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Tag Archives: Paleontology
September 15 is National Online Learning Day. Now that everyone should be well and truly back to school, I thought it would be a good time for a few miscellaneous notes on various resources.
Evolution: A Course for Educators. American Museum of Natural History via Coursera. Learn about evolution from an expert at one of the best places in the world to study it. Taught by Dr. Joel Cracraft, the course will cover everything you need to teach evolution well. The course is free and offers a paid certificate for teacher professional development hours. It is four weeks long and requires 5-8 a week. It begins October 1st, so you will be done by Halloween.
Introduction to Human Evolution. Wellesley College via edX. A subject that is endlessly fascinating, but seldom taught in schools. Learn about the origins of us from an expert. Taught by Dr. Adam Van Arsdale, the course is self paced, meaning you can start when you want. It takes 4-6 hours for four weeks and is free.
Paleontology: Theropod Dinosaurs and the Origin of Birds. University of Alberta via Coursera. A five week course headed by the esteemed dinosaur expert Dr. Phillip Currie on the anatomy, diversity, and evolution of theropods leading to birds. They offer a paid certificate for those needing the credit. Expect to spend 4-7 hours a week on the course. The course is free, but it started September 12, so join up now before you get too far behind.
Paleontology: Early Vertebrate Evolution. University of Alberta via Coursera. This course covers the evolution of vertebrates through the Paleozoic Era and is taught by Dr. Alison Murray. This is a four week course with an expected 3-5 hours per week. This course is free, but offers a paid certificate for those who need the credit. This course also started September 12th, so sign up now.
Dinosaur Ecosystems. University of Hong Kong via edX. A six week course on dinosaurs in their habitats. The course is taught by a collaboration of Dr. Michael Pittman and Dr. Xu Xing, along with other guests, all with an abundance of expertise on the topic. As a bonus, the course includes the work of one of my favorite paleoartists, Julius Csotonyi. The course requires 1-2 hours a week, so not a big time commitment. It is free, although it does offer a paid certificate for those who need the credit, and starts October 4th.
Dino 101: Dinosaur Paleobiology. University of Alberta via Coursera. Another course by Phil Currie, along with Dr. Betsy Kruk. This is a great introduction to dinosaurs. It is 12 weeks long and requires an estimated 3-10 hours per week, so expect more out of this course. The course is free and starts September 29th, so get signed up now.
Origins – Formation of the Universe, Solar System, Earth and Life. University of Copenhagen via Coursera. Learn how it all began by Dr. Henning Haack. This course is 12 weeks long and expects 5-7 hours a week. The course is free and starts September 17th, so don’t waste time signing up.
There are several more available. If you go to any of the course links shown here, they will guide you to other related courses that are available.
Tetrapod Zoology. Darren Naish has kept his blog, often abbreviated to TetZoo, for over a decade. Through all the years, he has provided multitudinous essays on a variety of animal groups, both extant and extinct. Sprinkled in are also essays on the truth of cryptids (Bigfoot, Nessie, and the like), paleoart, and other topics. Sadly, the blog at Scientific American has closed up shop. But don’t panic, because it has moved to another location. He has set up shop under his own banner at Tetzoo.com. Time to change your bookmarks.
Beautiful Minds. Scott Barry Kaufman has been writing a Scientific American blog about psychology off and on. He recently announced an upgrade to the blog allowing him to have a weekly online column, so expect more articles about human nature from him.
Science Sushi by Christie Wilcox has always been one of my favorite blogs. While I am not a marine biologist by any stretch, she has always been interesting to read. So it is sad to report her Discover blog is closing up shop. She is moving to ScienceSushi.com, but will not be adding regularly to it. She will continuing to write, so keep an eye out for her on the sites she lists in the post linked to here.
Dataset Search. You’ve heard of Google Search, Google Scholar, Google Maps, and a plethora of other ways Google lets people search the web. Now meet Dataset Search, for when you are trying to find data that has been published or stored online. This searches for data files or databases according to how they are identified, not by what is in the file.
Science without publication paywalls: cOAlition S for the realization of full and immediate Open Access, by Marc Shiltz. PLoS Biology. 2018. This article discusses Plan S, a proposal by a coalition of European leaders to make science articles free for everyone. In their words, “no science should be locked behind paywalls!” (emphasis theirs).
Seriously, Science? A great blog on Discovermagazine.com that covered weird and humorous published research has been canceled. No word on why, the authors just said they were informed they would no longer have a slot on the blog roll. So long, Seriously Science, it was good to have known you.
Return to Reason: The Science of Thought, by Scientific American. 2018. This ebook is a collection of essays discussing why facts don’t seem to matter to people or help persuade them and what we can do about it. Well worth a read.
Timefulness: How Thinking Like a Geologist Can Help Save the World, by Marcia Bjornerud. Princeton University Press. 2018. Most people can barely remember what they had for breakfast yesterday. We really aren’t well equipped to think about time on the scale of millions and billions of years. Dr. Bjornerud has written a great book to help people come to grips with the immensity of time. I highly recommend it.
Underbug: An Obsessive Tale of Termites and Technology, by Lisa Margonelli, Scientific American/Farrar, Straus and Giroux, 2018. This book is not really about termites. The study of termites is used as an illustration of scientific inquiry and the questions that researchers come across during their studies. There are questions about the termites, but also about how science is done and about humans viewed through a different lens.
Darwin and the Making of Sexual Selection, by Evelleen Richards. University of Chicago Press. 2017. This book tells the story of how Darwin figured out problems with natural selection by coming up with sexual selection. To my mind, sexual selection is a subset of natural selection, but it is generally viewed as separate, with natural selection being success based on fecundity and survival of offspring, whereas sexual selection deals with the choices of mates. However you look at it, sexual selection is an important concept and this book explores the origin of that idea.
The Dinosaur Artist: Obsession, Betrayal, and the Quest for Earth’s Ultimate Trophy, by Paige Williams. Hachette, 2018. Williams tells the story about a skeleton of a Tarbosaurus bataar, what could be described as a Mongolian Tyrannosaurus rex, and the long and confusing battle of who owned it and where it would eventually reside. The worldwide fossil trade is a morass of differing opinions, laws, and money. This book attempts to tease apart the strands to answer the question of who owns fossils.
Through a Glass Brightly: Using Science to See Our Species as We Really Are, by David P. Barash. Oxford University Press, 2018. As the great physicist Richard Feynman said, “The first principle is that you must not fool yourself–and you are the easiest person to fool.” Humans are masters of deluding ourselves, but science helps us remove the wool we place over our eyes to see things, and ourselves, as we truly are. Only then can we become the people we see ourselves as. That is the goal of evolutionary biologist Dr. Barash in this book.
The Book of Why: The New Science of Cause and Effect, by Judea Pearl and Dana McKenzie. Basic Books, 2018. A big problem that any educator sees is the rather unbelievable lack of understanding many people have about cause and effect. Please get this book and teach people about how cause and effect works. Since this book relates the science of cause and effect to robots and artificial intelligence, it will be the perfect addition to tech classes.
I think that is enough for now. It is certainly enough to keep you busy if you try even a few of the many offerings available for furthering your education or just indulging your curiosity. Enjoy. If you try them, come back and let us know what you thought of them.
It is long past time I resurrected Monday Mystery fossils. So to celebrate the season, here is a little animal whose relatives, or at least representations thereof, shall be widely seen over the next month.
If you think you know what this is, please leave your identification in the comments. I will let everyone know what it is and where fossils like this have been found in Arkansas on Friday. Have a great October!
Greetings and welcome to the final day of Prehistoric Shark Week! All week we have covered sharks that swam in Arkansas during the Cretaceous Period. The dinosaurs get all the press, but we had a diverse marine ecology during that time. Last week, we met a few of the non-shark denizens, such as mosasaurs, elasmosaurs, and more. This week, we have seen nurse sharks, goblins, sand tigers, and an array of rays, skates, and angel sharks. We wrap up the festival of marine animals with the question that everyone wants to know. Where did the most famous sharks of all time, the Great White and Megalodon, come from and how does Arkansas play into this?
The Great White, or simply White Shark, is named Carcharodon carcharias, meaning sharp tooth pointer, although more popularly named for its white belly, is well known as the largest living predatory fish in the sea, reaching up to and, probably over, 20 feet. Megalodon, listed either as Carcharocles megalodon or Carcharodon megalodon, depending on whether or not one believes it is directly related to or convergent with White Sharks, is the largest known predatory fish ever, reaching sizes up to three times that of the White Shark. It appeared in the fossil record about 16 Mya, but went extinct 1.6 Mya (contrary to what a fictitious documentary on the Discovery Channel claimed).
During the Cretaceous, the southwestern part of the state was covered by the Western Interior Seaway, which for us, was essentially equated to having the Gulf coast not just on our doorstep, but flooding it. Those waters were warm, rich in nutrients, and a hotbed of marine life. In those waters, a few sharks of interest made their home.
All of the sharks we will be talking about are lamniform sharks. These sharks are known for being at least partially endothermic, meaning they used their core muscles to create their own heat and maintain an elevated body temperature, giving them the ability to be active hunters even in cooler waters. Of course, it also meant they were hungrier, needing more food, keeping them always on the prowl. This is what allows the White to be such a fearsome hunter today, giving it the power and energy to breach completely out of the water during attacks.
Squalicorax is an extinct shark of the time that is commonly thought to have resembled Whites. These sharks got up to five meters, although they were typically around two meters. Squalicorax is also called the Crow Shark, which some people have speculated it got that name from evidence of its scavenging. However, squalus means shark (and is the scientific genus name for dogfish) and corax means crow, so the name Squalicorax literally means crow shark. Now as to why it was named that way to begin with, no one knows because when Agassiz named it in 1843, he didn’t leave a record as to why. They hunted and scavenged a wide range of animals, everything from turtles to mosasaurs. Unfortunately, the relationships between Squalicorax and other lamnids is uncertain, so whether or not it could have been ancestral to anything, much less Whites or megalodons, is unknown at present.
Another candidate is a shark named Isurus hastalis, an Oligocene shark that lived 30 Mya. Isurus also includes the modern day mako shark. However, a researcher by the name of Mikael Siverson concluded that the Isurus teeth were not makos, but worn down teeth similar to modern Whites. So he changed the name to Cosmopolitodus. It has also been suggested that these sharks originated from a shark called Isurolamna, which lived in the paleocene 65-55 Mya.
A more recent view, and one which I back (with freely admitted bias because it allows me to say they evolved from Arkansas sharks:) ), is that both Whites and megolodons evolved from an extinct lamnid called Cretolamna, the Cretaceous lamna. This shark had large, strong teeth and was very successful. It had a worldwide distribution and lived from the Cretaceous to the Paleocene. Cretolamna fossils have not been reported in Arkansas thus far, but they were a member of the family Cretoxyrhinidae, of which the shark Serratolamna was a member. The teeth of Cretolamna and Serratolamna are extremely similar, as one might expect from genera in the same family. However, Serratolamna teeth have serrations and Cretolamna does not, making Serratolamna teeth closer in shape to the White Shark. Serratolamna did not have the same worldwide distribution and did not last as long as long as Cretolamna, though. It is impossible to tell which one was directly ancestral to the later sharks, but Cretolamna, due to its more cosmopolitan range, has gotten the nod. It was named first and is much better known than Serratolamna, giving it an edge when people find and identify fossil shark teeth. Thus, it is not a big stretch to say that Serratolamna, or a very close relative, eventually evolved into Carcharodon carcharias as well as Carcharocles (or Carcharodon) megalodon.
I hoped you have enjoyed Prehistoric Shark Week and the previous week of Cretaceous Arkansas marine predators. Let me know if there is another group that you think deserves special consideration for a celebratory week.
For Day 4 of Prehistoric Shark Week, I would like to mention another modern day shark that has been around since the Cretaceous: the sand tiger sharks. Tomorrow, I will discuss a couple of Cretaceous sharks that may be the ancestors of the two most famous sharks in the world – the Great White and the giant Megalodon.
The Sand tiger is a common shark in the Cretaceous sediments, or at least, their teeth are, which means they were probably pretty common back then. The teeth tend to be long and thin, with two small cusps on either side of the large, center blade. Elasmo-branch.org reports that the center blade is smooth-edged with a strongly bilobed root, large bulge in the center of the root (aka lingual protruberance), and nutrient foramen in the center.
There are actually two sharks that are often called sand tigers in the Cretaceous rocks. One is Carcharias holmdelensis, the Cretaceous version of Carcharias taurus, the modern day sand tiger shark. Also going by the name grey nurse shark, amid several others, sand tigers are large-bodied sharks that will eat pretty much anything, but since it is a fairly slow and placid shark most of the time, it doesn’t seem to go after anything that requires a lot of effort. They are known for gulping air to allow themselves to float in the water column without expending much effort. So although they look scary, they appear to be too lazy to live up to appearances.
The other shark that gets called a sand tiger, is Odontaspis aculeatus, one of the ragged toothed sharks, which also go by the name sand tiger. These sharks were until recently in the same family as Carcharias, but have since been pulled out into their own family. They are very similar, as one might has guessed from the numerous times these sharks have been grouped and split over the years. As Elasmo-research.org put it, “Chaos reigned until Leonard Compagno examined museum specimens from all over the world, corrected misidentifications and sorted out synonyms.”
For Day 3 (a little late, yes) of Prehistoric Shark Week, I want to bring to your attention the diversity of chondrichthyans that have opted for a flatter bauplan.
Sharks are generally split into two groups, the galeomorphs, which are mostly the more typical torpedo-shaped sharks, including the sharks that most people think of when they envision a shark. The other group is the squalimorphs. These sharks lack an anal fin and many of them have developed a penchant for flatter bodies and broad pectoral fins, and in some cases pelvic fins as well (although not all, such as the dogfish and frilled sharks). Up until recently, the batoids, otherwise known as skates and rays, were considered part of this group, the consensus being that they were a more specialized type of squalimorph shark that had taken flat to an extreme. But the most recent molecular studies have indicated that they are a group unto themselves. The batoids have a long fossil history, with a number of ray teeth found in the Cretaceous deposits of Arkansas, particularly the eagle ray family Myliobatidae. Their teeth are typically flat rectangles on top with a comb-like surface below. Another type of ray that can be found are the guitarfish, or Rhinobatos casieri. These pectoral fins of these fish extend to their head, giving them a triangular shaped front end of a more traditional shark-like back end.
Skates and rays are generally very docile and would not be very threatening, spending their time scrounging about on the sea floor for benthic (living in or on the sea floor) invertebrates and the occasional fish. The same can’t be said for the last member of this group, the sawfish. Armed with a rostrum (its elongated snout) with teeth out to the side, the fish looks like it has a chain saw for a nose. The sawfish will swim into a school of fish and thrash its rostrum rapidly back and forth, spearing and stunning several fish, which it can then gobble up. They can also use it to dig up clams and crabs from the sediment. While they won’t attack humans, any human who provoked one may easily wind up perforated by the rostrum, probably not deadly but certainly painful. Most modern sawfish reach a respectable two meters, but the largest species, the green sawfish (Pristis zijsron) can top seven meters (24 feet). This is as large as the Cretaceous versions. Modern sawfish are typically put into the family Pristiformes. The Cretaceous ones are in their own family, called Sclerorhynchiformes and are not directly related, in that the Cretaceous ones are not thought to be ancestral to the modern ones. They are both put into the group Pristirajea, so they are thought to at least be related. But with the uncertainties in the relationships of the modern fish, the relationships with fossil forms are necessarily less certain. In any case, Arkansas sports several different species from this group, including Schizorhiza stromeri, Sclerorhynchus sp., Ischyrhiza mira, Ischyrhiza avonicola, and Ptychotrygon vermiculata. We were postively awash in sawfish.
The true squalimorph sharks that have shown up in the Arkansas Cretaceous rocks are best represented by the Angel shark (Squatina hassei), which looks like an early rendition of a skate, so it is little wonder that most researchers viewed skates and rays as simply more specialized versions of these sharks. Nevertheless, it appears this is case of convergence, not homology (similarity due to relationship). If it is homologous, it isn’t directly so. It is possible both groups had a common slightly flattened ancestor and each took their own route from there.
All of these fish are pretty docile hunters, scrounging around the sea floor for benthic organisms, all those animals that make their home in or on the sea floor sediments. They spend their time digging around the sand for crabs, clams, and other invertebrates, the occasional fish. When threatened by the presence of a predator, they hide on the bottom, using their shape to help them blend in with the seafloor. Neither the ones today or the ones in the Cretaceous would have bothered a human swimming around them.
Becker, Martin A., Chamberlain, John A., Wolp, George E. 2006. Chondricthyans from the Arkadelphia Formation (Upper Cretaceous: Upper Maastrichtian) of Hot Spring County, Arkansas
Welcome to Day 4 of Paleo-Animal Fest, celebrating the creatures populating the Arkansas seas during the Cretaceous. Today we are going to look at a fish that has survived for an amazingly long time. They first appeared in the Late Cretaceous and have survived to the present day, still thriving. You can find them in many freshwater lakes and rivers, especially brackish and hypoxic (low oxygen) waters, even into marine waters on the occasion. They are a tough predator in many ways, from their durability in the fossil record to their physical defenses and their intimidating jaws. I am of course talking about gars.
Gars are piscivorous, meaning they eat other fish. The most common description of them is “voracious predator.” They are known for their tooth-filled jaws, scales of armor, and their fight. Their typical mode of attack is a lightning-quick sideways bite. Gar fishermen are often called “not right in the head.”
Gars can be found in many places within North America, but their fossils can be found all over the world. The vast majority of the fossils have been identified as Lepisosteus, which includes the longnose, shortnose, spotted, and Florida gar. However, most of their fossils are isolated scales, which makes it difficult to impossible to tell what type of gar it is from. So I am going to go with most people’s favorite gar, Atractosteus spatula, the alligator gar (pictured above). It is the biggest one reaching almost 3 meters. Another impressive armored, ancient fish that is still around is the sturgeon, which can get a lot bigger, but are nowhere near as impressive in the teeth department.
There are not a lot of skeletons of gars with heads and tails, but there are a lot of body pieces covered in scales. Gar scales are thick, rhomboid-shaped ganoid scales, meaning they are covered in what is effectively enamel. The scales form an excellent armor, making handling them hard on the hands. They are so tough and dense, in fact, that the scales have been used as arrowheads and make even CT scans on gars hard to impossible to get decent views. On the plus side, this results in them having excellent preservational potential and can be found quite commonly. The scales make the fossils really stand out and readily identifiable to at least the group Lepisosteiformes.
By far, the most complete and detailed description of gars ever published is by Lance Grande, the universally acknowledged leading world expert on fossil fish, called “An empirical synthetic pattern study of gars (Lepisosteiformes) and closely related species, based mostly on skeletal anatomy. The resurrection of Holostei.” Special publication 6 of the American Society of Ichthyologists and Herpetologists, published in 2010. This is a massive tome, amassing almost 900 pages of detailed observation on gars. This book is a companion to a similar volume he did on bowfins. I can honestly say I have never seen a more thorough job on any group such as this in my life. Every time I look at it, I think wow, all this on just gars? This would make any scientist proud to have one of these capping their life’s work and this doesn’t even begin to touch the work put out by Grande. I am in awe.
Continuing our celebration of marine animals of the Cretaceous found in Arkansas, here is a picture of a mosasaur. It is from the Dallas (Perot) Museum of Nature and Science. They have a great display of several different mosasaurs. You can also see one on display at the natural history museum located at the University of Texas at Austin.
Mosasaurs were the apex predators of their time, which was in the Late Cretaceous. Tyrannosaurs may have ruled the land, but mosasaurs ruled the seas. The first mosasaurs appeared in the early Cretaceous, but by the end, they dominated the oceans. Unfortunately for them, they only had a 20 million year or so run at the top before the mass extinction at the end of the Mesozoic Era wiped them out along with the dinosaurs.
Mosasaurs were not related to dinosaurs, other than also being reptiles. They were most closely related to the group of lizards that include the monitor lizards, such as the Nile monitor and Komodo Dragon. They were fast predators with a powerful tail to move them through the water. Mosasaurs were so adapted to the water that they bore live young and were not able to walk on land, although they did still have to surface for air like every other reptile. Recent research has found they were endothermic (warm-blooded), unlike their competitors, giving them an edge by allowing them to sustain higher activity levels. It also meant they had to eat more often, making it necessary for them to be effective hunters. Research has also indicated they were countershaded, with a lighter belly than the back, much like many sharks of today. They had a varied diet, with some species specializing in different prey, so over the whole group, they pretty much ate everything in the ocean.
Mosasaur bones have been found in many places throughout southwest Arkansas, which was covered by the Western Interior Sea during the Cretaceous. Two species have thus far been recognized. Platecarpus was fairly small, only 4-5 meters (13-16 feet), but were noted for some exceptionally preserved fossils that retained the impressions of a tail fluke, allowing paleontologists for the first time to see what their tails looked like. The other species is Mosasaurus itself, a huge predator that reached lengths of 15-18 meters (50-60 feet).
One question I get asked a lot when I show fossils to people is “Is it real or fake?” It is a question that always irks me because it seems very few people understand that this is an entirely wrong question.
People like to categorize things into binary bins. Is it black or white? Republican or Democrat? Is it raining or not? Do you accept science or religion? Of course, none of these questions make any sense as an either/or question. Just like real or fake, all of these questions miss the fact that there is more to it than one or the other. All of them can only be correctly answered if one is cognizant of the other variations. So today, I am going to introduce to you a more nuanced view of whether or not the fossils you see in museums are real or not.
Real fossils need little explanation. They are the actual fossil material. Whether or not it is actual bone or shell being preserved, a bone that has been replaced with minerals, a natural mold, or other some such style of preservation, they are real.
Real in this case does not mean it is remains of the actual organism, although it can be. Bone, shell, leaves, and other tissues can be preserved indefinitely under the right conditions. Usually however, they are replaced with minerals or remain only as impressions in the sediment. In any case, these are all real fossils. They are the original fossil found, dug up, and brought back to the institution or person to whom it belongs.
Replicas are casts or molds made from the actual fossil. They are made to look as close as possible to the original fossil. These are made so that the original can be protected while the copy is shown to many more people than could see the original. Use of replicas allows copies to be put in the hands of many people all over the world. In many instances, the original is too fragile or heavy to safely transport.
The important point about replicas is that they are not fakes. They are duplicates of a real fossil. In some cases, they can be even better than the real thing. After decades of handling, the original fossils can get worn or broken, with details once present no longer visible.
Fakes, on the other hand, represent something that is not only not real, but never existed. Many fakes are designed to deceive and so are often called forgeries. The difference between what many people think of as forgeries and what we are talking about here is that forgeries are usually designed to trick people into thinking they are the real thing. A replica, if presented as the real thing, would be considered a forgery. However, in paleontology, most things described as forgeries are in reality fakes designed to deceive people into thinking a fiction is real. Fakes are never acceptable in museums unless explicitly labeled to indicate that they are fantasies. The Piltdown Man is an example of a fake. It was made with the express purpose of making people think it was real, when in fact it was created from bits of human and animal bones that were altered to make them look like they belonged to the same primitive human.
Archaeoraptor was another fake. This one adds a wrinkle in the topic though. Archaeoraptor was made by gluing pieces of different fossils together. The individual pieces were real, but the resulting chimera was a fake.
As Archaeoraptor shows, fakes don’t have to be unreal to be fictional. There are lots of fakes that are real fossils put together in intentionally misleading ways. In the case of Archaeoraptor, they were simply trying to make the fossils more spectacular so they could sell them for a higher price. Others are done to discredit scientists or simply as pranks for fun.
Of course, there are plenty of fakes that are made up out of whole cloth. Numerous “human” footprints found with dinosaur tracks are nothing more than carvings designed to trick gullible people. I have personally seen several in which the tool markings were clearly visible. The most famous picture of the Loch Ness Monster, known as the surgeon’s photo, was a fake.
So remember, when you are going to a museum or looking at fossils from a paleontologist, you may be looking at real fossils or replicas. But you will never be looking at fakes. They may not be the original fossils, but they are not trying to mislead you or lie to you, which is what fakes are trying to do. If you really want to see fakes, try here or here. And please, don’t insult your local paleontologist by saying they are showing you fakes when all they are doing is showing you replicas of real fossils that you might otherwise never be able to see.
Here is a new fossil for you to identify. I haven’t put up anything like it before, so you can rule out any of the usual candidates. I will put up the answer next Monday unless some early bird beats me to it. Good luck.
So were you able to identify our fossil this week?
This if Figure 5 from the only real publication on Arkansas fossil barnacles. I posted an articles on barnacles once before, but time grew short and I neglected to mention specifically the Arkansas ones, an egregious error on a website devoted to Arkansas fossils. So I am now correcting that with this post.
As I mentioned in the last post, barnacles are crustaceans and have been around since the Cambrian Period. They can be found throughout much of the Northwest half of the state, basically anywhere not carved out by the Mississippi river. However, other than some miscellaneous purported barnacles borings on clam shells and the like in the Ozarks and Ouachitas, there is not really any published literature on the subject.
For published information, if you really want to know about barnacles, you need to talk to Victor Zullo at the University of North Carolina, Ernest E. Russell of Mississippi State University, or Frederic Mellon. Sadly, you will find that difficult as they are all now deceased, leaving the field of Arkansas cirriped studies completely wide open to the prospective student.
In 1987, the trio published a paper detailing two new species of barnacles found in a quarry in Hot Springs County, Arkansas. The first barnacle was identified as being in the suborder Brachylepadomorpha and was named Brachylepas americana. They listed this as important as being “quite possibly the richest single accumulation of brachylepadomorph material ever encountered.” They also suggest that because of its similarity to other species in Europe that there was “unrestricted communication between these widely separated geographic regions during late Campanian time.”
Another thing I found interesting about these barnacles is where they were found. Thousands of these fossils were found in a gravel within the Brownstone Formation, dated to the Late Cretaceous, and deposited in a littoral environment. This is a high energy, near shore environment. The living representatives of this group, though, are only found near hydrothermal vents.
The other barnacle they discuss and the one which is shown in Figure 5 above is Virgiscalpellium gabbi and a subspecies V. gabbi apertus. These are only known from nine specimens however, unlike the thousands of B. americana. This seems to be a much less common species throughout its range than other barnacles.
Along with the barnacles, the trio mention the Brownstone Formation is rich in fossils of other types, including, the oyster Exogyra ponderosa, several gastropods, a sponge, brachiopod, serpelid worm, bryozoans, nannoplankton, and the odd vertebrate, such as mosasaurs, sharks, and skates.
Zullo, Victor A., Russell, Ernest E., and Mellen, Frederic F. 1987. Brachylepas Woodward and Virgiscalpellium Withers (Cirripedia) from the Upper Cretaceous of Arkansas. Journal of Paleontology. Vol. 61(1):101-111.