Bringing Fossils to Life by Donald R

Author:Donald R.
Language: eng
Format: epub
Tags: -
Publisher: Columbia University Press
Published: 2013-10-08T04:00:00+00:00

FIGURE 14.19 Structural features of the trepostome Dekayella. (A) Perspective drawing. (B) Longitudinal section. (C) Transverse section. (Modified from Moore et al., 1953.)

Order Cryptostomata (Ordovician–Permian; about 90 genera)

Cryptostomes (“hidden mouth” in Greek, in reference to how the true aperture is hidden beneath a vestibule) are the other dominant group of early Paleozoic bryozoans, radiating in huge numbers before the Late Ordovician extinctions, and then persisting through the rest of the Paleozoic before final extinction at the end of the Permian. They are distinguished by their short autopores, with a wider opening (vestibule) separated from the narrower inner zooecium by a hemiseptum (fig. 14.20). Some have abundant acanthopores of two sizes (megacanthopores and micracanthopores); others do not have abundant mesopores or acanthopores, but instead have large masses of common calcified skeletal tissue (a coenosteum, something we have already seen in some corals).

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.