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Dorsal spines (total): 15-17; Dorsal soft rays (total): 9-11; Anal spines: 3-3; Anal soft rays: 7-9; Vertebrae: 24-26. Diagnosis: Thysochromis emili is distinguished from its West African congener, T. ansorgii, by the following combination of characters: fewer scale rows between the pectoral and pelvic-fin origins, 3-4 vs. 5-6; jaw teeth closely spaced and evenly implanted over entire length of both upper and lower jaws vs. widely spaced and unevenly implanted along distal portions; a supraoccipital crest that is continuous with the frontal ridge vs. terminating posterior to frontal ridge (Ref. 122428); a shorter postorbital length, 38.2-41.9% of head length vs. 42.8-46.7%; and a shorter caudal peduncle length, 7.7-11.3% of standard length vs. 11.4-12.7% (Ref. 122428).
Description: Deep-bodied, body depth 38.4-47.8% of standard length; greatest depth at level of fourth or fifth dorsal-fin spine (Ref. 122428). Head small, 34.2-38.9% of standard length, depth 65.0-76.8% of head length; short postorbital length, 38.2-41.9% of head length; snout short, mouth small with well developed, fleshy lips (Ref. 122428). Dorsal head profile 40-50° to mid-orbit, rising steeply to nape; dorsal and ventral body profiles convex to short, 7.7-11.3% of standard length; deep caudal peduncle, 15.6-18.5% of standard length (Ref. 122428). Jaws short and isognathous; outer row teeth in both jaws, somewhat recurved unicuspids, with distally flattened, bilaterally shouldered crowns; outer row premaxillary and dentary teeth evenly implanted, closely spaced over entire length of dentigerous arms, vs. widely spaced and unevenly implanted along distal portions in Thysochromis ansorgii; two to four inner rows of small, similarly shaped, unicuspid teeth restricted to anterior third of both jaws (Ref. 122428). Infraorbital series with broad, plate-like first infraorbital bearing four small, sensory-canal pores; second to fifth infraorbital elements narrow and tubular, forming complete suborbital ring (Ref. 122428). Lower pharyngeal jaw wider than long, with slightly convoluted ventral suture; 24-28 teeth along posterior row, symphysial teeth moderately robust, becoming slender laterally; 8-10 tuberculate ceratobranchial rakers along first arch, often short raker in angle of arch, 4-7 simple epibranchial rakers; microbranchiospines lacking on inner faces of second to fourth arches; pharyngeal hanging pad moderately developed, extending just anterior to first epibranchial (Ref. 122428). Dorsal fin with 15-17 spines and 9-11 rays; anal fin with 3 spines and 7-9 rays; dorsal spines increase in length posteriorly; soft dorsal and anal fins extending over caudal-fin base; caudal fin large, sub-truncate to rounded, with 14 branched rays; pectoral fins short and rounded, extending to mid-body, not reaching anus; pelvic fins reaching just short of, or to anus in females, extending beyond anal-fin origin in mature males; first branched ray of pelvic fin longest in both sexes (Ref. 122428). Scales cycloid; flank scales large, uniformly sized onto crest, 3-4 between pectoral and pelvic-fin origins; cheek with three scale rows, four horizontal scale rows on opercle; prominent dark opercular blotch unscaled; pored lateral-line scales 26-28, upper and lower lateral lines not overlapping, 17-20 scales on upper row, 6-9 scales on lower row; upper line separated from dorsal-fin base at highest point, eight pored scale, by 2-2.5 scales, last pored scale separated by 1-1.5 scales; proximal third of caudal fin covered with small interradial scales; 16, rarely 15, circumpeduncular scales (Ref. 122428). Total number of vertebrae 24-26, comprising 13 abdominal and 11-13 caudal centra (Ref. 122428). Supraoccipital crest contiguous with frontal ridge vs. crest terminating posterior to frontal ridge in Thysochromis ansorgii (Ref. 122428).
Colouration: Colouration in life: head and body yellowish or yellowish-brown, paler ventrally; scaleless, dark opercular spot often extending posteriorly over one or two scale rows; three short dark bars along mid-flank, not extending to ventrum; single dark bar or rounded spot in midline or over dorsal half of caudal peduncle; flank scales ringed with dark brown pigment contrasting with paler central field, more strongly marked in males than females; ventral portions of cheek, operculum and chest silvery with a greenish or turquoise flush; cluster of silvery scales located lateroventrally around vent, reduced in number and less clearly marked in males, prominent in mature females; belly flushed pale rosy pink in mature females; leading edge of pelvic fin darkly pigmented; soft dorsal and anal fins with alternating pale and dark maculae variously evident, but always present; caudal-fin membranes with conspicuous rows of maculae, strongest proximally; all fin spotting more prominent in mature males than in females and juveniles (Ref. 122428). In preservation, ground colouration of body brownish yellow, darker dorsally; opercular spot and bars on flank and caudal peduncle clearly visible, fin maculae variously evident (Ref. 122428). |