Beautiful new baleen whale skull

Hey Folks,

Thursday evening I received an email from by buddy Karl Heiman, who co-discovered a mysticete skeleton at a seawall construction project last April; the skeleton was headless, but nonetheless is a beautiful find (the excavation was conducted by PaleoResource Consultants and covered here and here). Anyway, on Thursday, as part of the same project, Karl was watching as a backhoe dug a trench, and the bucket chewed right through a rather large bone.

After some careful digging, it turned out to be a nearly complete baleen whale skull - photos he sent me yesterday show what it looked like after it had been entirely excavated in the field: about 5 feet long, and only missing part of the right hand side - the left side of the skull is largely intact. I'll email Karl and ask for permission to use his photos, but otherwise - trust me, it's damn pretty; I almost shed a tear.

Prep update: Purisima Formation mysticete skull 3

Here are some pictures of the balaenopterid skull after preparation was completed. I finished preparation the tuesday before spring break. On wednesday and thursday I made the cradles, and friday loaded it into my car to drive back to California (on saturday).

Oblique posterolateral view of the Purisima balaenopterid skull.
Ventral view of the Purisima balaenopterid skull.Lateral view of the Purisima balaenopterid skull.The skull with the completed ventral cradle.The skull with both ventral and dorsal cradles.

On Friday of Spring Break, I met UCMP Curator Mark Goodwin at the oversize storage facility to drop the specimen off. UCMP is getting a new storage facility which will be a vast improvement over the current warehouse at the Clark Kerr campus (conveniently located right on the Hayward Fault).

Prep update: Purisima Formation mysticete skull 2

Hey folks,

As I mentioned in a previous post, I've been preparing a fossil mysticete skull I collected from the Purisima Formation in 2005 for a long time (i.e. 4.5 years). This winter and spring I really stepped up preparation, and you can see in these photos what the specimen looked like in January. At this point, Tom Demere of the San Diego Natural History Museum, who specializes in fossil mysticetes, tentatively identified this specimen as belonging to "Balaenoptera" cortesii var. portisi, a medium sized balaenopterid from the Pliocene of Italy, Florida, and California (Demere et al. 2005). An undescribed cranium (UCMP) from the San Diego Formation and several crania I've seen in the Purisima Formation have this same morphology, but I did not realize this taxon was B. cortesii var. portisi, or that this specimen belonged in that taxon. "Balaenoptera" cortesii var. portisi is characterized by elongate, widely diverging zygomatic processes, which these other fossils have; it appears that the zygomatics of this specimen are damaged. It is also a taxon that needs a new genus, as it definitely has features that place it outside of Balaenoptera. Tom Demere and Michelangelo Bisconti are currently revising this taxon (Demere et al., 2005).

The new Purisima mysticete skull in posterolateral view.

The new Purisima mysticete skull in anterolateral view.

The new Purisima mysticete skull in dorsal view. note the wide, triangular supraoccipital shield, a typical feature of balaenopterids.

The new Purisima mysticete skull in anterodorsal view.

Anyway, quite a bit of matrix was left at this point. Soon, I'll post pictures of the specimen after preparation is completed.

Deméré, T.A., A. Berta, and M.R. McGowen. 2005.
The taxonomic and evolutionary history of fossil and modern balaenopteroid mysticetes. Journal of Mammalian Evolution 12:99-143.

Pinniped ancestry: the "Oligocene Seal" from South Carolina

One of the most fascinating aspects of the study of marine mammals are the origins of the land to sea transition in various groups. Often marine mammals are so adapted for marine existence, that it is difficult to identify what group (fossil or modern) they descended from. Such has been the case with the origin of whales, for example. While I'm certainly interested in cetaceans, there has been a ton written about them, and I'm currently more intrigued by pinnipeds.

While modern cetaceans don't necessarily look like their artiodactyl relatives, pinnipeds generally retain enough features that allows them to be readily identified as carnivoran mammals, straight down to the dog-like bark of California sea lions. Certainly, this should make identifying the terrestrial progenitors of pinnipeds an easier task. Or does it?

The prevailing opinion throughout much of the 20th century was that the Pinnipedia are diphyletic; the sea lions and walruses formed the "Otarioidea", who descended from the Ursidae, and the true seals (the Phocidae) descended from mustelid (or musteloid) ancestors. In 1973, Ed Mitchell and Richard Tedford described Enaliarctos mealsi from the Early Miocene Pyramid Hill member of the Jewett Sand in Kern County, California. Enaliarctos still bore an ursid-like shearing dentition, which is absent in all modern pinnipeds (which have generally homodont postcanine teeth). Enaliarctos was purported to be the common ancestor of the Otarioidea.

Later work (which at some point will be detailed on here) by Andre Wyss (UC Santa Barbara) and Annalisa Berta (San Diego State University), proposed a drastically different phylogeny of the pinnipeds, which suggested that pinnipeds were instead monophyletic, and that walruses (Odobenidae) were more closely related to the true seals (Phocidae), forming a new group, the Phocomorpha. Dozens of molecular phlyogenetic analyses have unequivocally supported pinniped monophyly, chucking the old diphyletic view out the window. The major tenets of the new studies are the following: 1) all pinnipeds descended from a common ancestor; 2) Enaliarctos is basal to the Otariidae, Odobenidae, and Phocoidea; 3) the Otarioidea is paraphyletic, as odobenids and desmatophocids are more closely related to the phocids; and 4) pinnipeds were derived from an ursid (bear) like ancestor sometime during the Late Oligocene, probably in the Northeast Pacific, where the oldest pinniped fossils are known.

Putative seal femora from the Late Oligocene of South Carolina, from
Koretsky and Sanders (2002).

In 2002, Irina Koretsky and Al Sanders reported on some partial femora from the Late Oligocene of South Carolina. According to Koretsky and Sanders, these femora are most similar to those of extant phocids, and list several features they share in common. However, they argued that the Late Oligocene age of these, as well as the occurrence of these in deposits of the Atlantic Coastal Plain, indicate that true seals were already present in the Atlantic Ocean when the very primitive Enaliarctos was just appearing in the Pacific Ocean. Thus, the monophyletic origin of pinnipeds was not supported by this fossil, and it appeared that true seals evolved in the Atlantic separately from the Otarioidea, which are (during the Oligocene and the Miocene) restricted to the North Pacific.

There are, of course, some issues with this study and its inherent implications, irrespective of the incomplete nature of the fossils. For starters, the fossil record is notoriously crappy; in fact, the Early Oligocene marine record is the poorest of all with regards to marine mammal fossils. Very few cetaceans are known from the Early Oligocene worldwide, for example, primarily due to the scarcity of marine rocks for this time, due to low sea levels caused by the Eocene-Oligocene climate crash. Pinniped fossils just "show up" after sea levels rise and deposit more marine sediments during the late Oligocene, in both the Pacific (Enaliarctos) and Atlantic (Phocid femora). So - it is entirely possible for even more primitive pinnipeds to be found in earlier sediments (or, as "lazarus taxa" in Late Oligocene rocks).

The completeness of these fossils requires additional scrutiny. Some of Koretsky's other work focuses on the major elements of the fore- and hind-limb of true seals (and lower jaws) but generally placing low importance on cranial material (Koretsky and Ray, 2008). Koretsky and Sanders (2002), however, did not compare these specimens with femora of Enaliarctos, or basal odobenids such as Proneotherium and Neotherium (or an unnamed basal odobenid described by Naoki Kohno early on, ~1990). Additionally, now that the putative stem-pinniped Puijila darwini has been described, it's femora should be compared with these specimens as well. These could very well turn out to belong to something more like Enaliarctos or Puijila that we don't yet have a record of in the Atlantic. However these fossils are interpreted, their Late Oligocene occurrence (if the provenance is accurate) is intriguing, and further field investigation of Late Oligocene sedimentary rocks of the Atlantic Coastal Plain (and elsewhere!) should be considered.

References:

Koretsky, I.A. and A.E. Sanders, 2002. Paleontology of the Late Oligocene Ashley and Chandler Bridge Formations of South Carolina, 1: Paleogene pinniped remains; the oldest known Seal. Smithsonian Contributions to Paleobiology 93: 179-183.

Koretsky, I.A., and Ray, C.E. 2008. Phocidae of the Pliocene of Eastern USA. In: C.E. Ray, D. 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: 81-140.

Mystery Pleistocene bones

Hey folks, I've been rather busy preparing for spring break (which I leave for in about 30ish hours), and I've actually gotten quite a bit accomplished - I finished preparing the whale cranium from the aforementioned post (there will be more follow up posts to that soon), and as of this afternoon, finished the second plaster/fiberglass cradle for the skull, which I will eventually be able to sink bolts through to keep the two halves together. Tommorrow I'll be attaching foam to the inside of the cradles, and then lugging the whole monstrosity to my (rather small) car. However, as this thing now weighs around 100 lbs or so, it is still only 1/3 of its original weight, so my car can do it.

Other than that, I submitted a manuscript this week (late monday night), about bite marks on some bones from the Purisima Formation; you'll hear more about it later on down the line.

Mystery marine fossils from the Pleistocene.

Anyway, as part of my mental preparation for spring break and looking at marine Pleistocene "rocks", here are some Middle Pleistocene fossils from a marine unit in California. I haven't been able to ID them, but they were originally ID'd by the collector as sea turtle claws. I'm naturally skeptical of that, but I'd like to see what you folks think, or if anyone can come up with something better (or, validate that ID).

Prep update: Purisima Formation mysticete skull 1

In 2005 I received a permit to collect vertebrate fossils from a locality in the Purisima Formation. This project lasted two summers, and resulted in the collection of dozens of shark teeth and vertebrae, calcified cartilage skate jaws, pinniped bones and teeth, several bird bones, odontocete and mysticete bones, including a handful of tympanics, a complete lower jaw of Herpetocetus, a porpoise cranium, and the big kahuna: a 300+ lb plaster jacket with some sort of mysticete skull inside. I wasn't really sure what it was in the field, although I suspected it was a balaenopterid (i.e. rorqual whale, like a Minke, Humpback, Fin, or Blue whale) on gut feeling alone.

The cranium prior to excavation, June 2005.

I first spotted the skull over thanksgiving break in November, 2004, with a flashlight just after sunset. I thought it was a skull at the time, but hadn't seriously thought about getting a permit yet. After I started the permit application process, I actually forgot entirely about the skull, and hadn't thought seriously about excavating it. When I finally stumbled across it again, I thought "why the hell not?" and up until the last few weeks, I've regretted the decision. Bottom line - I spent five months preparing the soft matrix from the ventral side, and in Spring 2006 I moved it to Museum of the Rockies, where I've been (intermittently, given my school schedule) preparing it with pneumatic airchisels since.

Day 1 of the excavation - we started at 5 in the afternoon, and stopped at about 10pm, digging by lantern, headlamp, and heavy metal.

Four years of preparing it with pneumatic tools - this skull was encased in a ridiculously hard concretion which only gets harder toward the center; concretions from elsewhere in the Purisima Formation are "nice" in that they 1) are of constant hardness throughout, and 2) the rock splits off the bone in these other cases. For this specimen, rock never splits off the bone, and in most cases I've had to prep all but 1-2mm of rock away and then grind it down with the airchisel, so some surfaces have definitely gotten a little scored. No matter, because all the sutures are visible, and it looks pretty nice anyway (unless you look at it with a hand lens). So shoot me; if I'd done it 'better', I'd have another year or two of prepwork to do. As it is, I'm leaving some matrix in the left temporal fossa, and elsewhere.

Vicki Jacklich and Liz Johnson (North Carolina State University) assist with the excavation, on Day 2.

A closeup of the skull, which is upside down. The rostrum is missing, and the vomer is the elongate bone pointing to the left. The frontal is the roughly triangular bone in the middle, the arcuate bone is the lateral crest of the supraoccipital shield, which slightly overhangs the temporal fossae (filled with matrix); the base of the squamosal is preserved at left.

I love surprises; this is a broken, partial basking shark (Cetorhinus maximus) gill raker found associated with the skull. I've found two more during preparation.

Here Vicki and I are putting the finishing touches on a preliminary jacket to protect some exposed bone.

Liz Johnson (NCSU) assisting with plaster jacketing.

The end of day 3: the skull is now trenched and tunneled under (see rock hammer) and ready for the rest of the plaster jacket to be applied.

Another view of the skull bearing pedestal after trenching and tunneling.

The completed top jacket prior to flipping on Day 4; I didn't have much time to take photos after this.

After the top jacket dried (which took over a day, due to the extremely humid air and my lack of jacketing experience), my temporary field assistant (and friend since 1st grade) Matt Berrini and I used what resources we had, and played 'egyptian' for a while: the ancient egyptians used earth for monument construction. For building pyramids, they built an earthen ramp; for raising obelisks, they had a chamber filled with sand; after the obelisk was raised by ropes, the obelisk was propped up by the sand in the chamber, which was slowly removed, allowing the obelisk to become upright with comparatively little further struggle. So - we built a fairly large 'ramp' of beach sand up to the jacket (as the skull was about 1 meter above the beach) so that the jacket did not break apart and collapse during flipping. In retrospect, the incredible density of the concretion probably indicated we could have probably let it fall anyway (although parts of the bones protruded from the concretion's boundaries, and may have broken).

Anyway, that's all for now, but soon I'll have another post about the prep process, and let you in on the last 5 years of my life.

Benthic feeding in basal mysticetes, part 2: Mammalodon, the freak

Sorry about the "short" delay; the last week or so has been pretty rough, between my Paleobiology course, getting sick, and administering/grading my first exam. But, all of that's over now, so I've been able to allot some time to this again.

My last post concerned paleopathology and histology of the "cetothere" Diorocetus hiatus, published by Brian Beatty and Alton Dooley last summer in Jeffersoniana. In it they posited that Diorocetus may have been a benthic feeder based on peculiar pathologies as well as an interesting pattern of rib osteosclerosis.

Comparison of the size of Mammalodon and a blue whale. From http://museumvictoria.com.au

There's been some buzz in the science blogosphere recently about the truly bizarre Australian toothed mysticete Mammalodon, the subject of a new monograph by colleague Erich Fitzgerald. I'll admit I've been anticipating this paper since Erich's talk at SVP in 2008 (the same session as my first ever SVP talk, you know, the one where no one could see any of my text). Some other blogs have covered Mammalodon already, but mostly just some of the stuff you already hear in the news; ya, it was a mysticete with teeth (all toothed mysticetes look pretty weird), and it likely a benthic suction feeder, so what? There's far more interesting 'meat' in the paper, if you will, that someone who wasn't a mysticete worker and therefore didn't have time or interest to read 110 pages might not pick up on. Okay, I didn't read the description, but I've read the in depth discussion.

The skull and dentary of Mammalodon. From http://museumvictoria.com.au

Mammalodon colliveri was originally described in 1939 from the Oligocene Jan Juc Formation of Australia, although it was not identified as a toothed mysticete until the 1980's when Ewan Fordyce (U. Otago, New Zealand) undertook additional preparation of the fossil. In 1966, Doug Emlong (an extremely prolific and gifted amateur collector) described a peculiar toothed cetacean he discovered in the Oligocene of Oregon: Aetiocetus cotylalveus. Emlong thought it was an archaeocete, but Leigh Van Valen soon after recognized several mysticete features. Toothed mysticetes may seem odd at first, but when you think about it - 1) teeth are primitive for cetaceans and indeed mammals, and 2) they had to eat with something before baleen evolved. Mammalodon shares many similarities with Janjucetus, including a short rostrum, short triangular supraoccipital, and large orbits; however, Mammalodon is distinct in having laterally oriented teeth, and a relatively flat rostrum.

Comparison of Mammalodon (left) and Janjucetus (right). From Fitzgerald (2010).

Mammalodon has some strange features - a short, flat snout, large, upward facing orbits, large foramina on the maxilla, upper teeth that project laterally, and peculiar wear facets on the lower dentition that look like they were filed down at the same time (so to speak) - i.e. they share wear facets oriented on one single plane. Some authors have interpreted the denticulate teeth of basal mysticetes like Llanocetus and Mammalodon to have had a role in filter feeding, much like the teeth of the extant crabeater seal (Lobodon carcinophagus). Fitzgerald (2010) rejected this interpretation, as he did earlier (2006) for the tooth morphology of Janjucetus. Based on the probable presence of hyaline cartilage in the jaw joint of Mammalodon (as opposed to fibrocartilage in lunge feeding balaenopterids), Fitzgerald also rules out lunge filter feeding. Bony correlates of baleen, nutrient foramina, are absent on the palate of Mammalodon, suggesting that it did not possess baleen (such as later diverging aetiocetids - I'll talk more about those next time). Taken in full, few features of Mammalodon suggest filter feeding, rather than raptorial/pierce feeding (aka, biting stuff). Aside from this, some of the features unique to Mammalodon such as the very short rostrum, large maxillary and mandibular foramina, and extreme tooth wear suggest an alternative behavior. Typically, large foramina indicate improved blood flow and innervation to a region; for example the tactile whiskers of pinnipeds are correlated with a greatly enlarged infraorbital foramen (a pinniped synapomorphy), relative to "fissipeds". In this case, the short rostrum, probable highly innervated oral region, and wear most likely due to substrate interaction, all point towards benthic suction feeding. Additionally, the up-and-forward facing orbits would have conferred some degree of binocular vision, similar to the walrus and the bizarrer walrus convergent odontocete, Odobenocetops.

Various archaeocetes (top row), mammalodontids (second row) and aetiocetids (bottom two rows). From Fitzgerald (2010).

Most interestingly are the implications of the phylogenetic hypothesis of this study on the evolution of feeding in the mysticetes, relative to other recent hypotheses. Raptorial feeding is primitive for cetacea as a whole, including basal mysticetes. Interestingly, Llanocetus, Janjucetus, and Mammalodon all form a southern toothed mysticete clade, and Fitzgerald (2010) lumped Janjucetus and Mammalodon into the family Mammalodontidae, scrapping the family Janjucetidae he proposed earlier (2006). Llanocetus exhibits no adaptations for suction feeding, although Janjucetus does, suggesting that suction feeding is derived for this clade, but not a typical feature of basal mysticetes in general. Thus, this suggests that whatever feeding mode the mammalodontids employed was likely not representative of early mysticetes, contra Fitzgerald (2006).

Feeding evolution in baleen whales. From Fitzgerald (2010).

What the hell is Llanocetus, anyway? Llanocetus is perhaps the most interesting and strange described/undescribed cetacean out there. Well, what does that mean? Llanocetus was collected from the late Eocene La Meseta Formation of Antarctica. Yes, the Eocene of Antarctica, my friends. Why is that particularly awesome? The Eocene is dominated by archaeocetes, and elsewhere on earth during the late Eocene fantastic critters like Basilosaurus and Dorudon were kicking ass and taking names. And Llanocetus is the earliest known mysticete, let alone record of the Neoceti. The original description of Llanocetus denticrenatus by Ed Mitchell (1989) includes a maxillary fragment, mandible fragment, and an endocast - overall, marginally crappy. Later on, Ewan Fordyce revisted the site and collected what he initially thought was an archaeocete, and it even included (apparently) vestigial hindlimb elements (plural), similar to the condition in basilosaurid archaeocetes (which are not too phylogenetically divorced from Llanocetus, after all). This turned out not only to be a toothed mysticete, but the remainder of the holotype skeleton. My guess is that whoever originally collected the holotype scraps was freezing their ass off and said "to hell with it" and left. However, even though a cast of the skull is now on display at the USNM, the rest of the holotype is not yet described, and the dotted outline provided by Fitzgerald (2010) is the most informative figure ever published of this rather interesting beast. Anyway, I'll be pretty excited whenever the description gets published (much of the above information was presented by Fitzgerald, 2010, in his discussion of taxa used for the cladistic analysis).

The next post will (hopefully) be less-rambling, and will detail the transition from teeth to baleen in archaic mysticetes.

References:

Fitzgerald, E.M.G. 2006. A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proceedings of the Royal Society B: Biological Sciences
273: 2955–2963.

Fitzgerald, E.M.G. 2010. The morphology and systematics of Mammalodon colliveri (Cetacea:Mysticeti), a toothed mysticete from the Oligocene of Australia. Zoological Journal of the Linnean Society. 110p.