When Crocodiles Ruled
Dec 8, 2001 thru May 12, 2002
Changing Exhibits Gallery
ruled the world from 200 to 65 million years ago, and we know there are
human beings today. But what
happened after the dinosaurs were gone?
Evidence points to a time
when crocodiles were a dominant life form.
new exhibit by the Science Museums of Minnesota gives a glimpse of the
life, ecosystems, species and climates of 60 million years ago, and unites
research from paleontology digs around the world with rich evidence from
the Wannagan Creek quarry in North Dakota.
Carnegie Museum of Natural History is the first stop for this
exhibit after it premiered at the Science Museum of Minnesota. After Pittsburgh it continues on a
ten-year tour of international museums and cultural sites.
first see dioramas as they step back into the Paleocene era, a time when
North Dakota and the upper Midwest were a lush, warm, sub-tropical swamp.
In this prehistoric world you walk under the branches of cypress, magnolia
and oak, and hear the sounds of frogs and dragonflies. Alligator-like
creatures--champosaurs--are around you.
With their nostrils on the tips of their snouts, they could live
suspended underwater, floating vertically with only their noses exposed.
second part of the exhibit is interactive, with virtual displays and
activities that let you test the bite-force of a crocodile jaw, and follow
a brood of 40 baby crocks from hatching to adulthood, witnessing how only
two survive the perils of predators and the environment. A periscope lets you see what is living
at the bottom of a swampy lake, and you can hear crocodiles'
"voices" reveal their moods, from crabby adults to amorous
adolescents to hungry babies. You
can also see and understand other life forms, from plants and moths to
meat-eating flies and hungry hippos, and you can see the world through a
geologist's eyes. In the theater
area you see how North America changed in 65 million years, and in a Field
Camp you learn how researches live and work as they uncover the past.
When Crocodile Ruled is a fascinating experience for the entire
"Behind the scenes" goes
new paleontology laboratory that opened in November next to the Hall of
Dinosaurs puts on view the laboratory work which has made the museum
popular with visitors, but which until now has largely been restricted to
the lower level of the building.
Paleolab at the entrance to the Hall of Dinosaurs lets you lean against the
32-foot rail that separates visitors from staff preparators, and look
through the glass wall into the lab. The glass controls the dust, noise and
ventilation, but lets you see such apparatus as the huge fume hood used to
work with epoxy and solvents. You can also see the wheeled A-frame lifting
system that moves fossil-bearing rock into working position. In the rear of
the lab is the sand box used in holding pieces of bone together while the
glue resets the bones. All the
systems needed to operate a working laboratory have been installed:
electricity, plumbing, a sink to wash specimens, and a pneumatic line for
being worked on is the removal of a Camarasaurus from its bed of stone, or
matrix. Two computers with touch screens and a streaming video feed bring
you very close to the process of removing these bones from the stone matrix
where they have been imbedded for millions of years. The informational panels give you an
overview of the process and describe the tools used by scientific
staff. The computer also has an
Online Diary of the work--a "progress report" or running archive
of the work being done. Outside the Lab at an Education Desk staff will be
available to answer questions.
Blue Planet, formerly in that space, is now installed on the balcony above
the dinosaurs (second floor), where it continues to be a public resource
about Earth history.
Frog from the deserts of Yemen
You probably don't know Xenopus--an aquatic frog with long toes (and probably webbed
feet)--but it was similar to a popular frog species from the southern
hemisphere commonly sold today in pet shops. Very little has been understood about its
fossil history until scientific preparator Amy Henrici recently documented
the first occurrence of Xenopus
(Anura: Pipidae) on the Arabian Peninsula in the Journal of Paleontology (July 2001). This discovery documents the oldest
occurrence of the species and reveals information about its past
distribution. It also provides
information about the climate of present day Yemen 26 million years ago. The presence of this strictly aquatic
frog in Yemen during the Oligocene era adds to a growing body of evidence
that in the past the Arabian Peninsula was not always covered by a desert,
but probably had tropical forests and savannas.
Ice Mice --the first mammals to migrate from North America to
Europe are found in the Arctic
fossilized teeth of extinct rodents found within the Arctic Circle are the
first documented evidence that mammals originating in North American
crossed to Western Europe over a North Atlantic landmass. Paleontologist
Mary Dawson recently described the evidence in the Canadian Journal of Earth Sciences (July, 2001).
tectonics theory says that the cold, treeless area of today was once part
of a warm climate land bridge connecting North America to Western
Europe. Although there is evidence
that closely related animals existed in both land masses 50 million years
ago when the age of mammals was just beginning, proof that they migrated
over this route was still missing.
The fossils of small rodents, called microparamyines, were unearthed
from Canada’s high Arctic Ellesmere Island.
Situated at about 78 degrees north latitude, the area today is
covered with tundra and ice and is home to polar bears, walruses, seals,
musk oxen, foxes, Arctic wolves, lemmings, and hares, as well as a rich diversity
of bird life. Fifty million years
ago, when these mouse-sized rodents lived, the climate was warm and
temperate, similar to present day South Carolina.
peacock lost its spots--or the loss of sexually selected traits
In many animal species the males have unusual
ornaments and behaviors to increase their attractiveness to females, but
these traits not help their chances for survival. Consider the bright plumage of
peacocks--an attraction to females but an equal signal for predators. A display such as this is thought to be
part of sexual selection, as opposed
to natural selection. Traditionally,
research in sexual selection has focused exclusively on explaining how
these male traits originated, and female preferences for them. John J. Wiens, associate curator of
the section of Amphibians and
Reptiles, has published in Trends in Ecology and Evolution (September
2001) an explanations of why these sexually-selected traits are frequently
By using new phylogenetic trees, Wiens demonstrates
that the loss of these traits occurs
in a wide variety of animals, including insects, fish, birds, reptiles, and
mammals. In some groups losses may
greatly outnumber origins. Wiens
also found that in many groups of organisms, the elaborate traits seen in
males may also evolve in females--as often or more frequently than in
males. Explaining these unusual
findings is an exciting new area for research in sexual selection.