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Re: Alvarezsaur spurs (was Re: dino-lice)



Here is a film that shows that myrmecobius' tongue can protrude a distance
about equal in length to the skull. I haven't found any information on
their hyoid morphology, but I'd be surprised if it was much like that of
woodpeckers. There's surely more than one hyoid geometry that can endow an
animal with a long protrusible tongue.

http://www.arkive.org/numbat/myrmecobius-fasciatus/video-10a.html



> That certainly does not sound anything like the apparatus in woodpeckers,
> which is considerably longer than the skull and in fact wraps around the
> back if the cranium. Unless the tongue structure was very different it
> does not sound like Shuvuia could have had much in the way of an
> extensible tongue.
>
> This is not necessarily fatal to Shuvuia being a myrmecophage as a long
> tongue is not necessary if ants are simply being picked up from the
> substrate rather than being estracted from cavities. Climacterids do not
> have a particularly elongate or extensible tongue either (certainly
> nothing like that seen in woodpeckers) and, as I said earlier, they eat a
> lot of ants (especially from the ground).
>
> Ronald Orenstein
> 1825 Shady Creek Court
> Mississauga, ON
> Canada L5L 3W2
>
> On 2011-05-03, at 6:46 AM, Mickey Mortimer <mickey_mortimer111@msn.com>
> wrote:
>
>>
>> Yes.  In Shuvuuia IGM 100/977 and 100/1001, both photographed in Chiappe
>> et al. (2002).  They're ~37% of skull length, slender and bowed
>> laterally with no expansions I can see.
>>
>> Mickey Mortimer
>>
>> ----------------------------------------
>>> Date: Tue, 3 May 2011 06:38:25 +0800
>>> From: ron.orenstein@rogers.com
>>> To: augustoharo@gmail.com
>>> CC: d_ohmes@yahoo.com; dinosaur@usc.edu
>>> Subject: Re: Alvarezsaur spurs (was Re: dino-lice)
>>>
>>> Picid tongues are supported by an extremely elongate hyoid apparatus. I
>>> would expect that if alvarezsaurids had a protrusible tongue the hyoid
>>> would show specialization to that effect - are hyoid elements known for
>>> the group?
>>>
>>> Ronald Orenstein
>>> 1825 Shady Creek Court
>>> Mississauga, ON
>>> Canada L5L 3W2
>>>
>>> On 2011-05-03, at 2:09 AM, Augusto Haro  wrote:
>>>
>>>> Perhaps conservation of canines until developing powerful arms with
>>>> large claws is a way an anteater can protect itself. Phylogenetically,
>>>> conservation of canines makes sense, overall if descending from a
>>>> clade where the canines were much used. At least, there is an
>>>> intraspecific struggle selective force acting for their conservation,
>>>> in absence of other weapon. I once saw a video with an aardvark trying
>>>> to bite a cheetah which was trying to play with it. I suppose that
>>>> although biting will not be great thing against a larger hyena, lion
>>>> or leopard, it may at least diminish the list of predators, because
>>>> the similarly sized jackal and Cape badger would likely go for it if
>>>> this defense was not present (as far as I was able to observe, no
>>>> matter how courageous they are, mammalian carnivores do not prey on
>>>> other carnivores not smaller than they one-on-one, probably because
>>>> they have canines similar in effect to their own).
>>>>
>>>> Returning to the question of mymecophagy and cursoriality, I think
>>>> they are not exclusive, as shown by Proteles, and also the canid
>>>> Otocyon, but this is constrained because most myrmecophages today are
>>>> quadrupedal mammals, where you cannot specialize the forelimb for
>>>> myrmecophagy in the sense of anteaters or pholidotans while keeping
>>>> being a cursor. When termites go around without need to break their
>>>> nests, a cursor may perfectly feed upon them. The limbs of cursors are
>>>> energy-saving because of their longer stride and lesser weight
>>>> distally, requiring less force to be moved forwards, so can easily be
>>>> used for an energy-saving myrmecophage. It seems that the inactivity
>>>> of the specialized Proteles has more to do with the inactivity of the
>>>> termites themselves. Likely, if the termites were less seasonally
>>>> variable in activity, or active during a larger part of the day, the
>>>> aardwolf would be a similarly more active animal.
>>>>
>>>> Now, turning back to alvarezsaurs, they may have simply specialized
>>>> their forelimb without need to lose their hindlimb cursorial
>>>> adaptations (as many said). Thus, lack of cursoriality in most
>>>> myrmecophagous mammals can be explained because of the adaptation of
>>>> the forelimb, instead of metabolic rate constraints. Now, if
>>>> alvarezsaurids were capable of preying upon termites in their nests,
>>>> thanks to their forelimbs, they may have likely enjoyed this food
>>>> during a larger part of the year, overall accepting the calid
>>>> conditions loved by termites were more common in the Mesozoic.
>>>>
>>>> Other thing: there are birds, like picids, which have a long, sticky
>>>> tongue to grab insects. This seems to make them more similar to their
>>>> mammalian myrmecophagous counterparts. Tubular mouths are less common
>>>> outside mammals because there are no cheeks (oh, well, except for
>>>> seahorses and curculionids). We may say it was difficult for
>>>> alvarezsaurs to have had a tubular mouth because of phylogenetic
>>>> constraints.
>>
>


Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
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212 496 3544
jaseb@amnh.org