Friday, March 23, 2012

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. 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.

Thursday, March 22, 2012

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. 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.

Wednesday, March 21, 2012

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. 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.

Tuesday, March 20, 2012

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. 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.

Monday, March 19, 2012

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.

Sunday, March 18, 2012

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.

Saturday, March 17, 2012

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.

Friday, March 16, 2012

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:

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.

Thursday, March 15, 2012

Dispatches from the field: Baja California, Pt. 1

Ove the last several days I've been traveling through the Baja California Peninsula with Daryl Domning of Howard University (and my advisor) and Larry Barnes, emeritus curator of fossil marine mammals at the Natural History Museum of Los Angeles. The reason for this trip is to re-visit some sirenian localities, including the type localities of Dusisiren reinharti and Dioplotherium allisoni, both in Baja California Sur.
The Pacific coast, somewhere along the road from Tijuana to Ensenada.

However, we first made a stop in Ensenada, to look at some specimen of Metaxytherium arctodites (including the holotype) under the care of our colleague Francisco Aranda-Manteca of the Universidad Autónoma de Baja California (UABC). After a couple of days in Ensenada we headed out to our destination near San Juanico in Baja California Sur. We wouldn't get there until two days later, the route to our final destination is long and takes us zigzag-like through a great deal of length of the peninsula, but the long drive was worth it. The scenery is just stunning!
The sun sets over the cacti somewhere along the road from Ensenada to Guerrero Negro.

Outcrops and long winding roads, near Santa Rosalia, this was on the leg of the trip between Guerrero Negro and San Juanico. You can see the Sea of Cortez in the distance.

More tomorrow, including our first day in the field, stay tune!!

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.

Belugas tropicales... mi incursión en la paleocetología

Los monodóntidos, el grupo de ballenas que incluye las belugas y narvales, son símbolos emblemáticos del Ártico. Sin embargo, su registro fósil, aunque escaso, nos dice una historia distinta. Fósiles de monodóntidos han side encontrado previamente en depósitos del Mioceno temprano en Baja California, México, y el Plioceno temprano de Bélgica y la costa este de Norteamérica. En la edición de este mes del Journal of Vertebrate Paleontology, Nick Pyenson y yo describimos una nueva especie de monodóntido fósil de depósitos del Plioceno temprano (entre 3-4 millones de años atrás) en Virginia y Carolina del Norte. El fósil, denominado como Bohaskaia monodontoides, le rinde honor a David J. Bohaska del Museo Nacional de Historia Natural (NMNH por sus siglas en inglés) en Washington, DC, y miembro del Pyenson Lab, por su conocimiento y dedicación a la herencia paleontológica del litoral este de Estados Unidos.
Arriba en primer plano, Bohaskaia monodontoides; atrás, una beluga y un narval, la reconstrucción de Bohaskaia fue basada en su parecido a las dos especies actuales del grupo. Arte por Carl Buell.

Bohaskaia, al igual que otros fósiles de monodóntidos, ocurren en latitudes más templadas que sus parientes existentes. Nosotros proponemos que estas ocurrencias implican que el grupo, hoy día restringido a aguas Árticas y sub-Árticas, era tropical a sub-tropical en el pasado. El especimen que sirve de base para la descripción de Bohaskaia tiene una larga historia en el NMNH. Originalmente fue encontrado en 1969 en una localidad conocida como 'Rice's Pit' en Hampton, Virginia. Frank C. Withmore, Jr., uno de los miembros fundadores de la Sociedad de Paleontología de Vertebrados y desde hace mucho tiempo miembro de la comunidad científica del Smithsonian , a través de su vínculo con el Servicio Geológico, reconoció el parecido a los monodóntidos del especimen, en especial su similitud con las belugas, lo cual mencionó en varias publicaciones. Frank lo describe como una especie de Delphinapterus (el mismo género de las belugas modernas), y así quedó por mucho tiempo, sin estudiar. Cuando Nick llegó al museo en el 2009, el y yo estábamos buscando en la colección algo para hacer un trabajo colaborativo sobre anatomía de cetáceos. Nick sugirió que estudiáramos el espécimen de Rice Pit, ya que el había visto una réplica mientras era estudiante graduado en el Museo de Paleontología de la Universidad de California en Berkeley. con el fósil en mano, hicimos un viaje a las facilidades externas del NMNH en Suitland, Maryland, para comparar el fósil con restos óseos de belugas y narvales en la colección de mamíferos marinos de la División de Mastozoología, la cual es supervisada por Charley Potter y Jim Mead. Nuestro estudio, además de confirmar que Bohaskaia monodontoides es un monodóntido (por ende su nombre específico), reveló que es una especie más primitiva, y por ende única del grupo. Otro aspecto interesante de Bohaskaia, es que, al igual que otro monodóntido fósil conocido como Denebola brachycephala, han sido encontrado en latitudes menores de las que habitan su relativos actuales.
Los autores con el homenajeado. De izquierda a derecha: este servidor con un cráneo de beluga, Dave Bohaska con el cráneo de Bohaskaia, y Nick Pyenson con un cráneo de narval. (El colmillo que aguanta Nick es distintivo de los narvales machos, este es una réplica de uno existente en la colección).

Velez-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(2):476–484.


Eventualmente, el PDF de la publicación se podrá descargar gratis a través del Smithsonian’s Digital Repository.

Entradas previas sobre monodóntidos:

Convergencia: el caso de Odobenocetops ó el delfín que parecía morsa

Answer to the last post: it was a unicorn...

Upcoming: new publication in JVP

Other media:
[Ocean Portal], [Around the Mall blog], [SmithsonianScience], [Pyenson Lab], [MSNBC], [LiveScience], [UPI], [EarthTimes], [Science Codex], [RedOrbit], [Montreal Gazzette], [Calgary Herald], [Times Colonist], [Discovery News]