Zygherpe

Hajdu, Eduardo, Hooker, Yuri & Willenz, Philippe, 2015, New Hamacantha from Peru and resurrection of Zygherpe as subgenus (Demospongiae, Poecilosclerida, Hamacanthidae), Zootaxa 3926 (1), pp. 87-99 : 89

Subgenus Zygherpe de Laubenfels, 1932 (revalidated)

Diagnosis. Hamacantha with tylostyles and encrusting habit. Type species— Zygherpe hyaloderma de Laubenfels, 1932: 65.

Remarks. De Laubenfels (1932) erected Zygherpe for encrusting sponges bearing tylostyles and diancistras. With a single species known, Hajdu (1994) argued that the occurrence of tylostyles per se was not a solid character on which to diagnose a new genus for sponges with diancistras and proposed the synonymy of Zygherpe with Hamacantha . Subsequently, Hajdu (2002) proposed to assign species with diactinal megascleres to subgenus Hamacantha , and those with monactinal megascleres to subgenus Vomerula . The finding of a second species sharing relevant morphologic features with Hamacantha hyaloderma suggests it is worth reinstating de Laubenfels’ genus Zygherpe , here assigned to subgenus level, to further discriminate species with tylostyles from those with styles. The shared occurrence of encrusting habit, tylostyles and sigmas, as well as the overlapping distribution of H. (Z.) desmacelloides sp.nov. and H. (Z.) hyaloderma is remarkable.

Subgenera in Porifera are currently used as a convenient classification rank ( Hooper, 2002; van Soest, 2002a, b; van Soest & Hajdu, 2002), with no general claim for monophyly. Most of these are former genus names, downgraded to subgeneric rank as a consequence of suspicion (or even confirmation) of their non-monophyly. It is beyond the scope of this contribution to debate whether or not these assemblages should be kept in use or abandoned altogether. Rather, the decision taken here aims to undo a possibly unjustified taxonomic decision taken by Hajdu (1994, 2002), when Zygherpe was synonymized with Hamacantha . The main argument used for the proposed synonimization was the redundancy of recognition of higher taxa for single species (which renders genus and species diagnoses the same). This argument collapsed after a second species with tylostyles was found by us in Peru. We had to choose between resurrecting Zygherpe , which we preferred, or to assign both species with tylostyles to either Hamacantha (Hamacantha) or H. ( Vomerula ). The dichotomy between monactines and diactines suggested by the Systema Porifera classification for hamacanthids need not be entirely meaningful in evolutionary terms, and above all, there is no real evidence that species with tylostyles are possibly closer to those with styles than to others with oxeas. For this reason, we deemed convenient to take advantage of de Laubenfels’ taxon, which is resurrected here to keep both species with tylostyles, until further evolutionary evidence convincingly points in an alternative direction.