Boletín de la Sociedad Geológica Mexicana Volumen 76, núm. 1, A131223, 2024 http://dx.doi.org/10.18268/BSGM2024v76n1a131223

First record of an Eomysticetidae from the El Cien Formation (late Oligocene), “Ten Minute” locality, Baja California Sur, Mexico

Primer registro de Eomysticetidae de la Formación El Cien (Oligoceno tardío), localidad “Ten Minute”, Baja California Sur, México

Azucena Solís-Añorve^1,2,*, Gerardo González-Barba², Mónica R. Buono^3,4, Tobias Schwennicke⁵

Jesús Alberto Díaz-Cruz⁶

¹ 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.

² 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.

³ Instituto Patagónico de Geología y Paleontología, CCT CONICET-CENPAT. Bvd. Browm 2915, U9120ACD, Puerto Madryn, Provincia del Chubut-Argentina.

⁴ Museo Paleontológico “Egidio Feruglio”, Av. Fontana 140, Trelew, Chubut, Argentina.

⁵ 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.

⁶ Colección Nacional de Peces, Departamento de Zoología, Instituto de Biología, Universidad Autónoma de México, Tercer Circuito Exterior S/N. CP 045110, Mexico City. Mexico.

* Corresponding author: (A. Solís-Añorve) This email address is being protected from spambots. You need JavaScript enabled to view it.

How to cite this article:

Solís-Añorve, A., González-Barba, G., Buono, M.R., Schwennicke, T., Díaz-Cruz, J.A., 2024, First record of an Eomysticetidae from the El Cien Formation (late Oligocene), “Ten Minute” locality, Baja California Sur, Mexico, 76 (1), A131223. http://dx.doi.org/10.18268/BSGM2024v76n1a131223

Manuscript received: September 1, 2023; Corrected manuscript received: November 10, 2023; Manuscript accepted: December 13, 2023.

ABSTRACT

Eomysticetidae (Chaeomysticeti clade) is an archaic family of baleen whales that originated and diversified during the Oligocene epoch. The fossil record of this family is represented by at least 11 formally described species, including records in Baja California Sur (Mexico), Kaiserswerth (Germany), Kitakyushu (Japan), South Carolina (United States), and South Island (New Zealand). Baja California Sur (BCS) possesses important marine deposits from the upper Oligocene, which document a rich diversity of fossil mysticetes, including members of the family Eomysticetidae. In this work, we report a whale specimen collected in the upper Oligocene San Juan Member, El Cien Formation, from the so-called “Ten Minute locality”, San Hilario, about 100 km NW of La Paz, Baja California Sur. The studied specimen consists of an incomplete skull, in which most of the rostrum and part of the occipital shield are missing but preserving one tympanic bulla in situ. This specimen is identified as belonging to the family Eomysticetidae based on both an elongated skull and nasals and transversely narrow and long intertemporal region with a wide exposure of parietals and frontals. The lack of more diagnostic regions precludes its identification at generic/specific levels. The specimen represents the first description of an eomysticetid for the San Hilario area, increasing our knowledge of the evolution of this group of mysticetes and its record in the Pacific basin from the late Oligocene of BCS.

Keywords: Mysticeti, Oligocene, San Hilario, baleen whale, El Cien.