Trilobites of the family Paradoxididae occur widespread in theMiddle Cambrian of the palaeo-continents Baltica, Avalonia,Bohemia, peri-Gondwana (Spain, Morocco, Turkey) andSiberia. Traditionally, they have been used to define zones andstages in local stratigraphy. In Scandinavia Baltoparadoxides oelandicus, Paradoxides paradoxissimus and P. forchhammeri continue to define the superzones (stages) of the Middle Cambrian, whereas for higher stratigraphical resolution the earlier polymerid trilobite zones have been abandoned in favour of Westergård’s (1946) agnostid zonation; this zonation has been subsequently adopted worldwide. Agnostids are more common than paradoxidids, generally well preserved and their worldwide distribution pattern makes them suitable for intercontinental correlation. Members of the Paradoxididae, onthe other hand, may have a long stratigraphical range, severalspecies are only known from fragmentary material, and the taxatend to be endemic.To contrast this, in Sweden, ‘Paradoxides’ species of the B.oelandicus Superzone are regularly found as complete,well-preserved specimens within the so-called orsten (stinkstone)lenses and are treasured among trilobite collectors fortheir beauty. Middle Cambrian paradoxidid species weredescribed already by the early pioneers of the 19th century(Angelin, Brøgger, Gro¨nwall, Linnarsson, Sjo¨gren, Wahlenbergand Wiman). Additional species of the B. oelandicus SuperzonefromO¨ land were described and published by Westerga°rd (1936).Since then, however, Scandinavian species have received littletaxonomical attention, and only one new species, Hydrocephalusvikensis Rushton and Weidner, 2007, has been described (Fig. 1).In 2003, a ‘Paradoxides’ project was launched. Several newspecies of Acadoparadoxides, Eccaparadoxides and Hydrocephalusare now available to science and known from more than50 complete and nearly complete specimens as well as numerousisolated sclerites, and the majority are excellently preserved insoft orsten. All material derive from the Acadoparadoxidespinus–Pentagnostus praecurrens Zone in the autochthonousstrata around Lake Na¨kten (Ja¨mtland) and the Lower Allochthonfrom Ta°sjo¨ Mountain (A ° ngermanland). The fauna of the A.pinus–P. praecurrens Zone is a genuine, diverse ‘Paradoxides’fauna (nine species) with only very few representatives of otherpolymerid trilobites (five species) and agnostids (four species).Two species show affinity to Hydrocephalus minor and H.carens, respectively, which occur in the Barrandian of Bohemia.This study will lead to a significant increase in the taxonomicdiversity of the Paradoxididae, aid stratigraphical resolution andprovide important data for Middle Cambrian intercontinentalcorrelations.
2011. 73- p.