大西洋から報告されている本属魚類5種類中,肛門前側線孔数が40以上の種は本種とR. polyporaに限られる。R. polyporaでは眼の後縁に沿い3個の感覚孔が開く(Smith and Kanazawa, 1977)。 (上野・佐々木)
Distinctive characters:
Mouth inferior. Eye 2/3 of snout. Anus situated in front of mid-body, total length 2.5〜2.7 times of preanal length. Number of preanal lateral line pores 41〜44. Dorsal and anal fin rays segmented. Dorsal fin inserted slightly behind gill-opening. Labial flange present only on lower jaw. Posterior nostril in front of eye. No postorbital pores. Teeth conical and pointed; teeth on maxillary and dentary 3 rows anteriorly, 2 rows posteriorly; teeth on premaxillary rather large and canine-like; teeth on vomer in several rows and restricted to anterior part of mouth, the middle row teeth larger than those on side rows; some canine-like teeth present along the front margin of lower jaw. Margins of vertical fins black.
Distribution:
Gulf of Mexico to mouth of the Amazon.
Remarks:
Among the 5 known species of the genus from the Atlantic, the present species and R. polypora are characterized in having more than 40 preanal lateral line pores; R. polypora has 3 postorbital pores (Smith and Kanazawa, 1977). (Uyeno and Sasaki)