. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. The Jiatural History of the Frilled Shar\ 311 These statements have all been checked against the figures of the teeth referred to, and we beHeve that, so far as we can judge from the structure of the teeth, Chlamydo' selachus has no generic relationship with Diplodus { = Didymodus). With regard to its affinities to Cladodus, Dr. W. K. Gregory comments as follows: ''Some authors regard Chlamydoselachus as a living representative of the cladodont sharks of the Devonian and Carboniferous periods, but later inves
. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. The Jiatural History of the Frilled Shar\ 311 These statements have all been checked against the figures of the teeth referred to, and we beHeve that, so far as we can judge from the structure of the teeth, Chlamydo' selachus has no generic relationship with Diplodus { = Didymodus). With regard to its affinities to Cladodus, Dr. W. K. Gregory comments as follows: ''Some authors regard Chlamydoselachus as a living representative of the cladodont sharks of the Devonian and Carboniferous periods, but later investigations indicate that it is only a deep'water specialisation of a Meso2;oic ; The teeth of Chlamydoselachus (Text'figure 10) are barb'like, prehensile, and aUke in both jaws. Those of Heptanchus (Text-figure 29) are adapted for cutting as well as holding, and are not alike in upper and lower jaws. The decided differences between the teeth of Chlaynydoselachus and Heptanchus—forms which are in many important respects closely related—serve to weaken our faith in the validity of phylogenetic deductions based on a comparison of present-day fishes with fossil forms that are known only by their teeth. Generally speaking, in living fishes family differences in the teeth are great, gen- eric differences are considerable, while specific differences are slight. But it should also be borne in mind that the form of teeth is mainly an adaptive character, very subject to parallelisms. FOSSIL CHLAMYDOSELACHIDS Interestingly enough, while the controversy above epitomised was raging, all the contestants were unaware that as early as 1876 the fossil teeth of a true Chlamydoselachus had been described. In fact this was not known until Davis called attention to it in 1887, when the controversy had died down. Furthermore, since our work on this article began, the fossil tooth of an- other species of this genus has been found. Both of these finds will now be described. CHLAMYDOSELAC
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