Spring in Otago

I'll admit I had originally planned on spending a couple hours tonight typing about bone eating worms and their impact on the fossil record, but I came down with a fairly severe headache this afternoon that is still fairly intense. Instead, I'll leave you with a couple of pretty pictures from outside my office.

 While all of you folks in the northern hemisphere have been enjoying your summer, my wife and I have completed our 10th straight month of winter - just as spring was starting in the US we flew down here, just as winter was beginning again in the south. This winter was nothing compared to the nastiness we left behind in Montana, but it is a bit of a bummer not really being able to go outside in a t-shirt and shorts for nearly a year (not that it stops kiwis, who will walk to campus in shorts and barefoot as long as its not raining and at least a few degrees above freezing).

This beautiful magnolia tree started blooming last week; it has got to be one of the prettiest plants I've ever seen before. I hope the flowers last more than a few days or so.

Field work in South Canterbury

Late last week I went with Ewan, fellow student C. H. Tsai, and fossil preparator Sophie White on a day trip to North Canterbury, to one of Ewan's most productive fossil localities in the Otekaike Limestone. We got up early and packed the department vehicle and trailer with all manner of equipment, including the masonry saw and the equipment Ewan Fordyce is famous for within paleontological circles - a chainsaw. The rock is so soft that it can be sawn through with a chainsaw fitted with a diamond-dust coated chain, which Ewan estimates has cut the amount of time needed for digging by 70% or so. Unfortuantely I don't have any photos of the fieldwork, as I left my camera at home. It turned out that we were so damn busy I wouldn't have had time to take many photos anyway.

There has been quite a bit of rain here on the South Island over the past few weeks, and Ewan had planned on making a trip up there anyway - just not so soon, as he wanted to wait for some even drier weather. Upon arriving at the quarry, we found a few bits of bone here and there, but at first, nothing too promising.

One fossil included both mandibles of a medium-sized baleen whale (est. 2 meter skull length?), and will require a large jacket, at least 1.5 m long. I found a probable odontocete mandible (probably not very complete), and a couple of bird bones. One specimen that I poked around at initially looked like an odontocete rib, but very quickly turned into a disarticulated penguin skeleton. This is probably not something like the recently described penguin Kairuku - which is well known from the older, underlying formation called the Kokoamu Greensand - but, according to Ewan, may turn out to be Platydyptes novaezealandiae, which is well known from the Otekaike Limestone.

The most exciting find of the day started out not very promising at all: a cluster of dolphin ribs and vertebrae. Sophie started cleaning it up and uncovered a nearly complete radius. I developed a pretty solid headache and as a result was working fairly slowly, but helped Sophie as best I could with the dolphin. After a while she uncovered a weird, large, conical element, and asked me what I thought it was; after a little more exposure, it was very clearly the rostrum of a medium-sized odontocete (something about the size of modern Tursiops). After a bit more cleaning, Sophie found the vomer and internal choanae, the squamosal, and a paroccipital process (exoccipital bone): they were in place, and indicated that the entire skull is present. This was very exciting; there is a large assemblage of odontocetes from the Otekaike, including a large squalodont, small tusked dalpiazinids, a squalodelphinid (labmate Yoshi Tanaka is working on these), Notocetus marplesi (considered by Fordyce (1994) to be a Waipatiid), the strange and beautifully preserved dolphin Waipatia, and a smattering of other very strange and incompletely known (but tantalizing...) taxa I won't talk about any further. The weirdest part about this dolphin was the rostrum: it was very short, and apparently toothless. The skeleton includes the skull, a mandible, radius, many vertebrae and ribs, and a scapula.

We finished the day off by excavating everything but the block with the dolphin and the baleen whale; we would have to return later to excavate those. We left with a half dozen small blocks and two plaster jackets (the penguin skeleton and another partial dolphin). At the moment, Ewan is getting ready to return to the field (tomorrow), with Tsai, Yoshi, and Sophie; over the weekend, I started getting some strange rashes caused by a chicken pox-like virus, and won't really be able to make it out into the field with them, unfortunately.

New Zealand field work: Paleocene of Wangaloa

Last week, Ewan invited two other students and I to do some fieldwork on the coast south of Dunedin. We would go prospecting in lower Paleocene (er... Palaeocene) strata, approximately 62 Mya (pretty old stuff!). This is a particularly interesting period of time in general due to faunas recovering from the K/Pg extinction and reduction in competition and selective pressures for some clades, but the Paleocene of New Zealand has already yielded a number of interesting shark finds, and most importantly - the world's oldest and most primitive penguin fossils (Waimanu).

Yoshi Tanaka along the cliffs. Our target is the point in the distance and the stacks of concretions on the shoreline.

My adviser Ewan Fordyce examining the base of the cliffs.

Yoshi and I using the pionjar rock drill to extract a small vertebrate bone (or tooth).

Ewan using the rock drill. The drill weighs about 70 lbs, has an 18" bit, and is a percussive drill: it is effectively a combination drill and jackhammer. In other words, it's a jackhammer with a rotating chisel bit.

The skeletal element in question is in a shell-rich unit in extremely hard, calcium carbonate-cemented sandstone, and located about 4-5" to the right of the bit. We're drilling a couple holes here in a layer just below it.

Due to the low rotation speed of the bit, someone with gloves (Ewan in this case) can hold the bit in place in order to start a bore hole.

The rock drill is a bit of a beast to work with and bucks around a lot while at the same time being awkwardly proportioned and weighted and spitting out oil and foul smelling exhaust; it is relatively straightforward to use vertically, but using it at an angle is a constant struggle.

Fellow student Cheng-Hsiu Tsai starts a second bore hole.

Step two: after the bore holes are drilled, pairs of wedges with a half-circle cross section are placed in, and a wedge between them.

Another view of the wedges. At this stage, the wedges can be driven in by hammer (the long way), or a non-rotating "hammer bit" can be placed into the business end of the rock drill. This bit has a cup on the end, and if properly coaxed, will hammer the wedge into the rock. With two wedges, the rock drill has to be alternated from one to the other to ensure even splitting.

Yoshi (left), myself (middle), and Tsai (right) examining a tiny bit of bone in a very, very large boulder.

This was a pain in the ass: at shoulder height, three people are required, and a hook can be looped over a support - in this case an estwing "super pick"; not only does this allow for support, but the two can also use the cross beam support to push the drill into the rock. Minutes later, Yoshi unfortunately found another bone - this time, at eye level.

Yoshi (right), Tsai (middle) and myself (left) after an arduous walk back with ~120 pounds of rock drill & bits and wedges, and ~60 pounds of concretion fragments (with tiny bones). Tsai had some awesome oil splatter on his face (from the rock drill) which is only partially cleaned off here.

Parabalaenoptera baulinensis: the fossil baleen whale from Bolinas, Marin County, California

Until relatively recently, fossil balaenopterids have been avoided by modern paleocetologists like the plague. Modern balaenopterids include the humpback whale (Megaptera novaeangliae) and species of Balaenoptera, including the Minke, Blue, Fin, and Sei whales. Although balaenopterids have very distinctive and easy to identify crania, they are really only common in latest Miocene and Pliocene marine rocks, and early work by Kellogg and others yielded fossil baleen whales with much more primitive skulls, formerly called "cetotheres" sensu lato, also jokingly referred to by some paleocetologists as "Kelloggitheres".

Fossil balaenopterids have been plagued by a particularly nasty taxonomic situation since the late nineteenth century, when P.J. Van Beneden began describing fossil mysticetes collected during the construction of a series of forts around Antwerp. Unfortunately, many of these fossils which names like Plesiocetus and Herpetocetus are based upon were isolated finds, which were subsequently arranged into type 'series' with other skeletal parts based on a preconceived notion of what each taxon should have looked like. The end result was a series of chimaeras, some of which represented by potentially informative but often fragmentary material, lacking type specimens, the associated names of which have been dragged through the systematic mud by subsequent authors, and not allowed to simply die gracefully.

 

The skull and mandibles of the holotype specimen of Parabalaenoptera baulinensis from the late Miocene Santa Cruz Mudstone of Marin County, California.

Many of these fossil balaenopterids are difficult or impossible to diagnose: which specimen of the series would you designate as a lectotype? Is that specimen diagnostic? What do you do with the other specimens? Is an isolated mandible diagnostic or not? What about a piece of a braincase with unassociated bullae? According to Bosselaers and Post (2010), many of Van Beneden's taxa are based on "syntype" collections that are not possible to unambiguously diagnose: diagnostic syntype elements are either too incomplete, or include multiple diagnostic elements but from multiple individuals (and occasionally taxa; i.e. a balaenid bulla was grouped with the lectotype mandible of Herpetocetus scaldiensis by Van Beneden). Accordingly, Bosselaers and Post (2010) declared all of Van Beneden's Pliocene balaenopterid taxa to be nomina dubia: for the time being, I think this is probably the "safe", appropriate, and right thing to do.

The discovery and description of Parabalaenoptera baulinensis was one of the first important advances in balaenopterid paleontology: it was one of the first balaenopterids described from a nearly complete skull with associated mandibles and postcrania. Some other previously published fossil balaenopterids were described on somewhat complete remains: Megaptera miocaena (late Miocene of California), Megaptera hubachi (late Miocene of Chile), Protororqualus cortesii (Pliocene of Italy), "Balaenoptera" cortesi var. portisi (Pliocene of Italy), and Cetotheriophanes capellinii (...also Pliocene of Italy). Unfortunately, the holotype skeleton of Protororqualus was destroyed during bombing in World War II, and M. miocaena only includes earbones and a braincase; furthermore, the other Italian balaenopterids have been plagued with nomenclatural issues for over a century (see Demere et al. 2005).

The exhibit at the Drakes Beach visitor's center showing the holotype skeleton of 

Parabalaenoptera baulinensis.

In 1973, a large mysticete skeleton was discovered by Carl Zeigler of the College of Marin, weathering out of cliffs near Bolinas in Marin County, California. Bolinas is a quaint artist community on the Marin County coast and has changed little since the 1960's and 70's; it is predominantly settled by ex-hippies, who generally don't like visitors from out of county, and have continually removed the exit sign for "Bolinas: 2 miles" off of highway 1, to the point where the California Dept. of Transportation (CalTrans) has given up putting up new signs. Tales abound of visitors with out of county or out of state license plates having car tires popped or vandalized, and nails and other tire-popping objects being intentionally laid out onto dirt roads in town. My car had a San Rafael Honda license plate holder, so I never had this problem.

 

The assembled holotype skull of Parabalaenoptera at California Academy of Sciences, photographed by fellow Otago Ph.D. student Felix Marx.

Exposed along the southern tip of Point Reyes is a unit formerly identified as the early late Miocene Monterey Formation; this was subsequently reevaluated after Domning (1978) suggested that sea cow fossils from the Bolinas locality were too derived to be from such an old unit. Afterwards, microfossils suggested a much younger age, closer to the Mio-Pliocene boundary (6-6.8 Million years old), and the formation was reidentified as the Santa Cruz Mudstone, which has only been mapped in Santa Cruz County.

 

Anterior view of Parabalaenoptera.

The fossil occurred in indurated, blocky mudstone, and was collected over a ten year period as the blocks incrementally eroded from the cliff. The lead authors - Gordon ("Gordie") Chan and Carl Zeigler of the College of Marin in Kentfield, and their field assistants - would have to travel over the hill and out to Bolinas (nearly an hour's drive through some of the windiest vomit-inducing roads in Northern California) on a monthly basis during the summer, and much more often during the winter during periods of intense erosion, and sometimes daily, anticipating falling blocks. After collection, the blocks were prepared, and some were glued together - but left as a series of blocks that could be lined up and assembled. The holotype was prepared at College of Marin, and eventually molded, casted, and donated to the California Academy of Sciences. Mounted casts of Parabalaenoptera baulinensis are currently on display at College of Marin in Kentfield and at the Drake's Beach visitor center at Point Reyes National Seashore. Sadly, before the paper could be published on the fossil - Carl Zeigler and Gordon Chan passed away. Chan passed away in 1996 of Lou Gehrig's disease; I could not find information on Zeigler, though I seem to recall hearing that he was killed by a drunk driver. Dr. Lawrence Barnes of the Los Angeles County Museum of Natural History finished the manuscript and brought it to publication in the California Academy of Sciences in 1997.

 

The braincase and vertex of Parabalaenoptera.

Parabalaenoptera baulinensis is a medium-sized balaenopterid with a 2.2 meter skull, slightly larger than minke whales (Balaenoptera acutorostrata; a 10 meter long whale with a 2m skull), but has a number of features that are too divergent to warrant inclusion within humpbacks (Megaptera) or Balaenoptera. These include the very elongate and somewhat swollen zygomatic processes, narrow intertemporal region (the skull is less 'telescoped than in modern balaenopterids), and extremely long and narrow nasal bones. The mandibles are strongly outwardly bowed like in Megaptera, and have an elongate coronoid process - somewhat like blue and fin whales (Balaenoptera musculus and physalus). Many of these features suggest that Parabalaenoptera baulinensis was capable of lunge feeding just like modern rorquals. It is additionally convergent with Balaenoptera musculus in having a supraorbital process of the frontal that is somewhat triangular and narrows laterally, whereas in Balaenoptera and Megaptera, the posterior and anterior margins are either parallel, or the posterior margin is perpendicular to the midline. Unfortunately, the holotype specimen is not preserved very well, and it appears that a significant amount of bone was accidentally removed or ground away during preparation, and details of the basicranium are almost totally indiscernible. Parabalaenoptera has been found in many phylogenetic analyses to be a stem-balaenopterid - in other words, a primitive member of the clade (family Balaenopteridae) that does not belong to the clade formed by humpback whales and modern species of Balaenoptera - the Megaptera + Balaenoptera clade, if you will. These two modern genera have been traditionally grouped into the "Megapterinae" and "Balaenopterinae" - Zeigler et al. (1997) even went so far as to name a new subfamily, the Parabalaenopterinae. However, given that none of these subfamilies have really shown to be stable or even consistent in cladistic analyses, it's unclear what the utility of such taxon names even is.

 

Reconstruction of the holotype skull and mandibles of Parabalaenoptera. Unfortunately, certain features (e.g. squamosal morphology) of the actual skull don't really look like how they're portrayed in this figure. From Zeigler et al. (1997).

Nevertheless, the description of Parabalaenoptera was a hallmark in balaenopterid paleontology; however, given the stagnated taxonomic situation of fossil balaenopterids, little else was published on fossil balaenopterids until Michelangelo Bisconti started revisiting Italian fossils starting in 2007. In the last five years, a number of informative balaenopterid finds have been described - but it is only the tip of the iceberg. Perusing late Miocene and Pliocene marine mammal assemblages in Museums, it is apparent that balaenopterids comprise nearly two-thirds of the more recent baleen whale fossil record (it is at least the case for California marine mammal assemblages). In California, at least four to five unpublished balaenopterids await description from the Pliocene alone. Additional fossils that may represent Parabalaenoptera - potentially a new and slightly younger species - have been collected from the Purisima Formation near Santa Cruz (and are in much better condition than the holotype). The future of balaenopterid paleontology is bright!

References

Bosselaers, M., and Post, K. 2010. — A new fossil rorqual (Mammalia, Cetacea, Balaenopteridae) from the Early Pliocene of the North Sea, with a review of the rorqual species described by Owen and Van Beneden. Geodiversitas 32:331-363. 

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


Domning, D. P. 1978. — Sirenian evolution in the North Pacific Ocean. University of California Publications in Geological Sciences 18:1-176.


Zeigler, C. V., Chan, G. L., and Barnes, L. G. 1997. — A new late Miocene balaenopterid whale (Cetacea: Mysticeti), Parabalaenoptera baulinensis, (new genus and species) from the Santa Cruz Mudstone, Point Reyes Peninsula, California. Proceedings of the California Academy of Sciences 50(4):115-138.