Search results for "Mouth angle"

What a New Model of Skeletal Homologies Tells Us About Asteroid Evolution1

2000

The Extraxial-Axial Theory (EAT) is applied to the body wall homologies of asteroids. Attempts to characterize major plate systems of asteroids as axial or extraxial, particularly those that are highly organized into series, can be problematic. However, the Optical Plate Rule (OPR) is instrumental in establishing that ambulacrals and terminals are axial. It is equally clear that the region aboral to the marginal frame is a part of the perforate extraxial body wall (with the possible exception of the centrodorsal, which is likely imperforate extraxial). Previously established EAT criteria, particularly those strongly rooted in the embryologically expressed boundary between axial and extraxia…