. Bulletin of the British Museum (Natural History), Geology. 274 TWO UPPER CRETACEOUS SALMONIFORM both Astronesthidae), Chaiiliodus (Monod 1968, fig. 396 ; Chauliodontidae) and Idiacanthus (Beebe 1934, figs. 74, 78 ; Idiacanthidae). A free second ural centrum is present in Polymetme, Borostomias antarcticus and possibly in Maurolicus, and in this the stomiatoids are more primitive than osmeroids. In Polymetme and Gonostoma there are six autogenous hypurals, but in other forms there may be only five [Photichthys, astronesthids, Chauliodus) or there are various fusions. In Maurolicus and Vincigu
. Bulletin of the British Museum (Natural History), Geology. 274 TWO UPPER CRETACEOUS SALMONIFORM both Astronesthidae), Chaiiliodus (Monod 1968, fig. 396 ; Chauliodontidae) and Idiacanthus (Beebe 1934, figs. 74, 78 ; Idiacanthidae). A free second ural centrum is present in Polymetme, Borostomias antarcticus and possibly in Maurolicus, and in this the stomiatoids are more primitive than osmeroids. In Polymetme and Gonostoma there are six autogenous hypurals, but in other forms there may be only five [Photichthys, astronesthids, Chauliodus) or there are various fusions. In Maurolicus and Vinciguerria hypurals 1 + 2 and 3 + 4 are fused, and there are two slender, autogenous hypurals above, as in Gaudryella, while Vinciguerria has these two hypural plates and the parhypural fused with the compound centrum. Boro- stomias, Polymetme and Photichthys have an autogenous stegural of typical shape, but the stegural is fused with the centrum in other genera. There is a second uroneural ep'l-2 un3 pu1»ul+u2*st. 2 mm Fig. 43. Hypoinesus olidiis (Pallas), Recent. Caudal skeleton of a stained and macerated individual, same specimen as Fig. 29B. On the right is the detached sixth hypural in dorsal view. Explanation of abbreviations p. 296. in all genera except Polymetme and Chauliodus, but none has a third. There are three epurals in Gonostoma, two or one in other genera. All stomiatoids have a full neural spine on PU2, and in this they are more advanced than osmeroids, Gaudryella and Humbertia. No stomiatoid is known to have caudal scutes or a urodermal. There is clearly a wide range of caudal structure in stomiatoids, and no one genus can be clearly characterised as more primitive than the others. The occurrence of a second ural centrum, an autogenous stegural and three epurals in some forms shows that the stomiatoid caudal skeleton cannot be derived from the osmeroid Please note that these images are extracted from scanned page images that may have been digitally enhanced
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