. Bulletin of the British Museum (Natural History), Geology. FISHES OF THE TRIASSIC 243 There are faint traces of grooves running parallel to its anterior margins. Although damaged, this bone appears to have been bilaterally symmetrical, and is therefore a mid-line element; probably a median gular. In a specimen on block , a fragment of the right dermohyal is fused, or at least is in close contact, with the underljang hyomandibular. There is a tiny element lying ventral to the dermohyal, inserted between the antero-dorsal corner of the subopercular and the posterior margin of the preope
. Bulletin of the British Museum (Natural History), Geology. FISHES OF THE TRIASSIC 243 There are faint traces of grooves running parallel to its anterior margins. Although damaged, this bone appears to have been bilaterally symmetrical, and is therefore a mid-line element; probably a median gular. In a specimen on block , a fragment of the right dermohyal is fused, or at least is in close contact, with the underljang hyomandibular. There is a tiny element lying ventral to the dermohyal, inserted between the antero-dorsal corner of the subopercular and the posterior margin of the preopercular. This element corresponds with the accessory opercular recorded in many palaeoniscoids ( Watsonichthys, Gardiner 1963). It is seen only on the medial surface of the cheek (Fig. 3), laterally it is covered by the antero-dorsal corner of the opercular. The preopercular has similar proportions to that of Brookvalia, except that its anterior limb extends antero-ventrally for a short distance dorsal to the antero- dorsal border of the maxilla. Along the posterior part of the suture between the preopercular and the maxilla there is a very shallow medial lamina on the preopercular which underlaps the maxilla (Fig. 3). Further anteriorly there is a groove in the antero-dorsal edge of the maxilla which receives the antero-ventral part of the preopercular. Ornament on the maxilla consists of tubercles and some elongate rugae which radiate from the point on its ventral margin which lies below the posterior edge of the orbit. The posterior infraorbital is expanded posteriorly and has a complex postero-dorsal edge: it butts against the postorbital and the antero- ventral tip of the preopercular and, between these two contacts, is notched to receive ridge soc fr. ro Fig. 3. Ischnolepis bancrofti Haughton. : cheek, left side internal view; roof, impression of left Please note that these images are extracted from scanned page images that may have been digitally enhance
Size: 2062px × 1212px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbritishmuseumnaturalhistory, bookcentury1900, bookcoll
