A highly diverse siliceous sponge fauna (Porifera: Hexactinellida, Demospongiae) from the Eocene of north-eastern Italy: systematics and palaeoecology

Abstract

A siliceous sponge fauna, consisting of more than 900 specimens, is described from an early Lutetian tuffite horizon in the Chiampo Valley, Lessini Mountains, north-eastern Italy. Thirty-two taxa (15 Hexactinellida, 17 Demospongiae) are determined and illustrated, belonging to 24 genera, two of which are new (Rigonia gen. nov. and Coronispongia gen. nov.). Among these, 10 new species are proposed: Stauractinella eocenica sp. nov., Rigonia plicata gen. et sp. nov., Hexactinella clampensis sp. nov., Camerospongia visentinae sp. nov., C. tuberculata sp. nov., Toulminia italica sp. nov., Coronispongia confossa gen. et sp. nov., Cavispongia scarpai sp. nov., Corallistes multiosculata sp. nov. and Bolidium bertii sp. nov. Of the genera identified at Chiampo, 14 range back to the Cretaceous, three to the Jurassic and one to the Triassic, while six are still extant. The studied fauna shows affinities with sponges from the Eocene of Spain and the Cretaceous of Germany. The sponge fossils are uncompressed and bodily preserved, but the original siliceous skeleton is dissolved and substituted by calcite. Delicate attachments can be nevertheless documented: some sponges attached to a hard substrate by encrustation, while others were anchored on soft sediments by root-like structures. The presence of different modes of attachment suggests heterogeneous substrate conditions. Small, possibly young, sponges are recorded too. The sponge fauna is essentially autochthonous and lived in the middle-outer part of a carbonate ramp, where it formed clusters. This study extends the geographical and stratigraphical range of many sponge taxa, including Camerospongia, Toulminia, Ozotrachelus and Bolidium, previously documented only from the Cretaceous. The Recent calcified demosponge genus Astrosclera is reported here in the Cenozoic for the first time, having been reported previously in the Triassic only. Additionally, this study documents the second worldwide occurrence of the Recent sphinctozoan genus Vaceletia in the Palaeogene, formerly recorded exclusively in Australia.

http://zoobank.org/urn:lsid:zoobank.org:pub:B3466955-8E20-429A-89BE-42BAEB4002E8

Keywords:

• Hexactinellida
• Demospongiae
• Eocene
• Italy
• palaeoecology

Acknowledgements

This work was supported by the Municipality of Montecchio Maggiore, Museo di Archeologia e Scienze Naturali ‘G. Zannato’, Italy. Andrzej Pisera's visit to the Geoscience Department (Padova University) was funded by the International Office, Padova University. We are deeply indebted to the following professional and amateur palaeontologists who made this study possible: Livia Beccaro, Bruno Berti, Claudio Beschin, Fabrizio Bizzarrini, Andrea Checchi, Gilberto Cracco, Antonio De Angeli, Franco Mastrovita, Giancarlo Scarpa and the ‘Amici del Museo Zannato’ Association. We are grateful to the following people and institutions for providing access to the specimens in their care: Barbara Favaretto (Museo di Storia Naturale di Venezia), Mariagabriella Fornasiero (Museo di Geologia e Paleontologia dell'Università degli Studi di Padova), Bernardetta Pallozzi (Museo Civico ‘D. Dal Lago’, Valdagno), Antonio Dal Lago (Museo Naturalistico Archeologico, Vicenza) and Valentina Carpanese (Museo ‘Padre Aurelio Menin’, Chiampo). We also highly appreciate the help of many collegues from the Padova University, Geoscience Department: Paolo Mietto (local geology expertise); Claudia Agnini (nannofossil expertise); Lorenzo Franceschin and Carlotta Betto (Micropalaeontogy Laboratory); Leonardo Tauro and Elena Masiero (Thin Sections Laboratory); and Nicola Michelon (graphical expertise). All photographs (unless otherwise indicated) were taken by Stefano Castelli, who we thank especially for his excellent work. We thank Alessandro Minelli (Padova University) and Wolfgang Kiessling (Erlangen University) for stimulating discussions and advice. The manuscript also benefitted from the constructive comments of two anonymous reviewers.

Supplemental material

Supplemental material for this article can be accessed here: http://dx.doi.org/10.1080/14772019.2015.1132015