San Diego Cetacean With An Underbite

[Scylla]

New species saved from oblivion at construction site finally described.

http://www.kpbs.org/news/2014/mar/13/extinct-california-porpoise-discovered-san-diego-h/

[Boesse]

FYI, I'm a coauthor on this paper - let me know if you guys have any questions about it!

[dinosaurbero]

This is cool!

[Scylla]

FYI, I'm a coauthor on this paper - let me know if you guys have any questions about it!

Bobby, I knew you would be interested in this, but I totally missed that you were one of the authors! I was wondering why it seemed that a couple of recent marine mammal papers made the news in a relatively short period of time. This one and the one on the evolution of sonar. Was it just random chance? Or was there a recent meeting that triggered the media attention? Also, could you just tell us more about these fossils? Thanks.

edit: http://www.cell.com/current-biology/abstract/S0960-9822(14)00199-7

Edited March 15, 2014 by Scylla

[Boesse]

Hey Scylla,

That was pure coincidence. I had a second paper come out on the same day, regarding the taphonomy of fossil marine vertebrates in the Purisima Formation near Santa Cruz. - a publication which was derived from my master's thesis. The other paper on the new Oligocene odontocete, Cotylocara macei, was a bit of a surprise, but I was pretty happy to see that published - the lead author, Jonathan Geisler, was my de facto cetacean 'mentor' when I was at Montana State U., because nobody at MSU works on marine mammals (hence why my master's work focused on taphonomy). Jonathan's helped me out quite a lot, and I am just pleased to see this new paper get into such a high profile venue.

The important thing about Cotylocara is that it is the earliest- phylogenetically speaking - odontocete to have the auditory anatomy of its skull analyzed in detail. Many other members of that group - all of which are known from North and South Carolina (and one or two from Europe, e.g. Patriocetus) - were generally relatively poorly documented, and many were also incomplete. Cotylocara, on the other hand, is known from a nearly complete skull and mandible, in addition to well preserved earbones. Because of this, it is the earliest-evolving (or, in cladistic lingo, earliest-diverging) odontocete to have an overabundance of evidence for echolocation.

Semirostrum, on the other hand, is not really archaic but is really "derived" (advanced) and specialized. It is an extinct genus within a modern family - the true porpoises (Phocoenidae). Most obviously, it's got this weird paddle-like toothless extension of its "chin" (mandibular symphysis), and the mandibles are medially fused, unlike all other phocoenids. It has a somewhat more elongate rostrum than extant phocoenids, but unlike many other fossil phocoenids- it has a symmetrical skull (derived phocoenids have a secondarily symmetrical skull, but retain asymmetrical sinuses). It also has these oblique wear facets on the outer edges of its teeth - which did not line up with opposing teeth. One of the authors, Brian Beatty, who specializes in mammalian tooth wear interpreted this as being caused by substrate interaction - wear from ingested sand and silt. There are also some large longitudinal canals in the chin, suggesting some sort of vascularization - either for a cornified structure or for increased innervation.

To us, all of this pointed to some sort of benthic feeding strategy where the chin was used to probe the seafloor for burrowing invertebrates (e.g. shrimp, other small crustaceans).

My contribution to the paper - other than producing the skeletal reconstruction and life restoration - was to report and describe fossils of Semirostrum from the Purisima Formation, including a skull and mandibles that I had found near Half Moon Bay.

[Scylla]

Thanks!