ALBULIFORMES

Datovo, Aléssio & Vari, Richard P., 2014, The adductor mandibulae muscle complex in lower teleostean fishes (Osteichthyes: Actinopterygii): comparative anatomy, synonymy, and phylogenetic implications, Zoological Journal of the Linnean Society 171 (3), pp. 554-622 : 564-566

ALBULIFORMES

Description

Albula vulpes ( Fig. 7 )

The three primary sections of the segmentum mandibularis are relatively well differentiated, albeit with these sections partially continuous with each other along some areas of contact. The rictalis originates from the preopercle and quadrate and inserts on the posterior region of coronoid process of the anguloretroarticular. The posterodorsal portion of this section is mostly aponeurotic and covers a considerable part of the malaris. A small area of the rictalis has its fibres intermingling with the posteroventral region of the malaris. Anteriorly the rictalis is continuous with the stegalis.

The malaris arises from the hyomandibula and converges to the point of junction of the endomaxillar ligament with the mandibular tendon. In the two examined specimens, the malaris shows a partial differentiation into the retromalaris and promalaris from a medial view. The very conspicuous endomaxillar ligament attaches anteriorly to the anteromedial region of the maxilla.

The stegalis extends from the metapterygoid to the meckelian tendon, which is, in turn, completely separate from the mandibular tendon. The meckelian tendon continues anteriorly medial to the segmentum mandibularis to an attachment on the coronomeckelian.

The ramus mandibularis trigeminus nerve runs lateral to the segmentum facialis and transits between the coronalis (dorsally) and the ricto-stegalis (ventrally) in its passage to the lower jaw.

The coronalis extends posteriorly beyond the limits of the lower jaw and originates from the posterior portions of both the mandibular tendon and endomaxillar ligament in their area of confluence. This section inserts onto the dorsomedial surface of the portions of the dentary and angulo-retroarticular forming the coronoid process. The mentalis is posteriorly continuous with the coronalis but anteriorly is well separated from that section. The mentalis arises solely from the mandibular tendon and inserts on the dentary, anguloretroarticular, and Meckel’s cartilage.

Remarks

The morphology of the adductor mandibulae in Albula vulpes was previously described by Greenwood (1977) and Wu & Shen (2004). Both analyses recognized that the dorsal-most fibres of the muscle (= malaris) are associated with an endomaxillar ligament and partially separated from the remaining mass of the facial muscle ( Fig. 7 ). Only Greenwood (1977) attributed a distinct name (his A1β) to this portion of the muscle. No similar association of fibres with the endomaxillar ligament was reported for Pterothrissus . That genus consequently would have the entire segmentum facialis inserted solely on the lower jaw ( Greenwood, 1977).

The coronalis of Albula is well differentiated from the mentalis and posteriorly expanded, so as to be visible in a superficial lateral view ( Fig. 7 ). Owing to this degree of differentiation, Greenwood (1977) and Wu & Shen (2004) designated the mentalis as the Aω/Aw, whereas the coronalis was treated as part of the segmentum facialis. Pterothrissus was reported as having the coronalis conversely poorly separated from the mentalis and not posteriorly expanded. The entire segmentum mandibularis in this taxon was consequently identified as the Aω by Greenwood (1977).

Synonymy

Segmentum facialis

A2: Wu & Shen (2004): Albula .

Adductor mandibulae: Greenwood (1977): Pterothrissus .

Pars ricto-stegalis A2: Greenwood (1977): Albula .

Pars malaris A1β: Greenwood (1977): Albula .

Segmentum mandibularis Aω: Greenwood (1977): Pterothrissus .

Pars mentalis

Aω: Greenwood (1977): Albula .

Aw: Wu & Shen (2004): Albula .

Figures

Figure 7. Adductor mandibulae and associated structures of Albula vulpes (Albuliformes: Albulidae), LIRP 7427 (189.3 mm standard length). Left side in (A) lateral and (B) medial views; ramus mandibularis trigeminus nerve removed. Abbreviations: AM, adductor mandibulae; IA, intersegmental aponeurosis.