Bloom Taxa and Analogous Morphological Diversification after the K-Pg Boundary

Despite distinct evolutionary origins, the gastropod Araeodactylus and Perissoptera lineages show striking morphological parallels, suggesting convergence in ecological roles and locomotion strategies after the K-Pg boundary.

Araeodactylus, known from Paleogene strata, likely originated in the Late Cretaceous and is linked to “Chenopus buchii” Münster, 1839 sensu lato, with a possible Jurassic ancestor in Bicorempterus Gründel, 2001. Key morphological features include a teleoconch with spiral lines, a single apertural digit, and a straight to slightly bent rostrum.

On the other hand, Perissoptera likely descends from the Jurassic Pietteia Cossmann, 1904, both characterized by axial teleoconch ornamentation and a similar single apertural digit, which evolved in Perissoptera into a wing-like structure by the Maastrichtian.

Post-K-Pg, both lineages developed broad wing-like extensions. These may have functioned as protective feeding chambers, as in Xenophoridae, or supported locomotion—hydrodynamic gliding or swimming—as proposed by Savazzi, 1991, aligning with the diverse movement strategies seen generally in Stromboidea. While the Araeodactylus group and the broad-winged members of the Perissoptera group fully vanished in the Paleogene, various genera of the Perissoptera group survived and are now known as the family Rostellariidae.

Conclusion:
Despite originating separately, Araeodactylus and Perissoptera lineages demonstrate strikingly parallel evolutionary stories shaped by mass extinction at the K-Pg boundary, adaptive radiation, and eventual climate-induced collapse in the Oligocene.

Reference:

Savazzi, E. (1991). Constructional morphology of strombid gastropods. Lethaia 24(3): 311-331.