Hoyle (1904) based his description of M. dentata on two specimens from the Eastern Tropical Pacific, neither had tentacles. One specimen (male, 72 mm ML, captured off Cape Mala, Panama), subsequently, was designated as the lectotype as the other has been lost (Young, 1972). Young (1972) reported additional features from a damaged specimen taken off Cape Mala.
- Arm suckers with teeth on distal half of inner ring (Hoyle, 1904); Distal half with long, pointed teeth blending into short, broadly truncate teeth proximally, 23 teeth total (Young, 1972, Cape Mala specimens, drawing on near right, bottom).
- Length apparently half of tentacle length (Young, 1972, examination of lectotype).
- Suckers in 35-40 series (Young, 1972, examination of lectotype).
- Largest suckers ca one third of club length from distal end (Young, 1972, Cape Mala specimens).
- Basal club suckers smaller and less thickly spaced (Young, 1972, examination of lectotype).
- Suckers decrease in size near lateral margins of club (Young, 1972, examination of lectotype).
- Club sucker circular, rings with virtually smooth inner margins.
- Outer rings of club suckers with 12-14 small pegs projecting slightly into aperature.
- Club sucker diameter 0.13-0.16 mm (P.L. 92 mm)
- Funnel locking-apparatus with tragus and weak antitragus; area of antitragus well undercut (Young, 1972, examination of lectotype).
- Tubercules absent.
- 43-67% of ML (Hoyle, 1904). 66-67% of ML (Young, 1972, Cape Mala specimens).
- Integumental photophores cover body (Young, 1972, based on lectotype).
- Eyelid photophore present (Young, 1972, examination of lectotype).
- Arms IV appear to have two series of photophores (see photograph below).
Source Hoyle, 1904 Mantle length 72 Mantle width 17 Head width 17? Fin length 48 Fin width 52 Arm I, length: Right / Left 37 / 38 Arm II, length 44 / 47 Arm III, length 45 / 42 Arm IV, length 87 / 78
Figure. Oral view of arm suckers of M. dentata. Left - Arm III, Cape Mala, lectotype. Drawing from Young (1972). Middle - Arm IV. Drawing from Hoyle (1904). Right - Oral view of proximal segment of the outer ring of an arm IV sucker. Drawing from Hoyle (1904).
Type locality: Gulf of Panama, off Cape Mala, Panama at 7°21'N, 79°35'W. The original description included two specimens, one from off Cape Mala and the other from near the Galapagos Isl. Since the Cape Mala specimen has been designated as the lectotype, its place of capture becomes the type locality.