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Megatylopus sp. from the Blancan III of San Miguel de Allende, Guanajuato. IGM 8823, left DP3 and left DP4: 1, occlusal view; 2, labial view. IGM 9326, right M1 and right M2 fragment: 3, occlusal view; 4, labial view. Scale 5 3 cm.
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During the Pliocene, the diversification of the tribes Lamini and Camelini of the Family Camelidae took place in most of North America, but at present in Mexico the systematics of Pliocene Camelidae are poorly known. Fossil material described in this paper was recovered from Blancan I and Blancan III age floodplain and point bar deposits of the San...
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... Matthew and Cook, 1909 MEGATYLOPUS sp. Figure 6 Diagnosis.-Cheek teeth more hypsodont than in Titanoty- lopus, but much less so than in Megacamelus Frick 1929, Gigantocamelus, and Camelus Linnaeus 1758; I3 and C1/c1 large and rounded, but smaller than in other Camelini except Procamelus Leidy 1858; P1/p1 present; P3/p3 reduced; cement lacking in molar fossettes; nasals flattened in cross section; limbs long without distal shortening typical of Gigantocamelus and Camelus; metapodials longer than basal length of skull ( Voorhies and Corner, 1986;Honey et al., 1998). ...
Citations
... Morphological information on the skulls, mandibles and metatarsals of the extant taxa were obtained from photographs taken from the Field Museum (FMNH), the Smithsonian National Museum of Natural History (USNM) and the University of Michigan Museum of Zoology (UMMZ) via the Animal Diversity Web (ADW 1 ). Morphological information on the skulls, mandibles and metatarsals of the extinct taxa was obtained from the following sources: photographs taken at the American Museum of Natural History (AMNH) by CJ; photographs from online databases of the AMNH, the University of California Museum of Paleontology (UCMP), the University of Florida Museum of Natural History (UF), the Smithsonian National Museum of Natural History (USNM), the Yale Peabody Museum of Natural History (YPM), and the Museum für Naturkunde in Berlin (MfN); and the literature (Wortman, 1898;Matthew, 1908;Frick, 1937;Hibbard, 1951;Patton and Taylor, 1971;Taylor and Webb, 1976;Harrison, 1979;Webb, 1983a;Kelly, 1992;Morgan and White, 2005;Webb and Meachen, 2004;Prothero, 2008;Jimenez-Hidalgo and Carranza-Castañeda, 2010). ...
Savanna-like ecosystems were present at high latitudes in North America during much of the Neogene. Present-day African savannas, like the Serengeti, have been proposed to be modern analogs of these paleosavannas, particularly those from the middle Miocene of the Great Plains region of the United States. Both these extant and extinct savannas contain a preponderance of artiodactyl (even-toed ungulate) species; however, the taxonomic composition of each fauna is different. While present-day African savannas are dominated by ruminants (primarily bovids), the Neogene savannas of North America were dominated by a diversity of both camelid and non-bovid ruminant families. This study provides a quantitative test of the similarity of the artiodactyl faunas of the North American Neogene paleosavannas to those of the modern-day African savannas. A correspondence analysis of ecomorphological features revealed considerable overlap between modern and fossil faunas. The morphospace occupation of the extinct North American ruminants falls within that of the African bovids. Some of the extinct camelids also fall within this same morphospace, but many do not, perhaps indicating an environmental difference such as greater aridity in Neogene North America. The diversity and disparity of artiodactyl faunas through the Neogene of North America changed along with changing temperatures and precipitation regimes. The taxonomic and ecomorphological diversity of the Serengeti ruminant fauna is statistically comparable to those North American paleofaunas occurring during or immediately after the Middle Miocene Climatic Optimum (MMCO), but the later, more depauperate faunas are no longer comparable. This study quantitatively analyzes artiodactyl communities as they changed with the cooling and drying trend seen during the Neogene.
... 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.
... El individuo que produjo el rastro 3 correspondería al más pequeño (1.12 m) y el más grande al del rastro 6 (1.23 m) (Tabla 3 (Lange, 2002). Por lo anterior, es probable que los camélidos que generaron los rastros hayan sido representantes de ese género de lamines, el cual fue bastante común a lo largo del territorio nacional durante el Cenozoico tardío (Jiménez-Hidalgo y Carranza-Castañeda, 2010;Bravo-Cuevas et al., 2012, 2016a). La dirección de los rastros, los valores de velocidad y modalidad de progresión de los organismos que los produjeron, así como la profundidad de las huellas, son evidencia utilizada para establecer un comportamiento gregario a través de huellas (Castanera et al., 2012). ...
The Pie de Vaca locality in the State of Puebla stands out for its important abundance of fossil mammal footprints, among them, the most representatives have been referred to camelids and felids. The purpose of the present study was the formal characterization of this set of footprints and comment on some paleobiological aspects related to their size, speed, and mode of progression of the track-makers. The sample consists of 233 footprints including 154 referable to nine trackways produced by camelids and 79 referable to three trackways produced by felids. The characterization of the tracks was made by comparing their size and morphology with others produced by fossil and recent taxa. The impressions of camelids, based on their shape and size, were designated to the icnospecies Lamaichnum guanicoe because they show the typical morphological pattern of this group of artiodactyls. It is suggested that they were produced by some member of the genus Hemiauchenia, which corresponds to the most common camelid of the Late Cenozoic of Mexico. On the other hand, the tracks of felids were only referred to the morphofamily Felipedidae due to the bad preservation of its ichnotaxonomic characters; however, being larger than traces of the ichnogenera Felipeda, Pycnodactylopus, Pumaeichnum and Mitsupes, it is suggested that they were produced by some form of medium to large size, a machairodontid or a pantherine, for instance. The mode of progression of both producers corresponds to that of relatively fast walking organisms that move at a speed lower than 4 m/s. The direction and number of individuals of camelids trackways, are indicative of gregarious behavior, probably associated with a certain social organization. In the case of felids, solitary or couple behavior is proposed. © 2018 Instituto de Geologãa, Universidad Nacional Autãnoma de Mã.
... Por otro lado, hasta principios de la década de 1970, los mamíferos del Plioceno mexicano fueron conocidos casi exclusivamente a partir de material de localidades en chihuahua y algunas en Guanajuato (Montellano-Ballesteros y Jiménez-Hidalgo, 2006), pero se conocía muy poco sobre los mamíferos de esa época en la mayor parte del país. El estudio continuo de las localidades del Mioceno y Plioceno del centro de México por alrededor de 40 años ha permitido describir nuevas especies, extender los rangos biocronológicos de ciertas especies, como camellos, berrendos y roedores, así como modificar la distribución geográfica de varios taxones (carranza-castañeda 2006, Jiménez Hidalgo y carranza-castañeda, 2010carranza-castañeda et al., 2013). ...
... M. coloradensis; camelids, Hemiauchenia vera, Megatylopus matthewi, and Alforjas sp.; rodents, Spermophilus sp., Ammospermophilus sp., Paenemarmota sp., Perognathus sp., ?Pliogeomys sp., Calomys sp., Baiomys sp., Prosigmodon sp. and Neotoma sp.; the xenarthran Megalonyx sp.; lagomorphs, Hypolagus mexicanus and Notolagus velox; and the proboscidean Rhynchotherium sp. (Miller REVISTA MEXICANA DE CIENCIAS GEOLÓGICAS v. 34, núm. 1, 2017, p. 38-44 Diet and habitat of unique individuals of Dinohippus mexicanus and Neohipparion eurystyle (Equidae) from the late Hemphillian (Hh3) of Guanajuato and Jalisco, and Carranza-Castañeda, 1984Carranza-Castañeda, 2006;Jiménez-Hidalgo and Carranza-Castañeda, 2010;Carranza-Castañeda et al., 2013). These faunas constitute the basis for the late-Hemphillian biostratigraphy of central Mexico. ...
Stable carbon and oxygen isotopes were determined in molar enamel from fossil Pliocene equids from Rancho El Ocote in the San Miguel Allende basin, Guanajuato, and from Santa María, Tecolotlán basin, Jalisco. At each locality, the source was one molar from an individual Dinohippus mexicanus and one molar from an individual Neohipparion eurystyle. Results indicated that the N. eurystyle individu-als from both localities had been C3/C4 mixed feeders, and had lived in open-zone vegetation (δ13C: -3.1‰ to -1.3‰; δ18O: -4.9‰ to -6.4‰). On the other hand, the D. mexicanus from Rancho El Ocote had fed upon C4 plants and lived in open zones (δ13C: -1.3‰; δ18O: -4.9‰), whereas the D. mexicanus from Santa María was a C3/C4 mixed feeder with considerable consumption of C3 plants (δ13C: -7.7‰; δ18O: -6.4‰). These results could be contrasted to suggestions from previous isotopic work that D. mexicanus in Mexico predominantly fed on C4 plants and further samples analyses are warranted. This study contributes to the understanding of the Pliocene equid taxa from central Mexico and emphasizes the presence of different diets, ranging from exclusive C4 to mixed C3/C4 plants.
... En México Hemiauchenia vera ha sido registrada en las localidades henfilianas tempranas (Hh2) de La Presa y tardías (Hh3) de Coecillos y en las localidades henfiliano tardías de Tepalcates y la Rinconada (Hh3-Hh4), y blancanas de Rhino Layer y Rancho El Ocote, en la Cuenca de San Miguel Allende, Guanajuato (Montellano-Ballesteros, 1989;Jiménez-Hidalgo & Carranza-Castañeda, 2010;Carranza-Castañeda et al., 2013); así como la localidad de Santo Domingo en la Cuenca de Colotlán-Tlaltenango, Zacatecas (Henfiliano temprano Hh2) y las localidades de La Hacienda y Santa María en la Cuenca de Tecolotlán, Jalisco (Henfiliano tardío, Hh3-Hh4) . El registro de Hemiauchenia vera Matthew, 1909 en el Mioceno Superior de Costa Rica, corresponde al registro más austral de la especie (ver figs. ...
This work describes abundant fossil remains of a species of lamine camel, recovered from the San Ge- rardo de Limoncito local fauna in southern Costa Rica. The material corresponds to dental pieces and postcranial bones of Hemiauchenia vera Matthew, 1909 species, which is basically recognized by the biometry of the astragali and the anterior phalanx I, besides dental morphology. This new fossil record also permits to accurate the biochronologic age of the outcrop and its correlation with other Early Hemphillian localities of North America.
... The Hemphillian and Blancan associated fauna from the same beds where the Hexobelomeryx material was recovered consists of diverse species of xenarthrans, lagomorphs, rodents, ursids, canids, mustelids and felids; also, ghomphotherids, rhinoceroses equids, tayassuids, a protoceratid, camelids and some other antilocaprid species have been collected (Carranza-Castañeda and Miller, 2000;Carranza-Castañeda, 2006;Jiménez-Hidalgo and Carranza-Castañeda, 2010). The mammalian index genera and species of the bearing localities from San Miguel de Allende were previously published by Carranza-Castañeda (2006) and references therein; so, they are not repeated here. ...
Hexobelomeryx fricki is recorded in the San Miguel de Allende graben since the late early Hemphillian to the Blancan III, from about 7.0 millionyears to 3.0 millionyears. The studiedspecimens were recovered from floodplain andpoint bar deposits of the informal Rancho Viejo beds. The mortality profile of the H. fricki teeth sample from the study area is an attritional one, with few juveniles and a large majority of old individuals. The estimated body mass of H. fricki specimens range from around 10 to 30 kilograms, according to their age at death. The record of this pronghorn in Guanajuato during the late early Hemphillian and the Blancan III, are the oldest and the youngest occurrence of the species in North America and extends its geographic distribution from northwestern Mexico to central Mexico during the late Hemphillian.
... Ma) from central Mexico (Jiménez-Hidalgo and Carranza-Castañeda, 2010) and the southern Plains (Morgan and Lucas, 2003;Thompson and White, 2004;Morgan and White, 2005). Camelops evolved into possibly as many as six distinct species through the Plio-Pleistocene, however, some camelid specialists recognize the need for a thorough reexamination of the genus (Webb, 1965;Dalquest, 1992;Jiménez-Hidalgo and Carranza-Castañeda, 2010). The species C. hesternus is best known from Sangamonian interglacial (MIS 5) and later Rancholabrean faunas from across western North America (Kurtén and Anderson, 1980;Pinsof, 1996;Harington, 1997b). ...
Western camel ( C. hesternus ) fossils are rare from Eastern Beringia, thus there is little available information on their chronology, paleoecology, and biogeography in this region. In August of 2010, a partial proximal phalanx of a western camel was recovered from a sedimentary exposure along the White River, in the formerly glaciated terrain of southwest Yukon, northwest Canada. The fossil specimen was recovered in situ from sediments that are correlated by stratigraphic, tephra and radiocarbon data to the Marine Isotope Stage (MIS) 5 interglacial period (Sangamonian). Associated paleoenvironmental data indicates that this western camel inhabited a shrub tundra ecosystem that did not include spruce trees or boreal forest during a relatively cold interval between MIS 5e and 5a. This is the oldest reliably dated western camel fossil from Eastern Beringia and supports the model of range expansion for this species to the high latitudes of northwest North America during the last interglacial ( sensu lato ).
... Consequently, at present the picture of the Mexican Pleistocene fauna is biased because the knowledge of the Neotropical community is incomplete. It is unknown if the Late Pleistocene extinction event was isochronous with that from the temperate North America, or as in the Pliocene, some lineages persisted longer in subtropical and tropical North America than in the northern areas (Jiménez-Hidalgo & Carranza-Castañeda, 2005; Montellano-Ballesteros & JiménezHidalgo, 2006; Jiménez-Hidalgo & Carranza-Castañeda, 2009). Also, biogeographic patterns of Pleistocene North American mammals cannot be completely reconstructed at present because there is not enough information about the geographic distribution of many species (MontellanoBallesteros & Jiménez-Hidalgo, 2006; Jiménez-Hidalgo et al., 2007; Arroyo-Cabrales et al., 2008). ...
Paleontological work carried out in the Late Pleistocene floodplain and bar fluvial deposits of northwestern Oaxaca, southern Mexico, resulted in collecting cranial and poscranial material of mammals identified as Glyptotherium, Hemiauchenia, Camelops, Odocoileus, two Equus species, Cuvieronius, Mammuthus and Bison. The presence of Bison in all the localities indicates a Rancholabrean North American Land Mammal age for the faunal assemblage. Also, many mollusk specimens were collected and belong to five families of terrestrial gastropods, three families of freshwater gastropods, and one family of freshwater bivalves. Additionally, several fragments of Rodentia indet., sigmodontine rodents, and scincomorph lizards were also recovered through the screen-washing of sediments. This faunal association was designed herein as the Viko vijin (cold epoch or period in Mixteca language) Local Fauna (L. F.) and shares nine mammalian taxa with the Rancholabrean local faunas of Terapa (Sonora, NW Mexico), Chapala (Jalisco), El Cedazo (Aguascalientes) and Tequixquiac (Mexico), central Mexico. Likewise, five of the eight mollusk families identified are also present in the Late Pleistocene Rancho La Amapola, San Luis Potosi, Central Mexico. The presence of the llama Hemiauchenia in Oaxaca represents the southern-most record of this genus during the Late Pleistocene in North America, while Late Pleistocene scincomorph lizards are recorded for first time in Oaxaca. Similarly, the records of the mollusk families Bulimulidae, Polygyridae and Urocoptidae in the Mixteca Alta Oaxaquenit are the first for Mexico and allow extend their geographic ranges from southern USA to southern Mexico during the Late Pleistocene.
Encompassing global cooling, the spread of grasslands, and biogeographic interchanges, the Hemphillian North American Land Mammal Age is an important interval for understanding the factors driving ecological and evolutionary change through time. McKay Reservoir near Pendleton, Oregon is a natural laboratory for analyses of these factors. It is remarkable for its small vertebrate fauna including rodents, bats, turtles, and lagomorphs, but also for its larger mammal fossils like camelids, rhinocerotids, canids, and felids. Despite the importance of the site, few revisions to its faunal list have been published since its original description. We expand on this description by identifying taxa not previously known from McKay Reservoir based on specimens collected during fieldwork and through reidentification of previously collected fossils. Newly identified taxa include the borophagine canid Borophagus secundus (Matthew and Cook, 1909), the camelids Megatylopus Matthew and Cook, 1909 and Pleiolama Webb and Meachen, 2004, a dromomerycid, and the equids Cormohipparion Skinner and MacFadden, 1977 and Pseudhipparion Ameghino, 1904. Specimens previously assigned to Neohipparion Gidley, 1903 and Hipparion de Christol, 1832 lack the features necessary to diagnose these genera, which are therefore removed from the site's faunal list. The presence of Borophagus secundus , Cormohipparion , and Pseudhipparion is especially important, because each occurrence represents a major geographic range extension. This refined understanding of the fauna lays the foundation for future studies of taphonomy, taxonomy, functional morphology, and paleoecology—potentially at the population, community, or ecosystem levels—at this paleobiologically significant Miocene locality.
