Anhanguera adductor subsp. mandibulae

Pêgas, Rodrigo V, Costa, Fabiana R & Kellner, Alexander W A, 2021, Reconstruction of the adductor chamber and predicted bite force in pterodactyloids (Pterosauria), Zoological Journal of the Linnean Society 193 (2), pp. 602-602 : 602-

M. adductor mandibulae externus medialis (mAMEM)

Origin: This muscle, together with mAMEP and mPSTs, also originates from the margins of the upper temporal fenestra, this seems to be consistent throughout sauropsids in general ( Holliday & Witmer, 2007) except for turtles ( Werneburg, 2011).

mAMEM is located medial to mAMES and originates from the lateral border of the upper temporal fenestra (on the squamosal bone, as in lepidosaurs and modern birds). However, the exact extent over this border from which this muscle originates is often hard to observe in living taxa and even harder to interpret in fossil taxa mostly because this attachment is provided by an aponeurosis that leaves no clear osteological correlates (e.g. Holliday & Witmer, 2007).

Insertion: The insertion site of mAMEM is even harder to interpret. In living taxa this muscle often blends with mPSTs or mAMES when inserting on the mandible and is usually located posterior to mPSTs and medial to mAMES. This site corresponds to the coronoid eminence in modern crocodylians and to the lateral surface of the coronoid region in modern birds, and to the dorsolateral surface of the surangular in lepidosaurs ( Holliday & Witmer, 2007) and possibly the dorsomedial surface of the surangular in some dinosaurs ( Holliday, 2009). Faint muscle scars can be seen on the dorsal surface of the surangular in the holotypes of An. araripensis , Th. sethi and some pteranodontid specimens ( Fig. 16 ).

As further explored below, the dorsolateral surface of the surangular seems to contain the insertion of mAMES, especially the lateral surface. It seems likely that in pterosaurs the insertions of mAMEM and mAMES did partially blend on the dorsal surface of the surangular (see more on mAMES below).

Figures

Figure 16. Mandibular rami in dorsal view. A, Aymberedactylus cearensis holotype (MN 7596-V), right ramus. B, Thalassodromeus sethi holotype (DGM 1476-R), left ramus. C, Anhanguera araripensis holotype (BSPG 1982 89), left ramus. D, Pteranodon sp. YPM 2410, left ramus. E, Pteranodon sp. LACM 51130, left ramus. Arrowheads indicate muscle scars. Scale bars = 10 mm. Abbreviations: adfo, adductor fossa; defo, fossa depressoria; lc, lateral cotyle; mc, medial cotyle; rapr, retroarticular process.