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.