New published article (Part 1): herpetocetine jaws, and an example of finding a "simple" research project

The new issue of PaleoBios, the paleontology journal published by UCMP at UC Berkeley, includes my new article on herpetocetine jaws from the Santa Margarita Sandstone in central California. During the fall of 2008, I was in my first semester of graduate school, and was taking a difficult, time-intensive course on advanced stratigraphy. At the time, I already had two articles I had been working on: one on my undergraduate research concerning a new fossil vertebrate assemblage from the Purisima Formation, and another on Plio-Pleistocene fur seals from the Wildcat Group in northern California (both are currently in press). However, neither was in any shape to be published anytime soon - one was only half written, and the one that was nearly finished needed a lot of work (i.e. quality control). I needed a new manuscript to work on, to give me something to do that semester aside from stratigraphy, which had started to eat away at my brain. In other words, I needed to start something fresh from scratch, with a clear beginning, a clear end, and a clear message.

The right dentary of UCMP 85431. Scale bar =10cm. From Boessenecker (2011).

A month earlier, I had given a presentation (coauthored with Jonathan Geisler) on a new skull of Herpetocetus bramblei I had collected from the Purisima Formation in 2007. While ruminating on possible projects, I suddenly remembered a partial lower jaw from the Santa Margarita Sandstone that looks a lot like the lower jaw of Herpetocetus*. The problem is, the Santa Margarita Sandstone is early Late Miocene in age (10-12 Ma), while the oldest known bona fide specimens of Herpetocetus are latest Miocene to earliest Pliocene in age (~5 Ma). In fact, the oldest known described specimen is the fragmentary type specimen of H. bramblei, which is right about 5.33 Ma. So, this specimen (UCMP 85429) is MUCH older than any known specimen of a "true" Herpetocetus.

*All species of Herpetocetus have relatively similar lower jaws, and currently the lower jaw has only been described for the type species, Herpetocetus scaldiensis (the type specimen of which is a lower jaw - more on this later).

The left dentary of UCMP 85429; scale bar = 10cm. From Boessenecker (2011).

The lower jaw of baleen whales has long been assumed to be a fairly diagnostic element, at least in certain groups. Herpetocetus scaldiensis certainly has a very distinctive mandible. Other fossil mysticetes certainly have distinctive mandibles as well. Many fossil mysticetes (H. scaldiensis, Balaenoptera davidsonii, Archaeschrictius ruggieroi, etc.) have been described just off of their lower jaws. Are dentaries really that diagnostic? Perhaps. Demere (1986) used mandibular features to reevaluate "Eschrichtius davidsonii" from the San Diego Formation, which was a chunk of a 30% complete mandible, missing the anterior and posterior ends. Being able to refer a new dentary to this taxon, he demonstrated that the "davidsonii" morphotype was actually a rorqual, and assignable to the genus Balaenoptera, which led to its recombination as Balaenoptera davidsonii. Clearly, mandibular morphology is important, and can be used to assess the taxonomy of certain groups, and 'fix' the taxonomy of certain problem taxa. Are these specimens the oldest known records of Herpetocetus?

Reconstructed lower jaw of Herpetocetinae genus and species indet., based on UCMP 85429 and 85431. From Boessenecker (2011).

Reflecting upon the known fossil record of "true cetotheres" - relatives of Cetotherium and Herpetocetus (an entire other topic worthy of its own post) - I was able to formulate some interesting questions I could ask (and attempt to answer), which would make a nice core of an article. With these objectives in mind, I started taking copious notes on the anatomy of the fossil specimens, and eventually typed these notes up into an anatomical description for the article. By the end of the semester, I had a manuscript that was about three-quarters finished. During spring 2009, I wrapped up the discussion, and constructed some figures. I had a few people look at it and make some comments. Morgan Churchill looked at it late in spring, and had some of the most constructive and useful edits. That summer, I TA'd the Geology Field Course for MSU, and during some of the weeks, I took my manuscript out into the field with me, along with a red pen. In between helping students, I sat out in the hot sun, and critically examined every sentence in the manuscript. I even drafted one of the figures (on vellum, with nice pens) around the campfire one night after a few beers. By the end of the second to last project at field camp, I had all my edits finished, and I sent it off to PaleoBios for review.



To be continued...

Boessenecker, R.W. 2011. Herpetocetine (Cetacea:Mysticeti) dentaries from the Upper Miocene Santa Margarita Sandstone of Central California. PaleoBios 30:1:1-12.

Deméré, T.A. 1986. The fossil whale, Balaenoptera davidsonii (Cope 1872), with a review of other Neogene species of Balaenoptera (Cetacea: Mysticeti). Marine Mammal Science 2:277–298.

Broken tailbone

I failed to mention this a year ago when it happened, but during spring break last march (2010) I broke my tailbone way up in a quarry in the Santa Cruz mountains. I was sliding down a steep gulley carved in the Santa Margarita Sandstone, attempting to access a bonebed. I can't even remember if I got anything or not, but at one point, I realized I could not go back up as I had done before.

The dreaded gulley I dropped out of, right onto my #@!.

I looked below me - I had another ten feet of gulley or so before it dropped off. It looked like a large talus cone of sand about fifteen feet below me, which is also exactly what you'd expect, you know, at the bottom of a gulley like that. It looked like a six foot drop or so, nothing bad - I've jumped off cliffs down to the beach from a little bit higher with no consequence, so I thought I might as well. So I slid down to the end, and dropped down, with both toes pointed downhill. Only, the drop ended up feeling a little longer than 6 feet. When I landed, my feet bounced off the "talus cone", which was in fact a thin (1 inch?) veneer of sand over a smooth sandstone surface, my legs flew up in the air, and I fell back onto my tailbone. Now, this wasn't like my feet slowed me at all - all this took place within a second, and I effectively fell the entire distance with my tailbone intercepting 90% of the impact.

The red line shows the distance I fell onto my tailbone.

Naturally, I sat there writhing in pain for a good fifteen minutes, after I crawled out of the hot sun. Luckily no one was in the vicinity (it was pretty embarrassing), or perhaps if they were, they were driven away by a ten minute string of expletives. I've never broken a bone before (except a possibly less serious tailbone break during a snowmobile mishap in 2006), and I gotta admit, the pain was pretty intense. It's strange, it was really dull, but so intense it made me nautious for the better part of two hours. It took a while before I felt like I wouldn't puke from it. And damnit, I had just eaten a nice homemade lunch - I didn't want it to go to waste! Fortunately, after a while I kept on prospecting, and found a beautiful partial Imagotaria downsi (early walrus) dentary.

Chris Pirrone surveys the dreaded quarry.

In December I returned to the locality with my buddy Chris Pirrone, and we found a LOT of bone. It appeared as though an entire mysticete dentary (the single largest bone to ever evolve) that had formerly been about 5 or 6 feet long had eroded out of the cliff into about thirty pieces and was beyond salvage. However, we did find what appears to be an Imagotaria metapodial, which will be nice when I get it prepared. Anyway, I took these photos of the gulley, and when we returned to the site, it looks like I fell 8-10 feet instead of 6. Fun!

Anyway, the day I broke my tailbone, I continued my day and hit up about four more localities - sure, driving was awkward as hell, but standing didn't hurt one bit. In fact, it seemed to help. I actually ended up finding some great stuff that day. I thought about returning home, but I realized all I'd be doing there would be sitting around, which would hurt more than a day of fieldwork along the pretty coastline. What really sucked was the drive back to Montana - I had to pull over every hour and a half or so to get up and walk around.

The moral of the story is: be careful, and don't get cocky (or, overexcited and lose track of your surroundings). And if you must do what I did, land sideways with one foot downhill, like you're surfing. Never go face down, or facing the cliff (I can imagine a faceplant into the rock wouldn't be too nice). Or tuck and roll.

It's now 11 months later, and my tailbone still hurts if I sit in a bad chair for a couple hours.

Scotts Valley whale excavation, part 2

Before I continue, I need to give a shout out to Nick Pyenson - Nick initially forwarded Dr. Smith's emails to me, and this project has wasted a third of my summer. No, but seriously, thanks.

After putting the top jacket on, then came the problem of how exactly I was going to A) undercut it and B) actually flip it over. Normally, a trench is cut and then the pedestal is undercut from all sides leaving a pillar of rock underneath, which you can subsequently eliminate and then flip the jacket over. However, this jacket was far too large to do conventionally. And I couldn't really fit tools in all the way around the jacket to really undercut it from all sides.

So, in cases like this, go tunneling! I started two holes and dug and dug until they connected, and then widened them into a larve cavern underneath, and then added a hole on the other side. Problem was, this jacket was so large, I eventually couldn't reach the back wall with my rock hammer, and had to use my large estwing pick to scrape away underneath. Tunneling, by the way, is a good recipe for bloody knuckles.

Here you can see more of the tunnel. Aside from these two small columns, the back part remained as a large pedestal in back; the jacket stuck out from this like a surfboard with two pillars. Once I cut the pillars, I figured it would break the pedestal, and tilt forward.
The moment of truth! This was on the heavy side. Well, nothing happened - the left pillar remained still, but I figured it would fail if given this much weight. Apparently not, however - it just hung like this for several minutes.

When I cut through the other pillar, it shifted almost imperceptibly forward, but I knew at that instant that I had been successful. Then, I found one of the construction workers to help me flip it over and complete the jacket.Here's what it looked like - you can see the overhanging plaster; that's where the crack formed, leaving a little bit of the pedestal back in the hole, which I'll excavate in a separate jacket.

Voila! Here's the completed plaster jacket. It's pretty heavy.

The Coastal Paleontologist returns: Scotts Valley whale excavation, part 1

Hey folks, a lot has been going on recently. First and foremost, I've been busy dividing my time between collecting the last remaining data for my master's thesis, vacationing up at lake Tahoe (very difficult), and editing manuscripts. I hit a milestone yesterday - I submitted two manuscripts in the same day. I've been working like a hound the last few days to wrap up the first manuscript I ever started: a paper on the sharks, rays, fish, and birds from a new vertebrate assemblage in the Purisima Formation, titled: "Non-mammalian vertebrate remains from a new marine assemblage near Halfmoon Bay, California: Implications for the age of the Neogene Purisima Formation west of the San Gregorio fault", which I submitted to the PalArch Journal of Vertebrate Paleontology, an open access journal based in the Netherlands. I've heard they could use some more submissions, so be sure to read Andy Farke's interview with the PAJVP editor Brian Beatty, linked above. If you've got an article ~75% finished, put in a long weekend and submit that beast! The other article, "Mammalian bite marks on juvenile fur seal bones from the late Neogene Purisima Formation of Central California", was originally submitted to Palaios in march, and returned for major revisions, and apparently all I needed were three hours of work to finish it and resubmit it.
One of the first projects I started this summer was to excavate some sort of a whale fossil at a construction site in Scotts Valley. I was contacted early on in the spring by Dr. Roberta Smith, the project's consultant geologist. Oddly enough, Roberta had been in grad school at UC Berkeley in the mid 1960's when folks like Malcom McKenna and Ed Mitchell were there. To make matters stranger, she had also taught at Howard University and worked at the USNM in Washington D.C., where she knew other well known fossil marine mammal workers Clayton Ray and Frank Whitmore (but stopped teaching there long before Daryl Domning started). Anyway, I'm getting off track. The photo above shows the fossil after a day or so of digging. The exposed bones were not ribs or vertebrae, and I didn't care to expose enough of them for a proper ID due to their relative 'softness'. "What are those cinderblocks doing there?", you ask? Read on...

After about a week of day trips and short visits, the trench is nearly completed around the fossil. Bones continue into the back wall, but were too difficult to continue to excavate; I decided that during jacketing, I would try to form a crack across, collect most of it in one jacket, and return to make a second jacket for the rest.

Here you can see why there were cinderblocks in the first couple pictures. They had already put up a retaining wall, and when they found bones, they marked it off and left the retaining wall unfinished. I was able to park only about 8 feet away. This was the weirdest excavation I've ever done.

And here is the top jacket finished! Note that the hammer is way in the foreground; the jacket is much larger than it appears, and is nearly 4' by 4', and weighs between 300 and 400 lbs.

Summer Adventures Part 2: Clastic Dike

Late during the summer I revisited a classic and bizarre geologic site - the Santa Cruz Mudstone west of Santa Cruz, California. This spot in particular is called Shark's Cove, and is near Bonny Doon State Beach. This place looks like it is right out of a pirate story. Robert Louis Stevenson could have based a whole pirate story after this place.

Yar, here there be clastic dikes.

The Late Miocene (7-9 Ma) Santa Cruz Mudstone overlies the early Late Miocene Santa Margarita Sandstone. The Santa Margarita Sandstone is famous for large scale cross-strata formed by huge mega-bedforms (i.e. eolian dune size), as well as one of the most well preserved (and still under-studied, aside from sea cows and walruses) Tortonian/Serravalian marine vertebrate assemblages on the planet. The Santa Cruz Mudstone is known for a few marine verts (Parabalaenoptera baulinensis, from further north) but most famously for two things: methane cold seep-related carbonate pipes (a later post) and (arguably more famous) for its extensive clastic injections, dikes, and sills.A neat sea cave! But what else is it?

Fluidized sand (the Santa Margarita Sandstone is barely cemented; it looks like a holocene beach deposit, and is very easily sifted through for finding shark teeth) was injected into the overlying siliceous mud of the future Santa Cruz Mudstone (after a huge local transgression), typically as sills (parallel with bedding) and vertical dikes, as well as blobs. Above is a photo of me in a natural arch, with the dike above. The below photo shows the Santa Margarita Ss. derived dike (Tsm) and the Santa Cruz Mudstone (Tsc).

More of the dike, and idiots in the background who almost got stranded here at high tide.

EDIT: I failed to mention that this is the largest clastic dike system on the planet. For more pictures of weird fluidized clastic injections, visit the Injected Sands Group (University of Aberdeen), and read:

Scott et al, 2009. The Process of Sand Injection: Internal Structures and Relationships with Host Strata (Yellowbank Creek Injectite Complex, California, U.S.A.). Journal of Sedimentary Research 79:568-583

Boehm and Moore, 2002. Fluidized sandstone intrusions as an indicator of Paleostress orientation, Santa Cruz, California. Geofluids 2:147-161