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The giant Arkansas fossil catfish
Did you know that Arkansas once had catfish more than three meters long and weighing, depending on who you believe, as much as 450 kg? That makes the world record catfish of today look positively puny.
The proof can be found at the Arkansas Geological Survey. The skull of one such monster is on display in the second floor display case. It was found in 1983 off Highway 79 near Camden. The bones were pulled from the Claiborne Formation, or more specifically, the Sparta Sand.
The Claiborne Group can be found in much of the South-Central part of the state, as well as on Crowley’s Ridge. It is Eocene in age (34-56 Mya). According to the Arkansas Geological Survey, the Claiborne is primarily non-marine and is comprised of mostly fine-grained rocks ranging from silty clays to medium-grained sandstones, with the occasional lignitic coal bed. The shales usually have the variegated tans and grays often seen in terrestrial sediments, with brown and black organic-enriched layers intermixed. Fossils are common from the units, with plant fossils common, as well as trace fossils. Of particular interest here are the reptile and fish bones that have been found here.
The Sparta Sand in particular is a thick bed that can be several hundred feet think. It is a fine to medium-grained sandstone that is typically light-colored, either a whitish or light gray, with thin beds or brown or grayish sandy clay and lignite. It has been considered an important aquifer for the region. The sediment is thought to have been laid down by rivers during a regression of the marine shoreline farther south. In other words, we are looking at the flood plain of a river meandering its way to the ocean, much like southern Arkansas and Louisiana is today. Only back then, the catfish grew much bigger than they do now.
So what do we know of this fish? We know it was a siluriform catfish, most likely in the Ictaluridae family, along with all the other North American catfish. It was probably something like the giant Mekong river catfish and lived in similar environments. The Eocene was warmer than it is now, so it was likely even more tropical than it is today. Beyond that, we don’t know a lot. The fossil has never been fully studied and described as far as I am aware. In 1983, Dr. John Lundberg, a noted expert in fossil catfish and currently chief curator at the Academy of Natural Sciences of Drexel University, corresponded with the AGS about studying it, but thus far, I don’t know what, if anything, came of it.
Getting Antsy for the Answer to last Week’s Mystery Monday?
Last week we posted a new fossil. Were you able to figure it out?
This particular picture is of the ant, Nylanderia vetula, caught in Dominican amber. Dominican amber is from the Miocene, currently thought to be about 25 million years old. The fossil ants from Arkansas are a bit different.
In 1974, ants were found in amber collected near Malvern, Arkansas, from the Claiborne formation, which is listed as being from the Eocene, roughly 45 million years ago (give or take 3 million years). According to the Arkansas Geological Survey, the Claiborne is a series of fine sand to silty clay layers, with interspersed layers of lignite. The lignite and amber are clearly indicative of terrestrial environments, although there are some marine sediments within the formation. A number of fossils have been found in the formation, including fish and reptile bones and teeth, leaf impressions, trace fossils, and of course, wood and amber.
The specific ants that have been found were identified as Protrechina carpenteri. These ants are in the group Formicinae, one of the more common ant groups. Interestingly, the Eocene ants were anything but common. Ants during this time shifted from the earlier ants to a more modern collection of species. They were quite diverse, with Phillip Ward reporting that David Archibald claimed some of them were the “size of small hummingbirds”.
Images of our Arkansas fossil ant are hard to find, as in, I couldn’t find a single image. However, if you want to see the real thing, go to the Harvard Museum of Comparative Zoology, where Antweb.org reports it is being held. Yet another Arkansas fossil in the hands of another state.
Fossil Friday, Revenge of the Serpent
Mystery Monday this week fell on St. Patrick’s Day, so to celebrate, the following image was posted for the mystery fossil of the week.
St. Patrick was well known for driving all the snakes from Ireland, at least so the myth goes. In reality, there never were any snakes in Ireland for St. Patrick to drive out in the first place. But unlike Ireland, Arkansas has always had snakes. Right now, we have a diverse population of snakes, including boasting more different types of venomous snakes than most other states, being one of only ten states that have all four types of venomous snakes in the country (there are roughly twenty separate species, but they all fall into four main groups). Here you may find the copperhead, coral snake , cottonmouth (aka water moccasin), and the rattlesnake (including the Timber, Western Diamondback, and pygmy rattlers). At least we can take comfort that we are just outside the ranges of the Massasauga and Eastern Diamondback rattlesnakes and we don’t have the diversity of rattlers seen in places like Arizona and Texas (which may win the prize for most venomous snakes in the country if both species number and diversity are taken into account).
In the past though, we also had other snakes, including Pterosphenus schucherti, also known as the Choctaw Giant Aquatic Snake, a giant sea snake that lived here in the late Eocene roughly 35 million years ago. The Eocene was a much warmer time. In fact, this period falls at the end of what is called the Palaeocene-Eocene Thermal Maximum. There were no polar ice caps during this time, with at least double the amount of carbon dioxide and triple the amount of methane than what we see now. Because of this, Louisiana was pretty much under water and Arkansas had wonderful ocean front property, along with a lot of swamps and marshes. It is likely the cooling during this period into the Oligocene Period, that caused the extinction event that wiped out these snakes, along with several terrestrial mammals, including a variety of Perissodactyl horse ancestors, artiodactyls (cloven hoffed mammals), rodents, and primates.
This was the perfect environment for a number of different snakes, although we don’t have fossil evidence of many. One that we do have is of Pterosphenus. This snake had tall, narrow vertebrae, indicating adaptation to an aquatic lifestyle. In fact, it probably was not able to support itself on land very well due to its thin body.
Sea snakes today rate as some of the most highly venomous snakes in the world. However, there are nonvenomous ones as well, such as the marine file snake, Acrochordus granulatus, which live in coastal regions between Asia and Australia. Those of today are relatively small snakes, ranging from half a meter to just over 2 meters (2 feet to 7 feet or so). Pterosphenus, on the other hand, reached lengths of 2.3 m to 5.1 m, or possibly larger.
Unfortunately, we don’t know a whole lot about these snakes, other than they were clearly aquatic. The bones that have been found with them, such as whale bones, have indicated marine waters. Fossils of these snakes have been found in eastern Arkansas, in Saint Francis County in the Eocene deposits around Crow Creek called the Jackson Group.