Natural Science Forum / Biology / Paleontology / November 2005

Oh yes - sorry for that. Here's the citation:

Manning, P. L., Payne, D., Pennicott, J., Barrett, P. M. & Ennos R. A. 2005.
Dinosaur killer claws or climbing crampons? Biology Letters. FirstCite Early
Online Publishing. 3 pp. DOI: 10.1098/rsbl.2005.0395
http://www.journals.royalsoc.ac.uk/openurl.asp?genre=article&id=doi:10.1098/rsbl
.2005.0395

[snip]
... It sounds fairly convincing to me. Two questions:

A few observations:
The idea of dromaeosaurs climbing the bodies of their prey has
certainly been suggested before, possibly first by Ostrom but then in,
for example, Bob Bakker's 'Raptor Red'.

I've never been convinced that 'disembowelling' was a plausible
function for such a strongly curved claw on a very flexible digit.  The
ostrich and cassowary are widely reputed to be able to disembowel
humans, dogs, lions etc. with a front kick, and though I do not have
details of any documented cases this seems worth investigating (just
annoy your local ratite with a pig carcass on a stick?). Ratite claws
are not especially sharp-tipped, thick and strong but relatively weakly
curved; but the middle claw in cassowaries is quite variable in length
(fairly ordinary and emu-like in the Australian species, much longer in
some New Guinea animals) suggesting it may be evolving specialised
functions within the extant genus.  Has Feduccia written any reviews on
claw geometry and disembowelment in non-dinosaurian birds?

As Manning et al conclude, a strongly curved claw claw with an
elliptical cross-section is not an effective cutting tool; and there
seems to be no evidence from ungual morphology to override the
inference from the EPB (extant phylogenetic bracket, i.e. parsimonious
character reconstruction based on living animals). To reconstruct the
claw with a ventral cutting ridge would thus be an extrapolation that
would have to based on either extant analogues (of which there are
apparently none) or a biomechanical argument for the claw being
modified in other ways for disembowelling (probably ruled out by the
strong curvature).

Tree-climbing, why not?  Likely to be more important than prey-climbing
most of the time, I would think, since most maniraptors were relatively
small and likely to be generalist insectivore-carnivores like varanid
lizards. If the claw morphology evolved in association with arboreal
foraging (for insects or small vertebrates), nocturnal perching, or
juvenile escape behaviour in small generalists, its use in predation
would be an 'exaptation' that might have been critical in allowing
specialisation on large prey (which may or may not have actually
occurred).

There may now be enough different species of maniraptorans known from
foot bones to map out some morphological trajectories and compare with
limb proportions and dentition, to see if mega-carnivory or potential
arborealism is the better explanation for the origin of the big claw.
Thesis topic for someone?