Archive for February, 2015

393,646 Gulf Menhaden (Brevoortia patronus) in the Alabama River

February 25, 2015

Researchers studying fish assemblages in the Alabama River netted 393,646 gulf menhaden, a remarkable collection because this species had previously been unrecorded from this tributary.  Scientists investigating the fish composition of the Alabama River  used nets to sample 19 sand and gravel bars from mile 22.9 to mile 72.  They sampled night and day as well as seasonally.  In all they collected 48 species from 41 sampling locations.  They discovered 2 other species previously unrecorded from the Alabama River–gulf killifish (Fundulus grandis) and inland silverside (Menidia beryllina).  The purpose of this study was to compare their fish survey with past collections to gain insight into how fish assemblages change over time.  180 fish species have been recorded from the Alabama River including 33 found nowhere else in the world.  The scientists who conducted their study found low similarity between their sampling and past collections.

Gulf menhaden.  Formerly unknown in the Alabama River, it is now perhaps the most abundant species there.

Tombigbeerivermap.png

Map of the Coosa, Alabama, and Tombigbee Rivers.  Incidentally, an ornithologist from Auburn University claims to have seen an ivory-billed woodpecker in the bottomland forests of the Tombigbee River.

River conditions change drastically over time.  Dike-building, damming, and dredging greatly alter modern day river patterns, thus influencing the composition and abundance of various fish species.  But before man colonized southeastern North America, changes in climate also greatly altered river patterns.  During cold dry climate stages, rivers changed into braided patterns, shrinking in size and becoming clogged with sand bars.  Flooding was far less common.  Sudden shifts to warm climate phases transformed rivers to a supermeandering pattern when massive floods were common.  Eventually, rivers settled into a normal meandering pattern with a moderate frequency of flooding, such as occurs today.  Meandering patterns create oxbow lakes–an habitat favorable for bass, crappie, and sunfish.  The changing river patterns of the Pleistocene undoubtedly caused fish assemblages to change in abundance and variety of species.  It would be interesting if we could go back in time and sample rivers at intervals of a century for tens of thousands of years.  Probably, no 2 samples would show any similarity.  Changing conditions created favorable habitat for some species, but chance colonization probably played an important role in fish species abundance and composition.  The prevalence of gulf menhaden in the Alabama River is an example of a chance colonization when a species just happens to find new habitat.

Reference:

Haley, T. Heath; and Carol Johnston

“Fish Assemblage on Sand/Gravel Bar Habitat in the Alabama River, Alabama”

Southeastern Naturalist 13 (3) 2014

*****

I just began subscribing to the Southeastern Naturalist.  I realized I was interested in every article this journal publishes, and the material will provide endless speculative fodder for my blog.  I do have 1 complaint about this journal, however.  I’ve noticed a fetish for complex statistics in many of the articles that get published.  I believe charts of raw data would be much more interesting than complex statistics understood by few other than statisticians.  For example the above referenced article becomes weighted down with a statistical analysis when charts of just the raw data would have been more interesting.  I would like to have seen charts of every species of fish surveyed along with how many, when, and where each specimen was caught.  This chart could have been compared with a chart of species sampled from historical collections.  Everybody reading the article would have understood this data, but I doubt anybody, other than the authors, fully understood their statistical analysis.

 

How Far South did Polar Bears (Ursus maritimus) Range During the Ice Age?

February 21, 2015

Almost the entire present day range of the polar bear was uninhabitable for this species during most of the Ice Age.  The ice was too thick then, even for species adapted to arctic conditions.  Polar bear ranges shifted south.  Favorable habitat existed between the mile high Laurentide Ice Sheet and the Atlantic Ocean, and polar bears likely wandered along a strip of the Atlantic Seaboard now submerged by rising sea level.  I hypothesize they occurred as far south as what today is the continental shelf off the coast of South Carolina.

Map of North America during the Last Glacial Maximum.  Polar bears probably ranged on a narrow strip of the Atlantic Seaboard off the coast of what’s now Nova Scotia and Maine to as far south as what today is South Carolina during the height of the Ice Age.  Note the narrow strip of land between the ice sheet and the ocean in the northeast.  Dry land extended well off the modern day shoreline.  During warm climate pulses, icebergs broke off and drifted as far south as off the coast of Pleistocene South Carolina.

The ranges of walruses and 5 species of seals were also shifted south by the massive ice sheet.  All of these marine mammals lived on the narrow strip of land between the ice sheet and the ocean from what today is Nova Scotia south to New Jersey where the ice sheet terminated.  Fossils of 3 species have been found even further south near the South Carolina coast–walrus (Odobenus rosmarus), gray seal (Halichoreus grypus), and bearded seal (Erignathus barbatus).  It should not be surprising, if some day, a fossil hunter finds the remains of Pleistocene age harbor seal (Phoca vitulina) or harp seals (Pagophilus groenlandicus) farther south than their present day ranges.  (Harbor seals were probably more abundant off Pleistocene South Carolina’s coast than walruses, despite the absence of the former in the local fossil record.)  Predators follow prey.  Polar bears feed upon walruses, seals, washed up whale carcasses, sea birds, sea bird eggs, and fish.  All of these resources would have been abundant even further south than Pleistocene South Carolina.  One particular rocky outcropping that would have provided ideal nesting habitat for millions of sea birds existed on the Pleistocene coast of South Carolina.  (See: https://markgelbart.wordpress.com/2014/08/14/bulls-scarp/).  I’m certain this site attracted polar bears.  I think the presence of prey species such as walruses and seals in the fossil record of South Carolina means the presence of polar bears can be inferred.

Video of polar bear slaughtering a walrus.  I doubt ice ever grew this thick in South Carolina, even during the Ice Age.  Walruses were not confined to cold regions prior to the  catastrophic increase in the population of humans.

Predators are less common in the environment than prey animals, and therefore are less likely to be preserved as fossil remains.  Moreover, the southernmost range of the polar bear was restricted to the South Carolina continental shelf, an area now deeply submerged under ocean water.  This explains why polar bear fossil remains have yet to be found in this region.  Polar bear fossil remains dating to the Pleistocene are rare worldwide because much of their habitat during Ice Ages is now submerged.  Some day, a trawler dragging the sea bottom may luckily snag a polar bear specimen well south of the species’ present day range.

Polar bears did occur within historical times at least as far south as Great Breton, Nova Scotia.  In 1534 Jacques Cartier and his French crew of explorers encountered a polar bear on Funk Island, located near the mouth of the St. Lawrence River.  They had embarked on the island to collect now extinct great auks (Pinguinus impenns) and other sea birds for the ship’s larder.  The polar bear was also on the island to feast upon sea birds.  (Bulls scarp, the now submerged rocky outcropping off the coast of South Carolina, would have offered similar habitat.)  The surprised bear jumped back into the ocean.  But the following day, the Frenchmen spotted the bear again.  They manned a longboat, pursued the swimming bear, and dispatched it.  Captain Cartier pronounced the meat as good as that of a “2 year old heifer.”  Fresh meat was a treat after a long sea journey’s fare of heavily salted protein.

Pleistocene polar bears probably didn’t wander far inland.  A report of a polar bear fossil found in Breck Smith Cave, Kentucky about 100 years ago is likely a misidentification, and unfortunately that specimen has been lost.  Polar bears are adapted to hunting seals and scavenging whales, so their range hugged the shoreline where they could find their favorite foods.

Just contemplate the diversity of bears that existed in southeastern North America during the Pleistocene.  15,000 years ago, a paleoindian journeying from west Texas or Kentucky to the Atlantic Coast could have possibly encountered grizzly (Ursus arctos), black (Ursus americanus), spectacled (Tremarctos floridanus), giant short-faced (Arctodus simus) and polar bears. I’m 52 years old and have never seen a live wild bear of any kind in person.  The loss of wild lands that support this diversity of bears saddens me.

The Giant Short-Faced Bear (Artodus simus) was not as Bizarre as Originally Thought

February 17, 2015

Scientists first described the giant short-faced bear as an unusually long-limbed bruin with a shortened catlike face.  Some proposed this species outran prey, much like a cheetah does.  However, later studies determined it was not a particularly fast runner but was instead built for endurance.  Nevertheless, these descriptions suggested a very bizarre kind of bear.  But now, the most recent and thorough study of the short-faced bear’s anatomy upends much of what was previously thought about this bear. Paleontologists, led by Borja Figuerida, compared skeletons of the giant short-faced bear with those of 56 different species of carnivores including all living species of bear.  In all they looked at 411 specimens.  They believe the giant short-faced bear did not sport much of a different appearance than any living species of bear, though it was very large. The legs were not unusually long.  They claim the assumption of a bear with unusually long limbs was a misinterpretation based on an optical illusion.  Bears have short backs compared to big cats and wolves, leading previous researchers to overestimate the length of this bear’s legs.  Moreover, its snout was no shorter in proportion than those of the Malaysian sun bear (Helarctos malayanus) and the spectacled bear (Tremarctos ornatus).

The giant short-faced bear’s legs were not as long as typically depicted in illustrations.

Sitting sun bear.jpg

Malayan sun bear (Helarctos malayanus).  A study suggests the proportions of the giant short-faced bear’s snout were no different from that of this endangered species.

The frequency of supersized individuals in the population of giant short-faced bears surprised the scientists involved in this study.  The male bear skeletons they studied came from individuals that frequently reached an estimated weight of 2000 pounds.  (Specimens from Alaska and the Yukon tended to be the largest.)  There was great sexual dimorphism–females averaged just an estimated 400-800 pounds.  B. Figuerida and his co-researchers do not think the giant short-faced bear was an hypercarnivore that chased down prey or lived entirely from scavenging.  Instead, they believe it was a generalist feeder like most modern day bears.  This giant bear ate any available plant and animal material in its environment.  Nevertheless, they probably did often scavenge carcasses.  Saber-tooth and scimitar-tooth cats had weak jaw muscles and likely ate just the organs and soft muscle tissues, leaving quite a lot of meat for a huge hungry bear to consume.

Reference: Figuerida, Borja; Juan Perez-Claros, and Vanessa Torregruz

“Demythologizing Arctodus simus, the “Short-Faced” Long Legged and Predaceous Bear that never was”

Journal of Vertebrate Paleontology 30 (1) 2010

Add Mixotoxodons (Mixotoxodon cf larensis) to the list of Mammals that Occupied Southeastern North America during the Pleistocene

February 12, 2015

Toxodons and the closely related mixotoxodons originally evolved on the South American continent.  They are classified as notoungulates– primitive hooved animals that resembled the ancient ancestors of cattle, antelope, deer, horses, hogs, etc.  Artistic representations of notonungulates are reminiscent of beasts known from the Eocene and Oligocene.  Mixotoxodons weighed a little over a ton, ate plant material, and looked kind of like a rhino or hippo.

Mixotoxodon.jpg

Mixotoxodons were notoungulates, a group of primitive ungulates that evolved in isolation from all other hooved animals when South America was an island continent.

The notoungulates were thought to be restricted to tropical climates.  Until 2004 fossil remains were not known north of Guatemala. But that year, mixotoxodon fossils were excavated from 2 sites in Mexico–Hihiuctilan, Michoacán and La Estribera, Veracruz.  This was a range extension of 900 miles north but still well within the tropics.  During 2012 a mixotoxodon tooth (un upper 3rd left molar) was discovered along Cypress Creek, Harris County, Texas–a further range extension of 800 miles north.

State of Michoacán within Mexico

Michoacán Province in Mexico.  Mixotoxodon fossils were found here for the first time about a decade ago.  At the time they were the northernmost known fossils of this species.

Map of Texas highlighting Harris County

Harris County, Texas.  A fossil tooth of a mixotoxodon was found here just a few years ago.  Now this site is the northernmost known locality where toxodons once lived.

Harris County, Texas borders the modern day temperate and subtropical zone.  The mixotoxodon tooth couldn’t be directly dated but 2 pieces of fossil oak wood located 10 meters upstream from the specimen were dated and yielded ages of 17,080 years BP and 23,780 years BP.  The tooth is believed to be from the same geological strata as the fossil wood.  If the tooth does belong within this time span, than mixotoxodons occurred in southeast Texas during the Last Glacial Maximum, the coldest phase of the last Ice Age.  However, climate in this region then was likely similar to that of the present day, though summers were probably a bit cooler and winters a little warmer.  The modern day oceanic gulf stream that moderates present day climates in eastern North America didn’t exist during the coldest phases of the Ice Age.  Instead, tropically heated water remained near the equator and may have upwelled into the Gulf of Mexico at times.  When this warm water circulated just a little north, it may have reduced the intensity and frequency of frosts near the southern Atlantic coast and around the coast along the Gulf of Mexico.  The extent of warm water upwelling in this region likely fluctuated cyclically, resulting in decades of warm winters with few local frosts alternating with decades when frosts occurred more often because the warm waters pooled near the equator and away from nearby coasts.

I see no ecological reason why mixotoxodons couldn’t have occurred further east in North America.  Coastal savannah interspersed with open woodlands along waterways stretched from Mexico to Florida.  The Harris County mixotoxodon tooth was found right in the middle of where this type of environment existed.  Why isn’t there more evidence of mixotoxodons in North America, especially from the abundant fossil sites in Florida?  The fossil record is not a complete accounting of every organism that ever lived in a location, perhaps explaining the absence of this species.  Collared peccaries and giant short-faced bears were unknown from Florida’s fossil record until just a few years ago, so maybe some day someone will find a mixotoxodon fossil elsewhere in the south.  Alternatively, the Harris County specimen may represent a very temporary range extension of a cold sensitive species that occurred during a few decades or centuries when an upwelling of tropically warmed water resulted in a brief cycle of locally frost free winters.

Below is a list of currently known land mammals, weighing over 100 pounds, that lived in southeastern North America during the late Pleistocene.

1. Mixotoxodon (Mixotoxodon cf larensis)–from just 1 tooth certain species identification is not possible

2. Columbian mammoth (Mammuthus colombi)

3. woolly mammoth (Mammuthus primigenius)–not known farther south than Virginia

4. mastodon (Mammut americanum)

5. gompothere (Cuverionius tropicalis)

6. upland bison (Bison antiquus)

7. long-horned bison (Bison latifrons)

8. helmeted musk ox (Bootherium bombifrons)

9. collared peccary (Pecari tajadu)

10. long-nosed peccary (Mylohyus nasatus)

11. flat-headed peccary (Platygonus compressus)

13. stout-legged llama (Paleolama mirifica)

14. long -necked llama (Hemiauchenia macrophela)

15. stag-moose (Cervalces scotti)–from a site in South Carolina and a site in Mississippi

16. elk (Cervus canadensis)

17. caribou (Rangifer tarandus)

18. white tailed deer (Odocoilus virginiana)

19. horse (Equus ?)

20. half-ass (Equus?)

21. Vero tapir (Tapirus veroensis)

22. giant ground sloth (Eremotherium laurillardi)

23. Harlan’s ground sloth (Paramylodon harlani)

24. Jefferson’s ground sloth (Megalonyx jeffersonii)

25. pampathere (Holmesima septentrionalis)

26. glyptodont (Glyptodont floridanum)

27. giant beaver (Casteroides dilophidus)

28. capybara (Hydrochoreus)

29. another species of capybara (Neochoreus)

30. giant short-faced bear (Arctodus simus)

31. spectacled bear (Tremarctos floridanus)

32. black bear (Ursus americanus)

33. dire wolf (Canis dirus)

34. saber-tooth (Smilodon fatalis)

35. scimitar-tooth (Dinobastis serum)

36. giant lion (Panthera atrox)

37. jaguar (Panthera onca)

38. cougar (Puma concolor)

39. human (Homo sapiens)

References:

Lundelius, Ernest; et. al

“The First Occurrence of a Toxodont (Mammalia; Notoungulata) in the U.S.”

Journal of Vertebrate Paleontology 33 (1) Jan 2013

De la Rosa, Ruben; Jose Guzman-Gutierrez and Carlos Hurtado Menoza

“A New Occurrence of Toxodonts in the Pleistocene of Mexico”

Current Research in the Pleistocene 2011

 

Scientists give Religion too much Respect

February 9, 2015

Warning: I’m standing on my soap box today.  This blog article might offend Christians, Jews, Muslims, mentally disabled people, the LGBT community, and Native Americans.

I was having a hard time understanding a recent news report on National Public Radio.  The story was about opposition to the execution of a mentally disabled man in Georgia.  I couldn’t figure out what the hell mentally disabled meant.  When I think of the disabled, I think of someone like my wife who can’t walk.  Finally, I remembered mentally disabled was the politically correct term for retarded.  Politically correct fascists have declared the word, retarded, to be offensive and derogatory.  I don’t understand how calling someone mentally disabled could be any less offensive than referring to them as retarded.  Public figures are so afraid now of offending certain groups of people they use confusing terms that just muddy communication.  Another example is the ban of the word, queer.  Instead, the accepted term is LGBT, even though that isn’t any more clear than using the word, queer.  A person listening to a  news report about LGBT people doesn’t know whether the reporter means the L, the G, the B, or the T.  Aren’t the L and the G redundant anyway?  Clarity in language doesn’t matter anymore, just as long as no one is offended.

Scientists are usually among the most enlightened members of society and fear offending people more than most.  This is a shame.  Half of Americans reject the fundamental basis of biological science because it interferes with the narrative of their Sunday school bible stories.  I wish that just once, a prominent scientist would stand up and publicly declare that the bible is full of shit.  People believe the bible is a holy sacred work.  It is not.  It was written thousands of years ago by ignorant fanatics who  favored slavery, oppression of women, and the execution of misbehaving children among many other crimes against humanity.  The God of the bible is pro genocide.  Yes, God told the Israelites to kill every man, woman, child, baby, farm animal, and pet in the town of Jericho.  Christians claim Jesus repudiated the excesses of the Old Testament, but this isn’t true.  In Mathew 5:17 Jesus endorsed all of the Old Testament atrocities when he said, “Do not think I have come to destroy the Law or the Prophets.  I did not come to destroy but to fulfill.”

Tissot The Taking of Jericho.jpg

After the walls of Jericho tumbled down, the Israelites committed genocide, slaughtering men, women, children, farm animals, and pets; all according to God’s orders.  The bible is full of shit like this.  Anyone who considers the bible to be a “holy” book hasn’t really read it.  The bible is for morons.

Mohammed, the founder of Islam, was a mass murderer, an armed robber, a bigamist, and a pedophile.  The Islamic religion was forced upon the Middle East at the point of a sword, just as Christianity was forced upon Europe.  During the Age of Reason secular forces gained control over religion in most of Europe, allowing science and modern progressive values to advance.  If not for this power transfer, western civilization would still be oppressed by a theocracy, not unlike that seen in the Arab region today. Laws in Western countries are no longer written by clerics…for the most part.

Here is an exception. The U.S. Congress passed the Native American Graves and Repatriation Act–a law influenced by religious beliefs.  Indian skeletons and associated artifacts found on government land are supposed to be reburied, according to the stupid superstitions of the tribe that has the closest cultural affiliation to them. Politicians think it is important to show respect for Indian traditions.  I think this law is an impediment to archaeology and historical knowledge.  Scientific data can be lost because the religious beliefs of some idiotic Indians might be offended.

The conflict between science and Native American Indian religious beliefs became apparent in the case of Kennewick man.  The skeleton of a 9500 year old man was discovered along the Columbia River in Washington.  Specimens of humans from this time period in North America are incredibly rare.  Kennewick man was almost a 1 of kind type of discovery, yet the Army Corps of Engineers planned to give the skeleton to a local Indian tribe that was going to bury him without study.  Fortunately, a group of scientists pooled their money together and sued the government for access to the specimen, and several judges ruled in their favor.  Local Indians could not prove they were culturally associated with Kennewick man.  Bill Clinton, the rapist president, ordered the Army Corps of Engineers to bury the site where Kennewick man was found, so scientists couldn’t study the archaeological context, but at least they are allowed to study the skeleton.

Reconstruction of Kennewick Man’s face.  Idiotic Indians wanted to rebury the skeletal remains and prevent archaeologists from studying this extremely rare specimen.

Some Indians believe skeletons are sacred spiritual remains.  This is a really stupid belief.  There probably is no such thing as a spirit, and even if there is, I doubt a spirit would hang around its lifeless remains.  Shouldn’t a spirit be gone to the spirit world?  Physical remains should be unimportant, if there is such a thing as a spirit world.  There just is no logic in the belief that a corpse is sacred.

Alcohol abuse causes 12% of Native American fatalities–4 times the rate of the general population.  Indian babies are born with fetal alcohol spectrum disorder at 7 times the rate of the general population.  39% of Native American women suffer spousal abuse–by far the highest of any ethnic group.  The prevalence of alcoholic wife-beating losers in the Native American population is a  much more serious problem than whether some ancient bones get reburied or whether the Washington Redskins change their name.  Indian protestors need to change their priorities to focus on problems that really matter in this world, rather than the imaginary spirit world.

Native American protester outside Washington's game in Dallas in 2013.

If Indians are offended by the Washington Redskins, I’ve got the perfect solution for them…Don’t go to any Redskin games, you stupid jerks!

An Update on Vero Beach Man

February 5, 2015

I wrote about the Vero Beach mammoth engraving in February of 2012 (See: https://markgelbart.wordpress.com/2012/02/19/the-vero-beach-mammoth-engraving/).  A fossil collector found the bone of an unidentified species of megafauna engraved with the likeness of a mammoth.  This rare artifact was discovered at the Vero Beach fossil site in Florida.  This site was first excavated about 100 years ago.  Human remains were found in the same strata as the remains of extinct Pleistocene megafauna including sabertooth, mastodon, llama, tapir, etc.  The leading archaeologist of the day insisted humans didn’t colonize North America until after the Pleistocene megafauna became extinct.  He believed Indians buried dead members of their tribe, thus explaining why these particular human remains appeared to be in the same strata as the extinct mammals. Years later, overwhelming evidence showed that humans did overlap in time with North America’s extinct megafauna.  However, I had read that no scientist had been able to test the Vero Beach remains because they had been lost.  Either the Vero Beach remains were rediscovered or they were never lost because I came across a recent study in the Journal of Vertebrate Paleontology that did involve testing these specimens.

Paleoindians hunting.  An analysis of rare earth element concentrations confirms human fossils found at the Vero Beach Site were the same age as the megafauna fossils, solving a century old controversy.

The scientists who published this study (referenced below) analyzed the concentrations of rare earth elements to determine humans lived at Vero Beach at the same time as the extinct Pleistocene megafauna.  (Vero Beach was far inland then and not actually a beach.)  The concentration of rare earth elements in ground water varies over time.  Organisms drink this water and the amount of rare earth elements in their bone matches that of the environment at the time they lived.  The human remains had rare earth element concentrations in the same ratio as the Pleistocene mammals.  These levels are higher than are found in modern Floridian mammals.  This evidence resolves a century old scientific dispute, though few modern scientists doubted the Indian remains dated to the Pleistocene.

Reference:

Macfadden, Bruce; and Barbara Purdy, F. Church, and Thomas Stafford

“Humans were contemporaneous with Late Pleistocene Mammals in Florida: Evidence from Rare Earth Elemental Analysis”

Journal of Vertebrate Paleontology 32 (3) May 2012

Pliocene and Pleistocene Gulls (Laridae) of the North Atlantic

February 2, 2015

Ring-billed gulls (Larus delawarensis) often hover over grocery store parking lots in Augusta, Georgia.  The wide open spaces and spilled junk food attract them to these man-made habitats.  They appreciate all the obese Americans who can’t wait to get home to stuff their faces.   The gulls scavenge smashed corn chips and cheese crackers off the pavement.  Gulls perform a valuable service by cleaning up schools of dead fish and mountains of human garbage.  This helps reduce the spread of toxic bacteria in the environment.

Most people think of sea gulls as shore birds, but ring-billed gulls are quite common inland and some may never see the ocean.  Other species of gulls, such as Bonaparte’s (L. philadelphia), follow rivers upstream and can also be found inland.

Ring-billed Gull Photo

Ring-billed gulls are commonly found in parking lots and landfills during winter time in Georgia.

Several species of gulls, including the laughing (L. atricilla) and Franklin’s (L. pipiyan), are primarily shore dwellers and do nest off the coast of southeastern states.  The laughing gull prefers to nest in beach thickets, though many species of gulls and terns will lay their eggs in the open.  Sea gull nestlings are mobile shortly after hatching, so they can avoid predation at an early age.

There are at least 5 species of gulls that have a polar distribution.  I hypothesize some or all of these species ranged as far south as what today is South Carolina and Georgia during the Ice Ages.  Glaucous gulls (L. hyperboreus) are a polar species that prefers nesting on rocky sea cliffs where they can feast upon nestlings of other cliff-nesting sea birds.  Today, there are no sea cliffs off the coast of southern states.  But for about 40,000 years, there was an enormous sea cliff, known as Bulls Scarp, off the coast of South Carolina where glaucous gulls could have nested. (See: https://markgelbart.wordpress.com/2014/08/14/bulls-scarp/)  About 13,000 years ago, rising sea level submerged these cliffs, and glaucous gulls likely left the region then.

Adult breeding

Glaucous gull.  This is a polar species occasionally found as far south as Virginia.  During the Ice Age it likely ranged much farther south than it does today and it probably nested on Bulls Scarp, a now submerged sea cliff.

Some paleontologists puzzle over how rare gulls are in Pleistocene fossil sites.  The La Brea tar pits preserved the bones of more than an hundred species of birds but have yielded just 1 gull specimen.  I think I know why gull remains appear so rarely in Pleistocene fossil sites.  Pleistocene shorelines are submerged today. Most fossil evidence of gulls is deep beneath the surface of the ocean.

I am unaware of any extinct species of Pleistocene gulls.  The species that are alive today are the same as the ones that lived during the Pleistocene.  However, there were 2 species of Pliocene gulls that are now extinct.  Fossils of L. lacus and L. perpetis were among bird fossils found at a site on the Florida gulf coast.  The fossils are estimated to be between 2 and 2.4 million years old.  Apparently, all the birds found at this site were killed by a toxic red tide.  (I may do a blog article about this site, if I can ever obtain a reasonably priced copy of the scientific paper documenting it.)

The Larus genus originated in the North Atlantic polar region about 20 million years ago.  Sea gulls have dispersed and have an almost worldwide distribution today.