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Memoir 7

By R. H. Flower, 1961.

Text Section

229 pp., 10 figs.

Part 1: Montoya and related colonial, corals
Part 2: Organisms attached to Montoya corals

Plate Section

124 pp., 52 plates.

Part 1: Montoya and related colonial, corals
Part 2: Organisms attached to Montoya corals

Twenty-seven species are described from the Montoya Group of New Mexico; 17 from the Second Value Formation; 6 from the Aleman, and 5 from the Cutter; 1 species being common to the Aleman and the Cutter. Only four species have been described previously; the others are new. Four species are not determined specifically. One Aleman species is tentatively identified in the Cutter; others are distinct for the three formations. Two new genera, Crenulites and Trabeculites, are described. Species from other regions described and discussed, and in some cases revised, include five species of Favistina, Protrochiscolithus magnus, and Saffordophyllum crenulatum, three of Crenulites, one of Trabeculites, and two assigned to Foerstephyllum.

Regional analysis strengthens the Red River affinities of the Second Value Formation and the Richmond equivalence of the Aleman and Cutter Formations, but fuller evaluation must await more precise study of corals of other Ordovician faunas, particularly in western and northern North America.

Revised concepts of morphology and relationship are required, notably the derivation of septa as secondary structures from a primitive wall, and the primitive nature of a simple fibrous wall from which are derived trabecular walls on the one hand, and walls with an axial plate on the other, the axial plate developing both into the primary wall of the higher Favositidae, and into the epitheca of the rugosan types. The present study fails completely to support division of these corals into Tabulata and Rugosa, but it is felt that alternate proposals would be premature. A new structure, poikiloplasm, is described, which may line carallites, be concentrated as spherical knobs, with or without a thin connection, or form groups of discrete spheres. A summary is appended, briefly summarizing characters by which the Montoya species can be differentiated readily.

This is a study of the colonial corals of the Montoya Group. When the Montoya was considered as a formation, the early indications of the presence of a succession of distinct faunas were largely ignored. With recognition in the Montoya Group of several formations, and with reason to believe that a considerable interval of erosion separated the Second Value deposits from overlying Richmond beds, the need to take the stratigraphic range of various fossil groups into account becomes apparent at once. The material on which this study is based is, except for two specimens, of precisely known stratigraphic origin. The primary purpose of this study is the description of some 19 different sorts of organic calcareous remains found attached to colonial corals of the Montoya Group, mainly on colonies of Catenipora. These forms comprise 18 genera and species, all new. They are roughly divisible into (1) solid objects or calcareous capsules with central spaces, (2) coiled tests or shells, (3) straight tubes, and (4) a bivalved shell. The last is quite apparently an orbiculoid brachiopod, but the affinities of the others remain extremely doubtful, though in various cases the several possible interpretations are discussed. All forms are known only from their appearance in thinsections. Attention is also called to Lichenocrinus-like bodies in colonies of Coccoseris, and some cavities obviously occupied by foreign organisms in colonies of the same genus. The coral sections yielded a characteristic worm burrow in the matrix, which is briefly described but not named. The primary purpose of this study is the description and illustration of some small organic remains found attached to various of the corals described in Part I. These bodies, dominantly calcitic, are like nothing described before, and their affinities are highly uncertain. They were first observed in the examination of the thin sections prepared for the study of the corals, and indeed still remain known only from such sections. They are all small, few exceed 2 mm in their greater dimension, and most are 1 mm or less across. As the same sections and the same photographs that show these bodies also exhibit significant features of the corals to which they are attached, this and the preceding paper (Part I) are illustrated by a common series of plates, and illustrations of these bodies are primarily concentrated in Plates 9-12, following the illustrations of Catenipora, for most individuals were found on colonies of that genus. In order that the description of these remarkable bodies might not be obscured, as might be the case were they described as an appendix to the above coral study, several of the author's colleagues suggested that this study by kept distinct, with a separate title. For completeness, some observations are added on a Lichenocrinus-like body found in colonies of Coccoseris, and on some cavities, obviously of organic origin, noted in cerioid colonies of the same genus.

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