Rossellidae Schulze, 1885

Tabachnick, K. R., Menshenina, L. L. & Ehrlich, H., 2023, Rossellidae (Porifera: Hexactinellida) from the Bering Sea and off Bering Island, Invertebrate Zoology 20 (1), pp. 57-89 : 59

Rossellidae Schulze, 1885

The latest summary of the early history of Rossellidae and its scope is given by Tabachnick (2002b). This family is in the order Lysaccinosida and was originally subdivided into 3 subfamilies, Rossellinae (characterized by having neither discoctasters nor strobiloplumicomes), Lanuginellinae (characterized by the presence of strobiloplumicomes but no discoctasters), and Acanthascinae (characterized by having discoctasters but no strobiloplumicomes). Tabacknick (2002b) abolished the latter subfamily due to the presence of spicules resembling discoctasters in the holotype of the type species for the genus Caulophacus — C. (Caulophacus) latus . This genus together with Caulophacella was later moved from the Rossellinae to the Lanuginellinae ( Dohrmann et al., 2017; Reiswig et al., 2021). Reiswig and Stone (2013) resurrected the subfamily Acanthascinae , arguing that discoctasters were only found in the three genera within that group, without comment on the possible presence of these distinctive spicules in the genus Caulophacus . However, we continue to adhere to contend that the abolishment of the subfamily Acanthascinae is appropriate and suggest consideration of its tree genera status in the lower subgeneric level. As for the two remnant subfamilies of Rossellidae , the only morphological reason for the subdivision of this family was absence in Rossellinae and presence in Lanuginellinae of specific spicules — strobiloplumicomes. The genetic monophyletic charecters of these grpoops sudgested by Dohrmann et al. (2017) are not supported by any common morphological features sutable for the separate diagnoses of these two subfamilies. Inspite that the genetic analysis of Lanuginellinae supports keeping this subfamily no relible morphological features could be established to be valid for the diagnosis, which provides its definition from Rossellinae . A weak feature of this subdivision is connected with two facts. The first: absence of a peculiarity (in this case strobiloplumicomes in Rossellinae ) is a principally weak taxonomic feature, being alone it does not provide reliable ground for the taxon’s characterization – absence of a feature may be a result of multiple loses of it, or the feature has not appeared at all, thus the possibility of a polyphyletic origin of the taxon with such character is highly likely. And the second: strobiloplumicomes were not found in some specimens of monospecific Mellonympha — M. vellata (a doubtful Lanuginellinae representative) ( Tabachnick, 2002b). Now the new phylogenetic data led to the transferring of the genus Caulophacus (it is unclear complete (with numerous subgenera) or only a part of it) and suggestion of a new diagnosis for Lanuginellinae ( Reiswig et al., 2021) . This operation is a final point in the disappearance of the last reliable differences between the two remaining subfamilies and this fact requires the final formal action of the entire abolishment of discussed subfamilies. Thus Rossellidae now is an integral family, which has no subdivision into subfamilies. Meantime the fact of presence or absence of specific microscleres: discoctasters (former specific feature of Acanthascinae abolished by Tabachnick (2002b)) and presence of strobiloplumicomes (specific feature of former Lanuginellinae ) can be definitely used in keys to genera and subgenera of numerous rossellid taxa in corresponding chapters suggested by Tabachnick (2002b) following the insubstantial (as it is obvious now) subdivision into groups.