skip to main content


Search for: All records

Creators/Authors contains: "Weaver, Lucas"

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Mammals rose to prominence in terrestrial ecosystems after the Cretaceous–Paleogene mass extinction, but the mammalian lineages characteristic of Paleogene faunas began their evolutionary and ecological diversification in the Late Cretaceous, stimulated by the rise of angiosperms (flowering plants) according to the preeminent hy- pothesis. The Cretaceous rise of mammals is part of a larger expansion in biodiversity on land that has been termed the Cretaceous (or Angiosperm) Terrestrial Revolution, but the mechanisms underlying its initiation remain opaque. Here, we review data from the fossil and rock records of western North America—due to its relatively continuous fossil record and complete chronology of mountain-building events—to explore the role that tectonism might have played in catalyzing the rise of modern-aspect terrestrial biodiversity, especially that of mammals and angiosperms. We highlight that accelerated increases in mammal and angiosperm species richness in the Late Cretaceous, ca. 100–75 Ma, track the acceleration of tectonic processes that formed the North American Cordillera and occurred during the ‘middle-Cretaceous greenhouse’ climate. This rapid increase in both mammal and angiosperm diversity also occurred during the zenith of Western Interior Seaway trans- gression, a period when the availability of lowland habitats was at its minimum, and oscillatory transgression- regression cycles would have frequently forced upland range shifts among lowland populations. These changes to both landscapes and climates have all been linked to an abrupt, global tectonic-plate ‘reorganization’ that occurred ca. 100 Ma. That mammals and angiosperms both increased in species richness during this interval does not appear to be a taphonomic artifact—some of the largest spikes in diversity occur when the available mammal-bearing fossil localities are sparse. Noting that mountainous regions are engines for generating biodi- versity, especially in warm climates, we propose that the Cretaceous/Angiosperm Terrestrial Revolution was ultimately catalyzed by accelerated tectonism and enhanced via cascading changes to landscapes and climate. In the fossil record of individual basins across western North America, we predict that (1) increases in mammalian diversity through the Late Cretaceous should be positively correlated with rates of tectonic uplift, which we infer to be a proxy for topographic relief, and are attended by increased climate heterogeneity, (2) the diversity of mountain-proximal mammalian assemblages should exceed that of coeval mountain-distal assemblages, espe- cially in the latest Cretaceous, and (3) endemism should increase from the latest Cretaceous to early Paleogene as Laramide mountain belts fragmented the Western Interior. Empirical tests of these predictions will require increased fossil collecting in under-sampled regions and time intervals, description and systematic study of existing collections, and basin-scale integration of geological and paleontological data. Testing these predictions will further our understanding of the coevolutionary processes linking tectonics, climate, and life throughout Earth history. 
    more » « less
    Free, publicly-accessible full text available December 8, 2024
  2. Muñoz, Martha (Ed.)
    Abstract Selective pressures favor morphologies that are adapted to distinct ecologies, resulting in trait partitioning among ecomorphotypes. However, the effects of these selective pressures vary across taxa, especially because morphology is also influenced by factors such as phylogeny, body size, and functional trade-offs. In this study, we examine how these factors impact functional diversification in mammals. It has been proposed that trait partitioning among mammalian ecomorphotypes is less pronounced at small body sizes due to biomechanical, energetic, and environmental factors that favor a “generalist” body plan, whereas larger taxa exhibit more substantial functional adaptations. We title this the Divergence Hypothesis (DH) because it predicts greater morphological divergence among ecomorphotypes at larger body sizes. We test DH by using phylogenetic comparative methods to examine the postcranial skeletons of 129 species of taxonomically diverse, small-to-medium-sized (<15 kg) mammals, which we categorize as either “tree-dwellers” or “ground-dwellers.” In some analyses, the morphologies of ground-dwellers and tree-dwellers suggest greater between-group differentiation at larger sizes, providing some evidence for DH. However, this trend is neither particularly strong nor supported by all analyses. Instead, a more pronounced pattern emerges that is distinct from the predictions of DH: within-group phenotypic disparity increases with body size in both ground-dwellers and tree-dwellers, driven by morphological outliers among “medium”-sized mammals. Thus, evolutionary increases in body size are more closely linked to increases in within-locomotor-group disparity than to increases in between-group disparity. We discuss biomechanical and ecological factors that may drive these evolutionary patterns, and we emphasize the significant evolutionary influences of ecology and body size on phenotypic diversity. 
    more » « less
  3. Due to the increasing complexity of hardware designs, third-party hardware Intellectual Property (IP) cores are often incorporated to alleviate the burden on hardware designers. However, the prevalent use of third-party IPs has raised security concerns such as hardware Trojans. These Trojans inserted in the soft IPs are very difficult to detect through functional testing and no single detection methodology has been able to completely address this issue. Based on a Register- Transfer Level (RTL) soft IP analysis method named Structural Checking, this paper presents a hardware Trojan detection methodology and tool by detailing the implementation of a Golden Reference Library for matching an unknown IP to a functionally similar Golden Reference. The matching result is quantified in percentages so that two different IPs with similar functions have a higher percentage match. A match of the unknown IP to a whitelist IP advances it to be identified with a known functionality, while a match to a blacklist IP causes it to be detected as Trojan-infested. 
    more » « less