No abstract

The analysis of 359 samples from three regions of the Brazilian continental shelf (Northern, Northeastern and Eastern) resulted in the recognition of six species of the genus Xestoleberis. One of these species was already described, X. umbonata Whatley et al. 1998, four species are new and herein described, X. inesae sp. nov., X. amazonica sp. nov., X. subtriangularis sp. nov. and X. virilis sp. nov., and one was maintained in open nomenclature, Xestoleberis sp. The species X. inesae sp. nov. is widely distributed in the study area, occurring in all mentioned regions, while X. amazonica sp. nov. is restricted to the Northern region. Xestoleberis subtriangularis sp. nov., X. virilis sp. nov. and Xestoleberis sp. occur in the Northeastern and Eastern regions. Xestoleberis umbonata was recorded in this study only in the southernmost part of the Eastern region.

OPERATOR BIAS AND REPLICABILITY IN COMPARATIVE TAPHONOMIC STUDIES. The operator effect is a well-known analytical bias already quantified in some taphonomic studies. However, the influence of operator bias in the replicability on taphonomic studies has still not been considered. Here, we quantified for the first time this bias using different multivariate statistical techniques, testing if the operator effect is related to the replicability. We analyzed the results reported by 15 operators working on the same dataset. Each operator analyzed 30 bioclasts (bivalve shells) by site, from a total of five sites, considering the following taphonomic attributes: shell fragmentation, edge rounding, corrasion, bioerosion, and color alteration. The operator effect followed the same pattern reported in previous studies, characterized by a worse correspondence for those attributes having more than two levels of damage categories. However, the effect did not appear to have relation to replicability, because nearly all operators found differences among sites. The binary attribute bioerosion exhibited 83% of correspondence among operators, but at the same time it was the taphonomic attribute that showed the highest dispersion among operators (28%). Therefore, we concluded that binary attributes, despite indicating a reduction of the operator effect diminishes replicability, resulting in different interpretations of concordant data. We found that a variance value of nearly 8% among operators was enough to generate a different taphonomic interpretation, in a Q-mode cluster analysis. The results reported here showed that the statistical method employed influences the level of replicability and comparability of a study and that the availability of results may be a valid alternative to reduce bias.

This work is the second part of the analysis of ostracods from the Vitória-Trindade Chain ̶ consisting of four seamounts and Trindade Island—which resulted in the recording of 28 species belonging to 14 genera and eight families. Five new species of Cytherellidae, Bairdiidae, Bythocytheridae, and Xestoleberididae are described in this paper, as follows: Keijcyoidea oceanica sp. nov., Bairdoppilata vitoriensis sp. nov., Vandenboldina kyryia sp. nov., Xestoleberis acuminata sp. nov. and Xestoleberis caperata sp. nov.