Abstract

Based on 137 specimens examined, the new species Commutia exoleta is characterized by a small, slightly scolecoid shape with 21 septa at a mean maximum corallite diameter of 6 mm (range 3 to 10.5 mm); a persistent inner wall, which encloses an aulos with a mean maximum diameter of 1.2 mm, formed during an early ontogenetic stage when the axial ends of the cardinal, alar and counter-lateral septa fused; short counter septa are lacking in the earliest stage of development.

Corallites are highly variable. Characters exhibiting a wide range of variation are: size and shape of corallites, number of septa, diameter of aulos and the timing of its appearance, number of septa connected to the inner wall, and the septal arrangement in each growth quadrant. Combinations of these variable characters result in corallites that are each uniquely different. Variations of those characters are partly due to stressed environments, such as unstable, muddy substrates resulting in corallite rejuvenescence and redirection.

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