Redalyc.Oligocene Cetaceans from Baja California Sur, Mexico

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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

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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 P. 149‒173 VOL. 69NO. 1 BOL. SOC.GEOL.MEX.2017 PO Box 56,Dunedin9054,NewZealand. Otago, Geology, University of of Department Robert EwanFordyce México. 19-B, C.P. 23080,LaPaz, Sur, BajaCalifornia PostalCarretera alSurKm5.5,Apartado sidad Autónoma Sur, deBajaCalifornia Autónoma Sur, deBajaCalifornia Univer Museo deHistoriaNatural delaUniversidad Gerardo GonzálezBarba Mexico. 592, 23096,LaPaz, Sur, BajaCalifornia Playa Palo Postal deSantaRita,Apartado Av. InstitutoPolitécnico Nacionals/n,Col. disciplinario deCienciasMarinas(CICMAR), Instituto Politécnico Nacional,Centro Inter México. 19-B, C.P. 23080,LaPaz, Sur, BajaCalifornia Carre sidad Autónoma Sur, deBajaCalifornia Autónoma Sur, deBajaCalifornia Univer Museo deHistoriaNatural delaUniversidad [email protected] CisnerosAtzcalli EhecatlHernández Atzcalli Ehécatl Oligocene cetaceansfromBajaCaliforniaSur,Mexico Manuscript August accepted: 15,2016. Corrected manuscript received: August 4,2016. Manuscript received: February 1,2016. tera al Sur Km 5.5, Apartado Postaltera alSurKm5.5,Apartado Hernández Cisneros Hernández - - Mexico, fossils, LateOligocene Keywords: Mysticeti,Odontoceti, known from NorthAmerica. such assemblages the most southern Sur, Mexico are diverse andrepresent cene cetaceansfrom Baja California Oligo The laenopterids-like forms. basal group Eomysticetidae, and ba ticetes (Chaeomysticeti) include the mysticetes (Mysticeti). Toothless mys the basalgroup Aetiocetidae, toothed dontidae); archaic Odontoceti; and possible “archaeocetes” (?Kekeno species includetoothed cetaceans: Sur.fornia estimated An 26 unnamed Universidad Autónoma de Baja Cali MuseodeHistoriaNatural de la of long to the paleontological collection (Late specimens be Oligocene). The and from SanGregorio Formation mation (Oligocene-Early Miocene) the El CienFor from outcropsof Pacific basin.Fossilswere collected theNeoceti in the the evolution of fromtions materials that elucidate fossilrecord includingnewobserva Mexico. Here we review the cetacean knownOligocene cetaceansfrom which includes diverse but poorly ant Cenozoic marine fossilrecord Sur has animport Baja California ABSTRACT , Gerardo Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín González Barba , Robert Ewan ------ofrecemos másdetalles sobreestos fósiles de del OligocenodeMéxico. Enesteestudio incluyelos restos poco conocidos de cetáceos gistro defósiles marinos del Cenozoico que Sur tiene unimportante re Baja California RESUMEN Tardío toceti, México, fósiles, Oligoceno Palabras clave: Mysticeti, Odon Norteamérica. más australcomo tal el registro conocido de son taxonómicamente diversos y representan Sur,Oligoceno de Baja California México similares a balenopteridos. Los cetáceos del y formas basal Eomysticetidae al grupo incluyenticetos barbados (Chaeomysticeti) dentadas Aetiocetidae (Mysticeti). Los mis basal de ballenas (Odontoceti), y elgrupo odontocetos arcaicostos” (?Kekenodontidae), cluyencetáceos dentados: posibles “arqueoce alrededor de 26especies sinnominar in que Sur.tónoma de Baja California Se estiman de Historia Natural de la Universidad Au necen a la colección paleontológica del Museo (Oligoceno Tardío). Los especímenes perte Temprano) yla Formación San Gregorio la Formación El Cien(Oligoceno-Mioceno han sido colectados delos afloramientos de dentro dela cuenca del Pacífico. Los fósiles Neoceti del grupo aspectos de la evolución sobremateriales que proponen esclarecer cetáceos, incluyendo observaciones nuevas Fordyce /2017 149 ------

Oligocene cetaceans from Baja California Sur, Mexico ABSTRACT Oligocene cetaceans from Baja California Sur, Mexico INTRODUCTION 150 150 1. Introduction from around the Pacific margin. Many species have been named from North localities in western Many margin. Pacific the around from dolphins (Cetacea), have been reported widely Fossilmarine mammals, especiallywhales and Member, San ElCien Formation (inthe village of San Juan ed during the 1990s from outcrops of cetaceans were report Around 16species of (UNAM) 1998). collections(seeBarnes, maythe Universidadbe in Autónoma deMéxico the 1940s to early 1990sare unknown but some specimenscollected or reported during abouts of where The 1986). Tembabichi(Applegate, of ty LaFortuna and inthe vicini localities north of El Cien village). areMysticete skulls knownfrom atic sandstones the locality “Diezminutos”(near squalodontid teeth are knownfrom the phosphat of fragments odontocete include mandibles fromthe Aguajitoarea and 1980s the from Reports Zealand (Downs andMorris, 1974). ticete considered similar to the Oligocene-Miocene mys abaleen whale from the El Cien locality was of and Wilson,la Costa (Applegate 1976). One skull San Telmo, San Hilario, ElCien,andSan Juan de mal fossilswere reported in the 1970s, from Punta Carlos”in Bahía San Carlos). Other marine mam babichi Member, locality “miembro Punta San other fossilbones from Punta San Telmo (Tem stylian the desmo Durham (1950) reported remains of Amongst the early records, (1942) and Vanderhoof subtropical settings. temperate to Oligocene age from warm mals of into thepoorlyinsights marine mam understood occurrences areThese important in providing bones couldbelong to sirenians andpinnipeds. aredesmostylids known andsomefragmentary the identifiedof Oligocene fossils are cetacean, but Sur have been reported the 1940s,since andmost Oligocene frommarine mammals Baja California Australia, and Japan.Zealand, eastern Mexico In America from Peru, Alaskato California, New / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Mauicetus parki Cornwallius sookensis Cornwallius Bna, 97 fo New from 1937) (Benham, (Cornwall, 1922), and (Cornwall, ------/2017 oto the specimens are from the San Juan Most of Formation and ElCienFormation (Figure 1). Sur is restricted to the San GregorioCalifornia Oligocene cetacean fossilThe record from Baja toothed mysticete (Olivares-Bañuelos, 2001). anarchaic cete (Cruz-Marín, 1997)andaskullof aputative agorophiid odonto of include askull published specimensfrom the San Juan Member un Other 1998). (Barnes, Sur California Baja de the Museo Regional deAntropología e Historia Sur (MHN-UABCS)ifornia and material from tural de la Universidad Autónoma de Baja Cal the Museo de Historia Na from the collections of observationsfield on uncatalogued and specimens Juan de la Costa, El Cien and San Hilario), based H-AC olcin mrv nweg fMHN-UABCS collections improve knowledge of Oligocene cetaceans recently cataloged in sils of the main source horizonsare summarized. Fos distribution geographic andstratigraphyThe of mentioned only inunpublished theses orabstracts. specimensthat have previouslybeen add details of tacean assemblages from Sur, Baja California and whales). aimhere The is to review Oligocene ce and whales) Odontoceti (echolocatingand toothed dolphins baleen (filter-feeding Mysticeti of the Neoceti - the two extant clades radiation of the initial evolutionaryimportant to understand taceans from Sur are potentially BajaCalifornia ly unpublished. Nevertheless, the Oligocene ce detailed preparation, andthe arespecimens large the specimens need provisional because most of are identifications but level, family to species at diverse is summary,record In fossil 2013). the ba, ba, 2007; Hernández-Cisneros and González-Bar and some provisional identification (González-Bar Sur,ifornia leading torecent published mentions collected from the Oligocene outcropsin Baja Cal Since the 2000s more cetacean fossilshave been (San Gregorio Formation). chi Member, El Cien Formation) and La Purísima El Cien, Cerro Colorado, Tembabichi (Tembabi with abundant material like ElAguajito,places in fossilsbroader,is knownthat thedistribution of San Juan de la Costa. However,the village of it is Member (El Cien Formation), from localities near ------San Gregorio Formation(A),TembabichiMember of theElCienFormation, (B),and SanJuanMember oftheElCienFormation(C), Figure 1 2. Studyareaandgeologicalsetting Geological distribution extractedfrom themapof theServicioGeológicoMexicano (Alexadri-Rionda Sur include: the San Gregorio Formation, locat FossiliferousOligocene rocks inBaja California Sur (Hernández-Cisneros, 2012). Oligocene cetacean diversity inBaja California Geologic map of OligoceneoutcropsinBajaCalifornia Geologic Sur,andspecimens collectedfrom somerepresentative thelocalities. Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín - the bay inthe Eastandthe State Road 1inthe Member, ElCienFormation, which liesbetween Juan San the and 2002); Plata-Hernández, 1995; the Bahía de La Paz (Fischer km north of approximately California, 50 of theGulf coast of Tembabichi Member, El Cien Formation, on the (Fischer coast Pacific the near LaPaz ed aroundnorth of LaPurísima~250 km et al ., 2008). et al /2017 ., 1995);the et al 151 151 .,

INTRODUCTION / STUDY AREA AND Oligocene cetaceans from Baja California Sur, Mexico GEOLOGICAL SETTING STUDY AREA AND GEOLOGICAL SETTING/ Oligocene cetaceans from Baja California Sur, Mexico METHODS AND MATERIALS 152 152 and SanJuan members. Oligocene outcropsare the Tembabichithe more extensive distribution of the largest arroyos(McLean of small outcrops along the banks andstream bottoms the San Gregorio Formation are localities of The (Figure 1). west (Fischer mollusks and crabs(Smith, mollusks 1991; Grimm and – macroinvertebrates 2008), (González-Barba, faunas ray and shark 1992), Schwennicke, 1987; (McLean nannofossils calcareous and 1987), (Kim, foraminifera planktonic 1986), Barron, and diatoms(Kim (Schwennicke, 1994).Past studiesof vironments, coastal lagoons, estuaries and deltas en shelf than 200 m,suggesting ted no deeper ElCienFormation were deposi sediments of al planktic foraminifers andtrace fossils(McLean water between depths 500 and2500mbasedon gorio Formationfrom as deposits interpreted is environment depositional The for the San Gre al (Fischer conglomerates and tuff, phosphorite, partly phosphatic silt- and sandstones, granular siliceous, diatomaceous orphosphatic mudstones, tuffaceous, partly laminated, of composed mainly San Juan 2002).The Plata-Hernandez, Member is andSchwennicke, (Plata-Hernandez deposit 2000; thesamebasin a lateralMember as variation of and it is considered correlative to the San Juan coquina, phosphatic horizons, anddolomitic beds siltstones, sandstones, mudstones, of ber consists tuffs (McLean phosphatic mudstone with fish scales, and rhyolitic phosphatic layers,siltstone, siliceous quences of and Föllmi, 1994),withseveral se alternating porcelanite, siltyporcelanite andchert (Grimm sediments –white diatomite, diatomaceous clay, biosiliceous laminated finely very to finely dark San GregorioThe Formation ischaracterized by 1984; Fischer atomite, coquinaandconglomerates (Hausback, include phosphatic sandstonebeds, mudstone, di vironments withrelatively similar stratigraphy that discontinuous and reflect differentdepositional en / ., 1987; Grimm and Föllmi, 1994). In contrast, In 1994). Föllmi, and Grimm 1987; ., ., 1995). Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín et al et al et al ,19)~0k ot fLaPaz north of ., 1995)~40km ., 1995). ., 1987). The Tembabichi Mem et al ., 1987), unlike et al e.g et et ., ------/2017 . 3. MethodsandMaterials eous nannofossils( Oligocene-Early Miocene) based onK/Ar, calcar 1996), andhasbeen dated as ~27 to 22 Ma(Late SanGregorio Formation(Ganz, ~75 m is tion of to 23 Ma. The thickness for the main exposed sec ~30 range sequences Oligocene the for age The productivity.primary subtropical environment characterized byhigh region during the Late Oligocene and indicate a the of history obiological and paleoceanographic studies (Grimm,1992)have elucidated the pale and Vázquez-García, 1996), and sedimentological li-Olivier,Schwennicke,1993; Schwennicke1994; 2013), phosphorites (Galli-Olivier Föllmi, 1994;Schweitzer dez-Cisneros(2012, 2014,2015),Fordyce Hernán from derived are 1) (Tableobservations New present. Gerar to 1991 by from Barba, recorded González do were and 1988, in began fossil material for MHN-UABCS collections of the San Gregorio and El Cien formations. Field of viewed the available literature, outcrops and fossils fossilsfrom MHN-UABCS collection. We re cetacean Oligocene of catalog and identification, studyThis involved field exploration, preparation, the NP24/NP25zones (Schwennicke, representing 1992). nannofossils calcareous and 1987) aminifera representing zones P21 and P22 (Kim, Jousé,1973, – diatom 1984), (Hausback, bed tuff biostratigraphy a from biotite for dates K/Ar on based Ma 23 to ~30 is age Its 1996). Vázquez-García, and nicke (Schwen locality Costa la de Juan San at m 130 Member varies from 75mat Aguajito locality to Juan San the of Thickness 2002). ta-Hernández, Pla 1984; (Hausback, beds tuff using Rb/Sr and K/Ar with dated Ma 25.9 to ~28 of age an with 1992), (Grimm, thick m ~135 is section type the Lean gelida Rocella vigilans (Bukry, 1978) (Kim and Barron, 1986; Mc 1986; Barron, and (Kim (Bukry,1978) et al , 97. o te ebbci Member, Tembabichi the For 1987). ., R. gelia enr 1982, Fenner, Discoaster (Kim and Barron, 1986), for 1986), Barron, and (Kim et al ) anddiatoms – ., 2002;Vera-Dimas, Bogorovia veniamini et al ., 1990;Gal Rocella et al ., ------, 4. Results sequence (Appendix Figure A1). Incontrast, the sequence (Appendix the within phosphatic sandstonenear the top of Gregorio Formation. Generally thefossilsoccur ElCien Formation andSan Oligocene outcropsof Cetacean fossilsare in Latesporadic to common Smithsonian Institution,Washington D.C. Natural History, ed in the National Museumof Dunedin, NewZealand; USNM, specimencurat Otago, Museum, University rated of in Geology Sur,Baja California Mexico; OU, specimencu sidad Autónoma Sur, deBaja California LaPaz, (MU), Museode Historia Natural de la Univer Institutional abbreviations. ZoologicalNomenclature. Code of the International parentheses asappropriate) of using the author-comma-date convention (with References forcite taxa the mostly original author, Hernández-Cisneros and (2013), ba González-Bar and Hernández-Cisneros (2012), viduals, which represent two majortaxonomic speciesandindi number of worthyof in terms Fossilcetaceans from Sur are note Baja California Figure A3). (Appendix ~20 m above the lower limit at Aguajito locality the San Juan Member,found closeto the base of mine work isactive. More cetacean bones canbe the zonesin mainly occur where thephosphorite section inSan Juan de la Costa complete skeletons the exposed stratigraphic to. In the middle part of El Saladi fossilsin somelocalities to the north of by aconglomerate with sporadicmarine mammal the San Juanber. Member is capped top of The fossildistribution similar to Tembabichi is Mem ments on the surface. In the San Juan Member, the fossilsareThe in concretions or are scattered frag Figure A2). column(Appendix the stratigraphic in m ~30–35 –above base the to close and beds), middle part (mostly allochthonousin phosphatic and appear in the section closeto the top, inthe sociated with siltstones and phosphatic sandstones, Tembabichi area has abundant fossilswhich are as MHN-UABCS et al ., (2014). Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín ------the squamosal (Deméré and Berta, 2008) – from – 2008) Berta, and (Deméré squamosal the andthe zygomatic the jugal processof overlap of to the bony naris(Fitzgerald, 2010) and a short premaxilla that overhangs the maxillaadjacent Aetiocetidae, the family a including synapomor phies of exhibit 2A) (Figure EcSj5/24/123 Some Mysticeti specimens, asMHN-UABCS_ research. of pared well naming atenough tojustify thisstage counts for species, but few are preserved or pre separated at species level, thus allowing minimum generally show enoughdistinctive features to be and Odontoceti) or crown-Cetacea. Specimens tacea, and the monophyletic Neoceti (Mysticeti groups: the paraphyletic Archaeoceti or stem-Ce gon, ≤30Ma (Snavely Ore USNM205491 from the Alsea Formation of Sur specimen isphylogeneticallylifornia close to Ca Baja latter The 5B). (Figure EcSj24/50/183 specimens, which are undescribed, include MU but more derived in somecranial features. These New Zealand Oligocene dolphins,“dalpiazinid” archaic odontocetes that are structurally similar to anewgroup of presented preliminarydetails of recent prospecting. Fordycecess of suc the given work, field more with increase will specimens tified, but it is likely that the number of Few Oligocene haveOdontoceti skulls beeniden unclear. other fossilmysticetes are identities of family The ital, and along-based and highcoronoid process. the supraoccip that extends beyond the apex of the squamosal an elongate zygomatic processof region, elongate nasals, a large temporal fossa, including anelongate and narrow intertemporal general these specimens have a long, narrow skull, senecker andFordyce, 2014,2015a,2015b).In 2012) and 2002a, 2002b), Barnes, like share similar cranialfeatures witheomysticetids 3) 2C, (Figure mysticetes Welltoothless preserved plete specimenreferences inTable 1). series-collection to giveread aneasy (see the com here MU willbe used for MHN-UABCS in the Eomysticetus Tohoraata and , Waharoa Micromysticetus Yamatocetus et al ., 1975). and (Okazaki,1995, /2017 Tokarahia (Sanders and (Sanders et al. (2012) (Boes 153 153 ------

METHODS AND MATERIALS / Oligocene cetaceans from Baja California Sur, Mexico RESULTS Oligocene cetaceans from Baja California Sur, Mexico RESULTS 154 154 matrix. (C)Dorsal view,juvenileskullofanunnamed MUEcSj1/29/141, and eomysticetid, reconstruction scheme,right. ventral view.Continuous lines show anatomicaldetails, and dashed lines markmissingareas show anatomy. Shadedwhite sediment EcSj5/24/123. (B)Left, dorsalview,partialskull,MUEcSj9/08/36,? Figure 2 / Late Oligocene cetaceanfossilsfrom Late BajaCalifornia Sur,México.(A)Dorsalview,skullof anunnamed MU aetiocetid, Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín /2017 Chonecetus sp., and right,concretionwiththepartial skullin Table 1. Representatives list of LateOligocenecetaceansfromBajaCaliforniaSur. list Table 1.Representatives Zealand. of descriptionSpecimens inprocess Ewan with thecollaborationof* Robert FordycefromtheUniversity ofOtago,Dunedin, New Odontoceti Chaeomysticeti Mysticeti ‘Archaeoceti’ Unknown Chaeomysticeti Eomysticetidae ?Balaenopteroidea Aetiocetidae ?Kekenodontidae Unknown Odontoceti ?Dalpiazinidae ?Squalodontidae Gen. etsp.indet. Gen. etsp.indet. Fam. indet.Gen.etsp. Fam. indet,Gen.etsp.indet. Fam. indet.Gen.etsp. Fam. indet.Gen.etsp. Fam. indet.Gen.etsp. Fam. indet.Gen.etsp. Fam. indet.Gen.etsp. Fam. indet.Gen.etsp. Gen. etsp.indet. Gen. etsp.indet. Gen. etsp.indet. Fam. indet.Gen.etsp. Fam. indet.Gen.etsp. Aetiocetus sp.indet. ?Chonecetus sp.indet. Fam. indet.Gen.etspp. Fam. indet.Gen.etspp. Gen. etspp.indet. Gen. etspp.indet. Taxon H-AC_cm2/726Prilsuladtmai ule aeOioeeCñd aMnoa a alsE inTembabichi ElCien CañadaLaMontosa,SanCarlos Late Oligocene Partialskullandtympanicbullae. MHN-UABCS_EcTm12//67/216 *MHN-UABCS_EcSj24/50/183 * H-AC_cm/122Partialskull. MHN-UABCS_EcTm9/91/292 H-AC_cm/227Partialskull. MHN-UABCS_EcTm9/82/257 H-AC_cm/224Braincase. MHN-UABCS_EcTm9/82/254 H-AC_cj53/5 riuae adbewt et.LateOligocene Articulatedmandiblewithteeth. MHN-UABCS_EcSj25/39/157 MNUBSES54/7 Partialskull. *MHN-UABCS_EcSj5/49/176 MNUBSES14/6 Partialskull. *MHN-UABCS_EcSj1/44/165 MHN-UABCS_EcSj12/41/203 Twopremolarsteeth. MHN-UABCS_EcSj24/59/206 H-AC_cj/511Leftdentarywithteeth. MHN-UABCS_EcSj5/35/151 SanJuan ElCien MesaElTesoro,SanJuandelaCosta. LateOligocene Partialskullwithrighttympanicbullae. MHN-UABCS_EcSj1/51/184 H-AC_cj/915Partialskull. MHN-UABCS_EcSj1/29/145 H-AC_cj/926Braincaseandfragments. MHN-UABCS_EcSj1/29/276 H-AC_cj/718Partialskull. MHN-UABCS_EcSj1/47/168 MHN-UABCS_EcSj1/29/141 MHN-UABCS_EcSj1/29/142 Braincase. MHN-UABCS_EcSj1/29/143 MHN-UABCS_EcSj5/24/123 Partialskull. MHN-UABCS_EcSj1/38/155 Partialskull. MHN-UABCS_EcSj1/94/296 Partialskullwithperiotics. MHN-UABCS_EcSj1/45/214 Leftperiotic(Fig.6A). MHN-UABCS_EcSj5/16/267 MHN-UABCS_ MHN-UABCS_EcSj5/18/95 H-AC_cj/63 ata kl,lf eitc(i.4) Late Oligocene Partialskull,leftperiotic(Fig.4A). MHN-UABCS_EcSj5/06/31 MHN-UABCS_EcSj9/08/36 H-AC_cj/67 etfotlfamn Fg B.LateOligocene Leftfrontalfragment(Fig.6B). MHN-UABCS_EcSj5/16/72 H-AC_cj/017Partialskull. MHN-UABCS_EcSj1/50/177 H-AC_g/128Sul ypncbla,dnay aeOioeeRoL uíia aPrsm.SnGeoi --- SanGregorio RioLaPurísima,Purísima. LateOligocene Skull,tympanicbullae,dentary. MHN-UABCS_Sg6/71/208 Specimen

EcSj5/12/48 4B). Partial skull,leftbullaandperiotic(Fig. and fragmentarybones(Fig.2B). Partial skull,tympanicbullae,fewteeth and bones(Fig.2C). one caudalvertebra,earbonefragments, Partial skull,fourthoracicvertebrae, cervical), fragmentarybones(Fig.3). Partial skull,15vertebrae(including mandible, vertebrae. Partial skullandtympanicbullae,left cervical vertebrae(Fig.2A). Skull, lefttympanicbulla,teeth,dentary, radius, ribfragments(Fig.5A). vertebrae; humerus,rightulnaand Skull, rightbulla,periotics,cervical Partial skull(Fig.5B) Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Material Late Oligocene Late Oligocene Tembabichi ElCien CañadaElMangle. PuntaMontalva. SanJuan Late Oligocene ElCien MesaElTesoro, SanJuandelaCosta. Late Oligocene Late Oligocene aeOioeeMs lTsr,SnJa el ot.E inSanJuan ElCien MesaElTesoro, SanJuandelaCosta. Late Oligocene Late Oligocene aeOioeeMs lTsr,SnJa el ot.E inSanJuan ElCien Late Oligocene MesaElTesoro, SanJuandelaCosta. SanJuan Late Oligocene ElCien SanJuan MesaElTesoro,SanJuandelaCosta. Late Oligocene ElCien MesaElTesoro,SanJuandelaCosta. Late Oligocene SanJuan ElCien MesaElTesoro,San JuandelaCosta. Late Oligocene Late Oligocene Late Oligocene SanJuan ElCien MesaElTesoro, SanJuande la Costa. SanJuan Late Oligocene ElCien MesaElTesoro, SanJuande la Costa. Late Oligocene aeOioeeMs lTsr,SnJa el ot.E inSanJuan ElCien MesaElTesoro, SanJuandelaCosta. Late Oligocene Late Oligocene Late Oligocene Late Oligocene SanJuan ElCien MesaElTesoro,SanJuandelaCosta. Late Oligocene Late Oligocene Late Oligocene Age Costa. Terreros ElSaladito,SanJuandela Costa. Cañada delaLuz,SanJuan Costa. Terreros ElSaladito,SanJuandela Costa. Terreros ElSaladito,SanJuandela Costa. Terreros ElSaladito,SanJuandela Carlos. Miembro PuntaSanCarlos, Costa. Mina LasCrucecitas,SanJuandela Tarabillas" San JuandelaCosta,"Arroyo Costa. Terreros ElSaladito,SanJuandela 1 Aguajito deCastro,CarreteraNorteN. Costa. Terreros ElSaladito,SanJuandela Costa. Terreros ElSaladito,SanJuandela Costa. Terreros ElSaladito,SanJuandela la Costa. Carlos. MesaElTesoro,SanJuande Miembro PuntaSanCarlos, Costa. Arroyo Tarabillas,SanJuandela Locality omto Member Formation /2017 lCe SanJuan El Cien SanJuan El Cien lCe SanJuan El Cien lCe SanJuan El Cien lCe SanJuan El Cien lCe Tembabichi El Cien lCe SanJuan El Cien lCe SanJuan El Cien SanJuan El Cien SanJuan El Cien SanJuan El Cien SanJuan El Cien lCe SanJuan El Cien El Cien lCe SanJuan El Cien Tembabichi San Juan 155 155

Oligocene cetaceans from Baja California Sur, Mexico RESULTS Oligocene cetaceans from Baja California Sur, Mexico RESULTS 156 156 4.1.1. SUBORDERMYSTICETI-AETIOCETIDAE 4.1. SYSTEMATIC PALEONTOLOGY to an undescribed specimen (OU 22294)fromto anundescribedspecimen the (Hernán EcSj1/38/155 dez-Cisneros, specimens are 2015). These similar and EcSj1/94/296, 6B); and unprepared skulls, MUEcSj1/45/214, frontal fragment, MU EcSj5/16/72(Figure periotic, MU EcSj5/16/267 (Figure 6A); a left Probableare kekenodontids represented by:a tral groove,and elongate thick zygomatic process e (see Barnes nasal bones5–6%longer than in note include: elongate and narrow details. Features of fine lack generally elements postcranial obliterated. occipital condyles, The ear bones, and sutures which areclosed but mainly notfusedor the cranial vidual, asindicated bythe nature of inferred age is a subadult class indi 2011). The gomatic width(following Pyensonand Sponberg, derived~3.03 m fromthe bizy ed bodylength of ~320 mm andan estimat a bizygomatic width of ~760mm, withacondylobasal askull length of of Description. (Fischer approximately,Ma 25 to –28 Age Oligocene Late Formation. Arce. March 1996. Agundez Raúl and Barba González Gerardo by W), 110.70042 La Paz, Sur, Baja California N, México. Collected (24.43929 Costa la de Juan Locality. (Figure 2A). Material. Oligocene; Fordyce, 2004)from NewZealand. the Waitaki Valleyof region (26 Kokoamu Greensand-basal Otekaike Limestone / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Neoceti et al ElSaladito,El Saladito”, San “Mesa H-AC_cj/413 skull MHN-UABCS_EcSj5/24/123, Aetiocetidae Emlong, 1966 ., 1995). t al ?Aetiocetus Cetacea Brisson,1762 El CienFormation. Mysticeti Gray, 1864

The specimen (Figure The 2A) consists Fordyce &deMuizon, 2001 ., 1995), a wide and short mesoros ? Aetiocetus Emlong, 1966 sp. — Aetiocetus weltoni 8 M, Late Ma, 28+ - - - - - /2017

ittal crest, aslightlyconvex supraoccipitalshield with lobed end, intertemporal region withoutsag infraorbital foramina, thinandelongate lacrimal Other notable features includemultiple dorsal dingensis Fucaia buelli sookensis Morawanocetus yabukii from those of cotylalveus polydentatus torum featuresThese contrast notably with in itsmiddleportion,andawidetemporal fossa. squamosalwithout the thin dorsoventral shape of lated body length is ~2.86 m (following Pyenson (following m ~2.86 is length body lated calcu the and mm, ~300 at estimated is width ic 400 mm,withoutoccipitalcondyles,is bizygomat jaw fragments with few teeth; its preserved length bullae, apartial with both tympanic skull and of Description. (Fischer Age. Formation. gust 1992. Au Arvizá. Castro Ruben and Barba González Sur,California México. Collected by Gerardo Baja Paz, La W), 110.69608 N, (24.40859 Costa Locality. ments. (Figure 2B). tympanic bullae,skull, fewteeth and jaw frag Material. frontal. thesupraorbitalprocess of edge of the anterior the nasals isforward of rior edge of partially roofed bythe premaxilla, and the ante such asanincompletely open mesorostral groove for thegroup (Fitzgerald, 2010), synapomorphies placed in imen is occipital crest on middle line.external spec The with a semicircular-triangular outline and a weak (Barnes (Barnes 28 to 25 Ma approximately,Ma 25 to Oligocene Late28 Russell, 1968 (see also Barnes Pledge, 2005(see also Fitzgerald, 2010). et al Emlong, 1966. The features differ in part Mina “Las Crucecitas”, SanJuan Mina“Las de la both of Barnes Barnes bothof MHN-UABCS_EcSj9/08/36, partial MHN-UABCS_EcSj9/08/36, Marx ., 1995). ? ElCienFormation. Chonecetus et al Aetiocetus tomitai The specimen(Figure The 2B) consists ., 1995), ? et al Chonecetus Aetiocetus Barnes Barnes ., 2105and Russell, 1968 et al A. weltoni because it has some becauseithas et al sp. ., 1995,and Barnes Barnes ., 1995, Willungacetus al , and Fucaia goeder et al et al Chonecetus Aetiocetus Aetiocetus ., 1995), ., 1995, ------4.1.2. SUBORDERMYSTICETI-EOMYSTICETIDAE hcns fthesagittalcrest. thickness of supraoccipital and anteroposterior extension of named recently the with contrasts EcSj9/08/36, ly,MU not project laterally or dorsolaterally. Converse thesupraoccipitalthat apparently does crest of V-shape frontoparietal suture, andalow nuchal the rostrum; possibly a 10° tothe lateral edge of of less profile a with flat, and low edge braincase gerald (2010) recognized for that genus: dorsal that Fitz because itshowssynapomorphies some Nevertheless, the specimenisplaced in and 1968 sell, with the type species of features ~240 mm. These contrast al processesof down shape, and a total width between postorbit temporal region (~59 mm wide) with a U upside crest onthe intertemporal region; abroad inter the frontal; a convex, softandtenuous sagittal of line middle the in suture fine a are: note of tures indicated bygenerally closed cranialsutures. Fea and Sponberg, age is adult, class as 2011).The fully closed, by cranial sutures which are moderately but not associated elements. age class is indicated The ajuvenile mysticete, and apartial of skull of sists Description. (Fischer Age. Formation. November 1999. and two anonymous (Luisaand Memo), collectors Barba; Lawrence G. James Barnes; L.Goedert, González Gerardo by Collected Sur,México. nia (24.47366 N, 110.69646 W), La Paz, Baja Califor Locality. bone fragments, andbonefragments(Figure 2C). four thoracicvertebrae, onecaudal vertebra, ear Material. Eomysticetidae 2002b &Barnes, Sanders 28 to 25 Ma approximately,Ma 25 to Oligocene Late28 Eomysticetidae gen.et.sp. indet.1 Fucaia buelli et al Chaeomysticeti Mitchell, 1989 MesaTesoro, San Juan dela Costa MHN-UABCS_EcSj1/29/141, skull, ., 1995). e.g. ElCienFormation. The specimen(Figure The 2C) con tejnto fthe and squamosal the junction of F. goedertorum (see Marx Chonecetus (Barnes (Barnes et al , C. sookensis C. sookensis ., 2015)inthe et al Chonecetus ., 1995). Rus Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín ------

Eomysticetidae because it shows: rigid, firmly su firmly rigid, shows: it because Eomysticetidae neros (Hernández-Cis squamosal posterolateralof part the on fingertip a like prominence squamosal a occipital crest, verticalexternal nuchal crests; and similar to mammalodontids andarchaeocetes; an a supraoccipitalshieldwithsemicircular outline thick intertemporal region with a fine sagittal crest, (see 1995); ashort andrelativelyalso Okazaki, similar toY elongate, triangular, nasalbones;awidefrontal Pyensonand Sponberg, 2011).Features include: (following m ~3.03 is length body and mm, ~320 lobasal length is ~620 mm; bizygomatic width is parietal is still quite apparent. Estimated condy age class issubadult as indicated by cranial su vertebraeThe ~1600 mm. are unprepared. The complete condylobasal length couldhave reached whitmoreimysticetus proportionsmm. Assuming similar to those in 1100 trum apex, withapreserved total length of the condyles apartial lacking skull, and ros of Description. (Fischer Age. Formation. and Memo),November 1999. Goedert, and two anonymous (Luisa collectors L. James Barnes; G. Lawrence Barba; González Baja Paz, La Sur,California W), México. Collected by Gerardo 110.69646° N, (24.47366° Locality. bones(Figuretary 3). vertebrae, four lumbar vertebrae, andfragmen tial fourskull, cervical vertebrae, eight thoracic Material. necker andFordyce, 2015a,2015b). a supramastoid crest (featuresby discussed Boesse longitudinally twisted zygomatic processthat lacks anteroposteriorly oriented zygomatic process; and the skull; ed nuchal crest as the highest pointof tured nasals andpremaxillae; posteriorly elevat 28 to 25 Ma approximately,Ma 25 to Oligocene Late28 et al Eomysticetidae gen.et.sp. indet.2 et al ., 2014). The specimen isplaced within ., 2014). The MesaTesoro, San Juan dela Costa MHN-UABCS_EcSj1/29/142, par ., 1995). amatocetus canaliculatus ElCienFormation. The specimen (Figure 3) includes 3) (Figure specimen The Sanders and Barnes, 2002the and Barnes, Sanders Okazaki, 2012 Okazaki, /2017 157 157 Eo ------

Oligocene cetaceans from Baja California Sur, Mexico RESULTS Oligocene cetaceans from Baja California Sur, Mexico RESULTS 158 158 diagonal linesmarkbrokenareas. anatomical details,dashed linesmarkmissing anatomy,and premaxillae asthedistinctivefeature. Continuous linesshow EcSj1/29/142; reconstruction scheme,right,redlinesshow the Figure 3 uncertain contribution fromthe premaxilla. This the maxilla with an the ascending processof of theposterior margin bital notch.suture forms This the lacrimal and/or antor ly toward the region of orbit, a serrate suture runs obliquely anterolateral the frontal. Posteriorly, the behindthe level of a broad posterior apexforms that covers part of the premaxilla which tended ascending processof the frontals; andanex groove; anarial processof narrow elongate nasal bones; a wide mesorostral note include: very completely fused. Features of tures which are well closed, but distinct, andnot / Dorsalview,skullofanunnamed MU eomysticetid, Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín - - - /2017 4.1.3. SUBORDERMYSTICETI-CHAEOMYSTICETI senecker andFordyce, 2015a,2015b). large temporal fossa (characters reviewed by Boes temporal region exposed (parietal + frontal); and a medially elongated and transversely narrow; inter frontal and premaxillae; supraorbital processof nasals sutured rigidly or firmly rostrum, long and other eomysticetids in features including:anarrow isphenetically similar to the cranial morphology Eomysticetidaeplaced in is specimen The because data). unpublished (Hernández-Cisneros, ticetids Zealand eomysticetids, andother knowneomys maxilla from pre the of structure latter the in differs specimen clude: a periotic bone with very flat (transversely flat very with bone periotic a clude: note in that are not completely fused. Features of aremens subadults asindicated bycranial sutures ingful standardpreserved. dimensions Both speci mean no with but EcSj5/06/31, MU with size in fragmentary,comparable is EcSj5/18/95 MU laenopteroidea in Pyenson andSponberg (2011). the equations for stem Mysticeti andstem Ba and itscalculated size body is6.65to 7.70 musing gomatic process. condyle widthis~126 The mm, the zy midline at the condyle to the margin of fromthe dimension based on ~750mm the of bizygomaticestimated an width has EcSj5/06/31 both, but other size estimates are possible. MU periotic bone. condylobasal length The lostforis cranialmorphology,dorsal in but share asimilar other each from differ which skulls partial two of Description. (Fischer approximately,Ma 25 to –28 Age Oligocene Late Formation. González Barba,December1991andMay 1994. Sur,California México. Collected by Gerardo Baja Paz, La W). 110.69512 N, (24.43916 spoils Locality. periotic (Figure 4). and bulla left a with skull partial EcSj5/18/95, tial with left skull periotic; and MHN-UABCS_ Material. et al Family indet.gen.et. sp. indet. San Juan de la Costa, El Saladito, mine H-AC_cj/63, par MHN-UABCS_EcSj5/06/31, ., 1995). El CienFormation. Yamatocetus, Eomysticetus The specimens(FigureThe 4) consist , the New ------in situ Figure 4 sal posteriorly directed lateralin view (see Marx the squamo processital, and apostglenoid of thesupraoccip triangular constriction; shape of the periotic; transversally widened intertemporal chaeomysticetes: compound posterior process of features indicate that the fossilsare a speciesof the frontal (Geisler and Sanders, 2003). But, other well positioned anteriorly surfaceof onthe dorsal crest orbital an or 1989) (Mitchell, teeth of sence for Chaeomysticeti,synapomorphies suchab as fossilsThe are too incomplete possibleto assess (Hernández-Cisneros crest transverse largewith a single aperture without a prominent acoustic meatussuperior process; and an internal the periotic include: a ble primitive charactersof balaenopterids (Ekdale cess of similar tothenarrower andmore elongated pro terior process with a marked facial nerve sulcus, compressed) anterior process;pos and compound of MU EcSj5/06/31, ventral view. (D-D’) broken left periotic of MUEcSj5/18/95,medial view,left,periotic ofMUEcSj5/06/31,ventralview.(D-D’)brokenleft and lateralview,right. (A-B)Dorsal left; view,partialskulls,unnamed and MUEcSj5/06/31, bone periotic MUEcSj5/18/95,right.(C)Left mysticetes, et al ., 2011). Nota et al ., 2014). Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín ------ODONTOCETES 4.1.4. SUBORDERODONTOCETI-ARCHAIC 5A). right bulla, cervical vertebrae, and teeth (Figure right forelimb (humerus, radio, ulna),periotics, Material. published data). un (Hernández-Cisneros features cranial other and 2005) mainlyinthe ear bone morphology 2016, andM. Fordyce, 2015, from different quite are EcSj5/18/95 MU and EcSj5/06/31 MU imens and Fordyce, 2015,onthese features). spec The Family indet.gen.et.sp. indet. H-AC_cj/24, skull, MHN-UABCS_EcSj5/12/48, Odontoceti Flower, 1867 parki Whakakai waipata Whakakai Benham,1937 (see also Fordyce, Horopeta umarere Tsaiand Fordyce, /2017 Tsai

159 159 and - -

Oligocene cetaceans from Baja California Sur, Mexico RESULTS Oligocene cetaceans from Baja California Sur, Mexico RESULTS 160 160 Shaded whiteareas show sediment matrix. odontocete, MU EcSj24/50/183(Fordyce Figure 5 Formation. rence G. February Barnes 1993. Lawand AndreasKnieth Barba, rardo González Shelton P.Angel Meza Ortega; Applegate, Ge Sur,California México. Collected by Miguel spoils (24.44249N, 110.69106 W), La Paz, Baja Locality. to as “ referred earlier was EcSj5/12/48 MU 1975). rin, Per see fusion, of significance (on body vertebra nuchal crest, and epiphysesfused to the cervical by completely closed cranial sutures, a developed inferred age is adult, class as indicated2011). The for stemOdontoceti in Pyensonand Sponberg, (following ~1.41m theequation bodysize of ic widthestimated at ~200 mm, andestimated therostrum apex), bizygomat of loss because of (substantially lessthancondylobasalmm length ~400 apartial with apreservedskull length of of Description. (Fischer Age. / (A)Dorsalview,skullof unnamedodontocete, MUEcSj5/12/48.(B)Dorsalview,skull ofanunnamed archaic archaic Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín 28 to 25 Ma approximately,Ma 25 to Oligocene Late28 Agorophius et al San Juan de la Costa, El Saladito, mine ., 1995). ElCienFormation. The specimen (Figure The 5A) consists ” sp. (Cruz-Marín, 1997),but its et al ., 2012).Continuous linesshow anatomical detailsand diagonallinesmark brokenareas. - - - - - /2017 la risesposteriorly over the frontal, extended near teeth are heterodont but notpolydont. maxil The intertemporal regionprominent. is small The the squamosal fossa. The the anterior margin of occipital shieldwithasemicircular outline behind short mesorostraland snout groove, andasupra a shortened rostrumhas skull The withanarrow mm). ~200+ width: bizygomatic mm; ~450–500 us pygmaeus Fordyce,and mm, 2002) ~238 width: ic rayi note, the specimen issmallcompared with both Simocetus rayi Agorophiidae (Fordyce, to Godfrey 1981, different quite is morphology neirt h nobtlnth ayo the latter anterior to the antorbital notch. Manyof foraminalie well andsulci forwardthe rostrum, on premaxillaryfossasac orbit. and associatedThe the of exposed above dorsally the elevated roof the frontal supraorbital margin, leavingthe rest of the supraorbital process, but does not reach the of to the frontoparietal suture; laterally overlaps part cnyoaa lnt: 4+ m bizygomat mm; 449+ length: (condylobasal Mle, 89 (odlbsl length: (condylobasal 1849) (Müller, Fordyce, features 2002.Amongst of et al ., 2016) and closer to Agorophi S. - - - - 35 m u jdig rm oprbe spec comparable (USNM 205491,below)imens itscondylobas from judging but mm ~305 a partial skull witha preserved length of sists of Description. (Fischer Age. Formation. neros. February 2008. Cis Hernández Ehécatl Atzcalli and Cruz, Mata Martín Ricardo Priscila MoralesOrtega; Mirsha Barba; Fordyce;González Ewan GerardoRobert Paz, Sur, Baja California México. Collected by llas,(24.44249° N, minespoils 110.69106°W) La Locality. (Figure 5B). Material. netic analysis. descriptionandphylogea detailed morphological onomy. Systematicbe resolvedshould questions by A. pygmaeus featuresare shared plesiomorphic with and the flat, wide and slightly concave palatine. concave slightly and wide flat, the and thefrontal; and narrowpostorbital processof the narrow andrelatively longnasals, anelongate and shallowthan fossaeand, thepremaxillarysac are more anterior (Fordyce unnamed specimenUSNM205491fromOregon kazakhstanicus P 1994; Tanaka andFordyce, 2014,2015a,2015b), meffordorum than flat trally (Fordyce with anarrow andelongate premaxillary sac fossa plus premaxilla without a posterolateral fold but posed at aprominent intertemporal constriction, ial andarchaic“snout”, features like parietals ex note include the prominent nar tight. Features of by cranial sutures which are relatively closedand adult, inferredas indicatedis age class length. The al length could have been double the preserved atriocetus ehrlichi 28 to 25 Ma approximately,Ma 25 to Oligocene Late28 et al et al et al Family indet.gen.et.sp. indet. San Juan de la Costa, Arroyo Tarabi Uhen(2010), Waipatiidae (Fordyce, , andfor now they donothelp with tax MNH-UABCS_EcSj24/50/183, skull ., 1995). ., 2012). The skull ismore., 2012). The dorsoven , Dubrovo andSanders, 2000,orthe ., 2012). The rostrum., 2012). The islessconcave ElCienFormation. The specimen(Figure The 5B) con S. rayi Vn eee, 1865), Beneden, (Van S. rayi Fordyce (2002), . Other features include: S. rayi Albertocetus Patriocetus and Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín ------?KEKENODONTIDAE 4.1.5. SUBORDER‘ARCHAEOCETI’ spoils (24.44249° N,spoils 110.69106°W),LaPaz, Baja Locality. periotic (Figure 6A). Material. men isnotallocated tothefamily. family isnow considered uncertain, and the speci that possible Dalpiazinidae, butof the typology Fordyce butnot clear itis whether these are the same the unprepared specimen, MUEcSj1/45/214, similar totheelements EcSj5/16/267, is of MU ezoidal-rectangular in medial view. periotic, The trap is process anterior the and concaveprofile a the shape isrectangular, the superior processhas or 1847), ichenbach, with thehighstructure seenin ovoid;is thesuperior processlowis compared 2014) from suprameatal NewZealand. The area imen OU22294(Fordyce 2004;Clementz 10), and isquite similar to the undescribed spec onamata Kekenodon which istransversely narrow inventral view, like note include the elongate body mm. Features of 51 periotic a maximumhas preserved length of The 2016). Tsai, and (Hernández-Cisneros cetes present in mysticetes and odonto morphology 2004; Uhen, Fitzgerald, 2010), andcontrast widely withthe 1999; Gingerich, and Luo 1936; (Kellogg, basilosaurids similar tothata shape of periotic without theposterior process, andwith Description. (Fischer Age. Formation. Cruz Marin.March 1993. González Barba; Lawrence G. Barnes, and Arturo Sur,California México. Collected by Gerardo Basilosaurus isis Basilosaurus ~27 Ma approximately, Late Oligocene ?Kekenodontidae gen.et.sp. indet. et al ?Kekenodontidae Mitchell, 1989 et al San Juan de la Costa, El Saladito, mine MHN-UABCS_EcSj5/16/267, left ., 1995). Archaeoceti Flower, 1883 . (2012) identified the specimen as a as specimen the identified (2012) . ElCienFormation. The specimen (Figure The 6A) isa left Hector, 1881 (see Hector’s Fig. Hector’s (see 1881 Hector, (Andrews, 1904).Inlateral view Dorudon atrox Dorudon Zygorhiza kochii (Andrews, 1906), /2017 et al (Re 161 161 ., - - - - -

Oligocene cetaceans from Baja California Sur, Mexico RESULTS DISCUSSION / CONCLUSION / Oligocene cetaceans from Baja California Sur, Mexico AKNOWLEDGMENTS 162 162 lines markmissing anatomy. ?kekenodontid-like animal, specimen MUEcSj5/16/72,dashed animal, MUEcSj5/16/267.(B)Dorsal viewof afrontal fragment, Figure 6 described specimen OU 22294 (Clementz EcSj1/38/155 MU (partial areskulls), pheneticallysimilar totheun and EcSj1/94/296 MU MU EcSj5/16/72(partial frontal, Figure 6B); needed. Other unprepared specimens, such as species; detailed description and comparison are / (A)Medialperiotic, view,left ?kekenodontid-like Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín et al ., - /2017 5. Discussion and differences with Oligocene cetaceans from cetaceans Oligocene with differences and the PeninsulaOlympic inWashington (U.S.A.) similarity withthe fossilcetacean assemblage from the Pacific margin, remarkingother areas upon of the Oligocene cetaceans from Mexico with es of Barnes (1998) briefly discussed apparent differenc Basin. Pacific the around Cetacea of history cene towardsthe continually expanding Late Oligo Cetaceans from Sur contribute Baja California braincase (Hernández-Cisneros, 2015). flat a and process, zygomatic short region, poral 2014: Fig. 2)ina narrow andlongest intertem biogeography. functional and ecological shifts, andchanging transitions, the Cetacea including morphological Sur will elucidate evolutionBaja California of Late1995). The Oligocene cetacean fossilsfrom and the Neogene cetacean groups (Fordyce which include a critical link between archaeocetes gocene cetaceans (Uhen andPyenson, 2007), about the Oli gap a considerableis information than isapparent from the literature. Thus, there –as revealed by undescribed museum collections– vances, there is amuch greater known diversity such ad large character matrices. Inspite of of accounts withcladisticanalyses morphological the latter articles are detailed means that many of the specimens 2015b), andothers. nature The of Fordyce (2015); Tanaka andFordyce (2014,2015a, er and Fordyce (2014, 2015a, 2015b); Tsai and and itsdiversity, Oligocene cetacean evolution the framework of have vances incetacean paleontology expanded Tablespecies (Appendix, A1). Many recent ad named formally several include Basin Pacific the At present, the reported Oligocene cetaceans from described. formally parisons may become outdated unless speciesare from Sur and NewZealand, com Baja California Oligocene Cetacea rapidly expanding diversityof (Japan),Hokkaido andNewZealand.Given the e.g. Fitzgerald (2010); Boesseneck et al ., ------7. Acknowledgments 6. Conclusion ies set fcetaceanevolution. diverse aspectsof world, the materials will expand of understanding with newfossil cetaceans from elsewherethe in and San Gregorio Formation (Late Oligocene). As the El Cien Formation (Oligocene-Early Miocene) ti), and kekenodontid-like cetaceans,from mostly cetes, mysticetes (Aetiocetidae and Chaeomystice hitherto unreported archaic odonto presence of museumsare prepared. Recent studies indicate the fieldwork continues and the specimens collected in cetacean diversity as to increase the knowledge of from NorthAmerica. Therea great is expectation Late Oligocene cetaceans records of ern-most ses orabstracts. fossilsrepresent These the south Published years. 70 details are sparse, andsomeappear only inthe last the in briefly reported mals (mostlycetaceans and a fewdesmostylians) Peninsula,Late including Oligocene marinemam Cenozoicfossils assemblages distributed along the Sur has producedBaja California some important possible. This study was developed during AEHC’s in New Zealand, that made this workinternship the for support financial for COSCyT-BCS and (Beca CONACYTMixta, 290842), CICIMAR-IPN (SAI), CCA-IPN thank We 20131259). SIP: (project comments for and work field supporting for Sánchez Nava H. Enrique to and details, ogy Tobias Schwennicke for its commentsabout geol deron forand review. the comments to Thanks columns.stratigraphic to J. Thanks Lopez-Cal the with support their for González Guadalupe rence G. andJames Barnes Goedert, to Maria thiswork, especially to Law to the collectors of and constructive criticism during the preparation and Robert W. Boessenecker for their comments and comments. WeCheng-Hsiu Tsai alsothank cero andanonymousreviewer for their assistance We giveto theeditors, ourthanks toSergio Lu Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín ------8. References Alexadri-Rionda, R., Martínez-Vera, Espinosa- A., ship, 290143. de CienciayTecnología (CONACYT) scholar rinas (CICIMAR-IPN), and the Consejo Nacional cional –Centro Interdisciplinariode CienciasMa MSc thesissupported by Instituto Politécnico Na Barnes, L.G.,Barnes, Kimura, M., Furusawa, H., Barnes, fossilL.G., marine 1998, The sequence of Applegate, S.P., Wilson,E.C., 1976,Correlation Formation, Cien El The 1986, S.P., Applegate, Andrews, C. W., 1906, A Descriptive Catalogue Andrews, C. W., 1904,Further notes on the Federal, México, Servicio Geológico Sur,de Baja California 1:500000:Distrito Estado Geológico-Minera Carta 2008, L.A., H., Terán-Ortega, Maraver-Romero, D.V., E.G., Arriaga-Meléndez, Aramburu, Island Arc, 3,392–431. North America and Japan:western The (Mammalia; Cetacea; Mysticeti) from and Classification Oligocene Aetiocetidae distribution of 1995, H., Sawamura, 1, 26–79. investigación: Paleontología de Vertebrados, mammal assemblages in México, Avances en 6. Universidad NacionalAutónoma de México, de Geología: México, Instituto de Geología- (resumen), México, anda possible new phosphate source Arroyo Guadalupe, Sur, Baja California atMiocene sections SanTelmo Point and fossiliferousUpper Oligocene orLower of Ciencias Geológicas, 6,145–162. Sur: Revistain Baja California Mexicana de Oligocene and Early Miocene age strata of London, BritishMuseum,1–324. the Tertiary Fayum, Vertebrata of Egypt: of Geological Magazine, 5,11–215. Part Egypt. 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Oligocene cetaceans from Baja California Sur, Mexico REFERENCES / APPENDIX Oligocene cetaceans from Baja California Sur, Mexico APPENDIX 170 170 Table A1.Recognized Oligocenecetaceansfrom thePacificBasin. APPENDIX Tokarahia kauaeroa Tohoraata waitakiensis Tohoraata raekohao Yamatocetus canaliculatus Willungacetus aldingensis Aetiocetus polydentatus Tokarahia lophocephalus Aetiocetus weltoni Aetiocetus cotylalveus Aetiocetus tomitai aff. Morawanocetussp. Morawanocetus yabukii Ashorocetus eguchii Fucaia buelli Fucaia goedertorum Chonecetus sookensis Janjucetus hunderi Mammalodon hakataramea Mammalodontidae gen.etsp.indet. Mammalodon colliveri ‘Squalodon’ gambierensis Kekenodon sp. Kekenodon onamata Waharoa ruwhenua Horoperata umarere Mauicetus parki ‘Mauicetus’ brevicollis Sitsqwayk cornishorum Matapanui waihao Whakakai waipata Waipatia hectori Otekaikea marplesi Waipatia maerewhenua Arktocara yakataga Simocetus rayi Otekaikea huata Odontoceti Mysticeti ‘Archaeoceti’ / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Taxon/ species AM114,LC 307USA LACM 131146,138027 Specimens U153 U24 NewZealand OU 11573,OU22545 MHV 0,1 Japan KMNH VP000,017 NCVC 44 Canada (NMC-VPC) 64443 MZM 5 NewZealand NMNZ MA653 MZM.36NewZealand NMNZ Ma.306 M 262 Australia NMV P216929 Australia NMV P199986 SM243 USA USNM 214830 USA USNM 256517 CP120 USA UCMP 122900 WM804USA UWBM 84024 WM896USA UWBM 82916 SM220USA USNM 25210 Australia NMV P48794 M L42NewZealand OMC GL402 M.N.1 Japan AMP. No.12 AP03 Australia SAMP40034 MG 1 NewZealand OM GL412 MG 1 NewZealand OM GL410 MG 2 New Zealand OM GL421 M o Japan AMP No.2 Japan AMP No.9 Japan AMP No.1 Japan AMP No.3 U225NewZealand OU 22235 NewZealand OU 22178 U206NewZealand OU 22026 U204NewZealand OU 22044 U198NewZealand OU 12918 OU 21927 U205NewZealand OU 22095 U236NewZealand OU 22306 /2017 U29 NewZealand OU22294 OU21982 Australia New Zealand New Zealand Country (Fordyce, 2004;Clementz (Benham, 1937,1942;Fordyce,2005) (Boessenecker &Fordyce,2015b) (Boessenecker &Fordyce,2015a) (Boessenecker &Fordyce,2015a) (Fordyce, 2004;Fitzgerald,2004) (Boessenecker &Fordyce,2014) (Boessenecker &Fordyce,2014) (Boessenecker &Fordyce,2016) References (Boersma andPyenson, 2016) (Tanaka &Fordyce,2015b) (Tanaka &Fordyce,2015a) (Tanaka &Fordyce,2014) (Fordyce andMarx,2016) (Tsai &Fordyce,2015b) (Peredo &Uhen,2016) (Tsai &Fordyce2016) (Okazaki, 1994,2012) (Tsai &Ando,2015) (Barnes (Barnes (Barnes (Barnes (Barnes (Barnes (Marx etal.,2015) (Fitzgerald, 2006) (Fitzgerald, 2010) (Fitzgerald, 2010) (Marples, 1956) (Fordyce, 1994) (Fordyce, 2002) (Emlong, 1966) (Russell, 1968) (Pledge, 2005) (Hector, 1881) et al et al et al. et al et al et al et al ., 1995) ., 1995) ., 1995) ., 1995) ., 1995) ., 1995) , 2014) crabs arebasedonnew observations(Hernández-Cisneros, from thelocality “ArroyoSan dates 2012).Theageisbased onisotopic the Cerrodistributions ofcetaceanfossilsand ElPilóndeSanIsidro,BajaCalifornia Sur(26.198878°N,112.056659°W).Stratigraphic Figure A1 112.184059 W(Kim and Barron,1986). Raymundo”, 26.499422 N,112.508537W(McLean SanGregorioFormation,stratigraphic information summarized fromLa based Púrisima onGanz(1996),section closeto et al. , 1987)anddata from biostratigraphic “La Ventana”locality,26.116680 N, Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín /2017 171 171

Oligocene cetaceans from Baja California Sur, Mexico RESUMEN Oligocene cetaceans from Baja California Sur, Mexico RESUMEN 172 172 vanderhoofi similarities (Plata-Hernandez, 2002)and sharefossils also someconspicuousinvertebrate as on new observations(Hernández-Cisneros, 2012).Tembabichi and SanJuan members are considereddue lithological correlative Calera” closetoTembabichifisher village(25.26594167N,distributions 110.9622556W).Stratigraphic of cetaceanfossilsarebased Figure A2 / Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín Generalized stratigraphy of TembabichiMember, ElCienFormation (Plata-Hernandez, from cañada“La 2002),typesection , and Mytilus sp. (Fischer, et al ., 1995,Vera-Dimas, 2013). /2017 Diplochaetetes mexicanus , Anadara et al Figure A3 ., 1995). Stratigraphic distributions of., 1995).Stratigraphic cetaceanfossilsarebased onnewobservations(Hernández-Cisneros, 2015). Generalized stratigraphy ofzone SanJuanMember, SanJuandelaCosta(Schwennicke, 1994;Fischer ElCienFormation, at Boletín de la Sociedad Geológica Mexicana Geológica Sociedad la de Boletín /2017 173 173

Oligocene cetaceans from Baja California Sur, Mexico RESUMEN