Order LYSSACINOSIDA Zittel, 1877

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Diagnosis

Body form is typically a single ovoid, cup or tube bearing a single terminal osculum and deep atrial cavity, with either basiphytous or lophophytous substrate attachment, either directly or by short peduncle or long stalk; basiphytous forms attach by a thin basidictyonal plate of fused hexactins; thin-walled forms may have a sieve plate over terminal osculum and a regular series of small parietal oscula; thicker-wall forms may occasionally bifurcate or grow one or more lateral diverticula, each with terminal osculum; branching in stalks of cap-shaped members is poorly documented as a growth form and may result from secondary settlement; choanosomal megascleres may be mainly hexactins, a combination of stauractins, tauactins and diactins, or mainly diactins; dermalia may be large pentactins or hexactins unsupported by hypodermalia or small hexactins (pinular or regular), pentactins, stauractins or diactins supported by large pentactin hypodermalia; atrialia may be either hexactins and/or pentactins and/or stauractins; lateral prostalia may be absent or special diactins or extended hypodermal pentactins or simply the extended distal rays of choanosomal hexactins or pentactins; basalia of lophophytous forms may be monactine, diactine or pentactine anchors; microscleres include single types or combinations of stellate and spherical discohexasters of regular or hemi-form, discoctasters, discohexactins, floricomes, plumicomes, strobiloplumocomes, sigmatocomes, oxyhexasters of regular and hemi-form, oxyhexactins and onychexasters.

ID Keys

KEY TO FAMILIES
(1) Choanosomal megascleres mainly diactins; with hypodermal pentactins ------------------------------- Rossellidae
Most choanosomal megascleres other than diactins; without hypodermalia ---------------------------------------------- 2

(2) Choanosomal megascleres mainly hexactins ----------------------------------------------------------- Leucopsacidae
Choanosomal megascleres mainly stauractins, tauactins and diactins ----------------------------------- Euplectellidae

Diagnosis References

Reiswig, H. 2002. Order Lyssacinosida Zittel, 1877. 1387 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. [1387]

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