PASSAGE 59

　　The first birds appeared during late Jurassic times. These birds are known from four very good skeletons, two incomplete skeletons, and an isolated feather, all from the Solnhofen limestone of Bavaria, Germany. This fine-grained rock, which is extensively quarried for lithographic stone, was evidently deposited in a shallow coral lagoon of a tropical sea, and flying vertebrates occasionally fell into the water and were buried by the fine limy mud, to be preserved with remarkable detail. In this way, the late Jurassic bird skeletons, which have been named Archaeopteryx, were fossilized. And not only were the bones preserved in these skeletons, but also were imprints of the feathers. If the indications of feathers had not been preserved in association with Archaeopteryx, it is likely that these fossils would have been classified among the dinosaurs, for they show numerous theropod characteristics. Archaeopteryx were animals about the size of a crow, with an archeosaurian type of skull, a long neck, a compact body balanced on a pair of strong hind limbs, and a long tail. The forelimbs were enlarged and obviously functioned as wings.

　　Modern birds, who are the descendants of these early birds, are highly organized animals, with a constant body temperature and a very high rate of metabolism. In addition, they are remarkable for having evolved extraordinarily complex behavior patterns such as those of nesting and song, and the habit among many species of making long migrations from one continent to another and back each year.

　　Most birds also have very strong legs, which allow them to run or walk on the ground as well as to fly in the air. Indeed, some of the waterbirds, such as ducks and geese, have the distinction of being able to move around proficiently in the water, on land, and in the air, a range in natural locomotor ability that has never been attained by any other vertebrate.

　　1. According to the author, all of the following evidence relating to the first birds was found EXCEPT

　　(A) nesting materials

　　(B) four skeletons in good condition

　　(C) two fragmented skeletons

　　(D) a single feather

　　下转第二页