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The gomphotheres were a diverse and widespread group of proboscideans occupying Eurasia, North America, and South America throughout the Neogene. Their decline was temporally and spatially heterogeneous, and the gomphotheres ultimately became extinct during the late Pleistocene; however, the genusCuvieroniusis rarely represented in late Pleistocene assemblages in North America. Two alternative hypotheses have been invoked to explain this phenomenon: (1) competitive exclusion by sympatric mammoths and mastodons or (2) ecologic displacement due to an environmental transition from closed forests to open grasslands. To test whether competition for resources contributed to the demise of North AmericanCuvieronius, we present herein a large collection of stable isotope and dental microwear data from populations occupying their Pleistocene refugium in the Atlantic Coastal Plain. Results suggest thatCuvieroniusconsumed a wide range of resources with variable textural and photosynthetic properties and was not specialized on either grasses or browse. Further, we document evidence for the consumption of similar foods between contemporaneous gomphotheres, mammoths, and mastodons. The generalist feeding strategy of the gomphotheres likely facilitated their high Miocene abundance and diversity. However, this “jack of all trades and master of none” feeding strategy may have proved challenging following the arrival of mammoths and likely contributed to the extirpation ofCuvieroniusin North America.

In 2008 a rich accumulation of vertebrate bones and teeth was discovered in a small tributary drainage to Big Cypress Creek near the town of Hockley in Harris County, Texas. The fossils were recovered from sandy sediments of fluvial origin, interspersed with contemporaneous spring boil deposits, attributed to the Deweyville Formation and the recovered remains consist entirely of disarticulated and dissociated skeletal elements and teeth. Distinct stratigraphic horizons are limited in extent in the fossiliferous sections along the drainage, and the fossils are generally concentrated in close association with gravel lag deposits. Two radiocarbon dates on wood suggest that the fauna may have accumulated about 24,000 years ago but presence of spring deposits, association with lag deposits, and the aerial extent (approximately 125 m of exposed section along the length of the tributary) could indicate significant time averaging during the Rancholabrean (Bison occurs in the fauna). The unique faunal character of the site is emphasized by a single tooth of Mixotoxodon, a notoungulate mammal, that provides the first evidence of this taxon from the United States. The fauna is dominantly composed of herbivorous megafauna with two proboscideans (Mammuthus and Cuvieronius). Mammut americanum has not yet been found in the fauna. Isotopic analyses of the proboscideans and some of the other megafauna suggest that an open environment with scattered woodland habitat existed in southeastern Texas at the end of the last glacial period.

We present a revision, dating and interpretation of the Late Pleistocene megafauna of Guatemala based on paleontological material located in collections in the country and other fossils housed in the American Museum of Natural History, New York. Assemblages are dominated by proboscideans (Cuvieronius) and xenarthrans (Eremotherium, Glyptotherium), while co-occurring Equus and Mixotoxodon are significantly less frequent, and Holmesina, Palaeolama, Tapirus, Neocherus, Mammuthus and other ground sloth taxa (Paramylodon; Megalonyx) are rare. Contrary to published records the faunal assemblage is dominated by North American faunal elements. The underrepresentation of typical South American fauna therefore suggests a more southernly located biogeographic juncture between the two subcontinents, at least for the Late Pleistocene. The biogeographical barrier was either formed by the high mountain chains, or alternating periods of low and high precipitation that triggered the intermittent expansion of either grass- or woodland, thus leading to an alternating filter for either grazers or browsers. The presence of an oak-dominated forest vegetation with Mixotoxodon, Eremotherium and Cuvieronius supports high precipitation rates during MIS 3 and 2, followed by drought during the Late Pleistocene deglaciation. The expansion of grassland during the Younger Dryas period favored the migration of Mammuthus along the Mesoamerican Corridor, which is otherwise absent in Guatemala. Our data also suggest a survival of Cuvieronius into the early Holocene in the southeastern lowlands of Guatemala along the Motagua river. Our review is important as Guatemala is key to understanding migrations along the Mesoamerican Corridor that acted as a bridge but also as a filter of faunal interchange between North- and South America.

The Gomphotheriidae family belongs to the Proboscidea order. Gomphotheres were elephant-like mammals whose representatives inhabited North America from the Middle Miocene to the late Pleistocene. In this work, a gomphothere remains from Santiago Tepeticpac (Tlaxcala, Mexico) are described. The comparative study with other Proboscidea, mainly from different localities of Mexico and South America, mostly Argentina and Brazil, allowed to identify them as Cuvieronius genus. The microwear signature together with carbon and oxygen stable isotopes showed that this animal was a mixer feeder and inhabited open zones with patches of wooded flora. These analyses also indicated the presence of high abrasiveness components and C4 plants (grasslands) and medium to low wearing elements as well as C3 vegetation (forest) in the site. The strontium isotopic signature implies that this gomphothere lived in the Puebla-Tlaxcala Valley. The paleoenvironmental inferences would show regional conditions., We thank Project 11824 of the National Coordination of Cultural Heritage Conservation-INAH for facilitating the collaboration of Dr. María Teresa Alberdi Alonso during the month of November 2016 in the workshop/laboratory of Conservation of Organic Materials of the CNCPC-INAH. To PAPIIT-UNAM-México (#IN404714, IA#104017 and IA#102719), support for this project to Edith Cienfuegos-Alvarado and Víctor Adrián Pérez Crespo. DGICYT CGL2016-79334-P from Spain granted to Maria Teresa Alberdi contributed to funding this investigation., Coordinación Nacional De Conservación Del Patrimonio Cultural (México), Universidad Autónoma Nacional de México

Based on data from analyses on previously-reported carbon stable isotope data from dental enamel and dentine from tusks reported in the literature, diets were inferred for the gomphothere genera Amebelodon, Cuvieronius, Gomphotherium, Rhynchotherium, Serbelodon, and Stegomastodon (Proboscidea, Gomphotheriidae) that inhabited the Americas during the Cenozoic. Amebelodon, Gomphotherium, and Serbelodon specimens of the Barstovian and Clarendonian faunal stages fed on C plants; while the same Hemphillian genera consumed a mixed C/C diet. Hemphillian Rhynchotherium were mixed-diet feeders while Blancan specimens of the same genus fed on C plants. Stegomastodon from the same Blancan period consumed a mixed C/C diet, similar to Rancholabrean animals, although Lujanian specimens ate C plants. As for the genus Cuvieronius, Irvingtonian, Rancholabrean, and Lujanian specimens consumed a mixed C/C diet. These results suggested that American gomphotheres displayed generalist feeding habits, allowing them to inhabit different environments in extensive areas of the continents, and survive to the end of the Pleistocene., To PAPIIT (IA#104017 and IA#102719), for providing financial support for this project to Víctor Adrian Perez Crespo. Research Project ANPCYT PICT 20151512 and Grant UNICEN, Argentina were awarded to Jose Luis Prado; DGICYT CGL2016-79334-P from Spain granted to Maria Teresa Alberdi contributed to funding this investigation.

The diversity of South American proboscideans during the Quaternary has been a subject of discussion for decades. The presence of Cuvieronius hyodon in South America is unquestioned and unanimous; however, the taxonomy of the known second South American proboscidean is still a controversy. Some authors argue that the South American species traditionally referred to Stegomastodon should instead be referred to a distinc genus, namely Notiomastodon, endemic to South America. Others authors, however, do not accept this attribution and continue to recognize the genus Stegomastodon as present in South America. In this study, we recognize several differences in the mandible, skull, dentition, and postcranial morphology of North American species of Stegomastodon and Notiomastodon, that further support the validity of Notiomastodon as a taxon separate from Stegomastodon. Indeed, a phylogenetic hypothesis of trilophodont bunodont proboscideans supports the separation between Stegomastodon and Notiomastodon, and the diversification of the common ancestor of these proboscideans may have occurred during the middle to late Miocene. No specimen with Stegomastodon diagnostic features is recognized in South America. The Stegomastodon records are restricted to the Pliocene-middle Pleistocene of North America, while Notiomastodon records are found only from the middle Pleistocene-early Holocene of South America. In this way, we recognize that Stegomastodon records are restricted to North America and that only Cuvieronius and Notiomastodon are recorded in South America.

The Gomphotheriidae family included a large number of taxa, and a fossil record with extensive geographic and stratigraphic distribution. In South America, the gomphotheres evolved the dibelodont and brevirostrian characteristics, with brachydont, bunodot and subhypsodont molar teeth. Among palaeontologists it is generally accepted the division of gomphotheres into two different groups: the lowland and Andean gomphotheres. There is scientific consensus to designate the species Cuvieronius hyodon as representative of the Andean-type gomphotheres, and in the last few decades, the genus Stegomastodon including its two species S. platensis and S. waringi was described as a lowland-type gomphothere. Recent studies included the genus Stegomastodon within the genus Notiomastodon, with the species Notiomastodon platensis as endemic for the region. In Chile, the most abundant fossils of megafauna from the late Pleistocene—early Holocene limit are gomphotheres, counting with one of the southernmost fossil records that extend to Castro, on the island of Chiloe. The most common fossil remains are molars that are the base of many scientific studies aiming to synthesize the complex history of these mammals. The investigation of the Pilauco site in south-central Chile has improved our paleoecological knowledge of these mammals, as well as the taphonomic processes that favoured their fossilization in southern South America.

Diet and habitat were estimated, based on stable isotopes, for six species of proboscideans inhabiting the Americas during the Pleistocene. In North America, Mammuthus columbi (Elephantidae) was a mixed C3/C4 herbivore inhabiting open areas, while Mammut americanum (Mammutidae) fed exclusively on C3 plants and preferred closed areas. In contrast, members of the family Gomphotheriidae showed a wide range of food preference and habitats. This is the case of Cuvieronius tropicus, a mixed-diet herbivore living in open areas. In South America, another gomphothere — Cuvieronius hyodon — inhabited open areas and had a C3-plant diet similar to others from some Southern plains such as Stegomastodon platensis. On the other hand, S. waringi from tropical South America lived in open areas and had a C3/C4 mixed diet. The fact that gomphotheres had more flexible diet habits could explain why those animals were able to cross the Panamanian Isthmus, while mammoths and mastodons did not.

Fishermen have recovered four Quaternary proboscidean teeth from the continental shelf in the vicinity of the Pearl Islands, about 50–80 km offshore from the southern coast of Panama. Two upper third molars (M3) and one lower third molar (m3) are similar to comparable teeth of the Pleistocene gomphothere Cuvieronius based on the presence of 4½ to 5½ lophs/lophids that are either horizontal or slightly inclined to long axis of the tooth and rather complicated enamel with single trefoils, incipient double trefoils, and numerous small accessory cusps. Cuvieronius is also known from the Pleistocene El Hatillo and La Trinidaita sites from the Azuero Peninsula in Panama. The teeth of Cuvieronius from the Pearl Islands are referred to C. hyodon following recent taxonomic revisions indicating a single pan-American species of this genus was present in both North America and South America. The oldest records of Cuvieronius are from early Pleistocene (early Irvingtonian) faunas in El Salvador, Florida, and New Mexico. Cuvieronius dispersed to South America in the early Pleistocene during the Great American Biotic Interchange, with the earliest record of C. hyodon on that continent from the early to middle Pleistocene (Ensenadan) Tarija fauna in Bolivia. The two late Pleistocene populations of C. hyodon in the Neotropical region have a disjunct biogeographic distribution, with the population from southern Mexico and Central America separated from the second population in the Andean highlands of Ecuador, Peru, and Bolivia by a distance of about 1000 km. The intervening region comprising the lowland tropics of northern South America was populated by the gomphothere Notiomastodon during the late Pleistocene, although Notiomastodon is also known from Andean localities in Ecuador and Peru. Two of the Cuvieronius teeth from the Pearl Islands were recovered in nets by shrimp fisherman from depths of about 90 m, likely indicating they date to the Last Glacial Maximum between 30 and 15 ka, when sea level was as much as 120 m lower than present and the Gulf of Panama was dry land. These teeth represent the first record of late Pleistocene fossils of terrestrial mammals from the continental shelf in Central America.

A lower mastodont molar was found in Nacaome river, Nicoya, Guanacaste, Costa Rica. It is a Pleis- . tocene specimen of Cuvieronius hyodon .C. hyodon and Haplomastodon waringi, mountain and savanna mastodonts respectively, have been found in the same place. This evidence and the dental morphology suggest that they were seasonaly simpatric species with different alimentary niches. Probably H. waringi fed on savanna or prairie plants (very ligneous with high silíca concentration, e.g,Cyperaceae) whereas C. hyodon consumed sQfter plants (the enamel is less damaged).

In 2002, we assessed all sites known to us that had been suggested to provide evidence for the association of Clovis-era archaeological material with the remains of extinct Pleistocene mammals in North America. We concluded that, of the 76 sites we assessed, 14 provided compelling evidence for human involvement in the death and/or dismemberment of such mammals. Of these sites, 12 involved mammoth (Mammuthus), the remaining two mastodon (Mammut). Here, we update that assessment. We examine Clovis-era, and earlier, sites reported since 2002, as well as sites examined previously but for which additional information has become available. Our assessment leads us to exclude Hebior (Wisconsin) from the list of accepted sites, and to add El Fin del Mundo (Sonora) and Wally's Beach (Alberta). There are now 15 sites on our list, providing what we find to be compelling evidence for human involvement in the death and/or dismemberment of five genera of now-extinct late Pleistocene mammals: Equus, Camelops, Cuvieronius, Mammut, and Mammuthus. As in 2002, however, we note this is a small fraction of the 37 genera that disappeared at the end of the Pleistocene, and for this and other reasons we remain highly skeptical that human overkill was responsible for their extinction.

Despite more than two centuries of study, the South American Gomphotheriidae (SAG) taxonomy, phylogeny and biogeography are still problematic. The current knowledge about SAG is outdated and a revision of the classic concepts is necessary. Here, we analyzed a very large sample of Gomphotheriidae remains from North and South Americas. A taxonomic revision based on well-preserved diagnostic materials allowed the recognition of Notiomastodon platensis and Cuvieronius hyodon to South America, which are distributed from lowland to highland localities in this continent. Nevertheless, SAG remains of 66% of analyzed localities are not significantly diagnostic at specific level. Amahuacatherium peruvium diagnostic features are considered invalid and within the morphological variability range expected for N. platensis . The genus Stegomastodon is recognized as absent from South America and morphologically distinct of SAG taxa. The oldest record of SAG indicates that the arrival of this family in South America probably occurred during the Plio-Pleistocene, after the closure of the Isthmus of Panama.

Studies on South American Gomphotheriidae started around 210 years ago and, 150 years later, the classic study “The mastodonts of Brazil” by Simpson and Paula Couto (1957) attempted to clarify the complex issues related to our understanding of these proboscideans. Here, we update state of knowledge regarding proboscideans in South America subsequent to the publication of Simpson and Paula Couto (1957). The taxonomy of South American proboscideans is now stable and two species are recognized, Notiomastodon platensis and Cuvieronius hyodon. The former had a wide distribution in South America (from lowlands to highlands and from east to west coasts), while the latter was restricted to Ecuador, Peru and Bolivia. Although records of Notiomastodon are abundant and occur in almost overlapping geographic distribution with Cuvieronius, they have never been recorded in the same locality. Here, we evaluated over 500 South American localities with proboscidean remains, although only cranial and dental specimens show recognizable diagnostic features. As both proboscideans in South America had a generalist-opportunist alimentary strategy, a competitive exclusion probably precluded their sympatry. Their origin is most probably related to independent migrations from Central America during the Great American Biotic Interchange. They are not sister-taxa – Cuvieronius hyodon is sister-taxon of Rhynchotherium, and this clade is closer to Notiomastodon platensis than to the other proboscideans, supporting the hypothesis of independent origins. Notiomastodon platensis has a continuous record from the Early Pleistocene to Early Holocene, when it became extinct, probably due to synergy of human impact and climatic changes during the Pleistocene/Holocene transition. In contrast, extinction of Cuvieronius hyodon happened much earlier, and it was not related to the terminal Pleistocene event that lead the extinction of selected megafauna in South America, including Notiomastodon., Facultad de Ciencias Naturales y Museo

The earliest known foragers to populate most of North America south of the glaciers [∼11,500 to ≥ ∼10,800 14C yBP; ∼13,300 to ∼12,800 calibrated (Cal) years] made distinctive “Clovis” artifacts. They are stereotypically characterized as hunters of Pleistocene megamammals (mostly mammoth) who entered the continent via Beringia and an ice-free corridor in Canada. The origins of Clovis technology are unclear, however, with no obvious evidence of a predecessor to the north. Here we present evidence for Clovis hunting and habitation ∼11,550 yBP (∼13,390 Cal years) at “El Fin del Mundo,” an archaeological site in Sonora, northwestern Mexico. The site also includes the first evidence to our knowledge for gomphothere (Cuvieronius sp.) as Clovis prey, otherwise unknown in the North American archaeological record and terminal Pleistocene paleontological record. These data (i) broaden the age and geographic range for Clovis, establishing El Fin del Mundo as one of the oldest and southernmost in situ Clovis sites, supporting the hypothesis that Clovis had its origins well south of the gateways into the continent, and (ii) expand the make-up of the North American megafauna community just before extinction.

What is currently known about Mexico paleontology and specifically the proboscideans has centered in the central and southern states, with much of the north largely unknown. Here we report on Cuvieronius (Gomphotheriidae) and Mammuthus (Elephantidae) recovered from Terapa, a Late Pleistocene site in east-central Sonora. The local fauna reflects a badlands environment along the Rio Moctezuma, 183 km (114 mi) south of the Arizona border. The recovery of Bison places the locality within the Rancholabrean Land Mammal Age. Chronological analyses confirm that impounding basalt and fossiliferous sediments were deposited 43,000 to 40,000 years ago (MIS 3). Cuvieronius and Mammuthus are found throughout the stratigraphic profile. A review of Late Pleistocene collections indicates that Mammuthus, Cuvieronius, and one location of Mammut are known from Sonora. The Late Pleistocene along the Terapa river valley is reconstructed as cooler, with a more equable, less seasonal environment than today. The corridor was wetter, more tropical and included a riparian forest, ponding water, marsh, and savanna grassland. The area west of Terapa in western Sonora had a cooler summer climate, more winter rains and less summer rains. Woodlands and shrub communities occupied the upper bajadas and rocky hills, areas possibly where Mammut ranged more commonly. Valleys contained more grasslands than they do today. The environments and climates of valleys permitted Cynomys, Mammuthus, and Cuvieronius to exist over most of western Sonora where they are extinct today.

The Order Proboscidea in Mexico is composed of the families Elephantidae, Mammutidae, and Gomphotheriidae. The last one includes the genus Cuvieronius. In this paper, we present a skull identified as the first record of Cuvieronius hyodon in Valparaiso, southwestern Zacatecas.

"Se describen los restos de Cuvieronius hyodon, recuperados en el estado de Colima, enfatizando las características que permiten diferenciar los restos postcraneales de este gonfoterio de los de otros proboscidios mexicanos. El estudio del esqueleto permitió iden- tificar cuatro individuos adultos, dos hembras y dos machos, e interpretar las diferencias en talla como consecuencia del dimorfismo sexual secundario. El análisis bivariante comparativo de los terceros molares inferiores ubicó la talla de la población de Colima como intermedia entre las poblaciones mexicanas (167-215 mm de longitud del molar), aunque es pequeña comparada con las poblaciones sudamericanas (197-243 mm). La distribución de las localidades de Cuvieronius en el país sugiere que la dispersión del grupo se efec- tuó a través de las tierras bajas de ambas vertientes, de manera similar a lo que se observa en especies actuales de afinidad tropical."

The South American gomphotheres were previously classified in three genera and three species. Two biogeographic corridors are recognized for the dispersion of gomphotheres in South America. Cuvieronius hyodon was found mainly in the highlands and west to the Andes, and Stegomastodon platensis and Haplomastodon chimborazi were found in lowlands. The aim of the present study is to review the taxonomy of South American lowland gomphotheres. A large sample of specimens was analyzed, which included crania, teeth and postcrania from several localities in Brazil, Ecuador, Colombia, Venezuela, Argentina, and Uruguay. A review of the diagnostic characters proposed in previous taxonomic studies of South American lowland gomphotheres found that they are variable in both reputed species if large samples are considered. There is no support for more than one South American lowland gomphothere species, and it shows a significant morphological variation in some characteristics. The name for this taxon, after a taxonomic review, must be Notiomastodon platensis (Ameghino, 1888) new combination. This reduces the number of gomphothere species in South America to two genera and species. The lowland gomphothere is closely related to Cuvieronius and Rhynchotherium, and not closely related to Stegomastodon from North America, and Sinomastodon from Asia.

The taxonomic history of South American Gomphotheriidae is very complex and controversial. Three species are currently recognized: Amahuacatherium peruvium, Cuvieronius hyodon, and Notiomastodon platensis. The former is a late Miocene gomphothere whose validity has been questioned by several authors. The other two, C. hyodon and N. platensis, are Quaternary taxa in South America, and they have distinct biogeographic patterns: Andean and lowland distributions, respectively. South American gomphotheres became extinct at the end of the Pleistocene. We conducted a phylogenetic analysis of Proboscidea including the South American Quaternary gomphotheres, which resulted in two most parsimonious trees. Our results support a paraphyletic Gomphotheriidae and a monophyletic South American gomphothere lineage: C. hyodon and N. platensis. The late Miocene gomphothere record in Peru, Amahuacatherium peruvium, seems to be a crucial part of the biogeography and evolution of the South American gomphotheres.

There is an abundant fossil record of the family Gomphotheriidae in Chile, which is en- tirely ascribed to the late Pleistocene. Despite this, the lack of taxonomically diagnostic material has lead to an extended discussion, which has not reached a consensus regarding the number of forms of gomphotheres effectively present. This paper discusses the taxonomy of Chilean gomphotheres, based on tooth morphology and biometry, paleoecological and biogeographical data. The morphol- ogy of the tusks indicates the presence of the Stegomastodon genus in Chile, while bivariate and multivariate analyses of the teeth show an important amount of variability within the studied sample, although with a tendency towards larger sizes for the genus Stegomastodon and the Chilean samples than for Cuvieronius, especially among the M3s and m3s. In spite of this, in this paper only the specimens from localities that yielded molars associated with tusks are assigned to the genus Stego­ mastodon. Biogeographic information is consistent with the presence of a lowland-adapted taxon such as Stegomastodon, which could have reached the Chilean territory either through an Andean corridor from Argentina, or through a low-altitude route from Peru, then by the northern region of Chile. Bibliographic isotopic data also indicates an adaptative change to C3 feeding along a latitudi- nal gradient, around 35-41oS, which makes the Chilean and south Argentinean results quite similar at these latitudes. Due to the metric variability observed, the Chilean samples could not be assigned to individual species.

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 Oaxaquena are the first for Mexico and allow extend their geographic ranges from southern USA to southern Mexico during the Late Pleistocene.

I present here a revision of the late Pleistocene Haplomastodon chimborazi (Proano, 1922) material from Bolivar, Ecuador and a comparison with other New World trilophodont gomphotheres, and provide new morphological data in order to develop a novel phylogenetic hypothesis of South American (SA) proboscideans. Haplomastodon Hoffstetter, 1950 includes a single SA species whose valid name is H. chimborazi. Haplomastodon waringi (Holland, 1920) is considered to be an invalid taxon as it is based on undiagnosed material. Phylogenetic analysis supports the monophyly of SA gomphotheres (Cuvieroniinae) H. chimborazi, Cuvieronius hyodon (Fischer de Waldheim, 1814), and “Stegomastodon” platensis (Ameghino, 1888), based on five unambiguous characters. Conflicting evidence regarding the interrelationships of SA gomphotheres leads to three possible alternative hypotheses: two paired associations ((H. chimborazi, “S.” platensis) C. hyodon) and ((C. hyodon, “S.” platensis) H. chimborazi), and a trichotomy. Thes...

The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised. Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges. Trans-isthmian land mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10914-010-9144-8) contains supplementary material, which is available to authorized users.

The purpose of this application, under Articles 68 and 75 of the Code, is to conserve the generic name Cuvieronius Osborn, 1923, long and widely applied to extinct South American gomphotheriid proboscideans, by setting aside all previous type species fixations and designating Mastotherium hyodon Fischer, 1814 as the type species of Cuvieronius and by designating a neotype for that species. Because M. hyodon has long and universal (though incorrect) usage as the type species of Cuvieronius and because the type specimen of M. hyodon is unidentifiable, the type species and neotype designations are proposed to promote the stability and universality of nomenclature.

The purpose of this application, under Article 75.5 of the Code, is to conserve the usage of the name Mastodon waringi Holland, 1920, for a species of extinct South American proboscidean, by designating a neotype. Because M. waringi has had long and wide (though incorrect) usage as a species of Haplomastodon, and because the holotype of M. waringi is undiagnostic, the neotype designation is proposed to promote stability of nomenclature.

The incisors of proboscideans (tusks and tushes) are one of the most important feature in conservation, ecology and evolutionary history of these mammals. Although the absence of upper incisors is rare in proboscideans (occurring only in deinotheres), the independent losses of lower incisors are recognized for most of its lineages (dibelodont condition). The presence of lower incisors in the Pan-American gomphothere Cuvieronius hyodon was reported a few times in literature, but it was neglected in systematic studies. We analyzed several specimens of Cuvieronius hyodon from the Americas and recognized that immature individuals had lower incisors during very early post-natal developmental stages. Subsequently, these are lost and lower incisors alveoli close during later developmental stages, before maturity. Moreover, for the first time in a formal cladistic analysis of non-amebelodontine trilophodont gomphotheres, Rhynchotherium and Cuvieronius were recovered as sister-taxa. Among several non-ambiguous synapomorphies, the presence of lower incisors diagnoses this clade. We recognize that the presence of lower incisors in Cuvieronius and Rhynchotherium is an unique case of taxic atavism among the Elephantimorpha, since these structures are lost at the origin of the ingroup. The rediscovery of the lower incisors in Cuvieronius hyodon, their ontogenetic interpretation and the inclusion of this feature in a revised phylogenetic analysis of trilophodont gomphotheres brought a better understanding for the evolutionary history of these proboscideans.

Mesoamerica is the geographic region between northern Mexico and southern Panama. This region shows specific cultural and biological features, both presently and in the past. The proboscideans (Mammalia, Proboscidea) that inhabited the region in a time range from middle Miocene to late Pleistocene are outlined. Three families (Elephantidae, Gomphotheriidae, and Mammutidae) and six genera currently are known from the region. The systematic position of the genus Stegomastodon is unresolved, whether monophyletic or paraphyletic, and it may include two genera, Stegomastodon sensu stricto and Haplomastodon. The other five genera recognized for the region are Gomphotherium (1 species), Rhynchotherium (3 species), Cuvieronius (3 species), Mammut (1 species), and Mammuthus (2 species). The Great American Biotic Interchange played an important role for the migration of the proboscideans into South America. The association between proboscideans and humans in Mesoamerica has been explored, but there is only evidence of an association with mammoths exists.

Two new records of gomphotheriid proboscideans, one identified as Rhynchotherium and the other as Cuvieronius, are reported in Mexico. Both records are in the southwesternmost points of their known distributional range. The remains of both genera consist of molars and tusks. Their measurements were compared with data available from the literature and collection specimens. The molar index of Rhynchotherium shows statistical differences between m2 and M2, and m3 and M3. However, differences between the m3 from both genera are not statistically significant, despite slight morphological differences. This suggests that metric and morphological information should be included for a reliable identification of isolated molars and, if available, any other data of the associated tusk. All known records relating to both genera suggest that they found southwestern Mexico favorable for use as a dispersal corridor to South America, likely due to the region's tropical or subtropical climate. However, some distri...

The discovery of an Early-Middle Pleistocene continental vertebrate fauna from El Salvador is here reported. These fossils provide information about a poorly studied geographic area that played an important role during the Great American Faunal Interchange. The fauna is dominated by numerous remains of the proboscidean Cuvieronius tropicus and probably represents the largest known concentration of this genus in America. A number of living taxa are first recorded as fossils in El Salvador, including Crocodylus acutus, previously unknown as a fossil elsewhere. Hesperotestudo crassiscutata, Glyptotherium arizonae, Palaeolama, Hemiauchenia cf. H. seymourensis and Equus conversidens, are recorded for the first time in Central America. The new locality also holds the oldest record of Mazama, and the southernmost records of Glyptotherium arizonae and Equus conversidens. At least 17 taxa are represented in the new site, constituting the richest Central American continental vertebrate locality hitherto known.

Documentamos aquí por primera vez los mamíferos del Pleistoceno tardío de la localidad de El Hatillo en la península de Azuero en Panamá, originalmente reportado por C. L. Gazin en 1957. Los siguientes taxa están presente: Hoplophorinae?, Glyptotherium floridanum, Eremotherium laurillardi, Paramylodon harlani, Equus conversidens, Platygonus sp., Odocoileus sp., Mixotoxodon larensis y Cuvieronius hyodon. Este es un conjunto característico de mamíferos del Pleistoceno Tardío de Centroamérica destacado por fósiles de Eremotherium en asociación con fósiles de Mixotoxodon y Equus. Me refiero a este tipo de asociación como montaje EME y postulo que la mayoría de estos montajes de Centroamérica son de edad del Pleistoceno Tardío. Los montajes EME representan una fauna mixta de pasteadores y ramoneadores que eran muy común en toda Centroamérica durante uno o más de los fines interestadiales del Pleistoceno. Late Pleistocene mammals from the El Hatillo locality on the Azuero Peninsula in Panama, originally reported by C. L. Gazin in 1957, are documented here for the first time. The following taxa are present: Hoplophorinae?, Glyptotherium floridanum, Eremotherium laurillardi, Paramylodon harlani, Equus conversidens, Platygonus sp., Odocoileus sp., Mixotoxodon larensis and Cuvieronius hyodon. This is a characteristic assemblage of late Pleistocene mammals from Central America that is dominated by fossils of Eremotherium in association with fossils of Mixotoxodon and Equus. I refer to such associations as EME assemblages and posit that most of these assemblages from Central America are of Late Pleistocene age. EME assemblages represent a mixed fauna of grazers and browsers that was common across Central America during one or more of the Late Pleistocene interstadials.

Five proboscidean species have been found in Paleoindian sites from North to South America: two open-country adaptations, Mammuthus columbi and Cuvieronius tarijensis, two woodland and riparian forms, Mammut americanum and Mammuthus jeffersonii, and one tropical savanna species, Haplomastodon chimborazi. Their value in biostratigraphy and as ecological index fossils is discussed with particular emphasis on the Central Mexican Paleoindian sites.

Fossiliferous middle Pleistocene sediments of the Tarija basin of southern Bolivia contain a classic Ensenadan land-mammal fauna. New carbon isotopic data reported here for 50 specimens of the grazing mammals Equus (horse) and Cuvieronius (mastodon), documented from eight stratigraphic levels at Tarija, vary significantly in the δ13C values of their teeth. The pattern of variation appears to reflect the proportion of C3 and C4 grasses eaten during colder (more C3) and warmer (more C4) times. Within age limits set by associated magnetostratigraphy, the cold periods can be correlated with particular even-numbered stages in the marine oxygen-isotope record, and the warm periods can be correlated with odd-numbered stages. The oldest fossil teeth analyzed from the Tarija section can thereby be assigned to stage 29, and the youngest to stages 17 or 15, that is; the teeth range in age from about 1.1 myr to as young as 0.7 myr. Based on correlation of the upper part of the Tarija beds to the isotopic stages, the upper limit of the Ensenadan land-mammal age is between 0.7 and 0.6 myr, which is younger than stated in most previous studies.

Mammoths and mastodons are common in Pleistocene deposits, yet these proboscideans and many other animals disappeared suddenly ≈10,000 years ago. In this study, we reconstruct the diets of proboscideans and associated mammals through isotopic analysis of carbonate in tooth enamel apatite in order to test nutritional hypotheses for late Pleistocene extinction. We analyzed specimens from six sites in Florida, ranging from full glacial (>21,000 BP) to late glacial (14,750 to 10,000 BP) age. The oxygen isotope composition of mammalian apatite covaries with meteoric water composition, which in turn varies with climate. Consequently, oxygen isotope analysis can be used to assess the potential for time-averaging or mixing of specimens from different geographic regions within fossil assemblages. The carbon isotope composition of an herbivore is controlled by the isotopic composition of the plants that it ingests. Carbon isotope analysis reveals that mastodons ate chiefly C3 plants, presumably trees, shrubs and herbs, whereas mammoths consumed chiefly C4 grass. Several nutritional hypotheses for late Pleistocene extinction entail the assumption that extinct taxa had specialized diets. The resource partitioning and focused feeding preferences of Florida's proboscideans corroborate this assumption, but they do not, in themselves, prove that nutritional stress was the cause of the late Pleistocene extinction.

Fossil mammals are known from 41 localities of Pleistocene age in Costa Rica. Most of these mammals are proboscideans referable to the gomphothere Cuvieronius hyodon. One occurrence of Haplomastodon waringi is known, and Mammuthus columbi from Costa Rica is the southernmost record of Mammuthus in Central America. Less well documented are occurrences of megatheriid and mylodontid ground sloths and glyptodonts. Equus is poorly known from several localities, and the toxodont Mixotoxodon larensis is well known from a single locality. Canis latrans and Tapirus sp., cf. T. terrestris are new records for the Pleistocene of Costa Rica. None of the Costa Rican Pleistocene mammals is directly associated with human artifacts or remains. No endemic taxa of mammals are known from Costa Rica; most are of North American origin. The Costa Rican Pleistocene record is from numerous localities, but consists of one or a few taxa of large mammals and no small mammals at each site, indicating a probable bias towards p...

The exceedingly rich middle Pleistocene mammalian fauna from the classic Ensenadan Tarija basin in southern Bolivia contains a diversity of medium to large-bodied herbivores consisting of both endemic (†Toxodontia, †Litopterna, Xenarthra) and immigrant (Rodentia, Proboscidea, Perissodactyla, and Artiodactyla) taxa. In order to characterize feeding ecology and niche differences, a suite of morphological characters was measured for each of 13 species of herbivorous mammals from the Pleistocene of Tarija; these were combined with carbon isotopic results from tooth enamel. (The Xenarthra were excluded from this study because they lack tooth enamel.)Several different bivariate and multivariate combinations of characters can be used to characterize the feeding adaptations, niches, and guild composition of the Tarija mammalian herbivores. During the Pleistocene the browsing guild in the Tarija basin is interpreted to include the tapir (Tapirus tarijensis), extinct llama (Palaeolama weddelli), peccary (Tayassusp.), and deer (Hippocamelussp.). The mixed-feeding guild included two horse species (Hippidion principaleandOnohippidium devillei), litoptern (Macrauchenia patachonica), and capybara (Neochoerus tarijensis). The grazing guild included the numerically dominant horse (Equus insulatus), two lamine species (Lama angustimaxillaand cf.Vicugna, provicugna), notoungulate (Toxodon platensis), and gomphothere proboscidean (Cuvieronius hyodon). The grazing guild has the widest range of body sizes relative to the two other guilds. Closely related sympatric species within the Equidae and Camelidae differentiate their niches from one another using a combination of body size, feeding ecology, and probably local habitat. Most of the paleoecological reconstructions resulting from this combined morphological and isotopic analysis corroborate previous studies based primarily on morphology; there are, however, some notable surprises.

Medium- to large-bodied mammalian herbivores are taxonomically diverse and comprise a large component of the highly fossiliferous Neogene terrestrial sedimentary sequence from Florida. In order to reconstruct herbivore paleodiets and community paleoecology as well as understand climate and ecosystem change, 112 pristine tooth enamel samples were analyzed for at least 12 families and 26 genera within the orders Proboscidea, Perissodactyla, and Artiodactyla. These samples are from 17 localities and seven time horizons of late Miocene (Hemphillian) through late Pleistocene (Rancholabrean) age and between about 9.5 Ma to 100,000 yrs ago. Stable carbon isotopic analyses indicate that during the late Miocene local terrestrial communities and herbivore paleodiets consisted exclusively, or predominantly, of C3 plants, e.g., mean tooth enamel δ13C value is −11.9%o from the 9.5 Ma level. During the latest Miocene-early Pliocene (after 7 Ma) there is a shift in mean δ13C values of tooth enamel to −7.0%o (4....

New mastodon finds collected in the Province of Carchi (Northern Ecuador) give further evidence that in South America Haplomastodon and Cuvieronius are monospecific. Of all the specific names referred to the genus Haplomastodon, only chimborazi must be considered valid as it alone was based on significant diagnostic material. As far as the genus Cuvieronius is concerned a new type species, Cuvieronius tarijensis, is proposed as the type specimen of Cuvieronius hyodon likely belongs to Haplomastodon.