 Subjects -> PALEONTOLOGY (Total: 46 journals)
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- Using machine learning to classify extant apes and interpret the dental
morphology of the chimpanzee-human last common ancestor
Abstract: Machine learning is a formidable tool for pattern recognition in large datasets. We developed and expanded on these methods, applying machine learning pattern recognition to a problem in paleoanthropology and evolution. For decades, paleontologists have used the chimpanzee as a model for the chimpanzee-human last common ancestor (LCA) because they are our closest living primate relative. Using a large sample of extant and extinct primates, we tested the hypothesis that machine learning methods can accurately classify extant apes based on dental data. We then used this classification tool to observe the affinities between extant apes and Miocene hominoids. We assessed the discrimination accuracy of supervised learning algorithms when tasked with the classification of extant apes (n=175), using three types of data from the postcanine dentition: linear, 2-dimensional, and the morphological output of two genetic patterning mechanisms that are independent of body size: molar module...
PubDate: Fri, 24 Aug 2018 00:00:00 +000
- Late Cretaceous endemic shallow-marine gastropod genera of the northeast
Pacific: biodiversity and faunal changes
Abstract: Endemic genera of shallow-marine gastropods in the Cretaceous Northeast Pacific Subprovince (NEP), extending from Alaska to northern Baja California Sur, Mexico, are tabulated and discussed in detail for the first time. None are known in Lower Cretaceous or Cenomanian strata, but 43 genera, nearly two-thirds of which are neogastropods, are recognized in Upper Cretaceous strata. Their first appearance was at the beginning of the Turonian, which coincided with the warmest time of the Cretaceous and one of its highest sea-level stands. Fourteen new subtropical endemic genera appeared then, and 10 (71%) were neogastropods. Tethyan-influenced thermophilic mollusks (nerineid, acteonellid, neritid, and cypraeoidean gastropods, as well as rudistid bivalves) were present. A turnover at the Turonian/Coniacian boundary occurred when cooler waters migrated southward, resulting in the subtropical endemics being abruptly and nearly completely replaced by 10 warm-temperate new endemic neogastropods,...
PubDate: Wed, 22 Aug 2018 00:00:00 +000
- New insights into Late Triassic dinosauromorph-bearing assemblages from
Texas using apomorphy-based identifications
Abstract: The Upper Triassic Dockum Group of Garza County, Texas (lower, middle, and upper Cooper Canyon Formation) captures the radiation of Triassic non-marine tetrapods by preserving a variety of Late Triassic taxa from the southwestern United States. Our understanding of the vertebrate assemblage from these strata largely comes from a single site, the Post Quarry (lower Cooper Canyon Formation), with previous research documenting a variety of temnospondyls, sphenodontians, non-archosauriform archosauromorphs, and archosauriforms including a phytosaur, three species of aetosaurs, a poposauroid, a rauisuchid, a crocodylomorph, and several dinosauromorphs. To more completely reconstruct the vertebrate assemblage of the Dockum Group of Garza County we use an apomorphy-based approach to identify morphologically similar disarticulated and fragmentary elements from a variety of localities that span the entire Cooper Canyon Formation (Norian-Rhaetian), allowing assignments from the large clade...
PubDate: Sat, 21 Jul 2018 00:00:00 +000
- A new Calliovarica species (Seguenzioidea: Chilodontidae) from the Eocene
of Oregon, USA: Persistence of a relict Mesozoic gastropod group in a
unique forearc tectonic setting
Abstract: A new, enigmatic chilodontid gastropod with distinctive periodic varices is described as Calliovarica oregonensis. It is based on ten specimens from slope deposits of the early late Eocene Nestucca Formation on the coastal Cascadia margin of present day Oregon, U.S.A. It is the last appearance of a Mesozoic group of epifaunal basal gastropods with periodic varices. It is the third species in a Cenozoic genus previously known only from the early Eocene Lodo Formation in California and the late Paleocene to early Eocene Red Bluff Tuff in New Zealand. The type species, C. eocensis, is refigured to clarify the nature of the axial varices as well as a terminal thickening and flaring of the apertural lip immediately following deposition of the final varix. Detailed preservation of microstructure in the nacreous layers of crushed and disintegrating shell fragments demonstrates the value of collecting material typically left behind in the field. Calliovarica oregonensis...
PubDate: Wed, 18 Apr 2018 00:00:00 +000
- Western Association of Vertebrate Paleontologists Annual Meeting
Abstract: The 2018 Program with s volume for the Western Association of Vertebrate Paleontologists 52nd Annual Meeting held at Dixie State University, St. George, Utah, USA.
PubDate: Tue, 20 Mar 2018 00:00:00 +000
- The fauna and chronostratigraphy of the middle Miocene Mascall type area,
John Day Basin, Oregon, USA
Abstract: The Mascall fauna is a well-known middle Miocene (Barstovian) mammalian assemblage in the Pacific Northwest. It has been collected for over 100 years and collecting intensity has increased since the establishment in 1975 of a national monument enclosing the type area of the formation. Despite its importance to biostratigraphy, biogeography of Barstovian taxa, and paleoecological studies, the fauna at the type locality has not been taxonomically examined in more than 50 years. Evaluation and classification of the stratigraphy of the Mascall Formation (Bestland et al. 2008) has prompted a faunal revision in order to place taxa within the new stratigraphic framework. Here we report on the fauna from the type area of the Mascall Formation in central Oregon, and conclude that 20 taxa are new to the fauna, and several taxa previously assigned to distinct species are synonymized. We also place specimens and taxa within a robust stratigraphic framework, calibrated with new U-Pb radioisotopic...
PubDate: Mon, 15 Jan 2018 00:00:00 +000
- The first report of Toxochelys latiremis Cope, 1873 (Testudines:
Panchelonioidea) from the early Campanian of Alabama, USA
Abstract: Toxochelys latiremis Cope, 1873 is currently thought to be one of the oldest members of the clade originating from the last common ancestor of all extant species of marine-adapted turtles (Chelonioidea). Fossil material of this species has been reported from numerous lower Campanian marine formations across North America; however, reported occurrences have been conspicuously absent from the upper Santonian-to-lower Campanian Mooreville Chalk of Alabama and Mississippi, USA, the type stratum for the only other valid species within the genus, Toxochelys moorevillensis Zangerl, 1953. The apparent absence of T. latiremis from the Mooreville Chalk, and from the southern expanse of the Mississippi Embayment, has made T. latiremis one of the few outliers in previously proposed paleobiogeographic models for marine turtles in the Late Cretaceous Western Interior Seaway. This absence also confounded attempts at reconciling the distribution and phylogeny...
PubDate: Fri, 12 Jan 2018 00:00:00 +000
- Cenozoic Marine Formations of Washington and Oregon: an annotated
catalogue
Abstract: An annotated list of Cenozoic, fossiliferous marine formations from western Oregon and Washington State, U.S.A., and southwestern Vancouver Island, British Columbia, Canada, has been assembled. This chart is a product of the Eastern Pacific Invertebrate Communities of the Cenozoic (EPICC) Thematic Collections Network project that is digitizing over 1.6 million Cenozoic marine invertebrate fossils from the eastern Pacific margin (Alaska to Chile) housed in the network’s museums. The chart includes formation names currently recognized by Geolex, the U.S. Geological Survey’s National Geologic Map Database. Also included on the chart are prior names, original authors, biozonations, ages from the International Chronostratigraphic Chart (ICC), and references for the most recent age calls.
PubDate: Fri, 12 Jan 2018 00:00:00 +000
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