Feresa: The Growling Wolf-Dolphin

The dolphin Feresa attenuata has been bestowed with dreadfully stupid common names. Feresa has been recognized as distinct from Orca since Gray (1871), which makes "Pygmy Killer Whale" both inappropriate and archaic. The alternative "Slender Blackfish" is actively misleading as the superficially similar Pseudorca is more slender (Reeves et al. 2002) and well-lit color photographs in Rossi-Santos et al. (2006) show that the species is actually brown, contra every illustration. I'll be calling the dolphin "Feresa" from here on out (I'm also not too fond of  "attenuata") as my alternate suggestion in the title is a tad verbose.

Feresea... maybe. This species can be distinguished from Pseudorca by having a proportionally larger dorsal fin (2 base lengths away from the blowhole vs. 2.5) and by having a clearly demarcated cape; Peponocephala can be distinguished by having pointed flipper tips, a pointed head when viewed from above, and no white extending around the face (Baird 2010). I think this is the case in the above photo, but I'm not entirely certain. Photo by Gary L. Friedrichsen from WoRMS.

Feresa is one of the most poorly-known toothed whales (McSweeney et al. 2009) and single sightings or strandings are still viewed as deserving publication (Baird 2010). Prior to 1954, the species was known from only two skulls (Reeves et al. 2002), making it extremely poorly-known even compared to beaked whales. What makes this absolutely shocking is that Feresa is not a cryptic species. They are known from the tropics and subtropics worldwide, are easy to detect in visual surveys, do not take extended dives, and (contra Leatherwood et al. 1982) do not avoid vessels (McSweeney et al. 2009). While their surface behavior is normally subdued compared to other dolphins, they have been observed jumping high above the surface and even riding on bow waves (Reeves et al. 2002). It appears that while a deep-water habitat and confusion with Pseudorca and Peponocephala can explain the lack of observations to a degree, the main factor is probably the species being rare (McSweeney et al. 2009).

In 1965 - a little over a decade after the external appearance of the animal became known - Feresa was held in captivity. Pryor (1991) remarked that one individual behaved "more like a wolf than a normal dolphin" would "growl and snap like as canid" and "not hesitate to attack people and other cetaceans". Since when are cetaceans capable of growling? This behavior has led some to presume that Feresa preys on mammals in the wild (Leatherwood et al. 1982) and aggression towards other dolphins has been observed whilst individuals were trapped in tuna seines (Reeves et al. 2002). Considering that both situations occurred in cramped and undoubtedly stressful environments, I think it is completely unfounded to conclude that Feresa is a pugnacious marine mammal-killing macropredator with the available evidence. Stomach contents have included squid and fish (Rodríguez-López and Mignucci- Giannoni 1999; Zerbini & Santos 1997)

Feresa skeleton. From Wikipedia Commons.

The skeleton of Feresa does appear superficially Orca-like, however, it is not a particularly close relative, hence my strong dislike of the "Pygmy Killer Whale". There is some disagreement as to how closely they are related; Slater et al. (2010) places Orcinus (and Orcaella) as the most basal delphinids, however Vilstrup et al. (2011) consider both to be both members of the clade Globicephalinae, but with Orca as the most basal member and Feresa as a derived member and close relative of Peponocephala and Globicephala. This seems like a very interesting group, and perhaps I'll give it some more coverage.


References:

Baird, R. W. (2010). Pygmy Killer Whales (Feresa attenuata) or False Killer Whales (Pseudorca crassidens) Identification of a Group of Small Cetaceans Seen off Ecuador in 2003. Aquatic Mammals 36(3), 326-327. Available.

Gray, J. E. (1871). Supplement to the Catalogue of seals and whales in the British Museum. Available.

Leatherwood, S., Reeves, R. R., Perrin, W. F., & Evans, W. (1982). Whales, dolphins, and porpoises of the eastern north pacific and adjacent arctic waters (NOAA Technical Report NMFA Circular 444). Washington, DC: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service. Partially Available.

McSweeney, D. J., Baird, R. W., Mahaffy, S. D., Webster, D. L., and Schorr, G. S. (2009). Site fidelity and association patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Island. Marine Mammal Science 25(3), 557-572. Available.

Pryor, K. (1991). Mortal remains: Studying dead animals. In: Pryor, K. & Norris, K. S. (eds.) Dolphin Society: Discoveries and Puzzles. University of California Press: Berkeley. Available.

Reeves, R. R., Stewart, B. S., Clapham, P. J., & Powell, J. A. (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf: New York.

Rodríguez-López, M. A. & Mignucci-Giannoni, A. A. (1999). A stranded pygmy killer whale (Feresa attenuata) in Puerto Rico. Aquatic Mammals 25(2), 119-121. Available.

Rossi-Santos, M., Baracho, C., Neto, E. S., & Marcovaldi, E. (2006). First sightings of the pygmy killer whale, Feresa attenuata, for the Brazilian coast. JMBA2 - Biodiversity Records. Available.

Slater, G. J., Price, S. A., Santini, F., and Alfaro, M. E. (2010). Diversity versus disparity and the radiation of modern cetaceans. Proceedings of the Royal Society B 277(1697), 3097-3104. Available.

Vilstrup, J. T., Ho, S. Y. W., Foote, A. D., Morin, P. A., Kreb, D., Krützen, M., Parra, G. J., Robertson, K. M., de Stephanis, R., Verborgh, P., Willerslev, E., Orlando, L., & Gilbert, M. T. P. (2011). Mitogenomic phylogenetic analyses of the Delphinidae with an emphasis on the Globicephalinae. BMC Evolutionary Biology 11(65). Available.

Zerbini, A. N. & Santos, M. C. O. (1997). First record of the pygmy killer whale Feresa attenuata (Gray, 1874) for the Brazilian coast. Aquatic Mammals 23(2), 105-109. Available.

Eocetus, "Eocetus", and Friends

Update (January 28, 2014): "Eocetus" wardii is now Basilotritus wardii. More on my new post, The Third King.


I was shocked that Uhen (2010) remarked that Basilosaurus drazindai and Basiloterus hussaini "probably represent protocetids... akin to Eocetus". This would place the whales outside Pelagiceti and imply that the now-questionable basilosaurids were potentially capable of walking on land, despite being enormous. Unfortunately, other mentions of this revised placement give no further details (Uhen 2008, Uhen et al. 2011) and Uhen (2010) further states the placement is "difficult to determine with certainty" due to scarce materials. I suspect the hypothesis will not be officially discussed until further material is found and/or described... which won't stop me from wildly speculating.

Lumbar vertebrae in right lateral view. From left to right: "Eocetus" wardii (from Uhen 1999), Basiloterus hussaini, and Basilosaurus drazindai - note that the latter-most may be an anterior caudal (from Gingerich et al. 1997). For comparison: Basilosaurus isis vertebrae.

In the description of Basilosaurus drazindai, Gingerich et al. (1997) note a number of "primitive retentions" which resemble the morphology of "generalized archaeocetes": long neural spine and arch; broad, almost-horizontally placed, anterior-projecting metapophyses which project beyond the anterior edge of the vertebral centrum; and paired, posterolateral processes of the neural arch. Aside from the last trait (which I can't confirm without a dorsal view), all of these traits are present in "Eocetus" (Uhen 1999). Additionally, "Eocetus" has elongated transverse processes, unlike the condition of Basilosaurus (Uhen 1999); however, B. drazindai has processes with a 15.5 cm long base (they broke off) relative to the 30 cm centrum (Gingerich et al. 1997), and so probably had a similar, albeit slightly less extreme, condition. The only criterion for placing B. drazindai in the genus Basilosaurus was the size and shape of the centrum (Gingerich et al. 1997), and while they are uncannily similar in shape, everything else seems to be pointing towards a relationship with "Eocetus".

Lumbar vertebrae in anterior view. Ditto order.

As for awkward middle-child Basiloterus, it appears to have a centrum which is slightly more elongated than that of "Eocetus", however the neural arch and maybe the neural spine appear to be narrower. The metapophyses are upwardly-angled (Gingerich et al. 1997), less broad, less anterior-projecting, but still appear to extend past the centrum. The posterolateral processes are absent (Gingerich et al. 1997). The base of the transverse process is 9.3 cm long relative to a 19.5-20 cm centra (Gingerich et al. 1997), proportionally similar to Basilosaurus drazindai. The placement of Basiloterus is thus not clear, and perhaps it was a basilosaurid or an even more derived protocetid.

Maiacetus inuus, a basal "protocetid" (Uhen 2011). From Wikipedia Commons.

Protocetidae is a blatantly paraphyletic "family" of extinct cetaceans from Eocene coastal marine deposits with hip and femur morphology indicating amphibious capabilities (most of the time) and no evidence of flukes (Uhen 2010). Uhen (1999) appears to think that "Eocetus" wardii had weight-bearing hips, however Uhen (2010) refers to them as "moderately reduced" and regarded the species as possibly non-amphibious. This is perhaps not surprising since Eocetus, "Eocetus", and an unnamed Pisco Formation species are the sister group of Pelagiceti (Uhen et al. 2011). This could make them closer relatives of Dorudon than Maiacetus, and raises the question of how many typical protocetid traits they actually exhibited. Perhaps they were entirely aquatic tail-based swimmers which just happened to have fairly large vestigial legs.

Dorudon atrox. From Wikipedia Commons.

The scare quotes around "Eocetus" hint at a taxonomic misadventure. "E." wardii was assigned to its genus by Uhen (1999) based on comparisons of its skull and vertebrae to Eocetus schweinfurthi; the problem is, the holotype of E. schweinfurthi is an isolated skull and it is not possible to determine whether the vertebrae referred to it actually represent the species (Geisler et al. 2005). There is overlapping skull material (Uhen 1999), but Geisler et al. (2005) apparently regarded it as too incomplete to warrant unambiguous placement in the genus. Somehow, "Eocetus" and Eocetus formed a clade in phylogenetic analyses (Geisler et al. 2005, Uhen et al. 2011), making it probable that future discoveries will confirm their close relationship.

"Eocetus" wardii is clearly related to unnamed Pisco Formation material which exhibits the same distinctive traits (moderate centrum elongation, elongated neural arches and spines and transverse processes, strange pock-marked texture) with the only difference being that the unnamed material is 35% smaller (Uhen et al. 2011). The Egyptian vertebrae dubiously assigned to Eocetus schweinfurthi (figured in Uhen 1999) also seem quite similar (including the pock-marks), and if it is also a member of this clade, it would indicate a sizable trans-oceanic range. This in turn could be taken as evidence of the whales being largely pelagic... of course this is quite speculative.

There of course remains much to be known about these cetaceans, and perhaps future discoveries will be enlightening as to how similar they were to the pelagic cetaceans, as well as the origins of Pelagiceti. I really hope it turns out that a Basilosaurus-sized animal could walk on land.


References:

Geisler, J. H., Sanders, A. E., and Luo, Z-X. (2005). A New Protocetid Whale (Cetacea: Archaeoceti) from the Late Middle Eocene of South Carolina. American Museum Novitates 3480, 1-65. Available.

Gingerich, P. D., Arif, M., Bhatti, M. A., Anwar, M., & Sanders, W. J. (1997). Basilosaurus drazindai and Basiloterus hussaini, new Archaeoceti (Mammalia, Cetacea) from the middle Eocene Drazinda Formation, with a revised interpretation of ages of whale-bearing strata in the Kirthar Group of the Sulaiman Range, Punjab (Pakistan). Contributions from the Museum of Paleontology, University of Michigan 30 (2), 55-81. Available.

Uhen, M. D., Pyenson, N. D., Devries, T. J., Urbina, M., and Renne, P. R. (2011). New middle Eocene whales from the Pisco Basin of Peru. Journal of Paleontology 85(5), 955-969. doi: http://dx.doi.org/10.1666/10-162.1

Uhen, M. D. (2010). The Origin(s) of Whales. Annual Review of Earth and Planetary Sciences 38, 189–221. Available.

Uhen, M. D. (2008). Basilosaurids. In: Perrin, W. F., Würsig, B., and Thewissen, J. G. M. (eds.) Encyclopedia of Marine Mammals, Second Edition. Elsevier: Burlington, Massachusetts. Available.

Uhen, M. D. (1999). New Species of Protocetid Archaeocete Whale, Eocetus wardii (Mammalia: Cetacea) from the Middle Eocene of North Carolina. Journal of Paleontology 73(3), 512-528.

Weems, R. E., Edwards, L. E., Osborne, J. E., and Alford, A. A. (2011). An occurrence of the protocetid whale "Eocetus" wardii in the Middle Eocene formation of Virginia. Journal of Paleontology 85(2), 271-278. Available.

Picture of the Indiscriminate Interval #000008 - Eurhinodelphis longirostris

Eurhinodelphis longirostris at the American Museum of Natural History.

The most striking trait of Eurhinodelphidae is a toothless extension of the rostrum beyond the mandible (Lambert 2005), superficially similar to the bills of Billfish and Swordfish. Oddly, this morphology was speculative for a period of time (Kellogg 1925) although it has apparently been confirmed in several species as of Lambert (2005). Unfortunately, information on eurhinodelphids is scant and/or difficult to access and, among numerous other basics of their biology, I really don't know what the function of the extended rostrum would be. The only suggestion I could find is from one professor Abel who speculated that the cetaceans "swam on the surface of the sea, where they captured food - probably fishes - in much the same manner as does the skimmer (Rhynchops) [sic] among birds" (Anonymous 1909). Somehow, I find this even less plausible than azhdarchids-as-skimmers. On a curious note, there is a cetacean with the reverse of eurhinodelphid morphology (mandible extending past rostrum) unofficially known as the... skimmer porpoise.

Phylogenetically, eurhinodelphids have bounced around from being considered stem-ziphiids, the sister group to Delphinida, and the sister group to Squalodontidae + Squalodelphidae (Geisler et al. 2011 - citing various); within Geisler et al. (2011), they were placed outside crown-Odontoceti¹ in an unconstrained analysis and as the sister group of platanistoids in a constrained analysis. The authors regarded the latter position as more probable and placed eurhinodelphids within the new group Synrhina, which includes most odontocetes except for Sperm Whales and assorted extinct taxa. Whatever their placement, eurhinodelphids are certainly close relatives of living toothed whales, despite that whole extinct thing.

¹ It actually states they "did not fall inside crown Cetacea", but this is a typo. Otherwise, they'd be Miocene Archaeocetes. 

Eurhinodelphis longirostris seems to have an unusually long neck for a cetacean. The cervical vertebrae are not fused (Kellogg 1925), however this is a surprisingly common trait shared with river dolphins, monodontids, rorquals, and gray whales (Tinker 1988). The neck of E. longirostris appears to be proportionally longer than those of the baleen whales and Narwhal and is probably comparable to those of the Beluga and Dorudon. River dolphin skeletons are hard to find, but it seems likely they have similarly proportioned necks. It seems that Eurhinodelphis wasn't a total freak, well, except for the snout.

The Theatrical Tanystropheus covered Eurhinodelphis as well, and it doesn't even overlap that much!

References:

Anonymous. (1909). Notes. Nature 2088 (82), 16. Available.

Geisler, J. H., McGowen, M. R., Yang, G., Gatesy, J. (2011). A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea. BMC Evolutionary Biology 11 (112). Available.

Kellogg, R. (1925). On the occurrence of fossil porpoises of the genus Eurhinodelphis in North America. Proceedings of the U. S. National Museum 66(26), 1-40. Available.

Lambert, O. (2005). Les dauphins longirostres et les baleines à bec du Néogène de la région d’Anvers: systématique, phylogénie, paléo-écologie et paléo-biogéographie. Doctoral Thesis. Partially Available.

Tinker, S. W. (1988). Whales of the World. E. J. Brill Publishing Company: New York. Partially Available.

Picture of the Indiscriminate Interval #000007 - Narwhal

Monodon monoceros at the American Museum of Natural History.

Narwhals are a bit strange even by cetacean standards. I'll let the title of this Tet Zoo article speak for itself: "A 3-m tooth that can bend 30 cm in any direction and is hypersentitive to salinity, temperature and pressure... and the sonic lance hypothesis".

They get weirder. Without the tooth (or sometimes, teeth) it is difficult to picture how this flat-skulled cetacean could be the same as a bulbous-headed Narwhal. As brought up in my Dorudon post, there are colossal amounts of soft tissue involved.

Another soft-tissue feature not hinted at by the skeleton are unusually shaped flukes... in males. Fontanella et al. (2010) suggest that the concave leading edge and lack of sweepback of the flukes increases lift and thrust to compensate for the drag caused by the tusk in males. The implications of the occasional tusked female narwhal were not discussed by the authors.

One female Narwhal was estimated to be 114.8 (± 10.2) years old (Garde et al. 2007) which, if correct, would make Narwhals the third oldest known mammals after humans (122 years) and Bowhead Whales (211 years?). Garde et al. (2007) used a sample of 75 individuals (15 juvenile) from a heavily hunted population, and subsequently speculated that Narwhals in other populations could potentially reach "considerably higher" ages. As for methodology, Garde et al. (2007) used aspartic acid racemization rate in the eye; this method was also used to calculate the extreme age estimate for Bowheads (George et al. 1999), and ages of over a hundred years have subsequently been supported by bomb lance fragments (George and Bockstoce 2008) and ovarian corpora counts (George et al. 2011). So it looks probable that aspartic acid racemization does not provide grossly inaccurate estimates of old age - why would Narwhals live to be centenarians? Garde et al. (2007) note that Narwhals and Bowheads are both year-round Arctic residents and speculate that their extreme longevity is an adaptation to drastic changes is climate. While an interesting idea, there does not seem to be much data available on cetacean longevity (Table 2 in Garde et al. 2007 has only 12 out of ~80 species) and Narwhals are apparently not far older than other cetaceans (for instance, Orcas apparently live to be 90). It could be possible that further investigation into cetacean longevity will reveal that lifespans of over a hundred years are perfectly normal.

References:

Fontanella, J. E., Fish, F. E., Rybczynski, N., Nweeia, M. T., & Ketten, D. R. (2010). Three-dimensional geometry of the narwhal (Monodon monoceros) flukes in relation to hydrodynamics. Marine Mammal Science 27(4), 889-898. Available.

Garde, E., Heide-Jørgensen, M. P., Hansen, S. H., Nachman, G., and Forchhammer, M. C. (2007). Age-specific growth and remarkable longevity in Narwhals (Monodon monoceros) from West Greenland as estimated by Aspartic Acid Racemization. Journal of Mammalogy 88(1), 49-58. Available.

George, J. C., Follmann, E., Zeh, J., Sousa, M., Tarpley, R., Suydam, R. Horstmann-Dehn, L. (2011). A new way to estimate the age of bowhead whales (Balaena mysticetus) using ovarian corpora counts. Canadian Journal of Zoology 89(9), 840-852. doi: 10.1139/z11-057

George, J. C., and Bocktoce, J. R. (2008). Two historical weapon fragments as an aid to estimating the longevity and movements of bowhead whales. Polar Biology 31(6), 751-754. Available.

George, J. C., Bada, J., Zeh, J., Scott, L., Brown, S. E., O'Hara, T., & Suydam, R. (1999). Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization. Canadian Journal of Zoology 77, 571-578.

Dorudon Was Not A Monster

The external shape of cetaceans is very much defined by blubber and other soft tissues†. In a previous article, I argued that if a cetacean were to be naïvely reconstructed by what the skeleton (or rotten carcass) 'suggests', it could end up looking more like a reptilian horror than, say, a fat, charismatic monodontid we all know and love. It's below the monstrous footnote.

† But don't just take my word for it - the Woods Hole Oceanographic Institution has excellent CT scans showing the interplay between skeleton and external shape. Aside from the caudal peduncle and (occasionally) the tip of the snout, toothed whales are cocooned in blubber. The heads of the False Killer Whale and Narwhal provide sufficiently extreme examples. Contrarily, the Minke Whale has a skull which roughly correlates with the external shape... in a dorsal view; shrink-wrapping the skull at a different angle shows that soft tissue still plays a considerable role in determining overall shape. Dorudon probably looked a great deal more like toothed than baleen whales, however more basal 'baleen' whales (stem-Mysticeti) lacking the hyper-derived skull are potentially very informative. Thanks to Markus Bühler for the link.

This intentionally incompetent Beluga bears an unexpected similarity to some reconstructions of Dorudon... notwithstanding the blowhole and fur, of course. This is partially due to the offending illustrations depicting Dorudon atrox with almost no blubber, which makes as much sense as reconstructing a fossil bird without feathers. The other factor is that skeletally, Dorudon is broadly similar to modern toothed whales, despite being basal to the toothed/baleen whale split:

Delphinapterus leucas skeleton from Wikipedia Commons.

Dorudon atrox2, taken and modified from Wikipedia Commons. Note that the arm is held at an angle and was not, in fact, really really short.

White-sided dolphin, taken and modified from Wikipedia Commons.

Above Dorudon is a Beluga, which is similar in size and also has non-fused neck vertebrae (Uhen 2004). What I find particularly striking is the similar depth of the ribcages and the comparatively short spinous processes of Dorudon. Beaked whales also have non-fused neck vertebrae and Ziphius in particular has been compared in size to Dorudon (Uhen 2004) - judging by this photo of Ziphius, the species also has a deep ribcage and relatively enormous spinous processes†. Below Dorudon is a Lagenorhynchus dolphin (either L. acutus or L. obliquidens) which has numerous highly derived characteristics (Buchholtz and Schur 2004), and thus makes for strong contrast. The ribcage seems relatively streamlined and shallower and the spinous processes of the vertebrae are extremely developed. There's still a broad similarity between Dorudon and that highly derived taxon, which makes portrayals of Dorudon as some anguilliform quasi-reptilian horror appear increasingly bizarre.

† Aside from which, the lumbar/anterior caudal region gives off a strong Basilosaurus vibe due to the elongated vertebral bodies and lack of interlocking processes. Hmm.


So why have I been talking so much about Dorudon atrox as opposed to D. serratus, Chrysocetus, Ancalecetus, or some other 'dorudontine'? Dorudon atrox is the best-known 'archaeocete', and at present "[r]elationships among the Dorudontinae are not well-defined, either by morphology or stratigraphy... [i]n addition, the relationships among the Dorudontinae cannot be determined until the taxa within the Dorudontinae are clearly delimited" (Uhen 2004). Additionally, it's become apparent that I've been citing Uhen (2004) quite a bit so far, and that source just so happens to be a massive, book-length treatise on D. atrox which is freely available. The publication is outstanding... aside from the frontispiece, which was credited as being made in cooperation with the author, but seems to contradict several points made within the publication and looks more like a zombie than a fairly close relative of extant cetaceans.

I think I can do Dorudon a bit more justice... next post.

Well, I've actually already done it for the banner - but the explanation will be in the following post! Which won't be in a month, I swear.

References:

Buchholtz, E. A., and Schur, S. A. (2004). Vertebral osteology in Delphinidae (Cetacea). Zoological Journal of the Linnean Society 140, 383–401. Available.

Uhen, M. D. (2004). Form, Function, and Anatomy of Dorudon atrox (Mammalia, Cetacea): An Archaeocete from the Middle to Late Eocene of Egypt. University of Michigan Papers on Paleontology 34, 1-222. Available.

Of the Monstrous Pictures of Whales

"But it may be fancied, that from the naked skeleton of the stranded whale, accurate hints may be derived touching his true form. Not at all. For it is one of the more curious things about this Leviathan, that his skeleton gives very little idea of his general shape"

- Herman Melville. Moby-Dick; or, The Whale. Chapter 55.

Suspiciously similar to a photo taken by Markus Bühler.

What would be made of cetaceans if they were known only from fossil bones? The reconstruction above shows how a mildly unusual Sperm Whale (Physeter macrocephalus) may appear in this hypothetical alternate reality. The unfortunate cetacean is subjected to almost unadulterated 'shrink-wrapping', with the exception of the 'forehead' region. This area of the skull has a strongly concave surface which would look highly implausible on an aquatic creature. What the angle of the reconstruction fails to show is that the concavity is part of a basin-like depression which covers most of the Sperm Whale's cranium; coupled with crests for the attachment of the maxillonasalis muscle, it should be clear that vast amounts of soft tissue were present. The soft tissue is so considerable in mass that Clarke (1978) referred to the head of a Sperm Whale as "largely snout and the crest of the skull necessary to support it". 

A huge nose can be inferred from a Sperm Whale skeleton, yet Melville's assertion is still likely correct. A sloping, prow-like snout would probably be viewed as most likely due to the shape of the skull and hydrodynamic concerns. It seems unlikely, if not impossible, for internal structures such as the spermaceti organ, junk, museau de singe, and distal sac to be inferred; the first two have a major influence on external appearance, as demonstrated by Carrier et al. (2002). Who knows what functional morphology would be hypothesized without knowledge of the complex inner anatomy of the snout, but with knowledge of the strong asymmetry, lack of functional teeth, and a big lump of tissue that must be doing something other than fill out a basin-shaped skull. 

Thanks to cryptozoology, hypothetical alternate realities are not needed for cetacean remains to be grossly misinterpreted. I really couldn't ask for a better springboard for showing off the ludicrous contrast between the skeleton and life appearance in cetaceans.

Above is an extremely literal reconstruction of the 'hairy' Russian 'plesiosaur' carcass. The position of the nostrils is unambiguously cetaceous, but surely the head is too crocodilian and the body too serpentine for this to be a known species? Nah, the skeletal morphology is unambiguously identical to that of a Beluga whale (Delphinapterus leucas). Who knew that beneath all that blubber and muscle, Belugas were reptilian monsters?

Delphinapterus leucas skeleton from Wikipedia Commons.

Beluga, from Flickr user Travis S.

What I find particularly striking is how much of this cetacean's mass lies outside of the ribcage, and that the ribcage appears to have very little 'influence' on the overall shape of the animal.

Delphinapterus leucas head 3 - taken and modified from Wikipedia Commons.

It seems that a few suggestions of the underlying skull can be seen on the live Beluga's head, but it still seems amazing that the two have anything to do with one another.

---

In 1996, a 'dragon' skeleton was pulled out of the ocean in Langkawi, Malaysia. The only available photo is unfortunately tiny, but the shape of the skull as well as the shape and number of the teeth make an Orca (Orcinus orca) identity probable. That, and it was identified as such.

Based on this.

The situation is essentially the same as that of the Beluga, but with a scarier and vaguely crocodilian head. I think that this shows that, underneath that adorable layer of blubber and high-contrast markings, Orcas are capable of serious macropredation.

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The Ataka carcass - Worst 'Mystery' Ever.

Something like 6-7 years back in Rhode Island, a local news station ran a brief blurb on a carcass similar in condition to the Ataka specimen being unceremoniously disposed of. It was identified as a Humpback Whale (Megaptera novaeangliae) and nobody appeared to have given it a second thought. The Ataka carcass itself is similarly a complete non-mystery - it was unambiguously identified as a Bryde's Whale shortly after washing up. Even Heuvelmans' great tome, In the Wake of the Sea-Serpents, summarily lists it as such. It is then utterly baffling that some cryptozoology sites insist that this is still a valid mystery. Apparently, some people sincerely believe that this is roaming the oceans:

A thin membrane was added between the tusks so it would have some semblance of functional morphology. Baleen whales probably have the most 'alien' looking mammalian skulls around, so it is quite difficult imagining what a blind reconstruction would look like. I'll admit I just wanted to draw something which looked like a bird skull with pincers coming out of it.

This article is a runaway introduction to a somewhat more rigorous topic - giving extinct whales proper amounts of soft tissue. Yes, shrink-wrapped cetacean reconstructions have been done in all sincerity despite, as this post hopefully demonstrated, that making no sense whatsoever.

References:

Carrier, D. R., Deban, S. M., and Otterstrom, J. (2002). The face that sank the Essex: potential function of the spermaceti organ in aggression. The Journal of Experimental Biology 205, 1755-1763. Available.

Clarke, M. R. (1978). Structure and Proportions of the Spermaceti Organ in the Sperm Whale. Journal of the Marine Biological Association of the United Kingdom 58, 1-17. Available.

The Benefits Of Having Stuff Grow All Over You

One would think that epibiotic growth, that is, commensal organisms attached to a living surface, would be neutral at best and a hindrance to locomotion at worst* for the basibiont, the substrate organism. 'Fouling' by epibiotic growth is a virtually omnipresent pressure in aquatic environments, so basibionts variably avoid, defend against, or tolerate epibiotic growth (Wahl 1989). Since there are potential examples beyond count, given the tendencies of this blog I'll focus on some recently described examples of tolerance from big vertebrates.

* Potential disadvantages for the basibionts includes increase in weight, decrease in flexibility, increase in friction, damage from anchoring, damage due to grazers preying on epibionts, and so forth (Wahl 1989 - citing various).

The loricariid catfish Pterygoplichthys (possibly P. disjunctivus and hybrids) was accidentally introduced to Florida and has been observed interacting with manatees while both species were present near springs during the winter, avoiding unsuitably low temperatures (Nico et al. 2009). The interaction is that the catfish graze upon the grazers:

A mother and calf with 16 loricariids. Note that manatees are typically covered in epibiotic growth. The authors recorded another instance of over 40 catfish on one individual, almost obscuring it from view. Photograph by James P. Reid, taken from Nico et al. (2009).

The heavy covering of epibionts on manatees indicates tolerance and implies either a neutral impact or a beneficial one. Nico et al. (2009) speculate that while the epibiont layer probably does not provide notable protection against UV radiation (as manatee skin is very thick), it could play a role in heat absorption. Manatee behavior towards the armored catfish is contradictory; while some individuals ignore them (Fig. 1) even if as many as 40 catfish are involved, others apparently avoid congregations of catfish and others still are irritated by the fish and attempt to dislodge them (Nico et al. 2009). Since the interaction is so recent, perhaps it is possible that manatees have not learned or evolved a standardized response. Manatees generally ignore other fish including remora species that feed on their fecal matter and bluegills that apparently feed on epibionts (Williams et al. 2003, Powell 1984); however they are not tolerant of a porgy species which occasionally nips at them (Nico et al. 2009 - citing pers. com.). The grazing on manatees could be beneficial for the removal of parasites and removal of diseased and damaged tissue, although it also carries the risk of disease transmission (Nico et al. 2009). This is a surprisingly complicated situation and clearly the role of epibionts needs to be further investigated, as do the risks and benefits of allowing fish to graze. Nico et al. (2009) speculate that manatees that avoid loricariids may move to colder water, where they expend more energy than normal attempting to maintain body heat.

The interaction between cetaceans and their epibionts seems to be less obscure than the manatee situation. In dealing with Orcinus orca predation, mysticetes have adopted fight or flight countermeasures; the Balaenoptera species are fliers while the right whales (Eubalaena spp.), bowhead whale (Balaena mysticetus), humpback whale (Megaptera novaeangliae) and grey whale (Eschrichtius robustus) are fighters (Ford and Reeves 2008). Although the number of documented cases of orcas killing mysticetes are few, the rate of scarring suggests that predation attempts are significant, likely for juveniles (Ford and Reeves 2008). The ability to sprint at considerable speeds in the Balaenoptera species seems to be a direct evolutionary response to predation, but the fight species may have evolved to be slow and maneuverable primarily because of their ecological niches (Ford and Reeves 2008). Possibly mirroring the evolution of horns in some bovids, the offensive structures in right whales and humpback whales are used both for intraspecific male combat and interspecific defense and it is not clear for what purpose they originally evolved (Ford and Reeves 2008). Although right whales and humpback whale will swing or lunge with their heads, flippers and flukes are the primary means of defense for these species; gray whales roll on their backs to protect their vulnerable ventrum (Ford and Reeves 2008).

Right whales have hardened patches of skin known as callosities on the dorsal, lateral, and ventral surfaces of the head. These callosities host thousands of amphipods, epibionts with no obvious beneficial function for the whales - apparently the cornified epidermal tissue provides their ideal habitat and harboring the arthropod is a side effect for possessing the morphology. Southern right whales, however, possess barnacles which probably do have a function in making the callosities more formidable.

The Southern Right Whale has callosities with both amphipods and barnacles. From here. Has anyone every suggested that right whales may be responsible for sightings of 'marine saurians'?

Humpback whales lack callosities, but they have analogous barnacles which fulfill the same function - and provide an unambiguous example of a positive epibiotic interaction. Humpbacks can have up to 450 kg of large barnacles ( up to a 5 cm diameter) concentrated on the head, leading edge of their flippers, tips of the tail flukes, throat pleats, and near the genital slit (Ford and Reeves 2008 - citing Clark 1966, Slijper 1962). While intraspecific purposes are also likely, it is probably no coincidence that humpback whales defend against orcas using their head, flippers, and flukes (Ford and Reeves 2008). It seems like the throat and genital regions would be particularly susceptible to either biting or ramming attacks, further suggesting the defensive function of the barnacles.

Grey whales have often continuous encrustations of barnacles on the dorsal portions of their rostrum, anterior portion of their backs as well as their flippers, fluke, and elsewhere (Ford and Reeves citing Rice and Wolman 1971). Considering the defensive behavior of the whales, once again it appears that the barnacle placement is no coincidence. Exactly how these whales attract barnacles to particular portions of their body certainly is a good question; how do the callosities of some right whales have barnacles and others don't?

Epibiosis certainly doesn't end with heat balance (maybe) and creating weapons, Wahl (1989) notes that other potential benefits for the basibiont include a supply of vitamins and/or nitrogen compounds, water retention during low tide, camouflage, mask chemical cues, and drag reduction (!) - thanks to hydrophobic bacteria on skin. There are of course many, many potential disadvantages as well.

References:

Ford, John K. B.; Reeves, Randall R. 2008. Fight or flight: antipredator strategies of baleen whales. Mammal Rev. 38(1), 50–86.

Nico, Leo G; Loftus, William F.; Reid, James P. 2009. Interactions between non-native armored suckermouth catfish (Loricariidae: Pterygoplichthys) and native Florida manatee (Trichechus manatus latirostris) in artesian springs. Aquatic Invasions 4(3), 511-519. Available.

Powell, J. A. 1984. Observations of cleaning behavior in the bluegill (Lepomis macrochirus), a centrarchid. Copeia 1984, 996-998.

Wahl, Martin. 1989. Marine epibiosis. I. Fouling and antifouling: some basic aspects. Mar. Ecol. Prog. Ser. 58, 175-189. Available.

Williams, E. H. Jr.; Mignucci-Giannoni, A. A.; Bunkley-Williams, L.; Bonde, R. K.; Self-Sullivan, C.; Preen, A.; Cockcroft, V. G. 2003. Echeneid-sirenian associations, withinformation on sharksucker diet. Journal of Fish Biology 63(5), 1176-1183. Available.

The Sperm Whale's Jaw; or Sorry, Gerald Wood

In length, the Sperm Whale’s skeleton at Tranque measured seventy-two Feet; so that when fully invested and extended in life, he must have been ninety feet long; for in the whale, the skeleton loses about one fifth in length compared with the living body. Of this seventy two feet, his skull and jaw comprised some twenty feet, leaving some fifty feet of plain back-bone. Attached to this back-bone, for something less than a third of its length, was the mighty circular basket of ribs which once enclosed his vitals.

- Excerpt from "Measurement of The Whale's Skeleton" - Chapter 103 of Moby-Dick; or The Whale by Herman Melville

Earlier in the chapter, Melville/Ishmael tells us that a Sperm Whale of the largest magnitude measures between eighty-five and ninety feet long and by his reckoning weighs at least 90 tons, or as much as a village of 1,100. By my own reckoning in this previous post, I pegged a 19.5 meter (67'11") bull at around 90 tonnes (~100 tons) and I estimated a 27.5 m (90 foot) bull to weigh a stupefying 210 tonnes/230 tons. If the whale of Tranque was as big as Melville/Ishmael claimed*, it would have rivaled the largest blue whales (Balaenoptera musculus) for size.

* How can a 72 foot skeleton possibly correspond to a 90 foot whale? A ~20 foot mandible would be at a 1:3.6 ratio to the skeleton length, which agrees well with the 1:3.8 m estimate below. The modified Gore et al. (2007) formula (see further below) estimates the whale's length at 21.4 meters (70 feet) using a skull length of 6 meters - could this have been based off a real specimen?

Skeletons of gigantic sperm whales (Physeter macrocephalus sometimes P. catodon) do not currently exist in museums as far as I know (if they ever did) and the only possible evidence of colossal bulls rests in preserved mandibles. In my previous post I discussed a 5 meter (16'4.75") mandible in the British Museum which Wood (1982) estimated to have come from a 25.5 meter bull; I extended Wood's reasoning to estimate a 5.5 meter mandible from the Nantucket Whaling Museum to correspond with a 27.5 meter bull. Wood (1982) noted that a 14.7 m whale had a mandible:body length ratio of 1:6.2 and a 16.28 m whale had a ratio of 1:5.4; he extended the graph to estimate a 1:5.1 ratio for his monstrous mandible and I extended it further to 1:5 for the even bigger mandible. I'm now quite certain that all of these estimated lengths and ratios are, in fact, hogwash.

The book, The Marine Mammals in the Anatomical Museum of the University of Edinburgh (courteously digitized by Google) notes that a 15'10" (4.83 m) mandible probably corresponded with a sperm whale 60 feet (18.3 m) in length - let's assume that this estimate is accurate. This whale would have had a mandible:body length ratio of around 1:3.8; if we assume there is little allometric change, the 5 m mandible would thus correspond to a 19 meter bull and the 5.5 meter mandible would correspond to a 21 meter bull. Given that the record length sperm whale was 20.7 meters in length, I'd say that these seem like plausible figures. But is this accurate?

Unfortunately, there is a lack of data on sperm whale mandible length:body length. However, if we assume that the length of the mandible is nearly the same as that of the skull, this gives us more data to work with. I'll give a range of estimates just to be safe, the first will assume a 1:1 mandible:skull ratio and the second will assume that the mandible is roughly 90% of the skull's length. Data on head length should be avoided since soft tissue can make it considerably longer. Gordon (1991) used data on sperm whale spermaceti length in comparison to body length to come up with a formula which Gore et al. (2007) in turn used to estimate body length from skull length. It is as follows:

Total body length = 9.75 − 0.521 (SL) + 0.068 (SL^2) + 0.057 (SL^3)

Where SL = skull length

This is quite a bit more complicated than what I was using as it appears to take allometry into account (where I previously sorta ignored it). Here is what happens when we plug in numbers:

5 meter mandible:
5 meter skull = 15.97 meters (52 feet)
5.5 meter skull = 18.42 meters (60 feet)

Wood's 25.5 meter estimate was probably off by 138% to 160%.
Using a 1:3.8 ratio gives estimates that are off by 114% to 119%


5.5 meter mandible:
5.5 meter skull = 18.42 meters (60 feet)
6.0 meter skull = 21.384 meters (70 feet)

My 27.5 meter estimate (based off of Wood's allometry) is probably off by 128% to 149%
Using a 1:3.8 ratio gives estimates that are off by 113% and 106%

A 6 meter skull was also present in the (fictional?) Tranque whale, and Melville/Ishmael's estimate for skeletal length (72 feet) is off by 103%. The estimation for body length in the flesh is off by 129%.


Hard data is needed on the mandible:body length ratio in sperm whales so these equations can be refined. I'd say that as is, the data suggests that the 5 and 5.5 meter mandibles do not correspond with bulls greatly exceeding the known 20.7 meter record. It could be possible that these mandibles are the product of abnormal growth analagous to acromegaly in humans (as suggest by Alan Hazen). There is currently no non-anecdotal evidence of bulls greatly exceeding 20.7 meters and while specimens somewhat larger than this probably existed in the past due to a larger average length, sperm whales do not appear to rival blue whales for the title of the largest animal ever to have lived.


I was planning to make this an addendum, but it quickly got out of hand...


For information on sperm whale jaw oddities, see the post at Tetrapod Zoology


References:

Gordon, Jonathan C. D. 1991. Evaluation of a method for determining the length of sperm whale (Physeter catodon) from their vocalizations. Journal of Zoology 224, 301-314

Gore, M. A. et al. 2007. Sperm whale, Physeter macrocephalus, stranding on the Pakistani coast. J. Mar. Biol. Ass. 87, 363–364

Wood, Gerald. 1982. Guinness book of Animal Facts and Feats. Guinness Superlatives, Middlesex.

Mesoplodonts of the Southern Oceans

The huge expanse of water made up of the southern Indian, Atlantic and Pacific Oceans is home to six mesoplodonts (and 4 other ziphiids) including a Mesoplodon mirus subspecies or sister species. That species is known from strandings off South Africa, southern Brazil and southern Australia and sightings off the coast of Madagascar occuring within 33 to 38 degrees S, compared to 26.7 to 53.7 degrees N for the northern population (MacLeod et al. 2006). It should be warned that records for many of these species are uncommon and they may not entirely or accurately portray the range. It is certainly puzzling how these species coexist niche-wise and future studies will undoubtedly clarify or completely revise the information in this post.



Andrews' Beaked Whale
Mesoplodon bowdoini
Andrews, 1908

This species was regarded to be an antitropical population of M. stejnegeri by some, despite being more similar to M. carlhubbsi morphologically, and fortunately there has been a recent review (Baker 2001) that solidified the distinctiveness of this species. M. bowdoini has smaller teeth with a more forwards and upwards facing denticle than M. carlhubbsi; blunter antorbital tubercles that do not extend (anteriorly) past the maxillary prominences and are made of the maxilla, frontal, jugal and lacrimal (contra: maxilla and jugal); and prominential notches that are shallow and curved (and not deep and "v"-shaped). M. bowdoini was known as the splay-toothed whale to some due to the 20 degree splay in the type specimen, but it turns out that adult males have splays from 0 to <16 style="font-style: italic;">M. bowdoini and M. carlhubbsi to be "extremely similar" anatomically and predicts that the species will share similar stomach anatomy (Mead 2007). If stomach anatomy has some correlation to niche then there may be some differences.

Mesoplodon bowdoini is known from 35 strandings mostly from New Zealand (22) and Australia (8) but there are recent records from Tristan da Cunha, the Falkland Island and Tierra del Fuego (MacLeod et al. 2006, Baker 2001). This species may be circumpolar (all ziphiids in this area probably are) in waters roughly between 35 and 55 degrees S, but it is not known if the huge gaps in the Indian and Pacific oceans represent breaks in the range or not (MacLeod et al. 2006). This species is one of the four smallest mesoplodonts and may be in the "very small prey consumer guild" (MacLeod 2005), males (n= 7) have a median length of 4.22 m and a maximum of 4.41 m while females (n= 6) have a median length of 4.075 m and a maximum length of 4.36 m and the modes for all specimens (n= 15) were 3.9-4.0 and 4.2-4.3 (MacLeod 2005 - App. I). Does this M. bowdoini represent the same niche as M. carlhubbsi? Information is of course rather limited, but if M. carlhubbsi and M. mirus have analogous niches in different oceans (small prey consumer, deep water, moderate temp. preference) it would seem quite odd that similar species both inhabit the southern hemisphere. Unless M. mirus or a similar species are much smaller than their northern relatives, it would not make sense for the smaller of the species to inhabit higher latitudes.

Before I get too entangled, I should mention another piece of the puzzle.



Hector's Beaked Whale
Mesoplodon hectori
Gray, 1871

Not much is known about M. hectori and older sources are unreliable since the information presented mixes this species with M. perrini. Gales 2002 has an incredibly close-up photograph of M. hectori (considering how boat shy it probably is) that looks quite different from normal depictions (e.g. Reeves et al. 2002) that were based off of M. perrini. As far as I can tell this page has the only depiction of M. hectori that actually depicts the species.

One juvenile specimen (2.8 m) from New Zealand curiously had a single indentation on its throat instead of the pair of throat grooves present in all other ziphiids which are believed to aid in suction feeding (Baker 2001a). The specimen was in good physical condition and had stomach parasites which indicated that it did prey on organisms and wasn't weaned (Baker 2001a). It is theorized that this specimen was able to create suction by tongue retraction (Baker 2001) and I guess it shows that the throat grooves aren't critical in feeding, but they still should be offering a significant advantage.

M. hectori stranded from 32 to 55 degrees S (Tierra del Fuego) off South America and 35-42 degrees S off New Zealand, showing a range very similar to M. bowdoini. M. hectori is the final potential member of the "very small prey consumer" guild (MacLeod 2005) with a male median length is 3.73 m (3.7-3.8 mode, 4.34 max) and a female median length of 4 m (4.15 max) (MacLeod 2005 - App. I). While the other two possible members of the guild, M. peruvianus and M. perrini, are apparently parapatric it would seem that these species occupy separate niches. There is a chance that the stranding records give an inaccurate impression of distribution and these species are temporally separated. As discussed in the previous post, M. hectori and M. perrini do not appear to be sister species and are morphologically similar, possibly suggesting that M. hectori is also capable of out-competing M. densirostris. The latter species only appears to go down to 41 S and a smaller species out-competing it would be very unlikely. Maybe there are some fine-scale differences which allow for this to occur.

I have to admit that more information is needed to even get a basic understanding of how these species fit together niche-wise. Does similar morphology indicate similar niches or common ancestry? How accurate are the ranges? Do species occupy niches that have no northern counterparts? How is there all this confusion with three species left?


Strap-toothed whale
Mesoplodon layardii
Gray 1865

This is the first of three species which appear to be ecologically similar and overlap substantially in the southern oceans. Unexpectedly, this species seems to be fairly well studied for a mesoplodont but articles are either lacking or unaccessible for me. Fortunately I can at least get basic information from other sources.

M. layardii is the largest mesoplodont with a male median of 5.145 m (max= 5.84, n= 10) and a female median length of 5.765 m (max= 6.25 m, n=8), it is also one of two species (M. europaeus being the other one) where females appear to be consistently larger than males (MacLeod 2005 - Appendix I). M. europaeus also had many more measured specimens (72 vs. 18) so we'll have to see if this patterns continues (and to what degree) with additional information from M. layardii. What is known for certain about the strap-toothed whale is that it has enormous (30 cm) tusks that cross the upper jaw and has cutting areas reduced to small points (MacLeod 2003). It is commonly cited that this incredible tooth development limits the gape of male M. layardii to about an inch, but not so frequently mentioned is the fact that M. carlhubbsi (and apparently M. stejnegeri) has a similarly reduced gape thanks to mandible and tooth development*. It seems interesting that M. layardii, M. carlhubbsi and M. stejnegeri all tended to consume a greater number and a greater variety of cephalopods than other mesoplodonts and the prey tended to be quite small (under 500 g) (MacLeod et al. 2003). Local Ziphius and Hyperoodon can take prey five times larger than M. layardii can despite being only 10 and 20% percent longer, respectively (MacLeod et al. 2003) and I'd be curious if there are any differences between male and female M. layardii. It seems very odd that three of the four consistently largest mesoplodonts (MacLeod et al. 2005 - Appendix I, M. mirus is the fourth) would severely reduce their gape and potential prey size, the pressures for this don't seem overly clear. I was thinking about competition with large prey consumers (Indopacetus, Ziphius, Hyperoodon, Ziphius, Tasmacetus?) but a reduced gape does not seem to occur in Atlantic mesoplodonts.

* The reason for increased mandibular height/tooth development seems to be tied in with more posterior placement of the teeth and appears to be related to a fighting style that bypasses the reinforced melons (Hardy 2005). Other species with mandibular arches seem to have teeth placed in a way that won't reduce the gape much, if at all - M. bowdoini, M. densirostris, M. ginkgodens, M. peruvianus.


This species seems to range from 32 to 63 degrees S (for the most part) judging by records from strandings and sightings (MacLeod et al. 2006). Male M. layardii can of course be distinguished at sea by their strap-like tusks plus they have a bold coloration of white on black, including lighter coloration on the dorsal surface that at least one authority views as cape-like (Reeves et al. 2002). The lighter dorsal surface is reminiscent of Ziphius and the cape is reminiscent of Tasmacetus (where it seems to be better defined). As distinctive as this species is, there is an incredibly poorly known mesoplodont that may be confused for it.



Spade-toothed Whale
Mesoplodon traversii
Gray, 1874

This species is only known from a damaged mandible and teeth from Pitt Island New Zealand in 1872 (synonymized with M. layardii), a calvaria from White Island New Zealand from the 1950's (classified as M. ginkgodens) and a calvaria from Chile in 1986 (type specimen for M. bahamondi); these specimens have been assigned to M. traversii on the basis of molecular phylogenetics and morphology (van Helden et al. 2002). This gives the species a range of 33 to 44 degrees S although future investigation is needed to determine if any prior M. layardii records actually represent M. traversii (MacLeod et al. 2006)

Mesoplodon traversii of course lacks strap teeth, theirs look somewhat reminiscent of a whaler's flense (compare to the teeth). These teeth are very large (233 and 238 mm for right and left, respectively), are angled posteriorly at 140 degrees, have a large apically placed denticle that faces outwards, the teeth are sinusoidal in the sagittal place and offset the root by 20 degrees (van Helden et al. 2002). An anterior view of the mandible makes it look like the teeth could reduce the gape and van Helden et al. 2002 documented severe erosion just above the gum-lines on the anterior ends of the teeth, a trait shared with M. stejnegeri (and others) where the teeth impinge upon the rostrum. Somebody (probably Reyes et al. 1995 - which I can't access) estimated "M. bahamondi" at 5-5.0 m (according to this page and this page); if M. traversii occupies the same niche as M. layardii but at a higher latitude, a somewhat smaller body size would be likely. In cases of very low specimen counts (like fossils) it seems at least reasonable to assume that the specimen on hand represents the average size and range, but we'll have to see about that.

In the previous post I had mentioned Pitman's long-beaked "Mesoplodon sp. B" sightings which were tenuously attached to "M. bahamondi" because the wide rostrum base of the Chilean calvaria was taken as possible evidence for a long beak (Pitman and Lynn 2001). A year after that was written, we can now see that the jaw of M. traversii is proportionally similar in length to that of M. layardii and nowhere near as long as that of M. grayi, a long-beaked species "M. sp. B" was confused for by some. The external appearance of M. traversii is currently unknown, but I suppose it could be possible for it to strongly resemble M. layardii in external coloration.


Gray's Beaked Whale
Mesoplodon grayi
van Haast, 1876

This appears to be the widest ranging of the southern mesoplodonts, M. grayi has been seen summering off the coasts of Antarctica and for the most part appears to be circumpolar in waters below 30 degrees S (MacLeod et al. 2006). A stranding off Peru (at 13.8 S) may indicate that this species extends its range north in the cold Humboldt current, but another stranding in the Netherlands is probably a stray (MacLeod et al. 2006). Mesoplodon grayi is a moderately sized mesoplodont with a male median length of 4.5 m (n= 8) and a female median length of 4.67 m (n= 5) - I'd be curious about the reported length of "M. sp. B" which was reported from waters near the equator, if it occupies the same niche then we would expect it to be somewhat smaller.

Curiously, stomachs of M. grayi individuals have been found to contain only fish, which digest much faster than cephalopods (MacLeod et al. 2003). M. grayi is a long beaked species which often retains small maxillary teeth embedded in the gum, although I'm not sure if they're functional. Two other species which reportedly have fish as a major part of their diet, M. bidens and M. mirus (MacLeod et al. 2003); the former species also has a long beak, M. mirus on the other hand has a plesiomorphic dentition with simple apical teeth. Perhaps the presence of a long beak is best suited for a piscivorous diet while one with teeth impinging on the rostrum is better suited for teuthophagy. The theory of mesoplodonts selecting prey items on factors besides size still needs a lot of testing, but perhaps it could clarify how there are so many species in the southern oceans.




This ends an experiment in blogging. At the beginning of the summer I set out with the intention of seeing how deep I could get into a group. As extensive as these posts became, they're still only a moderately detailed look into ziphiids. I had dramatically underestimated how much reading I had to do, oh, and plus my writing process is painfully slow. Even though the odds are that I'll never even get to see a ziphiid, I'm still glad I did this. As interesting as a group is, there is a time to move on, at least for now.



References:

Baker, Alan N. 2001. Status, relationships, and distribution of Mesoplodon bowdoini Andrews 1908 (Cetacean: Ziphiidae). Marine Mammal Science 17 (3) pp. 473-493

Baker, Alan N. 2001a. A Juvenile Hector's Beaked Whale Mesoplodon hectori (Gray, 1871), without functional throat grooves, plus notes on parasites (Cetacea: Ziphiidae) Marine Mammal Science 17 (1) pp. 171-175

Gales, N. J. 2002.Genetic identification and biological observations of two free-swimming beaked whales: Hector's beaked whale (Mesoplodon hectori, Gray 1871), and Gray's Beaked whale (Mesoplodon grayi, von Haast, 1876). Marine Mammal Science 18 (2) pp. 551-557.

Hardy, Mathew T. 2005. Extent, Development and Function of Sexual Dimorphisms in the Skulls of the Bottlenose Whales (Hyperoodon spp.) and Cuvier’s Beaked Whale (Ziphius cavirostris). Available

MacLeod, Colin D. et al. 2006. Known and inferred distributions of beaked whale species (Cetacea: Ziphiidae). J. Cetacean Res. Manage. 7(3):271–286

MacLeod, Colin D. et al. 2003. Review of data on diets of beaked whales: evidence of niche separation and geographic segregation. J. Mar. Biol. Ass. U.K. , 83, pp. 651-665

MacLeod, Colin D. 2003. Species recognition as a possible function for variation in position and shape of the sexually dimorphic tusks of mesoplodon whales. Evolution, 54(6), pp. 2171–2173

Mead, James G. 2007. Stomach Anatomy and Use in Defining Systemic Relationships of the Cetacean Family Ziphiidae (Beaked Whales). The Anatomical Record 290:581–595

Pitman, Robert L. and Lynn, Morgan S. 2001. Biological observation of an unidentified mesoplodont whale in the Eastern tropical Pacific and probable identity of Mesoplodon peruvianus. Marine Mammal Science. 17(3), pp. 648-657

Reeves, Randall R. et al. 2002. National Audubon Society Guide to Marine Mammals, Alfred A. Knopf, New York.

van Helden, Anton L. et al. 2002. Resurrection of Mesoplodon traversii (Gray, 1874), Senior synonym of M. bahamondi Reyes, van Waerebeek, Cardenas and Yanez, 1995 (Cetacea: Ziphiidae). Marine Mammal Science 18 (3), pp. 609-621