Parvamussium catillus Dijkstra & Maestrati 2015, sp. n.
Creators: name: Dijkstra, H. H.
name: Maestrati, P.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Bivalvia
Pectinida
Propeamussiidae
Parvamussium
Parvamussium catillus

description: Parvamussium catillus sp. n.   
Fig. 2A–G  
 Etymology: From the Latin catillus (m.) (small dish), after the smooth circular shell that resembles a small dish.   
 Description: Shell up to 7.2 mm in height, fragile, semi-transparent, circular, inequivalve, left valve slightlY more inflated than right valve, equilateral, auricles almost equal in size, umbonal angle 110°–115°, colour whitish. Prodissoconch 100 µm long. Left valve smooth and dead throughout shell disc, umbonal part glossy and transparent. Anterior auricle with very weak and delicate widely spaced commarginal lamellae, more prominent near shell disc, posterior auricle almost smooth with traces of very closely spaced commarginal lirae laterally. Right valve with weak, regularly spaced, commarginal lirae (c. 8 per mm).Anterior auricle with weak and verY fine commarginal lirae and a noduliferous ridge along the byssal fasciole, posterior auricle continuous with disc, smooth with very close-set commarginal lirae laterally. Byssal notch moderately deep, byssal fasciole rather small, no ctenolium. Hinge line straight. Resilifer triangular. Internal ribs 13 commence in early growth stage and are exposed almost to the periphery, one interstitial rudimentary riblet antero-ventrally, and one riblet on both auricles.   
Dimensions (holotype): Height 7.2 mm, width 7.2 mm, convexity 2.5 mm.  
 Type material: Holotype (pr) (MNHN IM-2007-41966), paratype (pr) (MNHN IM-2007-41964). Type locality: MOZAMBIQUE CHANNEL: Inhambane transect (23°35'S 36°06'E), - 1092–1195 m, live, campaign Mainbaza, stn CP3139, RV Vizconde de Eza, leg. P. Bouchet, J. Rosado & E. Strong, 11.iv.2009.   
Distribution and habitat: See type locality.  
 Remarks: The closest resembling species is Parvamussium multiliratum Dijkstra, 1995, recorded from New Caledonia, Vanuatu, Fiji, Tonga, Wallis and Futuna (Dijkstra & Maestrati 2012: 392). Parvamussium catillus morphologically differs from P. multiliratum by a smooth shell disc of the left valve (P. multiliratum with prominent commarginal lamellae and weak radial sculpture postero-laterally), by having fewer interior ribs (P. multiliratum 14 and two rudimentary).   
 Another somewhat resembling species is Propeamussium arabicum Dijkstra & Janssen, 2013, recorded from the Gulf of Aden and herein also from northwestern Madagascar and the Mozambique Channel. This species is also circular in shape, but larger sized (up to 14.9 mm in height, P. catillus up to 7.2 mm) and has a fine reticular sculpture on the left valve (P. catillus smooth). Moreover, fewer internal ribs (7 without rudimentary, P. catillus 13 and one rudimentary).
description: Published as part of Dijkstra, H. H. & Maestrati, P., 2015, Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean, pp. 585 in African Invertebrates 56 (3) on pages 599-601, DOI: 10.5733/afin.056.0307, http://zenodo.org/record/7914533