. Bulletin of the British Museum (Natural History), Geology. . Fig. 48 Caturus sp. from the Lower Kimmeridgian of Bavaria, P44900. Region of right jaw articulation. of Ospia (Stensio 1932: 252), as well as in Amia. The palate of macrosemiids usually ossifies fully, although a gap may persist between the metapterygoid and quadrate. The neopterygian quadrate is associated with a separate ossification of the hyomandibular cartilage, the symplectic, and with a dermal bone, the quadratojugal. Patterson (1973) has dis- cussed at length the relationships between these three elements. Three patterns m
. Bulletin of the British Museum (Natural History), Geology. . Fig. 48 Caturus sp. from the Lower Kimmeridgian of Bavaria, P44900. Region of right jaw articulation. of Ospia (Stensio 1932: 252), as well as in Amia. The palate of macrosemiids usually ossifies fully, although a gap may persist between the metapterygoid and quadrate. The neopterygian quadrate is associated with a separate ossification of the hyomandibular cartilage, the symplectic, and with a dermal bone, the quadratojugal. Patterson (1973) has dis- cussed at length the relationships between these three elements. Three patterns may be recognized. In Lepisosteus, Lepidotes and Dapedium (Patterson 1973 : figs 6, 26) the quadratojugal is an elongated bone lying along the upper edge of the ventral arm of the preopercular; the anterior end of the bone abuts against the articular condyle of the quad- rate. No fusion occurs between the quadratojugal and quadrate in Lepisosteus and in Patterson's specimens of Lepidotes and Dapedium. In none of these forms does the symplectic come into contact with the mandible. In Lepisosteus the symplectic is small and remote from the quadrate; in Lepidotes and Semionotus it forms a long rod lying medial to the quadrate and quadratojugal. The second pattern is found in living teleosts and their fossil relatives. The quadratojugal is probably represented by the spine-like posterior process of the quadrate, as held by Holmgren & Stensio (1936 : 463). This condition is advanced relative to that of Lepisosteus, in which the quadratojugal remains discrete. The symplectic of teleosts is typically a long tapering bone which is inserted into a groove formed between the quadrate and its posterior process on their inner surface; thus in these fish too no contact between the symplectic and the lower jaw occurs. 211. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrat
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