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Re: Size of *Neoceratodus africanus* and/or *N. tuberculatus*

You may be right in that larger carnivores can have more diversified
diets. For example, lions eat from grasshopers to giraffe; wolves eat
from bison to mouse: no cat of the size of the domestic one would
possibly have such a range of prey size. Not only in absolute terms,
but there is a paper, I do not remember the title, where it is stated
that the largest carnivores were more likely to kill prey their size
or above than small carnivores (compare the mainly deer-eating tiger
with the mainly mouse-eating cats the size of the domestic one).
Something similar may apply to crocs, where small juveniles do not
seem to prey upon animals close to their size. Conical teeth may
better serve for fish catching, but in crocodiles their presence is
not hindrance for catching and eating tetrapods as well.

However, I do not consider the small spinosaurs to necessarily do not
survive the harsher seasons. After all, cheetahs survive even with
cleptoparasitism from lions and hyenas, and even baboons. Also, at
least some small spinosaurs would have to survive for there to be
giant adult spinosaurs.

2009/3/30 Andrew Simpson <deathspresso@yahoo.com>:
> I might suggest that the young did indeed focus on fish for their main diet 
> but the largest adults turned into greater opportunists over time. If great 
> predators such as this were seasonal hunters and knew when certain lakes 
> dried up where and when then suddenly great size is a huge advantage. The 
> giant can stay and eat the easy to catch fish leaving the smaller Spinosaurs 
> hungry. Sometimes if a lake isn't completely dry but merely shallow or if 
> there is a bottle neck in a river then the largest Spinosaurs, still holding 
> sway the way the biggest meanest bears take the best fishing spots, then 
> their giant well formed fishing jaws would still come in handy for 
> opportunistic fishing.
> During extreme food shortages only the very biggest live.
> Drew Simpson
> --- On Sun, 3/29/09, Raptorial Talon <raptorialtalon@gmail.com> wrote:
>> From: Raptorial Talon <raptorialtalon@gmail.com>
>> Subject: Re: Size of *Neoceratodus africanus* and/or *N. tuberculatus*
>> To: tijawi@yahoo.com
>> Cc: dinosaur@usc.edu
>> Date: Sunday, March 29, 2009, 4:33 PM
>> "I'm only arguing against the hypothesis that
>> spinosaurids were
>> specialized piscivores, or even that fish (including giant
>> lungfish)
>> were even a major part of their diet."
>> I suppose the bottom line is, why were animals as large as
>> spinosaurs
>> possessed of such an unusual head/neck morphology? Pretty
>> much every
>> other group of large theropods has robust skulls adapted to
>> either
>> hacking/slashing or gouging/crushing - features suitable
>> for big
>> predators taking big prey. Yet spinosaurs are virtually
>> antithetical
>> to this arrangement, being large to very large predators
>> that are very
>> ill-suited to taking large prey.
>> I'm not yet convinced that a generic diet of smaller
>> animals
>> (dinosaurs, crocs, lizards, whatever) is sufficient to
>> explain the
>> extreme development of the snout/neck traits seen in
>> spinosaurs.
>> Plenty of other medium-smallish to medium-largish theropods
>> must have
>> had broadly similar diets, yet never specialized in that
>> way. And of
>> course they don't seem to have reached such stupendous
>> proportions on
>> those diets, either. I would strongly suspect that, at the
>> very least,
>> the taking of aquatic prey was an important driver in
>> spinosaur
>> evolution, even if other prey types continued to be
>> imporant food
>> sources.