Archive for the ‘Fossil Sites’ Category

The Alum Bluff Fossil Site in Northwest Florida

September 28, 2019

Scientists have known about the Alum Bluff fossil site for 100 years, but a recent study looked at 475 plant macrofossils and identified 46 species.  The site is located along the Apalachicola river where currents have eroded away sediment, revealing strata estimated to be between 13-16 million years old.  The site was dated using mammalian index fossils found in the same geological formation. Index fossils are used for estimating ages when there are no rocks at a site that can be radiometrically dated, but certain fossil species are known from specific ages based on radiometric dating from other sites.  Rhinos, 3-toed horses, and 4-tusked mastodons roamed the earth during the time these leaves, fruits, and seeds were deposited and preserved.  There are only 9 Miocene-aged fossils sites in North America containing plant remains.  In addition to Alum Bluff other Miocene plant macrofossil sites are found in Tennessee, Maryland, Delaware, Virginia, Mississippi, and Louisiana.

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Alum Bluff alongside the Apalachicola River.

The most common plant macrofossils at Alum Bluff are species of palm, hickory, and elm.  The authors of this study believe this site is just a random sample of the local flora as it existed then, and they don’t think it exactly matches the floral composition of the time.  Pine was rarely represented, and surprisingly no oak was found at all.  The species of elm they examined was new to science and extinct, though it may be ancestral to modern species of elm.  Other interesting species included sequoia, ephedra, Jerusalem thorn, elderberry, magnolia, cypress, beech, sweetgum, willow, grape, and sedge.  Sequoia no longer occurs in Florida, and Jerusalem thorn no longer ranges into North America, though it is still found in Eurasia.  The presence of ephedra suggests an arid sandy habitat within a moist forest.  There are also plant fossils that compare favorably in appearance to sycamore and mulberry  but weren’t conclusively identified. 7 species just could not be identified.

Stock Photo: Christ's thorn, Jerusalem thorn Paliurus spina-christi, fruiting.

Jerusalem thorn.  Found throughout Eurasia it became extinct in North America millions of years ago.

Based on the species of plants present, the authors of this paper estimate it was a subtropical climate with an average annual temperature of 66 degrees F and average annual precipitation of 43 inches.  Modern day Tallahassee enjoys an average annual temperature of  67 degrees F and average annual precipitation of 59 inches.  Miocene Florida experienced similar temperatures as modern Florida but was noticeably drier.

Reference:

Lott, Terry; S. Manchester and S. Corbett

“The Miocene Flora of Alum Bluff, Liberty County, Florida”

Acta Paleobotanica June 2019

https://content.sciendo.com/view/journals/acpa/59/1/article-p75.xml?tab_body=pdf

The Hoyo Negro Fossil Site Keeps Producing Surprises

May 5, 2019

I’ve already written about the Hoyo Negro fossil site located in Yucatan, Mexico twice (See: https://markgelbart.wordpress.com/2015/08/08/the-hoyo-negro-fossil-site-in-yucatan-mexico/ and https://markgelbart.wordpress.com/2017/09/13/new-species-of-late-pleistocene-ground-sloth-and-peccary-discovered-on-yucatan-peninsula/ ), but new and interesting discoveries keep happening inside this underwater cave.  Scuba divers previously found a 13,000 year old human skeleton, the bones of 30 species of large mammals, and bat guano, containing valuable paleoecological evidence at this site.  Included among the mammal specimens were 3 extinct animals new to science–2 species of ground sloth (Xibalbaonyx oviceps and Nahochichak xibalbahakah) and 1 species of peccary (Mucknalia minimas).  Recently, scuba divers found another human skeleton here, this 1 dated to 12,000 years BP; and scientists identified the bones of 2 species of extinct carnivores previously thought to have been restricted to South America.

A team of paleontologists looking through bones excavated from Hoyo Negro realized 1 labeled as coyote had been misidentified.  The remains actually belonged to Protocyon troglodytes, an extinct wolf-like animal.  Subfossils of this species have been excavated from sites located in 6 South American countries, but this is the first time a specimen has ever been found in North America.  This team of paleontologists also recognized a bear skull misidentified as belonging to a spectacled bear was actually the skull of an Arctotherium wingei. This species of extinct bear was known from fossil sites in 3 South American countries, and this specimen is also a first from North America.  Photos of bear fossils from other sites in the Yucatan peninsula indicate these also are Arctotherium.  These discoveries extend the known northern range limits of these species by over 1200 miles.

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I think this photo is the Arctotherium skull found in the Hoyo Negro.  This specimen is preserved better than any previously known.

The Yucatan peninsula supported a unique fauna during the last Ice Age.  Paleontologists recently named a new species of extinct jaguar (Panthera balamoides) from a few bones found at another site in the region. This means there were 4 species of large mammals living on the Yucatan that may not have been found anywhere else.  Moreover,  both North and South American species had ranges that overlapped here and possibly nowhere else.  For example dire wolves co-existed here with protocyon, another predatory canid.  It seems likely a vast desert grassland isolated the Yucatan peninsula during Ice Ages.  However, the proximity of the Caribbean Sea allowed for more precipitation on the peninsula than farther inland.  This fostered the growth of jungles and wetlands that supported a greater variety of fauna, and new species that were different from populations on the other side of the desert evolved in this isolated paleoenvironment.

Reference:

Schubert, Blaine; et. al.

“Yucatan Carnivores Shed Light on Great Biotic Interchange”

Biology Letters May 2019

Peccary Cave in Arkansas

October 21, 2018

Perhaps the best site for Pleistocene fossils in Arkansas is Peccary Cave located in Newton County.  The site was first excavated in 1960s, and a follow-up expedition prospected for fossils again in the early 1990s.  The fossil remains of at least 51 species of mammals have been found here. 4000 specimens of a minimum of 64 individual flat-headed peccaries (Platygonus compressus) were discovered in the cave, hence the name.  The bones of other extinct species excavated from the cave include mammoth, mastodon, bison (Bison antiquus), stag-moose, helmeted musk-ox, tapir, beautiful armadillo, and dire wolf.  There are also remains of extralimital species found here that no longer occur in the region–grizzly bear, pine marten, porcupine, heather vole, and numerous other rodents and insectivores of northern affinities.  Plenty of species still found in the region are represented in the cave as well such as beaver, otter, muskrat, raccoon, coyote, gray fox, opossum, and either mule or white-tailed deer. Reptile and amphibian specimens have been excavated from the cave along with a few human-made artifacts of unknown cultural origin.

Map of Arkansas highlighting Newton County

Newton County, location of Peccary Cave.  

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Illustration of the flat-headed peccary.  Peccaries didn’t use Peccary Cave as a den.  Instead, they either fell inside or their bones were washed into the cave when the nearby creek flooded.  Birds of prey dropped or defecated smaller animals into the cave from overhanging trees.

The fossils represent several different climate phases.  The lowest level contains fossils over 22,000 calendar years BP, a climate phase that includes a weak interstadial and the following early glacial maximum.  Mixed Ice Age woodlands of spruce, pine, and hardwoods interspersed with prairies predominated.  7 different species of squirrels lived in the region then, showing how many diverse habitats occurred here.  Red squirrels and least chipmunks, now absent from the region, preferred spruce forests; gray squirrels, fox squirrels, and southern flying squirrels occur in temperate hardwood forests; woodchucks like meadows; and 13-lined ground squirrels require tree-less plains.  The author of the study discussed below thinks the following glacial maximum caused the entire Missouri Plateau to become inhospitable desert because there are few fossils from the site, dating to between 21,000 calendar years ago-15,000 calendar years BP.  Undoubtedly, the region became more arid during this climate phase, and desert scrub grassland likely predominated, but I think there are alternative explanations for the lack of fossils during this time period here: a) the cave entrance may have become closed and/or b) the barren landscape allowed animals to see the trap entrance and avoid it whereas before it was hidden by thick vegetation and animals frequently fell inside.  Without overhanging limbs there was no perch for birds of prey to drop of defecate the remains of their meals.  Moreover, the nearby creek dried up, so there were no floods to wash fossils into the cave.

The upper level of sediment represents a warm dry interstadial post 15,000 calendar years BP when the region was dominated by grassland.  Bison fossils appear during this phase, and toad fossils outnumber frog bones.  Toads can survive better than frogs in more arid climates.

Kurt Wilson wrote his PHD thesis about the peccary and dire wolf bones found in Peccary Cave.  His paper has interesting information, but it is incompletely researched, and his conclusions are logically flawed.  He believes flat-headed peccaries were always an uncommon species.  Part of his reason for this assertion is based on his incorrect observation that “the southeast is virtually devoid of records (of flat-headed peccaries), except for a dozen localities in Florida.”  Wilson is unaware of 2 sites in north Georgia (Yarbrough Cave and Ladds) and 1 site in coastal South Carolina where fossil remains of flat-headed peccaries have been found.  It is also illogical to assume a species was absent from a region based on its absence in the fossil record.  Large areas of the southeast are devoid of fossils because the local geology is not conducive to fossil preservation, not because animals didn’t live there in the past.

Wilson concludes flat-headed peccaries became extinct due to climate change based on 4 lines of evidence that are easily debunked.

1. He dismisses overhunting by humans as a cause of flat-headed peccary extinction when he regurgitates the tired old claim of Meltzer and Grayson (an archaeologist and anthropologist…not paleoecologists) that there isn’t enough archaeological evidence of human interaction (kill sites) with this species.  I consider this reasoning absurd in the extreme.  99.999…etc% of animals that ever lived on earth left no fossil evidence whatsoever.  It has always seemed unreasonable to me to expect the remains of the final populations of a species that overlapped with man for less than 2000 years to be preserved in the fossil record.  The chances of this happening are tiny.  I’ve noticed Grayson’s recent book published in 2016 is frequently being cited in new papers about Pleistocene vertebrates.  Grayson was blatantly dishonest in this book in the way he characterized a study that rules out climate change models of extinction.  (See: https://markgelbart.wordpress.com/2017/01/23/donald-graysons-disingenous-case-against-overkill/ ) Grayson lied and he knows he lied.

2. Wilson assumes flat-headed peccaries became extinct in this region about 22,000 calendar years BP because their remains don’t occur in cave sediment after this date.  (When Wilson writes of extinction in his paper he means regional disappearance or extirpation because he’s aware terminal dates for this species in other regions are 11,000 calendar years ago.  Nevertheless, he clumsily never makes this distinction in his paper.)  He asserts peccaries became extinct here because the climate became too arid for them.  Again, he is basing his assertion on the dubious assumption that the absence of evidence is evidence of absence.  I think flat-headed peccaries were probably even more abundant during the arid climate phase because they were anatomically well-adapted to dry dusty environments.  Flat-headed peccaries had extensive structures in their nasal passages that helped filter dust.  Wilson must be unaware there are at least 9 fossil sites where herds of flat-headed peccaries were buried during sandstorms.  (See: https://markgelbart.wordpress.com/2013/03/10/when-sand-dunes-buried-herds-of-flat-headed-peccaries/ ) This suggests they were common in desert environments.  Flat-headed peccaries may have avoided falling in Peccary Cave after 22,000 calendar years BP because the area around the entrance to the cave was barren and not hidden by vegetation.  None happened to fall in the cave after this date, but that doesn’t mean they didn’t still occur in the region.  Other fossil sites in the region yield the remains of horses, but not a single horse fossil has been found in Peccary Cave.  Horses were likely another abundant species in the region that just happened to never fall in or enter Peccary Cave.

3. Wilson did a stable isotope analysis of 2 flat-headed peccary teeth and concluded they fed upon just a few leguminous plant species, so they became extinct when these limited number of plant species disappeared from the region.  I don’t believe the entire dietary breadth of a species can be determined from such a small sample size.  Moreover, 1 study suggests stable isotope analysis is not at all reliable.  (See: https://markgelbart.wordpress.com/2016/06/24/trust-the-coprolites-not-the-stable-isotope-analysis/ )  Scientists compared the results of a stable isotope analysis of moa bones with actual fossil droppings.  The stable isotope analysis was wrong.  Flat-headed peccary teeth were built to eat grass and tough vegetation.  A species that survived millions of years of climate change didn’t exclusively feed upon just a few species of leguminous plants.

4. Wilson asserts flat-headed peccaries were uncommon and thus vulnerable to extinction.  However, a new genetic study of 12 flat-headed peccary individuals from Sheridan Cave, Ohio, dating to just before their extinction revealed populations of this species were diverse and expanding.  This suggests flat-headed peccaries were common, adaptable, and had a wide geographical distribution until the species’ demise.

Peccary Cave has yielded a wealth of information for paleoecologists, and I’m shocked at how little research has been published about this site.  I’ve been able to find about half a dozen research papers.  There hasn’t been a scientific excavation of the site since 1993, though amateurs are currently pillaging it.  Most of the specimens from this site have not yet been described in the scientific literature, and they are not listed on the paleobiology database. An early report of the site mentions the existence of peccary “droppings.”  Yet, nobody has studied the coprolites (please email me if I’m wrong)–an outrageous oversight.  We could actually find out what flat-headed peccaries ate, instead of guessing based on stable isotope analysis.  I’m not sure the coprolites were even collected and stored in a museum.  There should be hundreds of published papers about this site, not just a paltry 6.  I’ve come across other understudied fossil sites and collections in my research, but this site might possible be the most underappreciated.

References:

Bell, Kenneth; and Lee Davis

“Sinkhole Excavations in Peccary Cave, Newton County, Arkansas”

Arkansas Academy of Science 47(30) 1993

Davis, Lee

“Biostratigraphy of Peccary Cave, Newton, County, Arkansas”

Arkansas Academy of Science 1969

Perry, Tahlia; et. al.

“Ancient DNA Analysis of the Extinct North American Flat-headed Peccary (Platygonus compressus)”

Molecular Phylogenetics and Evolution 2017

Wilson, Kurt

“Late Pleistocene Extinction of the Flat-headed Peccary on the Ozark Plateau: Paleozoological Insights from Peccary Cave”

Iowa State Graduate Thesis 2017

 

 

 

New Study Supposedly Debunks Proposed Pre-Clovis Evidence from the Coats-Hines and Topper Sites

June 23, 2018

Archaeologists claimed they had “unequivocal” evidence humans butchered a mastodon at the Coats-Hines site located in Tennessee.  Now, some of these same archaeologists recently published a paper admitting their evidence was equivocal.  I wrote a beautiful article on my blog about the Coats-Hines site a number of years ago, and it always gets a lot of hits early during the school year because a teacher uses it as a reference for a school assignment.  Unfortunately, the assumption the site includes evidence of human-butchered mastodon remains may be bogus.  (See: https://markgelbart.wordpress.com/2013/04/15/the-coats-hines-pre-clovis-site-in-williamson-county-tennessee/ )

The Coats-Hines site is located adjacent to a golf course.  During construction of the golf course 40 years ago workers found the remains of a mastodon.  Further digging by trained experts over the years yielded the remains of 3 more mastodons, white-tailed deer, muskrat, turkey, and painted turtle.  This most recent paper noted the additional identification of ground sloth bones (probably Harlan’s) from the site.  A mastodon vertebrae apparently had cut marks on it, suggesting evidence of anthropogenic butchery, and it was associated with supposedly human-made artifacts.  In a paper published just 7 years ago the archaeologists wrote it was “unequivocal” evidence of human butchery.  However, in his more recent study Jesse Tune admits the cutmarks could’ve been caused by the bone being tumbled against rocks in an high energy stream environment.  He thinks the artifacts associated with that specimen are geofacts.  A geofact is a natural stone formation that resembles an human-modified object.  The stones come from local outcrops that naturally eroded into the stream.  There are definitive human-made tools at Coats-Hines, but they were found some distance away from the mastodon bones.  Coats-Hines was a former stream, and deposits of different ages can get mixed together when currents erode through different aged strata.

Jesse Tune used what he learned from studying the Coats-Hines site to debunk claims made for the antiquity of the Topper site in South Carolina, and the Burnham site in Oklahoma.  Archaeologists excavating these sites claim the evidence they found was older than the Last Glacial Maximum.  (The LGM dates to roughly between 18,000 years BP-22,000 years BP.)  Jesse Tune thinks the evidence at these sites consists of geofacts eroded from adjacent local outcrops that perhaps mixed with real artifacts of more recent origin in an high energy stream.

The new paper (referenced below) includes the Coats-Hines site as a proposed pre-LGM site.  This puzzles me because I can’t find anyone who ever claimed the artifacts and evidence from Coats-Hines dated to before 22,000 years ago.  The sediment around the mastodon bone thought by some to be butchered by humans produced a radio-carbon date of 13,100 years BP (~=15,000 calendar years BP).  This is well after the LGM.  I always considered Coats-Hines to be pre-Clovis but not pre-LGM.  It seems as if the authors of this paper are making a straw man argument because as far as I can determine, nobody claimed Coats-Hines was pre-LGM.

Image result for straw man

Who claimed Coats-Hines was pre-LGM?  I asked 2 authors of the below study but I didn’t get a response.  Are they making a strawman argument about Coats-Hines?

References:

Tune, Jesse; et. al.

“Assessing the Proposed Pre-Last Glacial Maximum Human Occupation of North America at Coats-Hines-Litchy, Tennessee and Other Sites”

Quaternary Science Reviews April 2018

Wolf, Aaron; Jesse Tune, and John Broster

“Excavations and Dating of Late Pleistocene and Paleoindian Deposits at the Coats-Hines Site, Williamson County, Tennessee”

Tennessee Archaeology 5 (2) Fall 2011

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

Hurricane Ivan Uncovered a 60,000 year old Cypress Forest in the Gulf of Mexico

August 9, 2017

In 2004 Hurricane Ivan spawned 140 mph winds, 90 foot waves, and the fastest sea floor current ever recorded.  That incredible sea floor current removed a sediment layer covering a 60,000 year old cypress forest in the Gulf of Mexico.  The exposed trees formed a natural reef, attracting a concentration of fish and other sea life 60 feet below the ocean surface and 15 miles offshore.  Fishermen noticed the unusual concentration of fish and asked scuba divers to investigate.  The scuba divers discovered the uncovered ancient forest, and scientists are now studying this rare site.

The scientists who visited the flooded forest were impressed with the marine life they encountered–flounder, cardinal fish, red snapper, blennies, sea bass, moray eels, sandbar sharks, hawksbill turtles, octopus, boring worms, anemones, and sponges.  But they were even more impressed with the ancient cypress wood they brought with them to the surface.  They sawed through it in the laboratory and smelled fresh sap.  Nevertheless, they couldn’t use radiocarbon dating because they discovered the wood was over 50,000 years old–too old for that method.  Instead, they found the nearest organic material that could be dated and estimated a 60,000 year old date based on stratigraphic location and assumed rates of deposition.

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Map of weather stations in south Alabama.  During Ice Ages dry land extended for miles into the Gulf of Mexico.  Mobile Bay was a valley of forests and grasslands.  Dauphin Island and Fort Morgan were high hills “hundreds of feet above the surrounding landscape.”

When it was alive, this flooded forest stood during a time period classified as Marine Isotope Stage 3.  I am fascinated with MIS3 because the dramatically fluctuating climate cycles had a major impact on natural communities.  MIS3 occurred just before the Last Glacial Maximum (the coldest stage of the last Ice Age), but unlike the LGM, MIS3 experienced warm interstadials alternating with cold phases.  Many geographical regions hosted an admixture of northern flora and fauna with warm climate species of plants and animals because of this climatic instability.  Tree rings on the fossil cypress wood excavated from this locality demonstrate this instability.  The tree rings provide a 489 year record of climate from MIS3.  The cypress tree rings show climate varied with warm wet years and dry cold spells but for the most part they are narrower than tree rings found in modern day cypress trees.  This reflects a cooler drier climate with lower levels of carbon dioxide in the atmosphere.  The trees were especially stressed during the last 50 years of their existence, and they all died at the same time, though the trees were of different ages.  Saltwater intrusion killed the trees.

Sea level rose rapidly here, probably during a warm phase of climate when glaciers were melting.  Cypress wood is resistant to decay, an adaptation for living in aquatic environments, but when exposed to air will eventually rot away.  The dead stand of cypress wood likely stood for decades, perhaps a century, before becoming covered in sand and mud.  Thus sealed off from air, it was preserved for tens of thousands of years.  Now that it is exposed to oxygen again, it will decay into nothing in a few centuries.

Scientists cored into the mud around the trees and took samples of pollen to analyze the type of natural environment that existed here 60,000 years ago.  Cypress, oak, and alder pollen dominated.  The palynologist who analyzed the pollen composition (the data as far as I know is still unpublished) concluded the forest was a rare type that no longer occurs in the region.  The closest modern analogue is classified as an Atlantic Coastal Plain Blackwater Bar/Levee Forest.  This type of forest occurs in small areas near the coasts of North and South Carolina.  Bar/Levee forests grow on soil formed on the inside bend of a river.  Sediment accumulates here through deposition, and the area is seasonally flooded.  (Indeed, this particular forest occurred alongside a river, and the paleomeander scar is still visible at the bottom of the ocean adjacent to the flooded forest.)  Dominant trees in a Bar/Levee forest are cypress, river birch, laurel oak, overcup oak, willow oak, sweetgum, red maple, elm, and loblolly pine.  The understory consists of holly and hop hornbeam along with red maple and ash saplings.  The shrub layer is made up of blueberry, titi, sweetspire, grape, poison ivy, climbing hydrangea, Alabama supplejack, greenbrier, sweet pepperbush, violet, and sedge.  Spanish moss covers the trees.  Bar/levee forests are similar to bottomland hardwood forests but are distinguished by the abundant presence of river birch or water elm (Planara aquatica which is not a true elm).

Macrofossils of Atlantic white cedar and palm have also been found among the dead cypress.  There are small disjunct colonies of Atlantic white cedar scattered throughout the southeast, indicating it was more widespread in the region during the Ice Age.  (See: https://markgelbart.wordpress.com/2012/03/11/the-discontinuous-range-of-the-atlantic-white-cedar-chamaecyparis-thyoides/ ) The presence of palm shows that climate, though cooler than that of today, was still warm enough for that species.  I suspect this was a unique forest that doesn’t exactly match any classified natural community of the present day.

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60,000 years ago, a cypress and oak forest grew at a location 15 miles off the coast of Alabama.  It was rapidly inundated during a sudden rise in sea level, becoming covered in sediment before the cypress trees rotted away.

The pollen evidence suggests alder was a pioneer species here that probably became established when the point bar of the river began depositing sediment.  Cypress and oak became dominant for about 500 years.  Then, after salt water intrusion killed the cypress, grass pollen predominates, suggesting a salt marsh replaced the cypress forest.  Extinct megafauna such as mastodon, tapir, and capybara undoubtedly passed through this environment, but vertebrate fossils have yet to be found.

Below is a documentary about the flooded forest–the source of information for much of this blog entry.

Reference:

Schafale, M; and A. Weakley

“Classifications of the Natural Communities of North Carolina, third approximation”

North Carolina Natural Heritage Program 1990

Ice Age Western Lakes and Altered Bird Migrations

April 9, 2017

I photographed a lesser yellowlegs (Tringa flavipes) at Woodbridge Lake, Evans, Georgia last weekend.  I was thrilled to see this transient species in such an unexpected locality.  Lesser yellowlegs and many other species of sandpipers spend the winter in South America, Florida, and the coasts of Georgia and South Carolina, but they migrate to their summer breeding grounds in western Canada during spring.  The present day breeding grounds of 22 American species of sandpipers, plovers, curlews, and dowitchers were mostly or completely under glacial ice during Ice Ages.  One might ask where these species bred during Ice Age summers.  Weather patterns were much different then.  Today, much of the west is arid desert, but during Ice Ages the region enjoyed a cooler and much wetter climate.  Many large lakes existed in western North America, and they provided beach, reedy marsh, and open water habitats for aquatic birds.  A large prehistoric body of water, known as Pleistocene Lake Manix, covered what today is the Mojave Desert, and Pleistocene Fossil Lake inundated the modern day site of a desert in central Oregon.  Both of these sites yield abundant remains of the aquatic bird species that formerly spent all or part of their lives there.

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Map of western North America during the Ice Age.  More precipitation and cooler weather patterns resulted in large lakes in place of present day arid landscapes.

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Lesser yellowlegs in Evans, Georgia.  This species is a transient here.  It spends winters in South America, Florida, and the southeastern Atlantic Coast, but breeds during summer in western Canada.

Lesser Yellowlegs Range Map

Range map for a lesser yellowlegs.  Many species of sandpipers have similar ranges.  Almost their entire breeding range was under glacial ice during Ice Ages.  They shifted their breeding ranges to the lakes in western North America that no longer exist and are deserts today.

The entire breeding range of the white fronted goose, the blue goose, and 10 species of ducks was also under glacial ice during the late Pleistocene.  The geese and some species of ducks shifted their breeding ranges to these western lakes.  However, harlequin, eider, king eider, and the extinct Labrador duck have/had more easterly distributions and likely bred near the Atlantic coast south of the ice sheet.  Other migratory species of birds that bred on western lakes during Ice Ages include whooping cranes, northern skuas, and arctic loons.

Many species of aquatic birds that breed in western Canada during summer still breed in western states as well wherever wetlands still exist.  Instead of shifting their breeding ground migration north, these species expanded their summer breeding grounds but still also nest within their Pleistocene range.  This list of species includes 2 loons, 2 grebes, white pelicans, 2 swans, 10 ducks, sandhill cranes, Virginia rails, Hudsonian godwits, American avocets, 3 phalaropes, and 3 jaegers.

The abundant large lakes of Pleistocene western North America attracted some species of non-migratory birds that no longer occur in the region.  Anhingas are fish-eating birds confined to southeastern North America today, but fossil evidence shows they lived in Oregon during the Ice Age.  The beautiful scarlet ibis no longer occurs north of Central America but ranged to Oregon then also.

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The scarlet ibis no longer occurs north of Central America but did live as far north as Oregon during Ice Ages.

Western lakes evaporated and turned into desert following the end of the Ice Age.  A number of species failed to adapt by shifting their ranges to newly available Canadian habitat, and they became extinct.  The extinct species include a flamingo, 2 gulls, a jaeger, a cormorant, a grebe, a swan, a goose, and a shelduck.

Breeding colonies of aquatic birds attract predatory species such as bald eagles and great horned owls.  Fossil evidence of both these species is found at most of the sites of these former Pleistocene lakes.

The extinct western lakes would have been a birder’s paradise. Paleo-indians saw the wealth of avifauna as a food source.  Paleo-indians had no television, radio, and little in the way of entertainment, so perhaps bird-watching was a leisure activity for them after they filled their bellies with spit-roasted duck.

Reference:

Jefferson, George

“Remains of the Late Pleistocene Avifauna from Lake Manix, Central Mojave Desert, California”

Bulletin of the Natural History Museum of Los Angeles County June 1985

Pleistocene Terrapins (Malaclemys terrapin)

March 20, 2017

Until recently, there was little fossil evidence of diamond-backed terrapins. This species inhabits salt marshes and mangrove swamps from the Gulf of Mexico to Cape Cod, Connecticut.  For most of the past 2 million years, sea level has been much lower than it is today due to the larger ice caps of long-lasting Ice Ages.  This means many potential fossil sites where the remains of terrapins might be found are submerged deep underwater and difficult to access.  Sea level has been the same or higher than it is today probably for less than 20% of the last million years, and this reduced the chances easily accessible fossil sites developed in salt marsh zones.  However, the remains of terrapins dating to the Pleistocene have been excavated from  3 sites in Florida, 1 in Georgia, and 1 in South Carolina.  These specimens weren’t described in the scientific literature until 2012.

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The diamond-backed terrapin is adapted to living in salt marshes.

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Diamond-backed terrapin habitat–a salt marsh.

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Diamond-backed terrapin range map.

The 3 sites in Florida where Pleistocene-age terrapin remains were discovered are Page-Ladson, Aucilla River, and Wekiva River.  Terrapin material turned up at Edisto Beach, South Carolina, and fossil hunters found terrapin bones in spoil piles dumped on Andrews Island, Georgia.  (All of Andrews Island is manmade, consisting of spoil piles dredged from the South Brunswick River, aka Fancy Bluff Creek. The Army Corps of Engineers periodically dredges the river to keep it deep enough for safe shipping. Plants have taken root there and it is an haven for wildlife.) The specimens are thought to be Pleistocene in age because they are associated with bones of other species that lived then.  The 3 sites in Florida and the 1 at Edisto Beach commonly yield bones of extinct Pleistocene mammals.  The spoil piles on Andrews Island contained the remains of snapping turtles (Chelydra serpentina), yellow-bellied cooters (Trachemys scripta), and the extinct giant tortoise (Hesperotestudo crassicutata).  These species all lived during the late Pleistocene.  The presence of these 3 species along with the terrapin indicates the local environment at the time of deposition was a brackish marsh bordering an open grassy savannah. Snapping turtles and yellow-bellied cooters are fresh water species that can tolerate brackish conditions, and giant tortoises preferred dry land environments.

Terrapins are not closely related to sea turtles.  Morphological and genetic evidence suggests they are most closely related to freshwater turtles in the Graptemys genus.  In North America this genus includes 10 species of map turtles and saw backs. Terrapins are the only turtle species uniquely adapted to live in salt marshes.  They have lachrymal salt glands that help them get rid of excess salt.  These are absent on all species of fresh water turtles.  Terrapins are also able to drink the layer of rain water that temporarily floats on top of salt water.  Terrapins feed upon shellfish–periwinkle snails are their favorite but they consume shrimp, crabs, and bivalves as well.

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The salt marsh periwinkle (Littorina irrorata) is the diamond-backed terrapin’s favorite food.

Terrapins were formerly so abundant they constituted the main source of protein for coastal slaves during the 18th and 19th century.  But a faddish craze for turtle soup circa 1900 greatly reduced their numbers.  All of the finest restaurants served turtle soup, and it was the most expensive item on the menu.  I’ve only had the opportunity to eat turtle meat once.  Turtle meat is very delicious, tasting like lobster.  Because terrapins feed on shellfish, their flesh likely reflects their diet.  Terrapins are presently a protected species but are still considered threatened.  Real estate development destroys their habitat, they drown in crab traps, cars run over them, and there are people who still eat them.  Egg-eating raccoons flourish as well, since most large predators that kept their population in check no longer exist on the east coast.  If I get the urge to eat turtle again, I’ll stick with the common snapping turtle which as their name suggests are still common.

Reference:

Ehret, Dana; and Benjamin Atkinson

“The Fossil Record of the Diamond-backed Terrapin, Malaclemys terrapin (Testudines: Emydidae)”

Journal of Herpetology 46 (3) September 2012

 

A Pleistocene-age Carolina Parakeet (Conuropsis carolinensis) Fossil Finally Discovered

December 29, 2016

The Carolina parakeet was a common species living in old growth bottomland forests until Europeans settled eastern North America.  Overhunting and deforestation doomed this only temperate species of parakeet. The colorful noisy birds were an agricultural pest that destroyed ripening fruit when they fed upon the seeds inside the pulp.  Orchardists wiped out entire flocks.  Though parakeets are supposed to be intelligent, they were not well adapted to avoiding patient men with guns.  A farmer firing his weapon into a flock (the birds routinely congregated in flocks of 200-300) caused the survivors to fly in a wide circle and return to the same place where their feathered comrades had just been killed.  A farmer could slaughter the entire flock in an afternoon without moving from the same spot.  Carolina parakeets nested in large hollow trees, but lumbering operations during the late 19th century eliminated their homes as well.  The last population of Carolina parakeets was probably rubbed out by market hunters seeking red and green and yellow feathers, then fashionable in women’s hats.  The last wild specimen was taken near Lake Okeechobee, Florida in 1904, and the last captive specimen died in the Cincinnati Zoo in 1918, coincidentally the same place and year where the last passenger pigeon died.

Until recently, the only North American fossil remains of a parakeet was a specimen found in Nebraska, dating to the mid-Miocene (about 16 million years BP).  Scientists are uncertain if this specimen represents a species ancestral to the Carolina parakeet, the same species, or a different lineage.  In any case no fossil remains of a parakeet dating to the Pleistocene age (~2 million years BP-11,000 years BP) had ever been found in North America.  Carolina parakeets lived in habitat where preservational processes don’t often occur.  Most bird remains are found in caves where they were carried by roosting owls or hawks.  There aren’t many caves in the lowland habitats favored by parakeets.  Moreover, the flesh of parakeets was toxic to many predators because they fed on poisonous cocklebur seeds.  Their colorful plumage may have worked as a deterrent to predators who learned to avoid the well-marked prey that may have sickened them previously.  Although preservational bias was the probable reason why remains of this species had never been found, it was possible Carolina parakeets were a recently evolved species that colonized North America, following the end of the most recent glacial-interglacial transition.  But finally, just a few years ago, the remains of a Pleistocene-age Carolina parakeet were unearthed at the Dickerson Coquina sand pit in St. Lucie County, Florida.  Fossils found at this site are estimated to be somewhat younger than 730,000 years BP-430,000 years BP, proving that Carolina parakeets had a very long history in North America.

Map of Florida highlighting St. Lucie County

St. Lucie County, Florida.  The Dickerson Coquina Pit fossil site, located in this county, yielded the first known Pleistocene-age remains of a Carolina parakeet.

The extinct Carolina parakeet.

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Range map of the formerly widespread Carolina parakeet.  It was doomed by overhunting and deforestation.

Sand is mined from the Dickerson Coquina sand pit to replace sand lost on Hutchinson Island to erosion.  Hutchinson Island is located in the same county as the sand pit.  Pleistocene-age fossils have been found in the sand pit and on the sand dumped on Hutchinson Island Beach.  Electron spin resonance dating determined the specimens excavated from the sand pit were above a layer dated to 730,000 years BP-430,000 years BP.  The species found are consistent with this dating and were common during the late Pleistocene including giant tortoise ( Hesperostestudo crassicutata ), box turtle, snakes, sharks, rays, fish, mammoth, paleollama, tapir, horse, pampathere, dire wolf, and jaguar.  No bison fossils were found.  Bison didn’t colonize North America until 300,000 years ago, so the absence of this species is consistent with an estimated date of 400,000 years BP for the fossils found here.

The remains of at least 24 species of birds have been excavated from these sands including a number of interesting extinct or extralimital species aside from the Carolina parakeet.  (The complete list of species found is described in the paper linked below as a reference).  Ornithologists have identified the remains of great auk ( Pinguinus impennis ), short-tailed albatross (  Phoebastrea albatrus ), northern gannet ( Morus bassanus ), an extinct stork ( Ciconia maltha ), and an unnamed extinct crane ( Grus sp. ).

Today, the short-tailed albatross nests on just 4 islands in the North Pacific between Hawaii and Japan (including Midway near where the famous WWII battle took place). But the presence of their bones in Florida means this species formerly ranged throughout the North Atlantic Ocean.  They probably nested on islands that were inundated by rising sea levels about 400,000 years ago, causing their extirpation here, but they didn’t necessarily nest in Florida.  Storms may have blown flocks inland.

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Today, the short-tailed albatross is a rare bird that nests on 4 islands in the North Pacific, but it also lived in the Atlantic Ocean during the middle Pleistocene.

The great auk was a denizen of rocky islands off the coast of Maine and Canada until 1852 when it was overhunted to extinction.  I hypothesize they nested on a rocky island off the coast of South Carolina, known as Bulls Scarp, that was above sea level during Glacial Maximums.  This possible nesting site may explain why they were close enough to have fished waters off the coast of Florida.  It’s likely storms blew this species inland as well.

A large, stuffed bird with a black back, white belly, heavy bill, and white eye patch stands, amongst display cases and an orange wall.

The great auk was overhunted to extinction by 1852.  Remains of this species were also found at this site.  I hypothesize that during Glacial Maximums this species may have nested as far south as South Carolina.

Northern gannets nest on subarctic islands in the North Atlantic but range throughout most of the Atlantic when seeking fish.  They too may have nested on Bulls Scarp.  The extinct species of stork probably ate carrion and depended upon the existence of large herds of megafauna for a major part of its food supply.  Not enough skeletal material has been found here from the large extinct species of crane to officially name it.  The fossil bone recovered from the sand pit resembles that from an extinct flightless crane that formerly lived in Cuba, but it is not an exact match.  This species was probably not flightless, like its Cuban cousin, because there were too many predators on the mainland.

Reference:

Kilmer, John; and David Steadman

“A Middle Pleistocene Bird Community from Saint Lucie County, Florida”

Bulletin of the Florida Museum of Natural History 2016

http://www.flmnh.ufl.edu/files/2514/8113/2040/Vol55No1_archival.pdf

The Pleistocene Champlain Sea

December 22, 2016

The weight of a glacier depresses the earth’s crust, a geological process known as crustal downwarping.  The Laurentide Ice Sheet covered most of eastern Canada during the Last Glacial Maximum, but a sudden warm phase of climate led to the rapid recession of its southern lobe.  About 13,000 years ago ocean water flooded into this glacial depression located in the present day region of eastern Quebec and Vermont, creating the Champlain Sea. The transgression of ocean water into land recently depressed by a glacier is termed eustatic sea level rise.  The Champlain Sea was bordered on its northern edge by melting ice cliffs formed by the retreating glacier, while a marshy tundra existed on its south side.  Over time this tundra was colonized by spruce trees.  This boreal forest was in turn replaced by a landscape of mixed conifers and northern hardwoods.  Meltwater and falling chunks of ice from the glacial cliffs reduced the salinity of the Champlain Sea, making it a brackish estuary teaming with a rich diversity of marine life.

Map of the pre-historic Champlain Sea.  It was created by crustal downwarping and fed by melting glaciers.  Ocean water flooded into this basin via the St. Lawrence River.  Isostatic rebound terminated the existence of this sea.

Lévis is located in Southern Quebec

Location of Levis, Quebec.  An excellent fossil site is found in the St. Nicholas borough of this city, containing many species that lived in the defunct Champlain Sea.

The fossil record suggests the white whale ( Delphinapterus leucas ) was the most common large mammal living in the Champlain Sea.  The white whale feeds upon fish, cephalopods, and shellfish.  The presence of a large population of white whales indicates an abundance of fish, and this is corroborated by the remains of both fresh and saltwater species found in deposits dating to this age here, including cod, tomcod, eelpout, capelin, smelt, spoonhead sculpin, lake cisco, lake char, wrymouth, long-nosed sucker, lumpfish, 3-spine stickleback, sturgeon, and salmon or trout.  Humpback, finback, and bowhead whales, and harbor porpoises also frequented the Champlain Sea.  Harp and bearded seals bred on pack ice, ringed seals bred on the shore, and harbor seals swam in the open water.  Herds of walruses rested on the ice edge.  Scientists have even excavated the remains of birds here–long-tailed ducks, thick billed murres, common eiders, and arctic terns.  The foot bone of an old arthritic grizzly bear was found at St. Nicholas, the best fossil site in the region where the remains of many species were buried under tidal current sands.  Polar bears probably roamed along the shores, but fossil evidence of their presence here has yet to be discovered.Image result for beluga whale

Fossil evidence suggests white whales were the most common whale species in the Champlain Sea.

In 1849 geologists were surprised to find whale bones and the remains of marine invertebrates such as clams, scallops, mussels, barnacles, and sea urchin in landlocked Vermont, and it took them a while to determine a vast inland sea resulting from retreating glaciers was the explanation for the presence of these fossils.  The sea existed from about 13,000 BP to ~10,000 BP.  Saline levels often fluctuated, depending upon the varying quantities of meltwater, and the sea gradually became more shallow as the earth’s crust rebounded.  The rise of the earth’s crust following the retreat of a glacier is known as isostatic rebound–the opposite of crustal downwarping.  The sea also became warmer over time.  Arctic saxicoue was an early dominant clam, but eastern soft-shelled clams, a warmer water species, replaced them.

Eventually, isostatic rebound split the Champlain Sea into 2 freshwater lakes and blocked their outlets to the St. Lawrence River and Atlantic Ocean.  Lake Lampsilis, named after a common species of freshwater mussel ( Lampsilis radiati ), lasted until ~8,000 years BP, when isostatic rebound completely eliminated the basin that held the lake.  Today, Lake Champlain is a freshwater relic of what was formerly an enormous brackish sea.

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Champlain Lake is a tiny remnant of the once vast Champlain Sea.

Reference:

Harrington, C. Richard; Marc Coornoup, Michael Chastia, Tara Fulton, and Beth Shapiro

“Brown Bear (Ursus arctos) (9880 BP) from Late Glacial Champlain Sea Deposts at St. Nicholas, Quebec, Canada, and the Dispersal History of Brown Bears”

NRC Press 2014