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Title: Systematics of the macrourid fishes
Author: Wood, Stephen William
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1996
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The systematics of rattail fishes (Teleostei: Gadiformes, Macrouridae) is reexamined focussing on the Coryphaenoides group of genera, including Albatrossia, Lionurus, Chalinura and Nematonurus. The data matrix consists of 69 osteological characters based on personal observations, 17 characters, generally of the soft anatomy, from various published sources and 34 characters reported from peptide mapping of muscle-type lactate dehydrogenase. An evolutionary systematics of morphology requires, firstly, a historical concept of homology and secondly, a scientific basis for the recognition of patterns. Viewing the organism as a hierarchy of constraint, homology is a relationship of development constraint inherited by parts of organisms. Taxa are types, relationships of constraint inherited by organisms. If, from the morphological perspective, taxa are relationships not groups, conventional concepts of monophyly and related terms cannot apply to them. In practice they describe comparisons between trees. The creation/discovery of patterns is embedded in the practice of systematics and has its basis in the intelligent abilities of human beings. Morphology deals with the linguistic aspect of evolution, rather than with its dynamic genetic aspect. Dynamic and linguistic aspects are complementary yet incompatible. The scientific status of morphology is shown to rest on this principle of complementarity. Through cladistic analysis of a large number of published characters, I investigate the scenarios and relationships of gadiform fishes that have recently been proposed. The results of the rattail analysis are thus placed within the broader context of gadiform ecology and evolution. In cladistics, parsimony plays the role of Popper's-empirical concept of simplicity, as a method of estimating the hypothesis of highest empirical support. Assumptions are made about the likely pathways of evolution in the way the characters are coded. Original classifications of the Gadiformes and the Macrouridae are proposed. Within the gadiforms there is a general trend from jaw precision to jaw protrusion. An index of protrusion/precision shows a negative correlation with depth. Rattails show low values of the index indicating high jaw protrusion. However, within the family the trend is towards higher jaw precision, and the precision/protrusion index is positively correlated with maximum depth. The discovery of cartilage in the exoskeleton of rattail fishes was an unforeseen result of the method of preparation. In rattails alcian blue reveals hyaline cell cartilage at the margins of certain dermal elements where it is gradually replaced by bone.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: rattail fishes ; Coryphaenoides