Icaphoca choristodon n. gen., n. sp., described in the present study, represents the sixth monachine seal from the Neogene Pisco Formation of Peru. The species is solely known from the holotype, including a cranium with both mandibles, as well as five cervical vertebrae including the atlas and axis. This holotype was collected at the Cerro La Bruja locality, the type locality of Magophoca brevirostris, in the Ica Desert after which Icaphoca has been named. Stratigraphically, the holotype was recovered from strata underlying those of the Cerro La Bruja level (CLB level), from which Magophoca was recovered. These beds likely correspond with the P1-2 unit of the P1 sequence within the Pisco Formation. Assumed to be as old as 9 Ma (middle Tortonian), Icaphoca may be the oldest described monachine seal from the southeast Pacific. Following Magophoca and Noriphoca, Icaphoca is the third extinct monachine seal known to have six upper incisors. This plesiomorphic character is absent in all other extant and extinct Monachinae which have only four upper incisors. The elongation of the snout, as well as the presence of profound diastemas between the postcanine teeth, suggests that Icaphoca is closely related to Acrophoca from the upper Tortonian and Messinian of the Pisco Formation in the Sacaco area (Arequipa Department), c. 200 km southeast to Cerro La Bruja. The specific name choristodon refers to this spacing between the post-canine teeth. The close phylogenetic relationship between Icaphoca and Acrophoca is confirmed by the phylogenetic analysis, which retrieves both genera as sister taxa.
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RBINS Staff Publications 2025
