Browsing by Autor "Russell K. Engelman"

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    New mammal faunal data from Cerdas, Bolivia, a middle-latitude Neotropical site that chronicles the end of the Middle Miocene Climatic Optimum in South America
    (Taylor & Francis, 2016) Darin A. Croft; Alfredo A. Carlini; Martín R. Ciancio; Diego Brandoni; Nicholas E. Drew; Russell K. Engelman; Federico Anaya
    We provide new and revised identifications of mammals from the early middle Miocene (Langhian age, Colloncuran South American Land Mammal Age [SALMA]) of Cerdas, Bolivia. We also formally name a new typothere notoungulate, Hegetotherium cerdasensis, sp. nov., that can be distinguished by the absence of an external talonid sulcus on m3 and its small size (15–25% smaller than Hegetotherium mirabile). We refer several typothere specimens from Nazareno, Bolivia, to H. cerdasensis, which suggests that the two sites are of similar age. We report the first sparassodont and astrapothere remains from Cerdas. Sparassodont remains include an associated basicranium and mostly complete mandible; the species appears to represent a new, small-bodied borhyaenoid. Astrapothere remains consist of many tooth fragments from a new species of the subfamily Uruguaytheriinae. A partial sloth dentary from Cerdas likely pertains to the subfamily Megatheriinae and is the first report of the family Megatheriidae from the site. A newly discovered peltephilid armadillo specimen includes a partial articulated carapace that supports recognition of the Cerdas taxon as a new species. The two dasypodids of Cerdas (one Euphractini, one Eutatini) represent two new species closely related to undescribed species from the late middle Miocene (Serravallian age, Laventan SALMA) of Quebrada Honda, Bolivia. The mammals of Cerdas indicate that (1) the middle latitudes (southern tropics) contributed significantly to the diversity of Miocene mammal communities in South America; and (2) the Middle Miocene Climatic Optimum was a key factor in the differentiation of South American mammal assemblages.Citation for this article: Croft, D. A., A. A. Carlini, M. R. Ciancio, D. Brandoni, N. E. Drew, R. K. Engelman, and F. Anaya. 2016. New mammal faunal data from Cerdas, Bolivia, a middle-latitude Neotropical site that chronicles the end of the Middle Miocene Climatic Optimum in South America. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1163574.
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    New palaeothentid marsupials (Paucituberculata) from the middle Miocene of Quebrada Honda, Bolivia, and their implications for the palaeoecology, decline and extinction of the Palaeothentoidea
    (Taylor & Francis, 2016) Russell K. Engelman; Federico Anaya; Darin A. Croft
    Paucituberculatan marsupials, particularly members of the family Palaeothentidae, were important components of South American mammal communities during much of the Cenozoic. However, after the late early Miocene, palaeothentid remains are rare in the fossil record, and the group is last recorded at late middle Miocene sites in Colombia, Bolivia and possibly Argentina. Here, we describe new specimens of palaeothentids from one of these late middle Miocene sites, Quebrada Honda, Bolivia, which include: (1) the first described lower dentitions of Acdestis maddeni, which exhibit distinctive features such as a greatly elongated paracristid and a single-rooted m4; (2) the first described late middle Miocene palaeothentines, representing two new species of Palaeothentes, P. serratus sp. nov. and P. relictus sp. nov., distinguished from other species of Palaeothentes by the presence of an anterobasal cingulid and reduced anterior trigonid crest, among other features; and (3) remains of a third new species, Chimeralestes ambiguus gen. et sp. nov., distinguished from other palaeothentids by its combination of a labially positioned cristid obliqua, reduced m4, and sharply curved entocristid. Phylogenetic and palaeoecological analyses show that Quebrada Honda palaeothentids were taxonomically and morphologically diverse and likely spanned a wide range of ecological niches. Combined with the wide geographical distribution of palaeothentoids during the late middle Miocene, this suggests that the disappearance of these marsupials was preceded by an abrupt rather than gradual decline in taxonomic and ecological diversity as well as geographical range.http://zoobank.org/urn:lsid:zoobank.org:pub:DA7E10BA-7203-4F5A-A3AB-F0E7352B101C
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    New Specimens of Acyon myctoderos (Metatheria, Sparassodonta) from Quebrada Honda, Bolivia
    (Asociación Paleontológica Argentina, 2014) Russell K. Engelman; Federico Anaya; Darin A. Croft
    Despite being the dominant group of South American mammalian carnivores for much of the Neogene, most post-early Miocene sparassodonts (Metatheria) are poorly known. Here, we describe new specimens of the hathliacynid sparassodont Acyon myctoderos Forasiepi et al. from the middle Miocene locality of Quebrada Honda, Bolivia, including a juvenile specimen that preserves the first known hathliacynid DP3. This specimen is unique among sparassodonts in preserving both upper and lower deciduous premolars and suggests that hathliacynids may have differed from borhyaenoid sparassodonts in having simultaneous eruption of M3 and m4 rather than M4/m4. Another specimen from Quebrada Honda tentatively assigned to A. myctoderos preserves the first known long bones (femur, tibia) of this genus, allowing us to estimate its body mass (13–17.5 kg) based on postcranial data. These new specimens document further morphological and ontogenetic variation within A. myctoderos as well as the Sparassodonta as a whole.
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    The flora, fauna, and paleoenvironment of the late Middle Miocene Quebrada Honda Basin, Bolivia (Eastern Cordillera, Central Andes)
    (Elsevier BV, 2024) Caroline A. E. Strömberg; Beverly Z. Saylor; Russell K. Engelman; Angeline M. Catena; Daniel I. Hembree; Federico Anaya; Darin A. Croft
    Miocene ecosystem change in the Central Andes is not well understood because of a dearth of well-dated fossil sites from the region. The late Middle Miocene (∼13–12 Ma) Quebrada Honda Basin (QHB) in southern Bolivia (22° S) helps fill this gap and provide vital insights into Neotropical paleoenvironments . The site is among the best-characterized Middle Miocene terrestrial vertebrate sites of South America and has a robust temporal, spatial, and lithostratigraphic framework for analyzing its sedimentary facies, fossils, and paleoenvironment. Here, we present new plant silica (phytolith) assemblage data from the QHB as well as new analyses of QHB faunal data. Phytolith assemblage data indicate two broad vegetation types : one suggestive of more open habitats (≥ 60% presumably open-habitat grasses) and the other of more closed habitats (typically dominated by potential bamboos and other forest indicators). Compositional overlap suggests that these vegetation types represent distinct plant communities within a broader biome that lacks an exact modern analog among studied Neotropical vegetation; however, it was likely akin to modern Neotropical semi-deciduous/dry forest to wooded savanna. No clear temporal or spatial trends in phytolith composition are evident in the QHB, and the same is broadly true for QHB vertebrates based on analyses of 872 identified specimens. Abundances of some mammals (certain rodents, armadillos, turtles, and the notoungulate Hemihegetotherium ) vary slightly among well-sampled local areas and stratigraphic intervals, paralleling phytolith assemblage data suggesting local heterogeneity. The new floral and faunal data, combined with previous studies of paleosols , ichnofossils , ectothermic vertebrates, and mammal ecological diversity of the QHB, point to a mosaic landscape in lowland subtropical to tropical conditions that did not change substantially during the preserved interval. These results add critically to our understanding of Neotropical landscape evolution , suggesting that the QHB had not undergone substantial uplift, counter to recent reconstructions of Andean orogeny in the Eastern Cordillera. • The Middle Miocene Quebrada Honda Basin (QHB) preserves vital fossil data from the Neotropics. • We integrate new reconstructions of QHB plant and animal communities. • Vegetation was heterogeneous, spanning dry forest to wooded savanna. • The diverse mammal fauna varied little through time or across the basin. • The Central Andes were still at relatively low elevation 12 million years ago. Velizar Simeonovski made the reconstruction of H. trilobus