Trilobite faunas of the Duncannon Group: Caradoc stratigraphy, environments and palaeobiogeography of the Leinster terrane, Ireland

The Burrellian trilobite faunas of the Leinster terrane comprise at least 3 1 species from a spectrum of faunal associations. Strong faunal links with the Anglo-Welsh area confirm the likely close proximity of these parts of A valonia during the mid Caradoc but together with existing magmatic and pala eomagnetic data, the Leinster faunas also indicate that the existing simple structural models of the relationship between these areas need to be reapp raised. Of the 22 identifiable trilobite genera, eight are not known from e quivalent or older horizons in the Anglo-Welsh area and indicate a signific ant link with Scoto-Appalachian faunas on the margins of Laurentia. This co lonization by trilobites of Scoto-Appalachian origin may have been achieved by 'volcanic island hopping' across the shrinking Iapetus Ocean. The Leins ter trilobites are therefore critical in documenting the breakdown of fauna l provincialism and in fingerprinting the faunas and likely palaeogeographi cal setting of terranes now caught up in the Iapetus suture zone to the nor th. Eighteen species are described or discussed in detail including a new s pecies of Ampyxina, A. hibernica sp. nov., a probable new species of Calypt aulax and revision of the M'Coy species Trinodus agnostiformis, Autoloxolic has laxatus, Flexicalymene forcipata and Remopleurides platyceps.