. Bulletin of the British Museum (Natural History) Zoology. 150 G. J. HOWES & AYANOMIYA FUMIHITO EPX LAP DO ET. AAP Fig. 18 Belodontichthys dinema: superficial cranial musculature; dashed lines indicate the underlying DO and LAP muscles (LILI 89002). long, rod-shaped bone, unlike the nodular element of the Siluridae). Among other siluroids examined, only in Hypophthalmidae does the extensor run longitudinally from the rear of the orbit. In this case, however, the muscle originates from the body of the adductor arcus palatini along the dorsal border of the posterior pterygoid, whereas in si
. Bulletin of the British Museum (Natural History) Zoology. 150 G. J. HOWES & AYANOMIYA FUMIHITO EPX LAP DO ET. AAP Fig. 18 Belodontichthys dinema: superficial cranial musculature; dashed lines indicate the underlying DO and LAP muscles (LILI 89002). long, rod-shaped bone, unlike the nodular element of the Siluridae). Among other siluroids examined, only in Hypophthalmidae does the extensor run longitudinally from the rear of the orbit. In this case, however, the muscle originates from the body of the adductor arcus palatini along the dorsal border of the posterior pterygoid, whereas in silurids its origin covers a broad area of the posterior part of the adductor arcus palatini and encroaches on the para- sphenoid, orbitosphenoid, pterosphenoid and, in Wallago, also on the sphenotic. In most other silurids the retractor tentaculi originates from a connective tissue fascia covering the posterior pterygoid medial to muscle A2. In Wallago, as in Belodontichthys there are two distinct segments of the retractor, the upper of which inserts on the base of the barbel, the lower passing beneath the upper segment to insert at the midpoint of the maxilla (Fig. 21C). Only in Kryptopterus cryptopterus is there a connection of the extensor with the premaxilla as in Belodontichthys. Belodontichthys most closely resembles Kryptopterus bicirrhis in its relatively short retractor and in the muscle's origin from the anterior pterygoid. Bornbusch (1990) has pointed out that the length and orientation of the retractor tentaculi in most Siluridae is a probable correlate of the shortened palatine. The distribution of a retractor tentaculi amongst siluroids has not been documented. Howes (1983a) drawing on a limited survey of Old and New World taxa, supposed that the muscle had been derived independently in several lineages. No evidence has emerged from this study to alter that opinion. In all of the Siluridae, the levator arcus palatini (LAP) is extensive, originating from the sphenot
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