Thursday, June 5, 2008

Ziphiidae: An Introduction

Finally: It was stated at the outset, that this system would not be here, and at once, perfected. You cannot but plainly see that I have kept my word. But I now leave my cetological System standing thus unfinished, even as the great Cathedral of Cologne was left, with the cranes still standing upon the top of the uncompleted tower. For small erections may be finished by their first architects; grand ones, true ones, ever leave the copestone to posterity. God keep me from ever completing anything. This whole book is but a draught—nay, but the draught of a draught. Oh, Time, Strength, Cash, and Patience!

- Herman Melville, Moby-Dick (or The Whale). Chapter 32: Cetology

Understanding of family Ziphiidae is still very much an emerging picture. At the time of Moby-Dick's publication in 1851 there were five documented species of beaked and bottlenose whale, now there are 6 genera with 21 species (around a quarter of all cetacean species) and possibly more. Melville's narrator Ishmael seemed aware of bottlenose and beaked whales in name only* and today Ziphiidae is the most poorly known of the cetacean families. They seem far from being marginalized weirdos or relics but are prominent apex predators in the Antarctic (Kasamatsu & Joyce 1995) and quite likely elsewhere. Species in the family tend to be difficult to observe: their blow is poorly visible, they have a low profile on the surface and behaviorally they are shy and spend a great deal of time diving (Watson et al. 2008). Some species have been observed rarely and others have yet to receive a confirmed sighting (Reeves et al. 2002). Curiously, some ziphiids known through observations (and not particularly rare ones either) have only been recently attached to physically described species. Fossil species are also fairly numerous and are in true ziphiid fashion regarded as being poorly known (Bianucci et al. 2007).

*He confusingly classified beaked whales as "whalebone whales". Bottlenose whales were likely Hyperoodon ampullatus. Wikipedia has an abnormally extensive article on Melville's strange chapter.

Reeves et al. 2002 (a field guide) notes that ziphiids can be distinguished from other cetaceans by the presence of grooves on the underside of their throats, "flipper pockets", flukes without a median notch and their diverse tooth/tusk morphology. Lambert et al. 2005, dealing with fossil species, states that the apomorphies of the clade include such features as an elevated vertex, wide transverse premaxillary crests, strong development of the hamular lobe of the pterygoid sinus and so forth. I will readily admit that I do not know how these characters feature into the functional anatomy of this suction feeder. Even more unfortunately, a paper discussing the mechanics of suction feeding in ziphiids (Heyning & Mead 1996) is unavailable to me; suction feeding seems to be facultative in many odontocetes with a small gape, short snout and blunt head generating the greatest pressures (Werth 2006). Ziphiids only have the first feature (outrageously so in the strap-toothed whale Mesoplodon layardii) and I'm guessing the retention of the beak offers some advantage at the expense of power.

Modified from Fig. 4 of Rommel et al. 2006. In lateral view, the delphinid Tursiops is on the left, the Ziphiid Ziphius is on the right (not to scale). Red = Premaxilla, Yellow = Maxilla, Purple = Nasal, Dark Blue = Frontal, Light Blue = Pterygoid, Turquoise = Palatine, Gray = Jugal, Orange = Squama, Pink = Exo. Rommel et al. note the more massive pterygoid, prominent nasal bones extended from the skull apex and lack of maxillary teeth in Ziphius as particularly notable.

Ziphiids appear to be generalized predators of desmeral and benthic fish and squid on the continental slope (200-2000 m down) with body size apparently determining niche, at least for the proposed mesoplodont and Ziphius/Hyperoodon niches (MacLeod et al. 2003). Exactly how the other genera fit in niche-wise is an open question and I for one am curious how so many species of mesoplodont are capable of co-existing (I'm guessing habitat use). The stomach anatomy of ziphiids is surprisingly variable, particularly in the mesoplodonts examined, but patterns between diet and stomach anatomy are not apparent - oh, and there's the problem of functional conclusions on stomach anatomy in animals like cows and sheep not being drawn yet (Mead 2007).

The IUCN Red List regards the whole of Ziphiidae as "insufficiently known" as far as conservation concerns, but there known threats. Some species are killed (only Berardius bairdii is hunted) and fatal entanglement in fishing gear may be substantial for some species (Reeves et al. 2002). Ziphiids are have longer and deeper average dives than any other air-breather recorded, and it appears that Naval sonar testing causes abnormal diving behavior (repeated shallow dives) which may lead to embolisms and strandings (Tyack et al. 2006). The 9th and 10th specimens of Indopacetus beached after sonar tests in 2005 (Watson et al. 2008) illustrating yet another way of killing animals we hardly understand anything about.

This only marks the beginning for the ziphiids; while they have been frequent subjects of this blog, more complete coverage should be appearing in the upcoming weeks. I can't pretend the posts will be some grand cathedral-like undertaking (yeesh), but hopefully they can at least lay out the basic foundations for a group which we are still beginning to understand.


Bianucci, Giovanni et al. 2007. A high diversity in fossil beaked whales (Mammalia, Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. A high diversity in fossil beaked whales (Mammalia, Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. Geodiversitas 29 (4) : 561-618.

Kasamatsu, J. & Joyce, G.G., 1995. Current status of odontocete in the Antarctic. Antarctic Science, 7, 365-379.

Lambert, Oliver and Louwye, Stephen. 2006. Archaeoziphius microglenoideus, a new primitive beaked whale (Mammalia, Cetacea, Odontoceti) from the middle Miocene of Belgium. Journal of Vertebrate Paleontology 26(1):182–191

MacLeod, C. 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, 651-665

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

Tyack, Peter L. et al. 2006. Extreme diving of beaked whales. The Journal of Experimental Biology 209, 4238-4253.

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

Rommel, S. A. et al. 2006. Elements of beaked whale anatomy and diving physiology and
some hypothetical causes of sonar-related stranding. J. Cetacean Res. Manage. 7(3):189–209

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): 609-621

Watson, Alastair et al. 2008. Distinctive osteology of distal flipper bones of tropical bottlenose
whales, Indopacetus pacificus, from Taiwan: Mother and calf, calf with polydactyly. Marine Mammal Science 24 (2): 398-410

Werth, Alexander J. 2006. Odontocete Suction Feeding: Experimental Analysis of Water Flow and Head Shape. Journal of Morphology 267:1415–1428

Things That I Couldn't Quite Fit In:

Already having outlined a lot of my upcoming posts (I intended it to be one mega-post...that didn't quite work out) some information got orphaned. Here are their stories:

In Lambert 2005, Squaloziphius forms a clade with the beaked whales but lacks certain key traits (vertex height, trans. premaxillary crests width and hamular process development similar to some eurhinodelphinids). It appears that Squaloziphius is the only non-Ziphiid member of the superfamily Ziphoidea* although this is not explicitly stated anywhere.

* For some reason Fuller and Godfrey put it in Physeteroidea, i.e. a clade with sperm whales. Likewise, the Paleobiology Database puts it in the slightly more inclusive Physeterida (and Ziphoidea). Molecular phylogenetics suggests that such groupings would by paraphyletic.

Lambert, Olivier. 2005. Systematics and phylogeny of the fossil beaked whales Ziphirostrum du Bus, 1868 and Choneziphius Duvernoy, 1851 (Mammalia, Cetacea, Odontoceti), from the Neogene of Antwerp (North of Belgium)

Fuller, Anna J. and Godfrey, Stephen J. 2007. A Late Miocene Ziphiid (Messapicetus sp.: Odontoceti: Cetacea) from the St. Mary's formation of Calvert Cliffs, Maryland. Journal of Vertebrate Paleontology 27(2):535–540

It has been recently suggested that ziphiids have a unusual "gular pathway" for sound reception. The authors suggest this may further help us understand why Naval tests are so detrimental - but at the same time suggest a healthy dose of skepticism.

Cranford, Ted W. et al. 2008. Acoustic pathways revealed: simulated sound transmission and reception in Cuvier’s beaked whale (Ziphius cavirostris). Bioinsp. Biomim. 3

1 comment:

Christopher Taylor said...

For some reason Fuller and Godfrey put it in Physeteroidea, i.e. a clade with sperm whales.

Some authors do include Ziphiidae in Physeteroidea, so inclusion of a taxon in the latter does not necessarily preclude its association with the former (you'd have to check what system the authors of that specific paper use). I believe that e.g. Geisler & Sanders (2003) found a monophyletic Physeteridae + Ziphiidae clade in their morphological analysis.

Geisler, J. H., & A. E. Sanders. 2003. Morphological evidence for the phylogeny of Cetacea. Journal of Mammalian Evolution 10 (1-2): 23-129.