Bailiaspis (Trilobita) with English affinities from the Mansilla Formation (Cambrian Series 3 of the Iberian Chains; NE Spain)

Abstract

A new study of the trilobite record in the Mansilla Formation (Iberian Chains, NE Spain) has led to the discovery of the presence of Bailiaspis aff. tuberculata, B. cf. tuberculata and Bailiaspis sp., the first certain citation of this genus in the Mediterranean subprovince. The age of the findings extends from Eccaparadoxides asturianus Zone (upper Leonian) to the lowermost Badulesia tenera Zone (lower Caesaraugustan), which correspond to the upper part of Stage 5 of Cambrian Series 3 and, probably, the lowermost Drumian. The specimens show the cranidial anterior border expanding backwards, forming a plectrum that is characteristic of Bailiaspis. The main characters of the three taxa include: a low convexity of the cranidium, with a very short or absent preglabellar field, and a cranidial sculpture with numerous densely-packed coarse tubercles. The only species that shows these diagnostic characters is Bailiaspis tuberculata from the middle Cambrian of England (Nuneaton, Warwickshire) in horizons inconclusively dated as the Ptychagnostus gibbus Zone (Cambrian Stage 5). This zone has been previously correlated with the upper Leonian and lower Caesaraugustan; thus, the British and Spanish materials are probably of similar age.