Volume 11 1968

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A comparison of the palates of Permian and Triassic dicynodonts
(Bernard Price Institute for Palaeontological Research, 1968) Cruickshank, A. R.
Whilst comparing the skulls of some Triassic dicynodonts with Permian members of the family, it was noted that the interpterygoid space in the former is consistently smaller than in the latter (Cruickshank 1965: 1967). In analysing this difference further, the palates of a series of Permian and Triassic dicynodonts were examined, either directly or from published diagrams. From graphs drawn using the various measurements taken from the palates, the geological age of the specimens can be deduced as can their estimated lengths, if fragmentary.
Tooth structure in Rhizodus hibberti Ag., a rhipidistian fish
(Bernard Price Institute for Palaeontological Research, 1968) Cruickshank, A. R.
The structure of the large laniary teeth of the Lower Carboniferous rhipidistian fish Rhizodu hibberti Ag. is interpreted in terms of a new theory of tooth development. The structure of these teeth is found to correspond almost exactly to that of the synchronomorial scale as defined by Orvig (195 1) and Stensio (1961 ; 1962). These labyrinthodont teeth are thus shown to be composed of many tooth primordia, and are not a single unit of dentine. Some isolated Rhizodus teeth are described in which the entire labyrinthodont structure is missing, leaving an empty space inside the tooth. From this, a non-mechanical tooth removal mechanism is postulated.