Re: Diplodocus: Return to the Swamps????

[don ohmes <d_ohmes@yahoo.com>]

--- On Mon, 12/14/09, David Marjanovic <david.marjanovic@gmx.at> wrote:

> From: David Marjanovic <david.marjanovic@gmx.at>
> Subject: Re: Diplodocus: Return to the Swamps????
> To: "DML" <dinosaur@usc.edu>
> Date: Monday, December 14, 2009, 6:23 AM
> >  Sounds like a buffet for
> crocodilians.
> 
> Exactly. If you're in a swamp and can't move quickly, the
> crocodiles will eat you alive. Goniopholidids had cutting
> edges on their teeth. None of this death roll business --
> they could just come in and take a bite.

Obviously, hippos will be extinct soon. Elephants in swampy areas, too. Oh well 
, easy come, easy go...

Anyhow, the croc aspect of swamp living having been largely dealt with 
previously, I will post an answer now (see below). Relative vs absolute power 
(also previously covered) will be combined w/ thoughts about the appearance in 
the geo-record of vertical limb elements and dry-land sauropod death at a later 
time . This is another (very) long post, so chopped text will be "repaired" in 
a subsequent post...

The image of a lone mud-constrained giant covered by ant-like swarms of 
knife-toothed croc-types isn't likely a realistic scenario in a swamp. Crocs 
are ambush predators, and therefore do not populate the homogenous areas 
covered by swamps as densely as they do natural nick-points like those sections 
of rivers and lakes used as waterholes by the denizens of large swathes of 
terrestrial habitat. Scenes of lone sauropods attacked on slippery waterhole 
approaches by ant-like swarms of highly cursorial bipedal saw-toothed 
land-sharks equipped w/ claws that might be useful for climbing columnar legs 
and flanks seem more compelling. Not to mention attacks by packs of allosaurids 
w/ great balance and traction :)...

Assuming an adult sauropod is in mud so deep that the base of the neck at the 
water/mud surface, they would be quite vulnerable to croc attack, especially if 
the head was also at that level. In shallower situations, it is the croc that 
is tactically vulnerable, mostly to stomping, especial
here groups* of sauropods are involved. Obviously, there is an advantage to 
tallness and therefore size in this case, and therefore another potential 
vector for directional selection to giant-ism.

Note that putative swampy refugia are likely to be tree-free in areas 
(particularly after thorough tromping by generations of sauropods), and 
therefore ideal for the much-dreaded surface-skimming tail-sweeps**, as opposed 
to terrestrial environments, where serious injury to hypothetically super-sonic 
tail-parts seems near-certain. 

Also, a well-trodden bottom laced w/ the bones of over-bold predators and 
compacted vegetative material would offer the hind legs an excellent platform 
from which to launch a counter-attack w/ the relatively compact front feet. In 
the case where a bottom cannot be touched by the would-be predator, and the 
long neck is hard to ambush due to elevation, the tactical advantage of the 
sauropod would be overwhelming, even in the crocodile case. 

Areas where even the long legs of sauropods cannot find a bottom might be 
avoided by sauropods, and therefore controlled by croc-types, but even that 
does not seem like a sure thing, given sauropod size, and their ability to 
alter the environment to their advantage. I think a 'sauropods move in, crocs 
move out' scenario or 'live and let live' would be the better guesses in most 
specific cases.

Watching the familiar video of the gigantic croc(s) attacking the flanks of 
migrating wildebeests gives the impression that even w/ those relatively small 
herbivores, attack success is hardly guaranteed. Further, breaking a sauropod 
into bite-size chunks might prove to be somewhat troublesome, even for 
Deinosuchus. Smaller saw-toothed predators might have trouble w/ sauro-hide. No 
doubt those are possibilities, though.

In other words, rather than certain croc-related sauropod death, I think the 
croc/sauropod relationship could be assumed to follow the modern hippo/elephant 
vs croc model, wherein the large herbivores apparently access croc-infested 
swamps, rivers 
arily (any references to the contrary appreciated). 

*herds? gaggles? flocks? I like 'gaggle' relative to sauropods...
**perhaps even a downward-directed modified overhead smash? Again, a maneuver 
that seems certain to cause tail injury in terrestrial environments.