Fig. 2

Morphometric analysis of head shape differences between CA, DC and F1 hybrids. a–c Lateral views of the skinned and alizarin red-/alcian blue-stained heads of CA (a), DC (b) and F1 (c) specimens. Scale bar 1 cm. b Anatomical landmarks examined: 1 anterior tip of the dentary, 2 antero-ventral corner of the dentary, 3 insertion of the interopercular ligament on the articular, 4 articular-quadrate joint (lower jaw joint); 5 postero-dorsal corner of the maxilla, 6 dorsal-most point on the origin of the A1 subdivision of the adductor mandibulae (jaw closing) muscle on the preopercular, 7 dorsal-most point on the origin of the A2 division of the adductor mandibulae on the preopercular, 8 ventral-most point on the origin of the A2 division of the adductor mandibulae on the preopercular, 9 antero-ventral edge of the eye socket, 10 postero-ventral edge of the eye socket, 11 dorsal-most tip of the supraoccipital crest on the neurocranium, 12 joint between the nasal bone and the neurocranium, 13 posterior-most point of the operculum, 14 ventral-most point of overlap between the interoperculum and the suboperculum, 15 posterior tip of the ascending process of the premaxilla, 16 maxillary-palatine joint (upper rotation point of the maxilla), 17 postero-ventral corner of the maxilla, 18 anterior tip of the premaxilla. d Anatomical landmarks shown on CA head Camera Lucida drawing. e First canonical variate (CV1) deformation vectors on CA landmark configuration. Asterisks indicate Bookstein landmarks. f Mean and distribution of CA (n = 15), DC (n = 12) and F1 (n = 16) individuals along the CV1 axis, expressed in within-species standard deviation units. g–i Dorsal views of skinned and alizarin red-/alcian blue-stained heads of CA (g), DC (h) and F1 (i) specimens. Scale bar 1 cm. j Anatomical landmarks examined shown in h: 1 anterior tip of the premaxilla, 2 and 6 lateral-most point in the preorbital region of the frontal, 3 and 5 lateral-most point in the postorbital neurocranium (sphenotic); 4 posterior tip of the supraoccipital crest. j Anatomical landmarks shown on CA head Camera Lucida drawing. k CV1 deformation vectors on CA landmark configuration. l Mean and distribution of CA (n = 15), DC (n = 12) and F1 (n = 16) individuals along the CV1 axis, expressed in within-species standard deviation units. **p < 0.001, Bartlett’s test