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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)



Sorry about insisting with the claws once the discussion entertained
other themes, but just wanted to note that dromaeosaurs seem to have
relatively little teeth and not quite powerful jaws.

I should spect an animal killing large game to have relatively large
teeth and more powerful jaws in order to more strongly tearing off
flesh from the death prey. Moreover, the larger the prey, the thicker
the hide, and the more necessary is having some more developed teeth.
Unless they cutted the hide with their digit II ungua and then didn't
need the teeth to be powerful enough for the task.

In having relatively reduced teeth they resemble Archaeopteryx. With
their small teeth, dromaeosaurs should have go after small prey,
perhaps snakes or small dinos. After all, defensively hypertrophied
claws are seen in other dinosaurs, including birds, such as
therizinosaurs, iguanodonts, cassowaries, apparently oviraptorosaurs.
Even the "fighting pair" do not prove predation, but just indicates
fighting (perhaps the Protoceratops was trying to gett off the
deinonychosaur from its realms, or youngs).

2008/9/26, Augusto Haro <augustoharo@gmail.com>:
> No quantitative data, David. There are other interesting things about
> the theory of the slashing dromeosaur ungual:
>
> -In sabertooths, for stabbing large prey they need enlarged neck
> musculature, as indicated by the enlarged mastoids processes, and
> perhaps the prominent nuchal crests. I cannot see such enlarged
> attachment areas of muscular insertion in the hindlimb of
> Deinonychus, overall of the origin of the musculature for the digital
> flexors in the tibiotarsus or tarsometatarsus. I acknowledge there is
> a well-developed cnemial crest, but not better developed than in most
> other theropods. Thus, if musculature for stabbing in sabertooths is
> so hypertrophied for just stabbing, one can suppose that Deinonychus
> should have even more hypertrophied musculature for slashing, that
> requires more strenght than stabbing.
>
> -Among human blade weapons, I do not know of slashing weapons where at
> the same time the flesh of the enemy/prey is hitted by an edge and a
> long point at its extreme (although most blade weapons are made to
> kill other humans, not elephants).
>
> -the transversal compression of the ungual, being there a ventral edge
> or not, can be alternatively related to increase resistance in the
> direction in which the point of  the ungual enters, which is not
> latero-medial (it would give the claw greater resistance to the
> shearing forces acting on the base of the ungual).
>
> -Large prey killing would require Deinonychus to jump over its prey
> and perhaps climb on it. The criticism to the arboreal paravian
> theory, that deinonychosaurs do not present special climbing devices,
> may apply to it climbing prey (although prey's hide is softer than
> tree bark, so it is more easy to sunk the claws there). For example,
> perhaps the relative robustness of Smilodon when compared to the lion
> may enable the sabertooth to climb its large prey – somewhat
> off-topic, most cats climb well, but lions seem to be much large for
> the general cursorial construction of cats to permit them to support
> their weight; cursorial adaptation likely do not permit them to exert
> the forces that climbers of comparable size, but not cursorial, such
> as black bears and gorillas, can exert-. The forelimbs of Deinonychus,
> even possessing large unguals, are too slim to suggest this
> leopard-sized animal (Ostrom 69') could climb or support itself so
> easily to the prey. With its short metatarsus (Ostrom 76'), its
> ability as a leaper would also not be so good.
>
> -In Ostrom's 1969 work, fig. 74, digit II ungual is well removed from
> the ground when the metatarsus form a less than 90 ° angles with the
> soil behind the ground-foot contact. This occurs on early phases of
> the step. However, at later stages of hindlimb retraction (near the
> end of the step), the metatarsus will form an angle greater than 90°
> with the soil behind the ground-foot contact. Here it seems that the
> claw cannot be maintained so far from the ground at retraction.
>
> -Greater range of extension in digit II is seemingly common in other
> dinosaurs. For digits II-IV to be approximately subequal in lenght (as
> in Deinonychus), digits with more interphalangeal articulations (as
> digit IV) would theoretically be more flexible and capable of more
> extension and flexion than digits with less interphalangeal
> articulations (as digit II) if all interphalangeal joint permitted the
> same movement range, so that more lateral digits would be more
> "extendable" and "flexable". This can be compensed if the
> interphalangeal joints of the digits with less phalanges (digit II)
> permit greater freedom of movements, and would not necessarily imply
> an hyperextended position.
>
> -Ungual phalanx of digit II is larger than those of digits III and IV
> in most birds, perhaps related to the fact that to have digits II-IV
> of similar lenght, the less numerous phalanges of digit II have to be
> more elongated. This being said, I recognize the digit II ungual in
> dromaeosaurs is elongated with respect to the two phalanges basal to
> it, and the whole feet, in relation to what is seen in other
> dinosaurs.
>
> Again bothering everybody with weird applications of the EPB, but many
> birds hit with their limbs when attacked (yesterday I saw a hen with
> chicken flying half a meter from the ground against a boy and throwing
> kicks in the air towards him – the boy fled), what is better
> accomplished by cassowaries (with large digit II ungual) and
> ostriches, which are said to have killed dogs. Seriemas and secretary
> bird seem to use the digit II claw to kill small prey, of course they
> are not entirely comparable, and perhaps rather derived, although I
> heard of chicken killing snakes with both feet and bill. So, with use
> of the EPB, may we think of a defensive, intraspecific fighting, or
> not-so bigger than itself prey predation function for the ungual in
> paravians?
>