Auricellina, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Genus AURICELLINA gen. nov.

Di Martino, Rosso and Taylor zoobank.org/ 9D103D7B-EB39-4509-BB3D-61D990BDABB7

Type species. Auricellina biserialis gen. et sp. nov. Di Martino, Rosso and Taylor.

Etymology. Latin, prefix meaning ear, referring to the position of the paired pore areas flanking the orifice, and suffix meaning small cell, commonly used in bryozoan genus names.

Diagnosis. Colony erect, jointed, branching. Internodes uni- to biserial, uni- to multizooidal. Autozooids claviform, narrowing proximally. Frontal shield largely gymnocystal, smooth, with no costae or foramina. Orifice monomorphic, transversely Dshaped with a shallowly concave proximal margin, centrally interrupted by a short suture. Two symmetrical, large, slightly depressed, drop-shaped, cryptocystal pore areas (vittae) flanking the orifice and extending proximally beyond it, with sparse, minute, circular pores; additional smaller pore areas possibly present on the sides or the back. Ovicell subimmersed, elongate, occupying the caudal and one-third of proximal portion of the distal zooid; ooecium frontally flat, sometimes developing a median longitudinal carena, and with an ectooecial slit-like fissure on its proximal third, placed medially, extending horizontally, slightly arched, sometimes closed centrally and separated into two openings of different sizes and shapes obliquely oriented; ooecial opening quadrangular, likely not closed by zooidal operculum. Avicularia not observed, seemingly lacking.

Remarks. Gordon (1993) described a new species of the catenicellid genus Talivittaticella Gordon and d’Hondt, 1985 , namely T. nuda Gordon, 1993 , from Mindoro Strait, Philippines, at depths of 92– 97 m. He noted that although no other genus could accommodate this species, it was very unusual among species of Talivittaticella in lacking costae and foramina. However, the small suture on the proximal margin of the orifice suggested a relationship with species having a costate shield. The absence of an ovicell in Gordon’s specimens prevented further taxonomic action at that time.

Our study of the present material, though limited to a single internode, allowed for the observation of the ooecium. As in other Catenicellidae (e.g., Pterocella Levinsen, 1909 ), the fertile zooid develops as part of a complex that includes the ovicell and the distal zooid (Ostrovsky, 2013). The distinctive feature of the ooecium is a slit-like ectooecial fenestra, which can calcify over to form two smaller windows. This unique characteristic distinguishes this genus not only from Talivittaticella but also from other genera of Catenicellidae . In other Catenicellidae , the ectooecium is completely or partially uncalcified, leaving numerous small windows or a few (one or two) large fenestrae, through which the endooecium is visible. The endooecium can vary from smooth, to reticulate, finely porous, spinous or a combination of these patterns.

Differences between this new genus and other genera in the family extend beyond the ooecium. Here, we briefly highlight the most salient distinctions.

Calpidium Busk, 1852 View in CoL and Claviporella MacGillivray, 1887 View in CoL , have a keyhole-shaped orifice and costate frontal shields. Costate frontal shields are characteristic of Costaticella Maplestone, 1899 View in CoL , Pterocella View in CoL and the fossil genus Costatimorpha Zágoršek, 2003 View in CoL , as well as Digenopora Maplestone, 1899 View in CoL . Additionally, Calpidium View in CoL has a frontal shield with multiple gymnocystal regions separated by ridges, and has terminal ovicells and dimorphic fertile zooids. This latter feature is also found in Cornuticellina Stach, 1935 View in CoL and Strophipora MacGillivray, 1895 View in CoL . Claviporella View in CoL and Strophipora View in CoL also have frontal shield with a median suture and an uncalcified central opening.

Catenicella Busk, 1852 View in CoL , Cornuticella Canu and Bassler, 1927 View in CoL , Scalicella Harmer, 1957 View in CoL and Terminocella Harmer, 1957 View in CoL have vittae along the lateral margins, rather than on the side of the orifice. In Catenicella View in CoL , avicularia are frequent, while in Cornuticella View in CoL , the distal compartments of autozooids develop into long spinose processes. Cribricellina Canu and Bassler, 1927 View in CoL and Paracribricellina Wass and Yoo, 1976 View in CoL have densely and evenly porous gymnocysts and also fertile zooid with enlarged dimorphic orifice. In Cribricellina View in CoL , the ooecium has numerous radially arranged pores, while Paracribricellina View in CoL has a deep, wide ectooecial fenestra exposing the endooecium, which can be finely porous, smooth, or papillate. Orthoscuticella Wass and Yoo, 1975 View in CoL has several windows on the frontal shield and dimorphic fertile zooids, in addition to an orifice with a small central notch. Scuticella Levinsen, 1909 View in CoL has large windows in the gymnocyst unequal in size, and dimorphic fertile zooids with an ectooecium calcified only proximally and a largely exposed endooecium, which is spinous and porous with pores organized in a V-pattern. Strongylopora Maplestone, 1899 View in CoL and Vasignyella Gordon, 1989a View in CoL have numerous windows in the frontal gymnocyst, mainly confined to the lateral margins in Strongylopora View in CoL , but extending centrally in one species of Vasignyella View in CoL . The distal corners can develop to different extents into spinose processes, but they always bear avicularia.

Despite T. nuda View in CoL lacking ovicells, the consistent presence of certain features (e.g., pore areas adjacent to orifice and their shape) and absence of others (e.g., costae and foramina) warrant the introduction of a new genus to encompass this species and the new species described here. Therefore, we propose the new combination Auricellina nuda (Gordon, 1993) comb. nov.

The differentiation between genera with uni-, bi-, and trizooidal segments versus those with segments comprising more than three autozooids (i.e., multizooidal) has traditionally been a key feature for distinguishing genera in the subfamilies Catenicellinae Stach, 1935 and Ditaxiporinae Stach, 1935 (Gordon and Braga, 1994; Vieira et al., 2007). However, this new genus includes one species with uni- to bizooidal internodes and another species with multizooidal segments. This variability is also seen in Vasygniella, which can have both uniserial chains of unizooidal internodes and biserial multizooidal internodes, with ovicellate zooids always occurring in multizooidal internodes ( Vieira et al., 2007). This suggests that if infertile internodes of the newly described species A. biserialis gen. et sp. nov. (see below) were found, they could be uni- or bizooidal, while fertile segments of A. nuda comb. nov. might be multizooidal.

The new genus differs also from other genera within the subfamily Ditaxiporinae . Bryosartor Gordon and Braga, 1994 has a costate frontal shield, a largely uncalcified ectooecium, granular endooecium, and avicularia. Caberoides Canu, 1908 has a dorsal side with vibracular-like chambers. Ditaxipora MacGillivray, 1895 and Ditaxiporina Stach, 1935 have keyhole-shaped orifices and distolateral avicularia. Ditaxipora additionally has a frontal shield largely occupied by vittae, while Ditaxiporina has numerous gymnocystal windows. Plagiopora MacGillivray, 1895 also has an elongate orifice, typically paired distolateral avicularia, and vittae on the frontal side that are continuous with those on the dorsal side.