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MPGJ 1970, Neohipparion eurystyle, left and right maxilla fragments, dP2-P4 in early wear. Locality ZJ 30 Mixtón, Juchipila, Zacatecas.
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... Neogene and Quaternary fossil mammals are better known. Their early and middle Miocene records include localities in northern (Sonora, Baja California, and Baja California Sur), central (Aguascalientes), and southern Mexico (Oaxaca and Chiapas); late Miocene and Pliocene mammals are known from northern (Baja California Sur, Chihuahua, and Sonora), central (Guanajuato, Hidalgo, Jalisco, Michoacán, Nayarit, Querétaro, Tlaxcala, and Zacatecas), and southeastern Mexico (Chiapas); and Pleistocene mammals have been recorded in many localities all along Mexico (Arroyo-Cabrales et al. 2005;Montellano-Ballesteros and Jiménez-Hidalgo 2006;Carranza-Castañeda 2006, 2019Carranza-Castañeda et al. 2013;Bravo-Cuevas and Jiménez-Hidalgo 2018;Gómez-Pérez and Carbot-Chanona 2018;Carbot-Chanona 2021;Carranza-Castañeda and Jiménez-Hidalgo 2021). ...
Mammals can be defined as the least inclusive clade containing Ornithorhynchus anatinus (Shaw in Nat Miscellany 10(118):7, 1799) and Homo sapiens Linnaeus, 1758. Mexico is the third country with the highest mammalian species richness in the world. Their fossil record in this megadiverse country spans from the Early Jurassic to the Late Pleistocene. Research of fossil mammals have been centered on taxonomy and until recently, some paleoecological and paleoenvironmental reconstructions have been published. In this chapter, some of the techniques of paleoenvironmental reconstruction based on fossil mammals are described (microwear, mesowear, stable isotope analysis, bioclimatic models, ecometric analyses, and mutual ecogeographic range) and some examples of their use with the Mexican record are provided. The extensive fossil record available for some geological epochs makes the Mexican mammals a rich source of paleoenvironmental data that needs to be further explored.
... The continuous research in the Juchipila basin, state of Zacatecas, has demonstrated these southern mammalian movements in early Hemphillian age in central Mexico, with its importance and diversity of mammals contained in the sedimentary sequence described in previous works (Carranza-Castañeda et al., 2013;Tseng et al., 2017;Carranza-Castañeda, 2022;Carranza-Castañeda et al., 2022). This work presents the latest discovery, a humerus, the only complete element known in the early Hemphillian deposits that has been referred to Agriotherium, in deposits dated to 6.35±0.38 ...
... The stratigraphy of the Juchipila basin has been logged by Aranda-Gómez (described in Carranza-Castañeda et al., 2013), in selected areas where the greatest diversity and number of fossil mammals from the early Hemphillian have been recovered. ...
... The most important localities of this stratigraphic sequence are: El Resbalón (Zac Juch 47), La Copa (Zac Juch 48) and El Epazote (Zac Juch 51), due to the diversity of recovered mammals: Sphenophalos, Gomphotherium hondurensis, Neohipparion trampanense, Dinohippus interpolatus, Calippus hondurensis, Enhydritherium terranovae, Alforjas taylori, Megalonichid? Teeth (Carranza-Castañeda et al., 2013;Tseng et al., 2017). Recently, in El Resbalón locality, we collected the southernmost record of Agriotherium of the early-late Hemphillian age known outside of the USA faunas. ...
A complete humerus referred to Agriotherium is described, collected from early-late Hemphillian deposits from Zacatecas. Agriotherium is widely represented by isolated molars, mandibles, and maxillae in early-late Hemphillian faunas of Eurasia and North America. In the literature, postcranial elements are scarce and briefly described with little detail. The greatest diversity is known from the Langebaanweg quarry in South Africa; however, the only complete specimen is from Mexico. The proximal end is described, and the humerus shares similarities with the description of the distal end from South Africa, in which the medial epicondyle and crest of the lateral epicondyle are reduced, which can be considered as a limitation in the hunting of larger prey for food. This implies that Agriotherium was not strictly carnivorous but was a predator-scavenger with an omnivorous diet that included plants and fruits.
... Horses were an important component of North American mammalian faunas during the Cenozoic, particularly from the late Neogene and Quaternary geological periods (MacFadden, 1988(MacFadden, , 1992Priego-Vargas et al., 2016). The fossil record of Mexican horses spanned from the early Eocene to the late Pleistocene (Novacek et al., 1991;Arroyo-Cabrales et al., 2005;Carranza-Castañeda et al., 2013;Jiménez-Hidalgo et al., 2019). Based on the known Mexican record, major species diversity is observed during the early middle Miocene (ca. ...
... The small-sized hipparionine Nannippus peninsulatus and the medium-sized primitive equine Equus simplicidens are typical species of the Mexican Pliocene (Priego-Vargas et al., 2016;Bravo-Cuevas and Jiménez-Hidalgo, 2019). These horses are known by cranial, dental, and postcranial remains recovered from several localities in northern and central Mexico (Lance, 1950;Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013;Bravo-Cuevas and Jiménez-Hidalgo, 2019). It is worth noting that both species were biochronological elements of the Blancan faunas from the southern United States and Mexico (Lance, 1950;Miller and Carranza-Castañeda, 1984;Carranza-Castañeda and Espinosa-Arrubarena, 1994;Morgan and White, 2005;Morgan et al., 2008Morgan et al., , 2011Morgan and Harris, 2015). ...
... In Mexico, these species have been reported from several Blancan localities in northern and central Mexico, including the states of Chihuahua, Michoacán, and Guanajuato (Lindsay, 1984;Carranza-Castañeda, 2006). The chronological information of the majority of these sites is from the biochronological correlation with other North American faunas from the southern United States (Lindsay, 1984;Carranza-Castañeda and Miller, 2004;Carranza-Castañeda et al., 2013). However, there is radiometric information for some localities in San Miguel de Allende, Guanajuato (La Pantera: 3.9 ± 0.3 Ma) and Charo, Michoacán (La Goleta: 3.6 ± 0.3 Ma), whose ages are related to the Blancan III (Carranza-Castañeda, 2006;Ferrusquía-Villafranca and Ruiz-González, 2015). ...
We describe a set of dental and postcranial horse material recovered from the locality Los Hornitos, northeastern Sonora, northwestern Mexico. The fossil-bearing unit consists of brown silt with intercalation of fine-grained sandstone and bioturbated incipient soils, set in an alluvial environment and considered Pliocene in age. The comparative study of the available sample indicates the presence of two species: the small-sized hipparionine Nannippus peninsulatus and the medium-sized and primitive equine Equus simplicidens. The isotope composition of δ¹³C and δ¹⁸O in dental enamel tooth indicates a C3–C4 mixed diet for these species and suggests the presence of woodland and open areas in Los Hornitos during the Pliocene. The less negative δ¹³C values observed in E. simplicidens are related to a more C4 diet, preferring to roam open habitats. The coexistence and optimal resource partitioning between these species are explained, considering their differences in dietary behavior, body size, home range, and/or vagility. The recognized horse species are typical of the Blancan North American Land Mammal Age, and their biochronological information from the southwestern United States and central Mexico establishes the probable age of the Los Hornitos at about 3.9–2.6 Ma, corresponding to the Blancan III or late early Blancan – early late Blancan.
... In the same locality Rodríguez-de la Rosa and Guzmán-Gutiérrez (2012) and Astrohippus, as well as an indeterminate gomphothere. Later, Carranza-Castañeda et al. (2013) assigned the fossil remains of Teocaltiche to two Hemphillian time intervals: the material previously reported by Montellano-Ballesteros (1997) to Hh3 and a fragment of the palate of Calippus hondurensis, found by them, to Hh2. The locality of this discovery is reported in the same work as Jalostotitlán; however, the GPS coordinates of the same site provided by González-Cervantes et al. (2019) place the fossil site in the municipality of Teocaltiche. ...
... Subsequently, several publications have suggested the presence of Rhynchotherium in the Tecolotlán basin, but without reference specimens to corroborate it (e.g. Carranza-Castañeda et al., 2013;Kowallis, 2017;McDonald and Carranza-Castañeda, 2017); Recently, Carranza-Castañeda (2018) figured a couple of isolated tusks collected in Tecolotlán, that could be assigned to the taxon, but he did not find any enamel bands that confirm such a determination. This is the first work where substantial evidence demonstrates the presence of Rhynchotherium falconeri in Jalisco. ...
... The lower jaws were later the subject of a cover illustration in Carranza-Castañeda and Lindsay (2006). In the same volume, Carranza-Castañeda (2006: Fig. 2) placed the GTO 43 in the latest Hemphillian, as also did Carranza-Castañeda et al. (2013). Hodnett (2010) remarked that the Guanajuato jaws are similar to Megantereon, but overall, the Mexican form is more closely related to Homotherium. ...
... Our selection of European records is not exhaustive, and the apparent gaps do not necessarily indicate the absence of Amphimachairodus. Chronological relationships of central Mexican localities and subdivision of Hemphillian NALMa are based on Carranza-Castañeda et al. (2013). Magnetic correlation of the Arroyo de las Burras section in Yepómera Basin is based on Lindsay et al. (2006). ...
The charismatic sabretooth cat Amphimachairodus has numerous but largely fragmentary records across late Miocene deposits of Africa, Eurasia and North America. The genus has a complex taxonomic history, and the majority of Amphimachairodus materials come from isolated localities, often studied without stratigraphic context. Here, we analyse the long, continuous records from the classic Chinese Baode strata, which produce Amphimachairodus throughout the section, and demonstrate that an A. palanderi-horribilis chronospecies succession represents a continuum of in situ anagenetic evolution of increasing size. We then synthesise chronological occurrences of Amphimachairodus from all Holarctic records and reframe their evolution as a case of chronospecies succession. Two parallel anagenetic lineages are evident: a Eurasian A. giganteus-palanderi-horribilis chronospecies succession and second, a North American A. coloradensis-alvarezi chronospecies succession following an immigration event in the early Hemphillian. In addition to greater hypercarnivory evidenced by dental specialisation, the Eurasian lineage shows a trend towards a large body size, whereas the North American lineage decreases in size. We take this opportunity to describe materials of Amphimachairodus alvarezi from Yepómera (latest Hemphillian) in the state of Chihuahua, Mexico, and previously undescribed materials from San Miguel de Allende Basin. We review taxonomic status of Chinese A. horribilis and related taxa.
... Plioceros sp., and cf. Sphenophalos sp., were recorded in the Hh2 of the Juchipila Local Fauna, Zacatecas state, and the Hh4 of Jalisco state (Tecolotlán and Teocaltiche local faunas) (Montellano-Ballesteros, 1997;Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013); and Merycodus sp. was reported from the Hh2 (a U-Pb zircon age of 6.77 ± 0.21 Ma is available) of Palmillas Local Fauna in Guanajuato (Robles--Rivera, 2015). ...
... Previous studies established the biochronology of the late Miocene-Pliocene fossil localities from San Miguel de Allende, which spans from Hh 2 to Blancan III North American Land Mammal Ages (see Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013;Carranza-Castañeda, 2019;Jiménez-Hidalgo and Carranza-Castañeda, 2011, and references therein). ...
... Studied specimens were collected through surface pick-up from the following Hemphillian localities: GTO 2B Rancho El Ocote (Hh 4) (White layer; Carranza-Castañeda et al., 2013), GTO 30 Coecillos (Hh 3), GTO 43 Rinconada (Hh 3), GTO 48 La Chiva 2 (Hh 3) (Fig. 1). Three of these localities have been radiometrically dated; fission-track ages of 4.4 ± 03 Ma for GTO 43, and of 4.8 ± 0.2 Ma for GTO 2B are available, whilst the ashy material that underlies the fossiliferous bed of GTO 30 was dated as 5.32 ± 0.34 Ma (Flynn et al., 2005;Carranza-Castañeda, 2019). ...
The pronghorns Texoceros altidens, Subantilocapra garciae and a new specimen of Hexobelomeryx fricki are described. Fossil material was collected from Zanclean age sediments of the informal Rancho Viejo Beds of the San Miguel de Allende Graben, state of Guanajuato, in central Mexico. Analysis of teeth measurements of the four Texoceros species from North America revealed that they cannot be objectively identified, thus, they were synonymized with Texoceros altidens, which has priority. A mesowear analysis of the San Miguel de Allende teeth specimens showed that their mesowear scores are most similar to mixed-feeder and browser ruminants. A discriminant function analysis classified most of the Pliocene pronghorns from Guanajuato as mixed-feeders. Given the occurrence of Texoceros and Subantilocapra in the Hh3 of central Mexico, it is likely that the early evolution of the Recent pronghorn took place in central Mexico. The identified antilocaprid species from San Miguel de Allende, Guanajuato are the most southern records of Pliocene age in North America. (Free download for some time: https://authors.elsevier.com/a/1doxy_KNqlfF11).
... The fill of these tectonic depressions is well documented in the Juchipila graben, where it was deposited nonconformably on rocks of the upper volcanic supergroup (Lopez, 1991) and is of late Miocene-Pliocene age, no older than 6.95 Ma (Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013). The master faults as well as lesser faults within the graben displace rocks of the upper volcanic supergroup against the graben fill (Lopez, 1991;Spinnler et al., 2000;Ferrari, Castillo-Reynoso, et al., 2018). ...
... Lacustrine sediments, >40 m thick, are overlain by the deposits of large alluvial fans (Fig. 2) and are normalfaulted in numerous localities (Scheubel, 1983, p. 74). By analogy with the fill of the nearby Tlaltenango and Juchipila grabens (Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013), these lake beds are likely to be of late Miocene-Pliocene age. The lack of lacustrine sediments younger than early Pliocene can be explained by the subsequent integration of this previously closed basin into the drainage network of the Río Grande de Santiago River and related river incision and fluvial erosion. ...
The continental part of west-central Mexico is characterized by the active extensional tectonic regimes of the Trans-Mexican volcanic belt and the adjacent southern Basin and Range Province. The deformation of the latter is distributed over several topographically very pronounced grabens and half-grabens (width 10–20 km, length ≤200 km; throw 1–2 km), including the Aguascalientes, Juchipila, Tlaltenango, and Bolaños grabens. Here, an A.D. 1774–1775 earthquake series in that area is documented based on numerous contemporary sources. The 6 November 1774 mainshock caused moderate-to-severe damage in several communities of the Bolaños graben, including the silver mining town of Bolaños, and moderate damage to communities in the Tlaltenango graben, such as the administrative center of Colotlán. Based on the macroseismic intensity distribution, the epicenter was in the Bolaños graben. The preferred magnitude of the mainshock is ∼6.0±0.5. No major historical earthquake had been reported previously from this region. Existing ground-shaking hazard models may, therefore, give a false sense of security.
In the Bolaños graben, motion along the graben-bounding faults and the observed tilting of the graben shoulders has to be mostly younger than the 19.9 Ma age of the youngest basalt of the graben-shoulder stratigraphy. Its correlation across the western master fault indicates a 1300 m throw and a vertical long-term slip rate of 0.07 mm/yr. The observations of alluvial fan deposits juxtaposed against the footwall ignimbrites along the western master fault of the Bolaños graben, the displacement of alluvial fan deposits along secondary faults within the graben, and the existence of hot springs along the western boundary fault all are indicative of active deformation, and so is evidently the A.D. 1774 earthquake.
... Al occidente del área de estudio se localiza la cuenca de Juchipila (Figura 1b: CJ), donde se ha reconocido una secuencia sedimentaria similar a la estudiada en este trabajo. Estudios de campo de la estratigrafía de algunas secciones (López, 1991, Carranza-Castañeda et al., 2013 y petrografía de muestras sedimentarias colectadas en ellas (Lahiere, 1982y López, 1991 han permitido identificar diferentes asociaciones de facies de ambientes lacustre, fluvial, de llanura de inundación y de abanico aluvial intercaladas de manera compleja. En ese relleno de graben son comunes las capas de ceniza volcánica intercaladas con otros sedimentos. ...
... A esa secuencia sedimentaria se le dio el nombre informal de formación Juchipila (Lahiere, 1982) haciéndose notar que el contacto entre la formación Juchipila y los depósitos volcánicos del Complejo Volcánico Superior de la SMOc es una inconformidad estratigráfica. Fósiles de vertebrados colectados en la formación Juchipila indican que esta incluye sedimentos con edades del Henfiliano temprano (~6.8 -4.75 Ma), mientras que edades de circones recuperados de capas de ceniza volcánica intercaladas con los sedimentos oscilan entre 6.95 y 5.59 Ma (Carranza-Castañeda et al., 2013). En los trabajos de Lahiere (1982) y de López (1991) también se señaló que la distribución vertical de litofacies en la secuencia sedimentaria está influenciada, principalmente, por cambios tectónicos contemporáneos a la sedimentación y, en menor grado, por ciclos climáticos. ...
... Una conclusión importante de López (1991) es que al comparar la fauna de ostrácodos encontrada en sedimentos del paleolago Juchipila con ostrácodos de sistemas lacustres modernos se puede inferir que el paleolago era perenne, de cuenca abierta y se desarrolló en un clima cálido subtropical. Por otro lado, la gran diversidad de mamíferos fósiles hasta ahora colectados en la formación Juchipila es consistente con un ambiente comparable con una sabana abierta (Carranza-Castañeda et al., 2013). ...
En la región ubicada al este de la parte sudoriental de la Sierra Madre Occidental (SMOc) existió un lago extenso durante parte del Oligoceno y casi todo el Mioceno. El lago se formó en una depresión tectónica, asociada con el graben de Aguascalientes y el semigraben de Teocaltiche. Los sedimentos que rellenaron parcialmente esta cuenca continental incluyen sedimentos epiclásticos derivados de las rocas de la SMOc y de la Mesa Central, precipitados químicos y bioquímicos (caliza de agua dulce) y sedimentos mixtos, así como una proporción pequeña, pero generalizada, de capas de ceniza volcánica de caída, que fueron empleadas para obtener edades de U-Pb en circón. El alcance temporal del relleno de la cuenca es amplio, pues abarca desde el Rupeliano (~28.6 Ma) hasta el Tortoniano (~7.6 Ma). Previamente, con base en fauna fósil se creía que la sucesión era solo del Mioceno tardío.
En la parte sur de la SMOc hay varias cuencas de origen tectónico, con orientación NNE, que contuvieron lagos. En al menos tres de ellas (Tlaltenango, Juchipila y Teocaltiche) se sabe, por el carácter de los sedimentos y por sus fósiles del Henfiliano temprano, que hubo lagos de manera simultánea. En el graben de Bolaños, al oeste y paralelo a la cuenca de Tlaltenango, se ha propuesto la existencia de un lago durante el Neógeno, cuyos sedimentos están casi completamente erosionados, por lo que se sabe poco acerca de ellos. Para explicar el bloqueo parcial y simultáneo de los sistemas de drenaje se requiere de una causa común de carácter regional. Las cuatro cuencas tectónicas mencionadas terminan al norte de las depresiones asociadas a los rifts Tepic-Zacoalco o Tula-Chapala. El ajuste isostático en los bloques de piso de estos rifts pudo causar el cierre parcial de los ríos axiales en los grábenes con rumbos NNE y atrapar así los sedimentos. Aunque se desconoce con precisión cuando las cuencas dejaron de ser sistemas acumulativos, se cree, por la ausencia de fósiles del Blancano, que la apertura pudo suceder antes de ~4.75 Ma, valor numérico del inicio de esa etapa faunística. Una causa común probable de la apertura puede ser la invasión marina de una depresión en lo que actualmente es el Golfo de California. La creación de este nuevo nivel base de erosión pudo aumentar considerablemente el gradiente hidráulico en los sistemas fluviales, proveyendo la energía suficiente para remontar al levantamiento asociado a la actividad de los rifts.
An extensive lake existed during part of the Oligocene and almost all the Miocene in the region located east of the southern end of the Sierra Madre Occidental (SMOc). The lake was formed in a tectonic depression associated with the Aguascalientes graben and the Teocaltiche half-graben. Sediments accumulated inside this continental basin are epiclastic, mainly derived from volcanic rocks of the SMOc, and from the volcanic cover of the Mesa Central, chemical and biochemical precipitates (fresh water limestone), and mixed sediments, as well as far less voluminous, but ubiquitous, volcanic ash-fall layers, which were used to obtain U-Pb ages from zircons. The age range of the basin-fill sediments is broad, varying from Rupelian (~28.6 Ma) to Tortonian (~7.6 Ma). Previously, on the basis of fossil fauna, the succession was considered only as late Miocene in age.
The southern end of the SMOc includes several NNE-trending basins of tectonic origin that contained lakes. Based on the characteristics of the individual sedimentary successions, and on their fossil faunas, it is known that three of these basins (Tlaltenango, Juchipila and Teocaltiche) had lakes at the same time. The fourth basin, the Bolaños graben, located west and parallel to the Tlaltenango basin, probably also had a lake during the Neogene, but almost all its sediments have been eroded, so that little is known about them. In order to explain the simultaneous partial closure of all the drainage systems a common, regional, cause must be invoked. All the tectonic basins in the southern part of the SMOc end close to the tectonic depressions related to either the Tepic-Zacoalco or Tula-Chapala rifts. Isostatic uplift of the footwall blocks of these ~E-W-trending rifts may have provoked partial closure of hydrologic systems within the NNE-trending grabens. It is not known when the basins were opened and ceased to act as aggrading systems, but the apparent absence of Blancan age fossils within them may indicate that they could have been opened prior to ~4.75 Ma, which is the numerical value of the beginning of this faunal stage. A probable common cause for the simultaneous opening could be a marine invasion in the region now occupied by the Gulf of California. The new base level of erosion probably increased the stream gradients in the fluvial systems, providing enough energy to the axial rivers within the grabens to overcome the uplift associated with ~E-W rift activity.
... The new record of P. tecolotum from Jalisco increased the Cricetidae diversity in central Mexico, a region that was very dynamic in geological and ecological processes during the Miocene-Pliocene (Woodburne, 2010;Ferrari et al., 2012). This is interesting because other Nearctic and Neotropical mammal groups have their center of diversification in the Trans-Mexican Volcanic Belt (Carranza-Castañeda, 2006;Wang and Carranza-Castañeda, 2008;Jiménez-Hidalgo and Carranza-Castañeda, 2010;Jiménez-Hidalgo and Carranza-Castañeda, 2011;Carranza-Castañeda et al., 2013;McDonald and Carranza-Castañeda, 2017). According to those previous studies, the central region of Mexico served as a center of diversification, refuge and corridor for faunas between North and South America during the GABI. ...
The Sigmodontinae subfamily represents one of the most diverse groups of mammals in the world; this rodent group evolved in the open and arid ecosystems of the Miocene of North America and was the most successful legion of mammals in the Great American Biotic Interchange. Part of its diversification occurred in the Mexican Pliocene, in the Hemphillian-Blancan boundary, where Prosigmodon and Sigmodon species are very common. Recent molecular phyloge-netic systematics research proposes that Sigmodon is related to South American sigmodontines, while studies of classical morphometry in isolated molar teeth consider Prosigmodon as a junior synonymy of Sigmodon, which modifies the biogeographic and chronostratigraphic interpretations of this group in America. In this paper, we describe a new species of Prosigmodon from the late Hemphillian (~4.89 Ma) of central Mexico based on jaws, maxillary and complete isolated teeth. This is the most complete and austral record of the genus in North America. This species was compared with North American species of the Sigmodontinae and Neotominae subfamilies and we defined it as a new Prosigmodon species characterized by having a consistently present minute mesoloph in M1 and M2, in addition, there is an isolated metaconid from the protoconid in the m1 of young individuals. We performed a phylogenetic model using osteodental morphological characters focused on understanding the relationship between Prosigmodon (four species) and Sigmodon (eight species), also we included Baiomys (two species), Neotoma (two species), Peromyscus (two species), and Reithrodontomys (two species). Our results indicate that Prosigmodon is a monophyletic group if Sigmodon minor is included within the genus and P. chihuahuensis is excluded. The Mexican Prosigmodon species have more apomorphic characters with respect to S. minor and P. holocuspis. The species of Prosigmodon and Sigmodon are not closely related. The Sigmodon species are more closely related to the Neotoma species than to the species of Baiomys, Prosigmodon, Reithrodontomys and Peromyscus. Based on the topology of our cladogram and the stratigraphic ranges of the species of Sigmodontinae and Neotominae, we discuss that Baiomys, Prosigmodon, Reithrodontomys and Peromyscus probably diversified in the early Hemphillian (late Miocene), while Sigmodon and Neotoma did so during the late Pliocene.
RESUMEN La subfamilia Sigmodontinae es uno de los grupos de mamíferos más diversos del mundo; este grupo de roedores evolucionó en los ecosiste-mas abiertos y áridos del Mioceno de Norteamérica y fue la legión de mamíferos más exitosa durante el Gran Intercambio Biótico Americano. Parte de esta diversificación ocurrió en México durante el Plioceno, en el límite Henfiliano-Blancano, siendo los representantes más comunes las especies pertenecientes a Prosigmodon y a Sigmodon. Trabajos re-cientes de sistemática filogenética molecular proponen que Sigmodon está relacionado con los sigmodontinos sudamericanos, mientras que estudios de morfometría clásica en fósiles de molares aislados consideran a Prosigmodon como una sinonimia de Sigmodon, lo que tiene un impacto importante en las interpretaciones biogeográficas y cronoestratigráficas de este grupo en América. En este manuscrito describimos una nueva especie de Prosigmodon del Henfiliano tardío (~4.9 Ma) del centro de México con base en mandíbulas, maxilares y dientes aislados completos. Este es el registro más completo del género y también el más austral en Norteamérica. Esta especie se comparó con especies norteamericanas de las subfamilias Sigmodontinae y Neotominae y la erigimos como una nue-va especie de Prosigmodon caracterizada por tener un mesolofo pequeño consistentemente presente en el M1 y M2, además de que en el m1 de individuos jóvenes el metacónido está aislado del protocónido. Se realizó un modelo filogenético con base en caracteres morfológicos osteodentales 322 Pacheco-Castro et al. RMCG | v. 36 | núm. 3 | www.rmcg.unam.mx | DOI: http://dx.doi.org/10.22201/cgeo.20072902e.2019.3.1162 para entender la relación entre Prosigmodon (cuatro especies) y Sigmodon (ocho especies) donde fueron incluidos también Baiomys (dos especies), Neotoma (dos especies), Peromyscus (dos especies) y Reithrodontomys (dos especies). Nuestros resultados indican que Prosigmodon es un grupo monofilético si se incluye Sigmodon minor y se excluye a P. chihuahuensis. Las especies de Prosigmodon mexicanas tienen caracteres apomórficos con respecto a S. minor y P. holocuspis. Las especies de Prosigmodon y Sigmodon no están cercanamente relacionadas, Sigmodon está más re-lacionado con las especies de Neotoma que con las especies de Baiomys, Prosigmodon, Reithrodontomys y Peromyscus. Con base en la topología de nuestro cladograma y los rangos estratigráficos de las especies de Sigmodontinae y Neotominae discutimos que Baiomys, Prosigmodon, Reithrodontomys y Peromyscus probablemente se diversificaron en el Henfiliano temprano (Mioceno tardío), mientras que Sigmodon y Neotoma lo hicieron durante el Plioceno tardío.
... from the Hemingfordian of Oaxaca and the majority of the protohippines have been not considered given that are known from single localities. It is noted that Calippus hondurensis is the well-known and documented protohippine from the late Miocene of central Mexico (Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013). ...
... Temporal ranges of the selected species are derived from the dating of some of the rock bearing-units and the biochronology of Mexican mammalian faunas that contain Neogene horses (Lindsay et al., 1984;Ferrusquía-Villafranca, 1992, 2001Kowallis et al., 1999;Carranza-Castañeda, 2006;Carranza-Castañeda et al., 2013). The species considered comprise 70% of the known record of the Mexican Neogene horses ( Table 2). ...
... Six Mexican species of Equinae are known during the Barstovian. The merychippines have been referred to The information is derived from data in Carranza-Castañeda (2006), Carranza-Castañeda et al. (2013), Ferrusquía-Villafranca (1992, 2001, Kowallis et al. (1999), Lindsay et al. (1984). Ma, million years ago; m. y. million years. ...
North American Equinae integrates a monophyletic clade that consists of about 20 genera and 80 species. This group includes horses with hypsodont cheek teeth belonging to the merychippines and the tribes Hipparionini, Protohippini, and Equini. The primary adaptive radiation and diversification of Equinae occurred in the Neogene period (23.03–2.53 Ma). In Mexico, 11 genera and 20 species of Neogene Equinae have been reported, which correspond to 55 and 28% of the generic and specific diversity in North America, respectively. The Mexican record exhibited their major diversity during the late Miocene (10 species) and evidences part of the evolutionary history of North American Equinae, as it is stated in the following considerations: (1) The presence of merychippine species from the late Hemingfordian—early Barstovian (18–15 Ma) of southern Mexico (“Merychippus” cf. primus and “M.” cf. sejunctus) that are related with earliest representatives of Equinae in North America. (2) The occurrence of populations referable to Cormohipparion aff. quinni, Calippus sp., and Pliohippus sp. from the early—late Barstovian (15–14 Ma) of southern Mexico, which are synchronous with the first known appearances of those genera from the Great Plains and Gulf Coastal Plain in the United States. (3) The equine horse Dinohippus mexicanus from the late Hemphillian (4.8 Ma) of central and northern Mexico that is considered the closest sister species of primitive Equus. These records suggest that early differentiation of some hipparionines, protohippines, and equines may have had occurred also in areas of southern tropical North America during the middle Miocene; furthermore, the origin of primitive Equus could be traced from the Mexican record.
