abderitid marsupials from the miocene of patagonia; an assessment of form, function, and evolution...
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Abderitid Marsupials from Abderitid Marsupials from the Miocene of Patagonia; the Miocene of Patagonia; An Assessment of Form, An Assessment of Form, Function, and EvolutionFunction, and Evolution
E. R. Dumont, S. G. Strait, & R. Friscia. E. R. Dumont, S. G. Strait, & R. Friscia.
J. of Paleont. J. of Paleont. 74(6), 2000 pp. 1161-117274(6), 2000 pp. 1161-1172
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Systema Naturae 2000 http://sn2000.taxSystema Naturae 2000 http://sn2000.taxonomy.nl/onomy.nl/
Taxonomy of the Taxonomy of the CaenolestoidaeCaenolestoidae○Class Mammalia
○Subclass Theriiformes ○Legion Cladotheria
○Cohort Marsupialia ○Magnorder Ameridelphia ○Order Paucituberculata ○Superfamily Caenolestoidea
◊ Family Palaeothentidae
◊ Family Abderitidae ¤ Genus Pitheculites
¤ Genus Abderites
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Inca Shrew OpossumLestoros Inca
Chilean Shrew OpossumRhyncholestes raphanurus
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Primary Goal of the Primary Goal of the ExperimentExperiment○ Description of the abderitids from
Pinturas Formation and the Santa Cruz Formation - What does the P4/m1 blade complex and details of molar morphology tell us about the dietary and feeding adaptations of these animals?
- Were abderitids dietary generalist or specialists? - Given the many new fossils from a long geological
sequence, what can be said about the changes of abderitids overtime?
- In light of recent work on palaeothentid caenolestoids, how do the diversity and relative abundance of abderitids and palaeothentids at these locals compare?
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Collection SitesCollection Sites○ Santa Cruz Formation: Monte Observacion
and Monte Leon - Along coast of Santa Cruz providence of Argentina
- Coast alluvial plains deposits- Intermittent pyroclastic ash and gravel from volcanic uplift of the Andes Mountains- Development of some paleosols – lacked maturity
○ Pinturas Formation- Approximately 400 km inland from the Santa Cruz
Formation near Río Pinturas- More pyroclastic sediments- More paleosols - Two large erosional unconformities
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○ This table lists the extant species included in this study.
○ Mean body mass and mean area are provided for species used to establish predictive regression equation between mass and tooth size.
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Fossils species showed in this study. Sample size and mean were presented where body was reconstructed
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The progression of the wear on th left upper and lower shearing blades of A. meridionalis
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The progression of wear on left upper and lower shearing blades of Phalanger orientalis
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Abderitid Feeding EcologyAbderitid Feeding Ecology○ Abderitid plagiaulacoid shearing
complex is more similar to that of the living Phalanger than to either carpolestids or multituberculates
○ Phalanger species are frugivor-omniovore:◦ Primarily fruits and seeds◦ Also leaves, blossoms, and nectar
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Abderitid Diversity, Abderitid Diversity, Abundance, and EvolutionAbundance, and Evolution
○ Pinturas Formation: ◦ A. meridionalis exhibits little change in the tooth area
○ Santa Cruz Formation: ◦ An abrupt increase in lower molar size in Abderites at the base◦ A similar shift in body size just above the base of the formation in association with volance activity
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Summary and ConclusionsSummary and Conclusions
○ Caenolestoid marsupials from Santacrucian Land Mammal Age of southern Argentina contained species from 8-1000 g
○ Although modern caenolestoids are faunivores, the Miocene fauna included both frugivores and faunivores, as well as mixed feeders
○ The two main groups of Santacrucian caenolestoids, abderitids and palaeothenids, differ dramatically in species diversity and inferred dietary strategies
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Summary and Conclusions.. Summary and Conclusions..
○ All Miocene abderitids can be placed into four species: ◦ Abderites meridionalis◦ Abderites pristinus◦ Pithiculites minimus ◦ Pithiculites chenche
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Summary and Conclusions..Summary and Conclusions..○ Abderites
◦ larger of the two groups and primarily frugivorous◦ all possess a well developed, double-bladed P4/m1 shearing complex◦ Based on comparison to Phalanger orientalis with a similar shearing mechanism, allowed initiation of the breakdown of hard or tough food◦ This unique specialization permitted a varied diet allows them to be veiwed as dietary generalists
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Summary and Conclusion..Summary and Conclusion..○ Palaeothentids
◦ Consumed a mixture of plant and animal material◦ More specious: exhibited wider range in body mass and encompassed a broader range of dietary strategies◦ Lacked a highly specialized P4/m1 shearing complex◦ Constrained to food designed for their specific molar teeth allows classification for dietary specialists
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Summary and ConclusionSummary and Conclusion○ Abderitids generalized morphology,
low species diversity, and stability over time allows classification as a eurytopic lineage
○ Palaeothentids generally exhibited shorter geological ranges with greater species diversity◦ Appear to be strongly affected by local environmental fluctuations◦ These combined allow for classification of stenotopic lineage