Browsing by Subject "Neogene"

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  • Pushkina, Diana (University of Helsinki, 1997)
  • Bernor, Raymond L.; Kaya, Ferhat; Kaakinen, Anu; Saarinen, Juha; Fortelius, Mikael (2021)
    Nearly five decades ago Berggren and Van Couvering proposed an Old World "Hipparion Datum" wherein a North American Hipparion extended its range across Eurasia and Africa as an "instantaneous prochoresis" populating the Old World. Four decades ago Woodburne and Bernor examined European and North African hipparion assemblages and proposed a number of distinct hipparion lineages, sharply departing from the mono-generic paradigm of previous work. Through the 1980s until now, hipparion systematic studies have delineated multiple superspecific groups of hipparions. Herein, we define 10 recognizable genus-rank Eurasian and African taxa delineating their chronologic occurrences, geographic extent and where data exists, their body mass and paleodietary preferences. Our study supports the current interpretation that a species of North American Cormohipparion extended its range into the Old World in the early late Miocene. Regional first occurrences of Cormohipparion are recognized in the Potwar Plateau, Pakistan and Sinap Tepe, Turkey 10.8 Ma. The slightly derived lineage Hippotherium is recorded earlier in the Pannonian C of the Vienna Basin, 11.4-11.0 Ma marking the chronologic "Hipparion" Datum at the lower boundary of Mammal Neogene (MN) Unit 9. Within MN 9, 11.2-9.9 Ma, Cormohipparion underwent a minor diversification whereas Hippotherium diversified in Central and Western Europe and China and Sivalhippus (S. nagriensis) originated in the Indian Subcontinent. Whereas Cormohipparion did not survive into the late Vallesian, MN10 (9.9-8.9 Ma), Hippotherium and Sivalhippus did and the Cremohipparion and Hipparion s.s. lineages originated. During the early and middle Turolian (MN11-12, 8.9-6.8 Ma) Hippotherium, Sivalhippus, Cremohipparion and Hipparion persisted and new lineages, Eurygnathohippus, Plesiohipparion, Baryhipparion and Shanxihippus originated. An initial extinction interval occurred at the end of the Miocene, MN13 (6.8-5.3 Ma) wherein all but one endemic species of Hippotherium, H. malpassi (Italy), Hipparion and several species of Cremohipparion became extinct. Lineage and species reduction continued across the MioPliocene boundary so that by the beginning of the Pliocene (MN14, 5.3 Ma) only African species of Eurygnathohippus, Chinese Plesiohipparion houfenense and Proboscidipparion sinense remained. The later Pliocene (MN15-16, ca. 5.0-2.5 Ma) documents the persistence of endemic Chinese Baryhipparion insperatum, modest diversification of African Eurygnatohippus spp. and Chinese Plesiohipparion and Proboscidipparion spp. Eurygnathohippus made a limited geographic extension into the Indian subcontinent during MN16, whereas Pleisohipparion and Proboscidipparion extended their ranges into Eurasia during MN15 and MN16. The latest occurring hipparions are Proboscidipparion sinense at 1.0 Ma in China and Eurygnathohippus cornelianus in Africa 300 kg), with the smaller forms being predominately grass feeders and larger ones being mixed feeders. Decreased hipparion lineage and species diversity in the Pliocene was accompanied by increased average body size and hypsodonty probably in response to more seasonal Eurasian and African environments. There is no evidence that hipparions ever adapted to cold and dry Old World Pleistocene environments.
  • Morales-Garcia, Nuria Melisa; Saila, Laura K.; Janis, Christine M. (2020)
    Savanna-like ecosystems were present at high latitudes in North America during much of the Neogene. Present-day African savannas, like the Serengeti, have been proposed to be modern analogs of these paleosavannas, particularly those from the middle Miocene of the Great Plains region of the United States. Both these extant and extinct savannas contain a preponderance of artiodactyl (even-toed ungulate) species; however, the taxonomic composition of each fauna is different. While present-day African savannas are dominated by ruminants (primarily bovids), the Neogene savannas of North America were dominated by a diversity of both camelid and non-bovid ruminant families. This study provides a quantitative test of the similarity of the artiodactyl faunas of the North American Neogene paleosavannas to those of the modern-day African savannas. A correspondence analysis of ecomorphological features revealed considerable overlap between modern and fossil faunas. The morphospace occupation of the extinct North American ruminants falls within that of the African bovids. Some of the extinct camelids also fall within this same morphospace, but many do not, perhaps indicating an environmental difference such as greater aridity in Neogene North America. The diversity and disparity of artiodactyl faunas through the Neogene of North America changed along with changing temperatures and precipitation regimes. The taxonomic and ecomorphological diversity of the Serengeti ruminant fauna is statistically comparable to those North American paleofaunas occurring during or immediately after the Middle Miocene Climatic Optimum (MMCO), but the later, more depauperate faunas are no longer comparable. This study quantitatively analyzes artiodactyl communities as they changed with the cooling and drying trend seen during the Neogene.