Biological affinity, phenotypic variation and palaeoecology of Tetradium Dana, 1846
Version of Record online: 11 MAR 2009
© 2009 The Author, Journal compilation © 2009 The Lethaia Foundation
Volume 42, Issue 4, pages 383–392, December 2009
How to Cite
STEELE-PETROVICH, H. M. (2009), Biological affinity, phenotypic variation and palaeoecology of Tetradium Dana, 1846. Lethaia, 42: 383–392. doi: 10.1111/j.1502-3931.2009.00151.x
- Issue online: 10 NOV 2009
- Version of Record online: 11 MAR 2009
- manuscript received on 27/05/2007; manuscript accepted on 29/09/2008.
- phenotypic variation;
Comparisons of morphologies and modes of life of the Ordovician fossil Tetradium Dana, 1846, with chaetetid sponges, tabulate corals, and Recent rhodophytes show that several defining Tetradium characteristics are incompatible with its chaetetid and tabulate classifications. All Tetradium characteristics fit a rhodophyte identification, however, as a calcified uniaxial corticated florideophyte. It is argued from functional morphology that the fundamental subsquare cross-section of the Tetradium tube is an adaptation for close packing, which implies that the basic growth form is compact and should have developed where conditions were optimal. More open forms are derived from it and probably occupied less-favourable environments.
Palaeoecological studies from the Ottawa Valley, Canada, show that the Tetradium growth form is correlated with environmental stress and became more open as salinity increased: i.e. the compact T. fibratum form lived in normal marine conditions, radiating bundles of T. cellulosum tubes in low to middle hypersalinity and single T. syringoporoides tubes in high hypersalinity. Different Tetradium growth forms from the study area are phenotypic variants of a single species, rather than different species and genera. Therefore, classifications that divide Tetradium into different species and genera based only on growth form have no biological basis. There is little evidence of interspecific interactions with Tetradium.