Between classes and school appearances, I have not had the time to write up as complete a description as I would like, so I will do a more complete description of the fossil later. But for now, did any of you think you saw crinoids in the face? If you did, you are correct! This photo was originally published on the Arkansas Geological Survey‘s blog. If you haven’t checked them out, I encourage you to do so.
Crinoids are perhaps the most common fossil found in Arkansas. They can be found in many of the Paleozoic rocks in northern Arkansas in the Ozarks and Ouachitas, although they are most common in the Mississippian age limestones of the Ozarks. All those white rocks along Highway 65 towards Leslie and Marshall are good candidates, although watch out for cars along the highway, please.
Crinoids are often called sea lilies because of their resemblance to plants, but they are actually animals that are related to sea urchins and starfish, so they are far more closely related to you than to any plant. Even though they lived in shallow marine environments during the Paleozoic Era, you can still find them today in deep water along what is called the continental slope. If you swim out into the deep water a long way away from shore and you get to the edge of the continent, you will see a cliff or steep slope descending all the way down to the abyss of the absolute bottom of the ocean. Congratulations, you have reached the continental slope and the last refuge of the crinoids.
It’s another Monday! You know what that means, right? The end of the weekend, an extra dose of coffee to get the day started, and a new fossil for Mystery Monday. Today’s fossil is a very common fossil in Arkansas. Some people think these fossils form a kind of spooky face. Bonus points if you can say where the picture came from. Once I tell you what it is, you should check out all the other cool info they have.
Many people have an issue with scientists, particularly those studying evolution and paleontology, for making statements they feel are pure speculation. I absolutely agree that people should be upfront about what is known and what is speculation. Most scientists ARE generally clear about that. If you ask most scientists, they will tell you what we know and don’t know. That is actually one of the biggest problems that scientists have with almost all of the shows and most of the books written for the public. Those outlets are not clear about what we really know and what we don’t, what is speculation. Most scientists I know work really hard at trying to clarify that sort of thing and get very frustrated when their words are twisted around. Many scientists have refused to work with film crews for precisely that reason. So please don’t blame the scientists. Write to the shows and demand they are clear about their speculations.
Sadly, I wish I could say all scientists act this way, but it is true, not all do. Scientists are only human after all. There are problems with some scientists. Believe me when I tell you that we recognize this and try to stop it. The lab I worked in to get my doctorate had a reputation for being spoilers, as it were, because a large portion of our research involved figuring out the limits of what the data really let us say and then telling others no, you can’t say that because the data do not extend that far. Our work was very much about separating speculation from reasonable interpretation and fact. But we were hardly alone in that regard, it is something most scientists work hard to do. Paleontology is admittedly one of those fields in which it is easy to take the fossils we have and in our excitement try to say too much about them. So we do our best to restrain ourselves and other workers from extrapolating too far. Go to a paleontology conference and you will see that on display in abundance.
Unfortunately, that rarely shows up in material done for the public. The film crews and honestly, most of the public, do not want to hear we don’t know. They want to hear the fanciful stories. Most people get annoyed with scientists when they equivocate and don’t give straight answers. We frequently hear from people, well which is it? Is it this way or that way? If you can’t say with absolute certainty one way or the other, you must not know ANYTHING, when in point of fact, there is a vast difference between not being sure and not knowing anything, I am sure most will agree. But most people don’t want to hear we don’t know with certainty, we can only say this much about it. I have even seen that in my college courses. Many students are uncomfortable with the material I cover in which there are no good answers everyone agrees on. They want definitive answers. A large part of that, I think, is that science is taught in schools very poorly, as a list of facts to memorize, not as a way of thinking and an expanding body of knowledge that is constantly re-examined, with large areas we don’t know yet. In fact, and what makes science fun and interesting for people doing it, is that science is more about what we don’t know than what we do. But happily, I can say that is changing in many areas, with the introduction of more hands-on, exploratory teaching methods.
One of the challenges though, is that many things the lay person thinks are pure speculation are not speculation at all, but are backed up by lots of evidence that there is simply not enough time to go into. Many computer programmers simply tell their clients what they do is magic because to answer their questions adequately would take months of training to even get them to the point they could understand the answer. Would you tell a computer programmer what they are doing is pure speculation simply because you don’t understand it? We aren’t trying to be elitest, there is just a lot of information we don’t have time to transmit. There is simply too much going on, too much data, too much research for anyone to keep track of it at all. Even professionals who try to keep up as part of their full-time job can’t do it. So it would be foolish to think anyone who doesn’t spend most of their time studying the research could possibly have a good grasp of the intricacies and quantity of data. It therefore becomes quite the annoyance when people say you can’t know something when they have no idea how much we do know. Many of those things people say we can’t know have been studied for decades by many people who have spent their lives figuring out how to go from speculation to concrete data and hard fact. Most people don’t realize the extreme levels of simplification it takes to get some concepts across because no one can provide all the data backing up those assertions without having their audience earn a graduate degree in the process.
Is all this me telling you to just trust whatever we say? Absolutely not. But don’t expect to come in on the ground floor and know what is going on at the top any more than you could expect to speak perfect French by catching someone speak a few words on TV. Understand that you are only getting the tip of the iceberg. What you see on TV is a seriously flawed transmission of a few grains of knowledge from a mountain range of data. Learn as much as you can from reliable sources. The more you know, the richer your interactions with professionals and the more in depth we can talk to you. We will be happy to share with you everything we know, that’s our job. But what we tell you is highly dependent on the level at which you come to us and the amount of time people are willing to spend. Also understand the quantity of data is more than any one person can understand, even those whose job it is to do so. That is why we have many people studying problems. No one can have all the answers. That is why we keep asking questions. Being open about what we know and what we don’t allows us the freedom to learn more and shows us the path about where to go next. Scientists don’t leave things at speculation, they try to figure out how can we go from speculation to understanding. But if you want to understand all the steps involved, may I suggest grad school?
I have been working on lectures on early amniote evolution, along with the following reptilomorph and synapsid lectures for my vertebrate paleontology course. We will be getting into dinosaurs and the other Mesozoic animals very soon, hooray! However, in preparing these talks, it has brought to my attention just how prevalent two sites in particular are: Reptileevolution.com and Pteresaurheresies.wordpress.com.
When I did a search for “pterosaur”, Google actually responded by saying “Did you mean pterosaur heresies” and provided images that all but one are either from the site or sites complaining about the site.
This is quite unfortunate. Both sites present an abundance of beautiful artwork done by a stellar paleoartist. There is an abundance of information on the animals and their relationships. All in all, the websites look fantastic and are quite the draw for paleo-enthusiasts.
But it is all wrong.
None of the hypotheses presented on these pages is accepted by virtually any other paleontologist. The techniques used to gather the information is not considered valid and no one who has tried to reproduce the data using the methods have had any success.
I won’t get into details about why the websites are wrong. I am frankly not qualified enough to provide a step-by-step breakdown of the problems (not being an expert in either pterosaurs or basal tetrapods), nor do I really have the time. I will say that many years ago, I heard the author of these websites give a talk about his evidence for a vampiric pterosaur and even as a young undergraduate, it was clear to me that neither the technique nor the conclusions were valid. I found it very unfortunate because the idea of a vampiric pterosaur was incredibly cool and the technique, which involves detailed image study, is useful in many contexts. However, it is very easy to let personal biases enter into conclusion based on these methods, to allow oneself to extrapolate well beyond anything the data can actually support. Oftentimes, those biases are completely unknown to the observer simply due to the way our brains interpret sensory input and modifies them based on past experience. We really do not see everything we think we see, which is why the scientific method requires other scientists examining your conclusions and your methods and trying to poke holes in your ideas. So it is vital to recheck one’s conclusions with many detailed images from various angles and lighting methods and, most importantly, detailed examination of the fossil itself.
So instead, I will point you to articles written by people who are experts in the very animals that are discussed on those pages and what they have to say about them. The first is an article by Dr. Christopher Bennett, who is an expert on pterosaurs. In this article, he discusses the validity of the techniques and discusses specific claims of two pterosaurs in particular, Anurognathus and Pterodactylus. Anurognathus is a very odd-looking pterosaur and is quite aptly named “frog mouth.” Pterodactylus is probably the most famous pterosaur next to Pteranodon and is why so many people mistakenly refer to all pterosaurs as pterodactyls. Dr. Bennett does an excellent job critiquing the science in a professional and readable way.
The second article is a blog post by Darren Naish, a noted researcher and science author that has researched pterosaurs and many other animals who has a deep understanding of both the accepted science and the author of these websites and the work presented therein. Here is what he says: “ReptileEvolution.com does not represent a trustworthy source that people should consult or rely on.Students, amateur researchers and the lay public should be strongly advised to avoid or ignore it.” The emphasis is completely his. The post is quite long and discusses several aspects of the work, discussing the accepted science and the material on the websites that is not accurate, including the techniques used to arrive at the conclusions, both accepted techniques and those by the website author that are not.
The next site is an article by Pterosaur.net, a website devoted to research on pterosaurs by pterosaur researchers. It is a brief article that uses Naish’s article as a starting point and continues on with a discussion of why they think it important for people to know why these sites should be avoided. To quote: “The issue taken with ReptileEvolution.com is not that it exists, but that it’s internet presence has grown to the point that it is now a top-listed site for many palaeo-based searches. Tap virtually any Mesozoic reptile species into Google and either ReptileEvolution.com or the Pterosaur Heresies is likely to be in the first few hits. The situation is even worse for image searches, which are increasingly dominated by the many graphics that Peters’ uses on his sites.” This would not be a problem that the sites are so well known if they were correct, but their prevalence presents a highly flawed version of what scientists really think. People are taking these sites as truth, when in fact they are regarded by professionals as seriously wrong.
Finally, Brian Switek, a science writer who authors the blog Laelaps, which moved from Wired Science Blogs to National Geographic and the now-defunct blog Dinosaur Tracking for the Smithsonian, wrote a piece on the site, in which he urged more paleontologists and paleontology blogs to call out misleading websites like these. In that spirit, I hope I can help some avoid getting a mistaken impression of dinosaur science and help steer them to better, more reliable sources.
* If you are wondering why I say “the author” or “the artist” rather than using the person’s name, it is because I don’t want this to be about the person, but the information. I don’t personally know the author, nor have I ever had direct contact, so I have nothing to say about the person. The work, however, can be and should be open for criticism, just like any other researcher, including my own.
On Monday, we posted this picture of an Arkansas fossil. Were you able to figure it out?
This is a fossil of Calamites (watch your spelling, we want to avoid any calamities). Calamites was a relative of the modern-day horsetails, Equisetum. But unlike today’s horsetails, which are generally only a meter or so in height (although some giant horsetails can grow up to 7 meters or more), Calamites grew up to 30 meters (100 feet).
Equiseta often grow clonally, spreading the rhizomes widely through the surrounding ground, forming large clumps of plants that are essentially the same plant, connected via their roots. Assuming Calamites did the same thing, it has been estimated “they may have been the largest organisms that ever lived.” This group of plants is unique in the incorporation of silica into their stems, giving rise to one of their common names being scouring rushes.
This group of plants first appeared in the late Devonian, but really had their heyday in the Carboniferous Period, although they died out soon after in the Permian. The Carboniferous is so named because most of the world’s coal was formed during this time. The reason for this is because of the difficulty in digesting plant matter. Cellulose, the primary ingredient in plant cell walls and what we call “dietary fiber.” Even today, other than fungi and some bacteria, there is precious little that can break it down. Lignin, the other main component of plant cells walls, otherwise known as “wood,” is even harder to break down.
The only thing that can really digest it is white rot fungi. Back then, there was little to nothing that could eat it. As a result, dead plant matter tended to sit around for a very long time, making it much more likely to accumulate and form coal. Once the enzymes needed to break down lignin evolved, white rot fungi found themselves with a hugely abundant food supply and acted like teenaged football players after a game at an all-you can-eat buffet. And thus ended the Carboniferous Period, in a massive bout of white rot.
Like modern horsetails, Calamites preferred wet soils around rivers and lakes, cropping up all over the world. While they avoided the standing water of the swamps, they flourished any place that regularly got wet, so levees and floodplains were good environments for them. There were no angiosperm trees at that time, what was there were forests of giant Calamites and ferns. Plants called lycopods, most commonly Lepidodendron, dominated the swamps along with the ferns, which were pretty ubiquitous.
Calamites’ modern counterparts are all herbaceous perennials, so Calamites is unique in the group for having a woody trunk. They form extensive underground rhizome networks, growing large clumps of clones from the rhizomes. The leaves form regularly spaced whorls around the stem, creating the horizontal lines breaking up the ridges running vertically up the trunk on Calamites. Inside, the xylem forms rays running from the exterior to the pith in the center. Oftentimes, the pith rots away, leaving a cavity that gets filled with sediment, forming an internal cast, or steinkern.
As a plant fossil, anyone can legally collect Calamites fossils as long as they are not on National Forest property (nothing is allowed to be collected in National Parks and Forests). Good places to look for Calamites would be among the Pennsylvanian (Late Carboniferous) rocks in the Quachitas and Ozarks. While Calamites may be found in rocks of Mississippian (Early Carboniferous) age, the rocks in Arkansas from that age are primarily marine. Good for finding sea shells, but land plants like Calamites are going to be rare, only there as a result of being washed in by a storm or some such. You will be much more likely to find them in rocks like the Atoka Formation on both sides of the Arkansas River Valley. Most of the Ozarks is Mississippian, but much of the Ouachitas is Pennsylvanian, so are much more likely to have them. You might find them in the Hartshorne sandstone (seen best capping Petit Jean Mountain), but plant fossils are rare and fragmentary. You would have better luck in the McAlester Formation overlying the Hartshorne. You can also try the Savanna and Boggy Formations, which are also of Pennsylvanian age.
It’s time for Mystery Monday! Here is a fossil that can be found in Arkansas, but is completely different from anything I’ve put up here before. Let’s see if you have the paleontological fiber needed to solve this puzzle, or do you lack the stomach for it? 🙂
It’s Friday again. Were you able to get the answer to Monday’s fossil?
The skull shown in the picture belonged to Arctodus simus, the giant, short-faced bear (the not-so-giant short-faced bear, A. pristinus, was smaller and lived in more southerly areas than A. simus). Arctodus lived in Arkansas and much of North America during the late Pleistocene, from less than 1 million years ago up to about 12,000 years ago, when most of the large North American Ice Age fauna went extinct. Arctodus was the North American version of the European cave bear, Ursus speleaous. While the European cave bear was a close relative of most modern bears, Arctodus was more distantly related, its only living relative being the spectacled bear, Tremarctos ornatus. It is sometimes considered possibly the largest terrestrial, mammalian carnivore that ever lived, standing over 3.5 m ( 11.5 ft) tall. Even on all fours, it was almost 2 m (6.5 f) at the shoulder. You would have to get at least 4.5 m (almost 15 ft) up a tree to avoid its reach, assuming it didn’t just tear the tree down or shake you out of the tree. It weighed in at a full ton and could run 40 mph (over 60kph). However, that is also the top range of modern Kodiak brown bears, otherwise known as Alaskan grizzly bears. In the wild, the bears don’t usually get over 1500 pounds (although they can), but the largest ever known was a bear in the Bismarck, ND zoo that weighed 2130 lbs at his death and previously weighed possibly close to 2400 lbs, although he was a very fat bear. There is another bear pelt on display at Space Farms Zoo and Museum in New Jersey that is claimed to be from a bear over 12 ft. tall and over 2,000 lbs, but those claims remain unverified are considered by most to be exaggerated. There is another bear that may have been even bigger. Arctotherium angustidens lived in South America about three million years ago and stood almost 3.5 m tall, so similar to Arctodus and the largest of extant bears, but was much more robust, weighing in the neighborhood of 3,500 lbs.
Arctodus is generally known for its long legs and short face. However, research in the past decade has indicated that its legs were neither longer than expected, nor was its face all that short. It was simply big. Like other bears, it is thought to be fairly solitary most of the time. Contrary to many depictions, it was not particularly adapted to running quickly, considering that modern grizzlies can run 30 mph. What may have made people think they were unusually fast is a combination of their size giving them long legs and tracks that have indicated they used a pacing gait, with the legs on the same side of the body moving in unison, rather than in opposition like most other animals. This sort of gait is typically used in animals with longer legs or at faster trots. Camels use it and dogs and cats, among others, do it when maintaining a trot before they break into more of a gallop. However, the pacing gait is not indicative of a fast-running animal, but of an animal that maintains a quick pace for long distances, it bespeaks of endurance, not speed.
Like most bears, Arctodus is thought to have been omnivorous, eating both plants and animals. There have been several hypotheses concerning its diet, from mostly scavenging to hypercarnivorism. It was certainly capable of bringing down large prey, although its limbs were not as flexible as most high level predators, nor were they particularly robust for their size, leading some to think they scavenged, although they would be hard-pressed to compete with giant vultures in scavenging and recent work indicates the tooth structure was not sufficient for chomping through bone. They may have been better suited for foraging plant material with their unusually flexible wrist giving them an almost semi-opposable thumb, much like pandas. This suggests possible tree-climbing to some workers, although Arctodus was a very large animal to be climbing trees. Besides, it typically lived in more open, grassland environments the majority of the time, so it is unlikely to have been adapted for tree-climbing.
They went extinct roughly 11,000 years ago, along with a large number of other large species. A reduction in rich food supplies is thought to have caused the extinction of the large herbivores. This would have placed a great deal of stress on the carnivores, causing increased competition. The dire wolves lost out to the modern grey wolves during this time, chiefly thought to be a result of the gray wolves being able to hunt and subsist on smaller and fewer prey than the larger dire wolves. This same reasoning would apply to Arctodus as well, which had to compete against both wolves and other bears, for a greater percentage of the share to fuel its larger body. On the other hand, evidence for this hypothesis has been lacking in analyses of tooth wear.
If you want to see more of Arctodus, make your way to the La Brea Tar Pits in Los Angeles. many bones of this bear have turned up from the tar and are on display at the Page Museum.
The weather forecast this week is for snow. So in going with the theme lately of Ice Age animals, I thought I would bring you another one for this week’s Mystery Monday fossil. This picture doesn’t have a scale, so I will just say this skull is bigger than yours (under the assumption that all my readers are Homo sapiens or within the same size range, my apologies to the exceptionally macrocephalic).
Mastodon bones have been found throughout Arkansas, although almost all have been found either in northeast Arkansas between Crowley’s Ridge and the Mississippi River or along the Red River in Southwest Arkansas. According to the Arkansas State University Museum in Jonesboro, Arkansas has more mastodon finds than any other state in the mid-south region, with at least 20 different skeletons. Most of the work on them has been done by Dr. Frank Schambach and others of the Arkansas Archaeological Survey, headquartered at the University of Arkansas at Fayetteville, along with members of the Arkansas State University Museum. This particular mastodon was excavated by Dr. Schambach with the help of the Arkansas Archaeological Society along the Red River in Southwest Arkansas, I think in 1987, although I am not sure of the date yet.
Mastodons were related to elephants, although not as closely related to modern elephants as mammoths. Mammoths have also been found in Arkansas, most notably the Hazen mammoth, found in 1965. That specimen was a Columbian mammoth (Mammuthus columbi), a less hairy version of the wooly mammoth (Mammuthus primigenius). They lived across much of North and Central America during the Miocene and Pliocene, although they are known mostly from the Pleistocene in Arkansas, the heyday of the Ice Age, which is when people traditionally think of them living. They were similar in size to modern elephants.
The teeth of mastodons, mammoths and modern elephants tell an interesting story. Modern elephants have a wide diet of vegetation from grass to fruit and tree limbs. The Asian elephant has teeth that are more plate-like in form, making a series of ridges that create an excellent grinding surface. African elephants spend more time in forests and bush lands, with a corresponding higher amount of bushy vegetation in their diet. Their teeth are large, multi-rooted teeth with a series of ridge-like cusps. Mammoths take the plate-like grinding surface to an extreme as an adaptation to the grasslands they frequented. Mastodons, on the other hand, specialized in the opposite direction, with large, prominent cusps suited to a more forested environment and diet. Thus, mastodons and mammoths formed a bracket surrounding elephant ecology.
Work that has recently come out has shed new light on why they went extinct. People have long argued over whether climate change or humans wiped out the megaherbivores at the end of the last ice age. The Overkill hypothesis postulated that early humans hunted them to extinction. There is also the alternative that other actions by early humans contributed to their extinction. However, while there has been plenty of evidence indicating humans did hunt mammoths (e.g. the Clovis people at the Dent site in Colorado), the hypothesis has come under fire for the lack of widespread hunting evidence and timing issues, with research indicating the megaherbivores were already going extinct before humans appeared on the scene. The other hypothesis, climate change, has gotten more support from a study of plant fossils. According to the new data, the early tundra environments were dominated, not by grass, but by forbs, weedy herbaceous plants with more nutrients than grasses. An earlier glaciation 20-25,000 years ago dramatically reduced the abundance of these plants. When the weather warmed up, the forbs increased again, but never approached their previous levels. When the next glaciation hit, the forbs mostly died out, allowing the less nutritious grasses to take over, which greatly reduced the amount of herbivores the land could support. Of course, this does not mean that humans had nothing to do with the extinctions, but it does mean they were likely not the primary cause, more likely simply throwing the last spear into the coffin of the great herbivores.
That’s it for this week. Check back Monday for a new mystery fossil. Have a good weekend.
One of the questions I get often is what should you do if you find a fossil. I have been meaning to write a post discussing that, but I found that someone else had already written a very nice discussion on that very topic. I thought why duplicate the efforts of someone else who has done a fine job already? So instead of writing my own post, I am just going to refer you to their blog post. So without further ado, may I present…