HOW SMALL ARE CALIFORNIA MASTODONS, REALLY?

Several authors over the years have suggested that individuals of Mammut americanum from California tend to be smaller than those from the eastern United States, but little data have been presented to test this hypothesis. Measurements obtained from second and third molars (maximum crown length and width) and femora (length, distal width, and minimum diameter) from mastodons from various southern California localities, particularly Rancho La Brea and Diamond Valley Lake, enable comparison to published measurements of specimens from elsewhere in North America.

Preliminary results indicate that California mastodon molars tend to be smaller in both length and width than those from mastodons from Florida or Indiana. Moreover, California mastodon molars tend to be narrower for a given length than those from Florida and Indiana; for data collected through December 2012 the narrowest for each tooth position was a California specimen. This trend is most pronounced in m3, but is also present in M3, M2, and m2.

Although femoral data are still very limited, there are some indications that distal femoral width does not track closely to body size. Diamond Valley Lake specimen WSC 18743 has a distal femoral width of 270 mm, larger than either measured specimen from Rancho La Brea and nearly as large as the Watkins Glen, New York specimen, a large male individual. Yet the molars from WSC 18743 are not particularly long relative to other California specimens, and in fact are among the narrowest molars measured.