Space-filling problems in ramose trepostome bryozoans as exemplified in a giant colony from the Permian of Greenland

Citation
Mm. Key et al., Space-filling problems in ramose trepostome bryozoans as exemplified in a giant colony from the Permian of Greenland, LETHAIA, 34(2), 2001, pp. 125-135
Citations number
54
Categorie Soggetti
Earth Sciences
Journal title
LETHAIA
ISSN journal
00241164 → ACNP
Volume
34
Issue
2
Year of publication
2001
Pages
125 - 135
Database
ISI
SICI code
0024-1164(200106)34:2<125:SPIRTB>2.0.ZU;2-7
Abstract
In order to maintain branch strength and a confluent outer membrane, trepos tome bryozoans had to maintain a continuous colony surface without any stru ctural gaps. This put great constructional demands on colonies with relativ ely thick exozones to fill the exozonal space while preserving a suitable a utozooecial spacing for colony-wide feeding currents. This situation was ma gnified in a giant colony of the trepostome Tabulipora from the Early Permi an Kim Fjelde Fm. in eastern North Greenland. This single branch colony fra gment had a diameter of 37.5 mm. A block was cut out of the 8mm thick exozo ne, and 20 serial tangential peels were made at varying distances from the endozone. Exilazooecial and autozooecial chamber cross-sectional area, pack ing, spacing, and wall thickness were measured in the maculae and intermacu lar areas. Results indicate that, in this colony, volumetric space in the e xozone was occupied by budding new exilazooecia in the maculae and by exozo nal budding: budding of new exilazooecia in the intermacular areas that tra nsform into autozooecia. Exilazooecia played a dominantly space-filling rol e in the maculae as well as helped to maintain regular spacing of autozooec ia in the intermacular areas.