New artwork: reconstruction of a remingtonocetid whale

Some time last fall I sat down and sketched out a drawing of Remingtonocetus, after Bajpai et al. (2011) was published. This new study described a new, nearly complete (and beautifully preserved) skull of Remingtonocetus harudiensis from India. The remingtonocetids are possible one of the only monophyletic groups of archaeocetes, and all appear to be relatively small-bodied, with ridiculously big heads and long rostra, very tiny and dorsally placed orbits, heterodont dentitions, and long tails. Perhaps the best way to imagine a remingtonocetid is to picture an otter with the (furry) head of a gharial.

The skull of Remingtonocetus harudiensis, from Bajpai et al. 2011.

The holotype skeleton of Kutchicetus minimus, from Bajpai and Thewissen (2000).

I had inadvertently sketched the head too small on the body, so when I completed the drawing over Christmas break with my wife's family in Montana, I ended up with a critter with a head that is way too small (although it looks like a less absurd beast, to be quite honest).

The original, unaltered drawing.

To fix this, I did some editing in photoshop after I had scanned the image - mostly by enlarging it's head about 20% or so. I also decided to experiment with texturing, and ended up with something that fairly convincingly looks like fur; I'm still experimenting with drawing fur in pencil, and as you can see between these two - the photoshopped version looks quite a bit better. Texturing can be pretty difficult on a small drawing - the original is only about 6" long from nose to tail. I was also able to make the wet fur on 'his' nose a little 'spikier'.

The modified version of the artwork. Overall, I'm quite satisfied with this piece, and am rather surprised that I was able to portray an archaeocete cetacean as "cute" - archaeocetes in general are pretty nasty, scary looking beasts, like Ambulocetus, Basilosaurus, Georgiacetus, and Dorudon.

The skull of Andrewsiphius, from Thewissen and Bajpai (2009).

There are a number of different remingtonocetids, including Remingtonocetus, Andrewsiphius, Kutchicetus, Attockicetus, and Dalanistes. Only Andrewsiphius and Remingtonocetus are known from good, well preserved crania. Bajpai et al. (2011) suggested that, based on the strange skull anatomy of Remingtonocetus, that remingtonocetids were ambush predators that were heavily reliant upon hearing rather than sight. The muscle attachment area is very large, and coupled with the very narrow jaws - suggests that remingtonocetids had a weak, but very fast bite, well suited for ambushing and catching small fish. Additionally, because Remingtonocetus was aquatic, the extremely long snout was probably not an adaptation for improved olfaction; Bajpai et al. (2011) hypothesize that as Remingtonocetus was one of the first marine cetaceans, this may have been an adaptation towards retention of freshwater during respiration.

Next up - continuation of the southern California research trip, Kolponomos, my Purisima vertebrate assemblage paper, desmatophocid taxonomy, etc.

Further reading:

A different kind of Whale, at Laelaps

Bajpai, S., and J.G.M. Thewissen. 2000. A new, dimunitive Eocene whale from Kachchh (Gujarat, India) and its implications for locomotor evolution of cetaceans. Current Science, 79(10):1478-1482.

Thewissen, J., & Bajpai, S. (2009). New Skeletal Material of Andrewsiphius and Kutchicetus, Two Eocene Cetaceans from India. Journal of Paleontology, 83 (5), 635-663.

Bajpai, S., Thewissen, J.G.M., and R.W. Conley. 2011. Cranial anatomy of Middle Eocene Remingtonocetus (Cetacea, Mammalia) from Kutch, India. Journal of Paleontology 85(4):703-718.

New artwork I: Cynthiacetus reconstruction

Hey folks,

Some of you cetophiles may have already seen photos of this specimen floating around on the internet. I thought the mount was pretty dynamic, and would work well as a skeletal reconstruction - so I did it. A photo of this specimen which has thus far only been identified as cf. Cynthiacetus is featured in a recent paper by Christian de Muizon.


Cynthiacetus is a dorudontine archaeocete that was originally described from the Eocene of Mississippi by Mark Uhen. He also referred a few vertebrae and a partial skeleton to this taxon from the Eocene of Egypt. This new skeleton (and I am not sure how complete it is) is from the Eocene of Peru, and is part of a large new collection of Peruvian archaeocete cetaceans we will be hearing about over the next few years.

Uranocetus and hearing in mysticetes

Hey Folks, Sorry about the delay; I realize its been over a month since I last posted anything. Winter break was not exactly relaxing, and the parts that neared relaxation were spent doing fieldwork (which definitely yielded some interesting material). In other news, my first technical paper has been tentatively accepted for publication by the UCMP-published journal PaleoBios; I'm approximately 99% done with revisions at this point, so you'll hear more about it after it's in press.

Recently two mysticete related papers have been published - Erich Fitzgerald's monograph on the truly bizarre Mammalodon colliveri, which I'll cover later, and M.E. Steeman's (2009) thought provoking paper naming the new "cetothere" Uranocetus from the Miocene of Denmark and its implications for mysticete hearing.

The cranium of Uranocetus, from Steeman (2009).

First off, "cetotheres" are a wastebasket group of generalized archaic baleen whales that don't fit nicely in modern families, although Bouetel and Muizon (2006) have redefined the Cetotheriidae sensu stricto as a small group with some very strange cranial features, including my personal favorite, Herpetocetus. Most other cetotheres (Cetotheriidae sensu lato) were placed into newly named families (Pelocetidae, Aglaocetidae, and Diorocetidae) which were sister taxa to the Balaenopteridae all included in her concept of the Balaenopteroidea (but not in the concept of the Balaenopteroidea advocated by Demere et al. 2005, which is Eschrictiidae + Balaenopteridae). Bottom line is Uranocetus is some kind of stem baleen-bearing mysticete, no matter whose phylogeny you use. The dentary of Uranocetus (from Steeman, 2009).

Interestingly, while it is placed rather close to Balaenopteridae, it still retains a large mandibular foramen, a plesiomorphic feature for mysticetes. The mandibular foramen is very small in extant mysticetes, but extremely large in odontocetes, so much that the posterior portion of the dentary is a thin bony shell (the "pan bone") that houses the mandibular fat pad. The lateral margin of the dentary is extremely thin, so that high frequency sounds can pass through without significant volume loss (Nummela et al. 2007, Steeman 2009). High and mid frequency sounds pass through this, and are then channeled up through the mandibular fat pad and up to the tympanic plate; in odontocetes, this is more or less a functional analog of the external ear pinna. And, by the way, all these strange auditory features are adaptations for allowing directional hearing underwater; otherwise terrestrial mammals hear via bone conduction hearing (sound travels faster in water, and the mammalian body is roughly as dense as the surrounding aqueous medium), and sounds more or less arrive at each ear too quickly to discern the direction. Cetaceans have separated their ear bones (petrosal, tympanic, and ossicles) from the temporal bone and surrounded them by sinuses to isolate these complexes from the skull to hear directionally. While this was initially thought to be an adaptation for hearing high frequency sounds and thus an adaptation for echolocation (a capability restricted to the odontoceti, and associated with high frequency sounds), recent research has identified the pan bone/enlarged mandibular foramen (i.e. bony correlates of the mandibular fat pad) in many archaeocetes, including Ambulocetus, remingtonocetids, protocetids, and basilosaurids (Nummela et al. 2007) as well as many archaic toothed- and toothless mysticetes, such as Aetiocetus weltoni, Mammalodon, Eomysticetus, and even Herpetocetus. This led Nummela et al. (2007) to reason that, since neither archaeocetes or mysticetes have any anatomical features associated with echolocation, that this feature is probably instead related to underwater hearing in general, and not just echolocation.

Dentaries of various archaic mysticetes and an archaeocete, from Fitzgerald (2009).

The fact that most basal mysticetes have an enlarged mandibular foramen suggests that this is a feature inherited from basilosaurid ancestors. Interestingly, modern mysticetes are adapted for hearing low frequency sounds, which pass through dense bone without significant volume loss. While Uranocetus has a large mandibular foramen, the lateral wall is too thick to be useful for hearing anything aside from low frequency sounds (which Uranocetus is adapted to hear based on its cochlear structure; Steeman 2009). The exact same thing is seen in Herpetocetus, which is also adapted for low frequency hearing, but has a large foramen with a thick lateral wall. This suggests that at least in these later diverging taxa, that the large mandibular foramen was a vestigial feature perpetuated by phylogenetic inertia.

Lateral aspect of a (not so typical) mysticete (Eshrichtius robustus, the Gray Whale) skull and dentary in articulation, from Johnston et al. (2009).

Steeman (2009) reasoned that the mandibular foramen decreased in size to strengthen the dentary due to the intense forces involved during feeding. Above shows a gray whale skull and mandible in articulation, just to give you an idea of how strange the mysticete feeding apparatus is (exclusive of baleen). In any event, I've been thinking about this quite a bit recently, and got to add a (very short) synopsis of this in my manuscript revisions, but you'll hear about that soon enough.

References-
Deméré, T.A. and A. Berta (2008). Cranial anatomy of the toothed mysticete Aetiocetus weltoni and its implications for aetiocetid phylogeny. Zoological Journal of Linnean Society, 154(2): 308-352. PDF

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.

Fitzgerald, E.M.G. 2009. The morphology and systematics of Mammalodon colliveri (Cetacea:Mysticeti), a toothed mysticete from the Oligocene of Australia. Zoological Journal of the Linnean Society 110p.

Johnston, C., T. Deméré, A. Berta, J. St. Leger and J. Yonas. 2009. Observations on the musculoskeletal anatomy of the head of a neonate gray whale (Eschrichtius robustus). Marine Mammal Science PDF

Nummela, S., J.G.M. Thewissen, S. Bajpai, T. Hussain, and K. Kumar. 2007. Sound transmision in archaic and modern whales: anatomical adaptations for underwater hearing. Anatomical Record 290:716-733.

Steeman, M.E. 2009. A new baleen whale from the late Miocene of Denmark and early mysticete hearing. Palaeontology 52 :1169-1190.

4th Annual Earth Sciences Colloquium

More on Puijila later on this week - don't worry, I know its a hot topic, and I love seals, but I'll post on that later.

Last weekend I participated in the 4th annual Earth Sciences Colloquium, a student research conference done in our department for students and organized completely by students (go us!). In any event, I helped out quite a bit with it, and (gasp) was the technical chair for the conference - I communicated with all the presenters, organized the technical program, and moderated the oral sessions. It was nearly enough work so that I almost didn't present my talk, the subject of this post; the title page is below. I've included a bunch of slides I thought looked neat. On the title page are the logos of various institutions loosely involved with this research (and planned research projects/collaborations): J. Geisler (Georgia Southern U.), Rachel Racicot (Yale U.), and Frank Perry (Santa Cruz Museum).


Shockingly enough, I talked about cetaceans. Since it was for a more general audience, I spent a while talking about how awesome the whale fossil record is:



Here's a very general cladogram of whale phylogeny.



One of the really apparent morphological transformations is the posterior migration of the nares. In reality, I could have added a dozen or more transitional fossils in here.



And of course there's the whole hindlimb thing. I love how the pelvic girdle of Dorudon and other basilosaurids just kinda 'floats' in soft tissue.



On to actual data... I won't elaborate on this much, as this is the subject of my SVP abstract that I co-authored with Jonathan Geisler (Georgia Southern U.), and Frank Perry (Santa Cruz Museum of NH). Above is a partial skull of a late Pliocene pilot whale superimposed over a modern Globicephala macrorhynchus.



This is a recently collected gem - an articulated petrotympanic of a new genus of porpoise or basal delphinoid. This is associated with a partial skull that has yet to be completely prepared.


Lastly, here is a pie chart I made for fun, of all the different periotic morphotypes represented in the Purisima Formation (N = 120). I can probably get N up to 150 if I need to. In other news, my Master's thesis proposal has received its informal stamp of approval from my committee, so kickass.

Edit: I really need to use the spellcheck feature more judiciously; I typed up this post pretty fast, so the typos were pretty obvious. I apologize for all the grammer nazis. Just typos, not a sign of my incompetence.