A new species of Buchia (Bivalvia: Buchiidae) from British Columbia, Canada, with an analysis of buchiid bipolarity

Abstract

Critical reinvestigation of the bivalve Buchia cf. blanfordiana Jeletzky, 1965 from the Upper Jurassic of western British Columbia indicates that it is morphologically distinct from B. blanfordiana Stoliczka, 1866 of the Indo-Pacific region. We analyzed collections from relatively coeval sections containing multiple buchiid species from the Northern and Southern Hemispheres and used ten morphological characters to describe Buchia shell shape and size. We tested for taxonomic differences on left and right valves using a traditional morphometric approach with both linear and angular measurements and Fourier (outline) analyses. Phenetic discrimination revealed considerable overlap in the morphospace, but high classification rates between the two groups when compared with a step-wise discriminant analysis. This study supports the retention of the Indo-Pacific genera Australobuchia Zakharov, 1981 and Malayomaorica Jeletzky, 1963 and confirms that Buchia (=Australobuchia) blanfordiana is restricted to the Southern Hemisphere. Consequently, we propose the new name Buchia columbiana n. sp. for material assigned to Buchia cf. blanfordiana Jeletzky, 1965. Our results have implications for bipolarity and migration of the genus Buchia, supporting previous suggestions that buchiids formerly identified as Buchia from the Southern Hemisphere should be grouped as a separate genus.