 The connection between these slender deciduous forms and the typically ascoceroid "Probillingsites" from the early Upper Ordovician can be made through the slightly inflated "Redpathoceras".A phylogenetic sequence can be seen in the Ascoceratidae, from "Probillingsites" through "Schucertoceras", then "Billingsites", in the Upper Ordovician, and finally to the middle and upper Silurian "Ascoceras".Changes involve the arrangement and complexity of septa in the mature conch and in its shape, ending with the more elongate and compressed mature "Ascoceras".