Scanning electron microscope analysis of enamel microstructure in a Polycotylid (Plesiosauria) from the Pierre Shale Group, South Dakota, U.S.A.

The teeth of polycotylid plesiosaurs are generally simple, cone shaped, non-serrated and only slightly recurved without distinct carinae. The surface of crowns are characterized by a series of vertical enamel wrinkles that are more highly developed on the lingual surface of the crown, and decrease in width and number toward the apex. Some of the most promising research related to fossil dentition, involves the analysis of surface and internal dental microstructure. This study, is an attempt to examine and describe polycotylid dental microstructure. It gives an overview of polycotylid plesiosaur enamel and dentine microstructures using a scanning electron microscope. Enamel type and structures vary, based on its position on the surface of the crown, and its perceived strength requirements. The dentition layer is “honeycombed” with tubular structure, possibly to provide nourishment to fast growing crowns. The study of crown microstructures may lead to a better understanding of polycotylid niche preference in the late Cretaceous oceans.

Scanning electron microscope analysis of enamel microstructure in a Polycotylid (Plesiosauria) from the Pierre Shale Group, South Dakota, U.S.A.

The teeth of polycotylid plesiosaurs are generally simple, cone shaped, non-serrated and only slightly recurved without distinct carinae. The surface of crowns are characterized by a series of vertical enamel wrinkles that are more highly developed on the lingual surface of the crown, and decrease in width and number toward the apex. Some of the most promising research related to fossil dentition, involves the analysis of surface and internal dental microstructure. This study, is an attempt to examine and describe polycotylid dental microstructure. It gives an overview of polycotylid plesiosaur enamel and dentine microstructures using a scanning electron microscope. Enamel type and structures vary, based on its position on the surface of the crown, and its perceived strength requirements. The dentition layer is “honeycombed” with tubular structure, possibly to provide nourishment to fast growing crowns. The study of crown microstructures may lead to a better understanding of polycotylid niche preference in the late Cretaceous oceans.

Simple-cone conodont taxa from the Cobbs Arm Limestone (Middle Ordovician), New World Island, Newfoundland

New and previously described conodont taxa are reported from the upper Chazyan (Llandeilian) Cobbs Arm Limestone of New World Island, north-central Newfoundland. In addition to Ansellidae n. fam., (the following new taxa are described: Ansella n. gen., with type species Belodella jemtlandica Löfgren, 1978, Goverdina alicula n. gen. n. sp., Serraculodus alveus n. gen. n. sp., and Walliserodus dolabellus n. sp. The conodont apparatus compositions of the following species are also described: Ansella nevadensis (Ethington and Schumacher), Scalpellodus cavus (Webers), Walliserodus ethingtoni (Fåhræs), and W. nakholmensis (Hamar).

2. On the Carboniferous Volcanic Rocks of the Basin of the Forth

After referring to a previous communication to the Society, in which the author had given an outline of the chronology of the igneous rocks of Scotland, he proceeded in the present paper to describe in detail the character of the volcanic phenomena in one district—that of the carboniferous system of the Forth basin. The igneous rocks of this district consist partly of doleritic and felspathic lava-form masses, and partly of various kinds of ash or traptuff. These materials present a considerable diversity in their modes of arrangement. But the author had found that all the volcanic hills of the district might be reduced to three types of structure:—1. A simple cone of ash, round and over which the ordinary sedimentary accumulation of the carboniferous period had been deposited. 2. A cone of ash with the crater filled up by a neck or plug of basalt. 3. Sheets of different lavas with intercalated ash or sedimentary matter.