http://worldcat.org/entity/work/id/146543410

Early Ordovician eephalopod fauna from northwestern Australia

A study of the rich Middle and Upper Canadian cephalopod fauna of the Price's Creek area forms the basis of the paper. Preservation in limestone has permitted detailed microscopic study. The time span of the fauna coincides with a critical period of rapid diversification of the nautiloid stock. The 26 new species are distributed amongst 24 genera (14 new) and 12 families. (1 new). It is considered that the multiplicity of generic and familial categories in relation to the number of species is a true reflection of the explosive evolution of the early Ordovician nautiloids. Ten of the genera are found only in North America and Australia, 2 genera are common to Europe and Australia, and 11 genera are indigenous. It is believed from these facts that there was an intermingling of littoral faunas between North America and Western Australia by some route which by-passed eastern Asia. Guyots may have served as an ecological bridge across the Pacific. The terminology of the etosiphuncle is revised. The terms orthochoanitic, suborthochoanitic, and holochoanitic are redefined, and the terms achoanitic, loxochoanitic, hemichoanitic, subholochoanitic, macrochoanitic, and ectosiphuncular suture proposed.

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