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



I won't comment yet on the bulk of this, as it impugns on my right to be snotty 
when I reply [at length - oy!] on my blog (the realm of escape to which I go 
when distressed at being upstaged by Haro and Williams when they are right and 
say things better than I do).

  However, Augusto writes something that allows me some freeform speculation, 
and that's always fun:

<What if in the Mesozoic there was the possibility of eating 4 m. crocodiles 
for a living, a niche we do not find today because carnivorous mammals are not 
large enough?>

  Most carnivores should have no difficulty processing the carcass of such an 
animal as a croc at 4 m, close to its own size perhaps. This likely happened 
for a lot of biotas from the Chinle to the Hell Creek. What is speculated seems 
to be the potential to _hunt_ crocodiles, and in that, our minds turn to 
spinosaurs plunging into rivers and lakes and surfing to find those delectable 
*Stomatosuchus* and *Sarcosuchus* and *Bernissartia*. Augusto is right, no 
animal selectively goes after crocs today, largely because they'd be supremely 
stupid to enter the water where the croc is king. Humans know this, and some of 
us DO hunt these for a living. I can't help but be reminded of one of my 
favorite movies for lampshading this, _Lake Placid_, repeatedly. How often need 
you be reminded that what dwells below wants to eat you?

  But in the era of tyrannosaurs and spinosaurs, there are more than aquatic 
crocs, and in this case, terrestrial forms both large and small were prevalent, 
and I would think just as likely to be prey (eventually) as any other theropod 
in the realm of the largest carnivore around.

  To answer the question then, "yes."

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: Tue, 1 Mar 2011 01:51:13 -0300
> From: augustoharo@gmail.com
> To: tijawi@gmail.com
> CC: dinosaur@usc.edu
> Subject: Re: What did Spinosaurus eat? New species of Lepidotes found
>
> 2011/2/28 Tim Williams :
> >
> > The closest analog or spinosaurs among modern crocodylians appears to
> > be the gavial (or gharial, _Gavialis gangeticus_).  The gavial is the
> > closest analog both structurally and biomechanically (Rayfield et al.,
> > 2007; JVP 27: 892-901).  The gavial is a longirostrine crocodilian in
> > which the rostrum ends in a terminal 'rosette' - as in spinosaurs.
> > The thing is, in order to catch fish, the gavial favors lateral
> > sweeping strikes with its rostrum.  In fact, the longirostrine snout
> > appears to be specialized for this kind of predation: rapid movement
> > through water by lateral flexion, with the prey caught at the end of
> > the rostrum (McHenry et al., 2006; Anat. Rec. 288A: 827-849).  If this
> > also applied to spinosaurs, this is inconsistent with a heron analog
> > for spinosaurs, because herons employ stabbing motions with their
> > rostrum to procure fish.
> > Further, the gavial analog suggests that the spinosaur rostrum was
> > already immersed in water when the predatory strike is launched.  So
> > the spinosaur rostrum wasn't above or by the water surface, but below
> > it.  This makes sense if one of the targeted prey items for African
> > spinosaurs were giant lungfish, which (going by the behavior of modern
> > _Neoceratodus_) spend most of their time lurking on the bottom of
> > rivers.
> >
> This hypothesis bears more data behind, and should be thus the most
> respected, but, it seems to me that the point by Jaime regarding the
> irregular tooth file arrangement seems to suggest some similarities
> the predatory habits of Crocodylus, although with less bite force
> (which would resemble more the gharial).
> Also departing from the gharial, the lower jaw does not seem to be
> much more dorsoventrally thin than in other dinosaurs, contrasting
> with gharials, nor is the rosette so much widened (a relatively not
> so-widened rosette is also present in Crocodylus).
> Long snouts seem to permit a faster grip of prey, because an angularly
> similar lateral head movement relative to the neck would move the tip
> a longer distance, and may be an advantage also at land (perhaps this
> explains they being able to capture presumably fast prey as
> pterosaurs, if not slow or already dead before capture; now I sin of
> spreading rumor, but I heard of storks being able to capture
> passeriforms).
> The hook at the tip may help retaining the prey which tries to escape
> away from the predator, or getting a piece out of it, as in the case
> of carcasses for the birds Jaime mentioned. Anyway, this hook seems to
> depart from the gharial condition.
> The irregular tooth row implies a longer alveolar border of the jaw (I
> was to say that this suggests more teeth and thus better grasp, but I
> am not sure), with which perhaps to grasp prey more securely.
> Alternatively, it may permit a small group of teeth at the tip of each
> "mount" in the irregularity to put more pressure (and thus to
> penetrate more) in the food item, because teeth closer to the
> "valleys" would contact the prey in a lesser degree.
> As far as I know, Crocodylus for the most rely on fishes and other
> relatively small aquatic animals as frogs, aquatic snakes and crabs.
> Perhaps the gharial is more specialized for fast, small fishes, while
> Crocodylus hunts a larger variety of fishes, with possibilities for
> swallowing larger fishes in the wider jaw. The jaw articular mechanics
> indicated by David Marjanovic may suggest swallowing of relatively
> larger fishes.
> May spinosaurs have been something more similar to a mix of the
> gharial, Crocodylus, and heron (at least for the jaw articular
> mechanism related to large-prey swallowing)? To me, Proterosuchus and
> phytosaurs look like better candidates for similarity in habits, but
> they are extinct.
>
> Regarding Majungasaurus, Lucas Fiorelli recently described several
> bite marks in a peirosaurid crocodile 3-4 mts. long which he
> attributes to large theropods, suggesting as culprits either
> charcharodontosaurids or abelisaurs
> (http://crilar-conicet.academia.edu/LucasFiorelli/Papers/352183/Predation_Bite-Marks_on_a_Peirosaurid_Crocodyliform_From_the_Upper_Cretaceous_of_Neuquen_Province_Argentina).
> What if in the Mesozoic there was the possibility of eating 4 m.
> crocodiles for a living, a niche we do not find today because
> carnivorous mammals are not large enough? Eating crocodiles would be
> easier if there were no larger crocodilian species (Sarcosuchus or
> Deinosuchus) around. Coping with he hard hide of the crocodiles may
> relate to the relatively rigid skull of Majungasaurus. Catching a
> crocodile seems to require less reflexes than catching faster swimmers
> as fishes. This may need to check if there was a large crocodilian
> population... the hypothesis may imply that the Majungasaurus teeth
> were prone to break up often if hitting osteoderms, and this may be
> tested checking the wear in Majungasaurus' teeth compared with other
> carnivores supected of eating more tender stuff.