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Re: Crocodile program on Discovery channel

On Fri, 13 Oct 1995, Achut Reddy wrote:

> Jerry D. Harris writes:
> > Yes, crocs were around before
> > the dinos (although the eusuchians didn't pop up 'til what, the
> > Cretaceous), but in the sense of "what animal filled most of the global
> > niches of big terrestrial reptile after the dinosaurs?," crocs fit the bill
> > nicely.  (coupled, methinks, with big birds!)
> But the crocs _didn't_ fill most of the global niches.
> They are found only in and around rivers.  They certainly did
> not have anywhere near the range that the dinos did.
> In the Tertiary, mammals and birds filled more niches 
> than crocs.

        The believe that crocs have changed little since  first appearing 
in the late Triassic over 225 mya (_around_ the same time as the earliest 
dinosaurs :o)) is a common one.  Living crocodylians (alligators, 
crocodiles, and gavials), while confirming to the standard eusuchian base 
plan, give no hint of the vast range of diversity of those now extinct.  
Indeed, the niche-filling capabilities of crocs should not be 
underestimated. Early crocodylomorphs such as sphenosuchians and 
protosuchians appear to have been gracile, quick-moving terrestrial 
predators.  It wasn't until the Middle Jurassic that crocodylomorphs 
adopted the amphibious mode of life they came to dominate so successfully.
However, these taxa, known as mesoeucrocodylians, in addition to the 
classic amphibious ambush predator, filled many roles. Thallatosuchians 
successfully adapted to marine life, evolving flippers and a heterocercal 
tail. Hsisosuchians and sebecids seem to have been terrestrial, evolving 
laterally compressed snouts and trechant, serrate teeth like those of 
carnivorous dinosaurs - traits also found in several eusuchian taxa which 
may also have been terrestrial (for example, pristichampsines and 
mekosuchins).  The relatively short-snouted notosuchids may also have 
been terrestrial.  The blunt, intricately fluted teeth of uruguaysuchians 
and some notosuchids were very similar to those of herbiverous dinosaurs 
and lizards, suggesting these animals may also have been herbiverous.  
        It's just a shame things like this aren't around today :o(


Steve Salisbury
Vertebrate Palaeontology Laboratory
School of Biological Sciences
University of NSW