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Dorsal spines (total): 13-13; Dorsal soft rays (total): 11-13; Anal spines: 3-3; Anal soft rays: 8-9; Vertebrae: 27-27. Diagnosis: A Ptychochromis with palatine morphology typical of species on Madagascar’s east coast (Ref. 105395). It is distinguished from all congeners by uniform dark brownish to black colouration in preservation and in life by expansive, continuous (or nearly so), longitudinal black blotch on midlateral flank extending from posterior margin of opercle to caudal peduncle versus absent in P. inornatus, P. onilahy, P. curvidens, P. loisellei, P. insolitus, or comprising multiple distinct midlateral blotches or bars in P. ernestmagnusi, P. makira, P. grandidieri, and P. oligacanthus (Ref. 105395). Ptychochromis mainty displays little or no overlap of anterior supraneural relative to supraoccipital crest, versus marked overlap in some eastern congeners like P. makira and P. ernestmagnusi; in comparison to P. grandidieri, body depth as a percentage of standard length in P. mainty considerably less for similarly sized individuals and slope of head in profile less steep; further distinguished from P. grandidieri by fewer and more sparsely arranged teeth on second pharyngobranchial toothplate of upper pharyngeal jaw, vs. numerous, densely arranged teeth (Ref. 105395).
Description: Shallow bodied, with elongated caudal peduncle; body overall convex in shape, most notably in dorsal profile; ventral margin between pelvic fin and vent nearly flat to slightly convex; prominent point along ventral margin at first anal spine due to moderate ventral sloping between vent and first anal spine and strong dorsal sloping along anal fin toward the caudal peduncle; profile of head flat and rising at roughly 40 degrees from midline; slight hump visible from supraoccipital crest in larger specimens (Ref. 105395). Vertebral count 27, with 14 pre-caudal and 13 caudal vertebrae (Ref. 105395). Oral jaws isognathous with dentition present across most of premaxillary arcade and covering about 2/3 of dentary; dentition distally expanded and bicuspid anteriorly; posterior teeth weakly bicuspid or flat, and rarely unicusped with pointed distal end; outer row of teeth larger than inner rows; three inner rows of teeth on anteriormost portion of dentary, reducing to single row of outer teeth posteriorly; up to four inner rows of teeth on anterior portion of premaxilla, reducing to single row of outer teeth posteriorly (Ref. 105395). Robust lower pharyngeal jaw, consisting of medially fused 5th ceratobranchials, with interdigitating suture uniting both halves; posteromedially, both lower pharyngeal jaw and upper pharyngeal jaw with enlarged molariform dentition; remaining dentition on lower pharyngeal jaw and upper pharyngeal jaw comparatively small and biscuspid, with well-developed posterior cusp and poorly developed anterior cusp; second pharyngobranchial toothplate with 3-4 rows of elongate, sparsely arranged hooked and biscupid teeth; presence of free second epibranchial toothplate; teeth on second epibranchial toothplate bicuspid, with one cusp strongly hooked and other cusp very poorly developed; non-molariform teeth on third pharyngobranchial toothplate, decreasing in size laterally, but increasing in intensity of hooked appearance; fourth upper toothplate with sparsely arranged hooked and bicuspid teeth that decrease in size and development toward plate’s outer margin (Ref. 105395). Gill rakers number 10 on lower limb of first gill arch, not including raker in angle of arch; tooth-bearing rakers present on lower limb of first gill arch; raker dentition conical with occasional weak curvature; Seven to eight elongate epibranchial gill rakers; rakers increasingly robust and with more numerous teeth from second gill arch to fourth (Ref. 105395). Flank squamation comprised of large, regularly imbricate, weakly ctenoid scales; anteriormost occurrence of ctenii near first dorsal spine and just posterior to pectoral fin base, and continuing posteriorly to origin of caudal fin; chest scales in larger specimens reduced in size and weakly embedded; embedded cycloid scales present on nape and head; cycloid scales present on opercle; preopercle asquamate; cheek scales cycloid, comprising up to four rows; anterior half of interorbital area, snout, anterior cheek and lachrymal asquamate; scales on caudal fin ctenoid at base, and become increasingly smaller, cycloid and embedded posteriorly; lateral line scales with well developed pores and numbering 28-31; four scales between pectoral and pelvic fin bases; five or six scales diagonally between dorsal-fin origin and upper lateral line; no scales extending onto dorsal- or anal-fin membranes (Ref. 105395). Dorsal fin with XIII spines and 11-13 soft rays; anal fin with III spines and 8-9 soft rays; first anal spine much shorter in length than the second and third; soft rays of dorsal and anal fins elongate, producing tapered appearance in both; anal-fin rays extend approximately to origin of caudal fin, although in 1 smaller specimen first three soft rays extend well posterior of caudal base; pectoral fin elongate, with rays increasing in length dorsally and extending posteriorly to anterior origin of lower lateral line; pelvic fin long and extending approximately to first anal-fin spine when adpressed, but more elongate in smaller specimen, extending to middle of anal fin; caudal fin emarginate, with somewhat rounded and equally sized upper and lower lobes (Ref. 105395). Infraorbital series comprising 7 elements; lachrymal with 4 pores; fourth pore directly adjacent to anterior pore of second infraorbital; second infraorbital expanded; second infraorbital excluded from margin of orbit by third infraorbital; first supraneural flattened dorsally and with little or no overlap with posterior portion of supraoccipital crest; second supraneural smaller than first or absent and more varied in shape, with forms either having anterior extension with flattened dorsal surface or no anterior projection; less developed or absent second supraneurals present in larger specimens; laterosensory laterosenory canals on dentary and preopercle well developed with large pores (Ref. 105395).
Colouration: In life, ground colouration light to dark olive green; one expansive longitudinal black blotch present on midlateral flank, and sometimes one or two smaller blotches also on caudal peduncle; primary blotch starting just posterior to opercle and continuous to caudal peduncle, but sometimes with break approximately at a vertical through anterior insertion of anal fin; this pattern contrasts with that of conspecifics, including P. ernestmagnusi, P. makira, P. grandidieri and P. oligacanthus, where several distinct midlateral blotches or bars are present; in individuals with darker ground colouration, ventral half of body has non-uniform yellow to greenish-yellow colouration; base colour of fins same as body; yellow colouration present on margin of dorsal fin, associated with distal portion of spines and sometimes also present on tips of soft rays; small patches of yellow colouration also present near distal ends of dorsal and ventral caudal fin rays; head colour uniform and same as base body colouration (Ref. 105395). Colouration in preservation: base colour of body dark brown, with ventral half just slightly lighter than dorsal; in smaller individuals ventral half of body pale brown and markedly lighter than dorsal half; darkest pigment occurs midlaterally and is most prominent directly posterior of opercle, although it does not contrast greatly with ground colouration of body; this darkened area corresponds to large, black midlateral blotch present in life; posterior half of lower jaw cream to light brown in colour; pectoral fin radials dark, but membrane cream coloured, giving fin a light overall appearance; some fading of pelvic fin at medial base, becoming light brown to nearly white in colour; anal fin slightly to mostly cream coloured near base posteriorly; vent clearly stands out from ventral margin of body and is white to cream in colour (Ref. 105395). |