An outstanding upper Katian (Upper ) fossil assemblage from Portugal (Buçaco, Central Iberian Zone): biostratigraphical and palaeobiogeographical significance.

*Jorge Colmenar (1) Sofia Pereira (2,3,4) Artur A. Sá (3,4) and Carlos M. da Silva (2) (1) University of Copenhagen, Denmark (2) Universidade de Lisboa, Portugal (3) Universidade de Trás-os-Montes e Alto Douro, Portugal (4) Universidade de Coimbra, Portugal The Nicolella Community was the most typical brachiopod-dominated assemblage throughout high- latitude Gondwanan shelves during mid to late Katian times. It is widely represented in the Upper Ordovician rocks of the Porto de Santa Anna Formation (Central Iberian Zone, Portugal). The present study focuses on the rich fossiliferous silicified rocks of the upper half of this formation in the Cabeço Pedrogão locality (Espinheira, Buçaco). The fossil assemblage is dominated by echinoderms, followed by brachiopods and bryozoans, but and algae are fairly common too. The re-study of the classical fossil collections from these beds housed at the Museu Geológico (Lisbon), supplemented by several sampling campaigns, revealed the presence, among others, of previously unregistered brachiopod and taxa in Portugal: Kjaerina (Villasina) meloui, a brachiopod recorded previously only in the uppermost Rosan Formation (Armorican Massif, France); Ceraurinus? meridianus and “Bumastus” aff. commodus, trilobites only known from the Cystoid Limestone (Iberian Chains, Spain). These records are important additions to the knowledge of the Portuguese Upper Ordovician benthic marine communities, providing crucial new data to constrain the biostratigraphy of the upper half of the Porto de Santa Anna Formation and the palaeogeographical setting of this region during the Late Ordovician.

Biostratigraphical review and palaeobiogeographical remarks on the trilobite genus Lichas Dalman, 1827.

*Sofia Pereira (1,2,3) Artur A. Sá (2,3) Miguel Pires (4) and Carlos M. da Silva (1) (1) Universidade de Lisboa, Portugal (2) Universidade de Trás-os-Montes e Alto Douro, Portugal (3) Universidade de Coimbra, Portugal (4) Arcodere, Unipessoal Lda., Torres Novas, Portugal The trilobite genus Lichas is currently known from Upper Ordovician (uppermost Sandbian/Katian) to (Wenlock-Ludlow? Series) sequences. Originally described from the upper Katian of Sweden, the genus presently includes 11 valid species reported from Portugal, Spain, Italy, the United Kingdom, Sweden, Morocco, UEA and probably also Japan and Mongolia. Lichas keisleyensis Reed, 1896 is considered a junior synonym of L. subpropinquus McCoy, 1851. New data from the Upper Ordovician of Portugal led to the definition of two new species from the Porto de Santa Anna Formation (Katian) of Buçaco. The presence of Lichas sp. in the Chão do Amieiral and Cabeço do Peão formations (uppermost Sandbian/Katian) of Portugal constitutes the oldest records of this genus. From a phylogenetic point of view, the occurrence of Lichas in the Portuguese Upper Ordovician and the presence of a posteromedian spine in the pygidium of the oldest known species of the genus indicate a closer relationship between the monogeneric tribe Lichini and Dicranopeltini Phleger, 1936. Biostratigraphical and palaeobiogeographical analysis suggest that Lichas originated in high-latitude Gondwana, where it has its older record and numerous Sandbian/Katian species, and not in Baltica as previously considered.

The Ordovician explosion in the designs of trilobite eyes.

*Brigitte Schoenemann (1) and Euan N. K. Clarkson (2) (1) University of Cologne, Germany (2) University of Edinburgh, UK The eyes of trilobites are poorly known, apart from those of the eodiscids and the Furongian to upper Ordovician Order Olenidae, though more are being discovered. Most are reniform ‘slit-eyes’ and all are holochroal. Schizochroal eyes arose in the early Ordovician by paedomorphosis from a holochroal ancestor, but in addition the ‘explosion’ in trilobite diversity during the Ordovician is matched by a striking increase in different kinds of holochroal eyes. The range in holochroal eye morphology correlates well with the habitat of the Ordovician trilobites; thus thin-shelled trilobites living in quiet conditions normally have thin biconvex lenses, while robust-bodied trilobites living in high- energy environments have thick, and sometimes prismatic lenses. The optics of trilobite eyes can be studied using tools developed for the analysis of living eyes, which facilitate an understanding of habitat. Special attention here is given to the eyes of asaphid and cheirurid trilobites, which raise some interesting problems.

Trends in trilobite moulting.

*Harriet B. Drage University of Oxford, UK periodically moult their exoskeletons for growth, development and repair. The methods by which they moult are consistent within clades of extant taxa, but trilobites show uniquely high levels of variation in this behaviour, both within and between species. Trilobites exhibit at least six distinct moulting behaviours, producing exoskeleton fragment configurations that are recognizable in the fossil record. Here I present results of a study exploring broad trends in trilobite ecdysial patterns through time and taxonomy. I examined collections of trilobite-moulted exoskeletons, housed in museums across the UK (London, Oxford, Birmingham) and Sweden (Uppsala), and combined this with information from the descriptive literature. These data consist of information on moulting behaviour, measures of morphology and complexity, and growth data. No clear evolutionary patterns in trilobite ecdysis have previously been identified, or interpreted in light of their admittedly poorly-constrained phylogeny. However, new data suggest the occurrence of different moulting behaviours, which vary between Orders and through time, and are associated with variation in body size. Trends in trilobite moulting behavior relate to phylogeny, morphology and development, and have influenced the evolution and survivorship of the group. Future research will focus on moulting behaviour within well-sampled Orders and localities.