Minyclupeoides, Roberts, 2008

Roberts, Tyson R., 2008, Minyclupeoides Dentibranchialus, A New Genus And Species Of River Herring From The Lower Mekong Basin Of Cambodia (Teleostei: Clupeidae: Pellonulinae), Raffles Bulletin of Zoology 56 (1), pp. 125-127 : 125-126

Minyclupeoides , new genus

Type species. – Minyclupeoides dentibranchialus , new species.

Diagnosis. – Minyclupeoides has the anal fin entire, with no gap separating the last two rays from the preceding ones. In this and some other respects it agrees with the Southeast Asian pellonulin genus Clupeoides . It differs from Clupeoides in having the body entirely or almost entirely scaleless and numerous (instead of few) teeth on the maxillary bone. Other characters, some of them possibly diagnostic, include a single pored humeral scale on the body near the posterodorsal attachment of the opercle; pectoral and pelvic fin axillary scales absent; and a flattened or ventrally slightly concave sheath-like structure, not a modified procurrent ray or a modified scale, at beginning of upper and lower procurrent caudal fin rays. The latter structure, provisionally identified as a caudal scute, is longer and wider but thinner than the first procurrent caudal fin ray and lies superficially to it. Gill rakers denticulate, with numerous tiny conical teeth similar to those on the jaws (as in some other pellonulins).

Etymology. – The genus name Minyclupeoides is from the Greek “minys”, small, and Clupeoides , generic name of larger and fully-scaled riverine clupeids also inhabiting the Mekong Basin.

Remarks. – Recognition of a new genus primarily because of a single loss character is in some instances strongly contraindicated. Species in nearly all fish groups that become adapted to permanent life in caves almost invariably lose the eyes. It serves no useful purpose to recognize every species of cavefish as representing a distinct genus just because it has lost its eyes. Loss of the scales covering the body is relatively or extremely rare in most groups of teleosts that are normally fully scaled. It is sometimes associated with reduction in body size but by no means always. Total or near total loss of scales is relatively rare in clupeoid fishes. In Pellonulinae it is otherwise known only in the diminutive West African Thrattidion noctivagus Roberts, 1972 . Minyclupeoides differs from Thrattidion in many ways, including retention of a single scale in the humeral area. Thrattidion has retained a row or two of scales associated with the ventral scutes (for details see Whitehead, 1985: 163– 164) and has a complex termination of the lateral line with numerous short canals and pores but no scales instead of the single short canal and pore on one scale present in Minyclupeoides . Loss of all body scales except for a humeral scale present in Minyclupeoides is otherwise unknown among clupeoids.