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Large quarrying surfaces of roofing slate in the Arouca Geopark (northern Portugal), formed under oxygen-depleted conditions, have yielded a unique Ordovician fossil lagerstätte that reveals new information on the social behavior of trilobites. It provides several of the world's largest trilobite specimens (some reaching 70 cm), showing evidence of possible polar gigantism in six different species, as well as numerous examples of monotaxic and polytaxic size-segregated autochthonous trilobite clusters, some of which contain as many as 1000 specimens. These reveal a very diverse social behavior, which includes temporary refuge from predation and synchronous molting and reproduction, demonstrated for the first time in five contemporary families of three different trilobite orders from a single formation. [ABSTRACT FROM AUTHOR]

A comprehensive treatment of Ordovician crinoids from southwestern Europe is presented, including taxa based on articulated crowns and stems. This summary incorporates new material, new localities, and a revision of some southwestern Europe occurrences. The first record of an Ordovician crinoid from Portugal, Delgadocrinus oportovinum n. gen. and sp., is reported, and this is the oldest known crinoid from the Iberian Peninsula (Arenigian/Oretanian boundary, early Darriwilian). Geographic and temporal ranges of several crinoids are revised from peri-Gondwanan areas in southwestern Europe and northern Africa or modified with new Iberian material. The Spanish range of Heviacrinus melendezi Gil Cid et al., 1996 is extended down into the lower upper Oretanian, and Merocrinus millanae Ausich et al., 2002 is restricted to the upper lower Dobrotivian. The stratigraphic position of Ortsaecrinus cocae Gil Cid et al., 1999b is restricted to the early middle Berounian, and the range of Visocrinus castelli Ausich et al., 2002 is restricted to the late middle Berounian (see Fig. 2). New topotype material of Morenacrinus silvani Ausich et al., 2002 is reported that furthers understanding of the occurrence this taxon, which was previously only positively known from the holotype. [ABSTRACT FROM AUTHOR]