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RE: What did Spinosaurus eat? New species of Lepidotes found



Augusto Haro writes:

< -Many of you may want to kill me, but may the size of the sail/hump helped an 
aquatic spinosaur forming a shadow which permitted fishes to approach?>

  In low-angle lighting, sure, but this confines use of the "umbrella" 
technique to morning and evening. Nighttime feeding, will low-angle moonlight 
or the absence of moonlight, would give extreme favoritism to nocturnal 
fishing, if only fish were as active at night (generally) as during the day.

  Now, to play with this hypothesis somewhat:

  Facial anatomy of baryonychines is replete with lots of little pits and pores 
across the maxillae and premaxillae. Ignoring pitting and nutrient foramina as 
links to certain types of dermal tissues (Hieronymus et al., 2009), it was 
suggested that these have much to do with crocodilian integumentary sense 
organs (Jackson et al., 1995), these could be used in allowing a "sit-and-wait" 
behavior (a feature found in some birds but also in some crocodilians). Instead 
of simply floating there and waiting for the prey to come close to this 
"inanimate" log (as in some crocs), the animal may prefer bottom fish and 
probing (again, found in some birds, with similar osteological indicators).
 
Hieronymous, T. I., Witmer, L. M., Tanke, D. H. & Currie, P. J. 2009. The 
facial integument of centrosaurine ceratopsids: Morphological and histological 
correlates of novel skin structures. The Anatomical Record 292:1970-1396.

Jackson, K., Butler, D. G. & Youson, J. H. 1996. Morphology and ultrastructure 
of possible integumentary sense organs in the estuarine crocodile (Crocodylus 
porosus). Journal of Morphology 229(3)315-324.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Thu, 3 Mar 2011 16:31:12 -0300
> From: augustoharo@gmail.com
> To: d_ohmes@yahoo.com
> CC: dinosaur@usc.edu
> Subject: Re: What did Spinosaurus eat? New species of Lepidotes found
>
> 2011/3/3 Don Ohmes :
> >
> > So -- perhaps a look at spinosaurid anatomy from the design perspective of
> > lifting vertically a "wiggly" weight that has been grasped by the jaws would
> > be interesting? As you say, the forces would be transmitted along the long
> > axis of the snout in a straight pull-back of the head, and this is true even
> > when the front limbs are not actively engaged.
> >
> > It would seem reasonable to assume (as a working hypothesis) that any fish
> > too big to swallow whole, but small enough to be lifted would be transported
> > to shore for processing -- much as river otters do -- and that processing
> > would not be extremely demanding, in itself.
> >
> Looks like a good idea, Don. Perhaps in this spinosaurids, with their
> relatively taller than wide snout, may surpass crocodilians, if the
> fish was carried with the skull oriented horizontally (more resistant
> the skull would be, with heavier fishes, if these were carried with
> the skull held vertically, as I suppose you are talking). But, is
> there evidence of this transport behaviour in fishers with long, and
> presumably more fragile, snouts?
>
> Other random thoughts
>
> -Sorry, Tim, but I erred when saying that spinosaurids have taller
> than wide snouts. This is true for baryonychines, but according to Dal
> Sasso et al. 2005, not of Spinosaurus, at least at the upper jaw.
> However, the lower jaw seems to be taller than wide, especially
> caudalwards.
>
> Now sorry again Tim, but I will play Devil's advocate with the
> longirostrine fish-eating bird model:
>
> -I think that the bird models have some adventages. First, it seems
> spinosaurids were no specialized swimmers, as far as can be seen from
> baryonychines, and would more resemble wading birds in locomotor style
> (although another problem: their limb proportions more closely
> resemble the short-limbed paddling birds!). Spinosaurines may have
> better swimming abilities (unknown because of the lack of limbs), but
> parsimony and the sail/hump do not suggest so. Second, the short
> secondary palate found in spinosaurs is found in a more extended
> fashion not only in crocodiles, but also in many long-beaked water
> birds, as the Mycteria skull I have, whose tip may have been subjected
> with similar bending stresses to those described by Rayfield et al. in
> the case of Baryonyx and the gavial by dealing with similar prey
> items. Third, the longer neck may help with a source of precision
> crocs seem not to have. Four, the back of the jaw apparently permiting
> to increase the gape (if I got well David Marjanovic's mention on
> this).
>
> -The Rayfield et al's 2007 paper does not make comparison with
> fish-eating longirostrine birds, just with tall-snouted theropods,
> alligators, and gavials. Thus, on the basis of their work, I would not
> say that longirostrine birds are worst analogs than gavials.
>
> -Many of you may want to kill me, but may the size of the sail/hump
> helped an aquatic spinosaur forming a shadow which permitted fishes to
> approach?
>
> -Regarding the Bailey's hump hypothesis... May the large size alone
> and the peril of isometry for the same function explain the robustness
> of the spines of sailed dinosaurs relative to those of large non
> therapsid synapsids? One may think that, if supporting these dinosaurs
> were humped, that the spines would be much stouter than (instead of
> similar to) those in the humped mammals with which Bailey compared,
> accepting that isometry is bad idea in differently sized animals.
>
> -If Spinosaurus had a weak bite as here hypothesized he may had as
> much chances against a Tyrannosaurus as a greyhound has against a
> pitbull even when the former is slightly larger than the latter!
>
> Cheers,
>
> Augusto