Studies on Brachiopoda from the Oolite Marl (Jurassic) of the Cotswolds.
thesisposted on 19.11.2015, 09:02 by P. G. Baker
The suggestion that a re-study of the Brachiopoda of the Oolite Marl was long overdue was made by the late Dr. Helen Muir-Wood because, although the extensive collections of Buckman, Richardson, Upton and Walker during the period 1895-1933 proved a diverse brachiopod fauna in the Oolite Marl, the deposit had subsequently received scant attention. Moore (1855, 1861) had described micromorphic species from the Inferior Oolite of Dundry but no parallel investigations were undertaken in the mid-Cotswolds. The apparent recent lack of interest seems strange as immature zeilleriids were certainly recognised by Richardson (1929) in Westington Hill Quarry and ontogenetic stages of zeilleriid genera have been sought for a number of years. In fact, bulk samples of the marl from this locality have yielded such a rich fauna of micromorphic and juvenile brachiopods that the current research has necessarily been restricted to micromorphs and to ontogenetic studies involving the juvenile zeilleriids. An obvious preliminary course of action was to attempt to correlate juveniles of a species with their respective adults. During these investigations it was noticed that the secondary shell mosaic of some specimens was often very well preserved. In the light of Williams' very important contribution to microstructure studies, first with the aid of the transmission electron microscope and subsequently with the aid of the scanning electron microscope, it was decided to obtain as much new microstructural data from the material as possible, in addition to ontogenetic, morphological and systematic studies. The species recognised have been studied separately and the sections are listed below together with the various aspects investigated. 1. Moorellina granulosa (Moore) A. Extraction. Brachial valve morphology. Ontogeny. P.4 B. Punctation. p.27 C. Growth. Microstructure. Palaeoecology. Affinities. p.36 2. Zellania davidsoni (Moore) p.76 Morphology. Microstructure. Palaeoecology. Affinity. 3. Nannirhynchia longirostra sp. nov. p.101 Systematics. Microstructure. Ontogeny. 4. Zeilleria leckenbyi (Davidson ex Walker Ms) p.112 Collection. Nomenclatural problems. Loop development. Loop function. Inter-relationships of Mesozoic long-looped Terebratulida. 5. Summary of Conclusions. p.149. (Abstract shortened by UMI.).