12 Reefs and Shallow Seas: Advances in High-Resolution Stratigraphy and Paleontology in Silurian-Ordovician Rocks of North America

Monday, 18 April 2016
1:30 PM - 5:30 PM
Illinois Ballroom C

ONTOGENY AND REPRODUCTIVE FUNCTIONAL MORPHOLOGY OF A NEW DASYCLADALEAN ALGA (CHLOROPHYTA) FROM THE SILURIAN ERAMOSA LAGERSTÄTTE OF ONTARIO, CANADA

Paper number: 12-9
Program: Theme Sessions
Time: 4:10 PM – 4:30 PM

Authors

Abstract

The thallus of a new genus and species of noncalcified macroalga from the mid-Silurian Eramosa Lagerstätte of Ontario, Canada, comprises a narrow main axis with unbranched laterals in whorls (euspondyl). Laterals of two types, (1) hairlike with tapered ends (trichophore) and (2) cylindrical with expanded, ball-shaped terminations (phloiophore), are segregated by type into alternating whorls distributed along much of the length of the main axis. The combination of thallus architecture and lateral morphology characteristic of this alga is unique to the extant green algal order Dasycladales and, in this context, morphologic differences between specimens can be readily interpreted as ontogenetic stages similar to those displayed by the extant dasycladalean Halicoryne. Biophysical modeling of reproductive functional morphology for living dasycladalean algae, when applied to the new alga indicates that the ball-shaped terminations of the phloiophore laterals are not homologous with gametophores, and that reproduction was instead either endospore or cladospore, details of the ontogenetic sequence pointing to the latter. Production of two types of laterals in alternating whorls (= cyclical heterocladous development) for this alga adds to the list of developmental innovation achieved by dasycladalean algae during a significant burst of evolutionary activity that unfolded between the Middle Ordovician and Late Silurian.

Geological Society of America Abstracts with Programs. Vol. 48, No. 5

doi: 10.1130/abs/2016NC-275148

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.