Variation in the loops of two recent species of Liothyrella (Brachiopoda; Terebratuloidea) from New Zealand and South Orkney Islands

Generic distinctions within the short-looped brachiopod Suborder Terebratulidina are based principally on differences in the size, shape and proportions of the loops and cardinalla. Classification of fossil terebratulidines has traditionally been based upon a narrow view of the variation present in the internal structures. The level of variation present in the loops of two clearly differentiated allopatric species of Recent brachiopods, Liothyrella neozelanica Thomson from New Zealand, and Liothyrella uva (Broderip) from South Orkney Islands is demonstrated quantitatively to be large and broadly overlapping, with considerable variation in every measured parameter. We therefore suggest that a re-evaluation of generic and specific boundaries for short-looped brachiopods is urgently needed.