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Redalyc.Oligocene Cetaceans from Baja California Sur, Mexico Boletín de la Sociedad Geológica Mexicana ISSN: 1405-3322 [email protected] Sociedad Geológica Mexicana, A.C. México Hernández Cisneros, Atzcalli Ehécatl; González Barba, Gerardo; Fordyce, Robert Ewan Oligocene cetaceans from Baja California Sur, Mexico Boletín de la Sociedad Geológica Mexicana, vol. 69, núm. 1, -, 2017, pp. 149-173 Sociedad Geológica Mexicana, A.C. Distrito Federal, México Available in: http://www.redalyc.org/articulo.oa?id=94350664007 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Boletín de la Sociedad Geológica Mexicana / 2017 / 149 Oligocene cetaceans from Baja California Sur, Mexico Atzcalli Ehécatl Hernández Cisneros, Gerardo González Barba, Robert Ewan Fordyce ABSTRACT Atzcalli Ehecatl Hernández Cisneros ABSTRACT RESUMEN [email protected] Museo de Historia Natural de la Universidad Autónoma de Baja California Sur, Univer- Baja California Sur has an import- Baja California Sur tiene un importante re- sidad Autónoma de Baja California Sur, ant Cenozoic marine fossil record gistro de fósiles marinos del Cenozoico que Carretera al Sur Km 5.5, Apartado Postal which includes diverse but poorly incluye los restos poco conocidos de cetáceos 19-B, C.P. 23080, La Paz, Baja California Sur, México. known Oligocene cetaceans from del Oligoceno de México. En este estudio Instituto Politécnico Nacional, Centro Inter- Mexico. Here we review the cetacean ofrecemos más detalles sobre estos fósiles de disciplinario de Ciencias Marinas (CICMAR), fossil record including new observa- cetáceos, incluyendo nuevas observaciones Av. Instituto Politécnico Nacional s/n, Col. tions from materials that elucidate sobre materiales que proponen esclarecer Playa Palo de Santa Rita, Apartado Postal 592, 23096, La Paz, Baja California Sur, the evolution of the Neoceti in the aspectos de la evolución del grupo Neoceti Mexico. Pacific basin. Fossils were collected dentro de la cuenca del Pacífico. Los fósiles from outcrops of the El Cien For- han sido colectados de los afloramientos de Gerardo González Barba mation (Oligocene-Early Miocene) la Formación El Cien (Oligoceno-Mioceno Museo de Historia Natural de la Universidad Autónoma de Baja California Sur, Univer- and from San Gregorio Formation Temprano) y la Formación San Gregorio sidad Autónoma de Baja California Sur, (Late Oligocene). The specimens be- (Oligoceno Tardío). Los especímenes perte- Carretera al Sur Km 5.5, Apartado Postal long to the paleontological collection necen a la colección paleontológica del Museo 19-B, C.P. 23080, La Paz, Baja California Sur, of Museo de Historia Natural de la de Historia Natural de la Universidad Au- México. Universidad Autónoma de Baja Cali- tónoma de Baja California Sur. Se estiman Robert Ewan Fordyce fornia Sur. An estimated 26 unnamed alrededor de 26 especies sin nominar que in- Department of Geology, University of Otago, species include toothed cetaceans: cluyen cetáceos dentados: posibles “arqueoce- PO Box 56, Dunedin 9054, New Zealand. possible “archaeocetes” (?Kekeno- tos” (?Kekenodontidae), odontocetos arcaicos dontidae); archaic Odontoceti; and (Odontoceti), y el grupo basal de ballenas the basal group Aetiocetidae, toothed dentadas Aetiocetidae (Mysticeti). Los mis- mysticetes (Mysticeti). Toothless mys- ticetos barbados (Chaeomysticeti) incluyen ticetes (Chaeomysticeti) include the al grupo basal Eomysticetidae y formas basal group Eomysticetidae, and ba- similares a balenopteridos. Los cetáceos del laenopterids-like forms. The Oligo- Oligoceno de Baja California Sur, México cene cetaceans from Baja California son taxonómicamente diversos y representan Sur, Mexico are diverse and represent como tal el registro más austral conocido de the most southern such assemblages Norteamérica. known from North America. Palabras clave: Mysticeti, Odon- Keywords: Mysticeti, Odontoceti, toceti, México, fósiles, Oligoceno Mexico, fossils, Late Oligocene Tardío BOL. SOC. GEOL. MEX. 2017 VOL. 69 NO. 1 P. 149 ‒ 173 Manuscript received: February 1, 2016. Corrected manuscript received: August 4, 2016. Manuscript accepted: August 15, 2016. Oligocene cetaceans from Baja California Sur, Mexico 150 / Boletín de la Sociedad Geológica Mexicana / 2017 Juan de la Costa, El Cien and San Hilario), based 1. Introduction on field observations and uncatalogued specimens from the collections of the Museo de Historia Na- Fossil marine mammals, especially whales and tural de la Universidad Autónoma de Baja Cal- INTRODUCTION dolphins (Cetacea), have been reported widely ifornia Sur (MHN-UABCS) and material from from around the Pacific margin. Many species the Museo Regional de Antropología e Historia have been named from localities in western North de Baja California Sur (Barnes, 1998). Other un- America from Alaska to California, Peru, New published specimens from the San Juan Member Zealand, eastern Australia, and Japan. In Mexico include a skull of a putative agorophiid odonto- Oligocene marine mammals from Baja California cete (Cruz-Marín, 1997) and a skull of an archaic Sur have been reported since the 1940s, and most toothed mysticete (Olivares-Bañuelos, 2001). of the identified Oligocene fossils are cetacean, but The Oligocene cetacean fossil record from Baja desmostylids are known and some fragmentary California Sur is restricted to the San Gregorio bones could belong to sirenians and pinnipeds. Formation and El Cien Formation (Figure 1). These occurrences are important in providing Most of the specimens are from the San Juan insights into the poorly understood marine mam- Member (El Cien Formation), from localities near mals of Oligocene age from warm temperate to the village of San Juan de la Costa. However, it is subtropical settings. known that the distribution of fossils is broader, Amongst the early records, Vanderhoof (1942) and with abundant material in places like El Aguajito, Durham (1950) reported remains of the desmo- El Cien, Cerro Colorado, Tembabichi (Tembabi- stylian Cornwallius sookensis (Cornwall, 1922), and chi Member, El Cien Formation) and La Purísima other fossil bones from Punta San Telmo (Tem- (San Gregorio Formation). babichi Member, locality “miembro Punta San Since the 2000s more cetacean fossils have been Carlos” in Bahía San Carlos). Other marine mam- collected from the Oligocene outcrops in Baja Cal- mal fossils were reported in the 1970s, from Punta ifornia Sur, leading to recent published mentions San Telmo, San Hilario, El Cien, and San Juan de and some provisional identification (González-Bar- la Costa (Applegate and Wilson, 1976). One skull ba, 2007; Hernández-Cisneros and González-Bar- of a baleen whale from the El Cien locality was ba, 2013). In summary, the fossil record is diverse considered similar to the Oligocene-Miocene mys- at species to family level, but identifications are ticete Mauicetus parki (Benham, 1937) from New provisional because most of the specimens need Zealand (Downs and Morris, 1974). detailed preparation, and the specimens are large- Reports from the 1980s include fragments of ly unpublished. Nevertheless, the Oligocene ce- odontocete mandibles from the Aguajito area and taceans from Baja California Sur are potentially squalodontid teeth are known from the phosphat- important to understand the initial evolutionary ic sandstones at the locality “Diez minutos” (near radiation of the Neoceti - the two extant clades El Cien village). Mysticete skulls are known from of Mysticeti (filter-feeding baleen whales) and localities north of La Fortuna and in the vicini- Odontoceti (echolocating dolphins and toothed ty of Tembabichi (Applegate, 1986). The where- whales). The aim here is to review Oligocene ce- abouts of specimens collected or reported during tacean assemblages from Baja California Sur, and the 1940s to early 1990s are unknown but some add details of specimens that have previously been may be in the Universidad Autónoma de México mentioned only in unpublished theses or abstracts. (UNAM) collections (see Barnes, 1998). The geographic distribution and stratigraphy of Around 16 species of cetaceans were report- the main source horizons are summarized. Fos- ed during the 1990s from outcrops of San Juan sils of Oligocene cetaceans recently cataloged in Member, El Cien Formation (in the village of San MHN-UABCS collections improve knowledge of Oligocene cetaceans from Baja California Sur, Mexico Boletín de la Sociedad Geológica Mexicana / 2017 / 151 Oligocene cetacean diversity in Baja California ed around La Purísima ~250 km north of La Paz Sur (Hernández-Cisneros, 2012). near the Pacific coast (Fischer et al., 1995); the Tembabichi Member, El Cien Formation, on the coast of the Gulf of California, approximately 50 2. Study area and geological setting km north of the Bahía de La Paz (Fischer et al., INTRODUCTION / STUDY AREA AND GEOLOGICAL SETTING 1995; Plata-Hernández, 2002); and the San Juan Fossiliferous Oligocene rocks in Baja California Member, El Cien Formation, which lies between Sur include: the San Gregorio Formation, locat- the bay in the East and the State Road 1 in the Figure 1 Geologic map of Oligocene outcrops in Baja California Sur, and some representative specimens collected from the localities. San Gregorio Formation (A), Tembabichi Member of the El Cien Formation, (B), and San Juan Member of the El Cien Formation (C), Geological
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