Systema Porifera: A Guide to the Classification of Sponges, Edited by John N.A. Hooper and Rob WM. Van Soest © Kluwer AcademiclPlenum Publishers, New York, 2002 Family Tracbycladidae Hallmann, 1917 John N.A. Hooper l & Rob W.M. Van Soest 2 1 Queensland Museum, P.O. Box 3300, South Brisbane, Qld, 4101, Australia. (JohnH@qm.qld.gov.au) 2 Zoological Museum, University of Amsterdam, P.O. Box 94766,1090 GT, Amsterdam, Netherlands. (soest@science.uva.nl) Trachycladidae Hallmann (Demospongiae, Hadromerida), contains two genera with at least nine species, all having an axial (or basally) compressed skeleton, and an extra-axial plumo-reticulate skeleton, with megascleres predominantly oxeas, less often strongyles and/or (tylo-)styles, in spongin-enforced multispicular tracts, or in the case of encrusting species, megascleres erect on the substrate (in hymedesmioid arrangement). Ectosomal skeleton is a crust of spinispirae (spined vermiform spiraster-like spicules), with smooth microrhabds and/or spinispirae dispersed throughout the mesohyl. The two genera are differentiated on the basis of fundamental differ- ences in spinispirae morphology. Species are known from the shallow subtidal to about 220 m depth, distributed from temperate Australia, New Zealand and New Caledonia, Indonesia, East Africa and South Africa, Mediterranean and the western North Atlantic. Keywords: Porifera; Demospongiae; Hadromerida; Trachycladidae; Rhaphidhistia; Trachycladus. DEFINITION, DIAGNOSIS, SCOPE Synonymy Trachycladidae Hallmann, 1917c: 673. [Spirophorellinae] Lendenfeld, 1889b (nomen nudum). Rhaphidistiinae de Laubenfels, 1936a. Definition Hadromerida with spined vermiform spinispirae and smooth microrhabds, with a differentiated axial and extra-axial skeleton cored by oxeas, strongyles and/or (tylo-)styles. Diagnosis Encrusting, massive or branching growth forms. Oscules are small (less than 1 mm diameter) and ostia are scattered singly or grouped. Skeleton is condensed in the axial region and plumo- reticulate in the extra-axial region, with ascending multispicular tracts joined at infrequent intervals by single spicules. Encrusting species have a hymedesmioid architecture. Skeletal tracts are composed of spongin fibres enclosing oxeas, strongy1es and/or (tylo-)styles. Microscleres are smooth microstrongyles (microrhabds) and/or spined vermiform spiraster-like spiru1es (spinispirae), with either a curled shaft bearing longitudinal rows of spines along its length, or a straight shaft bearing concentric spiral rows of spines around its circumference and length. Remarks Trachycladus was allocated to Axinellidae as 'Axinellidae with microscleres', but nevertheless recognised as anomalous (Hallmann, 1916a: 454), and later (in postscript) allocated to a monogeneric subfamily Trachycladinae (Hallmann, 1917c: 673). Topsent (l928c) overlooked or ignored Hallmann's new subfamily in his revision of Demospongiae, and retained the genus in Axinellidae. Hallmann (1916a: 454) remarked on the obvious derivation of spinispirae from spirasters of Spirastrella, the fact that microrhabds occur commonly in hadromerids, and (less convincingly) that some Spirastrellidae (e.g., S. dilatata Kirkpatrick) have megascleres united into spongin-enforced tracts reminiscent of Trachycladus. Conversely, he noted that Trachycladus had skeletal structure reminiscent of sigma-bearing poecilosclerids (which we now know as Desmacellidae), and thus supposedly represented a link between Spirastrellidae and Poecilosclerida. Brlilndsted (1924b) also stressed the close relation- ship between Trachycladus and Spirastrellidae and Latrunculia, although the latter taxon is no longer widely included in this relationship (see chapters on Latrunculiidae and Podospongiidae, this volume). Similarly, Trachycladidae was included in the polyphyletic order Axinellida by Bergquist (1970, 1978), Levi (1973), Hartman (1982) and others, as opposed to an allocation in Hadromerida, implicitly based on possession of an axially compressed and extra-axially plumo-reticulate skeletal structure, spongin-enforced spicule tracts, bright colouration, arborescent growth form (Levi, 1973). Unfortunately there is no corroboratory evidence to support a close relationship between typical axinellids (e.g. Axinella) and Trachycladus (e.g., oviparous mode ofreproduc- tion, parenchymella larvae), and in the absence of this evidence Trachycladidae is included in Hadromerida. Conceivably, however, it could justifiably be merged in Spirastrellidae given the fundamen- tal similarities in their microscleres, although with equally funda- mental differences in patterns of spination, hypothesised to reflect ontogenetic differences in their respective development. Scope and biology Four nominal genera have been included, or potentially included in the family, of which two are considered here to be valid, Trachycladus and Rhaphidhistia. There are 17 nominal species or subspecies referred to the family at one time or another, of which only nine are probably valid: seven allocated to Trachycladus, and two to Rhaphidhistia. These are: (I) T. laevispir- ulifer Carter (the type species, from E, SE, Sand SW Australia, including as synonyms: digitata Lendenfeld, 1888; scabrosus Hallmann, 1916a;fastigatus Hallmann, 1916a; gracilis Hallmann, 1916a; clavatus Hallmann, 1916a, reteporosus Hallmann, 1916a; and pustulosus Hallmann, 1916a); (2) T. strongylatus Hallmann, 1916a (as T. digitatus strongylatus, from Victoria) 268