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Re: Giant Cretaceous Crocs Grew More Slowly Than Their Dinosaur Cousins



Humans grow large under the influence of the pituitary gland with GH being
large factor.  Delay of closure of the epiphysis of the long bones is
essential.  What do we know about dinosaur pituitaries and long bone growth?

Best,

Michael Teuton
-----Original Message-----
From: MKIRKALDY@aol.com <MKIRKALDY@aol.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Wednesday, March 17, 1999 10:28 PM
Subject: Giant Cretaceous Crocs Grew More Slowly Than Their Dinosaur Cousins


>>From Business Wire--look for Chris Brochu's name as one of the
>authors of this Nature paper.
>________
>
>"Giant Cretaceous Crocs Grew More Slowly Than Their Dinosaur Cousins"
>
>     STANFORD, Calif.--(BUSINESS WIRE)--March 17, 1999--Imagine a
>crocodile that is more than 30 feet long and weighs about 10,000 pounds.
>
>     Such a creature actually existed 80 million years ago, when dinosaurs
>still ruled the Earth. Paleontologists Gregory Erickson, a postdoctoral
>fellow in mechanical engineering at Stanford University, and Christopher
> A. Brochu at the Field Museum of Natural History in Chicago, have figured
> out how they grew so large.
>
>     The giant crocs, dubbed Deinosuchus, or terror crocodile, needed
>their large stature to compete with the dinosaurs that also tended to be
> extremely large by today's standards. The prehistoric crocs achieved
>their large size by growing at about the same annual rate as modern
>crocodilians but continuing to grow for decades longer, the researchers
> report in the March 18 issue of the journal Nature.
>
>     The researchers studied the annual growth layers in the fossilized
>bony armor plates called scutes from two terror crocs that were
>unearthed in Texas and Montana. By comparing them with the scutes
>of existing crocodilians, the researchers have found that the Deinosuchus
> grew a foot a year, about the same as modern crocodiles, but they
>continued to grow for a much longer period, taking about 35 to 40 years
>to reach adult size. By comparison, today's crocodiles seldom live
>beyond the age of 30 in the wild.
>
>     "This is a much different growth pattern from that found in
dinosaurs,"
>says Erickson. "For example, duckbilled dinosaurs that were about the
>same size as Deinosuchus grew to adult size in only seven to eight years.
>It illustrates ne of the key differences between dinosaurs and other
>reptiles."
>
>     Scutes are bony plates within the skin of crocodiles that serve as
>body armor located on their back and sides. The plates contain a series
>of layers that are laid down annually. The thickness of a given layer is
>proportional to how much the animal grew that year. The scientists
>counted these layers to determine the age of the terror crocs that they
>examined. Then, by taking the relative thickness of the annual layers
> into account, the researchers reconstructed how much each of the
>crocs grew each year.
>
>     They also examined jaws, ribs, vertebrae and other long bones
>on the Deinosuchus skeletons. They found that the giant crocs of
>yesteryear had the same type of slow-growing bones, called lamellar-
>zonal bones, as do today's crocodilians: a finding consistent with the
>slow growth indicated by their analysis of the scutes.
>
>     This slow but steady growth pattern is characteristic of cold-blooded
> creatures like reptiles. At one time, scientists thought dinosaurs grew
>in a similar fashion and reached such large sizes because they continued
>growing for a long time, like the terror croc. In the last 20 years,
however,
> they have found considerable evidence that dinosaurs grew much more
>quickly, at rates comparable to those of large mammals today. This has
>led some paleontologists to argue that dinosaurs must have had a high
>metabolic rate, one comparable to warm-blooded animals. But exactly
>how dinosaurs managed to grow so large and so fast remains a scientific
>mystery.
>___________
>
>Mary
>mkirkaldy@aol.com
>
>
>