Order AMPHIDISCOSIDA Schrammen, 1924

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Diagnosis

Recent Amphidiscosida are distinguished from the other Amphidiscophora order, the fossil Hemidiscosida Schrammen, by amphidisc, rather than hemidisc, microscleres. All Amphidiscosida are lophophytous, with skeletons composed of loose (non-fused) spicules. Body forms are highly variable, including solid ovoids and cylinders, solid or hollow funnels or cups, and flattened bilateral variations of these. Some patterns of spicule form and location are consistent for all families, including pinular pentactins and rarely hexactins as dermalia and atrialia, oxypentactins as hypodermalia and hypoatrialia, basalia (where known) as monactins with one to many teeth at the lower ‘center’ end, three forms of amphidiscs and oxyhexactins as microscleres. Variation occurs in basalia (numbers of basalia, numbers of basalia bundles, compactness of basalia bundles, and numbers of head teeth), presence and form of prostalia (pinular diactins, monactine sceptres or none), and form of main choanosomal spicules. Families are presently distinguished most easily on the basis of the latter: principalia are diactins in Hyalonematidae, tauactins in Monorhaphididae, and pentactins in Pheronematidae.

ID Keys

KEY TO FAMILIES
(1) Major choanosomal spicules are diactins ------------------------------------------------------------- Hyalonematidae
Major choanosomal spicules other than diactins ------------------------------------------------------------------------------- 2

(2) Major choanosomal spicules are tauactins ----------------------------------------------------------- Monorhaphididae
Major choanosomal spicules are pentactins ----------------------------------------------------------------Pheronematidae

Diagnosis References

Reiswig, H. 2002. Order Amphidiscosida Schrammen, 1924. 1231 in Hooper, J.N.A. & Soest, R.W.M. Van (eds). Systema Porifera. A guide to the classification of sponges. New York : Kluwer Academic/Plenum Publishers Vol. 2. [1231]

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