Ben Creisler
For Fossil Friday, a few recent mammal-related papers that might be of interest:
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Fossil footprints: the fascinating story behind the longest known prehistoric journey
We describe a long prehistoric human trackway (1.5 km) of Late Pleistocene age at White Sands National Park (New Mexico, USA).
The trackway indicates two journeys. The outbound tracks are crosscut by giant ground sloth and Columbian Mammoth tracks.
Morphological variability is explored using track outlines.
This variability suggests that minimum sample sizes for biometric inferences are larger than commonly assumed.
Abstract
Human tracks at White Sands National Park record more than one and a half kilometres of an out- and-return journey and form the longest Late Pleistocene-age double human trackway in the world. An adolescent or small adult female made two trips separated by at least several hours, carrying a young child in at least one direction. Despite giant ground sloth and Columbian Mammoth transecting them between the outbound and return journeys, the human tracks show no changes indicative of predator/prey awareness. In contrast, the giant ground sloth tracks show behaviour consistent with human predator awareness, while mammoth tracks show no such apparent concern. The human footprints are morphologically variable and exhibit left-right asymmetry, which might be due to child carrying. We explore this morphological variability using methods based on the analysis of objective track outlines, which add to the analytical toolkit available for use at other human footprint sites. The sheer number of tracks and their remarkable morphological variability have implications for the reliability of inferences made using much smaller samples as are more common at typical footprint sites. One conclusion is that the number of footprints required to make reliable biometric inferences is greater than often assumed.
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Free pdf:
Silvia PinedaâMunoz, Advait M. Jukar, Anikà B. TÃth, Danielle Fraser, Andrew Du, W. Andrew Barr, Kathryn L. Amatangelo, Meghan A. Balk, Anna K. Behrensmeyer, Jessica Blois, Matt Davis, Jussi T. Eronen, Nicholas J. Gotelli, Cindy Looy, Joshua H. Miller, Alexandria B. Shupinski, Laura C. Soul, Amelia VillaseÃor, Scott Wing & S. Kathleen Lyons (2020) Â
Body massârelated changes in mammal community assembly patterns during the late Quaternary of North America.
Ecography (advance online publication)
doi:
https://doi.org/10.1111/ecog.05027https://onlinelibrary.wiley.com/doi/10.1111/ecog.05027
The late Quaternary of North America was marked by prominent ecological changes, including the endâPleistocene megafaunal extinction, the spread of human settlements and the rise of agriculture. Here we examine the mechanistic reasons for temporal changes in mammal species association and body size during this time period. Building upon the coâoccurrence results from Lyons et al. (2016) -- wherein each species pair was classified as spatially aggregated, segregated or random -- we examined body mass differences (BMD) between each species pair for each association type and time period (Late Pleistocene: 40 000 14C-11 700 14C ybp, Holocene: 11 700 14Câ50 ybp and Modern: 50-0 yr). In the Late Pleistocene and Holocene, the BMD of both aggregated and segregated species pairs was significantly smaller than the BMD of random pairs. These results are consistent with environmental filtering and competition as important drivers of community structure in both time periods. Modern assemblages showed a breakdown between BMD and coâoccurrence patterns: the average BMD of aggregated, segregated and random species pairs did not differ from each other. Collectively, these results indicate that the late Quaternary mammalian extinctions not only eliminated many largeâbodied species but were followed by a reâorganization of communities that altered patterns of species coexistence and associated differences in body size.
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Extant marsupials are highly diverse, both morphologically and ecologically. As a key ecological factor, diet has been studied in marsupials at the species level. However, a general lack of phylogenetic integration has resulted in macroevolutionary patterns of diet remaining largely unexplored in the group.
We review dietary information for extant marsupials and present the results of an evolutionary analysis in an explicit phylogenetic framework.
We compiled dietary data from diverse sources, coding characters in four dietary schemes. We reconstructed ancestral states of predominant diet and dietary shifts during marsupial evolution, by using a published, dated phylogeny that includes 193 extant species representing 97% of genera.
The ancestral diet was predominant insectivory. Most frequent transitions occurred towards carnivory, since the late Eocene. By contrast, the shift towards browse herbivory occurred only once, in Australasia, in Diprotodontia, as early as the Palaeocene. The browse herbivorous ancestor gave rise to several other herbivore strategies, as well as to the predominant mycophagy that evolved in Potoroidae. In the Americas, only one extant marsupial clade evolved predominant herbivory (frugivory in Caluromyinae). We found omnivory to be a derived dietary strategy that occurred in both American and Australasian lineages. Temporal and geographic patterns of marsupial dietary diversification appear to be dependent on major palaeoclimatic events and on concurrent diversification of other (placental) clades.
The higher frequency of transitions from an insectivorous ancestor towards carnivory might be related to the minor anatomical, physiological and molecular changes required by a transition within an animalivory (proteinâbased) dietary gradient, in contrast with major changes required by shifts towards herbivory (carbohydrateâbased diet). The contrasting evolutionary patterns of diet between marsupials in the Americas and Australasia may be explained, at least partially, by the radically different faunas with which marsupials from each region interacted during their parallel evolutionary history.
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