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Showing results for tags 'north texas heteromorph'.
From the album: Fauna and Flora of the Austin Group in TexasThis Tridenticeras peramplum specimen is 2.9 cm in height, and 1.9 cm in diameter. It shows the typical three rows of tubercles on each oblique rib, except on the most mature, bottom whorl. What I can tell from my references is that this is because only the phragmocone has tubercles, and thus the bottom whorl is the living chamber.