A full-sized Triceratops sculpture at Honolulu Community College Dinosaur Exhibit

It is the curse of paleontologists that they can never attain a definitive understanding of the creatures that so captivate them. A zoologist interested in, say, the predatory behavior of the tiger can go into the field, watch the action unfold and take notes. But answers to even the most basic questions about dinosaurs lie hidden in the silent bones. Undaunted, paleontologists continue to seek out new fossils and reinterpret old evidence to learn what dinosaurs were really like--often with unexpected results.

Some of the most recent work has yielded provocative insights into how dinosaurs reared their young and what dinosaur calls sounded like. Perhaps most startling of all, a Saharan expedition has turned up the remains of a predatory dinosaur that challenges Tyrannosaurus rex as the biggest carnivore ever to tread the earth.

Fragmentary remains of the giant lizard first turned up in northern Africa in 1927. The creature was given the ungainly name Carcharodontosaurus saharicus ("shark-toothed reptile from the Sahara"), but little information could be gleaned from the scattered fossils. Last fall, however, a University of Chicago team led by Paul C. Sereno made an expedition to the Kem Kem region of Morocco and suddenly realized the true enormousness, and enormity, of Carcharodontosaurus. As reported in the May 17 issue of Science, the creature's fossilized skull is 1.6 meters long, even larger than that of T. rex. (Sereno infers that T. rex probably was the taller of the two, but Carcharodontosaurus took the prize for sheer bulk.)

Even aside from its sheer size, Carcharodontosaurus is remarkable in other ways. An examination of its brain case shows a cranial volume of just 205 cubic centimeters, roughly one eighth that of a human and just half that of T. rex. It seems that Carcharodontosaurus was a fighter, not a thinker. Sereno and his collaborators note that Carcharodontosaurus is also of interest for the information it provides about dinosaur evolution. A closely related dinosaur called Gigantosaurus, which also rivaled T. rex in size, lived in Argentina at about the same time. Sereno concludes that there was a rapid evolutionary "radiation" of giant, carnivorous dinosaurs during the late Cretaceous (90 million to 65 million years ago). Those new species were spreading around the globe even as plate tectonics was starting to carry the continents apart.

While some researchers focus on the greatest dinosaur predators, others are intrigued by a more placid but essential aspect of dinosaur studies: How did they rear their young? For years, dinosaurs were popularly portrayed as stupid, sluggish animals. More recently, scientists have begun to recognize that dinosaurs may have been more active and behaviorally complex that previously thought; some researchers now argue that, based on their kinship with birds, dinosaurs may actually have been attentive parents, protecting their eggs and guarding their young.

Last December a group led by Mark A. Norell of the American Museum of Natural History in New York scored a major coup for the supporters of the devoted dinosaur theory. While fossil hunting at the Ukhaa Tolgod site in central Mongolia Norell's team happened across an unprecedented find: the skeleton of an Oviraptor (a relative of the Velociraptors that starred in Jurassic Park) buried atop a nest of dinosaur eggs. In a paper in the December 21/28,1995 issue of Nature, Norell claimed not only that the Oviraptor was tending to its nest but that it did so "in the same posture taken by many living birds when brooding.

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