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Diagnosis: Monopterus luticolus is assigned to the 'Amphipnous group' within the genus Monopterus based on the presence of a unique synapomorphy of the group: the spatial dissociation of ceratobranchial 1 from hypobranchial 1 and its close association with hypobranchial 2 and ceratobranchial 2 (Ref. 116049). It is distinguished from all other species of synbranchids, including the other African synbranchids Ophisternon afrum and Monopterus boueti, by having more vertebrae, 198-208 vs. 100-194 (Ref. 116049). It is further distinguished from all synbranchids except O. infernale, O. candidum, M. boueti, M. eapeni, M. roseni, and M. digressus by the lack of externally visible eyes; Monopterus luticolus is also readily distinguished further from the African synbranchid species O. afrum by having the posttemporal greatly reduced in size and removed spatially from the supracleithrum and cleithrum, as well as from the skull, vs. posttemporal large, articulating with supracleithrum and epiotic of skull; and by having five vs. six branchiostegal rays (Ref. 116049). Monopterus luticolus is most similar to the West African M. boueti, from which it differs by having fewer abdominal vertebrae, 95-101 vs. 108, and more caudal vertebrae, 98-110 vs. 79-86; it differs further from M. boueti by several osteological characters (Ref. 116049).
Description: Extremely slender, eel-like body, body depth 63-79 times in preanal length and body width 1.1-1.7 times in its depth; highest and widest part is at level of middle of head, tapering gradually posteriorly to whip-like tail and anteriorly to wide blunt snout (Ref. 116049). Head with bulging adductor muscles resulting in hump-like swelling in larger, and less pronounced bulging in smaller specimens; eye invisible externally; anterior naris at tip of snout, posterior naris situated right in front of bulging adductor muscles; gill opening greatly restricted to tiny crescentic orifice in ventral midline (Ref. 116049). Fins and scales absent (Ref. 116049). Vertebrae: 198-208 total number, 95-102 abdominal and 98-110 caudal vertebrae (Ref. 116049).
Colouration: In alcohol, body a uniform pale brown along dorsum and upper two thirds of sides, white on belly (Ref. 116049). In life, uniformly maroon, with some visible blood vessels particularly in upper body (Ref. 116049). |