DIGGING DINOSAURS <i> by John Horner & James Gorman (Harper & Row: $8.95, illustrated) </i>

In this unpretentious, first-person account, John Horner describes his discoveries of some of the first fossilized dinosaur eggs, embryos and nests in North America, and offers his theories about dinosaur parental behavior. The arrangement of the nests, the size of the juvenile skeletons and the partially worn surfaces of the hatchlings’ teeth suggest that adult maiasaurs (“good-mother lizards”) protected and nurtured their young much the way some modern birds do.

Horner is careful to separate the facts from his theories--a distinction too many science writers ignore. Numerous excavations have confirmed his belief that many species of dinosaurs built nests near upland streams and lakes; the discovery of large herds of animals near these sites leads him to speculate that the triceratops and its relatives used their elaborate horns and frills the way such modern herd animals as elk use their antlers--for courtship displays and fights over mates, rather than battles with predators. An entertaining example of popular-science writing at its best.