Memoir 19—Part I: The first great expansion of the Actinoceroids; Part II: Some additional Whiterock cephalopods

By R. H. Flower, 1968, 120 pp., 6 figs., 30 plates, 1 index.

Part I describes cephalopods from the family Wutinoceratidae, collected in Nevada, Utah, and Newfoundland. Part II illustrates and describes 15 genera and 27 species from the Whiterock stage, mainly of specimens from Nevada and Utah.

The family Wutinoceratidae is developed in the Whiterock stage of North America, and members of the family in other regions may indicate Whiterock equivalence of the containing beds. The Wutinoceratidae are discussed; new material, largely from the Whiterock of Nevada and Utah and from the Table Head of Newfoundland, yielded the several new species here described. Notes on occurrence and stratigraphy are included as well as a discussion of the evolution of the Actinoceratida in the Ordovician and some remarks upon the classification of the group. The thesis that the actinoceroids should be elevated in rank equivalent to the Nautiloidea from which they were removed is rejected. Fine structures of septa and the connecting ring are described for Adamsoceras cf. isabelae.

Polydesmia, regarded as the oldest and most primitive of the actinoceroids, is known only from occurrences of eastern Asia in beds of either latest Canadian or earliest Ordovician age (Koybayashi, 1940). The next stage in the development of the actinoceroids is marked by the family Wutinoceratidae, which spread widely, being now known in eastern Asia, Tasmania, the Baltic region of Europe, and in the Whiterock stage of Cooper in North America. New material, here described, has augmented the forms known from the Whiterock of Nevada and western Utah. Oddly, these forms seem confined to beds which are rather high in the Whiterock there, the Palliseria zone of Nevada, and zone N (Hintze, 1952, 1953) of western Utah. There is one species, not very well known morphologically in the Oil Creek Limestone of Oklahoma, and new material has added to the species known from the Table Head Limestone of Newfoundland, where they range from beds 2 through 8 in the Lower Table Head Formation (Whittington and Finale, 1963). These are the only three regions in North America in which preserved limy sediments of Whiterock age are known. Intercontinental correlations are always hazardous, but the occurrence of the Wutinoceratidae in other parts of the world may well indicate that the beds containing them are equivalent to the Whiterock of North America.

The new material has supplied a basis for a review of some recently published ideas, in particular, the rejection of the Wutinoceratidae and two of its genera by Teichert (in Teirchert et. al., 1964). The author would like to reassert the validity of the family, defined primarily on the radial canal system; the close relationships of its three genera, which show some intergradation from the new material; and the desirability of recognizing this group as a taxonomic entity as well as one significant temporally.     Here are described and illustrated nautiloids from the Whiterock stage, mainly of Nevada and Utah comprising 15 genera and 27 species. The Whiterock cephalopods are summarized, drawing upon some material not yet described. They tend to support equivalence of the Utah-Nevada region, the Joins and Oil Creek of Oklahoma, and the lower Table Head of Newfoundland as a pre-Marmor interval. Cephalopod evidence is so far wanting for the higher beds of the Antelope Valley Limestone of Nevada.

The preceding paper, Part 1, contains descriptions of the available actinoceroids of the Whiterock stage of North America. This accompanying paper (Part 2) contains descriptions of some additional cephalopods from this same interval, belonging to other orders of the Nautiloidea. It must be emphasized that the forms described here are far from representing the complete fauna. A large amount of material was collected in the last two years, which will add materially to the knowledge of some species which have been long in manuscript, and will add new forms. Some knowledge of this undescribed material is involved in the general discussion of the faunas.