(4) Musculi nonstriati dermatis is a collective term for smooth muscles within the dermis (as defined by Lucas and Stettenheim, 1972:483, Fig. 294).  These muscles consist of two principal types:  feather muscles and apterial muscles.  See Fig. 6.1.


Feather muscles (Musculi pennarum; Synonymy: Mm. pennales (NAA, 1979) are attached at each end by elastic tendons (Tendo  elastica) to the connective tissues of the external follicle walls of contour, semiplume, bristle, and body down feathers (Lucas and Stettenheim, 1972, Chap. 8).  Filoplumes lack feather muscles.  Basically feather muscles have a simple to complex parallelogram arrangement and function as erectors, depressors, retractors, and rotators (Langley, 1904: 242).


Lange (1931) designated the apterial muscles (Mm.apteriales) as a "Stratum musculo-elasticum";  these muscles lie within loose connective tissue of the dermis (Stratum laxum) but do not form a distinct layer.  In Gallus, they are most abundant in the following apteria: scapular (caudal part), pectoral, and lateral areas of the trunk,  pelvis, and tail.  Elastic tendons also connect apterial muscles with feather muscles.


Musculi pterylarum.  Synonymy: Musculi cutanei, after NAV,1983:A-41; "dermal muscles" (Lucas and Stettenheim,1972: 505).  Thin sheets or narrow bands of striated muscle lie in both the transverse (circular) and longitudinal planes of the neck within the superficial fascia (Tela subcutanea). They lie adjacent to or beneath large cervical feather tracts (e.g., M. constrictor colli, Annot. 6;  M. cucullaris, Annot. 7,8,and 10 ) and abdominal feather tracts (Pars subcutanea, M. pectoralis, Annot. 12).  Others may attach on the innermost lamina of a feather tract itself (Pars scapulohumeralis of Mm. latissimus dorsi and serratus superficialis, Annot. 11), but do not attach to the individual feather follicles.  They have a role in positioning one feather tract to an adjacent tract and thereby presumably smoothing out the surface contour of the body (Osborne, 1968).  For this reason, they are named "muscles of the feather tracts" (following Petry, 1951).


(5)  M. expansor secundariorum.  Synonymy: M. dermo-ulnaris (Owen,1842). This nonstriated muscle may have a single belly, or it may consist of a proximal tendon, and a distal fan-shaped belly associated with a distal tendon.  Tendo proximalis attaches to the deep fascia of muscles (especially M. scapulohumeralis caudalis) attaching on the scapula and coracoid, or directly on the two bones, extending as far as the sternocoracoidal articulation in some taxa.  In other taxa,  the tendon extends distally into the wing beneath the subhumeral apterium and is continuous with attachments of the scapulohumeral slips from Mm. serratus superficialis and latissimus dorsi (Annot. 11). Tendo  distalis (Tendo humeralis) is attached to the humerus (Epicondylus ventralis) or to the humeroulnar pulley (Trochlea humeroulnaris, pars pennata, Arthr. Annot. 110), and directly on the follicles of two to six of the most proximal secondaries at the elbow.   See, e.g., descriptions of Berger (1966); Vanden Berge (1970), and Fig. 6.12.