A history of land mammals in the western hemisphere

Scott, W. B.

doi:10.5962/bhl.title.159241

Cited by 85 publications

(70 citation statements)

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“…Hypsodonty was originally viewed as an adaptation to grazing in grassland ecosystems (e.g., Kovalevsky, 1874;Scott, 1937;Stebbins, 1981; see review of Damuth and Janis, 2011).…”

Section: Faunasmentioning

confidence: 99%

Quasi-static Eocene–Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling

Kohn

Strömberg

Madden

et al. 2015

Palaeogeography, Palaeoclimatology, Palaeoecology

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New local/regional climatic data were compared with floral and faunal records from central Patagonia to investigate how faunas evolve in the context of local and global climate. Oxygen isotope compositions of mammal fossils between c. 43 and 21 Ma suggest a nearly constant mean annual temperature of 16±3 °C, consistent with leaf physiognomic and sea surface studies that imply temperatures of 16-18 °C. Carbon isotopes in tooth enamel track atmospheric  13 C, but with a positive deviation at 27.2 Ma, and a strong negative deviation at 21 Ma. Combined with paleosol characteristics and reconstructed Leaf Area Indices (rLAI), these trends suggest aridification from 45 Ma (c. 1200 mm/yr) to 43 Ma (c. 450 mm/yr), with quasi-constant MAP until at least 31 Ma, and increases to ~800 mm/yr by 21 Ma. Comparable MAP through most of the sequence is consistent with relatively constant floral compositions, rLAI, and leaf physiognomy. Abundance of palms reflects relatively dry-adapted lineages and greater drought tolerance under higher p CO2 . Pedogenic carbonate isotopes imply low p CO2 = 430±300 ppmv at the initiation of the Eocene-Oligocene climatic transition. Arid conditions in Patagonia during the late Eocene through Oligocene provided dust to the Southern Ocean, enhancing productivity of silicifiers, drawdown of atmospheric CO 2 , and protracted global cooling. As the Antarctic Circumpolar Current formed and Earth cooled, wind speeds increased across Patagonia, providing more dust in a positive climate feedback. High tooth crowns (hypsodonty) and evergrowing teeth (hypselodonty) in notoungulates evolved slowly and progressively over 20 Ma after initiation of relatively dry environments through natural selection in response to dust ingestion. A Ratchet evolutionary model may explain protracted evolution of hypsodonty, in which small variations in climate or dust delivery in an otherwise static environment drive small morphological shifts that accumulate slowly over geologic time.

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“…Hypsodonty was originally viewed as an adaptation to grazing in grassland ecosystems (e.g., Kovalevsky, 1874;Scott, 1937;Stebbins, 1981; see review of Damuth and Janis, 2011).…”

Section: Faunasmentioning

confidence: 99%

Quasi-static Eocene–Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling

Kohn

Strömberg

Madden

et al. 2015

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…Dentition Scott (1913) wrote that Astraponotus had complete premolar series. Schlosser (1923) interpreted that the dental formula was apparently complete.…”

Section: Dentarymentioning

confidence: 99%

New remains of Astraponotus (Mammalia, Astrapotheria) and considerations on Astrapothere cranial evolution

2010

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Astraponotus Ameghino, 1901, the only valid Mustersan (late Eocene) astrapothere, typifies the Ameghino's ''Capas Astraponotenses''. This taxon is traditionally interpreted as structurally ancestral to all the OligoceneMiocene astrapotheriids. However, it was imperfectly known: only isolated teeth and very partial mandibles have hitherto been described. In this contribution we provide the first description of the skull, mandible, and complete dentition of Astraponotus based on new materials from the Gran Hondonada and other Mustersan localities in central Patagonia, Argentina. The features observed in the dentition of Astraponotus are intermediate between the Casamayoran (middle Eocene) and the Oligocene-Miocene astrapotheres in the degree of hypsodonty, reduction of the dental formula, and development of accessory occlusal elements. Concordantly, the skull retains some plesiomorphies, also observed in Trigonostylops, whereas the auditory region and the basicranium are much closer to those of Parastrapotherium, Astrapotherium, and Granastrapotherium. On the other hand, the skull of Astraponotus differs from all known astrapotheres by the disproportioned height and narrowness of the braincase, the extreme reduction of the nasals and the premaxillaries, the absence of anteorbital rim, and the reduction of the frontal region. Some of these features represent cranial specializations exactly opposite to that of Astrapotherium. These characters look astonishingly derived for an Eocene astrapothere, suggesting that extreme cranial specializations occurred independently during the evolution of the order, and that Astraponotus represents a distinctive lineage from that of Astrapotherium and other Miocene forms.Keywords Astraponotus Á Astrapotherium Á Trigonostylops Á Eocene Á Patagonia Kurzfassung Astraponotus Ameghino, 1901, der einzige valide Astrapothere aus dem Mustersan (spätes Eozän), diagnostiziert die ''Capas Astraponotenses'' von Ameghino. Dieses Taxon wurde traditionell als strukturell ursprünglich im Vergleich zu allen Oligozänen-Miozänen Astrapotheriiden angesehen. Allerdings war es nur unzulänglich bekannt: nur isolierte Zähne und teilweise erhaltene Dentalia wurden bisher beschrieben. Hier beschreiben wir zum ersten Mal den Schädel, Unterkiefer und die gesamte Bezahnung von Astraponotus auf der Basis von neuen Materialien aus der Gran Hondonada und anderen Mustersanen Lokalitäten im zentralen Patagonien. Die in der Bezahnung beobachteten Merkmale von Astraponotus sind intermediär zwischen Astrapotheren des Casamayor (mittleres Eozän) und des Oligozän-Miozän in Hinsicht auf Hypsodontie, Reduktion der Zahnformel und der Entwicklung zusätzlicher Okklusionsstrukturen.Electronic supplementary material The online version of this article (

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“…First appearances of Artiodactyla, Perissodactyla, and true Primates were taken to mark the beginning of the succeeding Eocene epoch. Sinclair (1912) and Scott (1913) were at the forefront of modern acceptance of the Paleocene as a distinct epoch.…”

Section: History Of Studymentioning

confidence: 99%

Mammalian responses to climate change at the Paleocene-Eocene boundary: Polecat Bench record in the northern Bighorn Basin, Wyoming

Gingerich¹

2003

Causes and Consequences of Globally Warm Climates in the Early Paleogene

136

141

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The Paleocene-Eocene transition in North American land-mammal faunas is well documented on the south side of Polecat Bench and in surrounding badlands of northwestern Wyoming. Here a rich fossil record is known from a stratigraphic section with an established geomagnetic polarity time scale and medium-to high-resolution carbon and oxygen isotope records. The Paleocene-Eocene carbon isotope excursion (CIE) and temperature maximum (PETM) associated with greenhouse warming are both represented, starting at ca. 55 Ma and lasting ∼ ∼86 k.y., during the transition from Paleocene to Eocene epochs and from Clarkforkian to Wasatchian land-mammal ages. Attention is focused on transient dwarfing of earliest Wasatchian (Wa-0) mammals during the CIE-PETM interval and on more lasting changes in generic composition and diversity. Faunal changes lagged initiation of the CIE by some 13 and 22 k.y., consistent with the idea of a stepped and pulsed response to climate change. Body size dwarfing in Wa-0 mammals cannot be explained as a response to temperature alone, and elevated atmospheric CO 2 probably played an important role. 463 Gingerich, P.D., 2003, Mammalian responses to climate change at the Paleocene-Eocene boundary: Polecat Bench record in the northern Bighorn Basin, Wyoming, in Wing, S.

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A history of land mammals in the western hemisphere

Cited by 85 publications

References 0 publications

Quasi-static Eocene–Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling

Quasi-static Eocene–Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling

New remains of Astraponotus (Mammalia, Astrapotheria) and considerations on Astrapothere cranial evolution

Mammalian responses to climate change at the Paleocene-Eocene boundary: Polecat Bench record in the northern Bighorn Basin, Wyoming

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