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Abderitid Marsupials from the Miocene of Patagonia; An Assessment of Form, Function, and Evolution E. R. Dumont, S. G. Strait, & R. Friscia. J. of Paleont.

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Presentation on theme: "Abderitid Marsupials from the Miocene of Patagonia; An Assessment of Form, Function, and Evolution E. R. Dumont, S. G. Strait, & R. Friscia. J. of Paleont."— Presentation transcript:

1 Abderitid Marsupials from the Miocene of Patagonia; An Assessment of Form, Function, and Evolution E. R. Dumont, S. G. Strait, & R. Friscia. J. of Paleont. 74(6), 2000 pp

2 Systema Naturae Taxonomy of the Caenolestoidae ○ Class MammaliaMammalia ○ Subclass TheriiformesTheriiformes ○ Legion CladotheriaCladotheria ○ Cohort MarsupialiaMarsupialia ○ Magnorder AmeridelphiaAmeridelphia ○ Order PaucituberculataPaucituberculata ○ Superfamily CaenolestoideaCaenolestoidea ◊ Family PalaeothentidaePalaeothentidae ◊ Family Abderitidae ¤ Genus Pitheculites ¤ Genus Abderites

3 Inca Shrew Opossum Lestoros Inca Chilean Shrew Opossum Rhyncholestes raphanurus

4 Primary Goal of the Experiment ○ 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?

5 Collection 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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13 ○ 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.

14 Fossils species showed in this study. Sample size and mean were presented where body was reconstructed

15 The progression of the wear on th left upper and lower shearing blades of A. meridionalis

16 The progression of wear on left upper and lower shearing blades of Phalanger orientalis

17 Abderitid 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

18 Abderitid Diversity, Abundance, 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

19 Summary and Conclusions ○ Caenolestoid marsupials from Santacrucian Land Mammal Age of southern Argentina contained species from 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

20 Summary and Conclusions.. ○ All Miocene abderitids can be placed into four species: ◦ Abderites meridionalis ◦ Abderites pristinus ◦ Pithiculites minimus ◦ Pithiculites chenche

21 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

22 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

23 Summary 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


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