Well, here we are at the end of seriously frickin' weird cetacean skull week. I hope you've all enjoyed it. We're going to finish with a bang by looking at a few - yes, not one, but a few - of the real way-out-there oddballs among the odontocetes. We start with a famous freak individual...
If you've ever read anything about sperm whales Physeter macrocephalus you'll have read the assertion that broken and deformed lower jaws have often been reported in members of this species. It's nice to know this, but why are these broken and deformed lower jaws never figured? Here is perhaps the ultimate example: this is the lower jaw of a mature male, about 12 m long, harpooned in Antarctic waters in January 1959. The dentaries curve to the right, then form a spiral, and note that the teeth on the outside of the spiral have been worn down to stumps, or lost (Spaul 1964). This is not the only sperm whale individual in which a coiled lower jaw was reported, and there are also quite a few additional records of sperm whales with strongly bent, hooked or crooked lower jaws. These deformities have been hypothesised to have arisen in diverse ways: as heritable malformations, as the consequences of disease or malnutrition, or as pathologies that resulted from combat. The important thing is that the individuals that possessed these jaws were generally described as healthy and otherwise normal (such was the case for the individual shown here). This strongly indicates that, however sperm whales obtain food, they don't need nice neat 'normal' lower jaws to do it. Exactly how sperm whales do obtain their food has been the topic of great debate, and it's such an interesting area that I'm not about to begin to cover it now (sorry, I would if I had the time).
Walrus whales
Moving on... if you've been paying attention you will have seen the bizarre walrus whales Odobenocetops mentioned here recently. It would be wrong not to look at least briefly at these incredible animals. O. peruvianus was described by Muizon (1993) from the early Pliocene part of the Pisco Formation and proved amazing in its combination of bizarre, decidedly un-cetacean combination of characters. Lacking both a rostrum and (almost certainly) a melon, its short skull had a strongly vaulted palate, dorsally facing orbits, anteriorly positioned nares, and posteroventrally projecting maxillary processes that housed tusks. The left tusk was much shorter than the right tusk (c. 25 cm vs over 55 cm). In a second skull discovered later on (Muizon et al. 1999), both tusks were short (c. 25 cm), suggesting that only males possessed the long right tusk. Sharing several derived characters with the monodontids (narwhals and belugas) and regarded as the sister-taxon to this group, Odobenocetops was essentially a 'walrus whale' that presumably used its vaulted palate and strong buccal musculature to suction-feed on the soft parts of benthic molluscs.
Even more incredible was the description of a second species, O. leptodon [shown here], that possessed much, much longer tusks (Muizon et al. 1999, 2002). Its left tusk was 25 cm long while the right one was a ridiculous 1.35 m long. O. leptodon is geologically younger than O. peruvianus and appears more specialised in tusk anatomy, in having a longer, broader palate, and in some other characters. However, O. leptodon was more primitive in still possessing a melon and in having orbits that did not allow the same degree of binocular visison as did those of O. peruvianus. It is inferred from these differences that neither species was ancestral to the other, but that both had specialised in distinct ways after diverging. The presence of long, walrus-like tusks in these bottom-feeding suction-feeders strongly implies that tusks act as guides, and are strongly beneficial for this lifestyle. Why the profound asymmetry in (presumed) males? It may be that the suction-feeding was only carried out on the short-tusked left side.
Incidentally, if you're interested in tusked odontocetes remember to check out the Tet Zoo narwhal article here. I still have to come back to monodontids at some time.
Half-beak porpoise
Finally, if you've been reading the comments you will already know all about the bizarre, soon-to-be-published 'half-beaked porpoise' or 'chinny-chin-chin porpoise' or 'skimmer porpoise', currently being worked on by Rachel Racicot and colleagues. A Pliocene phocoenid from the San Diego Formation, it possesses an incredibly elongate, fused, toothless dentary symphysis that extends well beyond the tip of the rostrum. It also sports large bony bosses just anterior to the nares, but given that one of the diagnostic characters of Phocoenidae is the presence of convex paired premaxillary eminences just anterior to the nares, these bumps are most likely just hypertrophied versions of these.
But what the hell was the animal doing with that incredible lower jaw? Clearly, it was leaping out of the water, sustaining some sort of flight, and trawling its lower jaw though the water while gliding through the air. No, I am kidding. We have no idea (or I don't anyway). We await the full description with great interest: an abstract on the taxon (Racicot et al. 2007) is all I've seen so far. The photo of the new taxon was taken by Doug Shore and is used with his permission.
So that's that. For the time being we say goodbye to the Odontoceti. Now that we're in August I need to start spending time getting geared up for conference season. I'm giving a talk at SVPCA in Dublin early in September, so had better get that ready, and continue the desperate quest for finance.
Refs - -
Muizon, C. de 1993. Walrus-like feeding adaptation in a new cetacean from the Pliocene of Peru. Nature 365, 745-748.
- . & Domning, D. P. 2002. The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications. Zoological Journal of the Linnean Society 134, 423-452.
- ., Domning, D. P. & Parrish, M. 1999. Dimorphic tusks and adaptive strategies in a new species of walrus-like dolphin (Odobenocetopsidae) from the Pliocene of Peru. Comptes Rendu de l'Academie des Sciences, Paris, Sciences de la Terre et des Planètes 329, 449-455.
Racicot, R., Deméré, T. & Rowe, T. 2007. Morphology of a bizarre new fossil porpoise (Cetacea: Phocoenidae) from the Pliocene San Diego Formation of southern California, USA. Journal of Vertebrate Paleontology 27 (supp. 3), 132.
Spaul, E. A. 1964. Deformity in the lower jaw of the sperm whale (Physeter catodon). Proceedings of the Zoological Society of London 142, 391-395.
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I have heard of deformed Sperm Whale Jaws but never seen one. That is astonishing - the living animal would have been bizarre to say the least.
If Sperm Whales do not rely on their teeth, does this add to the likelyhood that they incapacitate their prey with debilitating Sonar attacks?
"call me ishmael" etc...
Those deformed sperm whale jaws are really highly interesting, not only as you said for the reasons how they became deformed, but also the fact that sperm whale don´t seem to need their long mandible to hunt. I have seen a colour photo of this mandible some years ago, but it seems this site is no more online. But I found another photo of an even much more deformed sperm whale mandible from the musem of New Bedford: http://www.haveschoolwilltravel.com/content/Nov2006NewBedford/images/NB…
Given its size and the lack of teeth this was probably a female. I don´t think that just physical injuries or similar things can lead to such massive deformations. It looks more if one side of the mandible grew faster since a very early age.
The skull of the skimmer-porpoise looks interestingly very similar in its proportions to those of many fish, including the cretacous Sauropon, but especially some members of the living genus Hemirhamphidae or halfbeaks which hunt their prey directly under the surface.
Just found another bigger photo of this incredibly deformed mandible from New Bedford:
http://flickr.com/photos/petteway/1415566177/sizes/o/
http://flickr.com/photos/jzunc/2148612256/sizes/l/
"..the bizarre walrus whales Odobenocetops..."
Ah, yes. I remember this one from the 'Walking with Sea Monsters' CGI spectacular :)
A great week. A colleague of mine will be in Dublin for that conference - sounds like it should be a good one.
Holy crap, it's like the Helicoprion of whales! (Except at least Helicoprion is symmetrical!)
Heh all this talk of walrus whales brings back memories of a pr-Dr. Naish giving a lecture on whales, which is when I first encountered them. I've seen that photo of the deformed sperm whale before but god know where. I guess the sperm whales don't need the tips of the lower jaw to catch giant squid...
Darren - Thank you! We had a whale of a time....
Darren, a great week on a much neglected group. Amazing how there are so many of those toothy buggers out there, we kill so many of them, there is a huge public appetite for fluff information on them, and yet there are such massive holes in our knowledge about them. Well, you've just gone a long way to filling some of those gaps. Just goes to show that biologists may have all the data, but palaeontologists have the good questions....
Re the Sperm whales with disfunctional mandibles; I've read reports of animals with long-missing jaws that are healthy and well fed. However they are feeding, they don't necessarily need their jaws to do it. Lethal sonar, mad head-butts, or just sucking down kalamari - at the moment, anyone's guess. Wierd animals.
And he didn't talk about beaked whales; does this mean we can look forward to a 'Ziphiid Week' sometime?
This sperm whale jaw is incredible.
Your blog is great! great! great!
Excellent articles on these wacky whales.
Half beaked porpoise: Seems to me that it was a very fast pelagic swimmer chasing fast fish schools; the anterior nare bosses deflecting water from the blowhole which had not yet streamlined like modern cetaceans. But... is it nares or nare? Echolocation requires one nare to be non-functional and asymmetrical, I thought. Did this porpoise echolocate? The extended lower jaw may have help sound reception, since today's odontocetes listen with their oil-filled lower jaw.
If true, that might explain why sperm whales lower jaws are more susceptible to damage, if sound reception is more significant than jaw strength.
Regarding narwhal tusks, I'm rethinking the possibility that it evolved for poking through ice, especially along weak seams between ice floes near the periphery of the pack ice, which is where narwhals are often found, and wave action produces weaker ice fields. Weakened "faults" can probably be detected via echolocation, a concentrated ramming tool/tooth to poke a hole or crack followed by a couple body slams might do it. Compared to belugas, which rely on pre-existing holes often watched by polar bears, having an ice breaker would seem to be an evolutionary advantage.
(or not..)
If you're going to come right out and mention narwals, I supposed I'm obliged to post this again:
http://www.scarygoround.com/?date=20080711
Ddeden: I'm sorry, I'll never be able to credit such a crude primary use for something as heavily innervated as the narwhal tooth. I'm sticking with sensory organ, and hypothesizing specifically a very direction-sensitive sonar receiver... presuming, of course, that it's not really meant for detoxifying poisoned fresh-water courses.
I'll bet that phocoenid was either using its weird lower jaw to "skim" the seafloor or to probe underwater rock crevices.
Ddeden:
The premaxillary bosses are associated with the sound production system of odontocetes. In other odontocetes (e.g. delphinids) the dorsal surface is slightly concave, and that surface is called the premaxillary sac fossa. In phocoenids it is convex, and highly convex as in this critter. In any event, there would have been several inches of soft tissue (including a melon, and the extremely complex facial organ complex) between those bosses and the outside of the animal.
Porpoises lost cranial asymmetry, and are thus secondarily symmetrical. All odontocetes echolocate, symmetrical or not (that includes extant phocoenids).
As for narwhal tusks... I have a hunch that Nathan's suggestion is close to the truth. There are two possibilities, or both: sexual selection, or a functional advantage, which i would think is related to sound reception. Many odontocetes have extremely dense rostral bones to aid in receiving sounds; it only makes sense to grow a giant-ass tusk on the front of your face, which would be even more sensitive than dense bone.
Lastly... monodontids evolved and diversified in temperate latitudes, not in arctic waters... granted, the narwhal fossil record is nil, but it is currently most parsimonious to assume that Monodon evolved in temperate latitudes (just like Delphinapterus did). Just like odobenids, it appears that monodontids were rather late (i.e. Pleistocene) in their adaptation to cold boreal waters.
First post here...big fan of the site.
Bobby, I am not sure one can strictly consider porpoise craniums as symmetrical. IIRC, Racicot found that the while the skulls "look" mostly symmetrical on the outside, their sinuses are still asymmetrical (hopefully I spelled that right).
FYI, I would be skeptical of where the skimmer porpoise actually rests in the phylogenetic tree (other than within phocoenidae). The character matrix Racicot used was almost completely based on the recent Fajardo et al. paper. fossil porpoises were included, but I believe the lead author was less concerned with extinct taxa, and they are mostly coded from the literature. I believe Racicot plans on redoing the phylogeny at some point.
This guy was certainly had an interesting feeding morphology, and I believe Racicot has discussed looking at the dental wear with Brian Beatty, and I have discussed with her sampling this guy for isotopes, so we will have to see what happens.
Hey Morgan,
Ya, I remember the asymmetrical sinuses - I was explaining that a symmetrical skull in a cetacean does not mean it cannot echolocate.
As for the phylogeny... I added a bunch of characters and some more extinct taxa to the Fajardo et al. analysis, and coded my Purisima Fm. skimmer porpoise cranium - it usually plotted fairly basally, but that was a sort of 'back of the napkin' analysis if you will.
Morgan,
I remember the asymmetrical sinuses - I was explaining that a symmetrical skull in a cetacean does not mean it cannot echolocate, and that since all odontocetes can echolocate (asymmetrical or not) that this porpoise could as well.
DDeden--
Nares is plural; naris is the singular.
looks like the jawbone from a frumious banderstanch!
the "flying porpoise" looks like the "antarctic narwal that Karl Shuker writes about.
Someone else wrote about it too... :)
Naish, D. 1997. Are there narwhals in the Southern Hemisphere? Exotic Zoology 4 (2), 3.
umm, ok, IMO narial emplacement in odontocetes is asymmetrical, with external secondary symmetry; in mysticetes it remains symmetrical bilaterally, which is why blue whale blowholes resemble human noses, but dolphins blowholes don't. (naris? ok)
Narwhal tusks are enervated along the sides, not at the tip, (right?) so I'm going to stick with this: Adult male narwhals use their "sonic lance" to improve ice fracture finding and piercing, long tusk = better ice/snow sonar, not needed by other whales nor by small females which follow, but possibly also used by submerged walruses (they produce a loud subsurface "bell" sound) and Odobenocetops. Evolving at temperate zones included seasonal migrations to arctic waters, as that is where their (non-lunged) foods go when summer comes. "Crude"? Not at all, very elegant combination of an extended omni-directional sonar microphone + long spiraled drill bit in one piece of hardware, also improves general hearing and used as weapon during male-male battles.
(as always, I could be wrong)
If I remember correctly, the odontocete blowhole appears as one hole externally because the nares converge internally.
As far as narwhals using their tusks to break ice... I'm not sure that narwhals have ever been observed doing so. I could be wrong, of course.
However, given the ancestral temperate range of monodontids, and the appearance of an elongate tusk in Odobenocetops (a subtropical/temperate critter), I'm going to reiterate my guess that tusks evolved prior to the invasion of arctic waters by monodontids (and thus arose for some other function). Actually finding fossils of Monodon would test this parsimony-based hypothesis.
I should also mention that walruses cannot echolocate (e.g. use biosonar), and Odobenocetops is one of the few odontocetes which probably could not echolocate at all. Additionally, the walrus tusk evolved at temperate and even subtropical environments... and the same goes for Odobenocetops (which has not yet been recorded south of Peru, so it is doubtful it ever saw ice).
That twisty sperm-whale lower jaw!... Reminds me of weird shark Helicoprion
Is this a coincidence, or something to do with mega-molluscan prey?
What goes/went on down there, undersea?
(Mind boggles.)
I'd agree that (small) tusk development was probably initially a (sub)tropical feature as in sirenians. It is the great elongation in walrus, narwhal and odobenocetops tusks that I think occurred due to selection for (seasonal?) (sub)polar foraging migrations where pack ice and numerous ice bergs were present. Sirenians and walrus both produce sounds underwater but feed primarily on benthic immobile foods, unlike highly specialised echolocating dolphins which chase moving prey, this doesn't mean they do not use sound (echolocation) to navigate. (Compare to cave swallows which echolocate like bats but not for foraging, only for cave navigation.) Both sperm whales and humpback whales click underwater, but differ anatomically from dolphins' biosonar hardware, so I'm not sure that we can be certain regarding the use of underwater vocalizations in extinct animals.
Yes! :-)
Would require the whole animal to spin. Which I have a hard time imagining -- entirely apart from the fact that they've never been seen even trying to poke holes into ice.
The pacific was extremely warm during the Pliocene... I doubt that (given Odobenocetops' known occurrence)it ever contact sea ice.
I'm pretty sure that walruses and sirenians don't echolocate. Only odontocetes can (out of marine mammals anyway). In contrast to cetaceans, the ear of pinnipeds is little changed from terrestrial arctoid/canoid relatives. There is no evidence that they can echolocate. And lastly, just because I can submerge myself in a pool and make a sound doesn't mean I echolocate.
DD: "tusk like a long spiraled drill bit"
Would require the whole animal to spin. Which I have a hard time imagining -- entirely apart from the fact that they've never been seen even trying to poke holes into ice.
Posted by: David Marjanović
I was speaking of ice faults, not solid ice, so the tusk might be used to would pry & poke weak joints detected by sonar. It might only be done a few times in a lifetime of a male. Not exactly like a drill bit, but strong in all directions due to the spiral.
===
The pacific was extremely warm during the Pliocene... I doubt that (given Odobenocetops' known occurrence)it ever contact sea ice.
I'm pretty sure that walruses and sirenians don't echolocate. Only odontocetes can (out of marine mammals anyway). In contrast to cetaceans, the ear of pinnipeds is little changed from terrestrial arctoid/canoid relatives. There is no evidence that they can echolocate. And lastly, just because I can submerge myself in a pool and make a sound doesn't mean I echolocate.
Posted by: Boesse
If the Odobenocetops fossil was found on the Peruvian coast, why could it not have migrated to the antarctic, considering that penguins, seals and sea lions are both at the Galapagos Isles and Antarctica?
Blind humans can echolocate in air, but not at the level of bats, I would not be surprised if humans could be trained to echolocate underwater as well, to a limited degree. Your definition of aquatic echolocation is limited to odontocetes, but theirs' is merely the best. Echo + locate simply means using transmitted and received sound as part of navigation, so I consider it a general condition among many marine animals.
Because Odobenocetops has not yet been found in Chile. And its not exactly for lack of trying - really prolific localities of the same age (and share other marine verts, eg. pinnipeds with the Pisco Fm.) are known in Chile, and odobenocetops is not yet known there. So I doubt it ever came into contact with cold antarctic waters.
Your definition of echolocation is faulty... first off, humans cannot hear directionally underwater (this is critical; it is anatomically and physically impossible for us to do so). Directional hearing is required for echolocation. Even mysticetes can hear directionally, yet they do not echolocate. And in any event, experiments with captive pinnipeds (and observations in the wild) have shown that they do not echolocate.
In any event... my definition of aquatic echolocation as restricted to odontocetes is correct, because only odontocetes have been observed doing this behavior (!!!) and only odontocetes possess the unique headgear to do so.
"Because Odobenocetops has not yet been found in Chile."
Penguins and pinnipeds spend much time on the shore, not hard to find carcasses of young and old. I don't think Odobenocetops spent any time on the shore except for strandings. If they wintered in Peruvian-equatorial waters and summered in antarctic waters, fossils might be found there, but probably not on shores or shallows mid-way between (unlike penguins and pinnipeds).
"my definition of aquatic echolocation as restricted to odontocetes"
Yes, I refer to that as 'prey pursuit bio-sonar', while I consider echolocation to be 'locating by echo', odontocetes being special case.
But the fossil assemblages in Chile are not foreshore deposits - beach deposits almost never produce marine vertebrate fossils, because bone is typically pulverized. Read Walsh and Martill 2006 about the depositional environment of one of the more important Chilean localities that so far has not produced Odobenocetops.
'prey pursuit bio-sonar' is echolocation, aka active biosonar. Locating by echo is the same thing. No other marine mammals produce sounds in order to locate objects with said sound's echo. In fact, I'm not even sure that pinnipeds can hear directionallly underwater - Berta et al. 2006 state that the pinniped ear is modified for bone conduction hearing, which is a type that does not allow directional hearing, if I remember correctly. Directional hearing is a prereq for echolocating, period.
Berta, A., J.L. Sumich, and K.M. Kovacs. 2006. Marine Mammals: evolutionary biology. Associated Press. San Diego.
WALSH, S.A. & MARTILL, D.M. 2006. A possible earthquake-triggered mega-boulder slide in a Chilean Mio-Pliocene marine sequence: evidence for rapid uplift and bonebed genesis. Journal of the Geological Society, London, 163, 697-705.
"But the fossil assemblages in Chile are not foreshore deposits - beach deposits almost never produce marine vertebrate fossils, because bone is typically pulverized. Read Walsh and Martill 2006 about the depositional environment of one of the more important Chilean localities that so far has not produced Odobenocetops."
That seems to confirm my point, they did not live in Chile, (except possibly at the southern tip, today noted for harsh currents, climate) oceanic surf would be hard going so they would have avoided the coastal surf and stayed far offshore during their transit, then at either end of the journey would have found bays and shallows for foraging/resting/mating/birthing. Has offshore south Argentina coasts been checked for fossils?
"'prey pursuit bio-sonar' is echolocation, aka active biosonar. Locating by echo is the same thing."
Prey pursuit bio-sonar is a further specialization, derived from general echolocation (see humpback whale clicking). As stated before, swifts (birds) echolocate in caves, but do not employ directional bio-sonar in prey pursuit. Micro-bats use bio-sonar both in cave navigation and in prey pursuit. Both use echolocation.
I fully agree that most likely pinnipeds and sirenians and sea and marine otters do not use directional bio-sonar (Note the large vibrissae and forward large eyes).
I never saw that pic before.
I have a shot of another deformed sperm whale mandible from the Nantucket Whaling Museum if you'd like (email me). Sadly, there was no accompanying text nor any staff who had more info on it.