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I’d like to be able to make some kind of Berkeley connection with the California Academy of Sciences’ new exhibit, “Dinosaurs: Ancient Fossils, New Discoveries.” But geology is against me. There was no there here during the dinosaur era: the coast of North America ended about where the Sierra Nevada is now. Westward, there were volcanic island arcs, ancient equivalents of Japan or the Philippines, then open ocean.
“People ask where the California dinosaurs are,” says Peter Roopnarine, Assistant Curator of Invertebrate Zoology and Geology, who studies prehistoric mass extinctions. “We’ve only found bits of 12 individuals.”
Their fragmentary remains had been washed into the Jurassic or Cretaceous seas, entombed in marine deposits that make up the bedrock of the Central Valley and the Coast Ranges.
Giant reptiles of other kinds abounded in those warm waters, feeding on fish, squidlike creatures, and each other: fish-shaped ichthyosaurs, lizardlike mosasaurs, long-necked plesiosaurs (the classic Loch Ness Monster types), and enormous sea turtles. But those beasts just don’t have that dinosaur charisma. So the Academy’s exhibit, a collaboration with the American Museum of Natural History and Chicago’s Field Museum, focuses on the land-dwelling saurians we all know and love.
It’s an effective mixture of old bones (or their replicas) and state-of-the-art technology.
“The exhibit was designed to highlight new aspects of dinosaur paleontology,” Roopnarine explains. “There have been changes in the way we think about dinosaurs. They were faster and more powerful than we thought, and their behavior was more complex.”
So there’s an emphasis on biomechanics that was lacking in older exhibits. Along with the obligatory Tyrannosaurus rex skeleton, there’s a one-seventh scale model that demonstrates how T. rex would have walked. The life-sized fiberglass-and-steel Apatosaurus (the dinosaur formerly known as Brontosaurus) skeleton was generated from a digital model; on the wall behind it, computer animation builds the behemoth’s neck, from the vertebrae through the layers of muscle.
As for behavior, the trophy wall of horned-dinosaur skulls frames a discussion of what those nose spikes and neck shields were for: protection against predators, or competition within the species as in modern horned mammals? Roopnarine speculates it was a bit of both.
The section on trace fossils spotlights a replica of a fossil trackway from Davenport Ranch in Texas: a herd of sauropods, adults and young traveling together, left their footprints on an ancient floodplain, as did the bipedal carnivores that stalked them.
Surprisingly, there’s not much in the exhibit about the evidence that some dinosaurs—like the duckbill Maiasaura, the “good mother lizard”—cared for their young, as living alligators, crocodiles, and birds do. And I didn’t see any coprolites: fossilized dino dung can be very informative.
Less spectacular than the monstrous bones, but fascinating to any dinosaur aficionado, is a slice of grayish rock from New Jersey that includes a layer marking the slice of geological time when the dinosaurs, and a host of other species, went extinct: the Cretaceous-Tertiary boundary.
Here, come to think of it, is the Berkeley connection: it was UC’s Luis and Walter Alvarez who first made the case for an extraterrestrial impact as the agent of extinction. There’s compelling physical evidence for this, but massive volcanic eruptions and changes in sea level may also have played a part; the exhibit explains the competing hypotheses. Roopnarine says scientists disagree as to whether dinosaurs were already in decline when the asteroid or comet struck, but that recent research supports continued diversity right up to the end.
My personal favorite, though, was the lovingly detailed reconstruction of a swampy forest in what is now China’s Liaoning Province about 130 million years ago. It’s an old-fashioned diorama, with reconstructions of flora (ginkgo trees, horsetails, giant fernlike plants) and fauna (insects, frogs and salamanders, unprepossessing early mammals, the largest about badger-sized).
And of course dinosaurs, and birds. It would be reasonable to say and/or birds: “Modern birds are firmly nested within the dinosaurs,” says Roopnarine.
Birds are the only dinosaur lineage that survived the Great Dying. Feathers apparently evolved some 150 million years ago, long before flight: they may have functioned as insulation or in courtship displays. Even T. rex may have been downy in its youth. The avian dinosaurs of Liaoning were weird and wonderful creatures: four-winged gliders, terrestrial insect-catchers, a long-clawed planteater that had evolved from carnivorous ancestors (as, millions of years later, did the giant panda).
There’s something here to appeal to dinophiles of any age. The exhibit, at the Academy’s temporary quarters at 875 Howard St. in San Francisco, runs through Feb. 4, 2007.
For information, visit the Academy’s website: http://calacademy.org. The American Museum of Natural History’s site (www.naturalhistory.com) has much more detail, including interviews with Mark Norrell (who has done field work in Liaoning), Niles Eldredge (of punctuated equilibrium fame), and other paleontological luminaries.
Photograph by Ron Sullivan
A scale model in the exhibit at the Academy of Sciences demonstrates the tyrannosaur’s gait.