A new chaeomysticete from the Late Oligocene of Baja California Sur, Mexico: expanding the diversity of early baleen whales
Por:
Solis-Añorve A., Buono M.R., Díaz-Cruz J.A., Schwennicke T., Aguilar-Cruz C.A., Gonzalez-Barba G.
Publicada:
1 ene 2026
Resumen:
© The Trustees of the Natural History Museum, London 2026. All rights reserved.Chaeomysticeti includes the filter-feeding mysticetes, encompassing all extant baleen whales as well as early diverging mysticete fossils. Its origins date back to the early Oligocene Epoch, a period that marked a significant upswing for mysticetes. During this epoch, both toothed and toothless mysticetes were represented, alongside forms closely related to the crown group of mysticetes. In recent years, several taxa from the Oligocene of the El Cien Formation (Baja California Sur, Mexico) have been described, revealing a diversity of forms and adaptations that can be compared to those from other Oligocene localities in the Pacific and Atlantic. We describe the partially preserved skeleton of a new taxon of Chaeomysticeti, Calafiacetus longipinna, from the Late Oligocene of the El Cien Formation. This specimen includes the skull, tympanic bullae, vertebrae, and fragments of ribs and scapula, with both flippers notably preserving the carpal region. This taxon represents the earliest branching lineage of toothless whales, along with Maiabalaena nesbittae and Sitsqwayk cornishorum. Calafiacetus longipinna retained ancestral traits in forelimb morphology, including a prominent deltopectoral crest and proportionally similar radius and ulna, marking a transitional stage towards modern mysticete flipper adaptations. Its postcranial morphology indicates a wave-like locomotion pattern, consistent with other chaeomysticetes, facilitated by the elongation of the vertebral centra. This specimen provides key insights into the evolution of anatomical features in early diverging chaeomysticetes during the Oligocene in the North Pacific. https://zoobank.org/urn:lsid:zoobank.org:pub:89127B8E-E432-43C6-84A2-8505C22082C8.
Filiaciones:
Solis-Añorve A.:
Posgrado de Ciencias Marinas y Costeras (CIMACO), Universidad Autónoma de Baja California Sur,., Carretera al sur Km 5.5, apartado postal 19-B CP: 23080, La Paz, Baja California Sur, México
Museo de Historia Natural, Universidad Autónoma de Baja California Sur,., Carretera al sur Km 5.5, apartado postal 19-B CP: 23080, La Paz, Baja California Sur, México
Buono M.R.:
Instituto Patagónico de Geología y Paleontología, CCT CONICET-CENPAT,., Bvd. Brown 2915, U9120ACD, Puerto Madryn, Chubut, Argentina
Díaz-Cruz J.A.:
Instituto de Geología, Universidad Nacional Autónoma de México,., Ciudad Universitaria. Coyoacán, Ciudad de México
Colección Nacional de Peces, Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, Tercer Circuito Exterior S/N., CP 045110, Mexico City. México
Facultad de Ciencias, Circuito Interior, Avenida Universidad 3000, Universidad Nacional Autónoma de México, Coyoacán, Mexico City, 04510, México
Schwennicke T.:
Departamento Académico de Ciencias de la Tierra, Universidad Autónoma de Baja California Sur,., Carretera al sur Km 5.5, apartado postal 19-B, CP: 23080, La Paz, Baja California Sur, México
Aguilar-Cruz C.A.:
Laboratorio de Biología de Invertebrados, Centro Interdisciplinario de Ciencias Marinas del Instituto Politécnico Nacional, Avenida Instituto Politécnico Nacional s/n, Colonia Playa Palo de Santa Rita, CP: 23096, La Paz, Baja California Sur, México
Gonzalez-Barba G.:
Museo de Historia Natural, Universidad Autónoma de Baja California Sur,., Carretera al sur Km 5.5, apartado postal 19-B CP: 23080, La Paz, Baja California Sur, México
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