Clinal variation, episodic evolution, and possible parapatric speciation: the trilobite Flexicalymene senaria along an Ordovician depth gradient
Version of Record online: 9 OCT 2007
Volume 15, Issue 4, pages 325–341, November 1982
How to Cite
CISNE, J. L., CHANDLEE, G. O., RABE, B. D. and COHEN, J. A. (1982), Clinal variation, episodic evolution, and possible parapatric speciation: the trilobite Flexicalymene senaria along an Ordovician depth gradient. Lethaia, 15: 325–341. doi: 10.1111/j.1502-3931.1982.tb01697.x
- Issue online: 9 OCT 2007
- Version of Record online: 9 OCT 2007
Pygidial segmentation in the trilobite Flexicalymene senaria changes with time (as measured in relation to bentonite beds) and with depth (as measured along downslopc transects along bentomtc beds and as measured by gradient analysis of fossil assemblages) along a ‘fossil’ depth gradient in the Middle Ordovician Trenton Group in central New York State. The pattern of strictly temporal change resembles a ‘punctuation’ between ‘equilibria’. This evolutionary episode, a 106 year interval of continuous change, may represent parapatric speciation. The clinal gradient is strongest during this episode and is weak or not apparent outside it. Strictly temporal change takes place by way of temporal change in the cline's shape. □Evolution, geographic variation and dines, gradient analysis. Middle Ordovician, morphometry, speciation, Trilobita.