Order CLATHRINIDA Hartman, 1958

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Diagnosis

Calcinea with the skeleton composed exclusively of free spicules, without hypercalcified non-spicular reinforcements, spicule tracts, calcareous scales or plates.

ID Keys

KEY TO GENERA
(1) Sponge body composed of individual, anastomosed or ramified tubes, choanocytes line all internal cavities of the sponge-----------------------------------------------------------------------------2
Choanocytes do not line all internal cavities of the sponge----------------------------------------9

(2) No differentiated diverticuli on external part of the tubes; when a large cormus is formed there is no common cortex covering the whole body-------------------------------------------------4
Differentiated diverticuli on the external part of the tubes with a particular skeleton---------3
(3) Central tube ornamented with short, external, regularly distributed, radial diverticuli-----------Sycettaga
Central tube ornamented with external groups of ovoid diverticuli, which communicate with the central tube through a shallow cavity---------------------------------------------------Levinella

(4) Choanoderm flat, or exceptionally elevated in the form of cones around apical rays of tetractines, but never forming true folds----------------------------------------------------------------5
Choanoderm forming folds inside the choanocoel, delimiting shallow or deep radial spaces or tubes, supported by apical rays or tetractines from the external skeletal layer--------------------Ascandra

(5) Sponge body in form of solitary, sometimes distally ramified tubes, or composed of anastomosed tubes forming a large cormus-----------------------------------------------6
Sponge in the form of a large central tube bearing long radially arranged tubes, amply ramified in their distal part, but only occasionally anastomosed in their proximal part------------------Dendya

(6) Sponge in the form of solitary tubes, sometimes terminally ramified, or groups of erect tubes, growing from creeping stolon-like tubes-----------------------------------------Soleneiscus
Sponge in the form of anastomosed tubes--------------------------------------------------------------7

(7) Sponge cormus with distinct peduncle, solid or formed of normally organized, partially or fully coalescent tubes. Skeleton composed of parasagittal spicules, or of regular spicules to which parasagittal spicules are added, at least in the peduncle-----------------------Guancha
Sponge cormus without a distinct peduncle-----------------------------------------------------8

(8) Sponge body formed of anastomosed tubes, without a common cortex surrounding the whole cormus---------------------------------------------------------------------------Clathrina
Sponge body composed of amply anastomosed tubes covered by a distinct cortex surrounding the whole body. No exhalant aquiferous system; a pseudoatrium may be exceptionally formed through the calyciform growth of the sponge---------------------------------------------Ascaltis

(9) Sponge composed of central, occasionally ramified tubes, ornamented with distinct external diverticuli having their own skeleton, different from that of the central tube-----------------------------------------Burtonulla
Sponge with a compact body without external diverticuli-----------------------------------------10

(10) Sponge body composed of a network of anastomosed and ramified tubes with a proper skeleton and covered by a thin cortex. Central atrial cavity surrounded by a thin wall, with a proper skeleton------------------------------------------------------Leucascus
Sponge body solid; when the choanocyte chambers are elongated they do not have a proper skeleton, but are embedded in the choanosomal skeleton------------------------------------------11

(11) Sponge with a clear distinction between a solid cortex and the choanosome. Choanoskeleton and/or atrial skeleton absent, or when present, composed of diffuse triactines and/or tetractines much smaller than spicules of the cortical skeleton----------------------------12
Sponge without a clear distinction between the solid cortex and the choanosome supported by a reduced choanoskeleton-----------------------------------------------14

(12) Sponge composed of an external wall sustained by large radiate spicules; aquiferous system leuconoid, choanosome devoid of a skeleton-----------------------------------Leuclathrina
Sponge with elongate and/or spherical choanocyte chambers; in addition to the strong cortical skeleton, smaller spicules present in atrial and/or choanosomal skeleton-------------------------13

(13) Sponge body composed of large anastomosed tubes; the wall of each tube consists of a distinct cortex, a choanosome containing elongated choanocyte chambers and a large central atrium----------------------------------------------------------------------Leucaltis
Sponge body solid, occasionally ramified but not in the form of anastomosed tubes; aquiferous system containing elongated and/or spherical chambers. Large central atrium always present--------------------------------------------------------------------------------Leucettusa

(14) Sponge body solid; atrium often reduced to exhalant channels opening directly into osculum. Leuconoid organisation with choanosome supported by a regular network of triactines to which tetractines may be added; no distinct subcortical layer of inhalant chamber------------Leucetta
Sponge body solid with large atrium. Leuconoid organisation with subcortical system of inhalant cavities supported by a skeleton in part composed of centripetal rays of cortical triactines-----------------Pericharax

Diagnosis References

Borojevic, R., Boury-Esnault, N., Manuel, M. & Vacelet, J. 2002. Order Clathrinida Hartman, 1958. pp. 1141-1152 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. [1141]

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