Taxonomy and palaeoecology of the mollusc Pterotheca from the Ordovician and Silurian of Scotland

A large sample of the bizarre bellerophontiform mollusc Pterotheca from the Upper Llandovery Wether Law Linn Formation in the Scottish Pentland Hills shows marked polymorphic asymmetry. A survival strategy that presents to a predator a mosaic of different search images is suggested to account for the marked variability of the Pterotheca morphology. Multivariate comparisons with Pterotheca mullochensis from the Llandovery of Girvan, P. simplex from the Caradoc of Girvan, P. cf. simplex from the Caradoc of the Northern Belt of the Southern Uplands and P. aff. mullochensis from the Llandovery in the Pentland Hills have helped clarify the morphological differences between these groups. A new species, Pterotheca trimerelloides , is established for the specimens from the Pterotheca beds in the Wether Law Linn Formation. □ Mollusca, Silurian, Ordovician , Pterotheca, taxonomy, palaeoecology.