Archive for the ‘herpetology’ Category

Giant Sea Snakes of the Georgia Eocene

May 6, 2021

The entire coastal plain of southeastern North America and all of Florida were below sea level until about 32 million years ago. Strong currents carried sediment into shallow coastal waters, and some sediments eventually became kaolin clay, now mined in Wilkinson County, Georgia. The clay preserves fossils of the Eocene Age including shark’s teeth, sawfish and ray bones, and the remains of primitive whales. Miners excavating clay also find vertebrae from an enormous extinct sea snake given the scientific name, Palaeophis virginianus. Scientists compared the vertebrae of Palaeophis with modern species of snakes and estimated this extinct species reached a length of at least 17 feet long.

Artist’s rendition of an extinct giant sea snake (Palaeophis).. Image from the Prehistoric Animals Twitter Page..
Fossil vertebrae of an extinct giant sea snake. Image from an anonymous post on the Fossil Forum.

Palaeophis was not closely related to modern day sea snakes. Scientists don’t know much about it, but they think it was an ambush predator, like a modern day anaconda, that preyed on other animals in shallow coastal waters. There was more than 1 species of Palaeophis sea snakes alive during the Eocene (55 million years BP-33 Million years BP), and they had a worldwide distribution, but today they are extinct and they left no descendants. Palaeophis fossils found in south Georgia are thought to date to ~34 million years ago, close to the end of the Eocene.

Reference:

Calvert, C; A. Mead, and D. Parmley

“Size Estimate of Extinct Aquatic Snakes from the Eocene of Central Georgia”

Georgia Journal of Science 79 (1) Article 22 2021

The Former Abundance of Green Sea Turtles (Chelonia mydas)

April 22, 2021

Our ancestors didn’t appreciate wildlife. For them wild animals were considered either a pest or a resource to be ruthlessly exploited until that particular species was annihilated. I came across an article entitled “Turtling in Florida” written during 1890 and learned how abundant green sea turtles formerly were. According to the author, slaughtering turtles was great sport. So many turtles populated some lagoons that a man could theoretically walk from 1 side to the other by walking on their backs. Turtle stampedes endangered men’s lives. Sea turtles crawling on beaches to lay their eggs could become frightened by men hunting them and their eggs, and hundreds of 800 pound panicking turtles could crush men too slow to get out of their way.

Of course, man is much more dangerous to sea turtles than they are to us. In North America before man invaded the continent, adult sea turtles had few enemies–bears on beaches and tiger sharks in the sea. But man killed too many turtles and gathered too many eggs, and now green sea turtles are endangered. Several methods were formerly used to catch green sea turtles. Some men used nets, though in south Florida, they encountered problems with sharks and sawfish that often destroyed the nets. (Both sawfish and sharks are much more rare now than they were in 1890.) Other turtle-hunters used harpoons in a process called “pegging.” The harpoons were designed to just barely penetrate the shell, so the turtle could be reeled in and kept alive for as long as possible. Some Seminole Indians actually dove to the bottom of the sea, grabbed the turtles, wrestled them to the surface, lassoed them, and pulled them onto the boat. The most common method of hunting sea turtles was to simply sneak up on them while they were laying eggs on the beach, and turn them over. Sea turtles are helpless when on their backs. This method could be hazardous. The turtle-hunters could run into a bear in the dark (turtles lay their eggs at night). The article reports 1 expedition shooting and killing 5 bears on a night of turtle-hunting, and they could have killed more, if the sand flies hadn’t been driving them crazy. There was also the possibility of getting crushed in the aforementioned turtle stampedes.

Green sea turtles inhabit shallow coastal waters where they feed upon sea weed. They nest on tropical beaches.
Green sea turtle range map. They often stray far from where they nest.
Green sea turtles are considered a delicacy due to their vegetarian diet. They were formerly abundant, but overhunting by men has greatly reduced their numbers.
Aborigines can still get away with hunting sea turtles.

Green sea turtles were a popular delicacy over 100 years ago. Adult green sea turtles live on a diet of seaweed, giving their flesh a delicious flavor, according to old time accounts. People enjoyed eating turtle eggs too. No matter how long a turtle egg is cooked, the white part never solidifies. The eggs must have made cakes moist when they were used as an ingredient. The turtle shells were used to manufacture women’s jewelry as well. Now, green sea turtle populations are low and even raising them on farms for food is illegal. Nevertheless, various aboriginal groups around the world still hunt them and collect their eggs.

Reference:

Murphy, J.M.

“Turtling in Florida” from

Tales of Old Florida

Castle Books 1987

Tegu Lizards (Salvator merianae) are Invading Georgia

March 18, 2021

You know who I hate (besides Trumpanzees)?  I hate the hypocritical sadistic do-gooders who hunt Burmese pythons in south Florida.  For generations the ecosystem there has been out of whack because large predators have been reduced or exterminated.  Finally, a new large predator has been introduced (though accidentally), but these stupid jerks are wiping them out too.  Burmese pythons can help control the overpopulation of raccoons and wild hogs in South Florida that destroy eggs of endangered species of turtles.  The snake-killers refuse to acknowledge this benefit, and instead they are doing their best to eliminate another large predator that simply is substituting for the wolves and cougars that humans also try to wipe out.  I hope these assholes fail.  I root for the snake.  In fact I hope 1 day a Burmese python squeezes the life out of a snake-killing hypocrite who is trying to exterminate them. I would celebrate the irony.  I’d love to write the headline “Burmese Python Euthanizes Human.”

The Argentine black and white tegu is another newly colonizing species (which alarmists call invasive) that has wildlife biologists hyperventilating.  This species is native to South America and a popular pet among reptile-lovers.  However, they grow to 3 feet long and reach weights of 15 pounds.  Pet-owners get tired of taking care of such a large lizard, and they release them into the wild.  Tegus established a breeding population in south central Florida where they’ve been munching down on alligator and turtle eggs for 20 years.  Over the past 3 years there have been over 50 sightings of tegus in Georgia, mostly in Toombs and Tatnall Counties.  To determine whether a breeding population exists in south Georgia, scientists conducted a study.  They set out 75 live traps in 3 different locations in those 2 counties for a couple of months.  The scientists caught 2 breeding age females in all that time, indicating to me that they are still uncommon but present.  The authors of the paper wrote they “euthanized” the lizards by shooting them with a .22 rifle.  I hate the word, euthanize, because it makes killing a creature sound sanitized.

Argentine Black And White Giant Tegu, Tupinambis Merianae Or.. Stock Photo, Picture And Royalty Free Image. Image 94513894.

Black and white tegu lizards, native to Argentina and other South American countries, have established a population in Florida and are invading Georgia.  Do-gooder assholes want to wipe them out, but I think for the most part they are harmless.

Native range map for black and white Argentine tegus.

Verified and unverified sightings of tegu lizards in Georgia + trapping sites of the below referenced study.  .

Map of verified and unverified sightings of tegus in Georgia and Florida.  Surprisingly, some of them have been from quite far north in Georgia.  Tegus are partially warm-blooded and can dig burrows, helping them survive in cooler climates.  Map also from the below referenced study.

Most of Georgia is ideal habitat for tegu lizards.  They are partially warm-blooded and can did burrows to escape cold and hot weather.  Females lay about 30 eggs, and the young become full grown and sexually mature in 2 years.  They are also omnivorous, eating insects, other arthropods, small animals, eggs, and fruit.  The stomach contents of 7 tegu lizards trapped in Georgia included blackberry, strawberry, insects, other arthropods, crayfish, wood frogs, and a toad.  This list hardly sounds like an animal that is destabilizing the environment.  Wildlife biologists are concerned the lizards might eat eggs of the endangered gopher tortoise, and they have been found in gopher tortoise burrows, but native raccoons are much more abundant and have hardier appetites.  If gopher tortoises can co-occur with raccoon predation, they can endure the impact of a few lizards.  Unlike Burmese pythons, tegu lizards are much more vulnerable to native predators.  I’m sure bobcats, coyotes, hawks, owls, and snakes can control their numbers.

Reference:

Haro, D.; et. al.

“Evidence for an Established Population of Tegu Lizards (Salvatore merianae) in Southeastern Georgia”

Southeastern Naturalist (19) 4 2020

Deinosuchus rugosus Given a New Scientific Name–D. Schwimmeri

March 11, 2021

My wife took a geology class 40 years ago at Columbus State University, and it was taught by David Schwimmer who now has the honor of having an extinct species of crocodylian named after him.  The paleontologists who named the species after him consider it a new species (or species novum), but it is really not a species new to science.  The first scientist to name the species gave it the scientific name Deinosuchus rugosus.  However, the type specimen used to name the species is not considered diagnostic as it could represent any of the 3 known species of Deinosuchus.  So they used other more complete specimens to describe the anatomy of the species, and they decided to give it the scientific name D. schwimmeri after David Schwimmer who published a book about Deinosuchus during 2002.

Species named after Columbus State professor David Schwimmer | Columbus  Ledger-Enquirer

David Schwimmer of Columbus State University, my wife’s college geology professor.  He wrote a book about Deinosuchus, a giant extinct alligatoroid.  Deinosuchus rugosus has been renamed in his honor as D. schwimmeri.

Feces, Bite Marks Flesh Out Giant Dino-Eating Crocs

Deinosuchus preyed on tyrannosaurs and other dinosaurs.

Fossil evidence suggests there were 3 species of Deinosuchus living in North America during the late Cretaceous from ~80 million years BP-~73 million years BP.  The North American continent was split into 3 land masses by the Western Interior Sea then.  D. schwimmeri is the species that lived on the eastern part of North America, and D. riograndis lived on the western part.  D. hatcheri, a poorly known species, also lived on the western part.  D. riograndis tended to grow larger than D. schwimmeri.  All species of Deinosuchus were 36 foot long 12,000 pound monsters that ate Tyrannosaurus rex for breakfast.  Fossil specimens of Deinosuchus have been found in Georgia, New Jersey, North Carolina, Alabama, Mississippi, Texas, Utah, Nebraska, Wyoming, Montana, and Mexico.  Scientists aren’t sure how Deinosuchus came to live on both sides of the Western Interior Sea.  They likely were saltwater tolerant and perhaps island-hopped from 1 side to the other.  Alternatively, when the Western Interior Sea flooded the Great Plains, the 2 founding populations were separated.

Deinosuchus is considered an alligatoroid or in other words they are thought to have been more closely related to alligators than crocodiles.  They were not ancestral to modern alligators.  Instead they were related to the direct ancestor of modern day alligators.

References:

Gossette, A; and C. Bracho

“A Systematic Review of the Giant Alligatoroids Deinosuchus from the Cretaceous of North America and its Implications for the Relationships at the Root of Crocodylia”

Journal of Vertebrate Paleontology 40 (1) 2020

Schwimmer, David

King of the Crocodylians: The Paleobiology of Deinosuchus

Indiana University Press 2002

 

Pack-Hunting Cuban Boas (Chilabothrus angulifer)

January 8, 2021

Cuban boas work together when they hunt Jamaican fruit bats.  They each take a strategic position near cave entrances to increase the chances they will successfully ambush a bat.  Scientists believe the gauntlet they create requires active coordination.  Otherwise, they would all be laying on top of each other in the best strategic location, and bats could just avoid that area.

Found: Snakes That Hunt in Packs - Atlas Obscura

Cuban boas hunt in packs.  They coordinate their positions near cave entrances and ambush Jamaican fruit bats.  They kill their prey using constriction.

There are 12 species of large boas in the Chilabothrus genus, but each Caribbean Island usually hosts just 1 or at most 2 species.  Each island was colonized by 1 species of boa that drifted there on floating vegetation millions of years ago.  Once that species became established on the island, they precluded other species arriving on floating vegetation from colonizing the island.  Genetic evidence suggests Cuban boas diverged from their closest relative 17-20 million years ago, and since then they have prevented other boa species from establishing a population there.

Cuban boas were part of an unique ecosystem found on Caribbean Islands until it was disrupted by man thousands of years ago.  Cuban boas formerly grew up to 27 feet long, but now individuals larger than 9 feet long are rare.  During the Pleistocene they hunted hutias (large 15 pound rodents), birds, and lizards. They still hunt these species, but larger species of hutias became extinct after man colonized the islands.  Cuban boas may have also hunted the now extinct dwarf ground sloths that roamed the island then.  Cuban boas shared the environment with other predators including Cuban crocodiles, an extinct species of 3 foot tall flightless owl, and large extinct subspecies of barn owls and black hawks.  Since man arrived on Cuba, both boas and crocodiles have evolved to smaller sizes.

The 2 largest predators on Cuba have evolved to a smaller size, since man colonized the island.  Image from the below reference by Rodrigues-Cabrera.

References:

Dinets, Vladimir

“Coordinated Hunting in Cuban Boas”

Animal Behavior and Cognition 4 (1) Feb 2017

Rodrigues-Cabrera, T.; and T. Javier Torres

“An Overview of the Past, Present, and Future of the Cuban Boa, Chilabothrus angulifer, (Squamata: Boidae): A Top Terrestrial Predator on an Oceanic Island”

Reptiles and Amphibians Journal December 2016

A Pre-Historic Sloth-Eating Monster

September 7, 2020

A real monster inhabited the wetlands of South America during the Miocene between 20 million years BP-6 million years BP.  Purussaurus brasiliensis, an extinct 34 foot long caiman, preyed on everything from fish to giant ground sloths.  No complete skeleton of this giant caiman has ever been found, but the size was estimated from several skulls.  It weighed over 10,000 lbs. and was more than a match for any beast living in South America during the time it existed. The few marsupial carnivores that lived then didn’t offer much competition.  It was almost as large as Deinosuchus rugosus, a 39 foot long crocodylian that ate tyrannosaurs during the late Cretaceous.

Purussaurus

Purussaurus was a 36 foot long caiman that lived in South America during the Miocene and preyed on giant ground sloths.

Illustration of purussaurus preying upon a ground sloth.

Recently, scientists examined a fossil arm bone of a giant ground sloth (Pseudoprepothenum) and determined it had 46 tooth marks made by a purussaurus.  At least 6 other species of caiman and crocodiles lived then in South America, but purussaurus was the only species large enough to attack and subdue a giant ground sloth, though this particular specimen was estimated to weigh about 100 lbs. The sloth specimen was found near Iquitos, Peru along with many other fossils of fish, reptiles, and mammals.

Reference:

Pujos, F. and R. Salos-Gismonde

“Predation of the Giant Miocene Caiman Purussaurus on a Mylondontid Ground Sloth in the Wetlands of Proto-Amazonia”

Biology Letters 2020

Another Pleistocene Survivor–The Bird-Voiced Tree Frog (Hyla avivoca)

June 11, 2020

I discovered a new creature in my yard.  Green tree frogs (Hyla cinerea) are abundant here and often sneak into our house, but I was unaware that my yard is also home to the bird-voiced tree frog until I saw the below specimen in my cat’s water dish.  I saw another one a few weeks later.  Most of the time they stay in the tree tops and that is probably why I’d never seen one before, though maybe they had a good few years of reproduction and are on the increase at my locality.  Bird-voiced tree frogs can be green or gray, depending upon the temperature.

Bird-voiced tree frog.

Video of a bird-voiced tree frog call.

Bird-voiced tree frogs have an interesting range distribution.  They likely diverged from their closest living relatives in the Mississippi River Valley and dispersed across Alabama and Georgia.  Their preferred habitat is swampy bottomland forest, and during warm climate cycles this type of habitat is common in the southeast.  The habitat in my yard is a sandhill loblolly pine/sand laurel oak woodland, but McBean Creek bottomland is just about a mile away.  Bird-voiced tree frogs are absent from peninsular Florida.  They may have occurred in peninsular Florida in the past but were extirpated when most of the state was under ocean during marine high stands.

Species Profile: Bird-voiced Treefrog (Hyla avivoca) | SREL ...

Bird-voiced tree frog range map.

I searched the paleobiology database and learned no fossils of this species have ever been found.  A small animal that lives in a forest has a lesser chance of becoming preserved as a fossil.  Leaves turn the soil acid, dissolving bones.  As far as I can determine, no genetic studies of bird-voiced tree frogs have ever been conducted.  It is an understudied species.

An Extinct Map Turtle (Graptemys kerneri) and Pleistocene Sea Level Fluctuations

March 15, 2018

Most species of freshwater turtles can travel overland and occupy new favorable habitat, promoting genetic vigor within the meta population.  They often move between watersheds, and this explains why so many species have such a continuous geographic range.  I’ve seen snapping turtles (Chelydra serpentina) and yellow-bellied sliders (Chrysemys scripta) a considerable distance from any water source.  However, map turtles in the Graptemys genus (10 species) do not travel overland, and their ranges are usually restricted to single river drainages.  So how did closely related Graptemys species colonize different river drainages even though they don’t travel overland?  The dispersal of the Graptemys genus is closely related to Pleistocene sea level fluctuations.

Image result for Barbour's map turtle

Barbour’s map turtle is the closest living relative of the extinct Kerner’s map turtle.

Image result for Barbour's map turtle range

Barbour’s map turtle range.  Note how it is restricted to 1 river system.

Image result for map of Florida during the Last Glacial Maximum

Map of Florida during the Last Glacial Maximum.  Different rivers in Florida isolated by sea level rise today were interconnected on land exposed on the continental shelf due to sea level fall.  This allowed map turtles to colonize adjacent rivers systems where they evolved into distinct species following sea level rise and isolation of populations.

During Ice Ages sea level fell because so much of earth’s atmospheric water became locked in glacial ice.  In Florida dry land habitat extended 120 miles west into the Gulf of Mexico.  Several of Florida’s river systems that are isolated from each other today by sea level rise were interconnected during the Last Glacial Maximum on the land that was exposed by ocean recession.  This allowed an ancestral population of Barbour’s map turtle (Graptemys barbouri), a species today restricted to the Apalachicola-Flint-Chattahoochee River System, to colonize several other rivers in Florida.  Subsequent sea level rise isolated this founder population in the Suwanee, Santa Fe, and Waccasassa Rivers where they evolved into a now extinct species known as Kerner’s map turtle.  Specimens of this species have been found in all 3 of the above mentioned rivers in Florida, and the type specimen (a complete skull) came from the Suwannee.

Kerner’s map turtle had a wider shorter skull than any extant species of map turtle.  Morphologically, it most closely resembles Barbour’s map turtle, the extant species that has the widest shortest skull among living Graptemys turtles.  There is an east-west gradient in the shape of map turtle skulls.  Western species have narrower longer skulls, but map turtle species’ skulls get shorter and wider the farther east they occur.  Kerner’s map turtle was the easternmost species, and it ranged into north central Florida and possibly southeastern Georgia where the Suwannee River headwaters originate.  Rare earth element analysis indicates Kerner’s map turtle lived during the Rancholabrean Age (300,000 years BP-11,000 years BP).  There are no known Graptemys specimens older than the mid-Pleistocene.  The extinction of Kerner’s map turtle likely occurred during a dry climate stage of the mid-Holocene (~6,000 years BP).  Map turtles require fast moving high water where they can disburse up and down rivers.  But drought turns their habitat into stagnant isolated pools that can also be detrimental to their favorite food source–freshwater mussels.  Other species of freshwater turtles and alligators can survive these conditions by moving overland until they find good habitat, but map turtles don’t travel overland.  That’s why most species are restricted to major rivers that rarely, if ever, suffer sporadic flows.

The founding species in the Graptemys genus undoubtedly evolved in the Mississippi River.  Almost all other species exist in other river systems that empty into the Gulf of Mexico.  Pleistocene sea level fluctuations facilitated the colonization and speciation of map turtles in the Apalachicola River drainage, the Guadulupe River System, the Pascagoula River, Mobile Bay drainage, Yellow River System, and Pearl River.  Different map turtle species live in each.  Ocean recession allowed the rivers to become interconnected on the continental shelf, and map turtles were able to colonize adjacent river systems; then sea level rise isolated populations, causing speciation.

Reference:

Ehret, Dana; and J. Bourque

“An Extinct Map Turtle Graptemys kerneri (Testudinae, Emydidae) from the Late Pleistocene of Florida”

Journal of Vertebrate Paleontology 31 (3) May 2011

The Pleistocene Range Extension of the American Alligator (Alligator mississippiensis)

February 4, 2018

Paleontologists excavated 6 artesian springs along the Pomme de Terre River in Missouri before they were inundated by a reservoir about 40 years ago.  They recovered many bones of Pleistocene vertebrates, including the remains of 71 mastodons, along with invertebrate material, plant macrofossils, and pollen.  The scientists published their data in 1 of the papers referenced below.  This is 1 of my favorite studies because the subfossil evidence shows how the local environment changed over time.  During a warm interstadial over 40,000 years ago the region was dominated by hardwood forests of oak, hickory, maple, juniper, dogwood, hornbeam, honey locust, ash, cherry, plum, and Osage orange.  As the climate became cooler and more arid, jack pine and prairie expanded on poor soils, while oak was restricted to richer sites.  When the full glacial maximum struck, the environment transformed into an open spruce parkland landscape where spruce had previously been absent.  The remains of at least 2 alligators were recovered from the deposit dating to the warm interstadial.  This is the northernmost known occurrence in the fossil record of Alligator mississippiensis, and it is approximately 300 miles north of its present day range.  The alligator specimens were found associated with the bones of box turtles, soft shelled turtles, ducks, Harlan’s ground sloth, gopher, giant beaver, raccoon, saber-tooth cat, mastodon, mammoth, horse, tapir, camel, white-tail deer, long-horned bison, and woodland muskox.

Image result for american alligator range map

Current range map of the American alligator.  There is a disjunct population in northern Alabama introduced by man but not noted on this map.  Note the northcentral bulge in this species’ range toward its northernmost Pleistocene occurrence in northwestern Missouri.  Pet alligators released in southern Ohio today at approximately the same latitude can survive but can’t reproduce.

The only other possible known occurrence of A. mississippiensis north of its present day range is from Ladds in Bartow County, Georgia; but I think the paper that referenced this did so in error.  The paper (also referenced below) contains a checklist of all vertebrate species known to have occurred in southeastern North America during the Pleistocene, and alligator is noted as being reported from Ladds.  However, I’ve read all the published data about Ladds, and there is no mention of alligator specimens from this site.  The supposed specimen is also not listed in the paleobiology database.  It’s possible (perhaps even probable) alligators occurred in Bartow County, Georgia during warmer climate phases because north Georgia is much lower in latitude than northwestern Missouri where their remains have been found.  If anyone knows of a Bartow County alligator specimen, please contact me.

Some scientists may think the presence of alligators north of their present day range is evidence of temperatures warmer than those of today, but this isn’t necessarily the case. Instead, Ice Ages caused a retraction in the pre-historic range of the alligator, and they perchance have failed to recolonize all of their former stomping grounds.  If average temperatures continue to increase as predicted, alligators may yet expand their range farther north. It’s also possible alligators are able to extend their range during cycles of reduced seasonality.  The earth goes through cycles when it tilts to a lesser degree than it does now causing milder winters but cooler summers.  Annual average temperatures were the same as they are today but more evenly distributed throughout the year.

Alligators are better adapted to colder climate than any other species of crocodilian.  For example during unusual cold spells American crocodiles (Crocodylus acutus) bask in the sun in an attempt to warm themselves and they often perish, but alligators seek shelter in water, and if temperatures drop too much, they live but go dormant.  Adult alligators can survive quite cold temperatures.  In the northern parts of their range alligator reproduction becomes sporadic.  Though adult alligators can survive severe cold spells, juveniles die.  Alligators require several mild winters in a row before their young get large enough to survive an harsh winter.  Cooler summers and springs will result in an all female population–another potential limiting factor in the northern parts of their range.  Alligator eggs in nests with temperatures that fall below 86 degrees F become female.  Nests are warmer than air temperatures due to composting vegetation, but they can still cool, if the surrounding temperatures are low.  Eggs won’t hatch at all when nest temperatures fall below 80 degrees F.  Either decades of severe winters or cool spring/summers or both probably caused the extirpation of the alligator in Missouri during the late Pleistocene.

Image result for alligator brumating in ice

Alligator brumating (going dormant) in ice.

The American alligator is an extremely adaptable species having survived countless climatic changes.  It has existed relatively unchanged as a species for at least 5 million years.  Scientists aren’t even able to discern a definite difference between modern alligators and fossil specimens from 5-12 million years old, so the American alligator may be a 12 million year old species.  Alligators from the early Miocene are assigned to a different species (A. olseni), and this is the probable ancestor of the modern day alligator.  A. olseni specimens have been found in Tennessee, but climate was much warmer during the early Miocene than it is today.

Reference:

King, James; and Jeff Saunders

“Environmental Insularity and the Extinction of the American Mastodont”

in Quaternary Extinctions: A Prehistoric Revolution  edited by Paul Martin and Richard Klein

University of Arizona Press 1984

Russell, D.A.; F. Rich, V. Schneider, J. Lynch-Stieglitz

“A Warm Thermal Enclave in the Late Pleistocene of the Southeastern U.S.

Biology Reviews 84 (2) May 2009

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.

Image result for pterodactyl vs green lantern

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