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ISBN: 0-919216-75-7

ISSN: 0821-7556

The scanning electron microscope study of uncompressed and beautifully preserved graptolites (many illustrated in stereo-pairs) from the lundgreni Biozone (lower Homerian, Upper Wenlock) of Cornwallis Island has led to the recognition of a richly diverse lundgreni Biozone, pre-extinction fauna. The study reveals the presence of at least 19 species of monograptids and cyrtograptids, and a few species of dendroids and tuboids. Two new species of monograptids, and three new retiolitids (including a new genus and species) are described. The total Canadian Arctic biozonal diversity of graptoloids is the highest known in the world. But at the end of the lower Homerian, the lundgreni extinction event led to the demise of almost all graptolite taxa and morphotypes. From the Arctic diversity viewpoint alone, 96% of the monograptids and cyrtograptids, and 93% of the retiolitids disappeared during the extinction event, making it the most severe graptolite extinction event of the entire Silurian.

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Joint Committee on Paleontological Monographs

Softcover 61 pp., 19 pls. (2001)