Antarctotetilla Carella et al. 2016

Genus Antarctotetilla Carella et al., 2016

Definition: Tetillidae with pores grouped in small surface depressions or in sieve-like areas, without porocalices and without a proper cortex, but with a loose arrangement of auxiliary oxeas at the sponge periphery (i.e. pseudocortex) (Carella et al. 2016).

Diagnosis: Globular or egg shaped sponges. Surface mainly smooth and without porocalices, with one or several oscules situated on top. Pores always grouped in small surface depressions or in sieve-likes overlying a subectosomal cavity. Basal bundles of spicules at the sponge base, acting as a root system. Consistency generally compact out of the water. No a real cortex, but a pseudocortex composed of few auxiliary oxeas, perpendicular to the surface mostly concentrated at the final part of the radial spicule bundles. Choanosomal skeleton consists of spiral bundles of oxeas accompanied by anatriaenes and protriaenes radiating from the sponge center towards the surface. The bundles may pierce the ectosome in some zones and thus cause a locally hispid surface. Megascleres are oxeas, protriaenes, anatriaenes and trichodal protriaenes; microscleres are sigmaspires. Distribution: mainly on deep bottoms of Antarctic, Subantarctic, and New Zealand waters (Carella et al. 2016)

Remarks. Antarctotetilla differs from the typical Tetilla by the presence of pores grouped in shallow subectosomal depressions, covered by a perforate ectosome or not, and a peripheral concentration of auxiliary oxeas, irregularly arranged, forming a visually discerned layer, very different of a true cortex (e.g. that of Craniella or Cinachyra). The genus also differs from Cinachyra and Cinachyrella in the lack of porocalices. The reexamination of the species types (holotypes of Tetilla leptoderma, Tetilla grandis and syntype of Tethya sagitta) allowed us confirming these morphological features. The molecular and parsimony (morphological) phylogenies (Carella et al. 2016) clustered specimens previously described as Tetilla leptoderma Sollas, 1886, Tetilla grandis Sollas, 1886, and Tethya sagitta Lendenfeld, 1907 in a monophyletic clade that corresponds to the new genus. Furthermore, the revision of the syntype of Tethya coactifera as well as the new species Tetillidae sp.3 (Carella et al. 2016), now A. pilosa (see below), has proved they belong in Antarctotetilla.