The Ordovician trilobite Atractopyge from Wales and northern EnglandStaff: R.M. Owens
Of the trilobite specimens illustrated by the Welsh scientist Edward Lhuyd in 1698, only one is known to be extant, and was identified a few decades ago in the collections of the University Museum of Natural History, Oxford. It is a cranidium from Ordovician rocks of the Llandeilo area, almost certainly from Crûg Quarry, and is now classified in the genus Atractopyge. This is a relatively common trilobite in rocks belonging to the Caradoc and Ashgill series in Wales, and in the latter in northern England, but only in certain facies, where it is associated with a suite of brachiopods that typify the Nicolella community. It is surprisingly absent in the Gelli-grîn Calcareous Ash Formation of the Bala district, from which large collections of fossils have been made, including numerous brachiopods of the Nicolella community, but is present in coeval strata in the Berwyn Hills and in Snowdonia. The way in which it is distributed may be linked to the inferred life habits of this trilobite, which probably spent much of the time semi-submerged in soft sediments on the sea-bed. It is possible that the substrate of the Gelli-grîn Calcareous Ashes was simply too hard for it to burrow into, hence its absence from this formation.