Re: Another can, anyone?

["Jaime Headden" <jaemei@hotmail.com>]

This reminds be of way back when I first picked up _The Dinosaur 
Heresies_ by Bakker. Not saying this is the source of your info, Dave 
[in my best Hal voice].

<Here as I understand it are the arguments against:

1) There is a lack of well-developed skull processes that would indicate 
points of attachment for trunk muscles.

2) Trunk muscles develop from facial muscles, and sauropods had very
poorly developed facial muscles.>

  Two big reasons why they wouldn't've had them.

<3) Sauropod teeth are strong and well-worn, obviating the need for a 
trunk.>

  The structure of a sauropod's jaw is deep, with the snout very 
flat-ended, with *Diplodocus* an exception. The structure of the teeth 
aside, put together, the teeth make a nice chopping machine, shearing 
away at large clumps of food, swallowing, then shearing again, in a 
large, nearly continuous cycle. The structure of sauropod necks supports 
this, even the neutral positioning of the necks, more reliable in a 
"rest" mode; euhelopodids would have had nearly vertical necks, as 
woulkd brachiosaurs, so diet could have been different than low level 
feeding.

<With regard to (1), I would not expect to see well-developed processes 
like those of elephants.  Elephants have large, powerful trunks that 
largely make up for the fact that their necks are very short and 
relatively immobile.  Sauropods had enormous, highly mobile necks.  I 
believe that sauropod trunks were small and relatively weak.  As for 
(2), many vertebrates have fairly elaborate facial appendages, even 
mobile ones, despite having immediate ancestors with no facial muscles.  
Some examples include deep-sea fishes, chameleons, twig mimic snakes, 
tentacled snakes, and hornbills.>

  Hornbill crests, like cassowary crests [casques], are made of keratin 
pretty much stuck to the bird's head, and in at least one hornbill's 
case, is hollow, functioning as a display device or resonating chamber, 
like the hornbill's and toucan's beaks themselves.

<Consider the arguments in favor:

1) All large sauropods have relatively large external nares which occur 
high on the skull.>

  Some of the primitive sauropods, the shunosaurs and euhelopodids, 
reaching over sixty feet max, has forward set nares, near to the snout, 
as did some primitive camarasaur-morph titanosaurs like *Malawisaurus*.

<If we look around for terrestrial vertebrates with similar nares, we 
are faced with a striking fact.  The only species that have such nares 
are those with probosci.  Of the species that have small, forward nares, 
not one has a trunk.>

  Hmm. The tapir has nares almost identical to that of a horse, as does 
the rhinoceros. Now, true, rhinos have very mobile lips, but the 
nostrils are not connected to the lip's movements, making "trunk"-like 
nares not indicative of trunks. Diplodocid skulls have elephant-style 
nares, though, and this was Bakker's point on restoring Diplo with a 
trunk. More on this later.

<2) There is a distinct area of skull topography surrounding the 
external nares in sauropods.  There must have been some kind of unusual 
structure here.  It may have been a sound chamber or crest, but other 
dinosaurs had sound chambers and crests without the modifications of the 
nares seen in sauropods.>

  They _are_ sauropods, not analogous to ornithchians in this case. Too 
different. Some theropods (*Monolophosaurus* and *Oviraptor*) had the 
enlarged nasal chambers invade their crests to some degree or another. 
Take *Ornitholestes'* example, with the incomplete bridge of bone that 
surmounted his snout; sauropods lack this bridge, and in fact so do we, 
but we make up for the lack in cartilage, as do other mammals, and it is 
possible that cartilage was used in the forming of a small, not 
elaborate formation atop the nose to extend the nares in any particular 
way, but a trunk is not as likely as it seems, since this is a mammalian 
adaptation.

<3) Some sauropods have peg-like teeth seemingly inadequate for clipping 
vegetation. For an animal with such a need to consume to have such blunt 
teeth is strange to say the least.>

  You did say they were adequate to the task, and I think I said how 
they were.

<4) Sauropods, the very dinosaurs that most needed to have high rates of 
food intake, also have nares that suggest an excellent mechanism to
accomplish just that goal.  It is too much of a coincidence.  A 
proboscis would have increased the rate of intake dramatically; as the 
mouth manipulated one piece of vegetation, the trunk would reach out for 
the next.>

  Now, this proboscis would be located (or originated) at the top and 
back of the skull, not in front as in all other trunked animals, which 
might obviate its prescence. Bakker proposed the trunk would be 
connected to the snout's surface then hang off at the end, but as there 
are not analogies, we can't begin to figure out the osteological 
requirements for this.

<Your comments are welcome, please resist the urge to use words like 
stupid, moron and dullard, applicable as they may be.>

  You are none of these. I think it's nice that once in a while someone 
brings up an old topic or something Bakker or one of the other 
"heretics" came up with or simply passes on [Bakker will be the first to 
say he didn't come up with much of "his" material]. Greg Paul, right 
here on the list, is as much a heretic in some of his novel ideas, and 
they, too, are as much worthy of discussion as trunked sauropods.

Jaime A. Headden

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