Germán Mariano Gasparini

Formation of the Isthmus of Panama

Independent evidence from rocks, fossils, and genes converge on a cohesive narrative of isthmus formation in the Pliocene. The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.

Records and Stratigraphical Ranges of South American Tayassuidae (Mammalia, Artiodactyla)

Tayassuidae represent one of the first mammalian immigrants that entered South America during the “Great American Biotic Interchange.” However, the exact moment of its arrival for the first time in South America is controversial. Three genera are recognized in South America: Platygonus, Catagonus, and Tayassu. This paper aims to: (1) review the paleontological record of the South American Tayassuidae and update it; and (2) discuss its geographical and statigraphical distribution pattern in South America. The genus Platygonus (middle Pliocene to early Pleistocene) is registered in Argentina, Uruguay, Colombia, and Bolivia; Catagonus (late Pliocene? to Recent) in Argentina, Uruguay, Brazil, and Bolivia; and Tayassu (middle Pleistocene to Recent) in Argentina, Uruguay, and Brazil. Platygonus and Catagonus have adaptations to dry and relatively open environments; in contrast, Tayassu is adapted mainly to humid climates and woodland and forest environments. The faunal changes that took place since the middle-late Pliocene could have been strongly influenced by climate. Open and arid environments developed during the glacial cycles, allowing the latitudinal expansion of Platygonus and Catagonus. Considering ecological and anatomical information, it is possible to infer that Platygonus species were replaced by those of Catagonus since the middle Pleistocene, probably due to a reduction of the open environments to which Platygonus species were better adapted. The alternation of these mainly arid or semiarid, cold conditions with warmer and more humid short pulses would have allowed the posterior expansion of Tayassu species. According to phylogenetic analysis and chronological as well as geographical evidence, Platygonus and Catagonus represent two Tayassuidae lineages that originated in North America and then migrated to South America. This migration would have occurred on more than one occasion and with different taxa. Evidence indicates that Tayassu represents a lineage that differentiated in the Southern Hemisphere and then migrated to North America.

A review of the Quaternary Tayassuidae (Mammalia, Artiodactyla) from the Tarija Valley, Bolivia

Three genera of Tayassuidae are recognized in South America: Platygonus Le Conte, 1848, Catagonus Ameghino, 1904 and Tayassu Fischer, 1814. This study provides the first systematic review of the Pleistocene tayassuids yet reported from Bolivia. The richest records of the family in South America derived from central-eastern Argentina and southern Brazil. Catagonus stenocephalus (Lund in Reinhardt, 1880) is documented for the first time in Bolivia, significantly extending the geographic distribution of this species in South America. We cannot confirm the validity of Platygonus tarijensis (Ameghino, 1904), but accept its generic allocation. Both taxa show adaptations to arid or semi-arid and relatively open environments, which is consistent with the palaeoenvironmental conditions previously proposed for the Tarija Valley. The veracity of other records of the family from Bolivia cannot be confirmed.

Tayassu pecari (Link, 1795) (Mammalia, Cetartiodactyla): comments on its South American fossil record, taxonomy and paleobiogeography

Tayassu pecari is widely distributed across the Neotropical region, from northern Argentina to south-eastern Mexico. However, its fossil record is scarce; it is recorded since the middle Pleistocene to Holocene in Argentina, Brazil and Uruguay. This paper aims to: (1) update the systematic synonymy of this species; (2) review and update its geographic chronologic distribution and provide a new Lujanian record of Tayassu pecari in Buenos Aires Province and (3) discuss the paleoenvironmental and paleobiogeographical implications of this record. Considering the quantitative analysis performed, the fossil here recorded clearly integrates the group of Tayassu pecari. This specimen corresponds to the first record of Tayassu pecari in the central-northern region of the Buenos Aires Province. During Late Pleistocene, Tayassu pecari was distributed southern to its recent range, probably evidencing different paleoenvironment conditions. This species is the better adapted peccary to tropical and subtropical rainforests, but may also be present in arid environments. Consequently, Tayassu by itself is insufficient to infer the prevailing environmental conditions. However, according to the fauna associated with the specimen described here, it is possible to infer an open or semi-open and arid or semi-arid environment for the central-northern Buenos Aires region by Late Pleistocene times.

Phylogenetic Systematics of Peccaries (Tayassuidae: Artiodactyla) and a Classification of South American Tayassuids

Tayassuidae is a family of pig-like Artiodactyla restricted to the New World. Despite its rich fossil history, they have received less attention from a taxonomic and phylogenetic perspective when compared to the Old World pigs, Suidae. In this study, we performed a computer assisted phylogenetic analysis using morphological and molecular data including fossil and extant Tayassuidae, using parsimony and Bayesian approaches. We recovered the monophyly of the family Tayassuidae, confirming previous proposals, as well as the monophyly of the subfamilies Hesperhyinae and Tayassuinae, and the genus Platygonus, which we placed in a new taxon of tribe level. The three living peccaries and a number of fossil species belong to a new, tribe level, monophyletic group. The genus Catagonus comes out as paraphyletic, leading us to propose to restrict the generic name to the type species, C. metropolitanus, and a new taxonomic arrangement for the remaining species previously included in it, revalidating the genera Brasiliochoerus and Parachoerus, and describing a new genus, Protherohyus, gen. nov.

The Chacoan peccary, Catagonus wagneri (Mammalia, Tayassuidae), in the late Pleistocene (northern Uruguay, South America): paleoecological and paleobiogeographic considerations

Catagonus wagneri has the most restricted geographical distribution among extant Tayassuidae and inhabited semi-arid thorny forests of dry Chaco in Paraguay, Bolivia and Argentina. Until now, C. wagneri has only been recorded in archaeological, pre-Hispanic deposits from the Santiago del Estero Province, Argentina. A new partially complete skull from the Sopas Formation (Late Pleistocene; Uruguay) is identified as C. wagneri. This is the only fossil record of the species which extends its biochron until the late Pleistocene, and the first one substantially far from its current range; the first fossil record of the species in Uruguay; the most complete fossil material of the species; and it provides relevant ecological and climatic information. According to the ecological and climatic available information of C. wagneri, the presence of this mammal in the late Pleistocene of northern Uruguay indicates a warm climate and arid to semi-arid environments. Even though not associated with the fossil remains of C. wagneri, some mammals included in the sedimentary levels of the Sopas Formation also suggest arid to semi-arid environments. Climatic changes, in particular in the late Pleistocene and Holocene, could be invoked to explain modifications of its geographic range.http://zoobank.org/ECF04BCF-8246-4F11-AAB8-5FAA9F437BDA

Microvertebrates preserved in mammal burrows from the Holocene of the Argentine Pampas: a taphonomic and paleoecological approach

Abstract Microvertebrates are a major component of many assemblages recovered from the Quaternary of the Argentine Pampas. The main goal of this paper is to analyse the taphonomic history of a Holocene microfossil bonebed, recovered from the infilling of a burrow. Evidences suggest the plains vizcacha Lagostomus maximus as the putative producer of the burrow. The assemblage includes individuals belonging to different taxa of mammals (marsupials and rodents) and reptiles (snakes). Taphonomic features suggest that the accumulation inside the burrow was related to flooding processes in the plain. The burrow was a natural trap that favoured the accumulation and preservation of remains corresponding to individuals from different sources. According to the taphonomic evidence, some individuals (Lagostomus maximus, Lestodelphys halli and Serpentes indet.) died inside the burrow, whereas others (Microcavia australis, Reithrodon auritus and Ctenomys sp.) died outside the burrow, and after a time of being exposed on the surface their remains were transported by surface run-offs into the burrow. The record of Lestodelphys halli and Serpentes indet. in the burrow produced by Lagostomus maximus could be related to a circumstantial use. Mammal burrows are a significant taphonomic mode for the late Cenozoic of the Argentine Pampas.

Fossil peccaries of Late Pleistocene/Holocene (Cetartiodactyla, Tayassuidae) from underwater caves of Serra da Bodoquena (Mato Grosso do Sul State, Brazil)

Abstract New records of Catagonus stenocephalus and Tayassu pecari are reported from the karst of Serra da Bodoquena, located at a south-western portion of Brazil near the border with Paraguay. Skull and lower jaw fragments at different stages of mineralisation were retrieved from two limestone underwater caves, Japonês and Nascente do Formoso, associated with clay and sand deposits with no retrievable stratigraphy. C14 dating of fossil mammals from these caves was attempted, but so far no success was achieved, but the inferred age for the associated paleofauna of these caves is Late Pleistocene and Holocene. The morphology of these fossil peccaries, from the most south-western known population in Brazil, is detailed and paleoecological implications are considered.

Continental Vertebrates During the Marine Isotope Stage 3 (MIS 3) in Argentina

Paleontological sites in Argentina with continental vertebrates corresponding to the Marine Isotope Stage 3 (MIS 3) interval are scarce or poorly known. This situation is mainly due to the lack of absolute ages for Pleistocene fossil remains or their bearing sediments that would allow the verification of the chronology established for this interval. However, a few isolated evidences show that continental vertebrates responded to the abrupt temperature changes that characterized the MIS 3 (Heinrich colder events and Dansgaard–Oeschger warmer events). Up to date, continental vertebrate remains of this age have been found mainly in Buenos Aires province, but also in a few sites of northeastern Argentina (such as Entre Rios, Corrientes, Formosa and Chaco provinces). In Buenos Aires province: (1) Paso Otero, in the Rio Quequen Grande valley, evidence of warmer and more humid conditions were found in sediments dated in 37,800 ± 2300 radiocarbon years before present (RCYBP); (2) Mar del Sur, General Alvarado County, coastal marine sediments with continental mammals were dated in 25,700 ± 800 and 33,780 ± 1200 RCYBP; (3) Balneario Saldungaray, in the Rio Sauce Grande valley, Tornquist County, gastropods associated with mammal remains were dated in 32,300 ± 1800 and 27,500 ± 670 RCYBP; (4) Los Pozos, Marcos Paz County, sediments dated between 29,000 and 33,000 RCYBP are associated with remains of mammals , birds, reptiles and amphibians; (5) San Pedro, San Pedro County, sediments bearing vertebrate fauna have two OSL datings of 37,626 ± 4198 and 41,554 ± 3756 years B.P. (YBP). In Entre Rios province, Rio Ensenada valley, Diamante Department, some levels of the Tezanos Pinto Formation with OSL datings between 9000 and 35,000 YBP yielded remains of grazer megamammals and other taxa characteristic of the modern Patagonian Domain. In the province of Corrientes, Arroyo Toropi, Bella Vista, vertebrate remains dated with OSL from 36,000 to 52,000 YBP show a clear taxonomic change in response to climatic fluctuations. In Formosa province, Rio Bermejo, Villa Escolar sediments of the Fortin Tres Pozos Formation, bearing vertebrate fauna have an OSL age of 58,160 ± 4390 YBP. In the province of Chaco, Charata locality, gastropods associated with mammal remains were dated between 22,000 and 27,000 RCYBP. A larger amount of absolute datings of the bearing sediments and especially taxon dates are needed to determine more accurately the response of the fauna to the climate changes characteristic of MIS 3.

A Quaternary very young juvenile Tapirus Brisson, 1762 (Mammalia, Perissodactyla) from a cave deposit in northern Brazil: taxonomy and taphonomy

During fieldworks carried out from 2009 to 2013 in Aurora do Tocantins (northern Brazil), three isolated deciduous teeth of Tapirus were recovered. Those fossils come from a sedimentary deposit of presumed Late Pleistocene–early Holocene age in a karstic cave. This contribution aims to present a new locality of fossil Tapirus from northern Brazil, describe for the first time deciduous fossil teeth for South American Tapirus and evaluate the taphonomic aspects of those fossils. The specimens probably belong to the same individual due to there are no repeated teeth and they have the same wear pattern. Furthermore, the crowns of those teeth show no evidence of abrasion produced by transport. However, some abrasion is observed on the borders of the pulp chamber of teeth. These polishing are probably resulting of a very short transport (parautochthonous). These specimens are the only record of Tapiridae in Gruta do Urso cave; due to correspond to isolated and deciduous teeth, its identification to species level was not possible. There is not yet clear evidence that may indicate the kind of death of the individual studied here.