FIGURE 1. Map of the study area. A, the studied locality in the state of Baja California Sur in Mexico, zooming in on the area of the municipality of Comondú, where we can find the town of San Isidro. B, El Pilón plateau, located in La Purísima-San Isidro, where we can see the La Purísima stream and on the ground the strata where Cochimicetus convexus was collected. C, the photo shows C. convexus in ventral view and Cielo, who prepared the type specimen. D, map with close-up of the La Purísima-San Isidro region, the skull represents where C. convexus was collected in the fossiliferous sediments near the La Purísima stream. E, stratigraphy taken and modified from McLean et al. (1987), is observed on the upper horizon where C. convexus was collected. Illustration of Eomysticetidae modified and taken by Carl Buell.

FIGURE 2. Dorsal view of the holotype of Cochimicetus convexus. A, image showing the identified structures. B, photography with scale 10 cm.

FIGURE 3. Ventral view of the holotype of Cochimicetus convexus. A, image showing the identified structures. B, photography with scale 10 cm.

FIGURE 4. The cranial region and its structures in detail in dorsal view. A, each structure identified in this region is indicated. B, photography of Cochimicetus convexus, scale 5 cm.

FIGURE 5. Close-up of the ear area in ventral view. A, photography of Cochimicetus convexus. B, image showing the undefined structures with a scale 5 cm.

FIGURE 6. Close-up of the cranial case in ventral view. A, photography of Cochimicetus convexus. B, image showing the undefined structures with a 10 cm scale.

FIGURE 7. Left tympanic bulla in dorsal (A), ventral (B), medial (C), lateral (D), anterior (E), and posterior (F) view, with a scale of 1 cm.

FIGURE 8. Phylogenetic analysis showing the recovery of Cochimicetus convexus to Eomysticetidae. Blue shows the northern hemisphere Eomysticetids assemblage and purple shows the southern hemisphere assemblage. Show the equal weights, show the consensus tree with Cl: 0.262; RI: 0.0.748; 1,410 total lengths.