UF 243751, an artiodactyl tibia. Photo © VP FLMNH.
For this week’s Fossil Friday post I present an artiodactyl tibia, perhaps one of a peccary (Family Tayassuidae) or a protoceratid (Family Protoceratidae). The curvature and the morphology of the end that articulates with the astragalus along with other features strongly suggests it belongs to an artiodactyl, however it was not found in association with other elements, like teeth, that could pinpoint an identification. This specimen was found in the upper Culebra Formation and is early Miocene in age.
To learn more about this specimen, read its description in the paper referenced below on peccaries found in Panama.
MacFadden, B.J., Kirby, M.X., Rincon, A., Montes, C., Moron, S., Strong, N., and Jaramillo, C. 2010. Extinct Peccary “Cynorca” occidentale (Tayassuidae) from the Miocene of Panama and Correlations to North America. Journal of Vertebrate Paleontology 84: 288-298. doi: 10.1666/09-064R.1
A few weeks ago, when we were driving to one of our dig sites, we noticed a dip in the road that hadn’t been there the previous week. When we returned to the site the next week the dip was lower by at least six inches. The following week I decided driving down that road was not in our best interest but we wanted to investigate. We were able to document cracks and fissures that were several feet long and 4-12 inches wide. The next week there were men surveying the area and the week after that there were excavators and backhoes. I had read about the massive landslides during the construction of the canal and was aware that due to the geology of the area they are an ongoing problem. It was fascinating and I have to admit a bit disconcerting to watch the progression of the landslide and the remedial measures that were taken in response. I was so intrigued I did a little bit of research.
Landslides have always been a problem in the Panama Canal, most notably in the 13-km long section at the southern end of the canal known as the Culebra Cut (also known as Gaillard Cut). The special wonder of the canal is Culebra Cut. It cuts through the continental divide and is the high, hard rock basaltic slopes and the lower, soft shale/clay slopes of the Cucaracha and Culebra Formations that can be seen in picturesque photos of the canal. All the rain and humidity softens the shale into mud and clay. The instability of the mud and clay results in continual landslides. David McCullough in “Path Between The Seas”, his famous book about the building of the Panama Canal, states that all technical problems were small compared to the slides in the cut. Workers on the canal would arrive in the morning and months of digging, as well as equipment, would be completely wiped out by thousands of cubic yards of dirt and rock from slides. The massive slides in the cut also played a big part in the French Canal Company’s inability to complete the canal.
In 1915 the second year of operation, the canal was hit with two major landslides that struck simultaneously. Both the east side and west side of the Culebra Formation slid, resulting in the closure of the canal for seven months. In 1986 a geotechnical advisory board was formed after a major reactivation of the East Cucaracha slide encroached into the navigational channel of the canal and caused a closure of twelve hours.
In 1988 a report was issued by Luis D. Alfaro on the risk of landslides in Gaillard Cut. He researched all of the slide events that were documented up to 1986, thirty-one in all. In his report he suggests dividing the cut into zones of relative uniform geological environments to help monitor and document movement. We use these zone names at our dig sites. Today the slopes are monitored constantly through instrumentation and field inspections so remedial measures can be implemented if movement is detected.
The good news for us is that there is now a newly scraped-clean excavation site for us to investigate for fossils. We went there twice last week and discovered shark teeth, croc teeth, and a bunch of invertebrate fossils.
UF 271625, the left mandible of Paratoceras orarius. Photo © VP FLMNH.
For this week’s Fossil Friday, we have a newly identified protoceratid called Paratoceras orarius. This protoceratid is the smallest member of the informal protoceratid subfamily “Protoceratinae.” This specimen was found in the upper Culebra Formation and is early Miocene (He1, or early Hemingfordian North American Land Mammal Age [NALMA]). The specific name “orarius” means “estuarine” or “coastal,” which is the inferred environment for the upper Culebra.
If you would like to learn more about this specimen, read the publication that includes it below! Be sure to check out our other Fossil Friday protoceratid, which was renamed as a new species (Paratoceras coatesi) according to the same paper!
Rincon, A. F., Bloch, J. I., MacFadden, B. J., Jaramillo, C. A. 2015. New early Miocene protoceratids (Mammalia, Artiodactyla) from Panama. Journal of Vertebrate Paleontology. doi:10.1080/02724634.2015.970688. New early Miocene protoceratids (Mammalia, Artiodactyla) from Panama.
UF 244434, the left half of the skull of Culebrasuchus mesoamericanus. This is a left lateral view of the skull, which gives us a look at the animal’s teeth. (Photo © VP FLMNH)
This Fossil Friday we have a caiman (Family Alligatoridae, Subfamily Caimaninae) named Culebrasuchus mesoamericanus. This specimen was found by PCP PIRE Ph.D. student Aldo Rincon on March 13, 2009 at the El Lirio Norte site of the Culebra Formation, making it early Miocene in age. It is the sister taxon to all other caimans, making it the first documented taxon to have diverged in the caiman evolutionary lineage. Because of this, this specimen can help us learn more about the divergence of alligators and caimans.
To learn more about this specimen, read the publication about it here. You can also read an eNewsletter article on other fossil crocodylians from Panama here.
An artistic rendering of Culebrasuchus mesoamericanus. (Artwork © Danielle Byerley)
Hastings, A., Bloch, J., Jaramillo, C., Rincon, A., MacFadden, B. 2013. Systematics and Biogeography of Crocodylians from the Miocene of Panama. Journal of Vertebrate Paleontology 33: 239-263.
UF 262197, the centrum of a lamniform shark. (Photo © VP FLMNH)
This Fossil Friday we have a fossil centrum of a lamniform shark from the Lirio Norte locality of the Culebra Formation, which is early Miocene in age. The couplets of circular bands radiating out from the center, similar to tree rings, are believed to show annual growth. Chondrichthyans of the order Lamniformes first appeared in the Cretaceous Period and can still be found in the Atlantic, Pacific, and Indian Oceans of today. Lamniform sharks live mainly in tropical waters but can also be found in temperate areas, and they can live at depths ranging from shallow intertidal zones to as deep as 1600 m. Famous lamniform sharks include the extinct Carcharocles megalodon and the modern great white shark Carcharodon carcharias.
To read more about this fossil and other sharks from the Miocene of Panama, read the publication that includes this specimen here.