Ben Creisler
Some recently (mainly) non-dino papers:
Free pdf:
The mammalian neck adopts a variety of postures during daily life and generates numerous head trajectories. Despite its functional diversity, the neck is constrained to seven cervical vertebrae in (almost) all mammals. Given this low number, an unexpectedly high degree of modularity of the mammalian neck has more recently been uncovered. This work aims to review neck modularity in mammals from a developmental, morpho-functional, and paleontological perspective and how high functional diversity evolved in the mammalian neck after the occurrence of meristic limitations. The fixed number of cervical vertebrae and the developmental modularity of the mammalian neck are closely linked to anterior Hox genes _expression_ and strong developmental integration between the neck and other body regions. In addition, basic neck biomechanics promote morpho-functional modularity due to preferred motion axes in the cranio-cervical and cervico-thoracic junction. These developmental and biomechanical determinants result in the characteristic and highly conserved shape variation among the vertebrae that delimits morphological modules. The step-wise acquisition of these unique cervical traits can be traced in the fossil record. The increasing functional specialization of neck modules, however, did not evolve all at once but started much earlier in the upper than in the lower neck. Overall, the strongly conserved modularity in the mammalian neck represents an evolutionary trade-off between the meristic constraints and functional diversity. Although a morpho-functional partition of the neck is common among amniotes, the degree of modularity and the way neck disparity is realized is unique in mammals.
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Our knowledge about the origin of landbirds (Telluraves) is increasing rapidly but new questions are arising because of the contradictory findings from previous studies. All of the major lineages in the highly diverse clade of Neoaves have a Gondwanan origin, although studies often disagree about the origin of different sub-lineages. Nevertheless, understanding the biogeographical histories of these groups (e.g. Accipitriformes, Passeriformes) is important when studying the evolution of variation in life history and behavioural traits. Therefore, we would like to find answers to questions such as which biogeographic changes affected the radiation of birds? When did the most influential climatic events affect the diversification of birds? What behavioural adaptations occurred in response to those large-scale changes? The major orogenetic events in Asia and South America formed specific corridors that enabled the radiation of birds. The climatic changes and habitat differentiation they caused during the Oligocene-Miocene era made the divergence of birds possible through their adaptation to newly available niches. Consequently, variation in life history and behavioural traits emerged as adaptive outcomes of changes in foraging, nestling and migratory behaviours.
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(paywalled)
New member of the Kaiparowits Formation indicates distinct sedimentological change.
Regionally correlative with the Kirtland, Tuscher and Bearpaw formations.
Sedimentological change interpreted as a response to emerging basement uplifts.
Extends the Campanian record on the Kaiparowits Plateau to nearly the entire stage.
Represents a lush and diverse paleoenvironment during the latest Campanian.
Abstract
Lithostratigraphic investigation of the richly fossiliferous Kaiparowits Formation in southern Utah reveals the presence of a previously unidentified stratigraphic unit herein named the Upper Valley Member. The 255-m-thick Upper Valley Member is latest Campanian to earliest Maastrichtian in age and records a significant sedimentological change in the Kaiparowits Formation. This change is illustrated in the member by a significant increase in near syn-sedimentary aged zircons, coincident with the introduction of white, volcaniclastic sandstones, as well as a paucity of Jurassic grains, which dominate the provenance of the rest of the formation. The source of the late Campanian volcaniclastic material, including near syn-sedimentary zircons, is most likely from nearby volcanic centers within the Laramide porphyry copper province to the south of the Kaiparowits Plateau in the Mogollon region. Measured sections reported here stratigraphically expand the Kaiparowits Formation to a total of 1005 m and find that the upper boundary of the formation is largely gradational with the overlying Canaan Peak Formation. Lithological changes documented in this study are interpreted to signify a sedimentological response to proximal magmatism and emerging uplifts within the Cordilleran foreland basin during early Laramide orogenesis, which resulted in paleo-drainage rearrangement in southern Laramidia in the latest Campanian. The fossil-bearing Upper Valley Member can be correlated regionally to the Kirtland, Tuscher and Bearpaw formations and other latest Campanian -- and possibly early Maastrichtian -- units across western North America and represents the capping member one of the most continuous terrestrial records of the Campanian biosphere found anywhere in the world.
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Free pdf:
Tais W. Dahl & Susanne K.M. Arens (2020)
The impacts of land plant evolution on Earth's climate and oxygenation state -- An interdisciplinary review.
Chemical Geology 547: 119665
doi:
https://doi.org/10.1016/j.chemgeo.2020.119665https://www.sciencedirect.com/science/article/pii/S0009254120302047The Paleozoic emergence of terrestrial plants has been linked to a stepwise increase in Earth's O2 levels and a cooling of Earth's climate by drawdown of atmospheric CO2. Vegetation affects the Earth's O2 and CO2 levels in multiple ways, including preferential organic carbon preservation by decay-resistant biopolymers (e.g. lignin) and changing the continental weathering regime that governs oceanic nutrient supply and marine biological production. Over shorter time scales (â1 Myr), land plant evolution is hypothesized to have occasionally enhanced P weathering and fertilized the oceans, expanding marine anoxia and causing marine extinctions. Oceanic anoxia would eventually become limited by oceanic O2 uptake as oxygen accumulates in the atmosphere and surface oceans when excess organic carbon is buried in marine sediments. Here, we review hypotheses and evidence for how the evolving terrestrial ecosystems impacted atmospheric and oceanic O2 and CO2 from the Ordovician and into the Carboniferous (485â298.9 Ma). Five major ecological stages in the terrestrial realm occurred during the prolonged time interval when land was colonized by plants, animals and fungi, marked by the evolution of 1) non-vascular plants, 2) vascular plants with lignified tissue, 3) plants with shallow roots, 4) arborescent and perennial vegetation with deep and complex root systems, and 5) seed plants. The prediction that land vegetation profoundly impacted the Earth system is justified, although it is still debated how the individual transitions affected the Earth's O2 and CO2 levels. The geological record preserves multiple lines of indirect evidence for environmental transitions that can help us to reconstruct and quantify global controls on Earth's oxygenation and climate state.