This week’s Fossil Friday post highlights fossil vertebrae of the boa constrictor (binomial name: Boa constrictor) found in the Las Cascadas (UF 255000) and Cucaracha Formations (UF 237882 and UF 237883). These specimens represent some of the oldest fossil vertebrates from South America dispersing to Central America at 19.3 million years ago.
For images of the fossil specimens and for more information on them, be sure to read the publication on them here.
Head, J., Rincon, A., Suarez, C., Montes, C., and Jaramillo, C. 2012 Fossil evidence for earliest Neogene American faunal interchange: Boa (Serpentes, Boinae) from the early Miocene of Panama. Journal of Vertebrate Paleontology 32: 1328-1334. www.dx.doi.org/10.1080/02724634.2012.694387
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.
This Fossil Friday, we have a tooth from the camelid Floridatragulus dolichanthereus. This specimen was found by Stanley J. Olsen in 1956 at the early Miocene Thomas Farm locality in Florida. Camelid specimens referred to the genus Floridatragulus have also been found in Panama in the early Miocene Cucaracha Formation. F. dolichanthereus belongs to the same subfamily (Floridatragulinae) as Aguascalientia panamensis, which was featured in a previous Fossil Friday post.
For this week’s Fossil Friday, we have a dentary (mandible) of an amphicyonid from the Cucaracha Formation of Panama. This specimen was found near the Centenario Bridge and is Early Miocene in age. Amphicyonids, commonly called bear dogs, were an Old World taxon that migrated from Europe to North America during the Miocene. They are members of the mammalian Order Carnivora along with modern dogs, bears, walruses and raccoons, to name just a few. One of the defining characteristics of carnivorans is their teeth, which include prominent canines and carnassials. The fourth upper molar and first lower molar are termed carnassials and are teeth that are designed to shear meat like scissors.
To find out more about an indeterminate amphicyonid from Panama, read this paper about Miocene mammals of Panama here.
Feldhammer, G. A., Drickamer, L. C., Vessey, S. H., Merritt, J. F., and Krajewski, C. (2007). Mammalogy: Adaptation, Diversity, Ecology. 3rd ed. Baltimore: Johns Hopkins UP. 316. Accessed online at http://books.google.com on Feb. 16, 2015.
This Fossil Friday we are lucky to be showcasing an Early Miocene fossil wood specimen from the Lirio East locality, Cucaracha Formation. To identify the wood, different cuts (sections) were made. Paleobotany Intern Chris Nelson explains, “You need to cut the wood at three different angles: cross section, radial section, and tangential section. The cross section is the one people are most used to seeing (a cut perpendicular to the height of the tree, often showing growth rings if they are present). The radial section is perpendicular to the cross section (parallel to the height of the tree) and ideally goes through the center of the tree’s trunk (i.e. it is a diameter or radius). The tangential section is similar to the radial section but does not go through the center, so it catches the anatomical features at a third angle (a cut that is tangent to a growth ring). After you have those three views, you can examine the anatomy.”
The tree from which this wood came likely belongs to the genus Guazumaoxylon of the family Malvaceae, which includes okra and cotton. A modern relative of this tree, Guazuma, is found throughout the Neotropics. Members of this genus are pioneering tree species, meaning that they are one of the first species to colonize a disturbed area.
To read more about similar fossil wood from the Hodges Hill locality, check out the paper here.
The subject of this week’s Fossil Friday is a rhinocerotid (commonly known as rhinos) that has been found in Florida and Panama called Floridaceras whitei. Rhinocerotids (Family Rhinocerotidae) belong to the order Perissodactyla, the odd-toed ungulates. This specimen of Floridaceras whitei is from the Hemingfordian Thomas Farm locality in Florida, however it is also known from the Gaillard Cut Local Fauna (Cucaracha Formation) of Panama of similar age. This specimen consists of a right dentary with the lower deciduous second through fourth premolars (dp2-dp4), showing that this dentary belonged to a juvenile F. whitei.
If you would like to read more about Floridaceras whitei from Panama, read this paper on Miocene mammals from Panama here.
For the first Fossil Friday of 2015, we are going to look at the crocodylian Centenariosuchus gilmorei. This specimen was found at the Hodges Microsite at the Hodges Hill locality of the Panama Canal Zone. It is from the Cucaracha Formation and is early to middle Miocene in age. This species belongs to the crocodylian family Alligatoridae, which includes alligators and caimans, and according to phylogenetic analysis, it falls within the caiman subfamily (Caimaninae). Caimans, like alligators, have a low salinity tolerance, preventing them from living in marine habitats. However, the presence of this fossil crocodylian with South American affinities in Panama before the connection of North and South America suggests that there might have been a marine dispersal of caimans.
To learn more about this specimen and the implications of its discovery, read the publication about it here.
It’s Fossil Friday again and this time I would like to show you a specimen of a three-toed horse called Anchitherium clarencei. It was found at the Centenario Bridge Locality of the Gaillard Cut in Panama (Cucaracha Formation). It is from the middle Miocene and is about 18 to 15 million years old. Although this species was found in North American localities such as those in Nebraska and South Dakota, the discovery of this specimen extended the range of this species down to the ancient Neotropics. The low-crowned (brachyodont) dentition of this fossil horse suggests that it was a browser, eating the leaves of plants that grow higher off the ground such as shrubs and trees (as opposed to grazers, which eat grass and other low-growing vegetation).
To learn more about this specimen, read the publication about it here.
This Fossil Friday I would like to introduce you to Rhinoclemmys panamaensis. This specimen was collected from the Cucaracha Formation under the Centenario Bridge and is early to middle Miocene in age. The genus to which this species belongs (Rhinoclemmys) is commonly called the Neotropical wood turtles and the members of this genus are the only living representatives of the family Geomydidae in the New World (although they have great diversity in the Old World).This species is distinguished from other members of the genus by its large size, and it might have looked most like the extant black wood turtle, or black river turtle, Rhinoclemmys funerea.
If you would like to find out more about this specimen and other turtles from Panama, read the publication here.
We would like to welcome the Fall 2014 cohort of PCP-PIRE field interns back to the Florida Museum of Natural History. After over three months of fieldwork, Hannah, Daniel, Adam, and Lillian returned from Panama this week and will be working at FLMNH until December 19th. They will be processing fossils from Panama and doing fossil preparation. The interns have started off by helping prepare a lumbar vertebra of a fossil rhinoceros from the Cucaracha Formation. The vertebra has been broken into several pieces and the interns are cleaning the pieces so that they can be put back together later. It’s quite a change from working out in the field in Panama, but we are happy to have them back and to have their help here at the museum!