CANADOCERAS YOKOYAMAI: HASLAM FORMATION

A lovely chunky slate grey handful of an ammonite is Canadoceras yokoyamai from Upper Cretaceous (Early Campanian) outcrops in the Haslam Formation of Vancouver Island, British Columbia, Canada. 

This gorgeous ammonite was found by Tim O'Bear and is now in the collections of the Vancouver Island Palaeontological Society (VIPS), a regional paleontological society based in Courtenay.

This meaty cephalopod swam and hunted in our ancient oceans 80-84 million years ago and was once a leading candidate as the provincial fossil of British Columbia — an honour won by Shonisaurus sikanniensis.

The species is named for Matajirō Yokoyama, Professor of Geology and Palaeontology at the Imperial University of Tokyo, Japan. 

Yokoyama was born in the Nagasaki Prefecture on the 14th of June 1860 — the day slavery was abolished in the Neth Indies and the year Abraham Lincoln was elected president of the United States — a move that would lead to the beginning of the US Civil War the following year.

During his early life, the Meiji Restoration would begin the process of transforming Japan into a global imperial power. During the Restoration, Japan rapidly industrialized, adopting Western ideas and production methods. This shift in the cultural focus of his nation allowed him to pursue his studies in science — something encouraged in an emerging nation.

Matajirō Yokoyama (1860-1942)

Yokoyama did some wonderful work on the Cretaceous of Japan and opened up our understanding of the species on Vancouver Island. 

Through his research, we learned of the Japanese fauna and the extent of their occurrence. The range of Canadoceras yokoyamai extended from Alaska, the eastern coast of Vancouver Island, California to Santonian outcrops in the Yezo Group of Hokkaido in Japan’s northern islands. 

Within the Yezo Group, we find Canadoceras yokoyami amongst other ammonites, bivalves — and some wonderful marine reptiles — both mosasaurs and marine turtles.

Given that Canadoceras yokoyami arose, lived and died in a relatively short time frame — geologically speaking — they make excellent Index fossils. They can act as guides as to the age of the rocks in which they are preserved. This is helpful in the field. 

If you were to find a fossil in a rock of unknown age, you can look at the species and guess with relative certainty what age that rock likely is. 

References:

Matsumoto, T., 1954a [for 1953]: The Cretaceous system in the Japanese islands., pp. i–xiv + 1–324, pls. 1–20. The Japanese Society for the Promotion of Scientific Research, Ueno, Tokyo. (Reference No. 0219)

Tanabe, K., Ito, Y., Moriya, K. and Sasaki, T., 2000: Database of Cretaceous ammonite specimens registered in the Department of Historical Geology and Paleontology of the University Museum, University of Tokyo. The University Museum, The University of Tokyo, Material Reports, no. 37, pp. i–iv + 1–509. (Reference No. 0879)

Photo: Matajirō Yokoyama, Professor of Geology, Palaeontology and Mineralogy. 日本語: 横山又次郎 地質学古生物学及鉱物学教授 Tokyo Teikoku Daigaku (Imperial University of Tokyo). Ogawa Shashin Seihanjo, 1900 (reprint, Ryūkei Shosha, 2004).