ; et. al.

“Gigantic Lion, Panthera leo, from the Pleistocene of Natodermi, eastern Africa”

Journal of Paleontology 92 (2) Novemeber 2018

Sabol, Martin; Juraj Gullar and Jan Harrat

“Montane Record of the Late Pleistocene Panthera spelaea (Goldfuss 1810) from Zapadne Tatry Mountains (northern Slovakia)”

Journal of Vertebrate Paleontology  38 (3) 2018

See also: https://markgelbart.wordpress.com/2016/01/07/uf9076-a-complete-skull-and-jaws-of-a-giant-lion-panthera-atrox-found-in-the-ichetucknee-river-florida/

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There was No Such Species as the Fugitive Deer (Sangamona fugitiva)

December 16, 2018

During 1920 Oliver Hay, a noted paleontologist of that era, named a new species based on a tooth discovered in a Tennessee Cave 35 years earlier.  He believed it was from an extinct species of deer, and he gave it the scientific name of Sangamona fugitive because he thought it may have been common during the Sangamonian Interglacial, though most specimens of this proposed species came from deposits dating to the Wisconsinian Ice Age.  For the next 60 years scientists assigned additional specimens found at fossil sites located in Tennessee, Illinois, Maryland, and Iowa to this species.  The fugitive deer was thought to be a species intermediate in size between a white-tail deer and an elk.  However, during the early 1980s a paleontologist by the name of George Churcher looked at all the specimens assigned to this species and determined they were actually the bones of white-tail deer, elk, or caribou.  Some were from large white-tails and others were from small elk, explaining why they seemed to fall between the range of the 2 species.  Churcher declared Sangamona fugitive an invalid species.  No such animal ever existed.  Taxonomists refer to this as a nomen nudem or naked name because it was assigned to a non-existent animal.

I was unaware of Churcher’s study when I wrote about the fugitive deer in my book and in a few of my earliest blog entries.  His paper is buried in the middle of an obscure special bulletin of the Carnegie Museum.  I did come across this paper a few years ago, but I never felt motivated to write about it until now.  I’m in the middle of researching future topics for my blog and ran into a delay with a couple I had planned, so I finally decided to note this old mistake that originated from a long dead paleontologist.

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Most bones mistakenly assigned to the fugitive deer actually belonged to white-tail deer or elk.

The fossil record suggests there were just 4 species of deer living in southeastern North America during the late Pleistocene.  White-tail deer lived throughout the entire region.  Caribou and the extinct stag-moose (Cervalces scotti) periodically colonized the upper south during cooler climatic stages of the Ice Age.  Elk probably didn’t enter the upper south until 15,000 years ago.  Mule deer may or may not have occurred in western Arkansas.  A single specimen of the South American marsh deer found in Florida was probably a misidentified white-tail deer bone.  (See: https://markgelbart.wordpress.com/2013/02/28/sabertooth-cave-in-citrus-county-florida/ )

Reference:

Churcher, George

“Sangamona: the Furtive Deer”

Bulletin of the Carnegie Museum: Contributions in Memorial to John Guilday 1984

ABC Bears

November 5, 2018

During the Ice Age the coast of southeast Alaska was studded with ice floes and perfect habitat for seals and polar bears.  The interior of Alaska was mostly grassy steppe, the preferred habitat of brown bears.  About 16,700 years ago the icy habitat along the southeast coast of Alaska began to melt and polar bear populations became stranded on Admiralty, Baranet, and Chichagof Islands; also known as the ABC islands.  Here, the habitat began to become more favorable for grizzly bears, and young males looking for new territory not already occupied by adult males colonized the islands.  A genetic study of 1 specimen from this island group determined these colonizing male brown bears mated with female polar bears, creating an hybrid population  (Ursus arctos x U. maritimus).  Gradually, the population of brown bears swamped the DNA of this region, so today polar bear DNA makes up just 6% of their X  chromosome (the female chromosome is XX; the male is normally XY).  Polar bear DNA has also been found in specimens of the extinct Irish brown bear.  DNA evidence suggests polar bears diverged from brown bears about 4 million years ago, but there has been periodic hybridization in regions where the 2 species overlap.

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Location of the ABC islands.

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Top 2 photos are polar bear/brown bear hybrids in captivity.  Bottom right is a polar bear; bottom left a brown bear.  The 2 species rarely do hybridize in the wild.

A few months ago, Discovery Channel aired a program about the ABC bears that I lambasted in this blog article https://markgelbart.wordpress.com/2018/06/04/the-fear-island-special-that-aired-on-animal-planet-last-night-was-full-of-shit/ .  Previously, Discovery Channel has aired programs about Bigfoot, mermaids, and the extant existence of a 60 foot long extinct species of shark.  I assumed this program was completely bad pseudo-science, but 1 of my readers alerted me to the scientific merits of this program and also informed me that I wrongly assumed the ABC islands were the same as the Kodiak islands.  The Kodiak islands are on the other side of the Gulf of Alaska, so I errored geographically by hundreds of miles.  And the expedition on this program did have scientific merit because they were seeking just the 2nd DNA sample from an ABC bear.  However, I still think this program was full of shit…just not as full of shit as I initially assumed.  Here is why I stand by my first opinion:

1. The participants acted as if they were the first researchers to ever obtain DNA evidence from a bear on the island, though a study of 1 specimen had already been published.  They already had a good idea what they were going to find, and it was not a great mystery as they promoted.

2. The Indian guide claimed he saw 6 bears ceremonially bury another dead bear.  What unscientific bull crap.

3. I don’t buy the size estimate claim.  It was based on an up close trail cam photo.  Weigh it or just shut up.

Reference:

Cahill, J; et. al.

“Genetic Evidence for Island Populations Conversion Resolves Conflicting Theories of Polar Bear Evolution”

PLOS Genetics 2013

 

Pleistocene Pine Voles (Pitymys pinetorum)

October 16, 2018

Evolutionary biologists like to study rodent fossils.  Rodents occur in high population numbers, and their rapid generational turnover means evolutionary change occurs faster than with larger slower breeding animals.  Scientists recently studied pine vole teeth from 2 caves in Kentucky and 1 cave in Georgia that date to the last Ice Age and compared them with modern day pine vole teeth.  Pine vole teeth from Hilltop and Cutoff Caves in Kentucky date to about 30,000 years ago, and the pine vole teeth from Yarbrough Cave in Georgia date to about 23,000 years ago.  Pine voles are still a common species, occurring all across eastern North America.  Despite their name, they prefer living in moist deciduous forests where they tunnel under tree roots and feed on roots, seeds, fruit, fungus, and insects.  Their fossorial existence keeps them safe from owls and hawks, though snakes can enter their burrows.  Pine voles are considered arvicolid rodents because their teeth cusps are in the shape of alternating triangles.  Other common arvicolid rodents include meadow voles, lemmings, muskrats, and cotton rats.

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Pine voles weigh just an ounce.  They mostly live underground but occasionally venture to the surface.

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Pine vole range.  Pine vole is a misnomer.  They prefer moist deciduous woods, not pine forests.  Nobody knows why the common name is pine vole.

The pine vole teeth from the Kentucky Caves show the pine voles living then were the same size as modern day pine voles living in the region.  However, pine voles living in north Georgia during the Ice Age were larger than modern day Georgia pine voles and about the same size as northern pine voles.  Scientists believe this was in response to colder temperatures.  Bergmann’s rule states that animals living in colder climates generally grow to a larger size because they are better able to retain body heat.  The authors of this study can’t determine whether this large size was the result of inbreeding with northern populations of larger pine voles that colonized the region or natural selection of the local population.

Reference:

Martin, Robert; and K. O’Bryan

“Size and Shape Variation in the Late Pleistocene Pine Vole (Mammalia: Arvicolidae: Pitymys Pinetorum) First Lower Molars from 3 Caves in Kentucky and Georgia”

Paludicola September 2014

A New Study of the Looper Collection

October 9, 2018

Between 1989-1995 Lonnie and Freida Looper hunted for fossils on 19 different gravel bars along the Mississippi River during droughts when the bars became exposed.  These gravel bars are located between Helena, Arkansas and Greenville, Mississippi.  Thousands of years ago, the bones were quickly buried when glacial meltwater pulses flooded the Mississippi River Valley.  The Mississippi River erodes this Pleistocene-aged sediment and deposits the soil and bones on the gravel bars.  For years the Looper family sold replicas of their specimens, but they donated most of the actual specimens to Delta State University.  I don’t think they still sell the replicas, though the Looper’s website remains on the internet.  The Looper family discovered over 550 specimens including 27 species.  A comprehensive study of their collection wasn’t published until 2017.

 

 

 

 

 

 

The Looper family found this Jefferson’s ground sloth claw on a Mississippi River gravel bar exposed during a drought.

During most of the late Pleistocene the Mississippi River entered the Mississippi River Valley through 3 gaps, but all of these flooded following the collapse of the ice dam that unleashed the waters of Lake Agassiz about 12,900 years ago.  Before this the Mississippi River didn’t meander broadly like it does today.  Instead, it was a series of braided channels clogged with sandbars because the water table was much lower then.  Cold glacial meltwater pulses caused cool microclimates within the valley that favored mixed Ice Age woodlands of pine, spruce, ash, aspen, oak, hickory, willow, tamarack, herbs, and grass.  Frequently flooded bottomlands and abandoned dried-out channels hosted alder thickets with beech, walnut, tulip, willow, and grass.  Spruce and jack pine dominated drier upland sites.  These were the types of habitats that supported the animal life represented in the Looper collection.  Some of the species they found were not known to have occurred within the Mississippi River Valley including paleolama, stag-moose, helmeted musk-ox, giant short-faced bear, and manatee.

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Map of the Mississippi River Valley in relation to the ice sheet during the Last Glacial Maximum. This map doesn’t represent the land area that occupied the continental shelf then.

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The Mississippi River resembled this modern day braided river during the Ice Age.

Paleolama mirifica was a species known from the coastal plains of South Carolina and Georgia, and throughout Florida; so the specimen found by the Looper family was a first for the region and evidence for a greater range than was previously known. The manatee was likely an accidental migrant that may have perished because it failed to go south during cool weather.  Manatees can’t survive in water temperatures below 68 degrees F.  The Looper family also collected bones of mammoth, mastodon, bison, white-tailed deer, long-nosed peccary, 2 species of extinct tapir, horse, beaver, giant beaver, Jefferson’s ground sloth, dire wolf, raccoon, black bear, giant tortoise, snapping turtle, soft-shelled turtle, unidentified bird, small-mouth buffalo fish, and flat-headed catfish.  Bones of bison and deer were the most common.

Nina Baghai-Riding, the lead author of this new study, thinks the Mississippi River Valley may have been a migratory corridor for some species.  Cool microclimates along the river may have attracted fauna of northern affinities.  Rivers are also rich in food resources as well because a greater quantity and quality of vegetation can grow in more irrigated environments.  The superior feeding opportunity attracted megafauna as well.

Reference:

Baghai-Riding, Nina; and D. Hunley, C. Beck, and E. Blackwell

“Late Pleistocene Megafauna from Mississippi Alluvium Plain Gravel Bars”

Paludicola December 2017

file:///C:/Users/Owner/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/Downloads/Baghai-RidingLatePleistocenegravelbarpaper%20(3).pdf

 

How far South did the Extinct Stag-Moose (Cervalces scotti) Range During the Late Pleistocene?

October 2, 2018

A species of extinct deer, slightly larger than a modern day moose (Alces alces), occurred south of the ice sheets during the late Pleistocene.  It is alternatively known as stag-moose or elk-moose, but its scientific name is Cervalces scotti. This giant deer had the long nose of a moose, though its antlers were more like those of an elk.  However, it shared a closer common ancestor with the former.  They inhabited wetlands surrounded by mixed forests dominated by spruce but with significant elements of pine and hardwoods.  Like modern day moose, they fed upon aquatic plants during summer and twigs during winter.  Mastodons occupied a similar habitat and fed on the same foods, so the 2 species often co-occurred together.

Evidence from the fossil record suggests stag-moose were particularly abundant in midwestern bogs left by retreating glaciers.  Stag-moose bones are quite commonly found in Ohio, Indiana, Illinois, and New York.  Surprisingly, they occurred even farther south with isolated fossil remains having been discovered in Virginia, Arkansas, Mississippi, and South Carolina.  The stag-moose remains found in Desha and Philips County, Arkansas and Rosedale, Mississippi are at 34 degrees latitude.  These consist of antler fragments and a jawbone with a tooth.  The stag-moose specimen from Charleston, South Carolina (just a tooth) occurred at 32 degrees latitude.  This is probably close to the southern limits of its former range because stag-moose remains are completely absent from sites in fossil rich Florida.

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Artist’s depiction of the stag-moose.  They were huge. That is a lot of venison.

A stag-moose skeleton found in Chippewa Lake, Medina, Ohio had 1 bone that had attached sediment filled with pollen representing the type of environment it lived in.  The pollen included fir, maple, alder, aspen, birch, hickory, hackberry, hazelnut, ironwood, pine, oak, basswood, elm, spruce, cedar, ragweed, grass, and cattail.  Spruce pollen made up 60% of the total.  It seems likely the type of environment favored by the stag-moose, as far south as Charleston, South Carolina, included various compositional ratios of these species.  I hypothesize stag-moose occurred in the mid-south during cool moist interstadials rather than the coldest driest stages of Ice Ages.  Wetlands would’ve been more common during these climatic phases.  Full blown glacial maximums restricted stag-moose habitat because desert scrub and grassland habitat expanded then.

Although there is no supporting archaeological evidence, I think overhunting by humans caused the extinction of the stag-moose.  Man colonized North America when ice sheets covered most of Canada, thus restricting stag-moose to more temperate regions where humans became common enough to impact their populations.  When the glaciers began to recede, optimal stag-moose habitat increased, but humans had already decimated their populations into extinction.  Modern day moose crossed the Bering land bridge, and ecologically replaced the stag-moose and were able to survive in northern latitudes where human populations remained too scarce to overhunt them.

Reference:

Mcdonald, Greg; R. Glotchober

“Partial Skeleton of an Elk-Moose, Cervalces scotti, from Chippewa Lake, Medina County Ohio”

Research Paper 2017

Were Beringian Wolves Blonde?

September 25, 2018

An extinct ecomorph of the gray wolf (Canis lupus) roamed North America from Beringia to at least as far south as Wyoming during the Late Pleistocene. (See: https://markgelbart.wordpress.com/2016/05/30/beringian-wolves-an-extinct-ecomorph-of-canis-lupus-lived-as-far-south-as-wyoming/ ) Beringia included the unglaciated region of Alaska, the Yukon, and the Bering Strait located north of the Ice Sheet that covered most of Canada then.  The Bering Strait emerged above sea level during Ice Ages.  An ecomorph is the regional variation of a species that differs morphologically from other populations of the same species.  Beringian wolves had bodies closely resembling those of gray wolves, but their teeth and jaws were larger and more robust like those of the extinct dire wolf (C. dirus).  Paleontologists interpret the larger teeth and jaws as an adaptation for preying and scavenging on megafauna.  Isotopic evidence of Beringian wolf bones does suggest they fed upon mammoths, horse, bison, musk-ox, and caribou.  Beringian wolves were not ancestral to modern day Alaskan gray wolves, but they do share a common ancestor.  Genetic evidence suggests Beringian wolves diverged from wolves found in northern China and Mongolia today about 28,000 years ago.  Present day Alaskan wolves descend from a different population of wolves than the Beringian wolves which became extinct about 7500 years ago.

Map showing location of sites where Beringian wolf bones have been discovered and the proposed route from Beringia to Wyoming.  I hypothesize they occurred as far south as the southern Appalachians.

I hypothesize Beringian wolves were an hybrid species originated when gray wolves interbred with dire wolves.  This hypothesis will be possible to test when scientists are able to extract DNA from a dire wolf fossil.  There are thousands of dire wolf specimens from the La Brae Tar Pits, but the tar in the bones prevents DNA extraction.  Many specimens of dire wolf have been found in Florida as well, but humid conditions here cause DNA to deteriorate.  I also hypothesize Beringian wolves were more widespread than the fossil record indicates.  Over much of the continent fossil evidence of canids consists of isolated teeth and bones difficult for scientists to differentiate between gray wolf, Beringian wolf, dire wolf, and even large Pleistocene coyote.  For example 1 wolf tooth found at Ladds Cave in north Georgia was identified as belonging to a gray wolf by 1 paleontologist, but another scientist ruled it fell within the size range of a dire wolf.  Maybe this specimen came from a Beringian wolf.

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80,000 year old mummified wolf pup found in a Yukon gold mine.  Note the coat color.  It’s is a brownish blonde.

During June of 2016 gold miners discovered the mummified remains of a wolf pup.  As the photo shows, it was perfectly preserved.  Carbon dating of the specimen indicated it was older than 50,000 years–the upper limit of carbon dating.  However, the specimen was associated with volcanic ash dated to about 80,000 years BP.  This predates the 28,000 year old divergence between Mongolian wolves and Beringian wolves, so it will be interesting to learn how this specimen relates to later populations of wolves.  Julie Meachen of Des Moines University will lead a study of the pup.

The coat color of this specimen surprises me.  Of all the speculative illustrations of Pleistocene wolves none depict a golden, blonde, or tawny colored coat.  This specimen appears to have a coat color similar to a lion but a little darker.  Perhaps preservation in permafrost for so long changed the original color of the coat but suppose this was the color.  The coat color likely resembled the landscape background of its habitat.  Patches of yellow grass interspersed with bare dirt predominated in Beringia and much of North America during Ice Age stadials when precipitation was scarce and temperatures dropped.  It’s possible packs of yellow dire wolf/gray wolf hybrids lived throughout parts of North America for thousands of years.

Were Southeastern Wolves Feral Indian Dogs?

August 2, 2018

Archaeologists uncovered 10,000 year old dog (Canis familiaris) skeletons at 2 sites in Illinois.  The sites are known as Koster and Stillwell.  This is the earliest known evidence of domesticated dogs in North America, though scientists believe dogs traveled over the Bering Land Bridge with humans as long as 15,000 years ago about the same time they were first tamed.  Late Pleistocene evidence of dogs in America has either faded away or has yet to be found, but they were probably here.  The specimens from Illinois date to the Pleistocene/Holocene boundary.  The Stillwell dog was about the size of an English setter, and these early Indian dogs anatomically resemble coyote/dog hybrids (known as coydogs).  I hypothesize the wolves that lived in southeastern North America until about 1917 may have been Indian dogs that simply reverted to a wild state.

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Audubon’s painting of an Indian dog.  Indian dogs were so wolfish that European colonists often mistook them for wolves.

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Illustration of black wolf pack by Kelly Quinn.

Scientists classified the wolves that lived in southeastern North America until Europeans wiped them out as the red wolf (Canis rufus), but nobody really knows what they were.  A DNA test of a few specimens from Arkansas found they were hybrids of coyote (Canis latrans) x timber wolf (C. lupus), and wolves currently living in eastern Canada also appear to be coyote/timber wolf hybrids.  However, this still doesn’t explain what the now extinct wolves that lived in Georgia, South Carolina, and Florida were.  The so-called red wolf is not well represented in the fossil record, and the few specimens identified as red wolves may actually be coyotes.  They don’t appear in the fossil record until after dire wolves became extinct, and I think dogs brought by humans went wild and occupied the vacant niche created when dire wolves became extinct.  Although southeastern wolves varied in coat color, many were melanistic.  The gene for a black coat color in wolves originated in domesticated dogs and that was passed to the wolf population in the rare instances when wolves mated with dogs.  So I believe the wolves that lived in southeastern North America were feral Indian dogs with perhaps some admixture of timber wolf and/or coyote.  They were a primitive dog that like the dingo and Carolina dog readily reverted to the wild, especially those left behind when Indian tribes moved away from an area or died out.  Audubon almost mistakenly shot some Indian dogs because he reported that they looked just like wolves.  This resemblance may have contributed to their extinction, though diseases brought by the European colonists’ dogs were probably a bigger factor.  Europeans often mistook Indian dogs for wolves and killed them or deliberately exterminated them to prevent them from breeding with their well bred dogs..  A DNA study of the Koster specimen determined modern dogs have none of the earlier Indian dog ancestry, suggesting the ancient Indian dogs are extinct.

The Carolina dog descends from a later lineage of dogs brought by Eskimos about 1000 years ago.  Strange as it may seem, these dogs quickly evolved from long-furred Eskimo dogs well adapted to cold climates to the short-haired “Old Yeller” type dogs at home in the hot humid south.  Like the earlier Indian dogs, Carolina dogs also easily revert to a wild state.

The original Indian dogs may be extinct, but they did leave a modern day legacy. The only genetic imprint they left in modern dogs is a sexually transmitted cancer.  Geneticists found this cancer originated in the ancient Indian dogs and was passed on to modern dog breeds.

Reference:

https://www.sciencenews.org/article/dogs-lived-and-died-humans-10000-years-ago-americas

The Adaptability of Pleistocene Peccaries

June 30, 2018

Two lineages of peccaries lived all across North America for over 5 million years but both became extinct about the time man appears in the archaeological record.  The long-nosed peccaries in the Mylohyus genus were forest edge species, and the flat-headed peccaries in the Protherohyus-Platygonnus genuses inhabited scrubby thickets.  A new study looked at dental microwear and bone chemistry in these lineages and compared them with the teeth and bone chemistry of the extant white-lipped peccary to determine the dietary similarities and differences of the extinct and extant species of peccary.  Peccaries in the Mylohyus genus co-existed with Protherohyus peccaries during the Miocene over 5 million years ago.  The former ate more woody browse and forest vegetation, while the latter mostly ate grass.  During the Pliocene between 5 million years BP-2million years BP both Mylohyus and Platygonnus ate mostly woody browse in Florida.  Their diets shifted during the early-mid Pleistocene with an increased consumption of grass.  During the late Pleistocene Mylohyus ate more forest vegetation such as twigs, acorns, and nuts, while Platygonnus ate more tough leaves and grass.  This study shows how adaptable these lineages were to environmental change–their diets shifted with changes in climate.  It seems obvious to me that overhunting and/or disruption of the overall ecosystem by humans, not whole scale environmental change, caused the extinctions of both Mylohyus and Platygonnus.  Surviving extant species of peccaries live in deserts and remote jungles where human populations remain sparse.

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Illustration of Platygonnus peccary.

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White-lipped peccaries eat forest vegetation.  They can be dangerous.

The proliferation of feral pigs (Sus scrofa) in North America today demonstrates how favorable the environment still would be for Pleistocene peccaries, if they still existed.  Pigs co-evolved with humans in Eurasia to produce large litters, making them capable of surviving human hunting pressure.  Pigs produce litters of 8-12, but peccaries only birth 2-4 young.

Some archaeologists reject the likelihood that humans hunted peccaries to extinction because there are no known kill sites, other than a peccary shoulder blade with a spear hole in it next to a spear.  See: https://markgelbart.wordpress.com/2014/03/10/the-sheridan-cave-pit-fossil-site-in-wyandot-county-ohio/

This is a ridiculous assumption. There are also no known white-tailed deer kill sites in the archaeological record, but we know Indians hunted deer.  Evidence humans killed Pleistocene peccaries simply faded away over time.

Reference:

Bradham, J. et. al.

“Dietary Variability of Extinct Tayassuids and Modern White-Lipped Peccaries (Tayassu pecari) as Informed from Dental Microwear and Stable Isotope Analysis”

Palaeogeography, Palaeoclimatology, Palaeoecology April 2018

 

An Anatomical Comparison Between the Extinct North American Cheetahs (Miracynonyx sp.) and the Late Pleistocene/Holocene Cougar (Puma concolor)

May 28, 2018

One of my readers recently asked whether the cougar (Puma concolor) might be the same species as the extinct North American cheetahs (Miracynonyx inexpectatus and M. trumani).  This is not as ridiculous a question as a layman might think because paleontologists often mistakenly identify multiple species from fossil remains that after re-evaluation are eventually determined to be from 1 species.  I love reading articles about vertebrate paleontology, but I usually skip over anatomical descriptions because they are pretty dry.  But to answer his question, I used google to search for a paper comparing the anatomical differences between Puma and Miracynonyx.  I did not find a journal article with a comprehensive anatomical comparison between the 2, but I did recall a paper I’d already read that discussed some of the differences.  I’ve linked the paper below in  my references.

Cougars and North American cheetahs had different-sized teeth.  Cougars have larger canines and lower molars than North American cheetahs, but they have smaller lower premolars (p4) and smaller upper pre-molars (P3).  They also have a “less reduced protocone on upper premolar P4.”  North American cheetahs had longer limbs than cougars as the below photos from the linked paper show.  So the answer is no.  Cougars were definitely not the same species as the North American cheetahs.

Fossil history of the panther (Puma concolor) and the cheetah-like cat (Miracinonyx inexpectatus) in Florida - Page 208

Comparison of limb bones between cougar and North American cheetah shows the latter had longer hind foot bones and were better runners.

Fossil history of the panther (Puma concolor) and the cheetah-like cat (Miracinonyx inexpectatus) in Florida - Page 210

North American cheetahs had longer front foot bones as well.

Cougars and North Americans cheetahs are closely related, however.  Genetic evidence suggests their shared lineage originated 6-8 million years ago, and a puma-like cat, probably Puma pardoides, crossed the Bering Land Bridge from Asia shortly after this.  In North America the puma-like ancestor diverged into 3 lines: cougars, North American cheetahs, and jaguarundis. The Puma genus diverged from Miracynonyx about 3.2 million years ago.

The fossil evidence shows M. inexpectatus  lived all across North America from the late Pliocene to the middle Pleistocene (~3 million years BP-~300,000 years BP).  In the Florida Museum of Natural History there are 47 records in state of M. inexpectatus at sites thought to date from the Pliocene to the mid-Pleistocene, but they are known from just 1 late Pleistocene site in Florida.  This site is named Lecanto 2A. The only other Late Pleistocene site with a possible M. inexpecatus  fossil (1 leg bone) is in Cavetown, Maryland.  These specimens can’t be radio-carbon dated.  The reason the specimen from Lecanto 2A is considered Late Pleistocene is its association with specimens of other species known from this age including dire wolf, Florida spectacled bear, rice rat, and cotton rat.  It’s possible there were relic populations of M. inexpectatus  still living during the Late Pleistocene, but it seems more likely it’s a case of older fossils getting mixed with younger fossils.

M. inexpectatus  expanded its range at a time coinciding with the expansion of grassland habitat.  Its long legs helped it run down prey.  M. trumani was even more adapted for living in open habitat.  This species appeared during the Late Pleistocene and was restricted to western North America as far as we know from the fossil record.  M. trumani is probably a descendent of M. inexpecatus which had intermediate characteristics between cougars and M. trumani. 

The paleobiology database indicates cougar fossils dating to the Early and Mid Pleistocene in California, Idaho, Washington, and Mexico have been reported.  Nevertheless, cougar fossils predating the Late Pleistocene are rare.  In the Florida Museum of Natural History there are 44 records of cougar from the Late Pleistocene but just 2 from the Mid Pleistocene and 2 from the Early Pleistocene.  The early Pleistocene specimens are referred to as Puma lacrustis, but I searched for this scientific name on google and found nothing, so I’m not sure what these specimens actually were.  Genetic evidence suggests cougars were well established in South America between 300,000 years BP-200,000 years BP, and this corresponds with the widespread fossil evidence of this species throughout North America during this time period.  I hypothesize cougars began to expand their range widely during an early Rancholabrean interglacial from a regional ancestral population undetected in the fossil record.  This time period would correspond to when forested conditions expanded.  Cougars are ambush predators that prefer forests and woodlands.

North American cheetahs are not as closely related to Old World cheetahs as previously thought.  Physical similarities between the 2 are just another example of convergent evolution.

References:

Barnett, Ross; et. al.

“Evolution of the Extinct Sabretooth and the American Cheetah-like Cat”

Current Biology 15 (5) August 2005

Culver, M.; W. Johnson, J. Pecon-Slattery, and S. O’Brien

“Genomic Ancestry of the American Puma (Puma concolor)

Journal of Heredity 91 (3) 2009

Morgan, Gary and Kevin Seymour

“Fossil History of the Panther (Puma concolor)  and the Cheetah-like Cat (Miracynonxy inexpectatus) in Florida”

Bulletin of the Florida Museum of Natural History 1997

http://ufdc.ufl.edu/UF00095787/00001/1j