Raninidae De Haan, 1839

Van Bakel, Barry W. M., Guinot, Danièle, Artal, Pedro, Fraaije, René H. B. & Jagt, John W. M., 2012, A revision of the Palaeocorystoidea and the phylogeny of raninoidian crabs (Crustacea, Decapoda, Brachyura, Podotremata) 3215, Zootaxa 3215 (1), pp. 1-216 : 87-89

Family Raninidae De Haan, 1839 emend.

Raninidae De Haan, 1839: 102 .

Included subfamilies. Cyrtorhininae Guinot, 1993b (see below), Notopodinae Serène & Umali, 1972 , Raninoidinae Lőrenthey in Lőrenthey & Beurlen, 1929, Ranininae De Haan, 1839 , and Symethinae Goeke, 1981 (see below).

Type genus. Ranina Linnaeus, 1758 .

Diagnosis. Carapace elongated to oval, rounded, widened anteriorly; convex in transverse direction; may be roof shaped, with medial carina. Dorsal surface smooth, pitted, granular, inclined or fungiform nodes, eroded, scabrous or terraced; cervical groove generally indistinct, branchiocardiac grooves present. Anterolateral margin armed with 1‒3 teeth, which may be broad, or long, bifurcate, spinose, or small, blunt. Posterolateral margin long, often rimmed. Front generally triangular or subtrapezoidal, pointed, may be trifid, or replaced by V-shaped emargination. Orbitofrontal margin narrow to conspicuously wide. Supraorbital margin with 1 or 2 closed or open fissures, lined with granules, spinules or armed with teeth; extraorbital tooth generally produced, may be broad, bilobate. Orbits directed anteriorly or anterolaterally, narrow to wide. Eyestalks short to long, composed of 1‒3 calcified articles, bent at angle to one another when retracted into orbit.

Antennules, antennae rather stout; antenna not folded, inserted somewhat below antennule; antennules, antennae modified in connection with respiratory currents. Proepistome concealed; epistome short; endostome large, produced; strongly excavated. Pterygostome large, tumid, subantennary lobe well defined. Buccal frame large, with broad collar. Mxp3 strongly elongated, operculiform, endopod often grooved.

Thoracic sternum wider anteriorly, conspicuously narrow posteriorly, strongly deflected at different levels. Sternite 3 crown shaped (compressed in Cyrtorhininae ); sternite 4 usually wide, flat (narrow in Cyrtorhininae ); suture 4/5 crescent shaped; sternite 5 expanded laterally; sternite 6 smaller, wide anteriorly, restricted between P3 coxae; sternites 6‒8 conspicuously narrow. Medial line present along posterior sternites, running up to sternite 5 or 6. Sternum/pterygostome junction present, narrow to large. Junction sternum/exposed pleurites present between P1, P2 and between P2, P3, or only between P1, P2 ( Notopodinae ). Pleurites 5‒7 partially exposed (gymnopleurity), calcified, forming polished surface, generally excavated, concave. Spermathecal apertures various: opening anteriorly, within sternite 7; generally close to each other, recessed in medial depression (more superficial, wider, hooded in Symethinae ).

Absence of sterno-abdominal cavity. Abdomen short, incompletely folded, 6 freely articulated somites plus small telson; somites smooth; first somites dorsal, in prolongation with carapace, relatively wide in male, not much enlarged in female, thus sexual dimorphism relatively indistinct. Uropods or sockets absent; absence of abdominalholding structures.

Chelipeds homochelous, homodontous; arthrodial cavities large, placed laterally. Basis-ischium short, immoveably fused with long merus; propodus short, inflated, flattened, armed with long, sharp spines on upper and lower margins, or elongated, narrow, unarmed; fingers usually with teeth of prehensile borders joining alternatively, unarmed (several long, sharp spines in Cyrtorhininae ); fixed finger short to long, may be strongly deflected. Arthrodial cavities of P2‒P4 almost ventral; those of P5 only, or both P4, P5 subdorsal. Carpus, propodus, dactylus flattened; dactylus variously modified: flattened, paddle shaped, lanceolated, or falciform. P5 weakly to strongly reduced, dorsal or subdorsal in position, usually fitting posterolateral border of carapace.

Respiratory mechanism highly specialised. Absence of Milne-Edwards openings; strongly modified frontal region, antennules, antennae modified for inhalant current; posterior branchial orifices generally present, or absent ( Notopodinae ).

Remarks. Included in Raninidae are those raninoidean crabs that are markedly modified by their burying behaviour, thus with peculiar respiratory properties and having lost abdominal holding, in contrast to Lyreididae . The Cyrtorhininae and Symethinae are here tentatively placed in Raninidae awaiting the revision of the Raninoidea by M. Tavares.