. Bulletin. Natural history; Natuurlijke historie. B Fig. 2. Portion of the left side of the skull roof in three specimens of Devonian Dipnoi, showing variation in dermal bone pattern. A) Dipterus valenciennesi, "normal situation," specimen 33165, British Museum (Natural History); B) Dipterus valenciennesi, specimen showing possible fusion of X and K and subsequent modification of the lateral-line canal pattern, specimen 33165, British Museum (Natural History); C) Scaumenacia curta, "normal condition ' showing that in this case bone K has been eliminated, specimen E 2853, Park M
. Bulletin. Natural history; Natuurlijke historie. B Fig. 2. Portion of the left side of the skull roof in three specimens of Devonian Dipnoi, showing variation in dermal bone pattern. A) Dipterus valenciennesi, "normal situation," specimen 33165, British Museum (Natural History); B) Dipterus valenciennesi, specimen showing possible fusion of X and K and subsequent modification of the lateral-line canal pattern, specimen 33165, British Museum (Natural History); C) Scaumenacia curta, "normal condition ' showing that in this case bone K has been eliminated, specimen E 2853, Park Museum. Redrawn from Westoll (1949) and White (1965). 1956 and 1967). We would like to re-emphasize the importance of relation to the structures of the chondrocranium, particularly in the identification of the posterior roofing bones. 3) A standard for the comparison of dermal bone patterns must be established. In the past the skull roof of Dipterus has been used as a standard, following the work of Forster-Cooper (1937). However, Dipnorhynchus sussmilchi (and also Uranolophus) presents a more complex pattern that is both geologically and phylogenetically more primitive. Bones unknown in Dipterus now have to be named. Moreover, since the Forster-Cooper system of notation can be adapted to Dipnorhynchus with only minor modifications, and since a comparative study of Dipnorhynchus helps clear up certain problems in the interpretation of Dipterus itself and other forms (see below), we choose Dipnorhynchus as a new basis for com- parison. 4) An integrated sequential system of analysis should replace the current ad hoc approach to the identification of bones. That is, using a given bone as a primary reference point, other bones should be defined in sequence; each definition must be cast only in terms of entities defined earlier in the sequence. 5) The initial reference bone must be one that can be readily recognized in all genera, is not the subject of argument about fusion or splitt
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