Early Silurian (Llandovery) encrinurine trilobites from the Mackenzie Mountains, Canada
Llandovery Encrinurinae from the Whittaker Formation in the central Mackenzie Mountains include Cromus canorus n. sp., Distyrax cooperi n. sp., Distyrax n. sp. A, Perryus bartletti n. sp., and Encrinurus n. sp. Additional diversity of Distyrax Lane, 1988, demands a revised generic diagnosis with emp...
| Published in: | Journal of Paleontology |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
1992
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0022336000033485 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000033485 |
| Summary: | Llandovery Encrinurinae from the Whittaker Formation in the central Mackenzie Mountains include Cromus canorus n. sp., Distyrax cooperi n. sp., Distyrax n. sp. A, Perryus bartletti n. sp., and Encrinurus n. sp. Additional diversity of Distyrax Lane, 1988, demands a revised generic diagnosis with emphasis on pygidial homologies; new species are described from the Llandovery of Newfoundland and Ontario. Several characters suggest a sister group relationship between Distyrax and Encrinurus s.s. A lectotype is designated for the Llandovery species Encrinurus elegantulus Billings, 1866. Cromus canorus n. sp. is closely allied to other northern Laurentian Llandovery species. Synapomorphies of Cromus are inclusive for Encrinuraspis as revised by Snajdr, 1985. The long stratigraphic range and morphological conservatism of Cromus are correlated with occurrence in distal mudstone facies. Ontogenetic material for Distyrax n. sp. A, Cromus canorus , and Perryus bartletti is described, with consideration of librigenal spine homologies in Encrinurinae. Humaencrinuroides Nan, 1985, is a pliomerid of the new subfamily Quinquecostinae, and not a subgenus of Encrinuroides Reed. |
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