Fragmentation as a novel propagation strategy in an Early Ordovician graptolite

Abstract

VandenBerg, Alfons H.M., November 2017. Fragmentation as a novel propagation strategy in an Early Ordovician graptolite. Alcheringa 42, 1–9. ISSN 0311-5518.

Catenagraptus communalis gen. nov. sp. nov. is a late Floian (Early Ordovician) graptolite from Victoria, Australia, only found as fragments, with each fragment resembling an assemblage of uniserial tubarium-like structures (pseudotubaria) connected by threads (aulons). Individual pseudotubaria consist of a fallosicula and a stipe, both of which are linked by aulons to other pseudotubaria. Adjacent pseudotubaria are in a parent–offspring relationship. Aulons can be generated from both the proximal and distal extremities of fallosiculae, and from the ends of stipes. The aulons are interpreted to have been grown by the zooid that occupied either the fallosicula or the terminal theca of the stipe. Aulons were pathways for a zooid that built a fallosicula at the end of the aulon. This process was repeated to form the assemblage. None of the assemblages contain a true sicula, which suggests that the assemblages present evidence of a new, asexual propagation strategy that involved fragmentation and dispersal. As this interpretation is radical, other models explored are partial sclerotization and modified sicular spines.

Alfons H.M. VandenBerg [[email protected]], Museum Victoria, GPO Box 666, Melbourne 3001, Victoria, Australia.

Key words:

• graptolite pseudotubarium
• fallosicula
• aulon
• propagation strategy

Acknowledgements

I thank Roger Cooper (GNS Science, New Zealand)) and Jörg Maletz (Freie Universität Berlin), Lucy Muir (National Museum of Wales, Cardiff/Nanjing Institute of Geology and Palaeontology) and one unnamed reviewer, for helpful criticism that significantly improved the paper, and Leon Costermans for help in making the figures suitable for publication. Roger Cooper suggested alternative structures for the colony and provided Fig. 8.