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Left, lateral view of the cheek and ventral head musculature of Naso lituratus, 107 mm SL, ROM uncat. AAP, adductor arcus palatini; ABP, abductor profundus; ABS, abductor superficialis; HYIN, hyohyoides inferioris; PRHY §1, §2, §3, protractor hyoidei; STHY, sternohyoideus. Other abbreviations as in Fig. 1. Scale 1 cm.
Source publication
Striated muscles of 15 species of unicornfishes (Naso, Acanthuridae) are described in detail. Of 93 muscles dissected, only five demonstrate intrageneric variation, providing only ten characters suitable for phylogenetic analysis. Thus, myology appears to be highly conservative at the species level and has been so for approximately 50–55 million ye...
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... tissue deposits. Its origin is the lateral ethmoid and preorbital ligament that connects the anterodorsal surface of the hyomandibular and lateral ethmoid ( Fig. 1). The muscle tapers anteriorly, inserting on the anterolateral margin of the maxilla by means of a single, tendinous sheet, with ventral fibers attaching to the ligamentum primordium (Figs. 1-3). Intrageneric variation occurs in the relative length of the insertional tendon of A1 occupying the maxilla (Table ...
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... A2 is dorsal to A2; both sections are ventral to A1. The origin of section A2 is the anterodorsal surface of the hyomandibular at the anteroventral corner of the orbit (Figs. 1, 3). The insertion is tendinous on the medial side of the dentary and may include the ligamentum primordium (Fig. 1). ...
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... Naso lituratus and N. unicornis, fibers of A1 and A2 do not intergrade, and no identifiable part of the ligamentum primordium is visible in lateral view (Fig. 3). The ligamentum primordium is either reduced or is so closely associated with the insertional tendon of A2 that it is not discernible. The only identifiable part of the ligament may be the posteriormost end that is tentatively identified as a nonmuscular connection between A1 and A2 posterior to the origin of A1. Unique to these two ...
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... it passes through the cheek musculature, A2 and A2 do not intergrade and are thus easily divisible. A2 originates from the anterodorsal surface of the hyomandibular, lateral surface of the metapterygoid adjacent to the hyomandibular and posteroventral corner of the quadrate adjacent to the hyomandibular (Figs. 1, 3). Its insertion is tendinous on the medial side of the angular, dorsoanterior to the Meckelian fossa (Fig. 5). ...
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... levator arcus palatini is conical, its apex dorsally directed, and forms the posteroventral wall of the orbit connecting the neurocranium and suspensorium (Figs. 1, 3, 6). It originates from the ventral and posterior surfaces of the sphenotic and inserts on the dorsal surface of the hyomandibular, lateral faces of the hyomandibular heads articulating with the neurocranium and dorsal surface of the hyomandibular immedi- ately ventral to the sphenotic process. ...
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... dilatator operculi is also conical, but its apex is ventrally directed and connects the neurocranium and opercle (Figs. 1, 3). It is bordered anteriorly by the levator arcus palatini and posteriorly by the levator operculi. ...
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... levator operculi connects the neurocranium and suspensorium. It originates from the pterotic (Figs. 1, 3) and inserts on the medial side of the posterodorsal surface of the opercle (Fig. 7). It is composed of two bundles, near equal in size, that intergrade and are only weakly separable (Winterbottom, '93). ...
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... adductor arcus palatini is a thick muscle connecting the neurocranium and suspensorium. It extends anteriorly from the level of the nasal rosette posteriorly to the prootic but not attaching to it (Fig. 3). It is medial to the adductor mandibulae and dorsolateral to the dorsal elements of the gill arches. Its origin includes the lateral edge of the parasphenoid and lateral ethmoid; its insertion is the posterior face of the mesopterygoid, the dorsal face of the metapterygoid, and the medial face of the hyomandibular at the base of the ...
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... the gill arches. Its origin includes the lateral edge of the parasphenoid and lateral ethmoid; its insertion is the posterior face of the mesopterygoid, the dorsal face of the metapterygoid, and the medial face of the hyomandibular at the base of the orbit (Fig. 7). Anteriorly, the adductor arcus palatini and retractor arcus palatini intergrade (Fig. 3); however, fibers of the adductor arcus palatini are oblique, whereas fibers of the retractor arcus palatini are horizontal (Figs. 1, ...
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... origin includes the lateral edge of the parasphenoid and lateral ethmoid; its insertion is the posterior face of the mesopterygoid, the dorsal face of the metapterygoid, and the medial face of the hyomandibular at the base of the orbit (Fig. 7). Anteriorly, the adductor arcus palatini and retractor arcus palatini intergrade (Fig. 3); however, fibers of the adductor arcus palatini are oblique, whereas fibers of the retractor arcus palatini are horizontal (Figs. 1, 3). ...
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... retractor arcus palatini connects the neurocranium and suspensorium. It is a long, laterally compressed muscle with near horizontal fibers (Figs. 1, 3). It intergrades with the adductor arcus palatini along their common border. ...
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... protractor hyoidei has three sections (Figs. 3, 5, 8). The largest section, section one, is parallel to the ventral midline. It originates on the underside of the skin and overlying fascia of the sternohyoideus adjacent to the cleithra. Tendons extend posteriorly from each antimere at the cleithra to the ventral surface of the pelvic girdle (Fig. 8). Anteriorly, antimeres intergrade and ...
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... on the medial surface of the dentary on either side of the symphysis, ventral to the intermandibularis (Fig. 5). Section two is dorsal and lateral to section one but is shorter and less massive than section one (Figs. 3, 8). It originates on the anteroventral surface of branchiostegal ray one and anterohyal (Fig. 8). As antimeres converge anteriorly toward the ventral midline, they intergrade with section one. Section two inserts on the medial side of the dentary dorsal to the intermandibularis (Fig. 5). Section three is a single, median sheet of muscle ...
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... hyohyoides inferioris connects the branchiostegal rays and urohyal (Fig. 3). Fibers attach to the medial surface of ray one and converge toward the ventral midline anteriorly, where antimeres fuse by means of a raphé on the ventral side of the urohyal. From the urohyal, tendons connect the hyohyoides inferioris to the lateral sides of the ventrohyals. The muscle and tendons form an X in ventral view, with the ...
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... Only the dorsalmost fibers of the obiquus dorsalis II-transversus dorsalis II mass are continuous across the dorsal midline in the absence of a raphé and thus represent transversus dorsalis II. Transversus dorsalis III is present only in Naso lituratus. Transverus dorsalis IV is easily recognizable, largely because obliquus dorsalis IV is absent (Fig. 13). As a cautionary note, sphincter oesophagi fibers from the esophagus extend anterior of the retractor dorsalis, thus spatially resembling transversus dorsalis ...
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... is a single, well-developed muscle connecting the dorsal, posteromedial surface of ceratobranchial five and the posteromedial surface of epibranchial four. It is posterior to adductor IV and medial to adductor V (Fig. ...
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... vertebrae to the pharyngobranchials (Fig. 10). The origin includes at least the first three vertebral centra and the posteroventral surface of the basioccipital, posterior and dorsal to the attachment of Baudelot's ligament. Fibers pass anteroventrally from the origin to insert on the posterodorsal surface of pharyngobranchials three and four (Fig. 13). ...
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... I, II, and III are reduced to nonmuscular attachments between ceratobranchials and epibranchials of the same gill arches. Adductor IV connects the dorsomedial surface of ceratobranchial four and the posterolateral surface of epibranchial four lateral to the obliquus posterior (Fig. 13). Adductor V connects the dorsal, anteromedial surface of ceratobranchial five and the posterior surface of epibranchial four (Fig. ...
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... and epibranchials of the same gill arches. Adductor IV connects the dorsomedial surface of ceratobranchial four and the posterolateral surface of epibranchial four lateral to the obliquus posterior (Fig. 13). Adductor V connects the dorsal, anteromedial surface of ceratobranchial five and the posterior surface of epibranchial four (Fig. ...
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... oesophagi (SO) Fibers of the sphinctor oesophagi do not form a continuous and compact muscle around the esophagus. Attachment sites include the ventral side of the esophagus, between the medial surface of the fifth ceratobranchials posterior to transversus ventralis V, and the dorsal surface of the esophagus anterior of the retractor dorsalis (Fig. 13). Transversi ventrales (TV IV-V) Both muscles are dorsoventrally flattened sheets connecting the medial surfaces of ceratobranchials four and five, respectively, across the ventral midline. Transversus ventralis IV is trapezoidal and extends between the medial sides of the fourth ceratobranchials covering the cartilaginous tips of the ...
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... sternohyoideus connects the pectoral girdle and hyoid arch. It is a large, bulky muscle extending from the anterior surfaces of the cleithra (Figs. 3, 8) to the lateral sides of the urohyal (Fig. 9) ventral to the origin of the rectus communis. Both origin and insertion are muscular. Antimeres lie on either side of ventral midline and intergrade anteriorly (Fig. 9). Dorsally, the muscle gives rise to a tendinous sheet in the midsagittal plane dividing the ventral surface of the gill ...
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... abductor superficialis originates from the anterior, lateral surface of the cleithrum, the posterior side of the lateral flange of the cleithrum, and the tip of the anteriorly projecting coracoid spine lying on the ventrolateral edge of the cleithrum (Figs. 3, 15). Separate tendons insert on the anterior half of the lateral side of each ray's basal flange, excluding the marginal ray. Tendons are laterally compressed and overlapping, functionally forming an aponeurotic sheet (Fig. ...
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... muscle is the larger of the two abductor muscles and divisible into two subequal sections (Fig. 3). Section one is the larger and more lateral of the two sections. The origin is the lateral sides of the coracoid and coracoid spine (Fig. 15), excluding the posterodorsal surface of the coracoid. Separate, ribbon-like tendons insert on the ventral side of the distal end of each ray's basal flange, excluding the marginal ray. Tendons ...
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... on the medial surface of the dentary on either side of the symphysis, ventral to the intermandibularis ( Fig. 5). Section two is dorsal and lateral to section one but is shorter and less massive than section one (Figs. 3, 8). It originates on the anteroventral surface of branchiostegal ray one and anterohyal (Fig. 8). As antimeres converge anteriorly toward the ventral midline, they intergrade with section one. Section two inserts on the medial side of the dentary dorsal to the intermandibularis (Fig. 5). Section three is a single, median sheet of muscle on the ventral surface of section one (Fig. 8) and intergrades with it. A myocommatum is present at the posterior border of section three. Hyohyoidei abductores (HYAB) Abductors connect branchiostegal rays to the hyoid arch. They originate on the posteroventral corner of the ventrohyal (Fig. 9) and pass ventral to the anterohyal, to which they intermittently attach, and insert on the medial bases of all four branchiostegal rays. Hyohyoidei adductores (HYAD) Adductors lie between and across the proximal ends of the branchiostegal rays. They connect successive branchiostegal rays (Figs. 8, 9) and branchiostegal ray four to the posteromedial surface of the opercular plate. The muscular fibers are greatly reduced in mass and do not form a continuous bundle. Hyohyoides inferioris (HYIN) The hyohyoides inferioris connects the branchiostegal rays and urohyal (Fig. 3). Fibers attach to the medial surface of ray one and converge toward the ventral midline anteriorly, where antimeres fuse by means of a raph ́ on the ventral side of the urohyal. From the urohyal, tendons connect the hyohyoides inferioris to the lateral sides of the ventrohyals. The muscle and tendons form an X in ventral view, with the urohyal at the intersection (Fig. 9). Levatores externi (LE I–IV) Four distinct muscles connect the neurocranium and epibranchials. They originate from the ventral surface of the prootic medial to the origin of the adductor ...
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... ventral to the sphenotic process. Posteriorly, the levator arcus palatini is medial to the dilatator operculi. Dilatator operculi (DO) The dilatator operculi is also conical, but its apex is ventrally directed and connects the neurocranium and opercle (Figs. 1, 3). It is bordered anteriorly by the levator arcus palatini and posteriorly by the levator operculi. No intergradation of these three muscles occurs. The origin includes the posterior sur- face of the sphenotic, lateral surfaces of the hyomandibular heads and the anterior surface of the pterotic. The insertion is the dilatator process of the opercle. Levator operculi (LO) The levator operculi connects the neurocranium and suspensorium. It originates from the pterotic (Figs. 1, 3) and inserts on the medial side of the posterodorsal surface of the opercle (Fig. 7). It is composed of two bundles, near equal in size, that intergrade and are only weakly separable (Winterbottom, ’93). Bundles differ in fiber direction (Fig. 6), and fat deposits lie lateral of the levator operculi. Adductor arcus palatini (AAP) The adductor arcus palatini is a thick muscle connecting the neurocranium and suspensorium. It extends anteriorly from the level of the nasal rosette posteriorly to the prootic but not attaching to it (Fig. 3). It is medial to the adductor mandibulae and dorsolateral to the dorsal elements of the gill arches. Its origin includes the lateral edge of the parasphenoid and lateral ethmoid; its insertion is the posterior face of the mesop- terygoid, the dorsal face of the metapterygoid, and the medial face of the hyomandibular at the base of the orbit (Fig. 7). Anteriorly, the adductor arcus palatini and retractor arcus palatini intergrade (Fig. 3); however, fibers of the adductor arcus palatini are ob- lique, whereas fibers of the retractor arcus palatini are horizontal (Figs. 1, 3). Retractor arcus palatini (RAP) The retractor arcus palatini connects the neurocranium and suspensorium. It is a long, laterally compressed muscle with near horizontal fibers (Figs. 1, 3). It intergrades with the adductor arcus palatini along their common border. The origin is the parasphenoid ventral to the cartilaginous median ethmoid. Anteriorly, the muscle tapers and quickly becomes tendinous, losing its bulk, and inserts on the lateral, posterodorsal surface of the palatine. Adductor operculi (AO) The adductor operculi connects the neurocranium and suspensorium. This cylindrical muscle originates from the ventrolateral surface of the parasphenoid, anterior to the attachment site of Baudelot’s ligament, and extends laterally to insert on a short, dorsally directed process on the dorsomedial surface of the opercle (Fig. 7). Adductor hyomandibulae (ADHY) The adductor hyomandibulare is a sheet of muscle lying in a frontal plane originating from the prootic and inserting linearly on the medial face of the anterior hyomandibular head (Fig. 7). The adductor hyomandibulae and adductor operculi are adjacent but do not intergrade (Fig. 7). Intermandibularis (INTM) The intermandibularis is a horizontal sheet of muscle connecting the medial halves of the dentary across the symphysis. Antimeres insert with each other at the ventral midline. The muscle separates the insertion of the protractor hyoidei into dorsal and ventral sites (Fig. 5). Protractor hyoidei (PRHY) The protractor hyoidei has three sections (Figs. 3, 5, 8). The largest section, section one, is parallel to the ventral midline. It originates on the underside of the skin and overlying fascia of the sternohyoideus adjacent to the cleithra. Tendons extend posteriorly from each antimere at the cleithra to the ventral surface of the pelvic girdle (Fig. 8). Anteriorly, antimeres intergrade and ...
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... ventral to the sphenotic process. Posteriorly, the levator arcus palatini is medial to the dilatator operculi. Dilatator operculi (DO) The dilatator operculi is also conical, but its apex is ventrally directed and connects the neurocranium and opercle (Figs. 1, 3). It is bordered anteriorly by the levator arcus palatini and posteriorly by the levator operculi. No intergradation of these three muscles occurs. The origin includes the posterior sur- face of the sphenotic, lateral surfaces of the hyomandibular heads and the anterior surface of the pterotic. The insertion is the dilatator process of the opercle. Levator operculi (LO) The levator operculi connects the neurocranium and suspensorium. It originates from the pterotic (Figs. 1, 3) and inserts on the medial side of the posterodorsal surface of the opercle (Fig. 7). It is composed of two bundles, near equal in size, that intergrade and are only weakly separable (Winterbottom, ’93). Bundles differ in fiber direction (Fig. 6), and fat deposits lie lateral of the levator operculi. Adductor arcus palatini (AAP) The adductor arcus palatini is a thick muscle connecting the neurocranium and suspensorium. It extends anteriorly from the level of the nasal rosette posteriorly to the prootic but not attaching to it (Fig. 3). It is medial to the adductor mandibulae and dorsolateral to the dorsal elements of the gill arches. Its origin includes the lateral edge of the parasphenoid and lateral ethmoid; its insertion is the posterior face of the mesop- terygoid, the dorsal face of the metapterygoid, and the medial face of the hyomandibular at the base of the orbit (Fig. 7). Anteriorly, the adductor arcus palatini and retractor arcus palatini intergrade (Fig. 3); however, fibers of the adductor arcus palatini are ob- lique, whereas fibers of the retractor arcus palatini are horizontal (Figs. 1, 3). Retractor arcus palatini (RAP) The retractor arcus palatini connects the neurocranium and suspensorium. It is a long, laterally compressed muscle with near horizontal fibers (Figs. 1, 3). It intergrades with the adductor arcus palatini along their common border. The origin is the parasphenoid ventral to the cartilaginous median ethmoid. Anteriorly, the muscle tapers and quickly becomes tendinous, losing its bulk, and inserts on the lateral, posterodorsal surface of the palatine. Adductor operculi (AO) The adductor operculi connects the neurocranium and suspensorium. This cylindrical muscle originates from the ventrolateral surface of the parasphenoid, anterior to the attachment site of Baudelot’s ligament, and extends laterally to insert on a short, dorsally directed process on the dorsomedial surface of the opercle (Fig. 7). Adductor hyomandibulae (ADHY) The adductor hyomandibulare is a sheet of muscle lying in a frontal plane originating from the prootic and inserting linearly on the medial face of the anterior hyomandibular head (Fig. 7). The adductor hyomandibulae and adductor operculi are adjacent but do not intergrade (Fig. 7). Intermandibularis (INTM) The intermandibularis is a horizontal sheet of muscle connecting the medial halves of the dentary across the symphysis. Antimeres insert with each other at the ventral midline. The muscle separates the insertion of the protractor hyoidei into dorsal and ventral sites (Fig. 5). Protractor hyoidei (PRHY) The protractor hyoidei has three sections (Figs. 3, 5, 8). The largest section, section one, is parallel to the ventral midline. It originates on the underside of the skin and overlying fascia of the sternohyoideus adjacent to the cleithra. Tendons extend posteriorly from each antimere at the cleithra to the ventral surface of the pelvic girdle (Fig. 8). Anteriorly, antimeres intergrade and ...
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... 8. Left, ventrolateral view of the muscles of the ventral side of the head of Naso minor , 176 mm SL, ROM 67183. HYAD, hyohyoidei adductores. Other abbreviations as in Fig. 3. Scale ϭ 0.5 cm.
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... 15. Lateral view of the superficial musculature of the left pectoral fin, 17 rays, of Naso caeruleacauda , 245 mm SL, ROM 66949. ARV, arrector ventralis; CLTH, cleithrum; CORA, coracoid. Other abbreviations as in Fig. 3. Scale ϭ 1 cm.
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... dorsally, attaching to a ventrally directed process of hypobranchial two ( Fig. 14). A smaller tendon arises from the sternohyoideus immediately posterior of this tendon. Antimeres converge medially and fuse dorsal to the rectus communis. Antimeres then diverge before attaching to the anterior sides of the ventrally directed processes of the third hypobranchial (Fig. 14). This latter tendon is the sternobranchialis (STB) and in all unicornfishes is tendinous only. Pharyngoclavicularis externus (PCE) The pharyngoclavicularis externus connects the pectoral girdle to the fifth gill arch. It is well developed, laterally compressed, and nearly vertical, passing posterodorsally from origin to insertion (Fig. 10). It originates from the dorsal side of the cleithrum posterior to the origin of the sternohyoideus and inserts tendinously on the ventral side of ceratobranchial five immediately anterior to transversus ventralis V (Fig. 14). Pharyngoclavicularis internus (PCI) The pharyngoclavicularis internus connects the pectoral girdle to the fifth gill arch. It is well developed, laterally compressed, and nearly horizontal, passing anterodorsally from origin to insertion (Fig. 10). It originates from the medial side of the cleithrum at the junction of its vertical and horizontal arms and inserts on the ventral side of ceratobranchial five, including both bone and cartilaginous tip. The insertion is covered ventrally by the transversus ventralis IV except in Naso maculatus, in which transversus ventralis IV is anterior to ceratobranchial five, thus exposing the insertion of pharyngoclavicularis internus in ventral view. Protractor pectoralis (PP) The protractor pectoralis connects the neurocranium to the dorsal elements of the pectoral girdle. It is a thin sheet of muscle originating from the pterotic (Fig. 10) and grading quickly into an aponeurotic sheet connecting the pectoral girdle and ceratobranchial five. The muscle lies in a trans- verse plane posterior to the gill arches at the level of the anterior border of the supracleithrum. Levator pectoralis (LP) The levator pectoralis connects the neurocranium to the dorsal elements of the pectoral girdle. It is a small slip of muscle between the anterior surface of the supracleithrum and posterolateral surface of the pterotic dorsal to the levator operculi (Fig. 6). The fibers are nearly horizontal, passing anterodorsally from supracleithrum to pterotic. Abductor superficialis (ABS) The abductor superficialis originates from the anterior, lateral surface of the cleithrum, the posterior side of the lateral flange of the cleithrum, and the tip of the anteriorly pro- jecting coracoid spine lying on the ventrolateral edge of the cleithrum (Figs. 3, 15). Separate tendons insert on the anterior half of the lateral side of each ray’s basal flange, excluding the marginal ray. Tendons are laterally compressed and overlapping, functionally forming an aponeurotic sheet (Fig. 15). Abductor profundus (ABP) This muscle is the larger of the two abductor muscles and divisible into two subequal sections (Fig. 3). Section one is the larger and more lateral of the two sections. The origin is the lateral sides of the coracoid and coracoid spine (Fig. 15), excluding the posterodorsal surface of the coracoid. Separate, ribbon-like tendons insert on the ventral side of the distal end of each ray’s basal flange, excluding the marginal ray. Tendons are laterally compressed and functionally form an aponeurotic sheet due to their overlapping orientation. The second and smaller section serves only the marginal ray. This vertical bundle is medial to the anterior edge of the main mass of the abductor profundus. The origin is from the coracoid and extends dorsally to the coracoid-scapula suture but does not include the scapula. A large, thick tendon inserts on the ventral side of the base of the marginal ray. Arrector ventralis (ARV) The arrector ventralis is well developed, nearly vertical, and medial to the abductor superficialis. Its origin includes the coracoid spine and the lateral side of the cleithrum posterior to the cleithrum-coracoid suture. A large tendon inserts on the medial side of the base of the marginal ray (Fig. ...
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... edge of A2  . It extends anterodorsally and inserts on the dorsomedial surface of the maxilla (Figs. 1, 2). Adductor mandibulae, section A2 ␣ (A2 ␣ ) Adductor mandibulae A2 is divisible into ␣ and  sections that are differentiable by their sites of insertion. Section A2 ␣ is dorsal to A2  ; both sections are ventral to A1 ␣ . The origin of section A2 ␣ is the anterodorsal surface of the hyomandibular at the anteroventral corner of the orbit (Figs. 1, 3). The insertion is tendinous on the medial side of the dentary and may include the ligamentum primordium ( Fig. 1). In Naso lituratus and N . unicornis , fibers of A1 ␣ and A2 ␣ do not intergrade, and no identifiable part of the ligamentum primordium is visible in lateral view (Fig. 3). The ligamentum primordium is either reduced or is so closely associated with the insertional tendon of A2 ␣ that it is not discern- ible. The only identifiable part of the ligament may be the posteriormost end that is tentatively identified as a nonmuscular con- nection between A1 ␣ and A2 ␣ posterior to the origin of A1  . Unique to these two unicornfishes is a slimmer A2 ␣ relative to other unicornfishes. In the remaining 13 species of unicornfishes, A1 ␣ and A2 ␣ intergrade considerably, and a horizontal crease in the A1 ␣ –A2 ␣ mass may be the boundary between the two muscles. Of these 13 species, only the ventral portion of the ligamentum primordium is visible in lateral view in Naso brachycentron and N . tuberosus (Fig. 2). The dorsal half of the ligamentum primordium passes medially to A1 ␣ and A2 ␣ , but the ventral half is confluent with the insertional tendon of A2 ␣ and is visible in lateral view. As is the case in Naso lituratus and N . unicornis , A1 ␣ , A2 ␣ , and ligamentum primordium are not coplanar (Figs. 2, ...
Citations
... g., African spadefish Tripterodon orbis Playfair 1867) contain red muscle in a subcutaneous position consistent with other ectothermic fishes (Borden, 1999;Winterbottom, 1993), indicating that internalized red muscle is a derived character of L. imperialis unique among extant acanthuriforms. However, this medial shift in red muscle distribution not only aids in its insulation but also inherently alters the mechanics of swimming (Syme & Shadwick, 2011). ...
Ectothermy and endothermy in extant fishes are defined by distinct integrated suites of characters. Although only ⁓0.1% of fishes are known to have endothermic capacity, recent discoveries suggest that there may still be uncommon pelagic fish species with yet to be discovered endothermic traits. Among the most rarely encountered marine fishes, the louvar Luvarus imperialis is a remarkable example of adaptive evolution as the only extant pelagic species in the order Acanthuriformes (including surgeonfishes, tangs, unicornfishes and Moorish idol). Magnetic resonance imaging and gross necropsy did not yield evidence of cranial or visceral endothermy but revealed a central‐posterior distribution of myotomal red muscle that is a mixture of the character states typifying ectotherms (lateral‐posterior) and red muscle endotherms (central‐anterior). Dissection of a specimen confirmed, and an osteological proxy supported, that L. imperialis has not evolved the vascular rete that is vital to retaining heat in the red muscle. The combination of presumably relying on caudal propulsion while exhibiting internal red muscle without associated retia is unique to L. imperialis among all extant fishes, raising the macroevolutionary question of whether this species – in geologic timescales – will remain an ectotherm or evolve red muscle endothermy.
... Evidence presented here suggests the relevance of musculature as a source of reliable phylogenetic signal, a view foreshadowed by Borden (1999). That author found little intraspecific variability in the muscles of Naso species (Acanthuridae; Perciformes) when compared to other anatomical complexes (e.g., osteology) and, in combination with data from other studies, concluded that myological characters are reliable indicators of relationships at deep levels of phylogeny. ...
The present study offers a broad comparative analysis of the dorsolateral head musculature in the Gymnotiformes, with detailed descriptions and illustrations of the dorsolateral head muscles of 83 species representing combined all valid genera. Results permit a detailed assessment of primary homologies and taxonomically-relevant variation across the order. This provides the basis for a myological synonymy, which organizes 33 previously proposed names for 15 recognized muscles. Morphological variation derived from dorsolateral head musculature was coded into 56 characters. When analyzed in isolation, that set of characters results in Gymnotidae as the sister group of remaining gymnotiforms, and all other currently recognized families as monophyletic groups. In a second analysis, myological characters were concatenated with other previously proposed characters into a phenotypic matrix. Results of that analysis reveal new myological synapomorphies for nearly all taxonomic categories within Gymnotiformes. A Partitioned Bremer Support (PBS) was used to asses the significance of comparative myology in elucidating phylogenetic relationships. PBS values show strongly non-uniform distributions on the tree, with positive scores skewed towards more inclusive taxa, and negative PBS values concentrated on less inclusive clades. Our results provide background for future studies on biomechanical constraints evolved in the early stages of gymnotiform evolution.
... The resulting nomenclatural confusion is obvious, with the name adductor arcus palatini having been ambiguously applied to: (1) the short, plesiomorphic muscle attached solely to the hyomandibula and corresponding to the adductor hyomandibulae of basal actinopterygians (e.g., Elopiformes [1]); (2) the whole expanded muscle attached to both hyomandibula and palatoquadrate and thus encompassing the primitive adductor hyomandibulae (most teleosts [1,47]); (3) the anteriormost portion of the muscle attached solely to the palatoquadrate and separated from the posterior adductor hyomandibulae (e.g. some Clupeiformes, Cypriniformes, Osteoglossiformes, Perciformes, Siluriformes, and Tetraodontiformes [1,2,4,48,49]); or (4) an intermediate portion of the muscle located between the anteriormost retractor arcus palatini or extensor tentaculi and the posteriormost adductor hyomandibulae (e.g., some Acanthuriformes, Siluriformes, and Tetraodontiformes [1,2,4,49,50]). ...
Background
The facial musculature is a remarkable anatomical complex involved in vital activities of fishes, such as food capture and gill ventilation. The evolution of the facial muscles is largely unknown in most major fish lineages, such as the Actinopterygii. This megadiverse group includes all ray-finned fishes and comprises approximately half of the living vertebrate species. The Polypteriformes, Acipenseriformes, Lepisosteiformes, Amiiformes, Elopiformes, and Hiodontiformes occupy basal positions in the actinopterygian phylogeny and a comparative study of their facial musculature is crucial for understanding the cranial evolution of bony fishes (Osteichthyes) as a whole.
Results
The facial musculature of basal actinopterygians is revised, redescribed, and analyzed under an evolutionary perspective. We identified twenty main muscle components ontogenetically and evolutionarily derived from three primordial muscles. Homologies of these components are clarified and serve as basis for the proposition of a standardized and unifying myological terminology for all ray-finned fishes. The evolutionary changes in the facial musculature are optimized on the osteichthyan tree and several new synapomorphies are identified for its largest clades, including the Actinopterygii, Neopterygii, and Teleostei. Myological data alone ambiguously support the monophyly of the Holostei. A newly identified specialization constitutes the first unequivocal morphological synapomorphy for the Elopiformes. The myological survey additionally allowed a reinterpretation of the homologies of ossifications in the upper jaw of acipenseriforms.
Conclusions
The facial musculature proved to be extremely informative for the higher-level phylogeny of bony fishes. These muscles have undergone remarkable changes during the early radiation of ray-finned fishes, with significant implications for the knowledge of the musculoskeletal evolution of both derived actinopterygians and lobe-finned fishes (Sarcopterygii).
... The taxon selected for this study is a genus of acanthurid fishes, Naso, a strongly reefassociated group of perciform fishes with 19 extant species (Randall 2002). There is a substantial literature on the taxonomy (Smith 1966;Tyler et al. 1989;Randall 1994;Randall 2001;Johnson 2002;Randall 2002) and ecology (Jones 1968;Clements and Choat 1995;Choat and Clements 1998;Wilson and McCormick 1999;Leis and Carson-Ewart 2000;Choat and Robertson 2002;Leis and McCormick 2002) of acanthurid fishes and their evolutionary relationships in terms of fossil records (Tyler 2000) and morphology-based phylogenetic analyses (Winterbottom and McLennan 1993;Borden 1998;Borden 1999). ...
... Because several independent studies proposed that blenniiforms and gobiesociforms form a monophyletic group [4,7,55,64], the precise optimization of the presence of recti ventrales II and III in these taxa is ambiguous. To further complicate the issue, other apparently non-closely related percomorphs also have recti ventrales II and/or III: some acanthuriforms [71,72], tetraodontiforms [73], cottoids [74,75], and gasterosteiforms [25]. ...
... In Antigonia, one of the two examined specimens of Capros, triacanthids, balistoids, drepaneids, ephippidids, scatophagids, most acanthuriforms (except Luvarus and Siganus), chaetodontids, pomacentrids, and pristolepidids, obliquus ventralis II has an anterior projection that attaches to the sagittal elements of the anteriormost pharyngeal arches (urohyal, basihyal, or basibranchial 1) (Fig. 13). Some authors designate this anterior projection as rectus ventralis II [71][72][73], but in our opinion such a designation might be confusing in taxa having this muscle projection completely continuous with the remainder of obliquus ventralis II. A so-called rectus ventralis II is also present in a few internested subgroups within the Blenniiformes (Fig. 8), Gasterosteiformes [25], and Gobiesociformes. ...
... In the primitive percomorph condition, the pharyngoclavicularis externus inserts musculously on ceratobranchial 5 (Figs. 3,6,7,8,9,10,11,12,14,15). In Antigonia, acanthurids, and most tetraodontiforms, the insertion of this muscle is entirely mediated by tendon (Fig. 13) [71][72][73]. 29. The caproiform Antigonia and non-tetraodontoid tetraodontiforms have a fully differentiated sternobranchialis, a muscle derived from the separation of the dorsomedial portion of the sternohyoideus (Fig. 13) [33]. ...
The muscles serving the ventral portion of the gill arches ( = infrabranchial musculature) are poorly known in bony fishes. A comparative analysis of the infrabranchial muscles in the major percomorph lineages reveals a large amount of phylogenetically-relevant information. Characters derived from this anatomical system are identified and discussed in light of current hypotheses of phylogenetic relationships among percomorphs. New evidence supports a sister-group relationship between the Batrachoidiformes and Lophiiformes and between the Callionymoidei and Gobiesocoidei. Investigated data also corroborate the existence of two monophyletic groups, one including the Pristolepididae, Badidae, and Nandidae, and a second clade consisting of all non-amarsipid stromateiforms. New synapomorphies are proposed for the Atherinomorphae, Blenniiformes, Lophiiformes, Scombroidei (including Sphyraenidae), and Gobiiformes. Within the latter order, the Rhyacichthyidae and Odontobutidae are supported as the successive sister families of all remaining gobiiforms. The present analysis further confirms the validity of infrabranchial musculature characters previously proposed to support the grouping of the Mugiliformes with the Atherinomorphae and the monophyly of the Labriformes with the possible inclusion of the Pholidichthyiformes. Interestingly, most hypotheses of relationships supported by the infrabranchial musculature have been advanced by preceding anatomists on the basis of distinct data sources, but were never recovered in recent molecular phylogenies. These conflicts clearly indicate the current unsatisfactory resolution of the higher-level phylogeny of percomorphs.
... In general, myological patterns of origin and insertion do not echo the patterns of bony fusions, losses, and complexity. In the most general of terms, muscles appear to be more evolutionarily conservative than bones (BORDEN 1999, DIOGO 2004) even within diverse lineages and at various taxonomic ranks. Consequently, the number of osteological characters usually outnumbers myological characters, but a tradeoff has been suggested whereby myology might contain less homoplasy. ...
There are no fewer than twenty phylogenetic hypotheses of basal acanthomorph relationships. Among basal acanthomorphs, the Paracanthopterygii have historically been one of the more difficult groups to characterize, leaving many systematists to question their composition and monophyly. Here we investigate the osteology and myology of the caudal fin of paracanthopterygians. We describe 26 characters (14 osteological, 12 myological) from Recent and fossil material and evaluated their congruence with a phylogenetic hypothesis [Polymixiiformes (Percopsiformes (Zeiformes (Gadiformes Stylephoriformes)))] derived from the analysis of DNA sequence data. Osteological characters support more basal nodes and nodes within zeiforms and percopsiforms. In contrast, myological characters reflected the unique caudal fin of gadiforms and stylephoriforms. Both types of characters revealed significant homoplasies when mapped onto the existing molecular hypothesis. Nonetheless, osteologi-cal homoplasy reflected the recurring trend among teleosts of simplification of the caudal skeleton. Myological homoplasy reflected in part the inclusion of fossil taxa and the unusual, but varied, states within gadiforms. Despite these issues and a general need for increased resolution of relationships within paracanthopterygian lineages, morphology of the caudal fin reasonably supported the revised relationships. Perhaps more importantly , it highlighted the significant work needed to place many fossil lineages accurately and to test hypotheses of homology.
... In one of the first studies that considered the utility of myological data for phylogenetic reconstruction, Borden [31] described the configuration and variation of 93 muscles in 15 species of the genus Naso or Unicornfishes (Teleostei: Percomorpha) and discussed the phylogenetic implications of the results. Borden suggests [31] that phylogenetic studies have neglected evidence from myology because "investigators may be reluctant to use myology due, for example, to the plethora of names that have been used to describe the same muscles, to the realization that osteological proficiency is mandatory in order to identify muscles, leading them to concentrate only on osteology, or to the requirement of potentially finer dissection to preserve muscle bundles and nerves". ...
... In one of the first studies that considered the utility of myological data for phylogenetic reconstruction, Borden [31] described the configuration and variation of 93 muscles in 15 species of the genus Naso or Unicornfishes (Teleostei: Percomorpha) and discussed the phylogenetic implications of the results. Borden suggests [31] that phylogenetic studies have neglected evidence from myology because "investigators may be reluctant to use myology due, for example, to the plethora of names that have been used to describe the same muscles, to the realization that osteological proficiency is mandatory in order to identify muscles, leading them to concentrate only on osteology, or to the requirement of potentially finer dissection to preserve muscle bundles and nerves". In consequence "of those studies using myology as a basis of information, most are functional works often analyzing the role of various muscles in feeding or locomotion or comparing a muscle or specific group across a number of taxa systematically and/ or ecologically related" [31]. ...
... Borden suggests [31] that phylogenetic studies have neglected evidence from myology because "investigators may be reluctant to use myology due, for example, to the plethora of names that have been used to describe the same muscles, to the realization that osteological proficiency is mandatory in order to identify muscles, leading them to concentrate only on osteology, or to the requirement of potentially finer dissection to preserve muscle bundles and nerves". In consequence "of those studies using myology as a basis of information, most are functional works often analyzing the role of various muscles in feeding or locomotion or comparing a muscle or specific group across a number of taxa systematically and/ or ecologically related" [31]. Diogo [32,33] compared the incidence of homoplasy and the utility of 91 myological and 303 osteological characters used in the reconstruction of the higher-level phylogeny of a diverse group of teleosts, the Siluriformes (or catfish). ...
Molecules are rapidly replacing morphology as the preferred source of evidence for generating phylogenetic hypotheses. Critics of morphology claim that most morphology-based characters are ambiguous, subjective and prone to homoplasy. In this paper we summarize the results of recent Bayesian and parsimony-based cladistic analyses of the gross muscle morphology of primates and of other animals that show that morphological evidence such as muscle-based data is as capable of recovering phylogenies as are molecular data. We also suggest that recent investigations of neural crest cells and muscle connectivity might help to explain why muscles provide particularly useful characters for inferring phylogenies. Lastly, we show how the inclusion of soft tissue-based information in phylogenetic investigations allows researchers to address evolutionary questions that are not tractable using molecular evidence alone, including questions about the evolution of our closest living relatives and of our own clade.
... In one of the first studies that considered the utility of myological data for phylogenetic reconstruction, Borden [31] described the configuration and variation of 93 muscles in 15 species of the genus Naso or Unicornfishes (Teleostei: Percomorpha) and discussed the phylogenetic implications of the results. Borden suggests [31] that phylogenetic studies have neglected evidence from myology because "investigators may be reluctant to use myology due, for example, to the plethora of names that have been used to describe the same muscles, to the realization that osteological proficiency is mandatory in order to identify muscles, leading them to concentrate only on osteology, or to the requirement of potentially finer dissection to preserve muscle bundles and nerves". ...
... In one of the first studies that considered the utility of myological data for phylogenetic reconstruction, Borden [31] described the configuration and variation of 93 muscles in 15 species of the genus Naso or Unicornfishes (Teleostei: Percomorpha) and discussed the phylogenetic implications of the results. Borden suggests [31] that phylogenetic studies have neglected evidence from myology because "investigators may be reluctant to use myology due, for example, to the plethora of names that have been used to describe the same muscles, to the realization that osteological proficiency is mandatory in order to identify muscles, leading them to concentrate only on osteology, or to the requirement of potentially finer dissection to preserve muscle bundles and nerves". In consequence "of those studies using myology as a basis of information, most are functional works often analyzing the role of various muscles in feeding or locomotion or comparing a muscle or specific group across a number of taxa systematically and/ or ecologically related" [31]. ...
... Borden suggests [31] that phylogenetic studies have neglected evidence from myology because "investigators may be reluctant to use myology due, for example, to the plethora of names that have been used to describe the same muscles, to the realization that osteological proficiency is mandatory in order to identify muscles, leading them to concentrate only on osteology, or to the requirement of potentially finer dissection to preserve muscle bundles and nerves". In consequence "of those studies using myology as a basis of information, most are functional works often analyzing the role of various muscles in feeding or locomotion or comparing a muscle or specific group across a number of taxa systematically and/ or ecologically related" [31]. Diogo [32,33] compared the incidence of homoplasy and the utility of 91 myological and 303 osteological characters used in the reconstruction of the higher-level phylogeny of a diverse group of teleosts, the Siluriformes (or catfish). ...
... The high frequency of mimicking variants in the caudal and pectoral fins necessitates the use of alternative coding methods to incorporate intraspecifically polymorphic characters into phylogenetic analyses (e.g., Wiens & Servedio 1997;Wiens 1999Wiens , 2001. Overall, the paucity of myological characters suitable for phylogenetic analysis at low taxonomic levels, including Micropterus, and their relative rarity compared to osteological characters at these same taxonomic levels is a generally supported tenet (Kesner 1994 and references therein;Borden 1998;Diogo 2004). ...
Diverse freshwater lacustrine fishes enter tributaries to spawn, but resident riverine members may also occupy these same tributaries. While mark-recapture and biotelemetry studies suggest reproductive isolation between such populations, the assertion has rarely been tested genetically. To address this question, Micropterus dolomieu (Smallmouth Bass) from the southern shoreline of Lake Erie were compared genetically to bass in adjacent tributaries. Results from mitochondrial DNA sequences support the hypothesis that lacustrine and riverine populations segregate. Furthermore, divergences among tributary populations were often as large as those divergences between lacustrine and riverine bass, suggesting that each river population may become genetically distinct.
... The high frequency of mimicking variants in the caudal and pectoral fins necessitates the use of alternative coding methods to incorporate intraspecifically polymorphic characters into phylogenetic analyses (e.g., Wiens & Servedio 1997;Wiens 1999Wiens , 2001. Overall, the paucity of myological characters suitable for phylogenetic analysis at low taxonomic levels, including Micropterus, and their relative rarity compared to osteological characters at these same taxonomic levels is a generally supported tenet (Kesner 1994 and references therein;Borden 1998;Diogo 2004). However, across higher taxonomic levels, these five muscle systems (cheek, branchial gill arches, paired fins, caudal fin) are evolutionarily stable complexes that provide numerous myological characters suitable for comparative and systematic analyses of teleosts and perciforms. ...
Striated muscles of a generalized genus of percomorph fishes (Micropterus, Centrarchidae, Percomorpha) were described. Overall, myological variation was sparse among species of black bass. Variation took the form of minor variants in the size or shape of a muscle or of singular or incongruous variants characterized by abnormalities in a single specimen. The remaining myological variation occurred as mimicking variants and was shared irregularly among taxa. The lack of myological variation among black bass may well be correlated with the low degree of diversity exhibited in their ecology, life history, and external anatomy. However, the value of Micropterus in systematic and evolutionary studies is not compromised by morphological stasis. Instead, because Micropterus and other conserved lineages have been minimally responsive to ecological factors, they are valuable as outgroups to polarize character states, as identifiers of vicariant events leading to allopatric speciation, and as exemplars for studying the evolutionary mechanism of stabilizing selection. In addition, the description and assessment of myological variation in this generalized percomorph will be useful in future studies of comparative anatomy, functional morphology, and higher level systematics.
