Ben Creisler
Some recent itemsÂ+ non-dino papers:
===
Free pdf:
Free pdf:
Anatomical Record 303(4) Special Issue: The Hidden World of Dinosaurs
(papers have been posted earlier on the DML in advance form)Â
===========
Abstract only for now:
Neural spine hyper-elongation in tetrapods is a unique morphological adaptation that creates a dorsal sail. While this extreme morphology has appeared several times in the evolutionary history of tetrapods, it was first experimented with by the non-mammalian synapsid group known as âPelycosaursâ, famously represented by the Permian apex predator Dimetrodon. Here we provide new fossil data tracing back the evolution of this morphological innovation back to the initial Carboniferous radiation of the synapsid clade. We describe a new hyper-elongated neural spine belonging to the earliest ophiacodontid synapsid Echinerpeton intermedium, from the Pennsylvanian-aged deposits of Florence, Nova Scotia. The new fossil unveils the rapid convergence and repeated evolution of the âdorsal sailâ morphology in Synapsida. The development of this trait may have given early synapsids a unique advantage in their early radiation over the other early amniotes, the reptiles.
====
Andrew G. Flynn, Adam J. Davis, Thomas E. Williamson, Matthew Heizler, C. William Fenley IV, Caitlin E. Leslie, Ross Secord, Stephen L. Brusatte & Daniel J. Peppe (2020)
Early Paleocene Magnetostratigraphy and Revised Biostratigraphy of the Ojo Alamo Sandstone and Lower Nacimiento Formation, San Juan Basin, New Mexico, USA.
GSA Bulletin (advance online publication)
doi:
https://doi.org/10.1130/B35481.1abstract/doi/10.1130/B35481.1/583105/Early-Paleocene-Magnetostratigraphy-and-Revised
Preprint:
The lower Paleocene Ojo Alamo Sandstone and Nacimiento Formation from the San Juan Basin (SJB) in northwestern New Mexico preserve arguably the best early Paleocene mammalian record in North America and is the type location for the Puercan (Pu) and Torrejonian (To) North American land mammal ages (NALMA). However, the lack of precise depositional age constraints for the Ojo Alamo Sandstone and lower Nacimiento Formation has hindered our understanding of the timing and pacing of mammalian community change in the SJB following the Cretaceous-Paleogene mass extinction. Here we produced a high-resolution age model for the Ojo Alamo Sandstone and lower Nacimiento Formation combining magnetostratigraphy and 40Ar/39Ar geochronology spanning the first ~3.5 m.y. of the Paleocene. Mean sediment accumulation rates during C29n were relatively low (<50 m/m.y.) and equalized from basin center to basin margin indicating an accommodation minimum; sediment accumulation rates approximately double (>90 m/m.y.) during C28r and are highest in the basin center and lowest on basin margin, which indicates high accommodation and an increase in basin subsidence near the C29n/C28r boundary (ca. 64.96 Ma). Puercan fossil localities were restricted to C29n, Torrejonian 1 localities to C28n, and lower Torrejonian 2 localities to C27r. Our revised age model for the SJB suggests that the first appearance of To1 mammals may have been diachronous across North America, with the Torrejonian 1 mammals first appearing in the north (Montana and North Dakota) during C29n, then in middle latitudes (Utah) in C28r, and lastly in southern North America (New Mexico) in C28n.
===
Ruchira Somaweera, James Nifong, Adam Rosenblatt, Mathew L. Brien, Xander Combrink, Ruth M. Elsey, Gordon Grigg, William E. Magnusson, Frank J. Mazzotti, Ashley Pearcy, Steven G. Platt, Matthew H. Shirley, Marisa Tellez, Jan van der Ploeg, Grahame Webb, Rom Whitaker & Bruce L. Webber (2020)
The ecological importance of crocodylians: towards evidenceâbased justification for their conservation.
Biological Reviews (advance online publication)
doi:
https://doi.org/10.1111/brv.12594https://onlinelibrary.wiley.com/doi/10.1111/brv.12594
Largeâbodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosystems are poorly understood, constraining the design and implementation of optimal conservation strategies for freshwater ecosystems. Conservationists and environmentalists frequently promulgate ecological roles that crocodylians are assumed to fulfil, but often with limited evidence supporting those claims.
Here, we review the available information on the ecological importance of crocodylians, a widely distributed group of predominantly freshwaterâdwelling, largeâbodied predators. We synthesise information regarding the role of crocodylians under five criteria within the context of modern ecological concepts: as indicators of ecological health, as ecosystem engineers, apex predators, keystone species, and as contributors to nutrient and energy translocation across ecosystems. Some crocodylians play a role as indicators of ecosystem health, but this is largely untested across the order Crocodylia. By contrast, the role of crocodylian activities in ecosystem engineering is largely anecdotal, and information supporting their assumed role as apex predators is currently limited to only a few species. Whether crocodylians contribute significantly to nutrient and energy translocation through crossâecosystem movements is unknown.
We conclude that most claims regarding the importance of crocodylians as apex predators, keystone species, ecosystem engineers, and as contributors to nutrient and energy translocation across ecosystems are mostly unsubstantiated speculation, drawn from anecdotal observations made during research carried out primarily for other purposes. There is a paucity of biological research targeted directly at: understanding population dynamics; trophic interactions within their ecological communities; and quantifying the shortâ and longâterm ecological impacts of crocodylian population declines, extirpations, and recoveries. Conservation practices ideally need evidenceâbased planning, decision making and justification. Addressing the knowledge gaps identified here will be important for achieving effective conservation of crocodylians.
==========
Text preview, no abstract: