The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic nontherian lineage into the late Cenozoic of South America

The early Miocene mammal Necrolestes patagonensis from Patagonia, Argentina, was described in 1891 as the only known extinct placental "insectivore" from South America (SA). Since then, and despite the discovery of additional well-preserved material, the systematic status of Necrolestes has remained in flux, with earlier studies leaning toward placental affinities and more recent ones endorsing either therian or specifically metatherian relationships. We have further prepared the best-preserved specimens of Necrolestes and compared them with newly discovered nontribosphenic Mesozoic mammals from Argentina; based on this, we conclude that Necrolestes is related neither to marsupials nor placentals but is a late-surviving member of the recently recognized nontherian clade Meridiolestida, which is currently known only from SA. This conclusion is supported by a morphological phylogenetic analysis that includes a broad sampling of therian and nontherian taxa and that places Necrolestes within Meridiolestida. Thus, Necrolestes is a remnant of the highly endemic Mesozoic fauna of nontribosphenic mammals in SA and extends the known record of meridiolestidans by almost 45 million years. Together with other likely relictual mammals from earlier in the Cenozoic of SA and Antarctica, Necrolestes demonstrates the ecological diversity of mammals and the mosaic pattern of fauna replacement in SA during the Cenozoic. In contrast to northern continents, the Cenozoic faunal history of SA was characterized by a long period of interaction between endemic mammalian lineages of Mesozoic origin and metatherian and eutherian lineages that probably dispersed to SA during the latest Cretaceous or earliest Paleocene.Fil: Rougier, Guillermo W.. University of Louisville; Estados Unidos. Carnegie Museum Of Natural History; Estados UnidosFil: Wible, John R.. Carnegie Museum Of Natural History; Estados UnidosFil: Beck, Robin M. D.. University of New South Wales; AustraliaFil: Apesteguía, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentin

Simple guide to starting a research group

Conducting cutting-edge research and scholarship becomes more complicated with each passing year; forming a collaborative research group offers a way to navigate this increasing complexity. Yet many individuals whose work might benefit from the formation of a collaborative team may feel overwhelmed by the prospect of attempting to build and maintain a research group. We propose this simple guide for starting and maintaining such an enterprise

Simple Guide to Using Generative Artificial Intelligence Writing Tools in Research & Scholarship at UNH

While Artificial Intelligence (AI) technologies have existed for years, the recent arrival of widespread generative AI writing tools such as ChatGPT has provoked varied reactions in the scholarly community worldwide. Undoubtedly easy access to such tools may help to level the scholarly playing field for certain groups, particularly those with limited writing skills or proficiency with English as the primary language for written and oral communication of research and scholarship. There are, however, concerns about these tools, including, but not limited to, the accuracy, consistency, and bias of the information generated, appropriate acknowledgement of source material, and the tools’ lack of ability to reason or to understand meaning when generating output. This simple guide was developed to assist researchers and trainees to understand the fundamental issues with these technologies regarding research integrity

Cortisol, cognition and the ageing prefrontal cortex

The structural and functional decline of the ageing human brain varies by brain region, cognitive function and individual. The underlying biological mechanisms are poorly understood. One potentially important mechanism is exposure to glucocorticoids (GCs; cortisol in humans); GC production is increasingly varied with age in humans, and chronic exposure to high levels is hypothesised to result in cognitive decline via cerebral remodelling. However, studies of GC exposure in humans are scarce and methodological differences confound cross-study comparison. Furthermore, there has been little focus on the effects of GCs on the frontal lobes and key white matter tracts in the ageing brain. This thesis therefore examines relationships among cortisol levels, structural brain measures and cognitive performance in 90 healthy, elderly community-dwelling males from the Lothian Birth Cohort 1936. Salivary cortisol samples characterised diurnal (morning and evening) and reactive profiles (before and after a cognitive test battery). Structural variables comprised Diffusion Tensor Imaging measures of major brain tracts and a novel manual parcellation method for the frontal lobes. The latter was based on a systematic review of current manual methods in the context of putative function and cytoarchitecture. Manual frontal lobe brain parcellation conferred greater spatial and volumetric accuracy when compared to both single- and multi-atlas parcellation at the lobar level. Cognitive ability was assessed via tests of general cognitive ability, and neuropsychological tests thought to show differential sensitivity to the integrity of frontal lobe sub-regions. The majority of, but not all frontal lobe test scores shared considerable overlap with general cognitive ability, and cognitive scores correlated most consistently with the volumes of the anterior cingulate. This is discussed in light of the diverse connective profile of the cingulate and a need to integrate information over more diffuse cognitive networks according to proposed de-differentiation or compensation in ageing. Individuals with higher morning, evening or pre-test cortisol levels showed consistently negative relationships with specific regional volumes and tract integrity. Participants whose cortisol levels increased between the start and end of cognitive testing showed selectively larger regional volumes and lower tract diffusivity (correlation magnitudes <.44). The significant relationships between cortisol levels and cognition indicated that flatter diurnal slopes or higher pre-test levels related to poorer test performance. In contrast, higher levels in the morning generally correlated with better scores (correlation magnitudes <.25). Interpretation of all findings was moderated by sensitivity to type I error, given the large number of comparisons conducted. Though there were limited candidates for mediation analysis, cortisol-function relationships were partially mediated by tract integrity (but not sub-regional frontal volumes) for memory and post-error slowing. This thesis offers a novel perspective on the complex interplay among glucocorticoids, cognition and the structure of the ageing brain. The findings suggest some role for cortisol exposure in determining age-related decline in complex cognition, mediated via brain structure

Petrosal and cranial vascular system of the early Eocene palaeoryctid mammal Eoryctes melanus from northwestern Wyoming, USA

The petrosal and neighboring bones of the early Eocene palaeoryctid mammal Eoryctes melanus are described in tympanic and endocranial views based on CT scan data of the holotype. A second cranium of E. melanus has fragments of an osseous bulla, which have been interpreted as possibly formed by an independent entotympanic. The CT scans of the holotype reveal that the medial bullar wall is formed by an expanded rostral tympanic process of the petrosal, but the element(s) in the bullar floor remain unknown. The CT scans also allow for a comprehensive reconstruction of the cranial arterial and venous system. The arterial pattern differs from that in early eutherians by the absence of the arteria diploëtica magna and the bifurcation of the end branches of the stapedial artery dorsal to the tympanic roof. The venous pattern includes a large frontal diploic vein arising from the dorsal sagittal sinus on the midline and running through the frontal bone in a canal. Comparisons are made with other palaeoryctids, various Paleogene mammals (pantolestids, leptictids, apternodontids, apatemyids, and cimolestids) and the extant lipotyphlan Solenodon paradoxus. For the last taxon, the structure of the piriform fenestra and associated arteries is detailed. Cranial features support the monophyly of palaeoryctids and suggest possible lipotyphlan affinities