MANINGRIDIDAE

Golding, Rosemary E., Ponder, Winston F. & Byrne, Maria, 2007, Taxonomy and anatomy of Amphiboloidea (Gastropoda: Heterobranchia: Archaeopulmonata), Zootaxa 1476, pp. 1-50 : 22

Family MANINGRIDIDAE fam. nov.

Diagnosis: Shell globose, small (known species up to 6 mm in diameter), fragile, pale golden, slightly reflective; whorls rounded, lacking shoulder; spire short and convex; umbilicus very narrow (almost closed), lacking umbilical folds; outer lip of aperture thin, with flattened, indented sinus. Operculum corneous, thin, circular, pale yellow; nucleus marginal on columellar edge, striae concentric; inner surface lacking projections around nucleus; operculum extended on outer edge to form thin, corneous sheath around expanded opercular lobe. Head lacking pigmentation in formalin-preserved specimens; tentacles broad, flat, semilunar with small post-tentacular lappets, eyes at outside base of tentacles. Foot unpigmented in formalin-preserved specimens, with large, balloon-like opercular lobe on upper surface of foot. Mantle cavity with short opposed ciliary tracts restricted to exhalant canal; mantle cavity roof lined with thin glandular coating; hypobranchial gland round, containing large mucus-filled chambers. Radula with central tooth bearing between 11 and 13 equal sized cusps, lateral teeth absent, approximately 15 marginal teeth on each side of radula, unicuspid, elongate and broad. Central nervous system slightly streptoneurous; cerebral and pleural ganglia abutting but separate, commissure not visible; presence of subcerebral and parapedal commissures unconfirmed; visceral loop long, visceral-parietal connectives thin, accessory ganglion absent. Reproductive system syntremous diaulic; ovotestis sac-shaped, not intertwined with digestive gland; seminal vesicle enlarged section of upper hermaphrodite duct; seminal receptacle single, spherical structure attached to carrefour by moderately long, coiled duct; spermoviduct divides below carrefour, non-glandular oviduct and vas deferens reuniting at genital atrium. Two accessory sperm transfer structures (copulatory organs) located at genital atrium; one clubshaped, with internal duct leading to blind-ending, bilobed gland; second structure elongate tube lined with spinous microsculpture leading to large prostatic gland via long, coiled duct with muscular bulb. Egg mass unknown.

Remarks: Characters of the shell, external anatomy, reproductive system, nervous system and radula support the creation of a new family for Maningrida arnhemensis sp. nov., described below. Features including the narrowly umbilicate shell, operculum with concentric growth lines and a marginal nucleus, head with flattened semilunar tentacles, expanded opercular lobe, streptoneurous visceral loop and entirely novel reproductive system including two copulatory organs of unknown function, set apart this taxon from other amphiboloideans and preclude its inclusion in either Amphibolidae or Phallomedusidae fam. nov.. However, the presence of an operculum and other features, notably the pneumostome, radular teeth and digestive system offer support for its inclusion in the Amphiboloidea.