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Class Ophiuroidea groups the most diverse and abundant organisms of the phylum Echinodermata, having approximately 2100 described species. They have a simple body plan, consisting of a central disk, where their main internal organs are located, and to which the arms are attached. Species are identified based mostly on external morphological characters. However, many species present similar diagnostic characters in several families, which makes their phylogenetic reconstruction quite complex. Furthermore, many of these characters undergo changes during post-larval development and growth. Therefore, ontogenetic studies become relevant. Progress is still slow in this field, however, mainly due to difficulties in identifying some species in these stages. Despite significant advances in the number of species described for the Northeast region of Brazil, studies on the growth series of species of Ophiuroidea reported for this region are still scarce. The present work describes the intraspecific variations of Ophionereis reticulata (Say, 1825), Ophionereis squamulosa Koehler, 1914, and Amphipholis squamata (Delle Chiaje, 1828), considering young and adult specimens. The morphometry of individuals and aspects of microstructure are included. The description of morphological characters in growth series allowed us to identify typical characteristics of certain stages. Some structures remained almost unchanged, while others underwent most of the changes, being used to characterize different growth stages. Such stages are helpful for the correct identification of these species. In addition, the study of morphological variations between young and adult specimens contributes to our understanding on evolutionary relationships within Ophiuroidea. [ABSTRACT FROM AUTHOR]

For a long time, as the asterozoan studies were rare among Devonian invertebrates of the Paraná Basin, the knowledge about the taxonomy, taphonomy, and palaeoecology of this regional group remained extremely limited. Therefore, this research focuses for the first time on the detailed identification and classification of fossil asteroids and ophiuroids from the Jaguariaíva and São Domingos members of the Ponta Grossa Formation. As a result, four species are described herein, Paranaster crucis nov. gen., nov. sp., Magnasterella darwini (Clarke, 1913) nov. gen., Encrinaster pontis (Clarke, 1913), and Marginix notatus nov. sp. In addition, the Paranasteridae nov. fam. is also proposed. On the other hand, the taphonomic analysis of this asterozoans, together with the interpretation of sedimentary matrix and associated fossil assemblages, reveals important palaeoenvironment details from the Devonian of the Paraná Basin. These echinoderms lived in a marine platform governed by a polar climate and low sedimentation rates. But the commonly articulated asterozoans also support important events of rapid burial. Finally, this research expands the diversity of malvinokaffric echinoderms, contributing to the palaeoecological reconstruction of the Ponta Grossa Formation. Image 1 • This manuscript is a review of the Brazilian Devonian asterozoan fauna. • A new family, two new genera, and two new species described. • Two new Malvinokaffric asterozoans: Paranaster crucis and Marginix notatus. [ABSTRACT FROM AUTHOR]

Ophioscolex glacialis Müller and Troschel, 1840 (Ophiuroidea: Ophiomyxidae) was registered for first time off the Brazilian coast, from the Campos Basin of Rio de Janeiro, Brazil. The specimen was sampled during a environmental monitoring. [ABSTRACT FROM AUTHOR]