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[dinosaur] Cenozoic climate shifts: Mammalian ecomorphological specialization + avian latitudinal distributions

Ben Creisler

New non-dino papers that may be of interest:

Borja Figueirido, Paul Palmqvist, Juan A. PÃrez-Claros, and Christine M. Janis (2019)
Sixty-six million years along the road of mammalian ecomorphological specialization.
Proceedings of the National Academy of Sciences (advance online publication)
doi: Âhttps://doi.org/10.1073/pnas.1821825116


The six "evolutionary faunas" of large mammal taxonomic diversity described for the North American Cenozoic have a nonrandom ecomorphological spectrum and show a long-term trend toward greater ecological specialization over the past 66 My. We show here that each successive fauna was characterized by a change toward more specialized ecotypes; these changes were correlated with vegetation shifts caused by major climatic changes, which may have promoted the appearance of new ecological opportunities and morphological innovations.


The fossil record of the large terrestrial mammals of the North American Cenozoic has previously been quantitatively summarized in six sequential episodes of faunal associations--"evolutionary faunas"--that correspond well with previously proposed qualitative "Chronofaunas." Here, we investigate the ecological spectrum of these faunas by classifying their major taxonomic components into discrete ecomorphological categories of diet, locomotion, and body size. To specifically address the potential influence of long-term climatic shifts on the ecomorphological composition of these faunas, we analyze via contingency tables and detrended correspondence analyses the frequency distribution of ecomorph types within faunas. We show that each evolutionary fauna has a unique, nonrandom association of ecomorphs, and we identify a long-term trend toward greater ecomorphological specialization over successive faunas during the past 66 My. Major vegetation shifts induced by climatic changes appear to underlie the ecomorphological dynamics of these six temporal associations that summarize Cenozoic North American mammalian evolutionary history.


Erin E. Saupe, Alexander Farnsworth, Daniel J. Lunt, Navjit Sagoo, Karen V. Pham, and Daniel J. Field (2019)
Climatic shifts drove major contractions in avian latitudinal distributions throughout the Cenozoic.
Proceedings of the National Academy of Sciences (advance online publication)
doi: Âhttps://doi.org/10.1073/pnas.1903866116


The fossil record reveals evidence of dramatic distributional shifts through time for many groups of organisms. One striking example is the early fossil record of modern birds, which shows that many bird groups currently restricted to the tropics were formerly found at high latitudes in North America and Europe. Tracking potentially suitable habitat for these clades over the last 56 million years reveals that cooling trends throughout this period may have largely dictated the geographic distributions of these "tropical" groups, complicating our understanding of where on Earth many of these lineages originated.


Many higher level avian clades are restricted to Earthâs lower latitudes, leading to historical biogeographic reconstructions favoring a Gondwanan origin of crown birds and numerous deep subclades. However, several such "tropical-restricted" clades (TRCs) are represented by stem-lineage fossils well outside the ranges of their closest living relatives, often on northern continents. To assess the drivers of these geographic disjunctions, we combined ecological niche modeling, paleoclimate models, and the early Cenozoic fossil record to examine the influence of climatic change on avian geographic distributions over the last â56 million years. By modeling the distribution of suitable habitable area through time, we illustrate that most Paleogene fossil-bearing localities would have been suitable for occupancy by extant TRC representatives when their stem-lineage fossils were deposited. Potentially suitable habitat for these TRCs is inferred to have become progressively restricted toward the tropics throughout the Cenozoic, culminating in relatively narrow circumtropical distributions in the present day. Our results are consistent with coarse-scale niche conservatism at the clade level and support a scenario whereby climate change over geological timescales has largely dictated the geographic distributions of many major avian clades. The distinctive modern bias toward high avian diversity at tropical latitudes for most hierarchical taxonomic levels may therefore represent a relatively recent phenomenon, overprinting a complex biogeographic history of dramatic geographic range shifts driven by Earthâs changing climate, variable persistence, and intercontinental dispersal. Earthâs current climatic trajectory portends a return to a megathermal state, which may dramatically influence the geographic distributions of many range-restricted extant clades.





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