IT'S A CROC

[GSP1954@aol.com]

Because there as been a discussion about deinosuschians versus tyrannosaurs,
and the weight of early whales, this might be of interest. 

These days the biggest freshwater Austalo-Asian salt water and S American
Orinoco crocs reach something over 20 ft and about a tonne. Claims of 30
footers that would weigh about 4 tonnes are certainly excessive. 

It has been claimed over the years that some of the huge, extinct freshwater
crocodilians reached lengthes of 40 to 60 ft, and weights of 10 to 30 tonnes.
If so these monsters would greatly exceed known theropods, and rival whales
and the biggest sharks. This sounds fishy (pun intended), it is hard to see
how such colossi would fit into streams, ponds, and most rivers and lakes,
much less find enough food. 

There are 


no good skeletons that support these estimates, skull material is the basis
for them. There is very good data correlating dorsal midline skull length,
total length and body mass in large alligators and salt water crocs. The
correlation is highly consistent, in both total length is about 7.2 times
longer than the top of the head. The most complete big croc skull belongs to
the extinct S American caiman Purussaurus. Its skull is just over four feet
long on the top. So its body should have been just about 30 ft long, and it
should have weighed some 4 tonnes. A complete, bigger lower jaw of the same
beast suggests an individual that weighed about 5 tonnes. Of course these
estimates are subject to error, but estimates of 45 ft and 18 tonnes (that
have found there way into the Guinness book of records) are implausible. 

Wann Langston tells me that Deinosuchus skulls were probably no bigger than
those of Purussaurus -
, the supposedly longer AMNH skull was inaccurate and is no longer on
display. The fragmentary gavial Rhamphosuchus was estimated to be 60 ft long,
but the long slender snout is probably misleading. I suspect its body was not
much longer than Purussaurus.   

Therefore, ancient crocs were big, but not that big. In fact, they seem to
have been about the size of the biggest and unrealistic claims for living
crocodilians. 

On a related matter I've photographed the mounted skeleton of Giganotosaurus
at the Acad Nat Sci in Philadelphia. If the slides came out will restore the
skeleton and see how much it weighed
 compared to Tyrannosaurus. 

GSPaul