Physeteridae

Reconstruction of Aulophyseter morricei, copyright Nobu Tamura.

Belongs within: Physeteroidea.

More than just Moby
Published 17 August 2010

The photo above (from here) shows the lower jaw of Kogia breviceps, the pygmy sperm whale. Kogia is distinguished from other toothed whales by its relatively small number of noticeably slender teeth; K. breviceps is usually distinguishable from the other species in the genus, the dwarf sperm whale K. sima, by having 12–16 pairs of teeth in the lower jaw (K. sima usually has 8–11).

Dwarf sperm whale, Kogia sima. The two Kogia species are externally very similar; indeed, Watson (1981) noted that their status as separate species had not yet gained universal acceptance. Photo by Robert Pitman.

The family Physeteridae as used in this post includes just three living species, the great sperm whale Physeter macrocephalus* and the two Kogia species (alternatively, many authors refer to this groups as the superfamily Physeteroidea, separating the living genera and their respective stem groups between families Physeteridae and Kogiidae). Though superficially distinct in appearance, the two genera share a number of unusual characteristics including enamel-less teeth (that are restricted to the lower jaw) and an externally squared head with anteriorly placed blowhole. The distinctive profile is due to the spermaceti organ, a pair of gigantic oil-filled sacs that fill the inside of the head. The upper sac, the spermaceti, contains a less dense oil than the lower sac, the junk. Just exactly what the spermaceti organ does is still uncertain; proposed uses (which are not all mutually exclusive) include vocalisation, echolocation, use as a battering ram (Carrier et al. 2002) and for buoyancy control (with the whale controlling the temperature of the organ by controlling the bloodflow to it and hence controlling the specific gravity of the contained oil) (Clarke 1978). All living species feed primarily on squid though the Kogia species eat more fish than does P. macrocephalus**.

*The scientific name of the sperm whale is renowned for being one of the most prolonged, contentious and utterly pointless conflicts in zoological nomenclature. The needless complexity of this argument is such that I’m going to farm it out to a separate post rather than try to stuff it into this one.

**I’ve come across a number of references to the sperm whale as the largest ever carnivore. This isn’t actually true. Even if one excludes the blue whale Balaenoptera musculus as a ‘carnivore’ due to its diet of planktic crustaceans (still technically animals), P. macrocephalus is just edged out of the top spot by the fin whale Balaenoptera physalus which, in at least some parts of its range, feeds primarily on fish (Watson, 1981).

The great sperm whale, Physeter macrocephalus. Source of image uncertain: I got it via Google Images from here, but the actual link appears to be broken.

However, as is not uncommon in the world of biology, the most familiar members of this family are far from being the most typical. The fossil record of Physeteridae sensu lato extends back to the Oligocene; for most of that time, fossil sperm whales had teeth far more intimidating than those possessed by any living species, indicating diets potentially more rapacious*. Just this year, of course, we saw the publication of ‘Livyatan’, the largest of these killer sperm whales, with a skull some 3 m in length (Lambert et al. 2010; unfortunately, the original name bestowed on this animal, Leviathan, has turned out to be preoccupied, admittedly under pretty goofy circumstances). Bianucci & Landini (2006) suggested that the raptorial sperm whales may have been edged out by the evolution of large predatory delphinids (the lineage including the modern killer whale Orcinus orca) during the Pliocene, leaving only the squid-eaters behind.

*Interestingly, while both genera of living sperm whales lack teeth in their upper jaws, the loss of upper teeth seems to have happened independently; the stem lineages for both genera include taxa with teeth in both upper and lower jaws (Lambert et al. 2010).

Rather than the usual reconstruction of ‘Leviathan’ melvillei, I thought I’d show you this one by Hodari Nundu. The shark is supposed to be a juvenile.
The sad, sad story of Physeter
Published 18 August 2010
Original drawing of the sperm whale stranded near Berkhey, the Netherlands, in 1598. Reproduction from Husson & Holthuis (1974).

In the section above, I alluded to the long and reprehensible debate over the name of the great sperm whale Physeter macrocephalus. Reprehensible because for at least the last hundred years there has been absolutely no disagreement over the nature of the animal concerned; the conflict has purely been concerned with what to call it.

When Linnaeus discussed the genus Physeter in the 1758 Systema Naturae, he referred to four species: P. macrocephalus, P. catodon, P. tursio and P. microps. Most authors now treat these names as synonyms of the great sperm whale*. Normally, when two or more names are available for the one species, the oldest name automatically becomes the correct one. However, because Linnaeus’ 1758 publication is the official starting point for zoological nomenclature, none of these names count as the oldest. In such a case, the general rule is that the first person to treat the names as synonymous and pick one of them to be the correct name establishes which has priority (the principle of the First Reviser).

*Physeter tursio and P. microps were both described as having high dorsal fins, something the great sperm whale completely lacks, leading to considerable confusion over the identity of the animals concerned. Modern authors tend to assume they were based on distorted or mistaken accounts of ordinary sperm whales; this is not really a satisfactory explanation, but the true identity will probably never be establishable (killer or pilot whales seem not entirely unlikely to me), and there would be little to be gained from trying.

During the 19th Century, most authors knew the great sperm whale as Physeter macrocephalus while the name P. catodon was less often referred to (and sometimes thought to refer to something like the beluga or pilot whale). It wasn’t until the beginning of the 20th Century that Oldfield Thomas (1911) asserted the synonymy of the species and selected P. catodon as the correct name. However, in 1938 Hilbrand Boschma noted that Murray had treated the names as synonymous in 1866 and selected P. macrocephalus, pre-dating Thomas’ selection. This was countered in 1966 by Philip Hershkovitz who claimed that Murray’s selection was invalid.

The most detailed discussion of the matter was by Husson & Holthuis (1974) who discussed each of the records cited by Linnaeus for the names Physeter catodon and P. macrocephalus, selecting a lectotype for the former and a neotype for the latter that confirmed both as sperm whales. They also established that Blasius had treated the names as synonyms in 1857 and selected P. macrocephalus as the valid name, meaning that P. macrocephalus had priority even if Murray was disqualified as an authority.

However, the validity of Physeter catodon was again championed by Schevill (1986) on the basis that P. macrocephalus was supposedly invalid from the get-go. Linnaeus had distinguished the two species on the basis that P. macrocephalus supposedly had its blowhole on its neck while P. catodon had it at the front of the head; the correct position in the sperm whale is, of course, the latter. Schevill claimed that Husson & Holthuis’ examination of the earlier records to correct Linnaeus’ description was invalid as the concept of type specimens did not exist in Linnaeus’ time, making the printed description the only judge of the species identity. Because the description of P. macrocephalus did not agree with a real sperm whale, it could not be used as the valid name.

As pointed out by Holthuis (1987), Schevill’s latter argument was simply wrong. If the original author did not explicitly nominate a type specimen for a new species, then all specimens considered in the original description automatically become the type series*. To claim that the concept of types is inapplicable to Linnaeus is to ignore a fundamental aspect of the nature of the Systema Naturae, which did not spring ex nihilo but was in many places an index to the work of earlier naturalists, tying their descriptions into Linnaeus’ new nomenclatural system. In the case of the sperm whale, Linnaeus was mislead by the faulty descriptions provided by others (Linnaeus himself had never seen a sperm whale). Examination of these earlier records allows the error to be recognised. Husson & Holthuis (1974) chose as lectotype of P. macrocephalus a specimen stranded in the Netherlands in 1598; while the specimen has not been preserved anywhere, illustrations of it leave no doubt that it was a sperm whale.

*Though it is true that the type specimen did not exist as a formal concept in 1758, it was not long afterwards that naturalists were finding it useful to examine earlier authors’ specimens to determine their intention. Exactly when the type concept became formalised, I’m not sure.

So, in summary, both P. catodon and P. macrocephalus are available names for the great sperm whale; Blasius as First Reviser established the priority of the latter in 1857. The correct name for the great sperm whale is therefore Physeter macrocephalus.

Systematics of Physeteridae
Physeteridae [Catodontidae, Physodontidae]
|--PhyseterulaLB10
`--+--AulophyseterLB10
| |--A. morricei Kellogg 1927BDR85
| `--A. rionegrensis Gondar 1975BDR85
`--Physeter Linnaeus 1758LB10, W81 [Physeterinae]
`--P. macrocephalus Linnaeus 1758H87 (see below for synonymy)

Physeteridae incertae sedis:
Ferecetotherium Mchelidze 1970GS03, WS76
`--F. kelloggi Mchedlidze 1970SB02
Physetodon baileyi McCoy 1879LA02
Scaldicetus Du Bus 1867SM93
|--S. lodgei Chapman 1917LA02
|--S. macgeei Chapman 1912LA02
`--S. mortsenlensisL05
Scaptodon lodderi Chapman 1918LA02
Kogiopsis floridana Kellogg 1929BDR85
Idiophyseter merriami Kellogg 1925B76
Paleophoca nystiiR76
Miokogia Pilleri 1986SM93
Diaphorocetus Ameghino 1894SM93
HoplocetinaeBDR85

Inorganic: Physeter catodon protomiliorientalus Okamura 1987O87

Physeter macrocephalus Linnaeus 1758H87 [incl. P. catodon Linnaeus 1758H87, P. microps Linnaeus 1758W81, P. tursio Linnaeus 1758W81]

*Type species of generic name indicated

References

[B76] Barnes, L. G. 1976. Outline of eastern North Pacific fossil cetacean assemblages. Systematic Zoology 25 (4): 321–343.

[BDR85] Barnes, L. G., D. P. Domning & C. E. Ray. 1985. Status of studies on fossil marine mammals. Marine Mammal Science 1 (1): 15–53.

Bianucci, G., & W. Landini. 2006. Killer sperm whale: a new basal physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy. Zoological Journal of the Linnean Society 148 (1): 103–131.

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

Clarke, M. R. 1978. Buoyancy control as a function of the spermaceti organ in the sperm whale. Journal of the Marine Biological Association of the United Kingdom 58: 27–71.

[GS03] Geisler, J. H., & A. E. Sanders. 2003. Morphological evidence for the phylogeny of Cetacea. Journal of Mammalian Evolution 10 (1–2): 23–129.

[H87] Holthuis, L. B. 1987. The scientific name of the sperm whale. Marine Mammal Science 3 (1): 87–88.

Husson, A. M., & L. B. Holthuis. 1974. Physeter macrocephalus Linnaeus, 1758, the valid name for the sperm whale. Zoologische Mededelingen 48 (19): 205–217, pls 1–3.

[L05] Lambert, O. 2005. Phylogenetic affinities of the long-snouted dolphin Eurhinodelphis (Cetacea, Odontoceti) from the Miocene of Antwerp, Belgium. Palaeontology 48 (3): 653–679.

[LB10] Lambert, O., G. Bianucci, K. Post, C. de Muizon, R. Salas-Gismondi, M. Urbina & J. Reumer. 2010. The giant bite of a new raptorial sperm whale from the Miocene of Peru. Nature 466: 105–108.

[LA02] Long, J., M. Archer, T. Flannery & S. Hand. 2002. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. University of New South Wales Press: Sydney.

[O87] Okamura, C. 1987. New facts: Homo and all Vertebrata were born simultaneously in the former Paleozoic in Japan. Original Report of the Okamura Fossil Laboratory 15: 347–573.

[R76] Ray, C. E. 1976. Geography of phocid evolution. Systematic Zoology 25 (4): 391–406.

Schevill, W. E. 1986. The International Code of Zoological Nomenclature and a paradigm: the name Physeter catodon Linnaeus 1758. Marine Mammal Science 2 (2): 153–157.

[SM93] Stucky, R. K., & M. C. McKenna. 1993. Mammalia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 739–771. Chapman & Hall: London.

[W81] Watson, L. 1981. Sea Guide to Whales of the World. Hutchinson: London.

[WS76] Whitmore, F. C., Jr & A. E. Sanders. 1976. Review of the Oligocene Cetacea. Systematic Zoology 25 (4): 304–320.

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