DOES A DINOSAUR ECOLOGIST DO?
by Whit Gibbons
January 13, 2008
is a field of science that relies primarily on the use of fossils to study
relationships among organisms and environments of the past. Paleontologists
interpret clues to reconstruct not only what extinct animals and plants
looked like but also when and where they lived and under what environmental
conditions. But how do we know that our impression of geological times
millions to hundreds of millions of years ago is realistic and not just
comes from a paleontologist, Jim Farlow of Indiana-Purdue University,
who works with dinosaurs. Jim is the lead editor (with coeditor M. K.
Brett-Surman,) of the 1997 book The Complete Dinosaur. I first
knew Jim when he was in the undergraduate research program at the Savannah
River Ecology Laboratory many years ago. We worked on a turtle project
together. Although turtles live a long time, they apparently were not
ancient enough to suit him, so he went on to Yale University to get his
doctorate and become a paleontologist. In one of his scientific papers
he stated that "most aspects of dinosaur biology cannot be observed
directly but must be reconstructed by a variety of often speculative approaches."
sent me a book chapter he wrote about the paleoecology of dinosaurs from
Late Jurassic sediments in Wyoming and adjacent states. The creatures
lived more than 145 million years ago, and more of these Late Jurassic
dinosaur fossils have come from this rock formation than all the rest
of North America. His chapter was on "a speculative look at the paleoecology"
of Camarasaurus and Allosaurus, two of the giant dinosaurs
from the era.
which superficially resembled the brontosaurs most people are familiar
with, was a plant-eating monster as big as a house. In fact, Jim reports
that large individuals would have weighed more than "six big elephants,"
or about 100,000 pounds. Allosaurus, which to most of us would
look like the familiar T. rex, was smaller, but also enormous by
modern standards for a strict carnivore, weighing a little over a ton,
about three times as large as the biggest tigers of today.
the size, the shape, and even the general diet of extinct creatures like
these is usually straightforward because bones and teeth can provide clear
clues to what the animal looked like, how it moved about, and whether
it ate plants, animals, or both. Projecting this initial information into
understanding the general ecology of a species, however, enters the realm
of speculation. This next step for paleodetectives becomes more difficult;
they must understand the ecology of animals today and use educated guesses
about what happened in the past.
from the chapter is an estimate of how much rangeland would have been
necessary to accommodate a grazing Camarasaurus. In fact, Jim gives
two very different estimates because of major uncertainty and disagreement
among paleontologists about whether dinosaurs were "cold-blooded"
like today's reptiles or "warm-blooded" like today's mammals.
Using a basic formula that a typical cow would require 10 to 20 acres
of rangeland, a 50-ton herbivore (or "cowzilla," as Jim Farlow
calls it) would require at least 180 to 360 acres. Even if Camarasaurus
was reptile-like in its eating habits it would need 60 to 120 acres. In
either case, as Jim notes at the end of the section, "dinosaur ranching
would require a substantial investment in real estate."
the paleoecology of Allosaurus is even more speculative because
of mysteries about how often and in what manner these smaller carnivores
actually attacked the gigantic plant eaters. Some authorities suggest
that Allosaurus used its powerful jaws to crush the skulls of bigger
prey. Others speculate that a fast-moving, big-jawed Allosaurus
could take a meal-sized bite out of a slow-moving Camarasaurus
and make a speedy escape. And whether Allosaurus hunted in packs
like lions and wolves or as a solitary stalker like tigers and foxes remains
part of the speculation.
never know for certain about many of the relationships between Late Jurassic
dinosaurs and their environments. But logical, knowledge-based paleosleuthing
can lead to fascinating reconstructions of the past that give us a better
understanding of the world we live in today.
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