Extrinsic muscles of tongue namely genioglossus, hyoglossus
, styloglossus and palatoglossus are responsible for positioning the tongue in the oral cavity.
Generally, the extrinsic muscles--including the genioglossus, the hyoglossus
, the styloglossus, and the palatoglossus--tend to move the position of the whole tongue, while the intrinsic muscles change its shape.
The agamid tongue projection mechanism appears to be an ideal mechanical precursor for the ballistic tongue projection mechanism of chameleonids; the key derived feature in the chameleon tongue projection mechanism most likely lies in the changed motor pattern controlling the hyoglossus
muscle (Herrel et al., 1995).
From stage 42 onward, the paired hyoglossus
muscles are present medially to the paired geniohyoideus (Fig.