Phylogeny and revision of Leucaltis and Leucettusa (Porifera: Calcarea), with new classification proposals and description of a new type of aquiferous system Author Lopes, Matheus Vieira Author Klautau, Michelle text Zoological Journal of the Linnean Society 2023 2023-07-31 198 691 746 journal article 10.1093/zoolinnean/zlad008 0024-4082 7894159 5945BCC4-C3CB-4370-8ED8-632D8C6F1B15 FAMILY LEUCALTIDAE DENDY & ROW , 1913 The most recent diagnosis of Leucaltidae is: Clathrinida with a tubular, ramified or even anastomosed cormus with many oscula, or individualized with a large central atrium and a single osculum. The sponge wall is comprised of a distinct cortex sustained by a well-developed skeleton, and a choanosome. The skeleton of the choanosome and the atrial wall may be absent or comprised of small and dispersed triactines and tetractines ( Borojević et al. , 2002 ). According to our molecular and morphological results, only Leucaltis should be included in Leucaltidae . The aquiferous system of Leucaltis does not fit into any of the five types accepted up to date. Past works have considered it analogous to the leuconoid (e.g. Lanna et al. , 2009 ) or syconoid (e.g. Wörheide & Hooper, 1999 ) aquiferous systems, although the choanocyte chambers are not spherical nor do they have a regular radial orientation around the atrium. Pinacocytes are restricted to the external and atrial surfaces. Dendy (1893) described the ‘ type C’ for this organization of the choanocyte chambers, which are mostly elongated and ramified, commonly fusing with each other ( Fig. 3 ). It must not be mistaken with the solenoid aquiferous system because, in Leucaltis , the choanoderm is present inside the ramified chambers, instead of revesting the internal part of the anastomosed choanocyte tubes. Finally, it differs from the sylleibid aquiferous system because choanocyte chambers do not group around a common exhalant chamber. This kind of aquiferous system is present in five out of the six accepted species (following this work). Leucaltis sambucus is said to be leuconoid, but samples of this species were not found, hence we cannot corroborate if it has indeed a leuconoid aquiferous system. Considering that the aquiferous system of Leucaltis has been referred to as leuconoid in past descriptions, it is possible that L. sambucus is not leuconoid, but has the distinct aquiferous system of the other Leucaltis species. Leucaltis corticata is mentioned as having a similar aquiferous system to Leucaltis clathria ( Poléjaeff, 1883: 10 ) : ‘with the extension of the flagellated chambers into larger cavities of irregular outline, which come into contact with each other and anastomose, thus forming still larger sinus-like spaces’. For that reason, we draw attention to the presence of the new aquiferous system of Leucaltis in Leucaltis corticata . We suggest the name kladonoid for this new aquiferous system, derived from the Greek kladotós (= ΚΛαδωτός ), branched, ramified. For Leucaltidae , we propose to modify the diagnosis to: Clathrinida with a body comprised of large, ramified and anastomosed tubes; never clathroid. Each tube has a distinct cortex, a choanoderm and a central atrium. The skeleton of the choanosome and atrium is comprised of regular and/or sagittal triactines and tetractines much smaller than the cortical ones. Aquiferous system kladonoid, with elongated and ramified choanocyte chambers.