Antarctophiline malaquiasi Peralta-Serrano, Schrödl, Wilson & Moles, 2025, sp. nov.

Antarctophiline malaquiasi sp. nov. Diagnosis Body oval, large, arched in sagittal plain, white or ivory coloured. Cephalic shield oval. Shell internal, subquadrate, slightly angled dorsally, flattened. Radular formula 12 × 2.1.0.1.2. Gizzard plates (3) elongated, oval, ventral plate smaller than dorsal ones; internal surface, chitinous, slightly convex on one side, holes or slits absent, with concentric amber and dark brown bands; external surface highly convex, sometimes asymmetrically pointy dorsally. ZooBank registration urn:lsid:zoobank.org:act:963E806A-B353-472D-A3E9-29D690- CB00B7. Etymology This species is named in honour of Dr Manuel António E. Malaquias for his contribution to the systematics of cephalaspidean molluscs. Type locality Bransfield Strait, 150–247 m depth. Material examined Bransfield Strait, St. BS 1/86, 62 ○ 52 ′ 20.7 ′′ S, 57 ○ 11 ′ 32.5 ′′ W, 150–247 m depth: 2 specimens, sequenced and dissected, SIO-BIC M17786 (holotype; 24 October 2011), L = 9.6 mm, W = 5.4 mm, COI barcode MN486290, SIO-BIC M17787 (paratype; 24 October 2011), L = 6 mm, W = 4 mm. External morphology (Fig. 7a) Body oval, arched in sagittal plane; maximum L = 8 mm, W = 4.5 mm, white or ivory coloured; surrounding translucent white thin mantle. Cephalic shield oval, half of body extension, slightly over shell; central grove slightly marked, last two-thirds extension. Parapodia triangular, slightly extended over shell; gill visible from above. Foot smooth, extending from mouth approximately three-quarters of the animal. Shell (Fig. 7b) Maximum L = 6.6 mm, W = 5.3. Internal, subquadrate, white, thin, slightly angled dorsally, flattened. Periostracum thin, pellucid. Aperture almost full extension of shell, with thin, parietal callus. Outer lip straight, in right angle on posterior side. Columellar wall concave. Apex superficial, umbilicated, left-sided. Growth lines marked. Radula (Fig. 7c) Radular formula 12 × 2.1.0.1.2. Rachidian not detected. Lateral teeth hook-shaped, inner lateral thick, with broad base, tip rounded, inner edge without denticulation. Outer lateral teeth hook-shaped, with broad base, tip rounded or pointed. Digestive tract (Fig. 7e) Buccal mass highly muscular. Salivary glands short, entering pharynx from posterior end, extending over crop to beginning of gizzard. Crop globose, saccular, thin walled. Gizzard elongated, surrounded by circular muscle fibres. Gizzard plates (3; maximum L = 1.5 mm, W = 0.6 mm) elongated, oval, symmetrical; internal surface chitinous, slightly convex on one side, holes or slits absent, with concentric amber and brown bands; external surface highly convex, sometimes asymmetrically pointy dorsally (Fig. 7e,f); spines present in gizzard (Fig. 7d). Male reproductive system (Fig. 7g,h) Penial sheath short, pyriform. Penial papilla small. Ejaculatory duct surrounded by musculature tissue. Prostate granulose, saccular, shorter than penial sheath, displayed attached to seminal vesicle. Seminal vesicle saccular, semitranslucent, slightly bigger than prostate, containing autosperm. Ecology Found between 150 and 247 m depth. Sponge spicules, diatoms and foraminifera were found in the gut contents of the single specimen dissected in this study (Fig. 5g –i). Distribution Only known from the Bransfield Strait. Remarks Although not closely related phylogenetically to A. alata and A. gibba, the new species can hardly be differentiated from them externally. Only the shape of the gizzard plates, being highly convex and pointy dorsally, and a slightly more rounded shell are differential characters compared to the ones from A. alata and A. gibba. These are characters subject to intraspecific variation, thus more specimens are needed to further explore these differences. Unfortunately, only two specimens have been collected so far. Its known distribution also seems to overlap with A. alata and A. gibba, matching the same bathymetrical distribution, indicating that this species may coexist in the same locality.