Given that we’re all enjoying gawping at Caperea so much, I may as well finish up and use the rest of the photos that Joy Reidenberg kindly provided. First off, here’s the skull from the side.
It’s really weird: that lower jaw shape is utterly unlike anything else present in baleen whales, being comparatively deep and ‘heavy’ in appearance, with a downward flexure near the tip (is it just me, or does this look a bit like a flamingo mandible?). In comparison, the lower jaws of rorquals, grey whales are kin are laterally bowed, beam-like bones with cylindrical cross-sections. Those of right whales are much deeper, but they’re still not much like the Caperea lower jaw; they’re fairly straight and lack the down-curved anterior portion. As usual we have no idea why Caperea’s lower jaw is like this: remember that (to my knowledge) nobody knows what it eats [UPDATE: not entirely true - be sure to see the comments below], or how it eats (is it a skim-feeder, like right whales, or a lunge-feeder like most rorquals, or both, or neither?). Anyway, here’s the skull seen from below…
Here’s the whole skeleton in right lateral view…
And here’s the ribcage, again showing nicely the peculiar, thick posterior ribs…
Finally, here’s the distal end of the tail. Emily Buchholtz (2010) said that determining the precise number of vertebrae in Caperea is difficult because some of the distal-most caudals are virtually always missing. As everyone who knows whales knows… the caudal vertebrae that support the tail flukes have a distinctive cross-sectional shape, as does the vertebra positioned at the very start of the fluked part of the tail (it’s called the baseball vertebra). This is all great osteological correlate-type stuff, and has allowed people to show that fossils whales like Basilosaurus had tail flukes (Gingerich 1998). If we knew more about the shape and relative size of the fins and tail flukes of Caperea, we might be able to make some interesting inferences about its manoeuvrability, ability to accelerate, swimming speed and hence possible prey preference, since recent work (Woodward et al. 2006) has confirmed good correlation between these factors.
As usual, we long to know so much more. Many thanks to Joy for sharing the photos you see here (they were taken in New Zealand). For previous articles on Caperea and other baleen whales, see…
- A 6 ton model, and a baby that puts on 90 kg a day: rorquals part I
- From cigar to elongated, bloated tadpole: rorquals part II
- Lunging is expensive, jaws can be noisy, and what’s with the asymmetry? Rorquals part III
- The newest whales
- Inside Nature’s Giants part II: whale guts and hindlimbs ahoy
- When GREY WHALES – you know, from the PACIFIC OCEAN – crossed the Atlantic
- Pouches, pockets and sacs in the heads, necks and chests of mammals, part III: baleen whales
- Did I mention that Caperea is really, really weird?
Refs – –
Buchholtz, E. 2010. Vertebral and rib anatomy in Caperea marginata: implications for evolutionary patterning of the mammalian vertebral column. Marine Mammal Science 10.1111/j.1748-7692.2010.00411.x
Gingerich, P. D. 1998. Paleobiological perspectives on Mesonychia, Archaeoceti, and the origin of whales. In Thewissen, J. G. M. (ed) The Emergence of Whales. Plenum Press (New York), pp. 423-449.
Woodward, B. L., Winn, J. P. & Fish, F. E. 2006. Morphological specializations of baleen whales associated with hydrodynamic performance and ecological niche. Journal of Morphology 267, 1284-1294.