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Carranza-Castañeda, Óscar, 2006, Late Tertiary fossil localities in central Mexico, between 45 19°–23°N, in Carranza-Castañeda, Óscar, and Lindsay, E.H., eds., Advances in late Tertiary vertebrate paleontology in Mexico and the Great American Biotic Interchange: Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias, Publicación Especial 4, p. 45–60.

Late Tertiary fossil localities in central Mexico, between 19º–23ºN

Óscar Carranza-Castañeda*

ABSTRACT

Only 35 years ago, the continental late Tertiary biostratigraphy of Mexico was almost unknown. Most of the information regarding previous reports came from the Yepómera fauna, located in northwest Chihuahua. From central Mexico, the only known faunas were Tehuichila in the State of Hidalgo, Rancho La Goleta in the State of Michoacán and Rancho El Ocote in the State of Guanajuato, with the inconvenience that these faunas were referred only to the Pliocene age. Recent studies in the sedimentary basins of central Mexico (between latitudes 19°N and 23°N) have shown a wealth of diversity and abundance of Cenozoic vertebrates that represent the Hemphillian and the Blancan mammalian ages. Besides, our results have yielded relevant new information, revealing central Mexico as an important area for mammalian migrations during the Blancan.

Key words: stratigraphy, paleontology, mammals, fossils, basins, Hemphillian, Blancan, Mexico.

RESUMEN

La estratigrafía continental del Terciario tardío de México, hasta los años setenta del siglo pasado, estuvo basada en la información de la fauna de Yepómera en el noroeste de Chihuahua. En el centro de México, la información sobre la estratigrafía y contenido fósil de las cuencas, fue escasa y se basó sólo en la información disponible de las faunas de Tehuichila en el estado de Hidalgo, la fauna de La Goleta en el estado de Michoacán y la fauna de Rancho El Ocote, en el estado de Guanajuato, todas referidas al Plioceno. Los trabajos recientes efectuados en las cuencas sedimentarias del centro de México, entre los paralelos 23° y 19°N, han demostrado la diversidad y abundancia de vertebrados fósiles, que están representando dos edades de Mamíferos, Henfiliano y Blancano, además de proporcionar información acerca de las migraciones de faunas hacia el centro de México, durante el Blancano.

Palabras clave: estratigrafía, paleontología, mamíferos, fósiles, cuencas, Hemphilliano, Blancano, México.

INTRODUCTION late Tertiary stratigraphy of central Mexico was poorly known until the second half of the past century; it was The continental late Tertiary stratigraphy of Mexico for biased, incomplete and based on isolated fossil findings many years was based mainly on the published papers without any stratigraphic control, which did not allow of the Yepómera fauna, northwestern Chihuahua. The to make any correlations between the Mexican faunas. The results of the investigations carried out in the sedimentary basins of central Mexico, between 19º *Centro de Geociencias, Campus Juriquilla, Universidad Nacional Autónoma de and 23º N, have shown that in these basins there is a México, Querétaro, Mexico. E-mail address: [email protected] large fossil diversity that will contribute to a better un-

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 46 Carranza-Castañeda derstanding of migrations and the evolution of diverse standing, in this paper the study area has been sepa- taxonomic groups. Besides, the fossil material has been rated in the most complete stratigraphic sequences. important to establish the age of the basins, which for many years were considered filled only by Quaternary Rancho El Ocote Area alluvium in the geologic maps, and that their origin and sedimentation were the result of a single geologic event. The field work carried out at Rancho El Ocote allowed The purpose of this paper is to communicate the recent to establish that in this locality two stratigraphic levels advances in the knowledge of the better studied basins occur, each with a different lithology and faunal con- from the Transmexican Volcanic Belt and the latest fos- tent. In addition, an unconformity is present, which sil discoveries of their faunal content. In the second half separates the strata that bear the early Blancan fauna. of the last century, the Instituto de Geología, UNAM, The results of the taphonomic analysis made in started the study of the main basin in central Mexico, the GTO 2B locality showed that only in the basal and now is sponsored by the Centro de Geociencias, layer, named Rhino Level (because it is the only layer UNAM, Campus Juriquilla, Querétaro. where it is possible to find rhinoceros material), the genera Nannippus minor (=Nannippus aztecus), and Abbreviations Neohipparion are abundant, and Teleoceras, Osteoborus, Agriotherium, Machairodus, and Megalonyx are pres- COLO Colotlán ent. A late Hemphillian age was determined for this GTO Guanajuato layer. HGO Hidalgo In the overlying bed, named White Layer because HUAN Huanusco of its lithology of fine grained sand with volcanic ash, the JAL Jalisco equids Dinohippus mexicanus and Astrohippus stockii JUCH Juchipila are abundant, also a fibular fragment of Glossotherium MICH Michoacán was recovered in the top of the section. Based on the NAY Nayarit equid species, the age of this layer was determined as QRO Querétaro latest Hemphillian. TEO Teocaltiche The volcanic ash lenses present in this sequence TECO Tecolotlán were dated by the fission-track method, giving an age of ZAC Zacatecas 4.8 ± 0.2 Ma, which corroborates the late Hemphillian age based on the fauna described in previous papers (Table 1) (Carranza-Castañeda and Ferrusquía-Villafranca, GUANAJUATO STATE 1978, 1979; Miller and Carranza-Castañeda, 1984; Carranza-Castañeda, 1989; Carranza-Castañeda and San Miguel de Allende Basin Walton, 1992; Carranza-Castañeda and Miller, 1996; Miller and Carranza-Castañeda, 1996; MacFadden and Previous works. The first mention of the San Miguel de Carranza-Castañeda, 2002; Flynn et al., 2005). Allende area was made by Arellano (1951), who talked Los Corrales stratigraphic sequence is at the top about the Rancho El Ocote horses and some glyptodont of this section in erosional discordance. In it molari- scutes from Rancho Viejo. Later, Mooser (1958, 1959, forms of Nannippus peninsulatus and molars of Equus 1963, 1964, 1973) and Dalquest and Mooser (1980) de- simplicidens were found. One complete osteoderm and scribe the fauna of Rancho El Ocote. They suggest the fragments of other assigned to the pampathere Plaina fauna corresponds only to one age, late Hemphillian, have been recovered. Radiometric dating of the vol- and that is younger than the Yepómera fauna. canic ashes of this layer gave an age of 4.70 ± 0.07 The results of the research done in this basin have by 40Ar/39Ar, and 4.6 ± 0.3 by the fission-track method demonstrated the importance of it. For better under- (Kowallis et al., 1998) (Figure 1).

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 47

Table 1. Faunal list for Hemphillian and Blancan mammalian taxa from central Mexico.

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 48 Carranza-Castañeda

Table 1. Faunal list for Hemphillian and Blancan mammalian taxa from central Mexico (continued).

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 49 Figura 1. Stratigraphic sequence of the Rancho El Ocote area.

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 50 Carranza-Castañeda

It is important to point out that the Hemphillian- vore diversity of the Mexican Hemphillian localities Blancan boundaries in these localities are more reduced (Carranza-Castañeda, 1992; Carranza-Castañeda and than in any other research area. Also, in the upper part Miller, 1996; Miller and Carranza-Castañeda, 1996), of this layer, a Pleistocene sandy clay, brown in color, also the badger Taxidea was collected recently. The covers all the section (Figure 2). horses are abundant, mainly Dinohippus mexicanus, Astrohippus stockii and Neohipparion eurystyle. The Locality GTO 2 Rancho El Ocote Pleistocene radiometric date gave a Hemphillian age (Kowallis et al., 1998). Locality GTO 2B Type section 21°05.28’N, 100°41.01’W Locality GTO 43 Rinconada H Blanco layer latest H 21°03.44’N, 100°47.81’W Rhino layer late H The stratigraphic sequences of the localities from GTO Locality GTO 2 Los Corrales early Blancan 12 La Pantera are in erosional discordance. Here, abundant material of Nannippus peninsulatus has been re- Locality GTO 83 (GTO 2D Plaina) covered, a skull fragment and isolated molars of Equus 21°05.26’N, 100°41.30’W simplicidens as well as undescribed remains of rodents, amphibians and reptiles. The two ash layers present were Los Galvanes Area dated by fission-tracks, giving an age of 3.9 ± 0.3 Ma.

At the base of this sequence is the Rinconada fauna Locality GTO 12 La Pantera A and B early Blancan (locality GTO 43), which bears the largest carni- 21°03.78’N, 100°46.13’W

Figure 2. Stratigraphic sequence of the Los Galvanes area.

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 51

The localities from GTO 4 Arroyo El Tanque correlate In the Comonfort area, distant just 35 km, in the La with GTO 12. On different places of El Tanque, abun- Nopalera locality (Ranchería de Neutla), similar mo- dant fossils of Blancan age have been recovered, such lars to those of Calippus have been recovered. as birds and reptiles, skeletal elements of Hemiauchenia In Rancho Viejo are the localities of GTO 42 blancoensis and Platygonus, molars and mandibles Rancho San Martín, where besides Astrohippus stockii of Nannippus peninsulatus and Rhynchotherium, and Dinohippus mexicanus molars, a skull, a man- Neochoerus cordobai molars and Glossotherium mate- dible and different skeletal elements of Canis ferox rial (Montellano-Ballesteros and Carranza-Castañeda, were collected. This fauna correlates with the one of 1986); the last two represent the first records of South Arroyo Tepalcates (GTO 52), which bears abundant American immigrants integrated with the Holartic fau- material of Astrohippus stockii, Dinohippus mexicanus, nas (Flynn et al., 2005). Machairodus cf. M. coloradensis, Desmathyus brachi- dontus and Megatylopus matthewi. The age of these Locality GTO 4 Arroyo El Tanque localities is late Hemphillian. 21°04.03’N, 100°46.12’W Locality GTO 42 Rancho San Martín late H The basal bed of locality GTO 47 Arroyo Belén cor- 21°01.36’N, 100°46.00’W responds to the same stratigraphic level of GTO 4. Glyptotherium, Neochoerus elements and the most sig- Locality GTO 52 Arroyo Tepalcates late H nificant remains of a pampathere tentatively referred to 21°01.25’N, 100°45.46’W Plaina have been recovered in this locality. They represent the oldest records of South American immigrants The early Blancan locality GTO 11 Garbani is just 800 in North America; the bearing bed has an age of 3.6 ± m to the north of GTO 42; here an age of 4.1 ± 0.5 Ma 0.04 Ma. This sequence is covered by sandy clay with was estimated by a dated volcanic ash (Kowallis et al., Equus sp. molars and remains of the rodent Thomomys 1998). In this locality Nannippus peninsulatus, Equus sp. (Figure 2). simplicidens molariforms and undescribed rodent and bird material are abundant. Locality GTO 47 Arroyo Belén early Blancan 21°04.69’N, 100°46.41’W Locality GTO 11 Garbani early Blancan 21°01.12´N, 100°45.46’W Rancho Viejo Area Three kilometers to the southeast, the localities GTO 5 In the base of this sequence is locality GTO 44 La Miller Place, GTO 33 Pork Chop and GTO 14 Cuesta Presa, where molars of Calippus (Grammohippus) Blanca are located, where the largest amount of the castilli and diverse elements of Dinohippus interpo- capybara Neochoerus cordobai and some elements of latus have been collected. The locality was assigned Glossotherium have been collected. to the earliest late Hemphillian (Carranza-Castañeda and Espinosa-Arrubarrena, 1994). Other localities Locality GTO 14 Cuesta Blanca early Blancan of the same age where these species were recorded 21°01.26’N, 100°45.24’W are GTO 50 La Cancha EW and GTO 69 Arroyo Sorpresa. Locality GTO 6 Arrastracaballos is towards the south of this sequence, which bears the largest Blancan fau- Locality GTO 44 La Presa earliest late H nal diversity of the San Miguel de Allende basin. The 21°00.86’N, 100°47.19’W best collected material are the horses Equus simplicidens and Nannippus peninsulatus, the carnivores Locality GTO 50 La Cancha EW earliest late H Borophagus diversidens, Felis studeri, Pliotaxidea

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 52 Carranza-Castañeda sp., Trigonictis sp., and Canis cf. C. lepophagus, the material have been collected are only 400 m north of artiodactyls Hexobelomeryx fricki, Hemiauchenia this locality (Figure 3). blancoensis, and Platygonus sp. Besides, undescribed rodent material, as well as the lagomorph Hypolagus Coecillos Area (20º59.93’N, 100º46.06’W) vetus come from this locality. Locality GTO 69 Arroyo Sorpresa is situated at Locality GTO 6 Arrastracaballos late H – early Blancan the base of the same sequence, and is of early late 21°00.92’N, 100°45.31’W Hemphillian age. Its fauna is represented by the most complete palate of Dinohippus interpolatus, with both It is important to point out that the Pleistocene lo- P2-M3 series, and a maxillary fragment of a gom- calities where isolated teeth and a partial skull of Equus phothere.

Figure 3. Stratigraphic sequence of the Rancho Viejo area.

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 53

Above these stratigraphic sequences there are dif- sections, the most complete is the one from Rancho ferent sites within the Coecillos area where abundant Viejo area, with representative faunas of the early material has been collected of Dinohippus mexicanus, late Hemphillian, late Hemphillian, early Blancan and Astrohippus stockii, Neohipparion eurystyle, Nannippus Pleistocene. The age of these localities has been con- minor (=N. aztecus), Teleoceras, a Machairodus inci- firmed by radiometric dates of volcanic ashes interca- sor, numerous rodent remains, specially few skulls and lated with the bearing beds. jaws of Paenemarmota, the lagomorphs Notolagus In all four stratigraphic sections there is evi- velox, Hypolagus and the artiodactyls Hemiauchenia, dence of South American immigrants. Without doubt, Texoceros, Hexobelomeryx, Megatylopus and they represent the first fossil evidences that during the Desmathyus. All these collecting sites were named lo- Hemphillian-Blancan boundary the Panamian land cality GTO 30 Coecillos. bridge had an efficient terrestrial corridor, through Recent work in the ravine named GTO 75 Arroyo which the American faunal interchange began (Miller de Emilio (20º59.97N and 100º45.88’W), where a and Carranza-Castañeda, 1999; Carranza-Castañeda diversity of fossils was found, made this locality im- and Miller, 2004). portant. Here were collected a Dinohippus mexicanus skull fragment and mandibles, a complete and articu- HIDALGO STATE lated skeleton of the peccary Desmathyus. Some jaws, a partial skull, an almost complete skeleton, mandibles, Zacualtipán Basin skull and other elements of Paenemarmota, a new in- determinate mustelid, and the badger cf. Taxidea and Accidental fossil findings made by coal miners during the first record of the possible skunk Conepatus, a their work in the Zacualtipán mines, exploited during Hemiauchenia mandible and another jaw of a probable the second half of the xix century, are among the first Texoceros. Undoubtedly, all the material corresponds descriptions of fossil material of the Mexican Miocene. to the Hemphillian. This fossil material without stratigraphic control (Leidy, Pleistocene sediments, in erosional discordance, 1882; Cope, 1885, 1886) is known as the Tehuichila are in the same ravine. In them, an Equus mandible as- fauna. In the first descriptions, the age was assigned sociated with a more or less complete Glyptotherium to the Miocene. Ferrusquía-Villafranca (1978), in the cf. G. floridanus carapace, including the mandible of revision of the Miocene faunas, established their age the same individual, were collected. In the same area, as Pliocene. the locality GTO 36 Palma Sola has a similar stratig- During the research carried out in the 1990’s, raphy; Astrohippus molars have been collected in the sponsored by the Universidad Autónoma del Estado basal Hemphillian sediments, and molars of Equus sp. de Hidalgo, a new locality, HGO 2 Potrero de Zietla, in the Pleistocene ones. 20º36.40’N, 98°36.25’W, was discovered. The fauna Recently, Blancan fossils were recovered in the consists of Dinohippus interpolatus and Calippus locality GTO 79 La Perdida, consisting of isolated (Grammohippus) castilli upper molars, molar fragments molars of Nannippus peninsulatus. This shows that in of Agriotherium and Teleoceras?, a Hexobelomeryx the Coecillos area there is a complete stratigraphic se- molar and calcaneum and molar fragments of cf. quence from early late Hemphillian, late Hemphillian, Prosthennops. This fauna correlates with the one from Blancan to Pleistocene. the San Miguel de Allende basin, GTO 44 La Presa, assigned to the early late Hemphillian (Carranza- Discussion Castañeda and Espinosa-Arrubarrena, 1994). The revision of the equid fauna from Tehuichila The most complete stratigraphic sequences known at (MacFadden, 1984; Carranza-Castañeda and Espinosa- present in Mexico and probably in North America oc- Arrubarrena, op. cit.) showed that in this basin two cur in the San Miguel de Allende basin. Of the four mammal ages exist: late Hemphillian (late Miocene),

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 54 Carranza-Castañeda represented by the fauna of Potrero de Zietla, and early Equus sp. upper molars were collected. The presence Blancan (early Pliocene), by the presence of Nannippus of this genus indicates a Pleistocene age. peninsulatus. In the Tula area, locality HGO 24 El Bagre, fish remains of the genera Ictiobus (Alvarado-Ortega and Actopan-Ixmiquilpan Basin Carranza-Castañeda, 2002a, 2002b; Alvarado-Ortega et al., in press) and Ictalurus have been recovered in This is one of the largest ancient paleolakes in cen- Blancan age beds. Also, in surrounding sites there are tral Mexico. The fluvio-lacustrine sediments extend fish fossils that now are under study. Other important by thousands of square kilometers, and the thickness localities are HGO 21 Los Fragmentos and HGO 22 in some areas is more than 100 m, covered by early Los Tepalcates, where Nannippus peninsulatus materi- Pleistocene volcaniclastic sediments. al, proboscidean fragments possibly of Rhynchotherium At several sites in the surrounding of the and Platygonus molariforms have been recovered Lagunillas village, unidentified mammalian fossil frag- (Figure 4). ments have been collected. In the locality HGO 7 La Locality HGO 25 La Plegaria is southwest of Tepeji Suerte, 10º51.35’N and 99º01.36’W, a lower molar del Río city. Its fauna is represented by Astrohippus fragment of Rhynchotherium and molar fragments of stocki, Neohipparion eurystyle, Dinohippus mexica- unidentified equids were recovered. nus, Machairodus cf. M. coloradensis, Canis ferox, In the ravine Bodandha of the Ixmiquilpan re- Megalonyx, Teleoceras fossiger, cf. Megatylopus mat- gion (20°24.22’N, 99°14.56’W), just 2 km south of the thewi, Hemiauchenia vera, Alforjas sp., Hexobelomeryx ranchería de Xothi, the locality HGO 27 Las Arcinas was fricki and cf. Texoceros sp., of late Hemphillian age. discovered. Its fauna consists of upper molar fragments It correlates with the faunas of Rinconada, Arroyo of Nannippus peninsulatus, Equus cf. simplicidens and Tepalcates and Rancho El Ocote, from Guanajuato Platygonus, which are Blancan fossil indexes. State (Padilla-Gutiérrez, 2004). In the Santa María Amajac region, 20º18.27’N, 98º42.50’W, there is a sequence of clay, sandy clay and JALISCO STATE gravel which bears fossils. The ash that is at the base of this sequence was dated, giving an age of 4.2 ± 0.3 Large sedimentary basins occur in this state. The up- Ma by fission-tracks, and of 4.57 ± 0.02 Ma by 40Ar/ dated results of the prospecting work are given accord- 39Ar, which indicates an early Blancan age. The col- ing to the regions where these basins are located. lected fauna includes Equus simplicidens, Nannippus peninsulatus and Rhynchotherium fragments. These Tecolotlán Basin fossils reinforce the early Blancan age assignment. In the upper strata, a Tremarctus maxilla was recovered. During the last years an extensive investigation was Sediments that bear fragments of the rhino Teleoceras, carried out in this area, located 100 km southwest of a Hemphillian index fossil, are found to the west of Guadalajara city. The stratigraphy of the basin is com- these localities. The sequence has just been preliminary posed of two sedimentary sequences; the lower was de- explored (Carranza-Castañeda and Miller, 1998). termined as late Hemphillian because of the associated fauna and 40Ar/39Ar ash dating, which yielded an age Tepeji del Río-Tula Basin of 4.89 ± 0.016 Ma, and the upper, Buenaventura, assigned to the late Blancan also by its faunal content and The Tepeji del Río area, in the southwestern region of the ash dating that gave an age of 2.6 Ma. the Hidalgo State, is where the lacustrine sequence is The Hemphillian sequence consists of three sec- best exposed, with a thickness of more than 100 m in tions. The lower, named JAL TECO 9 Santa María, is some sites. This sequence is covered by volcaniclastic composed of red oxidized clay and sandy clay, as well sediments of the locality HGO 20 Tacos y Tortas, where as gravels that represent paleochannels. The abundance

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 55

Figure 4. Main basins in central Mexico. of Nannippus minor (=N. aztecus) is notable; it exceeds Unconformably, the sequence of gravel and fine- any locality from central Mexico, including the locali- grained sand, whose radiometric date gave an age of ties from Guanajuato. In contrast with other Mexican 2.6 Ma, allows to situate it in the late Blancan. From Hemphillian localities, in this layer few specimens of this sequence, in the locality JAL TECO 7 Las Gravas, Astrohippus stockii have been collected. The sequence equid molars were found with less progressive char- is interrupted by lacustrine sediments that crop out in acters than those of Equus simplicidens, besides almost all the southwestern part of the basin and cover Platygonus, Hemiauchenia blancoensis. this sequence; they do not have fossil mammals, but in In JAL TECO 44 Las Placas and the most impor- the upper bed some crystallized gastropods have been tant locality JAL TECO 53 Lic. Preciado, proboscidean recorded. tusks, horse teeth fragments and the noteworthy South Covering these lacustrine sediments, the upper American immigrants Glyptotherium, Neochoerus section consists of clay bed sequences named JAL and pampathere remains of cf. Plaina have been re- TECO 20 La Hacienda, JAL TECO 26 Kowallis, where covered. It is important to note that all along the se- the ash gave an age of 4.89 ± 0.16 Ma by the 40Ar/39Ar quence there are fossils of crocodilian and turtle mate- method. In this stratigraphic level, numerous micro ver- rial, but no remains of Nannippus peninsulatus were tebrate remains have been collected, such as rodents, observed (Kowallis et al., 1998, 2003, in press; Miller lagomorphs, amphibians, reptiles and birds, which have and Carranza-Castañeda, 1998a, 1998b, 1999, 2001a, not yet been described. It is interesting to point out that 2001b; Carranza-Castañeda, 2002; Carranza-Castañeda Astrohippus stocki is very rare in this part of the section et al., 2002) (Figure 5). The known fauna is listed in and Nannippus minor has never been collected. Table 1.

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 56 Carranza-Castañeda

Figure 5. Composite stratigraphic sequence of the Tecolotlán Basin.

Colotlán-Tlaltenango Basin Santo Domingo is found, where also the late Hemphillian equids Nannippus minor, Neohipparion eurystyle and The locality JAL COLO 17 Los Vélez is located eight ki- Astrohippus stockii were recorded. In the locality JAL lometers south of Colotlán city. Here the Neohipparion COLO 9 Los Corrales (= ZAC JUCH 9 Sanidad Animal, eurystyle, Astrohippus stockii and Desmathyus fos- 21º57.56´N, 103º18.27´W), molars of Dinohippus inter- sils have been collected; these taxa establish a late polatus and Calippus cf. C. castilli have been recovered, Hemphillian age. which represent the earliest part of the late Hemphillian. In the state border of Jalisco and Zacatecas, just It is important to point out that these equid species rep- 3 km south of Los Vélez locality, the locality ZAC 18 resent the oldest horses in central Mexico.

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 57

Teocaltiche-Xalostitlán Basin QUERÉTARO STATE

In different places located between these two cities, There have been several reports of Pleistocene fossils different specimens were collected. In the Teocaltiche from different places in this state. The only locality with area, Osteoborus cyonoides (=Borophagus secundus), late Tertiary fossils is QRO 1 Landa de Matamoros, Astrohippus stockii, Dinohippus mexicanus and cf. which is in the Sierra Gorda of Querétaro. The recov- Hexobelomeryx fricki fossils were found. This fauna is ered fossils include a gomphothere mandible and max- of late Hemphillian age (Montellano-Ballesteros, 1997; illa, a Nannippus minor lower molar and an astragalus Aguirre-Díaz and Carranza-Castañeda, 2001). of a possible Hexobelomeryx. The fauna was assigned In recent field work carried out by the author, a new to the late Hemphillian. locality was discovered, JAL TEO 2 El Libramiento, that allowed to recover an equid upper molar with NAYARIT STATE close characters to those of Calippus, a carnivore tibia, a second molar of probable gomphothere and bird re- In the 1960’s, Dr. Theodore Downs and Harley J. mains. The age of this fauna is the earliest part of the Garbani collected material from the locality Valle de late Hemphillian. Los Gigantes that is now housed in Los Angeles County Natural History Museum; the locality is recorded in MICHOACÁN STATE Centro de Geociencias, UNAM as NAY 1.

Late Tertiary localities from the Michoacán State are Los Gigantes Basin (21º27.69´N, 104º04.70´W) very scarce, but there are several reports of Pleistocene fossils. This fauna has not been described, but a preliminary study of the present author allowed to identify Dinohippus Charo Depression mexicanus, Neohipparion eurystyle, Agriotherium, Megalonyx, Rhynchotherium, Megatylopus, and a felid, The town of Charo is located 14 km south of Morelia probably Machairodus. During the spring field work of city. In the locality MICH 1 Rancho La Goleta is found 2005, a lower molar of Dinohippus and turtle (probably the only late Tertiary fauna. It has been mentioned Geochelone) carapace fragments were collected. The since the second half of the past century, but the age associated fauna suggests a late Hemphillian age. assignment always was ambiguous (Reppening, 1962; As part of the recent prospecting work, two new Howard, 1965; Ferrusquía-Villafranca, 1978). New late Hemphillian localities were discovered in the top investigations carried out with UNAM’s support, al- of the southwestern Sierra Madre. The most interest- lowed to prospect the area and to collect early Blancan ing one is found in the Huajimic basin, where some fossils (Carranza-Castañeda, 1976). Besides, there are fossils were collected. This locality was named as abundant unpublished rodent remains. The radiomet- NAY 2 El Huichol, and Dinohippus mexicanus and ric date gave an age of 3.6 Ma. Unconformably, late Rhynchotherium fossils were identified. Pleistocene sediments with Equus sp. molars cover the It is important to note that in all these localities vol- Blancan sediments. canic ash is intercalated with the bearing beds (Figure 4). The locality MICH 2 Cinqua, 19°45.43’N, 100°14’32”W, was discovered 160 km southeast ZACATECAS STATE of Morelia city. Its associated fauna consists of Neohipparion eurystyle, Dinohippus interpolatus (?), Juchipila-Jalpan-Tabasco Basin Teleoceras fossiger, Desmathyus and Megatylopus cf. M. matthewii, with an age corresponding to the earliest This is a large geologic structure about 120 km long late Hemphillian (Figure 4). with a NE orientation, where lacustrine sediments have

Carranza-Castañeda, Óscar, and Lindsay, E.H. eds., Advances in late Tertiary vertebrate paleontology in Mexico 2006 58 Carranza-Castañeda a thickness greater than 70 m, and in some areas the CONCLUSIONS clay sediments bear abundant root traces and other evidences of fossil plants, such as in locality ZAC JUCH The carried out research of the continental late Tertiary 29 Raíces, in the ranchería of Mezquituta. In other basins of central Mexico has shown the importance areas only the lacustrine sediments with ostracodes of this region due to the abundance of fossils and the crop out, as in localities ZAC JUCH 24 La Cofradía faunal diversity. The faunal associations represent two (21º37.53’N, 103º01.85´W) and ZAC JUCH 27 La mammal ages: late Hemphillian (late Miocene) and Chimenea (21º27.25’N, 103º05.54W). Blancan (Pliocene), although Pleistocene mammals are Along this basin, several localities with fos- also present. In some basins, the superposition of late sil mammals have been discovered. Among the most Hemphillian-Blancan faunas has demonstrated that the important is locality ZAC JUCH 30 Las Lomas del San Miguel de Allende and Tecolotlán basins are the Valle, where upper molars of a possible Calippus and most complete stratigraphic late Tertiary continental antilocaprid molars were collected; this large area sequences in Mexico. This superposition opens the pos- with exposed sediments has diverse fossil mammals. sibilities of studying the extinctions that occurred in the In the locality ZAC JUCH 25 Arroyo Los Fragmentos, boundary between the mammal ages. Also, the abun- Dinohippus mexicanus molars and a tibia, and dance of rodent fossils, of which most part has not been Astrohippus stockii molars were recovered; the abun- described, constitutes an opportunity to study different dance of fragments also suggests a diverse fauna. Other biological events, such as the evolution of cricetid ro- localities are ZAC JUCH 22 Camino de Piedra and dents, which are common in these basins. Collaterally, ZAC JUCH 23 El Pájaro (21º37.53´N, 103º01.85´W), the boundaries of large lakes that were present in cen- where bird elements, specially coracoids and an upper tral Mexico during late Tertiary have been defined. molar probably of Dinohippus were recovered. The continuity of researching in basins of Mexico To the north of Jalpan city are localities ZAC will contribute to precise the migrating routes of the JUCH 28 La Canica, where a Neohipparion eurystyle first South American immigrants from the early Blancan molar and other fragments were collected, and locality faunas of central Mexico to the late Blancan faunas of ZAC HUAN 5 Yerbaniz, with fragments of a possible Texas, Arizona, New Mexico and Florida. Rhynchotherium. Locality ZAC HUAN 6 Hilda, with Equus sp. upper molars, is north of Tabasco city, where ACKNOWLEDGMENTS only Pleistocene sediments crop out (Aguirre-Díaz and Carranza-Castañeda, 2000; Carranza-Castañeda and The research of the sedimentary basins from cen- Aguirre-Díaz, 2000, 2001). tral Mexico began with the support of the Instituto de Geología, UNAM, and continues with that of the BAJA CALIFORNIA SUR Centro de Geociencias, UNAM, Campus Juriquilla, Querétaro. Mr. Harley J. Garbani, since the beginning, In the southern part of the Baja California Peninsula, has been working in the San Miguel de Allende Basin. the late Tertiary Las Tunas fauna was for several years I am very grateful to Dr. Wade Miller and Dr. Bart the only extensively described fauna (Miller, 1980). Kowallis, from Brigham Young University; their sup- Prospecting work done north of San José del Cabo al- port and participation in the research have been signifi- lowed to recover Blancan fossil mammals. This area is cant in the success of the results here presented. In the being systematically worked now, and abundant Equus last years, Miss Hilda Troncoso has been prospecting simplicidens, Rhynchotherium, a canid material, a Felis and collecting. I want to express my special thanks for lacustris partial jaw, and lagomorphs, rodents and bird their financial support to the investigations to the fol- specimens have been collected (Carranza-Castañeda lowing institutions: Centro de Geociencias, Campus and Miller, 1999; Miller and Carranza-Castañeda, UNAM, Juriquilla; National Geographic (Grant 3443- 2001a, 2001b, 2002). 86); CONACYT (Project 1466 and Project 47071);

Universidad Nacional Autónoma de México, Instituto de Geología and Centro de Geociencias Publicación Especial 4 Late Tertiary fossil localities in central Mexico, between 19°–23°N 59

National Science Foundation (Grants EAR 8620155, tardío en el centro de México: Unión Geofísica Mexicana, EAR 9316895, and EAR 9902898), and The Earth Resúmenes y Programa, Reunión Anual 2000, Geos, v. 20, Watch Institute. no. 3, p. 301 (abstract). ――― 2001, Índices bioestratigráficos de las cuencas sedimentarias Finally, I acknowledge Luis Burgos and Fernando del Terciario tardío del centro de México: Unión Geofísica Vega for drawing the illustrations. Also, I thank all par- Mexicana, Resúmenes y Programa, Reunión Anual 2001, ticipants during the field work, Gerardo Álvarez-Reyes, Geos, v. 21, no. 3, p. 206 (abstract). students and researchers, which have collaborated in Carranza-Castañeda, Óscar, and Espinosa-Arrubarrena, Luis, 1994, different phases of the studies of central Mexico. Late Tertiary Equids from the State of Hidalgo, Mexico: Universidad Nacional Autónoma de México, Instituto de Geología, Revista, v. 11, p. 182–192. 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