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.
paleoaerie 
Thank you for all the time you put in sharing your knowledge. Are there dig sites or an area I can go?
Glad you find it helpful. For dig sites, it depends on what you are looking for. A lot of people collect invertebrate fossils along Highway 65 around Leslie. Most of the roadcuts showing limestone rocks have fossils that can be collected. Don’t collect on National Forest land or private property without permission of course, but collecting along the highway is perfectly permissible. Just take care of cars. There are also several places in Howard and Hempstead County and that region you can collect Cretaceous aged fossils, mostly Exogyra oysters, but there are vertebrate fossils that are not too uncommonly collected as well. If you take a look at my Arkadelphia post, I show a creek where we collected a lot of fossils. If you click on the map, it is easier to read. There are quite a few creeks between the Arkadelphia-Malvern area and Texarkana that commonly turn up shark teeth. We are also trying to get funding to sponsor a dig at the Conard Fissure, an important dig site near Harrison, which was initially investigated by the American Museum of Natural History around 1906, but hasn’t been touched since. They pulled thousands of fossils out of one chamber there, including fifteen Smilodons (saber-toothed tigers), and there are at least a dozen more chambers to investigate. Besides that, important fossils have been found near Crowley’s Ridge and that area could desperately use more examination.
The Central Arkansas Gem, Mineral, and Geology Society hosts field trips every month, some of which are focused on fossil collecting and the group has some avid local fossil collectors. They are very helpful and can be found at http://www.centralarrockhound.org.
You may be interested in this fossil map of Arkansas I posted that shows what types of fossils have been found in what parts of the state.