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Today is National Fossil Day™. The National Park Service holds this annual event on the second Wednesday every year to coincide with Earth Science Week sponsored by the American Geosciences Institute. Earth Science Week highlights the important role of earth sciences in our everyday lives and “to encourage stewardship of the Earth.” National Fossil Day is, as NPS says, “held to highlight the scientific and educational value of paleontology and the importance of preserving fossils for future generations.”
In honor of the day, I am going to give you a whirlwind tour of some of our most outstanding fossils from all over the state. People may not think of Arkansas as being rich in fossils, but we have a rich natural history spanning 500 million years. To give you a quick summary of the wide array of fossils, just check out the map on the fossil page, reproduced below.
The most fossiliferous region in the state is the Ozarks, without a doubt. It is a favorite fossil collecting spot for many people, even though much of the area is national forest or national park owned, which prohibits fossil collecting. Nevertheless, fossils may be collected on any roadcut. I-65 near Leslie has several fossiliferous roadcuts. You are most likely to find abundant examples of crinoids, bryozoans like the screw-shaped Archimedes, clams and brachiopods, ammonoids (mostly goniatites), corals such as horn corals and tabulate corals, as well as the occasional echinoid and trilobite, along with many other types of fossils. This list of fossils makes it plain that the Ozarks are dominated by marine deposits, but you can find the occasional semi-terrestrial deposit loaded with plants like Calamites and Lepidodendron.
Top, left to right: Calamites, spiriferid brachiopod, blastoid echinoderm, goniatite ammonoid. Bottom left to right: Archimedes bryozoan, crinoid with calyx and fronds (very rare, mostly you just find pieces of the stalk).
There are a few fossils that particularly stand out. One is Rayonnoceras, a nautiloid ammonoid, which reached lengths of over two meters, making it one of the longest straight-shelled ammonoids ever found. The other is a shark named Ozarcus. While shark teeth are common, it is rare to find one that preserves parts of the skull and gill supports. At 325 million years, Ozarcus is the oldest one like this ever found and it changed the way we viewed shark evolution, indicating that modern sharks may be an offshoot of bony fish, not the other way around.
We can’t leave the Ozarks without talking about Conard Fissure, a spectacular collection of Pleistocene fossils. Barnum Brown excavated the first chamber of the cave in 1906, pulling out thousands of fossils or all kinds, many of which were new to science. Of course, of all of them, the ones that most people remember were 15 skeletons of Smilodon, the largest of the saber-toothed cats. The one pictured to the right is a cast of one from La Brea, California. All of ours are held at the American Museum of Natural History.
The Ouachita Mountains are not nearly as fossiliferous, but they have two important types of fossils that are commonly found: graptolites (below left) and conodonts (below right, not from AR, Scripto Geologica). Graptolites are thought to be closely related to pterobranchs, which are still living today, even though the graptolites themselves are all from the Paleozoic Era. Most of the time, Graptolites look like pencil marks on slate, but if you find a good one, you can see they are often like serrated files that may come branched or coiled. The reason these are important is because they are hemichordates, the closest group to the chordates, all animals with a spine (either a stiff rod or actual bone). Conodonts, on the other hand, are the closest we have to the earliest vertebrates, looking like nothing so much as a degenerate hagfish.
The coastal plain is quite fossiliferous and has attracted the majority of press because it is here where you will find Cretaceous aged rocks and that means dinosaurs and their compatriots. Here you will find thousands of Exogyra oysters. Scattered among them, you can find numerous shark teeth, along with teeth from Enchodus, the saber-toothed herring (although not really a herring), especially if you look in the chalk beds. You can also find the rare example of hesperornithids, extinct diving birds, as well as fossil crocodilians.
But of course, the main draws here are the marine reptiles and the dinosaurs. Mosasaur vertebrae are not uncommon, although the skulls are. More rarely, one can find plesiosaur (the article only mentions elasmosaurs, which are a type of plesiosaur, but most plesiosaur fossils in Arkansas cannot be identified that closely) vertebrae as well.And then of course are the dinosaurs. We only have a few bones of one, named Arkansaurus, but we have found thousands of footprints of sauropods, the giant long-necked dinosaurs. Since the sauropods that have been found in Texas and Oklahoma are titanosaurs, such as Sauroposeidon, it is a good bet the footprints were made by titanosaurs. A few tracks have also been found of Acrocanthosaurus, a carnivorous dinosaur like looked something like a ridge-backed T. rex. Acrocanthosaurus reached almost 12 meters, so while T. rex was bigger, it wasn’t bigger by much.
Top left: Mosasaur in UT Austin museum. Top right: Plesiosaur vertebra from southern AR. Middle left: reconstruction of Arkansaurus foot. Middle right: statue of Arkansaurus (out of date). Bottom left: Sauropod footprints. Bottom right: Acrocanthosaurus footprint, Earth Times.
The eastern half of the state is dominated by river deposits from the Mississippi River, so the fossils found there are mainly Pleistocene aged, with the exception of a few earlier Paleogene fossils near Crowley’s Ridge. Pleistocene deposits can be found all over the state, as they are the youngest, but are most common in the east. In these deposits, a number of large fossils have been found. A mammoth was found near Hazen, but we have almost two dozen mastodons scattered over the state. I already mentioned Smilodon, but we also have , the giant short-faced bear, dire wolves, giant ground sloths, and even a giant sea snake named Pterosphenus. Most unusual of all is a specimen of Basilosaurus, which despite its name meaning king lizard, was actually one of the first whales. Considering the month, I would be remiss not to include Bootherium, also known as Harlan,s musk ox, or the helmeted musk ox.
Top left: Mastodon on display at Mid-America Museum. Top right: Basilosaurus by Karen Carr. Bottom left: Arctodus simus, Labrea tar pits. Wikipedia. Bottom right: Bootherium, Ohio Historical Society.
This is nowhere near all the fossils that can be found in Arkansas, but it does give a taste of our extensive natural history covering half a billion years. After all, we wouldn’t be the Natural State without a robust natural history. Happy National Fossil Day!
National Fossil Day is today. The Museum of Discovery is having their second annual National Fossil Day event this Saturday. In celebration of these events, I am reviewing important fossils of Arkansas. Last post I stated my picks for the most famous fossils of Arkansas. This time I will discuss what I think are the most common fossils in particular regions of the state.
In the Ozarks, you can find an abundance of marine fossils. There are ammonoids, bryozoans, brachiopods, clams, corals, echinoids, and many others. The Pitkin limestone is so chocked full of Archimedes bryozoans that it is sometimes referred to as the Archimedes limestone. But overall, I have to go with crinoids as the most commonly found fossil in the Ozarks. Crinoids lived throughout the Paleozoic Era, making them potential finds throughout the region. They survived even up to the present day in deep marine settings, but in the Paleozoic, they lived throughout the shallow marine realm, which is where fossils are most common.
Known as sea lilies today due to their plant-like appearance, they are actually echinoderms, making them relatives of sea urchins and sea stars. While not common today, they were quite abundant during the Paleozoic. Most of the fossils of crinoids are of their stems, which look like stacks of circles with the centers punched out, sort of like flattened rings. But occasionally, you can find the tops of the crinoids with the body (called a calyx) and the arms still intact. These are rare because, like all echinoderms, the body is made of plates that fall apart into indistinguishable fragments shortly after death.
You will not find many fossils in the Ouachitas, but two types of fossils are commonly found there, conodonts and graptolites. Conodonts are the toothy remains of the earliest vertebrates. Unfortunately, you can place several of them on the head of a pin, so unless you are looking at rocks under a microscope, you probably won’t see them. That leaves graptolites, which can be found in several places fairly easily. Unless you know what you are looking at, they can be easy to miss. On black shale, they often appear as pencil scratches that are easy to overlook. But look closely and you will see that many of them look like tiny saw blades. These are what remains of animals we call today pterobranchs. These animals are the closest an animal can get to being a chordate, the group that includes vertebrates, without actually being one. So the Ouachita mountains have fossils that bracket that hugely important transition from spineless to having a backbone.
For the third choice, one could always argue for shark teeth, which are commonly found in southwest Arkansas, but can be found most anywhere in the state. But if we limit our discussion to the southwest part of the state, the easiest to find on the basis of quantity and size I think has to go to Exogyra ponderosa. These are Cretaceous aged oysters known for their thick shells adorned with a curled hornlike shape. They are big, sturdy, and can be found by the thousands. One can only imagine that the Cretaceous was a great time to be an oyster. At that time, southwest Arkansas was beachfront property. with lots of shoreline and shallow marine deposits of sand, shale, limestone, and the famous Cretaceous chalk deposits. Dinosaurs walked along the beach, marine reptiles like mosasaurs and elasmosaurs plied the waters, along with sharks and fish of all kinds. And between them lay mountains of oysters.
You may notice that I left out pretty much all of eastern Arkansas. That is because that region of the state is covered in fairly recent Mississippi river sediment, so you don’t find that many fossils in that part of the state. Some have been found, such as the Hazen mammoth, mastodons, sea snakes, and the occasional giant ground sloth or whale, but the fossils are few and far between. So while they have several fascinating fossils, they aren’t going to show up on anyone’s list of commonly found fossils.
So those are my choices. Do you have other suggestions?
Now that Labor Day has come and gone, everyone should be back to school by now. I have been absent for much of the summer and not posted nearly as much as I had hoped to. I have been working on some projects which I hoped to have up by now, but are still in process. Working two jobs right now while trying to maintain some semblence of a personal life has left me precious little energy to work on Paleoaerie. But hopefully, that should end soon and I will be back to posting on a regular basis.
In the meantime, there are some news and upcoming events I would like to share so you can put them on your calendar.
- I have received the audio for my talks at the Clinton Presidential Library. Unfortunately, the video was not successful. So as soon as I get the chance to sync the audio to the powerpoint, I will post it here.
- I have joined forces with TIES, the Teacher Institute for Evolutionary Science, sponsored by the Richard Dawkins Foundation for Reason and Science. They have a number of excellent resources on their webpage and will allow an improved opportunity to offer workshops on evolution to teachers and other interested parties. These workshops are designed by teachers for teachers and are aligned with the Next Generation Science Standards. If you are interested in a workshop, please either contact me or Bertha Vasquez, the TIES Director. You can also find them on Facebook and Twitter.
- I will be appearing at the Forest Heights STEM Academy in Little Rock on Friday, September 11, to discuss how the scientific method is really used by scientists.
- I will be appearing at the next quarterly meeting of the Arkansas STEM Coalition meeting on September 25 to talk about TIES and National Fossil Day.
Speaking of National Fossil Day, make sure to put Saturday, October 17th on your calendar. The Museum of Discovery is hosting the second annual National Fossil Day event, even bigger and better than last year. Don’t miss it. National Fossil Day is a part of Earth Science Week, sponsored by the American Geosciences Institute, designed to “help the public gain a better understanding and appreciation for the Earth Sciences and to encourage stewardship of the Earth.”
Now that all the business is out of the way, I will get on with more educational material. In honor of everyone going back to school, I thought I would start a few posts about some definitions that most people generally get wrong. Today, I am going to discuss a few of the types of scientists that study past life.
Whenever a scientist tells people they are an archaeologist or paleontologist, they tend to brace themselves for the almost invariable questions about the other field. In most people’s minds, all the different sciences seem to be interchangeable, with little understanding that just because someone studies the past, they don’t necessarily study everything in the past. I won’t even get into the difference between scientists who study past life and historians. I will leave that for any archaeologists who wish to tackle that issue. I get this question so often that I bought this Tshirt.
Even though we all study past life, there are important differences. Here is a Venn diagram I created that may help explain how they differ.
As you can see, there are two main divisions in scientists who study past life: those who study humans and those who study everything else.
Anthropologists study humans, so don’t ask them about dinosaurs or mammoths or giant sharks. Don’t bring them a fossil you found. If you find a pottery shard or an arrow head, find an anthropologist. If you found a book, you might also try a historian. Ok, I said I wouldn’t get into this, but maybe just a little bit. Historians deal with written human history. So one might say that historians are a subset of anthropologists, in that they only deal with relatively recent anthropology. Many would also argue that they should not be included at all because they do not approach the endeavor with a scientific approach. While I can see the point, I can also see the point that this would also include many anthropologists, so comes across as sounding like the argument about can bloggers be considered journalists. The correct answer is that it is not as simple as that. But it’s not my field and my view of the topic is strictly as an outsider.
Paleontologists study everything that does not include humans. So please feel free to ask us about extinct organisms, as long as they don’t make pottery or arrow heads.This doesn’t mean to say that every paleontologist studies all extinct organisms. There are innumerable specialities within the field. If you ask a paleoclimatologist to identify a bone, he won’t have a clue what you are talking about. They study past climates, not bones. Just like one wouldn’t ask a podiatrist (foot doctor) to do brain surgery, don’t expect an expert in Pleistocene pollen to help you identify which type of trilobite you have, although I expect they could tell you that you do indeed have a trilobite.
But what do you do if you find a fossil of a hominid, something not quite human, but not quite an ape? That is where paleoanthropologists come in. They deal with that intersection between paleontology and anthropology, where the lines blur into shades of grey. In point of fact, all these terms are arbitrary boundaries and only serve to help us break up the studies into something manageable. Like everything else in nature, we have taken a continuous spectrum and cut it into defined sections to satisfy our need to categorize everything.
Even though there is far more life that is not human than there is that counts as human, for obvious reasons. The study of humans is more discussed than anything else. So while it is not my field, i will attempt to separate the major divisions within anthropology. Anthropologists, as mentioned study anything to do with humans. This can be broken down into two main categories. Physical anthropologists study the biology and evolution of humans. If you have human bones, they are the ones to talk to. Cultural anthropologists study human culture, their behaviors, what they make, how they interact with others. If it’s not a bone, but related to humans, ask a cultural anthropologist.
But what then are archaeologists? Do they not do the same thing as anthropologists? Yes, because they are anthropologists. They are just a subset that happens to be so well known that many people lump archaeologists and anthropologists together as if they are the same thing. But they aren’t, not quite. All archaeologists are anthropologists, but not all anthropologists are archaeologists.
Archaeologists study past human life through physical remains. Thus, they include some of both physical and cultural anthropology. They are the ones to talk to about pottery shards, arrow heads, and the like. Any physical evidence of a preexisting culture could be brought to the attention of an archaeologist. However, anthropologists cover a lot more ground, so to speak. There are cultural anthropologists that study current, existing culture. This is in fact a large field within cultural anthropology. There are even physical anthropologists that study evolutionary changes taking place within humans right now. Neither of these would count as archaeologists though.
Just as in anthropology, as I mentioned earlier, there are several different subspecialties within paleontology. Here is how the University of California Museum of Paleontology breaks it down.
Paleontology is traditionally divided into various subdisciplines:
- Study of generally microscopic fossils, regardless of the group to which they belong.
Paleobotany: Study of fossil plants; traditionally includes the study of fossil algae and fungi in addition to land plants.
Palynology: Study of pollen and spores, both living and fossil, produced by land plants and protists.
Invertebrate Paleontology: Study of invertebrate animal fossils, such as mollusks, echinoderms, and others.
Vertebrate Paleontology: Study of vertebrate fossils, from primitive fishes to mammals.
Human Paleontology (Paleoanthropology): The study of prehistoric human and proto-human fossils.
Taphonomy: Study of the processes of decay, preservation, and the formation of fossils in general.
Ichnology: Study of fossil tracks, trails, and footprints.
Paleoecology: Study of the ecology and climate of the past, as revealed both by fossils and by other methods.
Each one of these can be broken down into even more specific specialties. Paleoecologists can specialize in biogeography, limnology, pedology, tempestology, schlerochronology,and many others. Vertebrate (and invertebrate) paleontologists can specialize in taxonomy, systematics, functional morphology, etc., but I think you get the point. There is far more that can be studied by any individual. paleontology, like any other science, is a team sport.
There are no hard and fast boundaries between these of course. Vertebrate and invertebrate paleontologists can and do study taxonomy, biogeochemistry, paleoecology, and taphonomy, and others all at the same time. Paleontology is highly interdiscplinary and requires knowledge in a lot of different fields. But many scientists tend to spend most of their time in a specific area.
So if you have a question, you will get the most detailed answers from someone in the right specialty. Choose wisely and you will get your questions answered. If you don’t, go to grad school, discover them for yourself and let everyone else know about it.
Tomorrow is the day to see tons of fossils at the Museum of Discovery. Come out and see what Arkansas has to offer in fossils. We have a far more diverse array of fossils than most people realize. Here are a few dinosaurs you will see.
Here are some casts of Allosaurus bones, a foot and a humerus. Allosaurus itself didn’t live here, but its descendant, Acrocanthosaurus, did.
Here is an ischium of an Apatosaur, which did not live here either. But its titanosaur relatives did.
Here are some hands and claws of Allosaurus and Utahraptor, a giant version of Velociraptor.
Not interested in dinosaurs? How about a Smilodon, one of the biggest and most iconic of mammalian predators?
Of course, what I have shown the past few days is only a few things that the University of Arkansas Earth Sciences Department is bringing. The Anthropology Department will also be there with their own fossils. The Arkansas Geological Survey will be there with a cast of the dinosaur, “Arkansaurus” and more. The Virtual Fossil Museum will be present with more than virtual fossils. Not to be outdone, the Museum of Discovery will have a collection of dinosaur skulls on display, which will be part of an upcoming dinosaur exhibit which you won’t want to miss.
The National Fossil Day event at the Museum of Discovery is almost here.Here are a few more things you might see at the event. Here is a cast of a coelacanth, a lobe-finned fish that is closely related to the fish that started the trek onto land, and a mesosaur, an early reptile before reptiles and mammals went their separate ways.
Want something with a bite to it? How about some teeth? Like Megalodon teeth, and a nodosaurid dinosaur, and how about the tooth of a giant ground sloth? What about primitive horse and rhino teeth?
Lots more to see. Come out and have a look. Bring your fossils and compare.
Here are some brachiopods you will see at the National Fossil Day event. They look much like clams, but are unrelated.
Here are some bryozoans, which look like they should be related to coral, but are thought to be more related to brachiopods because they share the same odd feeding structure.
Speaking of corals…
National Fossil Day is October 15th, but the Museum of Discovery, in conjunction with the Earth Science and Anthropology departments at the University of Arkansas at Little Rock (UALR), the Arkansas Geological Survey, the Arkansas State University Museum, the Virtual Fossil Museum, and others (including of course, me) will be putting on an exhibit on October 11th. If you are in the neighborhood, please stop in. there is much to do and see for everyone from toddlers to grandparents and professional researchers.
This week I will be sharing a few photos of the collections at the UALR Earth Science Department as a preview of things you will see. We will start with echinoderms today. These include crinoids, sea urchins, starfish, and an array of others.