SALMONOIDEI
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publication ID |
https://doi.org/ 10.1111/zoj.12142 |
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persistent identifier |
https://treatment.plazi.org/id/03DB6116-5318-A23C-FE1D-D2AC26887A22 |
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treatment provided by |
Marcus |
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scientific name |
SALMONOIDEI |
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Description
Oncorhynchus mykiss ( Fig. 26 View Figure 26 )
The rictalis and malaris are continuous with each other at their origins, which involve the quadrate, symplectic, preopercle, and hyomandibula. As the muscle continues anteriorly, the rictalis and malaris become differentiated along their lateral surfaces. Both of these sections insert on the mandibular tendon, which is much shorter medially and becomes laterally continuous with a mandibular raphe shared with the segmentum mandibularis.
The stegalis is partially differentiated into an epistegalis and a substegalis. The latter muscle section is largely continuous with the ricto-malaris but is distinguished, albeit only to a slight degree, at its origin by its shorter fibres that arise from the metapterygoid. The substegalis converges onto the ventral portion of the intersegmental aponeurosis formed jointly by the meckelian and accessory tendons. These tendons are only partially separated from each other and both attach ventrally to the coronomeckelian. The epistegalis originates from the metapterygoid and hyomandibula and is separated dorsally from the ricto-malaris. Insertion of the epistegalis is onto the medial regions of the much shortened mandibular tendon.
The segmentum mandibularis is posteriorly differentiated into a coronalis and a mentalis. The coronalis originates from the lateral surface of the mandibular tendon and the dorsal portion of the mandibular raphe, both of which serve as insertion sites for the malaris. The mentalis, in turn, arises from the ventral portion of the mandibular raphe and the medial surface of the mandibular tendon, which serve as insertion sites for the epistegalis and rictalis. Towards their insertions, the coronalis and mentalis become continuous with each other and attach jointly on the dentary, anguloarticular, and Meckel’s cartilage.
The ramus mandibularis trigeminus nerve runs along the lateral face of the segmentum mandibularis and then traverses the segmentum mandibularis between the coronalis and the mentalis.
Remarks
Both the segmenta facialis and mandibularis of salmonoids were previously reported as largely undivided ( Greene & Greene, 1913; Edgeworth, 1935; Van Dobben, 1935; Lauder & Liem, 1980; Williams, 1987; Sanford, 2000; Wu & Shen, 2004). Although these segments in Oncorhynchus mykiss indeed mostly lack subdivisions, all of the primary facial sections typical of the Teleostei are readily recognizable in this species. That said, the degree of differentiation of the sections is often admittedly tenuous ( Fig. 26 View Figure 26 ). Incipient degrees of differentiation are also indirectly indicat- ed in the literature information. Although Sanford (2000) reported that the segmentum facialis in all salmonoids lacks any medial division, the accompanying illustration ( Sanford, 2000: fig. 92) shows a distinct medial set of fibres in Salmo that converges onto a tendon inserted on the coronomeckelian (= the meckelian tendon). This medial facial portion was labelled as the A2(M), which seems equivalent to the stegalis, and the lateral muscle portion as the A2(L), which apparently corresponds to the ricto-malaris. Sanford (2000) also recognized a lateral differentiation between the malaris and rictalis in Stenodus (his A2α and A2β sections, respectively), an arrangement similar to that in Oncorhynchus mykiss ( Fig. 26A View Figure 26 ).
In most salmonoids the ricto-malaris is connected solely with the segmentum mandibularis via the mandibular tendon and raphe. However, in some taxa a few fibres of the ricto-malaris insert directly on the coronoid region of the lower jaw and/or the retrojugal lamina ( Williams, 1987; Sanford, 2000).
Apparently all salmonoids have a medially much shortened mandibular tendon ( Fig. 26B View Figure 26 ) that is transformed laterally into a mandibular raphe ( Fig. 26A View Figure 26 ; Edgeworth, 1935; Lauder & Liem, 1980; Williams, 1987; Sanford, 2000; Wu & Shen, 2004). In most genera, the mandibular raphe and consequently the posterior portion of the segmentum mandibularis extend posterodorsal to the limits of the lower jaw ( Williams, 1987; Sanford, 2000).
Synonymy
Segmentum facialis
A 2: Van Dobben (1935): Salmo .
A2: Sanford (2000): Brachymystax , Coregonus , Hucho , Oncorhynchus , Prosopium , Salmo , Salvelinus , Stenodus , Thymallus ; Williams (1987): Brachymystax , Coregonus , Oncorhynchus , Prosopium , Salmo , Salvelinus , Stenodus , Thymallus .
A 2 A 3: Lauder & Liem (1980): Salvelinus .
A2β: Wu & Shen (2004): Oncorhynchus .
Adductor mandibulae: Edgeworth (1935): Salmo .
Cephalic division: Greene & Greene (1913): Oncorhynchus .
Pars rictalis
[At least the lateral part of] A2β: Sanford (2000): Stenodus .
Pars malaris
[At least the lateral part of] A2α: Sanford (2000): Stenodus .
Pars ricto-malaris A2(L): Sanford (2000): Salmo .
Pars stegalis A2(M): Sanford (2000): Salmo .
Segmentum mandibularis
Aw: Lauder & Liem (1980): Salvelinus .
Aw: Sanford (2000): Brachymystax , Coregonus , Hucho , Oncorhynchus , Prosopium , Salmo , Salvelinus , Stenodus , Thymallus ; Williams (1987): Brachymystax , Coregonus , Oncorhynchus , Prosopium , Salmo , Salvelinus , Stenodus , Thymallus ; Wu & Shen (2004): Oncorhynchus .
Intramandibularis: Edgeworth (1935): Salmo .
Mandibular portion: Greene & Greene (1913): Oncorhynchus .
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