Updates from Panama

Soon after the last post, I headed out to the US, for a short collection trip. During this trip, I visited both the Florida Museum of Natural History (FLMNH), and the National Museum of Natural History (NMNH) as I needed to compare my notes on some fossil cetaceans from the late Miocene of Panama with material housed in those institutions. It was also an opportunity to see my wife as well as spend some quality time with some good friends.

Gainesville, FL
At the Florida Museum of Natural History, I focused on comparing the Panamanian material with several fossil toothed whales in the collections, mainly from the late Miocene and early Pliocene of Florida. There are some interesting specimens at the FLMNH and I was able to make some useful comparisons. I also took some time to look at the exhibits in the museum, which I had not fully done yet.

Me, pointing out to the Florida dugongid triad, of which I wrote early last year (Vélez-Juarbe, et al., 2012). These are part of one of the exhibits at the Florida Museum of Natural History. Not everyday you get to see fossils you've worked on as part of an exhibit. One of those is a new species, so stay tuned!!

Washington, DC
At the Smithsonian in Washington, DC, I had the opportunity to look at both extant and fossil whales. For this, I went to the Smithsonian's Museum Support Center (MSC) which is where the extant whales are housed. If you study whales and dolphins of any kind, this is the place to go! The collection at the MSC allows us to look at more than one individual of a certain species, which gives us a better understanding of differences in the morphology due to age (juveniles vs adults) or sex (males vs females), or just variation within a species. We need to know this, specially when it comes to describing fossil species.

The "whale warehouse", one of the several storage facilities at the Smithsonian's Museum Support Center. If you need to look at skeletons of extant whales, this is the place to go!

The skull of Bohaskaia monodontoides a fossil beluga which Nick Pyenson and myself described last year (Vélez-Juarbe & Pyenson, 2012). Now part of a temporary exhibit called "Whales: From Bone to Book". Make sure you see it if you're in the DC area, its awesome!!

I also looked at several fossil whales, mostly physeteroids, which is the group that include sperm whales and pygmy sperm whales.

Some of the fossil whale I studied at the NMNH. Left: cast of the skull of Aulophyseter morricei, a small sperm whale from the middle Miocene of California (Kellogg, 1927). Right: the skull of Aprixokogia kelloggi, a fossil pygmy sperm whale from the early Pliocene of North Carolina (Whitmore & Kaltenbach, 2008).

Panama
After the US tour, I returned to Panama. Fieldwork so far, has been pretty standard along the canal. One of the recent highlights, was the visit of Bruce MacFadden, who brought a fantastic group of school teachers from California and Florida. We all did some fieldwork along the canal and also went to some localities of the Gatun Formation. At one of the Gatun localities the teachers had prepared an in situ paleontological workshop for a group of local schoolchildren, which was a wonderful experience for all of us involved!

The students were measuring diversity within a meter square grid.

It was not all fieldwork. We also had the chance to go birdwatching along the Pipeline trail in Gamboa, where we did get to see several birds, as well as a lot of other fauna along the trail.

On our hike along the Pipeline trail, led by George Angehr of the BioMuseo, and also author  of Birds of Panama (an excellent reference).

Some of the fauna we saw along the Pipeline trail. Clockwise from top left: leaf beetle (Platyphora haroldi); brown-throated three-toed sloth (Bradypus variegatus); black-tailed trogon (Trogon melanurus); striped rocket frog (Silverstonneia flotator).

So I guess that's it for now. But stay tuned as more discoveries are made in the canal and elsewhere here in Panama!


References
Kellogg, R. 1927. Study of the skull of a fossil sperm-whale from the Temblor Miocene of southern California. Carnegie Institution of Washington Publication 346:1-23.

Vélez-Juarbe, J., and N. D. Pyenson. 2012. Bohaskaia monodontoides, a new monodontid (Cetacea: Odontoceti: Delphinoidea) from the Pliocene of the Western North Atlantic Ocean. Journal of Vertebrate Paleontology 32:476-484.

Vélez-Juarbe, J., D. P. Domning, and N. D. Pyenson. 2012. Iterative evolution of sympatric seacow (Dugongidae, Sirenia) assemblages in the past ~26 million years. PLoS ONE 7(2):e31294.

Whitmore, F. C., Jr., and J. A. Kaltenbach. 2008. Neogene Cetacea of the Lee Creek Phosphate Mine, North Carolina; pp. 181-269 in C. E. Ray, D. J. Bohaska, I. A. Koretsky, L. W. Ward, and L. G. Barnes (eds.), Geology and Paleontology of the Lee Creek Mine, North Carolina, IV. Virginia Museum of Natural History Special Publication 14.

Whale Rescue in the Canal

A little more than a month ago I got an email regarding a fossil find near the construction site of the new canal locks on the Atlantic side of Panama. The photo that came with the email was a bit blurry and with no scale, so it could as well be a small fossil, or even an invertebrate. However, I took the chance as it was, after all, an opportunity to look at outcrops on that part of the canal (most of our work is towards the Pacific side). And so it was, that the spring interns (previously featured here and here) and myself ended up driving towards Colón with the hopes that the fossil was some sort of interesting vertebrate.

One thing I must mention, is that security is very tight in the canal, much more so near the construction sites. So that day, we only had about 20 minutes to look at the fossil and eventually come up with a plan to collect it at some later time, if it was worth it.

And it was! Upon seeing the fossil, I immediately recognized it as a baleen whale jaw. Most of what we could see was a cross section of it (see below), which meant that however long the jaw was, it was going straight into the wall.

Part of a baleen whale jaw, in cross section.

It is not the first time that fossil whales have been found in Panama. A 2010 paper by Mark Uhen of George Mason U. and colleagues (including yours truly) described all that was known of the fossil marine mammals of Panama. Admittedly, it wasn't much, but we were able to confirm the presence of dugongid sirenians, toothed whales (odontocetes) and baleen whales (mysticetes) (Uhen et al., 2010).   Since then, more and better material has been found, including a couple of odontocete skulls that I have helped collect from the late Miocene Chagres Formation (see here and here), as well as other things you'll hear about later this year at SVP.

The new whale mandible was found in the Gatun Formation of late Miocene (12-8 Ma) age (Collins et al., 1996). The Gatun is better known for the abundance of invertebrates (e.g. Woodring, 1957; Hendy, 2013) and for having deposits that represent nursery sites for Carcharocles megalodon (Pimiento et al., 2010). Previous reports of whales from the Gatun include odontocete ribs (Uhen et al., 2010), so finding a baleen whale is a first!

Like I mentioned above, that day we only had a very limited amount of time, and the fossil was worth rescuing. And so it was that over the next month or so I began coordinating with the Panama Canal Authority to go back and collect the fossil. Just last week we were able to go back. This time I had a new group of interns, and over the course of two days we were able to collect the fossil.

The summer interns at the dig site. Chris (at far left) prospects, while Christina and Silvia dig around the whale jaw.  You can see the construction of the new locks in the background.

Unfortunately, due to the nature of the outcrop we only had a limited space and depth to dig. So we had to make the best out of it. Sadly, that meant that if the jaw was longer than our depth limit, we had break it.

The whale jaw, prior to being jacketed.

Me posing with the now jacketed whale jaw fragment. 

The exact affinities of the whale jaw remain a mystery, for now. Hopefully once it is prepared I'll be able to determine what it is. So stay tuned!


References

Collins, L. S., A. G. Coates, W. A. Berggren, M.-P. Aubry, and J. Zhang. 1996. The late Miocene Panama isthmian strait. Geology 24:687-690.

Hendy, A. J. W. 2013. Spatial and stratigraphic variation of marine paleoenvironments in the middle-upper Miocene Gatun Formation, Isthmus of Panama. Palaios 28:210-227.

Pimiento, C., D. J. Ehret, B. J. MacFadden, and G. Hubbell. 2010. Ancient nursery area for the extinct giant shark Megalodon from the Miocene of Panama. PLoS ONE 5(5):e10552.

Uhen, M. D., A. G. Coates, C. A. Jaramillo, C. Montes, C. Pimiento, A. Rincón, N. Strong, and J. Velez-Juarbe. 2010. Marine mammals from the Miocene of Panama. Journal of South American Earth Sciences 30:167-175.

Woodring, W. P. 1957. Geology and paleontology of Canal Zone and adjoining parts of Panama. Geology and description of Tertiary mollusks (gastropods: Trochidae to Turritellidae). U.S. Geological Survey Professional Paper 306-A:1-146.

The Southernmost Atlantic Seacows

Its been a while since I posted news on fossil sirenians. I've been very busy with fieldwork, manuscripts, among other things. The Spring interns have now gone back home. So, while I wait for the arrival of the next round of interns, here's the latest on fossil sirenians.


Where are sirenians found

With the exception of the now extinct Steller's seacow (Hydrodamalis gigas), all extant sirenians have tropical to subtropical distribution, with some species having a notably broad latitudinal and longitudinal distribution (Marsh et al., 2011). But, when we look at the fossil record of sirenians, we see a slightly different pattern of distribution, mostly tied to tectonic and/or climatic events. For example, during parts of the Cenozoic global temperatures were higher than today (Zachos et al., 2001), so you find fossils of sirenians far off their modern range (e.g. Belgium). These climatic variations amongst other physical drivers have played a prominent role in the distribution of seagrasses and seacows (expect more on this in the nearby future).

Nowadays, in the Western Atlantic and Caribbean (WAC) region, the most common and widespread sirenian is the West Indian Manatee (Trichechus manatus) whose range extends from as far north as the Carolina's (with some individuals reaching New England) to northeastern Brazil; another species found in the region is the Amazonian manatee (Trichechus inunguis) which lives in the Amazon basin (see map below). But, it hasn't always been like this. Throughout most of the Cenozoic, dugongids, a group of sirenians are now restricted to the Indo-Pacific region, were the predominant seacow group in the WAC, including multispecies communities in the region (Domning, 2001; Velez-Juarbe et al., 2012a; see previous post on this subject). Fossil of dugongids in the WAC are found in deposits as far north as Maryland, and as far south as Argentina. However, these southernmost dugongids, are poorly known, and have had a somewhat rocky taxonomic history.


From Metaxytherium to Dioplotherium a case of mistaken identity

The most common, and temporally and geographically widespread seacow genus known is the Halitheriine dugongid Metaxytherium. Species of this genus are known from late Oligocene through Pliocene deposits, and are found from the Eastern Pacific, Caribbean, Western and Northern Atlantic, and Western Tethys regions (e.g. Domning, 1988; Sorbi et al., 2012). Therefore it shouldn't have been much of a surprise when Roy H. Reinhart (1976) described a molar from the late Miocene Paraná Formation of Entre Ríos, Argentina as that of Metaxytherium. The importance of this find, lies in that prior to its discovery, the youngest species of Metaxytherium known from the WAC was the middle Miocene M. floridanum, which is not known outside of Florida (Domning, 1988). The Paraná molar was then, the youngest and southernmost record of the genus from the Western Atlantic.

However, species of Metaxytherium display a generally conservative morphology, and because of this, it has had a long, somewhat convoluted, taxonomic history. This is, fortunately, slowly being resolved as most species of Metaxytherium have been re-described (e.g. Domning, 1988; Domning & Pervesler, 2001; Sorbi et al., 2012) and studied in detail within the last 25 years, giving us, paleosirenologist a better idea of the valid species within the genus and variation within each species. Since Reinhart's description, several workers (Cozzuol, 1996; Cione et al., 2000; Domning, 2001) have disagreed with his interpretation regarding the affinities of the Argentinian molar. All of them referring the Paraná molar to Dioplotherium, still a dugongid, but one that belongs to the Dugonginae, a group very different from that to which Metaxytherium belongs. And indeed, the overall morphology of the tooth conforms well with what we know about Dioplotherium, it is in fact, very similar to those of Dioplotherium cf. D. allisoni from the early Miocene of Brazil (Toledo & Domning, 1991). This meant that Metaxytherium may have gone extinct in the WAC at the end of the middle Miocene (Domning, 1988), and that the genus only reached as far south as northeastern Brazil (Toledo & Domning, 1991), or did it?

Left: Map showing the distribution of Miocene seacows throughout the Americas. (ER = Entre Ríos).
Right: Map showing the distribution of extant sirenian in the Americas.
(Click on the map to view larger version.)

New fossils from the Paraná Formation

A couple of years ago I received an email from an Argentinian colleague, Jorge Noriega from CONICET in Diamante, informing me of a new discovery from the Paraná Formation in Entre Ríos. The new fossils consisted of left and right partial maxillae and most of the molars of a single individual (see figure below). At this point I was close to finishing my PhD, which meant that I had look at a lot of specimens and was well acquainted with the morphology of most, if not all Oligocene through Pliocene sirenians. Once I looked at the pictures of the new material, I quickly recognize these as most likely representing a species of Metaxytherium.

Molars of Metaxytherium from the late Miocene Paraná Formation. 1-2) left maxilla and M1-3 in occlusal view. 3-4) right maxilla and M3 (modified from Velez-Juarbe et al., 2012b)

Now, I must admit that dugongid teeth are not the most diagnostic, so figuring out if these actually belonged to Metaxytherium was not an easy and quick task. After a considerable amount of reading, and detailed observations of material from various species of Metaxytherium as well as other dugongids I was confident they belonged to that genus. And so, working together with Jorge and Brenda Ferrero (also from CONICET in Diamante) we took on the task of formally re-designating the fossil described by Reinhart (1976) as well as describing the new material which actually represented a species of Metaxytherium (Velez-Juarbe et al., 2012b). The new Parana molars are quite similar to those of the middle Miocene Metaxytherium floridanum, but, their dimensions are below the range exhibited by M. floridanum and may represents a different species. One of the positive outcomes resulting from this work, was realizing that teeth of dugongids can sometimes be of taxonomic usefulness. We noticed, that the molars of some of the more derived species of Metaxytherium often have additional cusp and/or cuspules, a derived character which is not observed in Dioplotherium or any of its kin (i.e. Dugongines). The contemporaneous presence of both, Dioplotherium and Metaxytherium is not something unheard of. This same duet, occurs in the late Oligocene of Florida, early Miocene of Brazil and possibly in the middle Miocene of California and Baja California (Domning, 2001; Velez-Juarbe et al., 2012a). This again shows that multispecies communities and niche partitioning seems to have been the norm, not the exception, throughout sirenian history.


References

Cione, A. L., M. M. Azpelicueta, M. Bond, A. Carlini, J. Casciotta, M. A. Cozzuol, M. de la Fuente, Z. Gasparini, F. Goin, J. Noriega, G. Scilato-Yané, L. Soibelzon, E. Tonni, D. Verzi, and M. G. Vucetich. 2000. Miocene vertebrates from Entre Ríos Province, Argentina. INSUGEO, Serie Correlación Geológica 14:191-238.

Cozzuol, M. A. 1996. The record of the aquatic mammals in southern South America. Münchner Geowissenschaftliche Abhandlungen A30:321-342.

Domning, D. P. 1988. Fossil Sirenia of the West Atlantic and Caribbean region. I. Metaxytherium floridanum Hay, 1922. Journal of Vertebrate Paleontology 8:295-426.

Domning, D. P. 2001. Sirenians, seagrasses, and Cenozoic ecological change in the Caribbean. Palaeogeography, Palaeoclimatology, Palaeoecology 1:27-50.

Domning, D. P., and P. Pervesler. 2001. The osteology and relationships of Metaxytherium krahuletzi Depéret, 1895 (Mammalia: Sirenia). Abhandlungen der Senckenbergischen Naturforschenden Gessellschaft 553:1-89.

Marsh, H. D., T. J. O'Shea, and J. E. REynolds, III. 2011. Ecology and conservation of the Sirenia: dugongs and manatees. Cambridge University Press, 521p.

Reinhart, R. H. 1976. Fossil sirenians and desmostylids from Florida and elsewhere. Bulletin of the Florida State Museum, Biological Sciences 20:187-300.

Sorbi, S., D. P. Domning, S. C. Vaiani, and G. Bianucci. 2012. Metaxytherium subapenninun (Bruno, 1839) (Mammalia, Dugongidae), the latest sirenian of the Mediterranean Basin. Journal of Vertebrate Paleontology 32:686-707.

Toledo, P. M., and D. P. Domning. 1991. Fossil Sirenia (Mammalia: Dugongidae) from the Pirabas Formation (Early Miocene), northern Brazil. Boletim do Museu Paraense Emílio Goeldi, Série Ciencias da Terra 1:119-146.

Velez-Juarbe, J., D. P. Domning, and N. D. Pyenson. 2012a. Iterative evolution of sympatric seacow (Dugongidae, Sirenia) assemblages during the past ~26 million years. PLoS ONE 7(2):e31294.

Velez-Juarbe, J., J. I. Noriega, and B. S. Ferrero. 2012b. Fossil Dugongidae (Mammalia, Sirenia) from the Paraná Formation (late Miocene) of Entre Ríos Province, Argentina. Ameghiniana 49:585-593.

Zachos, J., M. Pagani, L. Sloan, E. Thomas, and K. Billups. 2001. Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292:686-693.

Return to the Caribbean side of Panama, pt. 2

A couple of Friday's ago, we were set to return to the locality where we had been excavating a relatively large whale skull. Last time we were there we manage to make the jacket around the skull, but the plaster did not dry quickly enough, and we had to leave it, as it was late in the day and the tide was coming in. Unfortunately, due to the change in time of the low tide (happening later and later in the day) as well as other technical problems, we could not go back as soon as we wanted. So we ended up waiting a whole week to return and hopefully finish the job.

A local girl, Pedro, Nicole and Samantha pose next to the jacket.

To our surprise, the jacket held up during the eight days that passed since we made it. Those were good news as it meant that our work and effort from the previous week was not lost and that we didn't had to make a new jacket. Plaster bandages are hard if not impossible to get here in Panama, so I was extremely happy we didn't had to use more than we already had.

Pedro, a local kid, Erik, Nicole and Samantha happily pose next to the large jacket as we get ready to move it to the truck.

We were able to remove the jacket and get it into our truck without further incidents, this wouldn't have been possible without the interns who are doing a great job! To top it off, we even found another tooth associated with the skull. Its not the first one, Aaron had already collected two, which were somewhat incomplete, but hinted at the affinities of the skull. The new tooth we collected is complete, and I can now confidently say that it belongs to a physeterid (a sperm whale)!! Sperm whales are found nowadays in the Caribbean, but their fossil record in the region is relatively poor, with only a handful of reports from a few sites. So this is a fantastic find!

One of the teeth associated with the skull in the jacket. Notice the large root and small enameled crown (to the left of the photo).

Stay tuned, as I'm sure we'll keep finding many other interesting fossils here in Panama.

Return to the Caribbean side of Panama

As part of the PCP-PIRE we not only get to look for fossils and study the geology of Panama along the canal. We also get to prospect and collect at other localities. Yesterday, we made the two hour drive to the Caribbean side of the country, where late Miocene marine units are exposed along the beach. If this sounds familiar, is because I had been there a couple of years ago, where, as part of the Pyenson Lab we went to collect a really nice fossil dolphin skull.

On our way to the locality we had to go through the Gatún Lock, and wait for several ships to go through before we could cross.

Going to this locality means we have to really plan ahead, as the late Miocene deposits will be best exposed at low tides. That also means that we only have about a four hour window to prospect and collect.

As the water recedes, the rock is exposed and its time to prospect!!

Ideally, we can find and collect specimens on a single day (within that 4 hour window), others may take longer, and require to return to the site one or more additional days.

Here Samantha and Pedro work on a project they stated with Aaron several months ago, excavating a large whale skull.

We worked two sites simultaneously this day. Pedro, Samantha and Erik continued an excavation they started several months ago with Aaron. They are digging around what seems to be a large whale skull. Nicole and I were about 15-20 meters southwest of where they were. We were busy digging what seems to be part of yet another whale skull. The skull seems to be broken or at least there's a skull and postcranial elements associated with it, so we collected these in two jackets (see picture below).

Here we take a break and have some snacks and talk with the local kids while the two small plaster jackets (center of the pictures) dry out so we can remove them and take them back to the lab.

We'll go back today to finish off the large whale skull, and who knows what else we'll find. So stay tuned!

Fossil Mammals of Panama

In recent years the efforts to know the fossil terrestrial vertebrates of Panama have been revitalized, in part thanks to the expansion of the canal and the efforts of Panama Canal Project-PIRE in collaboration with the Panama Canal Authority. Vegetation grows fast in the tropics, so good fossiliferous deposits are covered and basically lost within years, even months, of being exposed. The new cuts being made for the expansion of the canal offer a unique opportunity to further understand the geology and paleontology of the area.
Interest in the fossil vertebrates of Panama started when Robert H. Stewart, a geologist with the Panama Canal Company, alongside his assistant, started finding and collecting fossil vertebrate remains in the early 1960's. The fossils were being collected from sediments of the Cucaracha Formation exposed along the Gaillard Cut, one of the artificial valleys that was crucial to the making of the canal. Frank C. Whitmore Jr. (who sadly passes away a little more than a year ago) was then a paleontologist with the US Geological Survey (and expert on fossil mammals) and eventually got involved with the collecting and studying of the Panamanian fossil. He and Stewart published the results of their study in 1965 (Whitmore & Stewart, 1965). Prior to these discoveries, very little was known of the fossil vertebrate fauna of the Central American region, and these were actually the first Miocene fossils found between Honduras and Colombia (Whitmore & Stewart, 1965). Up to that point it was not known wether Central America had been separated from North or South America (some even said both) during the Cenozoic, and if so, for how long? So the discovery of Miocene terrestrial mammals in Panama was a big deal!

The Gaillard Cut and Centenario Bridge in the early morning.

One of the main results of Whitmore & Stewart's study was that the Miocene Panamanian fauna was of holarctic* affinities. That meant that at least through the early Miocene, Panama was connected to North America, even though its geographically much closer to northwestern South America**. The fauna studied by them consisted of turtles, crocodylians, horses, rhinos, oreodonts and protoceratids (which I mentioned in a previous post). The mammal assemblage of this fauna is very similar to coeval faunas in North America.
*a term used for the biogeographic region comprising the northern continents.
**we now know that they remained separated by a marine passageway known as the Central American Seaway until about 3 million years ago (Duque-Caro, 1990; Coates et al., 1992).

Another closer look at the Gaillard Cut. Here you can see sediments of the Cucaracha Formation with Centenario Bridge in the Background.

The fauna described by Whitmore & Stewart was eventually called the Gaillard Cut Local Fauna (Ferrusquía-Villafranca, 1978; Rich & Rich, 1983; MacFadden, 2006). However, the fossils that make up this fauna had not been described in detail. It wasn't until until Bruce MacFadden of the Florida Museum of Natural History took on the task of describing them, 40 years after they had been collected (MacFadden, 2006). As a result, the composition of the Gaillard Cut Local Fauna has changed due to new discoveries, and will most likely continue to do so in the upcoming years. So, stay tuned as I'll cover this subject on the next post.

*Access to this and all other paleontological localities along the canal brought to you thanks to the courtesy of the Panama Canal Authority (ACP).

References

Coates, A. G., J. B. C. Jackson, L. S. Collins, T. M. Cronin, H. J. Dowsett, L. M. Bybell, P. Jung, and J. A. Obando. 1992. Closure of the Isthmus of Panama: the near-shore marine record of Costa Rica and western Panama. GSA Bulletin 104:814-828.

Duque-Caro, H. 1990. Neogene stratigraphy, paleoceanography and paleobiogeography in northwestern South America and the evolution of the Panama Seaway. Plaeogeography, Palaeoclimatology, Palaeoecology 77:203-234.

Ferrusquía-Villafranca, I. 1978. Distribution of Cenozoic vertebrate faunas in middle America and the problems of migrations between North and South America. Instituto de Geología, Universidad Nacional Autónoma de México 101:193-329.

MacFadden, B. J. 2006. North American Miocene land mammals from Panama. Journal of Vertebrate Paleontology 26:720-734.

Rich, P. V., and T. H. Rich. 1983. The Central American dispersal route: biotic history and paleogeography; pp. 12-34 in D. H. Janzen (ed.), Costa Rican Natural History. University of Chicago Press, Chicago, Illinois.

Whitmore, Jr., F. C., and R. H. Stewart. 1965. Miocene mammals and Central American Seaways. Science 148:180-185.

GSA Southeastern Section Meeting 2013

Just a week and a half ago (March 20-21, 2013) was the 62nd Annual Meeting of the Geological Society Southeastern Section, held in San Juan, Puerto Rico. This two day meeting was a great venue, not only to see some interesting presentations, but was also an opportunity to meet colleagues I had not seen in a while. One of the sessions during the first day was chaired by my friend Alvin Bonilla-Rodríguez of the University of Kansas, and myself. The aim of the session, titled: Multidisciplinary Approaches to Caribbean Stratigraphy and Paleontology, was to find out what our colleagues are up to these days. It was both our first time chairing a session, so we were both a little nervous, but I think it went pretty well. We had a great set of talks as well as poster presentations. Overall it was a fantastic meeting, hat-tip to the organizers for doing such a great job!

The title slide of my GSA talk. 

Of course, going to Puerto Rico for a meeting also meant I would stick around for a few days more.
And so I did. It was time to see my family, but also go to the field and revisit some localities.

Friday after the meeting I returned once again to my favorite early Oligocene locality (see previous posts here, here and here). It hasn't rain a lot in Puerto Rico lately, so the exposure was even better as this locality is exposed along the banks of a river. This gave me the opportunity to spend the morning measuring and describing in detail the main fossiliferous section.

The lowermost marine units was remarkable for the presence of the clam Lucina collazoensis (you can see several of them near the center of the picture). 

Overall, the sequence consists of alternating terrestrial and shallow marine horizons. It is in one of those marine horizons where I have collected several fossil vertebrates, including side-neck turtles, sirenians and rodents among others.

The main part of the section, you can see the terrestrial (brownish-redish units) and the marine (grayish units).

Of course, this wasn't the only day I went to the field. The next day I set out to Ponce, in the southern coast of Puerto Rico, where I will meet with colleagues from the Florida Museum of Natural History, as well as others interested in seeing Oligocene and Miocene marine deposits in that area. It was sort of an unofficial post-meeting field trip.

Our first stop in Ponce, where early Oligocene marine deposits are exposed.

Some of the fossils found at this locality. Left, some crinoid stem fragments. Crinoids were once inhabitants of shallow seas, but since the end of the Paleozoic, they are more typical of deeper settings. Right, a shark tooth, probably a carcharhinid. 

After spending a couple of hours at this locality we were ready to move on to the next outcrop. Unfortunately, my field vehicle would not start, and had to get towed back home.

My field vehicle, acting up...

The others, went on (we were on three vehicles), hopefully they found interesting fossils.

I'm back in Panama (it was a very short trip to PR). So stay tuned for upcoming entries on the geology and paleontology of this beautiful country.