Ancient Sperm Whales were no squid eaters but killers

[Sordes]

This is no thread which is really ceph-related, but as sperm whales are among the most important predators of many larger squids-species, this has at least a little relation to prehistoric squid ecology (and could be interesting for other reasons too). The modern sperm whales are among the most spectacular and highest evolved mammalian predators which ever existed, but despite their huge size they feed mainly from comparably small and petite prey and they show no aggressions towards other marine mammls, which is probably a result of their high grade of specialization on squid (and also fish).
In contrast to this gentle giants, some of their distantly related forefathers had a much more aggressive lifestyle. I knew already of some early spermwhales, but only a short time ago I discovered that this animals were probably very fierce hunters in the prehistoric seas, and acted very similar to modern orcas, which did still not existed at this time. Here are some descriptions about them:

Killer sperm whale: a new basal physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy


GIOVANNI BIANUCCI* and WALTER LANDINI




Zygophyseter varolai, a new genus and species of Physeteroidea (Cetacea, Odontoceti), is based on an almost complete skeleton from the Late Miocene (Tortonian) in southern Italy. The extreme elongation of the zygomatic process of the squamosal and the circular supracranial basin (probably for housing the spermaceti organ) delimited by a peculiar anterior projection of the supraorbital process of the right maxilla are the most distinctive features of this bizarre sperm whale. Large body size, large teeth present in both lower and upper jaw, and anteroposteriorly elongated temporal fossa and zygomatic process of the squamosal indicate that this cetacean (for which we suggest the English common name killer sperm whale) was an active predator adapted to feeding on large prey, similarly to the extant killer whale (Orcinus orca). A phylogenetic analysis reveals that Zygophyseter belongs to a Middle?Late Miocene clade of basal physeteroids, together with Naganocetus (new genus for the type of 'Scaldicetus' shigensis). Moreover, the phylogenetic analysis shows evidence of a wide physeteroid radiation during the Miocene and that the extant Physeter and Kogia belong to two distinct families that form a clade representing the crown-group Physeteroidea. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 148, 103?131.

Middle/late Miocene hoplocetine sperm whale remains (Odontoceti: Physeteridae) of North Germany with an emended classification of the Hoplocetinae


Oliver Hampe


Museum für Naturkunde der Humboldt-Universität zu Berlin, Invalidenstraße 43, D-10115 Berlin


Abstract


Hoplocetus ritzi n. sp. is a new hoplocetine physeterid from the Bolboforma fragori /subfragoris Zone of the middle/late Miocene mica-clay of Groß Pampau in Schleswig-Holstein, North Germany. The Hoplocetinae are known from the early Miocene to the Pliocene. Comparative studies of cranial characters and tooth morphology allow an emended diagnosis of the Hoplocetinae Cabrera, 1926. Four genera, Diaphorocetus, Idiorophus, Scaldicetus, and Hoplocetus are included in this subfamily. The pattern of functional tooth wear deduced from the described Hoplocetus ritzi n. sp. remains is reminescent of that known from Orcinus orca. The hoplocetine physeterids possibly occupied the killer whale niche before the killer whales appeared during the middle Pliocene.

Picture of the killer-sperm-whale Aulophyseter:
http://www.gem.hi-ho.ne.jp/aquaheart/aulophyseter.gif

On the last page of this pdf-article is a photo of a skeleton of such a killer sperm whale: http://collections.nhm.org/newsletters/pdfs/2006-01.pdf

Note the comparably short and very robust mandibula and maxilla with the large palatinal teeth. The snout is also very stout and completely different from those of modern sperm or pygmy sperm whales. The skull resembles much more those of the recent orca: http://www.amonline.net.au/mammals/images/marine/400/killer_whale.jpg
In contrast the highly elongated and very thin "tweezer"jaws of recent sperm whales with lacking palatinal teeth: http://www.museum.vic.gov.au/bioinformatics/mammals/images/macroside1.jpg

It would be very interesting to know what effects the evolution of sperm whales had on the evolution of squids (and I suppose it had a strong impact) and if there were already other large squid-eaters before the development of squid-eating sperm whales.

 

[cuttlegirl]

Thanks for the article.

The diet of modern orcas consists of marine mammals, fish and squid. Depending on the location of the orca, 6-20% of its diet consists of squid. The rest of its diet is vertebrates. It seems like an animal would need strong crushing jaws and teeth to consume other marine mammals, not so much to eat squid, which could probably slide down their throats whole (if the squid was small...).

What hard animal do you think this killer sperm whale was eating? Ammonites were extinct, that leaves other vertebrates and sharks...

 

[monty]

speaking of cetaceans, apparently they have "spindle" neurons in their brains:
http://today.reuters.com/news/artic...LES-BRAINS.xml&WTmodLoc=Home-C5-scienceNews-2

I'm dubious about something that specialized evolving independently, I think the claim in the paper about that is more likely to be explained by them, or at least the mechanism for making them, having evolved much earlier than the primate-centric researchers thought, and it's just been lost or not expressed in the "not so great apes."

 

[Sordes]

There are several populations of orcas, from which some eat nearly only fish like salmons or herring, but others consume mainly marine mammals (even the attack of a school of sperm whales by a large pod of orcas was documented a short time ago), but also birds and sometimes turtles.
Teeth seems not to be necessary for squid eaters- young and females sperm whales have none, and in beaked whales which eat mainly squid too, the number of teeth is also strongly reduced in most cases, they suck the slippery squid like a vacuum cleaner.
I don´t know how large the ancient killer sperm whales were, but I suppose they were smaller than modern sperm whales and more in the range of orcas. But what did they eat? I think nearly anything they wanted, the only exeptions were probably giant sharks like Megalodon, but a whole pod of this whales was probably also able to kill such a giant shark (modern orcas have no problems to kill great whites...). There were already many small and medium-sized whales, on some places sirens, marine crocodiles and a lot of fish- I think this guys had enough to eat.

 

[Phil]

What a fascinating discovery and thanks for telling us about it Sordes.

It would be very interesting to know what effects the evolution of sperm whales had on the evolution of squids (and I suppose it had a strong impact) and if there were already other large squid-eaters before the development of squid-eating sperm whales.

That is a most fascinating question indeed. I really don't think that anyone could answer that question satisfactorarily as fossil squid are utterly enigmatic apart from deposits in one or two locations, so how the animal evolved over time and diversified is really just educated guesswork. Come to think of it, I can't remember seeing any papers on Eocene or Miocene squid anywhere during my occasional searches on the net for this site. I can't imagine that deep diving mammals would have affected squid that much; afterall squid would have teemed in their tens of millions and the occasional whale picking off a few would have little impact on their overall populations.

I am probably talking utter cobblers here but I had a pet theory that predation pressures from marine reptiles in the Jurassic and Cretaceous slowly forced some squid into deeper waters where they thrived largely untouched (excepting sharks) until the arrival of the deep diving mammals such as the whale you've mentioned above. I think that most plesiosaur fossils are from shallow water deposits, but then that is hardly surprising as deep water deposits are very rare, as far as I know. Fossil squid are enough rare beasties from shallow waters but when and where they began to live in the abyss is something that we'll probably never know for certain as they simply would not fossilize.

Certainly the barracuda like fish Cimolichthys from the Niobrara chalk preyed on giant squid as one example was found choked on a large Tusoteuthis that it had siezed from behind; the poor fish had eyes bigger than its stomach and suffered from terminal indigestion as a result.

 

[Sordes]

Some of the ichthyosaurs were undoubtly high-specialized squid-eaters, and the in some cases huge eyes (some ichthyosaurs had even larger eyes than Mesonychoteuthis), and it seems very probable that they could dive very deep. Interestingly some very large (about the size of fin-whales or even larger) ichthyosaurs had toothless jaws and an enlarged hyoids, similar to several beaked whales, which eat also mainly squid. Mosasaurs feed on ammonites, but their anatomy shows no signs of deep-diving abilities.
But I have no ideas if there were any big specialized squid-eaters in the last 65 Mio years, before squid-eating sperm-and beaked whales evolved.

 

[Sordes]

Here is a photo of a skeleton of Scaldicetus shigensis, one of this killer-sperm-whales.