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Abstract
A partial dentition of Polyrhizodus is described from the Namurian A Bear Gulch Limestone Member, Heath Formation, Big Snowy Group of central Montana. The dentition is interpreted as containing five tooth families in each jaw ramus, with at least three teeth in each family. The dentition is homodont, with teeth decreasing in length as well as numbers of roots in proximal‐distal progression. The teeth conform to those of Polyrhizodus digitatus Leidy, 1857, as well as several other nominal species.
The teeth consist of a thin, double‐layered enameloid interdigitating with the underlying osteodentine. Peripheral vascular canals radiate towards the outer surfaces of tooth apexes. Orthodentine is absent. The teeth of Petalodus ohioensis are more derived in that the enameloid is greatly thickened apically and principal vascular canals are limited to vertical rows normal to the cutting edge of the apex.