This species is distinguished all its congeners, except M. affinis, M. australis, M. glutinosa, M. limosa, M. hubbsi, M. hubbsoides, M. jespersenae, M. knappi, M. kuoi, M. mcmillanae, M. paucidens, M. sotoi, M. greggi, by having 6 pairs of gill pouches and a 2/2 multicusp pattern of teeth; differs from these congeners by the number of total cusps 34 (vs. 38-46 in M. affinis, 38-44 in M. jespersenae, 30-32 in M. kuoi, 42-48 in M. mcmillanae, 26 in M. paucidens, 34-44 in M. sotoi); prebranchial pores 26-27 (vs. 30-31 M. hubbsoides, 28-37 in M. jespersenae, 30-38 in M. knappi, 28-38 in M. sotoi); trunk pores 52-54 (vs. 57-79 in M. affinis, 57-73 in M. hubbsi, 68-71 in M. hubbsoides, 57-58 in M. kuoi, 60-76 in M. mcmillanae, 61-73 in M. sotoi, 58-66 in M. greggi); total pores 91 (vs. 94-124 in M. affinis, 111-116 in M. hubbsoides, 107-121 in M. jespersenae, 98-126 in M. knappi, 95-100 in M. kuoi, 101-113 in M. mcmillanae, 101-119 in M. sotoi); and by having one single conspicuous nasal sinus papilla in the mid-dorsal surface of the nasal sinus (vs. two bilaterally symmetrical nasal-sinus papillae in M. jespersenae); differs further from its congeners with six-gill pouches by its colour pattern, with body dark brown and white head (vs. body entirely pigmented, without white head, in M. affinis, M. australis, M. hubbsoides, M. knappi, M. kuoi, M. paucidens); differs further from M. greggi and M. hubbsi by having a white ventral finfold (vs. same colour or darker than body); the gill aperture on the left side is not confluent with the pharyngocutaneous duct aperture, but separated by a very short distance (c. 1 mm) (Ref. 123790).