Trip to Chile, pt. 4

After some fieldwork (see previous post) it was time to do some preparation of the material we collected. We did some preliminary prep work at the Cabañas, but most of it was done over at the Museo Paleontológico de Caldera. There was also a lot of additional material collected over past expeditions, and we wanted to take good publication quality photos, specially of the material from Cerro Ballena.

Members of the expedition get some initial prep work done on some of the material we collected over the past few days.

More prep work, this time at Museo Paleontológico de Caldera. Cony and Carolina talk about fossil billfishes, while Ana and David are busy preparing pinniped material.

 Luckily, before we headed back to Santiago, we had time for one more trip to the field. This time we went to some Neogene badlands, that have yielded remains of sharks, cetaceans, pinnipeds and penguins. Our time was limited, but was still fun to be out in the field one last time.

Neogene badlands of the Atacama, even with less plant life than the ones I visited earlier in the year in Baja California Sur. In stark contrast with what I usually deal with in Puerto Rico.

One of several shark teeth we found. This one hints at the age of the deposit.

One last view of the Atacama, as the sun settled and we headed back to Caldera and to Santiago the next morning.

The trip is not over, more to come, so stay tuned!

Go read previous installments of this series: Part 1, Part 2, and Part 3.

Also, go see Nick's here, here, here and here.

Trip to Chile, pt. 3

Like I mentioned in the previous post, we returned to the Cerro Ballena site. There we looked for fossils that might still be exposed in the outcrop. We didn't find much, but we did found some interesting stuff.

David, Nick and Roberto, dig a baleen whale vertebra in Cerro Ballena. Several, nearly complete skeletons were previously collected at this locality and are waiting to be prepared at the Museo Paleontológico de Caldera.

An interesting find was the remains of a billfish. Here David, Cony and Roberto collect the remains, while Nick and Carolina were taking notes on the locality and horizon. Missing from the picture are Ana and Mario, who were in another part collecting remains of the aquatic sloth, Thalassocnus.

We also visited some other localities, including one that yielded remains of Pelagornis chilensis amongst other interesting stuff!

Ana, David and I as we walk to another sites where remains of other marine vertebrates have been collected.

Unfortunately, poachers also know of these sites and go looking for shark teeth and other fossils to sell, which is illegal! So in many places we knew the location of bone beds because of the shattered remains of material thought as uninteresting to poachers.

The example above show some penguin bones that were left behind by poachers. These was actually my first encounter with penguin bones in the field!

More posts to come, so stay tuned!!

Also, go see parts 1 and 2 of this series!

Trip to Chile, pt. 2

Things have been pretty busy over the past several days. Between work at the museum in Caldera, fielwork and spending time working on manuscripts I haven't really been able to post as much as I wanted to. Anyways, like I mentioned on the previous post, we've been spending some time studying fossil material at the museum during the day, while in the afternoon we work on manuscripts, abstracts and the like.

Afternoon in the cabaña after a long day of data collecting. Mario (left) prepares the fire, while Nick, Roberto and Carolina work on manuscripts.

One of the benefits of staying in a coastal town is the fresh seafood, which we buy at the market and then cook it ourselves. Just because we are on the field it doesn't mean we have to eat poorly!

Fresh albacore tuna fillet and shrimp and veggie skewers. It was delicious!!

We've also been out in the field. We revisited the Cerro Ballena site (above), as well as some other localities. More on this on the next post, so stay tuned!

You can see the first part of this series here.

Trip to Chile, pt. 1

So a few days ago,  Nick and I arrived to Chile, where we'll be for the next couple of weeks. The purpose of this trip, is to look at collections and visits Cerro Ballena and some other localities in the Atacama region. Some of our colleagues were waiting for us in Santiago, David, Carolina, Roberto and Anita who live there, and Mario Cozzuol who had arrived earlier in the week from Brazil. That afternoon, we headed out to Caldera, in the northern part of the country.
We are staying in some lovely cabañas, with a nice view to the Bahía de Caldera and the city.

The view at night from the cabañas.

At the cabañas, talking with the owner.

The next morning we visited the Museo Paleontológico de Caldera, where we met with another of our colleagues, Mario Suarez. At the museo we spent the day looking at the material collected from Cerro Ballena and nearby localities. The fossils from this site includes a wealth of marine mammals, mostly whales and dolphins, but also, aquatic sloths (more on that later)!! 

Here's a view of some of the material collected from Cerro Ballena, nearly each one of those jackets have remains of baleen whales!!

So, stay tune for more upcoming entries from this trip. Also, go over to the Pyenson Lab where there will be posts about this trip as well.

Dispatches from the field: Baja California, Pt. 8

Today, we set out to pop the jacket that we made yesterday afternoon. While the humidity from the night before dried, some of us kept working on smaller or isolated bones. Others went to town to make phone calls and arrange accommodations for our stops on the way back to Ensenada the next day.

It was a lovely morning to dig bones, as well as for surfing (you can see a surfer to the right). Daryl and Ehecatl take care of some isolated elements while the jacket dries.

We started digging around the jacket with our picks and hammers to remove it. One of the locals, Cal, offered to help us with more advanced technology.

The jacket, popped and ready for capping. This and all the other fossils we collected will go to the Universidad Autónoma de Baja California Sur. Later this year, hopefully, we'll get some of the material on loan so we can start describing it and publishing on the interesting finds that resulted from this trip.

After one last look at the bay we headed out to begin our four day trip back, first to Ensenada, then to Los Angeles.

For past entries of this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Dispatches from the field: Baja California, Pt. 3

Dispatches from the field: Baja California, Pt. 3.5

Dispatches from the field: Baja California, Pt. 4

Dispatches from the field: Baja California, Pt. 5

Dispatches from the field: Baja California, Pt. 6

Dispatches from the field: Baja California, Pt. 7

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 7

So we continued more or less where we left the previous day. We set out to establish the limits of the bone concentration, getting it ready for jacketing.

This is the bone concentration that we jacketed latter that day. They're mostly sirenian ribs, but there's also a humerus (you can see it towards the center of the block).

Among the most interesting fossils that we found in the bone bed this day was this fragment of baleen whale mandible. More specifically it seems to be that of a herpetocetine, an extinct group of (somewhat small) baleen whales. 

Ehecatl, Gerardo and Daryl dig out smaller isolated bones from the bonebed while Fernando and Larry begin jacketing the block with the bones (seen above).

The view from where we were staying. If you click on the picture you can spot the jacket (towards the center left). Tomorrow we'll remove it and wrap things up.

For past entries of this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Dispatches from the field: Baja California, Pt. 3

Dispatches from the field: Baja California, Pt. 3.5

Dispatches from the field: Baja California, Pt. 4

Dispatches from the field: Baja California, Pt. 5

Dispatches from the field: Baja California, Pt. 6

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 6

After a day in La Purísima we were ready to keep digging at the bonebed we found several days ago.

Fernando (on the left) works on some cetacean bones, while Daryl (center) and Ehecatl (to the right of Daryl) remove sediment from around some sirenian bones. Larry (upper right) removes overburden.

As you can see in the image above, bones are sometimes jumbled together. Here's are two dugongid sirenian ribs and an atlas.

One of the most interesting finds of the day was this crocodylian cervical vertebra that I found. We started to find croc teeth around some of the sirenian bones. Then latter on this vertebra, some big kind of croc was lurking in Baja California during the early Miocene!

The field team (from left to right: Gerardo, Larry, Daryl, Fernando and Ehecatl) pose in front of a concentration of sirenian bones that we are preparing to jacket in the next couple of days. This so far, has been the most productive locality.

For past entries of this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Dispatches from the field: Baja California, Pt. 3

Dispatches from the field: Baja California, Pt. 3.5

Dispatches from the field: Baja California, Pt. 4

Dispatches from the field: Baja California, Pt. 5

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 5

This day we headed to La Purísima, to look at more early Miocene outcrops. Specifically we wanted to relocate the type locality of Dioplotherium allisoni, a large-tusked dugongine that is known by the type, a fragmentary mandible, and some referred specimens from California. We still know very little of the morphology of this animal and would like to find more of it.

On the way there, we stopped at a locality where the late Oligocene San Gregorio Fm. and the early Miocene Isidro Fm. are exposed. (above).

Sirenian ribs as well as a variety of fish teeth were quite common in the basal conglomerate (just above my rock pick) of the Isidro Fm. (above).

After our stop to look at the contact between the San Gregorio and Isidro formations we continued our way to La Purísima in search of the type locality of Dioplotherium allisoni. To our luck, Kilmer (1965) in his description of the species, provided a very detailed description of how to get the the locality, that plus our colleague from UABCS, Gerardo González, knew the way as he had been to the locality on a previous occasion.

The type locality of Dioplotherium allisoni in La Purísima (above). Something that Kilmer didn't mention was the the vast majority of the sirenian fossils were inaccessible as they occur nearly exclusively on the bottom of the bed that forms the ledge.

The bottom of the ledge (above). Click on the picture and you'll see some of the sirenian bones in the layer (mostly ribs).

Luckily for us, parts of that bed were exposed at more workable levels. Some of us actually found some bones, and not just the usual sirenian ribs and vertebrae, but we found two scapulae, probably belonging to the same individual! One of them, seen below, had something else in the matrix. When I turned it around there was a desmostylian molar fragment, the first one we know about from this formation!! So with that, I have actually found and collected nearly one of every group of marine mammals (at least the ones from the northern hemisphere)!

One of the sirenian scapulae from La Purísima, kind of small compared to other sirenians, a juvenile? a small species of sirenian? It remains to be sorted out!

More entries to come, so stay tuned!!

For past entries of this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Dispatches from the field: Baja California, Pt. 3

Dispatches from the field: Baja California, Pt. 3.5

Dispatches from the field: Baja California, Pt. 4

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 4

Having almost finished at the locality in the bay we headed inland, to look at additional exposures of the early Miocene Isidro Formation. We went to an area called Mesa El Aguaje. There we could see the Isidro Formation (the light colored units) overlain by the volcanics of the Esperanza Basalt (the dark colored rock over the Isidro).

Its hard to decide where to look for fossils when there are such extensive outcrop. So we decided to go along a dry riverbed, where on the sides we could see the exposures of the Isidro. At one point we saw some bones, so we started to dig.

Our efforts paid well, we found a fragment of mysticete jaw and part of a pinniped forelimb and many shark teeth. If you click on the picture for the larger version you can see where we were digging.

For now we're done at this locality as we still have to go to La Purísima to look for the type locality of Dioplotherium allisoni. So, stay tuned!!

For past entries of this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Dispatches from the field: Baja California, Pt. 3

Dispatches from the field: Baja California, Pt. 3.5

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 3.5

Almost forgot about this. One of the interesting things that we see when we walk along the shores of the Pacific Ocean in this region is marine vegetation that has washed on the shore.

To the left (in green) is Zostera a seagrass which is widely distributed across the world, including Baja California. Kelp, the long brown one (with the Zostera tangled in its base), is a brown algae that also grows in this region.

Dugongid sirenian, which inhabited this region during the early Miocene most likely ate a variety of marine vegetation. Species, like the dugongine Dioplotherium allisoni, probably fed on seagrasses, whereas the hydrodamaline Dusisiren reinharti, likely fed on kelp, both species are known from the . So the interesting thing is that nowadays we still find the same, or at least very similar, food source that these sirenians used. So the seacows are gone, but the food remains the same.

Previous entries in this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Dispatches from the field: Baja California, Pt. 3

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 3

Today we set out to collect the partial mandibles that were next to the skull that we collected yesterday. We are still not sure which taxon it is (we have some ideas) but to know for sure we'll have to wait until the skull is completely freed from its rocky tomb. But first, we decided to do some prospecting to the east of where the sirenian skull was.

We didn't find anything in the units east of the sirenian skull site so we decided it was time to collect the mandibles. Also, there were some postcranial material that we had started to collect, but with the excitement of finding a skull, they had been neglected. Well, not any more. After this we were supposed to be done with this locality, and could get ready to head out to other localities we've plan to go.

As it sometimes happens, our plans changed. After collecting the fossils we set out to review the stratigraphy of the section we've been prospecting, actually, some of us, Larry and Fernando, had done it, and they wanted our opinion on it, and we could also know exactly how to refer to the units where we were collecting our specimens. At the beginning, near our camp, I stayed behind digging a rib, from one of the lower beds of the formation, after a while I stopped and joined the others, but keeping in mind that on the way back I wanted to collect the rib. So, on the way back, I started digging the rib and to my surprise found something even better next to it. Part of a sirenian skull! Another one!

The fragment that I found consists of part of the left maxilla (see the molar in the maxilla, above), and as I and some of the others kept digging more stuff kept coming out. As the sun settled we kept finding more and more bones along this one bed, next to the sirenian maxilla there were other cranial material most likely belonging to the same individual, obviously the sirenian was juvenile as the skull is disarticulated. Other fossils that we've collected so far include a baleen whale vertebra and some dolphin vertebrae, so in one small spot we've got three different marine mammals. It was another good day of collecting today!

Previous entries in this series:

Dispatches from the field: Baja California, Pt. 1

Dispatches from the field: Baja California, Pt. 2

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

Dispatches from the field: Baja California, Pt. 2

Having finally made it to San Juanico late Tuesday night, we were finally settled near our field localities. We are staying at a bay that looks to the southeast, so we get to see the sunrise over the Pacific ocean.

We were joined today by Gerardo Gonzalez-Barba of the Universidad Autónoma de Baja California Sur and three of his students, all the material collected will eventually end up in the collection at that institution under his care. Some of the outcrops we'll visit are right along the shore, walking distance from where we are staying. Here the early Miocene San Isidro Fm. is exposed (see picture below, in the background). In the foreground you can see pillow lavas, part of a large lava flow north of the bay. The bay was formed by the differential resistance to erosion of the two rock types, the more resistant pillow lavas form the promontory, while the sedimentary rock is being eroded by the ocean.

We've had some success so far, having collected quite a number of shark and ray teeth as well as marine mammals, including some pinniped bones, part of an odontocete cranium and a nearly complete sirenian skull!!!

Above: In the background Daryl finishes the jacket on the sirenian skull (it was his birthday so he was really happy to collect a skull of his favorite group of sirenians), Fernando of the UABC is helping him. In the foreground, Larry ponders into the distance, is he thinking of marine mammals, bungalows or just enjoying the sunset... who knows.

Previous post in this series:

Dispatches from the field: Baja California, Pt. 1

Fieldwork in Baja California was made possible through an NSF EAR grant to D. P. Domning & L. G. Barnes. The text in these posts reflect my own opinion and not those of the granting agency or institutions to which I’m affiliated.

A river runs through an Oligocene sea: parte III

So, keeping up with stuff I’ve collected at the Río G locality (for previous entries about this locality go here and here), I bring you some of the sirenian material that I collected last January. It is not much, but it adds to stuff I’ve collected previously (as you’ll see).

In tropical regions, a lot of times, good outcrops are along riverbanks. Puerto Rico is no exception and that is why the Rio G locality is so good, the exposure is kept “fresh” because of the nearly constant river erosion. Of course the drawback is that fossils are also lost if nobody visits these type of localities at least once a month or after big rainstorms (at least that’s what I used to do).

The picture above shows one such example. I spotted this bone fragment on the wall, very close to water level (a little more than half a meter). And, as you can see in the inset, the surface facing away from the rock looks freshly broken. I did collect the fossil, and unsuccessfully looked for additional fragments nearby.

Above is the picture of the fossil, in dorsal view (anterior towards the top), and the interpretative drawing. As it turns out the fossil was part of a sirenian skull. What was left of the fossil, is the anterior part of the frontals (Fr) and the nasals (N), the supraorbital processes of the frontals are missing. The convex frontal roof and shallow nasal incisure (the concave area between the frontals) are some characters that identify this fossil as belonging to a halitheriine dugongid. In fact, it is very similar to the same part of a much more complete skull that I collected from that locality several years ago (see below).

The figure above shows the more complete skull. A and B show a close-up dorsal view (anterior towards the top) of the area that was preserved in the fragmentary fossil. C is a dorsal view of the skull (anterior to the right) with the outline of the enlarged area in A. As you can see the frontal and its relationship with the nasals look much the same as the fragmentary fossil. It also displays a shallow nasal incisure at the posterior end of the mesorostral fossa (MRF) and convex frontal roof. In the more complete skull the premaxilla (Pmx) partially cover the nasals and the supraorbital processes (SOP) are preserved. (In A and C it is missing the left nasal process of the premaxilla which is loose and needs to be re-attached, but I was able to put it in the drawing).

I’m pretty certain that the fragmentary fossil belongs to the same species as the more complete specimen; it was a pity that part of it was lost previous to it being found. If you’re well acquainted with extinct sirenians, you can probably guess what genus this skull belongs to. So, go ahead and make a guess!

A river runs through an Oligocene sea: part II

This is the first post of the year and, hopefully, more will follow. Anyways, today I bring you a brief overview of fieldwork that I did back in January while I was in Puerto Rico. I had written in a previous occasion about this locality (you can read part I here) and unlike back then, I did find some vertebrate fossils.

The picture above shows one of the most productive outcrops along this locality. As you can see there are about four distinct units. I and III are paleosols (ancient soil horizons) whereas II seems to be shallow marine/brackish and IV shallow marine deposits. Unit II has yielded good fossils in the past, including a sirenian skull and associated axial skeleton, croc teeth, rodent teeth and some nurse shark teeth (gynglymostomatids) (update: you can read about newer discoveries at this site and other nearby ones here, here, here, here, and here). These beds are part of the San Sebastian Formation of early Oligocene age, which in the past have yielded other interesting fossils such as the sirenian Caribosiren turneri (Reinhart, 1959) and the gharial Aktiogavialis puertoricencis (Vélez-Juarbe et al. 2007), among others.

Like I mentioned in the intro, this time around I did find some cool stuff!

In the photo above you can see a closeup of unit II showing some of the fossils as I found them and before I started digging. The red circles are for turtle shell fragments while the green is a sirenian rib. Yes, I know, they are somewhat difficult to see but click on the picture and look carefully, you’ll see them.

The sirenian rib was isolated and easy to collect; it is fairly normal to find isolated sirenian ribs in the San Sebastian Fm and other Oligocene and Miocene localities in Puerto Rico. In contrast, while digging around the turtle shell fragments shown in the picture above, I kept stumbling upon more fragments, until it was apparent that this represented a partially disarticulated turtle shell. Not only that, but there was also an associated left pelvis (shown in the picture below), not bad!!

One of the first posts on this blog was an overview of what's known of the fossil side-neck turtles from Puerto Rico. In it I mentioned that some pelomedusid (a more technical name for side-necks) material from the San Sebastian Fm. had been described by Wood (1972) as an unknown taxon. In fact, Wood (1972) not only described an incomplete shell and plastron but also an associated pelvis. Maybe this material I collected represents additional specimens of that unknown taxon. However, comparison with the description as well as with other turtle fossils from the overlying Lares Limestone will have to wait until after the specimens are prepared (you can get a glimpse of the preparation process here). Below you can see the jackets with the specimens inside.

Preliminarily, I am quite certain that this San Sebastian turtle is a pelomedusoid just by the morphology of the pelvis. Also, there was one other fossil collected that day (is in the jacket in the far left), which was both interesting and frustrating, but I'll leave that for next time!

Recommended Literature

Reinhart, R. H. 1959. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences 36(1):1-146.

Vélez-Juarbe, J., C. A. Brochu, and H. Santos. 2007. A gharial from the Oligocene of Puerto Rico: transoceanic dispersal in the history of a non-marine reptile. Proceedings of the Royal Society B 274:1245-1254.

Wood, R. C. 1972. A fossil pelomedusid turtle from Puerto Rico. Breviora 392:1-13.

This post was updated April 28, 2020

A day in the field, Tertiary

This time our field area is in northern Puerto Rico. We decided to visits a couple of outcrops of the Late Oligocene Lares Limestone. If the name of the formation sounds familiar you either know about the geology of Puerto Rico or, have read about it on a previous post.

One of these localities (see picture below), I have visited at least since 2000, and up until very recently, we thought that the only formations present there were the Early Oligocene San Sebastián Formation and the overlying Lares Limestone. Now, thanks to new information regarding the stratigraphy of the Tertiary limestones of the north coast of Puerto Rico (Ortega Ariza, 2009), we know that in this locality, overlying the Lares Ls, there are also units of the Montebello Limestone. The age of the Lares Limestone and Montebello Limestone were designated as Late Oligocene – lower Early Miocene and upper Early Miocene, respectively (Seiglie & Moussa, 1984). New data, using strontium isotopes obtained from tubes of the pelecypod Kuphus incrassatus, seems to indicate, instead, that both formations span the Late Oligocene (Johnson et al., 2006; Ramírez et al., 2006; Ortega Ariza, 2009). If this is correct (more samples need to be run, hint, hint!!) I will like this outcrop even more (sorry, can't hide my love for the Oligocene)!!

Here's the one of my favorite outcrops, where the Lares and Montebello limestones are exposed. The arrow points to a sirenian fossil that is yet to be collected.

Of course, what I’ve been mostly searching in these localities are sirenian remains, but like I mentioned on that previous post, other vertebrates have also been collected. Interestingly, the best sirenian remains have been collected from the upper Lares Limestone, with a total (so far) of two skulls, and a set of nine articulated vertebrae (see picture below). There are more fossils but those will be collected in due time. As for the sirenian skulls, well, they are an important part of my thesis work and I will discuss them at some point in the future.

Some articulated sirenian vertebrae, these have already been collected. This is an earlier picture, there were three more vertebrae behind the one labeled Ca1, the ones anterior to L3 were collected earlier.

References

Johnson, C. C., W. R. Ramírez, L. R. Mark, S. Y. Hernandez, E. A. Barrow, M. Hegewald & J. Velez. 2006. Oligocene reef deposits linked to OPD site 999 with strontium isotope stratigraphy. Geological Society of America Abstracts with Program 38:557.

Ortega Ariza, D. L. 2009. Establishing a high resolution sequence stratigraphy and sea-level curve for Tertiary limestones, Puerto Rico. M.S. thesis, University of Puerto Rico, Mayagüez, Puerto Rico, 132 pp.

Ramírez, W. R., C. C. Johnson, M. Martínez, M. C. Torres & V. Ortiz. 2006. Strontium isotope stratigraphy from Kuphus incrassatus, Cenozoic limestones, Puerto Rico. Geological Society of America Abstracts with Program 38:90.

Seiglie, G. A. & M. T. Moussa. 1984. Late Oligocene-Pliocene trangressive-regressive cycles of sedimentation in northwestern Puerto Rico. American Association of Petroleum Geologist Memoir 36:89-95.