. The dinosaur book : the ruling reptiles and their relatives. Dinosaurs; Reptiles, Fossil. period of time—that time when the verte- brates were first invading the land—the amphibians enjoyed a period of terrestrial dominance, a period when they were the masters of the solid earth. This dominance had its beginnings in the first venturings of vertebrates from an aquatic to a terrestrial mode of life, when there was nothing to dispute the claims of the primitive amphibians to the firm ground as a new environment. It had its beginnings with certain Upper Devonian forms such as Ichthijostega (ik-t
. The dinosaur book : the ruling reptiles and their relatives. Dinosaurs; Reptiles, Fossil. period of time—that time when the verte- brates were first invading the land—the amphibians enjoyed a period of terrestrial dominance, a period when they were the masters of the solid earth. This dominance had its beginnings in the first venturings of vertebrates from an aquatic to a terrestrial mode of life, when there was nothing to dispute the claims of the primitive amphibians to the firm ground as a new environment. It had its beginnings with certain Upper Devonian forms such as Ichthijostega (ik-thee-o-STEEG-a), an early amphibian from Greenland that shows in its structure the heritage of its crossop- terygian ancestors. The development of the Amphibia reached its culmination in a line of late Paleozoic and early Mesozoic forms known as labyrinthodonts (lab-i-RiNTH-o-donts), so named from the labyrinth-like internal structure of their teeth—a direct inheritance from their crossopterygian fish ancestors. The labyrinthodont amphibians appeared in Mississippian times, seemingly as direct descendants from the ichthyostegids (see Ichthijostega, above), and they persisted through the Permian period, finally to be- come extinct in the Triassic some 170 million years ago. During this time they de- veloped so that some of them became rather large, the giants of their kind. The evolution of the labyrinthodonts, which is rather interesting, may be outlined briefly as follows. These amphibians began their evolution- ary life in Mississippian and Pennsylvanian times as predominantly water-living forms, having relatively weak limbs. These early labyrinthodonts are known as the Embol- omeri (em-bol-o-mer-ee). From the Em- bolomeri there evolved large, robust, land-living types with strong legs, the Rhachitomi (rak-iT-o-me). The Rhachitomi, living in the Permian period, were among the largest and most powerful of the terrestrial vertebrates, and at first glance it would look as i
Size: 3058px × 817px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublishernewyork, booksubjectreptilesfossil
