A new aetiocetid (Cetacea, Mysticeti, Aetiocetidae) from the late Oligocene of Mexico

Echericetus novellus n. gen. n. sp. (Cetacea, Mysticeti, Eomysticetidae), an Oligocene baleen whale from Baja California Sur, Mexico

“…The discovery of Echericetus novellus n. gen. n. sp. from the Oligocene of Mexico (slightly older than 27.95 Ma, latest Rupelian) adds to the growing list of new eomysticetids in the North Pacific (e.g., Hernández-Cisneros and Nava-Sánchez, 2022). The eomysticetid fossil record represents one of the bestsampled stem mysticete clades, but large-scale questions remain, such as the origin, adaptive traits, and functional morphology (whether eomysticetids were skim feeders, similar to right baleen whales), and the causes that drove their extinction after the Oligocene-Miocene transition (Boessenecker andFordyce, 2015b, 2017b).…”

“…; but also see Boessenecker and Fordyce, 2017a for a review of Eomysticetidae), suggest that eomysticetids represent an ecologically competitive and successful lineage. The wide distribution in the Pacific, Atlantic, and likely Mediterranean-Paratethys oceans indicates that eomysticetids likely responded to environmental pressures and relocated with food sources efficiently (Boessenecker and Fordyce, 2017b;Marx et al, 2019;Hernández-Cisneros and Nava-Sánchez, 2022), but the sudden disappearance of eomysticetids remains uncertain and likely opens up the ecological niches for the success of the "modern" mysticetes.…”

“…In contrast to the toothed mysticetes (e.g., aetiocetids), these questions are crucial to understanding the bloom and evolution of baleen whales because eomysticetids likely represent the first fully baleen-assisted lineage (with nonfunctional teeth; Boessenecker and Fordyce, 2015a). Eomysticetids were probably driven by food sources (e.g., zooplankton; Clementz et al, 2014;Marx et al, 2019;Hernández-Cisneros and Nava-Sánchez, 2022) that seem related to phosphogenetic episodes during the Oligocene (Bisconti et al, 2023). Still, the relationship between the physical conditions and marine ecological systems that have facilitated eomysticetid diversification remains uncertain.…”

“…The phylogenetic analysis was performed on the basis of the original data matrix from Marx and Fordyce (2015), including recent updates from Hernández-Cisneros and Nava-Sánchez (2022) and Hernández-Cisneros (2022). We reviewed coded characters for Maiabalaena and Sitsqwayk , considering the observations from Boessenecker et al (2023) that suggest their inclusion in Eomysticetidae.…”

Aquatic mammal fossils in Latin America – a review of records, advances and challenges in research in the last 30 years

“…The cetacean fossil record in Mexico includes aetiocetids (e.g., Aetiocetus palmadentis) (Fig. 2), eomysticetids (e.g., Eomysticetus), stem mysticetes (e.g., Tlaxcallicetus), early odontocetes (simocetids) and archaeocetes such as kekenodontids (Hernández-Cisneros & Tsai, 2016;Hernández-Cisneros et al, 2017;Hernández-Cisneros, 2018;Solis-Añorve et al, 2019;Hernández-Cisneros & Nava-Sánchez, 2022). Such a record will likely increase our knowledge of the evolutionary and adaptive radiation of stem Neoceti during the Oligocene.…”