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criteria adopted for separating couples of confamil- in length and 600 μm in width: see measurements)
iar genera, such as the couple formed by Therenia to the curving or irregularly uneven morphology
David & Pouyet, 1978 and Herentia Gray, 1848 of the colonised surfaces. Finally, zooids are loosely
within the Escharinidae Tilbrook, 2006 (see Bern- connected each other and more or less wide lacunae
ing et al. 2008), and that formed by Buffonellaria exist in between them. All these features allow a
Canù & Bassler, 1917 and Pourtalesella Winston, certain articulation or at least some constructional
2005 within the Celleporidae Johnston, 1838 (see flexibility to be attained. Consequently, colonies
Winston 2005, but also Berning & Kuklinsky are able to grow nearly flat, thus partly levelling
2008). Consequently, it could be suggested that the irregularities of the colonised surfaces, when
also Robertsonidra and Bertorsonidra n. gen., sharing encrusting rough substrata, and to cover surfaces
most of their characters and differing for the nature which are flexible or fleshy for the presence of soft
of their frontal walls belong to the same family. tissues possibly without being particularly dangerous
Nevertheless, as the genus Robertsonidra, including or lethal for the overgrown organism, due to their
at least seven species, mostly from the Indo-Pacific loose attachment. The presence of basal pillar-like
area (Bock 2002, but see above), had remained attachment structures is not exclusive of B. prenanti
systematically unplaced (see Tilbrook 2006: 261), n. comb. but has been observed also in similar,
the erection of a new family Robertsonidridae n. possibly related species, such as those belonging to
fam. is here suggested for accommodating both Robertsonidra (see Robertson 1908; Tilbrook 2006).
Robertsonidra and Bertorsonidra n. gen. The new Furthermore, comparable basal extensions are present
family shares some features, such as the concave in species of the Hiantoporidae Hiantopora and the
to widely sinuate primary orifice and the frontal Microporidae Mollia (Fig. 4B, AR pers. obs.), as
avicularia, with the Bitectiporidae MacGillivray, already observed by Gautier (1955) himself and
1895 (as reported by Hayward & Ryland 1999 and Berning (2006).
Ramalho et al. 2008) but differs for the ovicells with
calcified entoecium and ectooecium, which remain DISTRIBUTION
unfused. In contrast, although special studies aimed Bertorsonidra prenanti n. comb. is presently known
to describe ovicells in both genera are needed, both only from a restricted area in the present-day and
Robertsonidra and Bertorsonidra n. gen. seem to pos- past Mediterranean. Living specimens originate from
sess ovicells with an entirely uncalcified ectoecium the southern part of the western Mediterranean: the
and appear consequently comparable to those in colonies described by Gautier (1955, 1962) and
the family Schizoporellidae Levinsen, 1909, mostly recently listed by d’Hondt & Ben Ismail (2008) were
those of species belonging to the genus Schizoporella sampled at Castiglione (Algeria), and those herein
Hincks, 1877. described come from the Egadi Islands located West
of Sicily. Additional material is from off Tabarka,
FUNCTIONAL MORPHOLOGY western Tunisia (Harmelin, pers. comm., December
Colonies of B. prenanti n. comb. are loosely attached 2008). Noteworthy, the species is apparently absent
to their substratum through hollow, pillar-like struc- from the eastern side of Sicily (Ionian Sea), which
tures (Figs 3D; 4A), already described and figured by was extensively examined for bryozoans (Rosso
Gautier (1955: figs 7, 8), which emanate from the 1996a, b; Rosso et al. 2008, 2010 and pers. obs.) and
basal surfaces of each zooid. These structures, mostly other western Mediterranean localities (see Gautier
originating from the zooid periphery, elevate the 1962; Harmelin 1976), as also discussed by Zabala
basal surface of the colony some tens of micrometers (1986) and Zabala & Maluquer (1988). Similarly,
above the substratum leaving a fissure-space above no bryozoan review from the Adriatic (Novosel &
the algal tissue. Furthermore, it has been observed Požar-Domac 2001; Hayward & McKinney 2002)
that the length of the rhizoidal pillars changes seem- and the Aegean Sea (Harmelin 1968, 1969; Hayward
ingly to better adapt the relatively thick and large 1974) reported this species. Furthermore, all available
colonial modules (zooids can reach about 900 μm fossil specimens come from Sicily.
464 ZOOSYSTEMA • 2010 • 32 (3)
