. Bulletin of the British Museum (Natural History), Geology. 298 REDFIELDIIFORM AND PERLEIDIFORM similarity between the two genera is impressive (cf. Fig. 35 and Schaeffer 1955 : text- fig, i). The differences between the cheek regions of Manlietta and Mendocinia can be related to the fact that the suspensorium is more vertical in the latter. This difference is accompanied by a reduction in the width of the preopercular, and considerable reduction of the posterior part of the maxilla. Other changes can be seen in the anatomy of the fins. In Manlietta the unpaired fins bear fringing fulcra, but
. Bulletin of the British Museum (Natural History), Geology. 298 REDFIELDIIFORM AND PERLEIDIFORM similarity between the two genera is impressive (cf. Fig. 35 and Schaeffer 1955 : text- fig, i). The differences between the cheek regions of Manlietta and Mendocinia can be related to the fact that the suspensorium is more vertical in the latter. This difference is accompanied by a reduction in the width of the preopercular, and considerable reduction of the posterior part of the maxilla. Other changes can be seen in the anatomy of the fins. In Manlietta the unpaired fins bear fringing fulcra, but these are lost in Mendocinia; also, whereas in Manlietta the basal fulcra of the anal and dorsal fins do not exceed the length of the proximal lepidotrichia, in Mendocinia they extend almost to the distal ends of the anterior rays. There are several reasons for supposing that, although closely related, Manlietta is not ancestral to Mendocinia. The preopercular of Manlietta is subdivided and there is no postorbital element, and the anal iin-rays are unusually long. More important is the anatomy of the snout. In Manlietta the postrostral has been lost and the nasals meet in the midline. In consequence the nostril cannot lie at the anterior margin of the nasal, and is situated at the ventral edge of the nasal. This condition is paralleled in Birgeria and Haplolepis, although in these forms the post- rostral is still present, and reasons for migration of the nostril from the position more typical of lower actinopteryians are obscure. Manlietta crassa Wade (Figs 35-37) 1935 Manlietta crassa Wade: 59-62, text-figs 29-30, pi. 9, fig. i. Horizon and locality. Ladinian (?). 560 feet above the base of the Hawkes- bury Sandstone, Beacon Hill, Brookvale, Diagnosis. As for the genus Manlietta. HoLOTYPE. Fig. 35. Restoration, X2approx. Scales Please note that these images are extracted from scanned page images that may have been digitall
Size: 2451px × 1020px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbritishmuseumnaturalhistory, bookcentury1900, bookcoll
