SALMA Research Articles

Proterotheriids and macraucheniids (Litopterna: Mammalia) from the Pampa Castillo Fauna, Chile (early Miocene, Santacrucian SALMA) and a new phylogeny of Proterotheriidae

Here we describe the litopterns, a diverse and temporally long-ranging clade of South American native ‘ungulates’, of the early Miocene Pampa Castillo fauna from the Galera Formation in the Andean Cordillera of southern Chile, and present a new phylogeny of Proterotheriidae, the most speciose litoptern subgroup. Two proterotheriids occur at Pampa Castillo: Thoatherium, the northernmost and first record of this taxon outside Santa Cruz Province, Argentina, and Picturotherium, known previously solely from the Pinturas Formation of north-western Santa Cruz Province. Macraucheniidae are represented at Pampa Castillo by Theosodon. Collectively, these three taxa suggest an early Miocene (Santacrucian South American Land Mammal ‘Age’ (SALMA)) age for the fossil mammal fauna from Pampa Castillo, reinforcing previous biochronological interpretations. Results of a comprehensive phylogenetic analysis identify Megadolodus molariformis as the earliest-diverging member of Proterotheriidae, a name for which we propose a stem-based definition. Few multi-species proterotheriid genera were recovered as monophyletic in our analysis. Three ‘anisolambdid’ litopterns, initially assumed to represent outgroups, instead nest deeply within Proterotheriidae, implying long ghost lineages. The phylogenetic placement of the four proterotheriids from the middle Miocene La Venta fauna of Colombia sheds light on the poorly understood long-term isolation of tropical faunas and their degree of exchange with high-latitude regions. Santacrucian SALMA assemblages in Patagonia are notable in that older localities preferentially produce earlier-diverging proterotheriids. Older sites are also marked by a mix of brachyodont and hypsodont taxa, whereas younger sites yield strictly hypsodont forms, supporting the notion of increasing aridity in Patagonia through this interval. Proterotheriids alone cannot be used to discriminate between an early or late Santacrucian age for the Pampa Castillo fauna, but the brachyodonty of Picturotherium suggests a humid climate and closed habitats.

Macraucheniidae and Proterotheriidae (Mammalia, Litopterna) from Quebrada Fiera (Late Oligocene), Mendoza Province, Argentina

In this contribution we present new specimens of Litopterna recovered during the last decade in Quebrada Fiera (Mendoza Province, Argentina), whose fossiliferous sediments, currently recognized as the base of Agua de la Piedra Formation, are assignable to Late Oligocene (Deseadan South American Land Mammal Age). Two remains mentioned in the first publication on this locality were neither detailed nor described, and they have not been located in the corresponding repository. The new material consists of postcranial fragmentary remains (astragali, calcaneum, and metapodials) of Macraucheniidae (Cramaucheniinae) and an incomplete upper molar (M3) of Proterotheriidae (Proterotheriinae). These few remains of litopterns contrast with the abundance of notoungulates at Quebrada Fiera. A comparative study was carried out with material from Patagonia (Argentina) and taxa recorded in Bolivia and Peru for the same temporal interval. The specimens of Cramaucheniinae are assigned to Coniopternium andinum and the molar of Proterotheriinae to cf. Lambdaconus suinus. This contribution allows us to extend the geographical range of Coniopternium, filling the gap between the Patagonian and lower latitude localities (Bolivia and Peru) in which this genus was found. The record of L. suinus in Quebrada Fiera expands the geographical range of this species outside from Patagonia.

The Allemann collection from the Santa Cruz Formation (late early Miocene), Argentina, in Zurich, Switzerland

One of the best-known faunal assemblages that characterizes the past ecosystems from South America comes from the Santa Cruz Formation in Argentina. This assemblage is formed by an endemic fauna, which included ground sloths, glyptodonts, native ungulates, terror birds (phorusrhacids), among others. The Santacrucian South American Land Mammal Age is dated 18.0–15.6 Ma, late early Miocene. Current curatorial efforts revealed a large collection of over 1100 fossil remains from the Santa Cruz Formation, donated in 2007 to the Paleontological Museum, University of Zurich, Switzerland. The fossils were brought to Switzerland in the late 1880s by Theodor Allemann, an engineer and amateur collector. The collection includes skulls, isolated teeth, mandibles, and isolated postcranial elements. Postcranials are mainly represented by astragali, calcanei, and osteoderms. The study of the remains allowed us to recognize 20 families of mammals, one of birds, and one of amphibians: Abderitidae, Palaeothentidae (Paucituberculata); Hathliacynidae (Sparassodonta); Dasypodidae, Peltephilidae, and Glyptodontidae (Cingulata); Megatheriidae and Megalonychidae (Tardigrada); Astrapotheriidae (Astrapotheria), Protherotheriidae and Macraucheniidae (Litopterna); Toxodontidae, Homalodotheriidae, Hegetotheriidae and Interatheriidae (Notoungulata); Dasyproctidae, Dinomyidae, Neoepiblemidae, Chinchillidae, Erethizontidae, Echimyidae and Eocardidae (Rodentia); Phorusrhacidae (Cariamiformes); and Calyptocephalellidae (Anura). Among them, we identified 28 genera and 9 species. Reference to the previous work on the Santa Cruz fauna and the good preservation of the material allow us to achieve taxonomic resolution in the identifications. We discuss the potential usefulness of this collection for studying the paleobiology of specimens/species of this fauna.

FLOODPLAIN TAPHONOMIC MODE OF EARLY MIOCENE VERTEBRATES OF SOUTHERN PATAGONIA, ARGENTINA

A continental assemblage of fossil mammals from the Santa Cruz Formation (early Miocene, Burdigalian) recovered from the coast of the Santa Cruz Province (Anfiteatro locality), Argentina, was evaluated taphonomically. Due to its stratigraphic position and age (∼ 17.5 Ma), the fossiliferous level corresponds to the lower section of the Estancia La Costa Member (lower part of the Santa Cruz Formation). The Anfiteatro assemblage (Santacrucian South American Land Mammal Age) is dominated by mammals, but some birds and carnivore coprolites were also recorded. The recorded taphonomic features and the sedimentological interpretation suggest that the bone remains were preserved in a floodplain related to a fluvial system influenced by volcaniclastic input. The assemblage was interpreted as a result of death of mammals over a short period of time. The residence time of carcasses on the surface was variable. Although most bones were quickly buried, the exposure was sufficiently long for the disarticulation and scattering of different skeletal components and the agency of other processes (e.g., trampling, weathering). The loss of skeletal elements is linked to the action of water flows generated in the plain, during overbank floods or rainfalls, which mobilized those elements more susceptible to transport. After burial, the specimens were affected by diagenetic processes (e.g., soil corrosion, infilling, impregnation, deformation). The taphonomic evaluation of the Anfiteatro locality provides a framework for the analysis of other fossil assemblages with similar features worldwide.

Chlorocyon phantasma, a Late Eocene Borhyaenoid (Mammalia: Metatheria: Sparassodonta) from the Los Helados Locality, Andean Main Range, Central Chile

Sparassodont metatherians were the dominant terrestrial mammalian predators during South America's long Cenozoic isolation. This group's early fossil record is very poor, however, particularly for the late Eocene and early Oligocene. Here, we describe a new sparassodont, Chlorocyon phantasma, gen. et sp. nov., based on a specimen from Los Helados, a new locality within the Abanico Formation of the Andean Main Range of central Chile. New 40Ar/39Ar dates at Los Helados bracketing the fossil-bearing level constrain the age of this specimen to 37–36 Ma (late Eocene), indicating that this new taxon likely pertains to the Mustersan South American Land Mammal “Age.” Chlorocyon is the first Paleogene sparassodont reported from Chile and the first sparassodont described from the Abanico Formation. Distinctive features, including a p3 with an anterior edge that is more curved than the posterior edge and the lack of a hypoconulid on m4, suggest that Chlorocyon is a borhyaenoid closely related to Pharsophorus or Plesiofelis, although much smaller. Chlorocyon represents a welcome addition to the sparse record of late Eocene sparassodonts and indicates that the diversity of non-proborhyaenid borhyaenoids prior to the late Oligocene was greater than previously thought.

New well-preserved craniodental remains ofSimomylodon uccasamamensis(Xenarthra: Mylodontidae) from the Pliocene of the Bolivian Altiplano: phylogenetic, chronostratigraphic and palaeobiogeographical implications

Fossil remains of extinct terrestrial sloths have been discovered in numerous localities throughout the Americas, but knowledge of these animals remains poor in the tropical latitudes in comparison with the austral ones. Even where Pliocene mylodontine sloths are known from North and South America, well-preserved craniodental remains are extremely rare, hindering reliable assessment of their taxonomic assignment and phylogenetic affinities. Here, new craniodental remains of Simomylodon uccasamamensis, from the latest Miocene–Pliocene of the Bolivian Altiplano, are described and compared with those of other Neogene Mylodontinae from South and North America. The resulting morphological observations, combined with morphometric analyses, permit reliable differentiation among these moderate-sized Miocene–Pliocene mylodontids. Simomylodon uccasamamensis appears to be the smallest Pliocene mylodontine, and it is closely related phylogenetically to the late Miocene species Pleurolestodon acutidens. Simomylodon uccasamamensis is also an endemic taxon of the Andean highlands during the Pliocene, with a continuous chronological range extending throughout the Montehermosan, Chapdamalalan and (early) Marplatan South American Land Mammal Ages. This terrestrial sloth may have found its ideal ecological conditions in the Bolivian Altiplano, during a span of time falling between the important South American Late Miocene–Pliocene faunal turnover and the Great American Biotic Interchange around the Pliocene–Pleistocene transition.

The Interatheriinae (Mammalia, Notoungulata) of the Friasian sensu stricto and Mayoan (middle to late Miocene), and the fossils from Cerro Zeballos, Patagonia, Argentina

The middle to late Miocene Friasian sensu stricto, Colloncuran and Mayoan South American Land Mammal Ages (SALMAs) were established based on the mammals recovered from the Río Frías, Collón Curá and Río Mayo formations, respectively (southern Argentina and Chile). Records of Interatheriinae (Notoungulata) from these sediments have been known since the first contributions of Ameghino and Roth, but most of this material has only been superficially revised or is almost unstudied. Based on these old collections and new interatheriine records from Cerro Zeballos (Chubut Province), we improve the diagnosis of Caenophilus tripartitus, describe new and peculiar characters for this taxon, consider Epipatriarchus bifidens as Protypotherium cf. colloncurensis, and propose Epipatriarchus as a junior synonym of Protypotherium. In turn, the holotype of Epipatriarchus innexus is here identified as the mesotheriid Trachytypotherium sp. Therefore, only two genera of Interatheriinae, Protypotherium and Caenophilus, are recognized in the Friasian sensu stricto and Mayoan. We identify Protypotherium cf. endiadys and a probable new species of Protypotherium for the Friasian sensu stricto, P. cf. colloncurensis and Caenophilus tripartitus for the Mayoan, and C. tripartitus, P. colloncurensis and P. cf. endiadys for Cerro Zeballos. An extended phylogenetic analysis is performed, including species from low latitudes and new data for P. colloncurensis and Caenophilus tripartitus, with the latter recovered as a sister taxon to Miocochilius federicoi. Both Protypotherium and Miocochilius are recovered as paraphyletic. The updated information we present provides a better knowledge of Interatheriinae for the middle to late Miocene of southern South America.

A new teiid lizard of the genus Callopistes Gravenhorst, 1838 (Squamata, Teiidae), from the Lower Miocene of Argentina

Although squamates are commonly found in Cenozoic South American deposits, most findings correspond to fragmentary cranial materials or isolated vertebrae. Among the known South American vertebrate fossil localities, the lower section of the Chichinales Formation (Early Miocene, Colhuehuapian South American Land Mammal Age [SALMA]), in Paso Córdoba Protected Natural Area, Río Negro Province, Argentina, recently yielded an almost complete skull of a previously unknown teiid lizard. Here, we provide a detailed description of this new fossil, based on stereoscopic and high-resolution X-ray computed tomography (CT scan) analyses. Our phylogenetic analysis recovered the new fossil within the monophyletic genus Callopistes, as the sister group of the fossil C. bicuspidatus from upper Miocene–lower Pliocene sediments (Montehermosan SALMA) of the Monte Hermoso Formation. The new species antedates the oldest previously known fossil record of the genus by at least 14 Ma, providing a minimum age of origin for the genus of approximately 20.1 Ma (based on recent revisions of the Cenozoic fossil record of SALMA). The current distribution of the two known extant species of Callopistes and the locality from which the new taxon was recovered indicate that this genus had a much broader distribution in the past that included cis-Andean areas of Patagonia during the Miocene. Our phylogenetic results further suggest that Tupinambis uruguaianensis should be allocated to the genus Dracaena.http://zoobank.org/urn:lsid:zoobank.org:pub:452C7D2A-6819-4488-9C28-1020EBD71F91SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Quadros, A. B., P. Chafrat, and H. Zaher. 2018. A new teiid lizard of the genus Callopistes Gravenhorst, 1838 (Squamata, Teiidae), from the Lower Miocene of Argentina. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1484754.

New Paleogene Notohippids and Leontiniids (Toxodontia; Notoungulata; Mammalia) from the Early Oligocene Tinguiririca Fauna of the Andean Main Range, Central Chile

Here we describe three new notohippid notoungulate species from the early Oligocene-aged Tinguiririca Fauna (Tinguirirican SALMA), recovered from volcaniclastic deposits of the Abanico Formation in the central Chilean Andes, two of which are known from material sufficiently complete to warrant formal naming. These include Eomorphippus bondi, sp. nov., a form of moderate size distinguished by hypsodont incisors and cheekteeth, as well as distinctive proportions of the upper incisors. A closely similar but more diminutive form is described as Eomorphippus neilopdykei, sp. nov. A third previously unrecognized notohippid in the Tinguiririca Fauna, best represented by a large, low-crowned, lower incisor battery, almost certainly represents a new taxon, but remains too fragmentary to warrant naming now. We also propose a new binomial for a previously named notohippid, ?Eomorphippus pascuali, originally described from Gran Barranca in Argentina but which is now also recorded in Chile. This taxon, here named Rosendo pascuali, is markedly less hypsodont than E. bondi and E. neilopdykei and retains lingual cingula on at least p4-m1. As least one leontiniid notoungulate occurs in the Tinguiririca Fauna, Termastherium flacoensis, gen. et sp. nov., best represented by two partial upper cheek toothrows and a tentatively referred maxillary fragment bearing three deciduous teeth. Collectively, description of these new fossils from Termas del Flaco, Chile helps to more fully characterize the Tinguiririca Fauna, facilitating correlation and comparison to other South American land mammal faunas spanning the Eocene-Oligocene transition.

New caviomorph rodents from the late Oligocene of Salla, Bolivia: taxonomic, chronological, and biogeographic implications for the Deseadan faunas of South America

Caviomorph rodents have been an important component of South American mammal faunas at least since the Oligocene. Those from the Deseadan South American Land Mammal Age (SALMA; late Oligocene) have been exhaustively studied because they are considered key to understanding the evolution of South American rodents. Deseadan faunas are widely distributed from northern Peru to central Patagonia, with those from Salla (Bolivia) and Cabeza Blanca (Argentinean Patagonia) being the most diverse. Recent studies of Deseadan rodents at some localities in high (Cabeza Blanca, Punta Nava, Scarritt Pocket) and low (Contamana) latitudes revealed greater taxonomic diversity. However, at middle latitudes, Salla has not received the same attention, despite being exceptional in terms of the abundance and high-quality preservation of specimens. The aim of this work is to report new caviomorph rodents from Salla, and to discuss their systematic and palaeobiogeographical implications in the context of the South American Deseadan caviomorph assemblages. We describe two new genera (†Lapazomys gen. nov. and †Cholamys gen. nov.) and five new species (†Migraveramus lavocati sp. nov., †Sallamys woodi sp. nov., †Lapazomys hartenbergeri sp. nov., †Protosteiromys pattersoni sp. nov. and †Cholamys tetralophodonta sp. nov.). These include the first erethizontids and the oldest Cavioidea sensu stricto for middle and low latitudes. The increase in the number of species corroborates the existence of an important rodent diversification already evidenced in the late early/early late Oligocene. In addition, the new rodents lessen the degree of endemism of the Salla rodent fauna proposed in previous papers. We interpret that the differences among Deseadan assemblages from low, middle and high latitudes are due essentially to climatic, historical and local environmental conditions, whereas diachronism seems less important in the modelling of faunas.http://zoobank.org/urn:lsid:zoobank.org:pub:A8A04332-12E1-4966-9807-47B66554718E

Rediscovering a forgotten rodent of Patagonia and its phylogenetic implications

Cephalomyidae is an enigmatic caviomorph ‘family’ recorded in the Deseadan–Colhuehuapian SALMAs (South American Land Mammal Age) of Bolivia and Argentina. The validity and phylogenetic relationships of this group remain unconfirmed. Litodontomys chubutensis is one of the most poorly known cephalomyids, recorded only by a partial mandible with the complete dental series. Here we present a new specimen of Litodontomys from the same Deseadan locality as the holotype (Cabeza Blanca, Chubut, Argentina). It is a more complete and better preserved specimen from a larger and older individual. A phylogenetic analysis, performed to test the position of the genus and the validity and relationships of the family Cephalomyidae, recovered Litodontomys as the sister taxon of Cephalomys and confirmed the monophyly of the clade for the first time in an updated matrix and broader phylogenetic context.

Two new macraucheniids (Mammalia: Litopterna) from the late middle Miocene (Laventan South American Land Mammal Age) of Quebrada Honda, Bolivia

ABSTRACT We describe two new macraucheniid litopterns from the late middle Miocene (ca. 13 Ma) Quebrada Honda Fauna of southern Bolivia. The holotype of ‘Theosodon’ arozquetai, sp. nov., is a partial cranium preserving RI2–M3 and LP1–M3, elements of the hind limb, and two metapodials. An upper cheek tooth series is also referred to this species. The holotype of Llullataruca shockeyi, gen. et sp. nov., is a mandible preserving nearly the entire lower dentition. A dentary, several upper teeth, and a variety of postcranial elements are also referred to this species. Two specimens from the slightly older locality of Cerdas, Bolivia, are assigned to L. cf. shockeyi. A phylogenetic analysis recovers ‘T.’ arozquetai as sister to Theosodon spp., and we provisionally refer it to that genus pending its revision. Llullataruca shockeyi forms a polytomy with three late Oligocene–early Miocene ‘cramaucheniines’ and the later-diverging macraucheniids. The body mass of ‘T.’ arozquetai is estimated at 80.8–116.2 kg, slightly smaller than early Miocene T. garretorum. Llullataruca shockeyi is among the smallest known macraucheniids based on dental dimensions and is estimated at 35.3–54.6 kg. Theosodon' arozquetai and L. shockeyi are the first well-characterized macraucheniids from the middle Miocene, and the latter species demonstrates that relatively early-diverging lineages persisted at least 7 million years longer in tropical latitudes than they did in Patagonia. http://zoobank.org/urn:lsid:zoobank.org:pub:D26BB67B-D8E1-4D36-9552-4391874CF69C SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: McGrath, A. J., F. Anaya, and D. A. Croft. 2018. Two new macraucheniids (Mammalia: Litopterna) from the late middle Miocene (Laventan South American Land Mammal Age) of Quebrada Honda, Bolivia. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1461632.

Patagonian Eocene Archaeopithecidae Ameghino, 1897 (Notoungulata): systematic revision, phylogeny and biostratigraphy

AbstractThe Archaeopithecidae is a very poorly known group of native ungulates from the Eocene of Patagonia (Argentina), whose alpha taxonomy has remained obscure since Ameghino’s times. It is traditionally considered as a family representative of the Casamayoran (middle Eocene) South American Land Mammal Age, and is thought to be morphologically close to the notopithecids. After studying >200 specimens from several institutions, including all the type specimens, a taxonomic overestimation is established. Out of the six species considered originally as archaeopithecids,Archaeopithecus rogeriAmeghino, 1897 is here recognized as the only valid name and species; subsequent synonymies are proposed and previous taxonomic hypotheses discarded. This exhaustive revision has permitted improving the knowledge ofA.rogeriand, for the first time, it has revealed many craniodental characters, which allow amending its diagnosis and differentiating this taxon from other Eocene notoungulates.Archaeopithecus rogeriis a small-sized taxon characterized by its complete and rooted dentition, which is relatively higher than that of other contemporaneous short-crowned notoungulates and shows ontogenetic variation in size and morphology. The body mass range ofA.rogeri(1.4–2.5 kg) is comparable to those of notopithecids and some small hegetotheriids. The phylogenetic analysis showsA.rogeriis not directly related to any family within Notoungulata, appearing into a polytomy, as a basal taxon of typotherians. The biochronological range ofA.rogeriis adjusted to Vacan (middle Eocene) through Barrancan subages (late middle Eocene); older (Riochican, late early Eocene) and younger (Mustersan, late Eocene) records remain to be confirmed.

New Anatomical Data on Pyrotherium (Pyrotheriidae) from the Late Oligocene of Mendoza, Argentina

Fil: Cerdeno Serrano, Maria Esperanza. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales; Argentina

Cricket oviposition trace fossils in palaeosols and their stratigraphic significance: The South American Palaeosol Ichnofossil Ages (SAPIAs)

The first insect trace fossil in palaeosols attributed to the oviposition of crickets is represented by openings composed of two to four, but usually three, perforations with a tripartite pattern. This pattern is compatible with the cross section of the distal ovipositor of some crickets. The new ichnotaxon Bellosichnus tripartitus igen. isp. nov. represents a novel architectural design among insect trace fossils in palaeosols. It may reflect true ovipositions or the behavior of testing soil with the ovipositors performed by crickets. In accordance, this trace fossil would be indicative of the surface soil horizon. Bellosichnus tripartitus is abundant in the lower section of the Sarmiento Formation (middle Eocene Casamayoran Age) and it is almost absent before and after this interval in other terrestrial successions of Patagonia. It is a trace fossil with high stratigraphic significance. Bellosichnus tripartitus and other insect trace fossils in palaeosols with similar stratigraphic significance comprise several assemblages, which are representative of different ages along the Cenozoic of southern South America. Such assemblages are typical of particular ages that are named herein South American Palaeosol Ichnofossil Ages (SAPIAs). The SAPIAs run in parallel with the South American Land Mammal Ages (SALMAs). The SAPIAs would be useful to make predictions not only on ages, but also on possible mammal faunas and palaeoenvironments in understudied palaeontological localities.

New age constraints for early Paleogene strata of central Patagonia, Argentina: Implications for the timing of South American Land Mammal Ages

Fil: Krause, Javier Marcelo. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Museo Paleontologico Egidio Feruglio; Argentina. Universidad Nacional del Sur. Departamento de Geologia; Argentina

Occurrence of Toxoplasma gondii antibodies in lowland tapirs maintained ex situ in Brazil and Paraguay

ABSTRACT: Lowland Tapir ( Tapirus terrestris ) is the second largest South American land mammal. It is strictly herbivorous and its exposure to Toxoplasma gondii should be indicative of environmental contamination by oocysts.In the present study antibodies to T. gondii in 47 Brazilian tapirs maintained ex situ in 10 Brazilian and in one Paraguayan institution were sought in serum samples by the modified agglutination test (MAT ≥25). None of the animals presented clinical signs during the study. From 47 animals 35 (74.5%) were positive with titers of 25 in 8, 50 in 6, 100 in 12, 200 in 5, 400 in 1 and 800 in 3. One animal had samples collected on twice, and 19 were born in captivity. There was no association between occurrence of T. gondii antibodies and gender, and positive animals were reported in all institutions. The high occurrence of seropositive tapirs born ininstitutions (54.3%) confirmed the high exposure of these mammals to T. gondii in captivity. Only two cases ofabortion were reported, but it was not possible to correlate these abortions to T. gondii infection.

A New South American Paleogene Land Mammal Fauna, Guabirotuba Formation (Southern Brazil)

The Paleogene vertebrate-bearing sites of Brazil are restricted to few formations such as Maria Farinha (Late Cretaceous-early Paleocene), Itaborai (early Eocene), Entre-Corregos (Eocene-Oligocene), and Tremembe (late Oligocene-early Miocene). A new Paleogene fauna is reported from an outcrop of the Guabirotuba Formation located at Curitiba, Parana State, southern Brazil. The Guabirotuba Formation is a stratigraphic unit of the Curitiba Basin, which belongs to the Cenozoic continental rift system of southeastern Brazil, a predominantly half-graben and horst system. The sedimentary facies indicate a fluvial distributary depositional system associated with floodplain, generated under humid climate conditions alternating with drier periods. This new Paleogene fauna, here named the Guabirotuba Fauna, has invertebrate and vertebrate taxa, including mammals (Cingulata, Notoungulata, Astrapotheria, and Metatheria). The fossil remains of seven armored xenarthrans are identified, including the description of a new species and genus named Proeocoleophorus carlinii. The Guabirotuba ungulates are assigned to Interatheriidae, Oldfieldthomasiidae, and Astrapotheria. The metatherian mammals are represented by a sparassodont, a palaeothentoid, and an argyrolagoid. This new mammalian fauna preliminarily suggests a late middle Eocene age (Barrancan South American Land Mammal Age) for the Guabirotuba Formation.

Extinction of South American sparassodontans (Metatheria): environmental fluctuations or complex ecological processes?

AbstractSparassodontans are a diverse but now extinct group of metatherians that were apex predators in South America during most of the Cenozoic. Studying their decline has been controversial mainly due to the scarcity of the fossil record, and different methodological approaches have led to contradictory hypotheses. In an effort to explore questions about their extinction, we developed a novel multi‐model statistical approach to analyse all of the currently available data at a continental scale. Using multiple regression analysis and new advances in beta diversity analysis, we used all currently available fossil data at a continental scale to test four competing hypotheses to account for the decline of sparassodontans: competition with placental carnivorans, competition with avian phorusrhacids, non‐competitive ecological interactions, and environmental fluctuations. Our results show that the sparassodontan extinction was a gradual process with species disappearing throughout the Cenozoic. Multiple regression analysis supported non‐competitive ecological interactions as the best extinction model. Native South American ungulates, African migrants (caviomorph rodents and platyrrhine primates) and didelphimorphians were the groups with the highest statistical significance. Sparassodontan beta diversity increased between South American Land Mammal Ages after the Paleocene–Eocene boundary. Our results demonstrate that ecological modelling techniques illuminate aspects of extinction processes whilst mitigating the limitations of the fossil record. Our study suggests that non‐competitive ecological interactions could have been the main driver for sparassodontan extinction rather than, as commonly assumed, a result of competition and/or abiotic fluctuations.

Late Oligocene caviomorph rodents from Contamana, Peruvian Amazonia

AbstractThe Deseadan South American Land Mammal Age (late Early Oligocene – Late Oligocene) attests to a time of great diversification in the caviomorph rodent fossil record. Nevertheless, Deseadan rodent‐bearing localities in Neotropical lowlands are few and poorly known. Here we describe the rodent assemblages from two Late Oligocene localities, near Contamana, Loreto, Peru. Seven taxa are new to science: Palaeosteiromys amazonensis gen. et sp. nov., Plesiosteiromys newelli gen. et sp. nov., Loretomys minutus gen. et sp. nov., Scleromys praecursor sp. nov, Ucayalimys crassidens gen. et sp. nov., Chambiramys sylvaticus gen. et sp. nov. and Chambiramys shipiborum gen. et sp. nov. These rodent faunas show that caviomorphs were relatively diverse in Peruvian Amazonia during the Late Oligocene, with the co‐occurrence of at least three extant superfamilies: Erethizontoidea, Octodontoidea and Chinchilloidea. Additionally, they mark the earliest known occurrences of Scleromys, of a small erethizontid closely related to Microsteiromys and of an adelphomyine closely reminiscent of Ricardomys (all taxa previously restricted to Miocene localities thus far). They also document a form potentially related to Eosallamys (previously known from around the Eocene–Oligocene transition at Santa Rosa in Peruvian Amazonia). Finally, the geographical range of Adelphomyinae and of Deseadomys is widely expanded to the lower latitudes of South America for the Deseadan interval. The latter elements, in addition to the record of a very primitive species of Scleromys, suggest the absence of palaeogeographical and palaeoenvironmental barriers within the southern cone of South America before the Oligocene–Miocene transition.