CRANIUM ASSOCIATED MUSCULATURE IN EMYDURA SUBGLOBOSA

Out of the 88 potential muscular units of turtles defined in this study (Appendix 1, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14, Figure 15), the following structures were either not present or found in Emydura subglobosa or – in the case of some neck muscles – did not attach to the cranium: Muscular units No. 6, 11-13, 16, 22, 30, 32-33, 35-36, 39, 48, 50, 53-54, 56, 59, 61-62, 65-66, 68, 71, 76, 79, 81-85.

N. Oculomotorius (III) Innervated Musculature

Extraocular Eye Muscles

(Figure 22.2-4)

M. obliquus inferior (No. 1). The bent-shaped muscle originates laterally at half the height of the anterior region of the interorbital septum, medial to the insertion site of m. rectus anterior, (No. 2) and ventral to the course of n. ophthalmicus (V₁) (Figure 22.3-4, Figure 28.2). The muscle runs caudoventrad (Figure 24.2, Figure 28.3-4) and inserts to the posteroventral curvature of the eye bulbus (Figure 22.3, Figure 28.1, 28.3). The cross-section of the belly at insertion is twice that found at the point of origin.

M. rectus anterior (No. 2). The bent-shaped muscle originates at the anterodorsal border of the foramen opticum (Figure 22.4, Figure 28.2). While passing n. ophthalmicus (V₁), ventrolaterally the muscle runs rostrad and keeps a consistent cross section in its course (Figure 22.3, Figure 28.2). The muscle inserts to the anteromedial curvature of the eye bulbus (Figure 28.3).

M. rectus inferior (No. 3). The muscle originates at the anteroventral border of the foramen opticum (Figures 22.2, 22.4, 28.2), ventral to the origin of m. rectus anterior (No. 2). It runs anterodorsad, and instantly it becomes four times broader than its origin site (Figure 22.2). The muscle covers the tractus opticus from medial and spans over the insertion site of this nerve to the eye bulbus. The muscle has a broad insertion on the medial curvature of the eye bulbus (Figure 28.3).

M. rectus superior (No. 4). The primarily bent-shaped muscle originates at the posterior border of foramen opticum (Figure 22.3-4). Medial of the eye bulbus, it runs anterodorsad and passes n. ophthalmicus (V₁) dorsolaterally (Figure 28.2). Below the suture of frontal and parietal, the muscle becomes broad and inserts to the dorsal curvature of the eye bulbus (Figure 22.3, Figure 28.3).

Intraocular Muscles

(Figure 22.1, Figure 24.2)

M. cilliaris (No. 5). M. cilliaris (No. 5) originates with several radial and circumferential fibres in the connective tissue of the ciliar folds and abuts the m. sphincter pupillae (No. 7) internally. It is hard to distinguish both muscles in some regions, because here the former overlaps the latter laterally (Figure 24.2). The circular muscle inserts externally on the ora serrata, the border to the retina.

M. sphincter pupillae (No. 7). The circular muscle stretches around the pupil, and it forms the iris. It originates with several radial and circumferential fibres at the innermost connective tissue of the ciliar folds (König 1934/35). These fibres run externally and insert inside the medial region of the ciliar folds; here they abut the m. cilliaris (No. 5).

M. transversalis oculi (No. 8). The short and narrow muscle (Figure 22.1) is situated anteroventral of the pupil and lateral of m. cilliaris (No. 5). Its origin and insertion are within connective tissue, and some fibres could be associated with fibres of m. ciliaris (No. 5).

N. trochlearis (IV) innervated musculature

Extraocular Eye Muscle

(Figure 22.4)

M. obliquus superior Pars principalis (No. 9). In the hatchling specimen, only an unseparated muscular structure is present (No. 9), which forms the Mutterboden for m. obliquus superior Pars accessorius (No. 10). It originates in the anterior most angle of the ocular cavity. The flat muscle originates laterally from the interorbital septum. The origin site lays medially to the course of n. ophthalmicus (V₁). The muscle runs dorsad and inserts to the anterodorsal curvature of the eye bulbus.

M. obliquus superior Pars accessorius (No. 10). This portion was only discovered in the subadult specimen; it originates laterally to Pars principalis (No. 9) on the prefrontal (Figure 28.2). It runs caudorostrad and dorsad and inserts dorsally onto the eye bulbus, laterally to the insertion of Pars principalis (Figure 28.1).

N. Trigeminus (V) Innervated Musculature

Eyelid Related Musculature

M. depressor palpebrae inferioris Pars transversalis (No. 14). The muscle originates anterior at the ventral border of septum interorbitale and dorsomedially at the vomer. It runs laterad and inserts into the lower eyelid. It is situated anteriorly to Pars equatorialis (No. 15) (Figure 22.1-2) and has crossing fibres with it at its posterior edge (Figure 28.4).

M. depressor palpebrae inferioris Pars equatorialis (No. 15). The flat muscle (Figure 22.2, Figure 24.2, 24.4) originates posteriorly to the eye bulbus within connective tissue (Figure 24.3). It runs rostroventrad and covers the posterolateral curvature of the eye. Ventrally, the muscle continues as a very thin tendon and anteroventrally to the eye bulbus, it inserts within connective tissue. The muscle is not connected to any bone, neither to the postorbital or frontal dorsally nor ventrally at the palatine or pterygoid, which would identify it as m. levator bulbi (No. 16), moreover, in contrast to the latter, No. 15 contains smooth muscle fibres.

Jaw Musculature (constrictor I lateralis)

M. adductor mandibulae externus (No. 17-21). This most prominent cranial muscle originates with three muscle portions from the cranium, these portions partly fuse together and insert to the coronar aponeurosis and the lower jaw in a complex pattern. In the hatchling, the medial most muscle portion, m. adductor mandibulae externus Pars profundus (No. 19), originates from the lateral face of the supraoccipital as a flat muscular structure (Figure 22.5, Figure 23.6, Figure 26.2, Figure 27.1). In the subadult, the portion has extended its origin to the lateral face of the vertical plate and ventrally to the horizontal plate of the parietal (Figure 29.1). Shortly lateral to the parietal, some fibres also originate from the fascia temporalis (compare to Appendix 5), w5ich is spanning above the postorbital cavity of the adductor chamber. Pars profundus (No. 19) runs rostrad and short after the origin site on the supraoccipital, it becomes a strong muscle portion. In the hatchling (Figure 22, Figure 23), the m. adductor mandibulae externus Pars superficialis (No. 21) originates dorsally from the quadrate and from the opisthotic as well as from the dorsomedial face of the squamosal. In the subadult, fibres also originate from the fascia temporalis shortly anterior to the bony bridge formed by squamosal and parietal (Figure 29.1). Pars superficialis (No. 21) is stronger than Pars profundus (No. 19) and has a slightly flattened, roundish shape in cross-section (Figure 26.1). Following the dorsal curvature of the otic capsule, the portion runs anterodorsad shortly after its origin site (Figure 23.6). Dorsal of the quadrate, it runs rostrad (Figure 29.1). Shortly caudal of the bony bridge, the Pars profundus (No. 19) and Pars superficialis (No. 21) begin to partly fuse (Figure 22.5, Figure 26.1). After passing the bony bridge anteriorly, the muscle portions are hard to distinguish in external view and finally they form a consistent muscle belly (Figure 22.1, 22.5, Figure 25.2, Figure 29.1). In serial sections, both muscle portions are still distinguishable (Figure 25.2) because of the strong horizontally orientated coronar aponeurosis (Figure 26.2), which partly separates No. 19 and No. 21 in their medial region. This coronar aponeurosis originates medially in the Pars superficialis portion (No. 21) (Figure 26.2) and becomes strong during its course through the whole muscle (Figure 29.2-3). The muscle fibres of Pars profundus (No. 19) and Pars superficialis (No. 21) by and by insert almost completely to this tendon, the former dorsally and medially, the latter laterally and ventrally (Figure 25.2, Figure 26.1, Figure 29.3). The coronar aponeurosis broadens near to the attachment site and forms the tendinous cartilago transiliens (Figure 22.6, Figure 29.2-4). It continues as a broad and short tendon and inserts around the coronoid of the lower jaw (Figure 22.1, 22.5-6, Figure 25.1, Figure 29.2). Some fibres of the Pars profundus and Pars superficialis (No. 19, 21) do not insert to the coronar aponeurosis and insert posterolaterally from it to the coronoid process of the lower jaw (Figure 25.1). In the hatchling, the third portion of the muscle, m. adductor mandibulae externus Pars medialis (No. 17), originates as a narrow muscle portion ventrally at the anteroventral curvature of the quadrate (Figure 22.5, Figure 23.3). In the subadult, it extended its origin site more dorsad to the anterior curvature of the quadrate (Figure 29.2, Figure 30.3-4). The fibres of Pars medialis (No. 17) run rostrad and anterior to the quadrate, they fuse with the remaining m. adductor mandibulae externus. For a short distance, the whole muscle (No. 17, 19, 21) appears as a homogenous structure, still permeated by the coronar aponeurosis. Posterior to the coronoid, the fibres of Pars medialis separate ventrally from the rest of the muscle (Figure 25.2) – in the hatchling it has the same thickness and vertical altitude as before. It inserts laterally to the anterior part of surangular and the posterodorsal part of the dental (Figure 22.1, 22.5).

M. adductor mandibulae internus (No. 23-28). This muscle is separated into three to four muscle portions. This imprecise number has an ontogenetic reason. In the hatchling specimen (Figure 22, Figure 23), following portions are identifiably: Ventral to the pterygoid bone, a distinct Pars pterygoideus ventralis (No. 28) is present (Figure 23.2, Figure 25.2). Posteriorly to it, the Pars pterygoideus posterior (No. 27) is present (Figure 22.7, Figure 23.2), originating as a flat structure ventrally from the posterior part of the pterygoid and medially to the optic capsule at the anterolateral part of the basisphenoid (Figure 26.1). Dorsally to those both very integrated portions, a muscular structure is present, including one head inserting dorsally to the pterygoid bone as well as to the posterior edge of the palatine. An additional dorsal head originates ventrally to the anteriormost edge of the vertical plate of the parietal as well as to the posteroventral tip of the postorbital and during its posteroventrad course a few fibres originating from the prootic are also incorporated. The former structure is homolog to the Pars pterygoideus dorsalis (No. 26). The latter structure, in contrast, represents the Anlage of Pars pseudotemporalis (No. 23) (Figure 22.3, Figure 23.1-2, Figure 25.2). A close relationship of both structures in turtle development was already reported by Rieppel (1990). In the hatchling, all three portions (No. 27, 28, 23/26) insert with their own distinct fibre course to the posteromedially edge of the lower jaw, namely to the border between angular and cartilago meckeli. In the subadult specimens, the following condition is recognisable: The Pars pterygoideus posterior (No. 27) is located in a more anterior position and originates from the pterygoid only. The Pars pterygoideus ventralis (No. 28) seems to be completely reduced or to be fused with the Pars pterygoideus posterior (No. 27), any anteroventral insertion of m. adductor mandibulae internus to the pterygoid bone is missing. The dorsal structure (No. 23/26) of the muscle is now separated into two distinct structures (Figure 28.1-2, 28.4, Figure 29.4). Pars pterygoideus dorsalis (No. 26) is now clearly distinguished from the pseudotemporalis-structure (No. 23). Moreover, in some specimens, although keeping its origin site, the latter separated completely from the m. adductor mandibulae internus complex (No. 26, 27, 28) and became an independent muscle par definition. Compared to the hatchling, Pars pseudotemporalis (No. 23) extended its origin dorsad and now originates from the whole anterior border of processus descendens parietalis (Figure 28.2, 28.4). Via a short tendinuous structure, the subarticular aponeurosis, it inserts to the ventral edge of the articular, which is situated posteroventrally to the more or less direct attachment of the internus-complex (Figure 17.2). Hence, for some grown-up Emydura subglobosa specimens, one has to acknowledge an m. pseudotemporalis (No. 23) s. s.

M. adductor mandibulae posterior (No. 29).  The muscle originates anterolaterally at the prootic and anteromedially at the quadrate (Figure 22.6-7, Figure 29.4). A few fibres originate at the vertical plate of the parietal, where it contacts the prootic. The belly runs ventrad along the posterior margin of the postorbital cavity of the adductor chamber as a complanate sheet of muscle fibres (Figure 22.7). With a narrow insertion, the muscle attaches dorsally to the surangular and dorsomedially to the cartilago meckeli (Figure 25.2). M. adductor mandibulae posterior (No. 29) is clearly separated from the portions of m. adductor mandibulae internus Partes pterygoidei (No. 26-28) and to m. pseudotemporalis (No. 23) by ramus mandibularis nervi trigemini (V3) (Figure 28.4). In subadult E. subglobosa specimens, it more likely seems to be "related" to portions of m. adductor mandibulae externus (No. 17/19/21).

Jaw Musculature (constrictor I ventralis)

M. intermandibularis (No. 31). The flat and thin muscle stretches transversely between the halves of the lower jaw and posteriorly transverses the symphysis of the dentaries. It originates medially at the cartilago meckeli, dentary, and angular. The contralateral parts are fused together in a thin medial raphe (= insertion site), which is ventrally covered by a high density of pigments. In the hatchling specimen, its anterior most part does not directly contact the symphysis of the dentaries (Figure 23.1, Figure 24.2), whereas in subadult specimens this area is ventrally covered by the muscle (Figure 30.1, 30.3). Posteriorly, m. intermandibularis (No. 31) contacts the n. facialis (VII) innervated intermandibularis part of constrictor colli (No. 42) ventrally (Figure 23.1, Figure 26.1). Laterally between both muscles, a trigonum intermandibulare posterior (Appendix 5) is visible enabling a view to the region around the jaw joint (Figure 23.1, Figure 30.1).

N. abducens (VI) Innervated Musculature

Extraocular Eye Muscles

M. pyramidalis (No. 34). In the hatchling specimen, this flat muscle is the only extraocular eye muscle that does not originate from a bone or the interorbital septum (Figure 28.2). It originates on the ventromedial curvature of the eye bulbus, ventral to the insertion site of m. rectus inferior (No. 3). It runs caudodorsad without changing its thickness. During its course, the muscle is partly covered medially by m. rectus anterior (No. 2) (Figure 22.4) and laterally by m. rectus inferior (No. 3) (Figure 22.2). The muscle forms two short muscle heads. The stronger, posteromedial one develops a strong tendon leading to the lower eyelid in a posterolateral curve. The small, anterolateral head develops a thin tendon leading to the membrana nictitans also in a posterolateral curve. The muscle is dorsomedially innervated by n. abducens (No. VI). In one subadult specimen, I found a different origin pattern of the pyramidalis-structure (No. 34): Herein, its anterior part originates from the eye bulbus, comparable to the condition seen in the hatchling. Posteriorly, the structure is strongly integrated to m. retractor bulbi (No. 38) (Figure 28.2). Following the presented nomenclature of this paper (Figure 1), the pyramidalis-structure in this specimen should be mentioned as a portion of m. retractor bulbi (No. 38). After its "origin sites", the pyramidalis structure itself becomes a continuous muscle with a similar shape as seen in the hatchling, hence no internal portions can be identified (Figure 28.3).

M. rectus posterior (No. 37). The flat muscle originates on the posteroventral border of foramen opticum (Figures 22.4, 25.1, 28.2). While extensively broadening, it runs anteroventrad and has a broad insertion to the posteroventral curvature of the eye bulbus (Figure 22.3, Figure 28.3).

M. retractor bulbi (No. 38). The conical muscle originates in the posteriormost narrow angle of the optic cavity formed by pterygoid, prootic, basisphenoid, and parietal (Figure 25.2). It runs rostrad and has a broad insertion to the posterior curvature of the eye bulbus (Figure 22.3, Figure 25.1, Figure 28.2-3).

N. Facialis (VII) Innervated Musculature

M. constrictor colli (No. 40, 42-43). The parts of m. constrictor colli are not distinctly separated from each other in the hatchling. The Pars aboralis (No. 40) homologue originates laterally on the lig. nuchae (Appendix 5); hence the fibres themselves seem to originate on the underlying m. collooccipitis (No. 80). In fact, both muscles are only connected to each other by connective tissue. The Pars oralis (No. 43) homologue originates from the posterior edge of the squamosal (Figure 27.1). Anteroventrally, it continues to the Pars intermandibularis (No. 42) homologue, which originates with some fibres from the posteroventral tip of the articular. Below the corpus hyoidei, it overlaps the m. intermandibularis (No. 31) dorsally. All three parts of m. constrictor colli indistinguishably insert into a thin medial raphe. Due to the unseparated condition of the muscle in Emydura subglobosa, one should declare all three parts of m. constrictor colli (No. 40-44) together to form only one muscle s. s. having three muscle heads in the origin. Moreover, posteriorly, m. constrictor collis (No. 40-44) is indistinguishably fused with m. sphincter corticis (Ogushi 1913b: his No. 53) that gains spinal nerve support. By definition, both muscle parts, although having different ontogenetic and phylogenetic origin, should be named m. supracorticis. Thus the presented study concentrates on cranium-associated muscles only, and the innervation pattern of both parts are obviously different, I did not list m. supracorticis in Appendix 1 or Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14, Figure 15.  Moreover, an extensive literature review would be necessary to get an impression of the "real" nature of this muscular structure in the trunk near region. Studies expanding the list of muscular units to non-cranium associated postcranial muscles should be aware of this problem and some modification of the here presented list may be necessary in the future.

In subadult specimens, I found a clear separation of the portions of m. constrictor colli (No. 40, 42-43) (Figure 30.1, 30.4). However, Pars aboralis (No. 40) was still indistinguishably connected to m. sphincter corticis (Ogushi 1913b).

M. depressor mandibulae (No. 45). In the hatchling specimen, the strong muscle originates laterally at the posterior curvature of the quadrate (Figure 20.4, Figure 21.3-8, 21.2). Dorsally, only a few fibres come in contact with the ventral edge of the squamosal. In the subadult, the muscle origin expanded dorsad to the lateral face of the squamosal, and a few fibres attach, the posterodorsal border of that bone. As a parallel fibred muscle, it runs anteroventrad and covers the ventral curvature of the otic capsule laterally. Anteroventral of the quadrate, it extends its origin site to the ventral aspect of the quadrate, and the muscle belly broadens. Dorsomedially, the muscle contacts the m. dilatator tubae (No. 46) (Figure 26.2) and the m. constrictor colli (No. 43) posteriorly with connective tissue. Via a short tendon, the muscle inserts dorsolaterally to the posteriormost tip of the articular (Figure 26.1). In the subadult, m. depressor mandibulae (No. 45) seems to be separated into two muscle portions in ventrolateral view (Figure 30.3). However, after redissection of the superficial muscle fibres a homogenous muscle is recognisable (Figure 30.2). In the origin and in the insertion site, the muscle forms different muscle heads, either originating on different positions laterally on the squamosal or also posteroventrally on the opisthotic (Figure 30.2). Those muscle heads do not correspond to the portion-like superficial partition of the muscle; hence, no separation into portions, but a superficial muscle layer s. s. is present.

M. dilatator tubae (No. 46). Separated by the lateral head vein (Rieppel 1990), the muscle originates by two muscle bundles from the ventral face of the lateral lamella of the opisthotic (Figure 27.1, Figure 30.2). Shortly after the origin, the muscle heads fuse and run rostrad. The muscle broadens extensively and surrounds the eustachian tube (Figure 30.2). This skinny element is situated posteroventrally to the groove formed by the incisura columellae auris. The muscle attaches the prootic and the quadrate ventrally (Figure 26.2, Figure 30.2). The thin, anteriormost aspect of the muscle is still connected to the eustachian tube, where the tube opens into the mouth cavity.

N. Glossopharyngeus (IX) Innervated Musculature

M. branchiomandibularis visceralis (No. 47). The long bent shaped muscle originates anteriorly at the distal most part of cornu branchial-I (Figure 22.5-7, Figure 23.1-2, Figure 30.1, 30.3-4, Figure 31.1). Lateral to this bone, it runs anteroventrad (Figure 23.1-2, Figure 27.1, Figure 30.3-4, Figure 31.1) and inserts medially to the angular and articular (Figure 26.1, Figure 30.2-3).

Nn. Vagus (X) et Accessorius (XI) Innervated Musculature

Larynx Musculature (ramus laryngeus sup. of N. vagus; Shiino, 1913)

M. constrictor laryngis (No. 49). The muscle (Figure 22.4, Figure 23.2) originates dorsally in the anterior region of corpus hyoidei and reaches the basis of its processus lingualis (Figure 25.1). It runs caudodorsad and passes cartilago thyreoidea laterally and the m. dilatator laryngis (No. 52) medially (Figure 25.2). The muscle bends mediad around the curvature of cartilago thyroidea and inserts with the contralateral muscle in a median raphe, which is anterodorsal to cartilago cricoidea.

M. dilatator laryngis (No. 51). The bent shaped muscle originates on the lateral tip of the processus muscularis of cartilago arytaenoidea. It runs caudad and passes m. constrictor laryngis (No. 49) laterally. It inserts laterally in the posterior part of cartilago thyreoidea and a few fibres insert to the first tracheal ring.

M. plastrocapitis (No. 52). The muscle originates with a thin diameter medially on the dorsal face of the entoplastron (Figure 31.1). It runs rostrodorsad into the neck (Figure 30.4, Figure 31.1, 31.4). In the posterior part of the neck, it lays ventrolaterally of the m. coracohyoideus Pars principalis (No. 58) (Figure 31.1). At the level of the third cervical vertebrae, it passes this muscle dorsally and lies medially of it in the anterior part of the neck (Figure 23.4: hatchling). In its whole course, m. plastrocapitis (No. 52) is strongly connected to m. coracohyoideus (No. 58) via connective tissue. After passing m. coracoideus Pars principalis (No. 58), the elongated m. plastrocapitis (No. 52) becomes a very thin muscle that attaches the cornu branchial-I medially with a few muscle fibres (Figure 23.4, Figure 30.4, Figure 31.1). Afterwards, the remaining muscle fibres run rostrad to insert into lig. hyosquamosal (Ogushi 1913b), which is stretched between cornu branchial-I and the posterior part of the otic. In the dissected specimens, the anterior part of the muscle appeared to be slightly brighter than all other muscles in the neck, possibly due to several internal tendinuous fibres (Figure 30.4, Figure 31.1).

N. Hypoglossus (XII) Innervated Musculature

Tongue Muscles and Rectus System

M. branchiohyoideus (No. 55). The massive, parallel fibred muscle originates at the medial third of cornu branchial-I (Figure 22.5-7, Figure 30.1, 30.3). Here it originates from almost all sides of this bar-shaped bone. Only a narrow longitudinal, vertical area at the medial side of cornu branchial-I is not covered by the muscle in this region (Figure 27.1). The muscle fibres run rostrad (Figure 30.4). The dorsal fibres insert to the posteromedial face of cornu hyale (Figure 23.2). The ventral and medial fibres insert to the lateral and ventrolateral face of corpus hyoidei, around the articulations of cornu hyale and cornu branchial-I with corpus hyoidei (Figure 22.4, Figure 23.2, Figure 25.1).

M. collosquamosus (No. 57). By a tendon, the conical muscle originates ventrolaterally from the forth cervical vertebrae. In the hatchling, its origin site is not visible, possibly either because of the abrupt end to the serial sections or intraspecific variability with an appreciable origin from the fifth cervical vertebrae. The muscle runs rostrodorsad and laterad (Figure 30.4, Figure 31.1-2, 31.4) and broadens extensively (Figure 23.4). In the hatchling specimen, the lateral muscle head inserts dorsolaterally to the distal third of cornu branchial-I and to the posterior edge of the squamosal (Figure 23.4, Figure 27.2); a very short medial head inserts to connective tissue posterior to the skull. The insertion of collosquamosus (No. 57) to cornu branchial-I is not present in the subadult; however, it is connected via connective tissue.

M. coracohyoideus (No. 58, 60). The flat but strong muscular unit m. coracohyoideus Pars principales (No. 58) originates posteriorly from the proximal fifth of the coracoid bone of the pectoral girdle (Figure 31.2-3). It turns dorsad around the coracoid and runs rostrad. The portion forms the ventral margin of the neck region (Figure 23.4, Figure 27.2, Figure 31.1, 31.4), and it is only superficially covered by the inserting parts of the neck constrictors [No. 40, 42, 43, m sphincter corticis (Ogushi 1913b), Figure 30.2-3, Figure 27.2, Figure 30.4]. It inserts posteromedially to cornu branchial-I (Figure 23.4, Figure 31.1), ventrolaterally to the proximal part of cornu branchial-II (Figure 23.1, Figure 27.2), ventrally and laterally to the skull near the trachea (Figure 26.2, Figure 27.1, Figure 31.1), as well as ventrally to the posterior half of corpus hyoidei (Figure 26.1). In the area of the hyoid apparatus, it dorsolaterally shares fibres with m. coracohyoideus Pars interbranchialis (No. 60) (Figure 26.1-2, Figure 27.1).  The parallel fibred muscular unit M. coracohyoideus Pars interbranchialis (No. 60) originates from the dorso- and ventrolateral face of the medial third of cornu branchial-II (Figure 22.5, Figure 23.1-2, Figure 31.1). It runs rostrad (Figure 23.1) and inserts ventomedially to the proximal third of cornu branchial-I (Figure 26.1, Figure 31.1). Postero- and ventromedially, this portion shares fibres with m. coracohyoideus Pars principalis (No. 58) (Figure 26.1-2, Figure 27.1).

Mm. genioglossus (No. 63) et hypoglossoglossus (No. 69). Those muscular units are not clearly separated from each other in the hatchling stage of Emydura subglobosa. The structure originates dorsally at cartilago meckeli, laterally to the symphysis of the dentaries (Figure 23.1-2, Figure 24.2). The fibres run caudolaterad and form two muscle heads dorsally to the anterior most part of hypoglossum (Figure 23.2). The longer, lateral head of the muscular complex inserts to the anterolateral edge of the hypoglossum, some fibres insert ventrally to the lateral aspect of hypoglossum (Figure 23.1-2). It is homologous to the posterior part of m. genioglossus (No. 63). Laterally to the anterior most tip of processus lingualis of corpus hyoidis, the short medial muscle head – the m. hypoglossoglossus homologue (No. 69) – runs caudad and inserts to the dorsal integument of the tongue. Here it anteriorly and directly opposes the insertion site of m. hyoglossus (No. 67). In subadult and adult specimens, the differentiation of both structures was much clearer, however, they still were not completely separated from each other (Figure 31.1).

M. geniohyoideus (No. 64). The flat and broad muscle (hatchling) covers the ventral surface of the hyoid apparatus, and it is situated dorsally to m. intermandibularis (No. 31). The major muscle head originates along the ventromedial surface of the proximal half of cornu branchial-I (Figure 23.1, Figure 25.2). The muscle fibres run rostromediad. A small muscle head originates from the ventral face of articular and angular, and its muscle fibres incorporate into the whole muscle (Figure 23.1). The muscle inserts broadly to the thin medial raphe it shares with the contralateral geniohyoideus (Figure 25.2), as well as on the medial aspect of corpus hyoidei and at the posterior edge of hypoglossum (Figure 23.1). In the subadult/adult, no connection to the lower jaw is present (Figure 30.1, 30.3-4).

M. hyoglossus (No. 67). The major head of the muscle originates at the ventral aspect of the anterior most part of cornu branchial-I, lateral to the articulation of this bone to corpus hyoidei (Figure 23.1, Figure 31.1). Some muscle fibres run rostromediad (Figure 30.3) and a few fibres, originating medially from the corpus hyoidei, between processus lateralis anterior and processus lateralis intermedius, incorporate into the muscle. A small muscle head originates ventrolaterally from cornu hyale. Anterior to the processus lateralis anterior and lateral to the processus lingualis of corpus hyoidei, the course of the muscle changes to dorsomediad (Figure 23.2). Dorsally to the hypoglossum and at the level the anterior most tip of processus lingualis, the muscle inserts to the dorsal integument of the tongue (Figure 22.4, Figure 23.2).

M. hypoglossohyoideus (No. 70). The very small, thin, bent-shaped muscle originates laterally at the distal part of processus lingualis of corpus hyoidei. It runs caudad and has a ventrolateral course (Figure 23.2). It inserts dorsally to the hypoglossum.

Linguae-muscles (No. 72-74). I was able to identify several separated longitudinal and transverse as well as a few vertical muscle fibres in the tongue. Thus I only had access to a serial section series of a hatchling specimen, I am currently not able to state, whether the identified structures are linguae muscles (No. 72-74) or if they belong to the Anlagen of mm. genioglossus (No. 63) et hypoglossoglossus (No. 69) as described above. Sections of adult specimens as well as a comprehensive set of sections of other species are necessary to clearly identify such structures.

Cranium Associated Musculature Innervated by Cervical Nerves ("neck muscles") (nn. Sd/v)

Epaxial Musculature (n. Sd)

M. atlantoepistropheooccipitis (No. 75). The muscle originates laterally at the neural arches up to the lateral processi of the first and second cervical vertebrae; some fibres also originate from the anterior zygapophysis of the third cervical vertebrae (Figure 23.5). The fibres run ventrolaterally (Figure 27.2, Figure 30.4) and attach the exoccipital and opisthotic posteriorly (Figure 23.5, Figure 29.1).

M. atlantooccipitis (No. 77). The conical muscle broadly originates from the whole transverse process of the first cervical vertebrae (atlas) (Figure 23.5-6). It runs anteroventrad and reduces its diameter (Figure 27.2, Figure 30.2). With a small insertion area, it inserts posteromedially to the ventral face of the opisthotic (Figure 23.5-6), shortly next to the suture of the opisthotic to the basioccipital.

M. atlantoopisthoticus (No. 78). The parallel fibred muscle originates laterally from the neural arch of the atlas, runs rostrolaterad and slightly dorsad (Figure 29.1) and inserts posterodorsally to the opisthotic, directly between the origin sites of m. adductor mandibulae externus (No. 19, 21) (Figure 23.6, Figure 27.1, Figure 29.1).

M. collooccipitis (No. 80).  The very massive, parallel fibred dorsal neck muscle originates with three muscle heads dorsally form the neural arches of cervical vertebrae-I to -IV (Figure 23.3-6). It runs rostrad (Figure 27.1-2, Figure 30.4, Figure 31.2, 31.4), completely covers m. atlantoopisthoticus (No. 78) dorsally, and inserts directly into the fascia temporalis posterostegalis, which is spanning between the posterior edge of squamosal, the parietal and the supraoccipital (Appendix 5).

Hypaxial Musculature (n. Sv)

M. longus colli Pars capitis-I et -II/III (86-87). It is not possible to separate both muscle portions in the hatchling specimen via three muscle heads. The muscular structure originates directly at the ventral parts of the centra of cervical vertebrae-I to -III, a fourth head leads caudad to cervical vertebrae -IV (Figure 23.6), but connects to non-cranial portions of the whole m. longus colli complex. Shortly before the structure inserts to the basioccipital, it splits into a thin lateral head and a large medial (Figure 27.1), which reaches far more rostrad than the lateral one (Figure 26.2). The medial may be homologous to the anterior part of Pars capitis-I (No. 86), while the lateral one may be homologous to the inserting part of Pars capitis-II/III. In the subadult/adult specimens, a clearer separation of the portions is distinct (Figure 30.1).

M. retrahens capiti collique Pars carapacobasioccipitale (No. 88). This longest muscle in the turtle body originates medially from the ventral face of the 7^th to 8^th costal plate, ventrolaterally from the 7^th to 8^th dorsal vertebrae, and ventrally from the distal end of the related ribs. Some fibres also originate anteriorly from the 9^th costal plate (Figure 31.4). The portion runs rostroventrad, and it is situated between m. longus colli (No. 86-87 + related portions) and the oesophagus (Figure 23.5, Figure 27.2, Figure 31.1). Via a long tendon, it inserts ventrally at the basioccipital, anteriorly to the cranial portions of m. longus colli (No. 86-87) (Figure 23.5, Figure 26.2).