Helcionelloida

Helcionelloida; Temporal range: Early Cambrian–Early Ordovician PreꞒ Ꞓ O S D C P T J K Pg N
	Latouchella costata
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	†Helcionelloida; Peel, 1991
Orders
	Order Helcionelliformes; Order Pelagialliformes; Order Khairkhaniiformes; Order Onichochiliformes; and see text

The Helcionelloida are an extinct class of fossil molluscs.

They are among the earliest animals with mineralised shells. They are also the oldest known molluscs wth a shell. Some members of this class were mistaken for Monoplacophorans. The class was erected by Peel in 1991.^[1]

The latest word on this group is the classification of Parkhaev, who splits it into three subclasses.^[2]^[3]

References

↑ Peel J.S. 1991. Functional morphology of the Class Helcionelloida nov., and the early evolution of the Mollusca. In Simonetta A.M. & Conway Morris S. The early evolution of metazoa and the significance of problematic taxa. Cambridge University Press, pp. 157–177. ISBN 978-0-521-40242-2
↑ P. Yu. Parkhaev (2006) "Adaptive radiation of the Cambrian helcionelloid mollusks (Gastropoda, Archaeobranchia). Archived 2015-06-10 at the Wayback Machine" In: S.V. Rozhnov (ed.) "Evolution of the biosphere and biodiversity. Towards the 70th anniversary of A. Y. Rozanov". 2006. Moscow, pp. 282-296.
↑ P. Yu. Parkhaev (2007). "The Cambrian 'basement' of gastropod evolution". Geological Society, London, Special Publications. 286 (1): 415–421. Bibcode:2007GSLSP.286..415P. doi:10.1144/SP286.31. S2CID 130979274.

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[Peel1991-1] Peel J.S. 1991. Functional morphology of the Class Helcionelloida nov., and the early evolution of the Mollusca. In Simonetta A.M. & Conway Morris S. The early evolution of metazoa and the significance of problematic taxa. Cambridge University Press, pp. 157–177. ISBN 978-0-521-40242-2

[2] P. Yu. Parkhaev (2006) "Adaptive radiation of the Cambrian helcionelloid mollusks (Gastropoda, Archaeobranchia). Archived 2015-06-10 at the Wayback Machine" In: S.V. Rozhnov (ed.) "Evolution of the biosphere and biodiversity. Towards the 70th anniversary of A. Y. Rozanov". 2006. Moscow, pp. 282-296.

[Parkhaev_2007-3] P. Yu. Parkhaev (2007). "The Cambrian 'basement' of gastropod evolution". Geological Society, London, Special Publications. 286 (1): 415–421. Bibcode:2007GSLSP.286..415P. doi:10.1144/SP286.31. S2CID 130979274.

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