Pterosaurs may have Cared for their Young

January 11, 2018

Some imagine the Cretaceous and Jurassic Ages as a time when the earth was strange and full of terrifying monsters.    The earth was a vast wilderness then, dangerous perhaps for most creatures, but it was no more strange or terrifying than the world we live in today–the Anthropocene with its genocides, terrorism, potential nuclear war, and extensive environmental destruction caused by a single dominant species.  The dinosaur world hosted species different from those of modern day earth, but these organisms were part of ecosystems recognizably comparable to those of today.  For example fish-eating pterosaurs nested in communal colonies, not unlike present day heron and egret rookeries.  Pterosaurs were not dinosaurs but instead were flying reptiles–the only vertebrates besides birds and bats to evolve the ability to fly. After their initial evolution the early Jurassic pterosaurs radiated into many species and occupied different ecological niches.  From the middle of the Jurassic until their extinction at the end of the Cretaceous 66 million years ago, there were probably about as many species of pterosaurs living in the world as there are birds today.  Evidence from 1 site in northwest China suggests pterosaurs, like so many modern day vertebrates, cared for their young.

Paleontologists found 215 fossilized eggs of a species of pterosaur known as Hamipterus tianshanensis, a fish-eating species that nested communally.  The fossils from this site date to about 120 million years BP, and they are from many generations. The nests were located next to a lake at the time of deposition.  Apparently, pterosaurs used this site annually.  Perhaps it was difficult for predators to access.  Some of the eggs contain visible embryos.  The embryos show well developed legs but underdeveloped wing bones.  This suggests the hatchlings couldn’t fly and depended upon parental care for food until their wings developed.  However this conclusion isn’t certain.  The fossils are of an embryonic stage, not actual hatchlings.  The wing bones may have developed at a later embryonic stage.

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Artist’s representations of pterosaurs have changed over the years.  In this old issue of Green Lantern from the early 1970s the pterosaur is larger than a man, featherless, and conveniently yellow.  Green Lantern’s power ring doesn’t work against yellow objects.  The wingspans of some species of pterosaurs were longer than the length of a man, but they could not have seized and carried a man away.  They were able to leap straight up and fly though, unlike large modern bird species which must take a running start.

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This more modern representation of pterosaurs by Masato Hattori, a depiction of Hamipterus tianshanensis, shows the reptile covered with hair-like feather structures.  It also had teeth.

Cretaceous-aged outcroppings occur near Columbus, Georgia and the Chattahoochee River.  These are the only regions in the state where Cretaceous fossils have been found.  David Schwimmer, a professor at Columbus State, excavated 3 pterosaur wing bones from an outcropping here–the only evidence pterosaurs formerly existed in the state.

References:

Deeming, Charles

“How Pterosaurs Bred”

Science 358 (6367) December 2017

Wang, Xi; et. al.

“Egg Accumulation with 3-D Embryos Provides Insights into the Life History of a Pterosaur”

Science 358 (6367) December 2017

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Pleistocene Wood Ducks (Aix sponsa)

January 4, 2018

Wood ducks differ from most other species of ducks because they nest in hollow trees, rather than in thick wetland vegetation.  Unlike migratory species of ducks that prefer to fly over open water or high in the sky, wood ducks comfortably fly between trees.  However, wood ducks do share a love of water with their kin.   Shortly after wood ducklings hatch, they jump out of their nest and follow their parent to water.  Oftentimes, their den tree is located in flooded terrain and the water guarantees a safe landing.  But the ducklings are so light they can land on solid ground without sustaining injury, though they are not yet able to fly.

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Male wood ducks are much more colorful than females.  I’ve only seen wood ducks on 1 occasion, while I was visiting Phinizy Swamp Park in Augusta, Georgia.

Wood ducks probably first speciated during the early Pliocene when Ice Ages began occurring, and glaciers caused a divergence in the Holarctic ancestral population that also gave rise to their closest living relative, the mandarin duck (Aix galericulata) of east Asia–the only other species of duck in the Aix genus.  Fossil evidence of wood ducks dating to the late Pliocene and Pleistocene has been found at 6 sites in Florida and 1 each in Oregon, New Mexico, and Georgia; suggesting the species has been widespread for millions of years.  (Pleistocene wood duck remains in Georgia were excavated from Kingston Saltpeter Cave, Bartow County.)  Wood ducks were likely most common during interglacials and interstadials when their favored habitat–beaver ponds and woodlands with abundant streams–expanded.  Wood ducks eat acorns, seeds, berries, and insects.  Oaks increased in abundance during wetter climate phases, therefore providing more acorns for wood ducks to eat.

There are eastern and western populations of wood ducks.

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Wood duck range map.

Genetic evidence suggests these populations diverged ~34,000 years ago.  This is consistent with the record of climate change.  The stage 2 stadial that included the Last Glacial Maximum started about 29,000 years ago and before this climate frequently fluctuated between stadial and interstadial. Any 1 of the previous stadials preceding stage 2 or stage 2 itself could have caused the ecological changes isolating the 2 populations.  Dry grassland habitat expanded and streams dried up, so that eastern and western populations were separated into different refugia.  They still haven’t reconnected, even though the 2 populations come so close to each other in the midwest.

Reference:

Peters, J.L.; W. Gretes, and K. Omland

“Late Pleistocene Divergence between Eastern and Western Populations of Wood Ducks (Aix sponsa) inferred by the ‘Isolation with Migration’ Coalescent Method”

Molecular Ecology (11) October 2005

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

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.

 

 

Surprise: Increased Hurricane Activity During the Younger Dryas

November 28, 2017

 

The vast ice sheet that covered Canada during the last Ice Age began to melt rapidly about 15,000 years ago, creating enormous glacial lakes. The largest glacial lake, known as Lake Aggasiz, was bigger than all of the present day Great Lakes combined.  The ice dam impounding this incredible volume of water collapsed 12,900 years ago, and a massive flood of cold freshwater, icebergs, and debris gushed into the North Atlantic via the St. Lawrence River.  This event caused a sudden drop in global temperatures and a reversal back to Ice Age conditions at northern latitudes because the influx of cold fresh water shut down ocean currents that brought tropically-heated salt water north.  The cold climate phase lasted for about 1500 years, and climate scientists refer to it as the Younger Dryas.

The colder ocean of the Younger Dryas should have spawned fewer hurricanes than the warmer oceans of today.  Hurricanes are a product of energy released from warm ocean water.  However, scientists discovered evidence hurricane activity increased off the coast of Florida during the Younger Dryas.  They discovered deposits of turbidite near the Dry Tortugas Islands, dating to the Younger Dryas.  Turbidite is sediment and rock resulting from underwater perturbations.  Earthquakes can cause turbidite formation, but this region is not prone to seismic activity.  Instead, hurricanes produced underwater currents that formed turbidite here.

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Map of the Dry Tortugas–site of the study referenced in this blog entry.

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Image showing how turbidite deposits are formed.

Scientists aren’t sure why hurricane activity increased during the Younger Dryas at this locality.  Some of their climate models suggest the oceans were much colder to the north and west of the Florida coast but only slightly colder than present day ocean temperatures off the modern Florida coast.  Perhaps the tropically-heated water that pooled near the equator spawned hurricanes that reached the Florida and south Atlantic coasts.

Increased hurricane activity contributed to the expansion of longleaf pine savannahs.  The wind felled forests, and the accompanying lightning-sparked fires maintained longleaf pine savannah ecosystems while repressing closed canopy hardwood forests.  Pleistocene megafauna became extinct during the Younger Dryas, even though longleaf pine savannahs are ideal habitat for grazers such as mammoths, bison, horses, giant tortoises, and many other species.

Reference:

Toomey, M. ; et. al.

“Increased Hurricane Frequency Near Florida during Younger Dryas Atlantic Meridional Overturning Circulation Slow Down”

Geology 45 October 2017

 

 

 

 

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 Friesenhahn Cave Fossil Site in Bexar County, Texas

November 14, 2017

Rob Nelson stood next to a wall of fossils on 1 episode of Secrets of the Underground, a Science channel tv series.  He was visiting Friesenhahn Cave in Bexar County, Texas about 20 miles north of San Antonio during the taping of the series he hosts.  The tusk of a mammoth or mastodon, a baby mammoth tooth, and many small fossils were visible; and they were cemented together.  It’s remarkable that such an undisturbed matrix could still exist here because people have been excavating fossils from this site off and on for about 100 years.  Specimens collected by local amateurs were first described from this site in a paper published during 1920.  For awhile the landowner stopped permitting people to collect fossils in the cave, but then in 1949 Mr. Friesenhahn himself invited some professors to excavate fossils in the cave. They found the complete skeletons of scimitar-toothed cats and a long-nosed peccary plus the bones of 30 other species of mammals and the remains of reptiles and amphibians. The discovery of the complete scimitar-toothed cat skeletons was important because before this the species was known from an incomplete skull, a few teeth, and some isolated bones.  Large numbers of juvenile mammoth and mastodon bones were found associated with the scimitar-toothed cat skeletons, and the paleontologists came to the conclusion the big cats used the cave as a den and dragged their prey inside.

A flurry of papers about the cave were published, but access was again restricted until Concordia University purchased the property in 1998.  Apparently, since the purchase, some scientists have been working with the disturbed sediments, but they are waiting for a private or government grant before tackling the remaining undisturbed strata.  I suppose they want to use the most modern techniques when going through this material.  During the original dig 68 years ago, scientists mention fossils that were in such poor condition “they weren’t worth preserving.”  (I was appalled when I read this.)  There are modern methods that can preserve fossils that are in poor condition, but they can be costly.  Scientists have also developed better ways of excavating fossils.  Nevertheless, nothing has been published in the scientific literature about this cave since Concordia University purchased the property.  It has been nearly 20 years, and they still haven’t been able to obtain funding for new excavations, though they do have a corporate grant to study the disturbed sediments.  Still, it seems as if someone currently studying the cave would have at least published a paper by now entitled “Additional fossils recovered from Friesenhahn Cave.”  To be honest, I am not impressed with their academic efforts here.

Brief excerpt of an episode of Secrets of the Underground, featuring Friesenhahn Cave.

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A grate protects the cave from looters and keeps trespassers from falling inside.

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The paleontologist, Grayson Mead, with the complete skeleton of a scimitar-toothed cat discovered in Friesenhahn Cave during 1949.

So far, 13 adult and 5 juvenile scimitar-toothed cat remains have been found in the cave.  It’s unclear which of these were recovered in 1949 and which were discovered more recently.  The cave has also yielded 1 bone of a saber-toothed cat, hundreds of baby mammoth and mastodon teeth, the bone of 1 ground sloth; and the remains of bison, deer, camel, tapir, long-nosed peccary, black bear, dire wolf, and coyote.  The latter was especially abundant.  Smaller animals that inhabited the area during the late Pleistocene, based on the bone accumulation in the cave, were jack rabbit, cottontail, desert cottontail, pocket mouse, and 4 species of mice in the Peromyscus genus.  Some of these species are listed in the paleobiology database, and others are mentioned in the below referenced bulletin or on the Texas University website.  The lists don’t match up.  Someone needs to do a more thorough review of the specimens to determine exactly which species were found by whom and during which excavation.

Evidence suggests a pond periodically existed in the cave, depending upon rain and drought cycles. The basin filled during rainy years but dried out during droughts. No fossil evidence of pond turtles exists here.  Instead paleontologists report remains of 2 terrestrial species–a large extinct subspecies of box turtle and an extinct tortoise (Geochelone wilsonirelated to the extinct giant tortoises that ranged throughout the south during the Pleistocene.  G. wilsoni is known from just a few sites in North America but was first discovered in Frisenhahn Cave.  Pond turtles never found the ephemeral water hole in the cave, but northern leopard and barking frogs did. Diamondback rattlesnakes used the cave as a den as well.

The species composition suggests the region around the cave was an arid grassland with some scrub.  Woodlands existed alongside local rivers.  The mammoth, bison, camel, coyote, and jackrabbit indicate dry grassland environments.  However, the presence of deer, tapir, long-nosed peccary, and black bear suggest some woodlands or forest edge habitat existed nearby.

The cave formed when rainwater dissolved limestone rock underground.  The initial entrance was small, and the oldest levels contain small vertebrates deposited in the form of owl pellets.  Gradually, the entrance enlarged so that larger vertebrates began to use it as a den.  Some of the fossil remains are from animals that died in the cave, but others were brought in by predators.  Periodic flash floods may have added small bones to the collection.  Eventually, the cave entrance collapsed, and the chamber was sealed for thousands of years until recent times when a sinkhole formed on top of the cave, allowing modern day access.  The remains are estimated to be 19,000 years old, but it’s unclear where this estimate originated.  I’m unaware of any carbon-dating of the objects in this cave.  It was originally discovered before carbon-dating was invented.  The site is badly in need of a more modern review, and I’m not sure Concordia University is up to the task.

References:

Evans, Glen; and Grayson Meade

“The Friesenhahn Cave” and “The Saber-toothed Cat, Dinobastis serus

Bulletin of the Texas Memorial Museum  September 1961

Secrets of the Underground  Season 1 Episode 5

R.D. Lawrence–Wildlife Writer

November 8, 2017

I enjoy deciphering articles published in scientific journals and translating them into language a layman can understand.  I learned how to do this because of my long fascination with Pleistocene ecology.  Information about Pleistocene ecology almost entirely comes from scientific journal articles, and I found the language in these publications can be unnecessarily complex and oftentimes the writing is just bad.  I had to learn how to interpret them.  Some scientists are good writers, but others are not.  R.D. Lawrence (1921-2003) was a writer who felt the same way I do about language in scientific journals.  At 1 point in his life he was studying to be a biologist.  He wrote a thesis about stickleback fish, and his professor told him it was good, but he wanted him to rewrite it in the language used by scientific journals instead of the easy to understand language Mr. Lawrence had used.  He rejected this “babblespeak” and dropped out of school.  He later wrote 36 books about Canadian wildlife and won 7 awards.

The late R.D. Lawrence relaxing at home with his pet raccoon.

R.D. Lawrence was born in Spain to a Spanish mother and an English journalist who worked for Reuters.  At the age of 14 he was separated from his family during the Spanish Civil War, and he joined the side fighting against the fascists.  (Ironically, his brother joined the fascists.)  Though just a teenager, he led 1 military attack in the sewers against the fascists.  Eventually, he escaped to southeastern France and was later reunited with his family in England.  He fought for Great Britain during World War II.  He was at Dunkirk, rode a tank in North Africa, and was severely wounded during the D-Day invasion.  His injuries ended his military career.  He moved to Canada and worked as a journalist, while studying nature in his spare time.  He gathered enough material so that he was able to start getting his books about Canadian wildlife published.  Recently, I’ve read 3 of his books.

Mr. Lawrence and his wife bought some land in the wilderness of Ontario during 1962.  Here, they built a cabin where they spent weekends.  (He still worked as a journalist during the week.)  He bought the land before most of Ontario was logged over and converted into suburbs, so much of the wildlife was naïve and not particularly afraid of people.  He wrote about his experiences at this cabin in his book, The Place in the Forest.  The semi-tame animals frequenting his cabin yard included red squirrels, fox squirrels, flying squirrels, white-footed mice, snowshoe hares, and birds.  Bird seed and table scraps encouraged the creatures of the forest to hang around the cabin, and if the door was left open, they would enter the cabin and help themselves.  Mr. Lawrence and his wife adopted 2 orphaned raccoon kits and after they were grown and freed, they often returned and joined the feast.  Mr. Lawrence also wrote about some of the less tame inhabitants in the local wilderness–beavers, deer, wolves, black bears, and birds of prey.  He didn’t let worms and insects go unnoticed either.  My favorite chapter relates his encounter with a bald-faced hornet’s nest when he was climbing a tree to photograph a hawk’s nest on another nearby tree.

Mr. Lawrence’s wife died of a brain aneurism at a quite young age, prompting him to move to British Columbia where he decided to buy a boat and travel up the Pacific coast from Vancouver to southern Alaska by himself.  He wrote about this experience in his book, Voyage of the Stella.  When he fished for salmon to eat, he often caught weird species of fish–wolf fish, Pacific lancet fish, barrel eyes, and dogfish. He fed these to the killer whales that occasionally swam near his boat, and he even dove in the water with them while wearing his scuba gear.  The killer whales never bothered him, but he once had to fend off a blue shark.  On his journey he also encountered pods of Dall’s porpoises and a pair of whale sharks.  He refueled his boat at the Indian villages that dotted the coast.  Most of the Indians were friendly, but 1 drunk tried to hit him over the head with a ketchup bottle while he was trying to eat supper at a restaurant. The brave war veteran floored the Indian with an open palm blow to the forehead.

Mr. Lawrence demonstrated even more courage in his next book, The Ghost Walker.  He spent 8 months in a wilderness cabin located in a remote area of British Columbia that was 60 miles from the nearest town, and the only feasible connection to civilization was an hazardous canoe ride down a river.  He used this makeshift cabin as an home base for tracking a large male cougar.  He gained the cougar’s trust, and the big cat let the man follow him around.  Mr. Lawrence experienced several dangerous situations, aside from trusting the cougar not to turn around and eat him.  During a blizzard, Mr. Lawrence sought shelter in a creekside cave but found himself staring eye-to-eye with an hibernating grizzly bear.  Mr. Lawrence popped out of the cave like a “champagne cork” and fled, dropping his backpack which the angry bear tore to shreds. On another occasion he slipped down an icy slope, hit a tree, and sustained a concussion.  He administered his own first aid.  He often tracked the cougar after sunset, walking in the dark woods by himself for hours.  He was 1 brave soul.

I have 1 criticism of Mr. Lawrence.  He imagined he had established ESP connections with a cougar and a killer whale.  There is no rational scientific basis for his belief.  I’m sure it was his imagination, not an ESP connection.  He was just lucky the animals he “communed” with didn’t decide to attack and eat him.