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RE: Claw function in Deinonychus



Mickey Mortimer wrote:

Achillobator's ungual seems to be manual (Senter et al., 2004), as I had listed as a possibility back in 2000

This is kind of funny, considering that _Achillobator_ was actually named for the slashing ungual on the foot. Interestingly (or not), in their description of _Bambiraptor_, Derstler et al. (2000) proposed that _Achillobator_ might be a chimera based on material from two or more theropod species, with only the pedal unguals coming from a dromaeosaur! They interpreted the cranial, pelvic and caudal elements as sharing "no unique features with the Dromaeosauridae." Can't say I agree, though.


John Scanlon wrote:

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

Do you mean the inner toes? Cassowaries appear not to use their spike-like inner claws for predation, only in defense and/or to vent their bad temper on people who refuse to feed them.


Seriemas (which can fly, and are predominantly terrestrial) are reported to use their enlarged inner claws as climbing aids. Here this claw also plays a role in predation, and is actually curved. The related phorusrhacoids also show an enlarged (but not hyperextensible) sickle-claw.

(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?

Only Feduccia (and a very few others) regard all birds as 'non-dinosaurian'. :-) I know what you mean though.


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).

I couldn't agree more, John. Furthermore, if these small maniraptorans were generalists, they may have been partly herbivorous and headed up the tree for the leaves, fruits or seeds. The interesting thing is that the basal members of the Oviraptorosauria-Therizinosauroidea clade (the sister taxon to Deinonychosauria) were at least partly hervivorous, and this might have been true of troodontids as well. Among non-avian maniraptorans, dromaeosaurids (or just dromaeosaurines) may be the exception in being hypercarnivorous.


Ralph Miller wrote:

To determine the utility of a robotic dromaeosaur leg as a model for studying the capabilities of a living dromaeosaur's leg, it would be helpful to set up a parallel experiment that would investigate how closely the damage inflicted by a robotic cassowary leg would mimic the damage caused by a real cassowary. I don't know if a cassowary could be provoked to lash out at a fresh pig or (perhaps more appropriately) a fresh croc carcass, but there are reports and medical records of cassowary-inflicted wounds that could be used for drawing comparisons.

Apparently cassowaries become aggressive when their expectation of food is denied. (This is why it's a very bad idea to feed a wild cassowary.) It is not difficult to rile them up.


Cheers

Tim