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Indications of polypides in feeding zooids and polymorphs in Lower Paleozoic trepostomata (Bryozoa)

Published online by Cambridge University Press:  14 July 2015

Richard S. Boardman
Richard S. Boardman*
Affiliation:
Curator Emeritus, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560
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Abstract

Delicate symmetrical structures in living chambers of autozooecia of some lower Paleozoic species of the order Trepostomata have been interpreted as indications of polypides with little further elaboration. Applications of the anatomy, mode of skeletal growth, and functional requirements basic to living species permit recognition of a few organs of these partially preserved polypides, their functions, and their relationships to enclosing skeletons. Only one basic polypide anatomy is indicated in lower Paleozoic trepostome species, in contrast to the wide diversity of polypide anatomy and their lack of correlation with skeletal characteristics in living stenolaemates. In general, the longer the evolutionary history, the greater the diversity of skeletal morphology in stenolaemates. Apparently, polypide diversity and lack of correlation with skeletal morphology also have increased over time.

The complex skeletal septa in autozooecial apertures of the lower Paleozoic trepostome Hallopora have been interpreted as reflecting an organ of full-sized feeding polypides. Applications of the basic biological concepts of living species suggest that the septa provided reduced skeletal apertures to fit smaller polypides of polymorphs that secondarily occupied the living chambers of full-sized degenerated feeding polypides.

Type
Research Article
Information
Journal of Paleontology , Volume 73 , Issue 5 , September 1999 , pp. 803 - 815
Copyright
Copyright © The Paleontological Society 

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