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[dinosaur] Mass extinctions on Pangaea + megafauna extinctions + Late Triassic climate in Chinle sandstone

Ben Creisler

Some recent papers:

Free pdf:

David J. Button, Graeme T. Lloyd, Martín D. Ezcurra & Richard J. Butler (2017)
Mass extinctions drove increased global faunal cosmopolitanism on the supercontinent Pangaea.
Nature Communications 8, Article number: 733 (2017)

Mass extinctions have profoundly impacted the evolution of life through not only reducing taxonomic diversity but also reshaping ecosystems and biogeographic patterns. In particular, they are considered to have driven increased biogeographic cosmopolitanism, but quantitative tests of this hypothesis are rare and have not explicitly incorporated information on evolutionary relationships. Here we quantify faunal cosmopolitanism using a phylogenetic network approach for 891 terrestrial vertebrate species spanning the late Permian through Early Jurassic. This key interval witnessed the Permian–Triassic and Triassic–Jurassic mass extinctions, the onset of fragmentation of the supercontinent Pangaea, and the origins of dinosaurs and many modern vertebrate groups. Our results recover significant increases in global faunal cosmopolitanism following both mass extinctions, driven mainly by new, widespread taxa, leading to homogenous ‘disaster faunas’. Cosmopolitanism subsequently declines in post-recovery communities. These shared patterns in both biotic crises suggest that mass extinctions have predictable influences on animal distribution and may shed light on biodiversity loss in extant ecosystems.






Mauro Galetti, Marcos Moleón, Pedro Jordano, Mathias M. Pires, Paulo R. Guimarães Jr., Thomas Pape, Elizabeth Nichols, Dennis Hansen, Jens M. Olesen, Michael Munk, Jacqueline S. de Mattos, Andreas H. Schweiger, Norman Owen-Smith, Christopher N. Johnson, Robert J. Marquis and Jens-Christian Svenning (2017)

Ecological and evolutionary legacy of megafauna extinctions.

Biological Reviews (advance online publication)

DOI: 10.1111/brv.12374




For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna


Cong Jin, Steve Dworkin, Stacy Atchley and Lee Nordt (2017)

Eogenetic diagenesis of Chinle sandstones, Petrified Forest National Park (Arizona, USA): A record of Late Triassic climate change.

Sedimentology (advance online publication)

DOI: 10.1111/sed.12421


Fluvially derived tuffaceous Chinle sandstones from Petrified Forest National Park provide a well-preserved Late Triassic archive of climate information. Petrographic analysis of 38 Chinle sandstones provides new insight into the depositional history and evolution of palaeoclimate during Chinle deposition. This study focuses on the relationship between climate and meteoric diagenesis as a guide for constraining climate change in western equatorial Pangea during the Late Triassic. Petrographic analysis of Chinle sandstones reveals their wide range of textural attributes, as well as pedogenic and shallow burial diagenetic features that occurred during the Late Triassic. These diverse petrological characteristics are indicative of the evolving Late Triassic climate, when placed into a well-constrained stratigraphic and geochronological framework. The stratigraphic succession is characterized by variations in the abundance of framework grains, detrital matrix, weathering intensity of feldspar and volcanic rock fragments, and the mineralogy of clay cements. Climate records from Chinle palaeosol geochemistry indicate a progression from wet to dry conditions. This trend is also reflected in the meteoric diagenetic features of Chinle sandstones. During deposition of the lower Chinle, elevated rainfall promoted the weathering of labile volcanic detritus to kaolinite whereas feldspars (especially plagioclase) were partially or completely dissolved. In the upper Chinle, a trend towards dryer conditions favoured the formation of smectite and less feldspar dissolution resulting in a higher abundance of well-preserved plagioclase grains. Shallow burial meteoric weathering reactions in Chinle sandstones reflect the evolving climate during the Late Triassic.



Free pdf:

Uri Roll, Anat Feldman, Maria Novosolov, Allen Allison, Aaron M. Bauer, Rodolphe Bernard, Monika Böhm, Fernando Castro-Herrera, Laurent Chirio, Ben Collen, Guarino R. Colli, Lital Dabool, Indraneil Das, Tiffany M. Doan, Lee L. Grismer, Marinus Hoogmoed, Yuval Itescu, Fred Kraus, Matthew LeBreton, Amir Lewin, Marcio Martins, Erez Maza, Danny Meirte, Zoltán T. Nagy, Cristiano de C. Nogueira, Olivier S. G. Pauwels, Daniel Pincheira-Donoso, Gary D. Powney, Roberto Sindaco, Oliver J. S. Tallowin, Omar Torres-Carvajal, Jean-François Trape, Enav Vidan, Peter Uetz, Philipp Wagner, Yuezhao Wang, C. David L. Orme, Richard Grenyer & Shai Meiri (2017)
The global distribution of tetrapods reveals a need for targeted reptile conservation.
Nature Ecology & Evolution (2017)

The distributions of amphibians, birds and mammals have underpinned global and local conservation priorities, and have been fundamental to our understanding of the determinants of global biodiversity. In contrast, the global distributions of reptiles, representing a third of terrestrial vertebrate diversity, have been unavailable. This prevented the incorporation of reptiles into conservation planning and biased our understanding of the underlying processes governing global vertebrate biodiversity. Here, we present and analyse the global distribution of 10,064 reptile species (99% of extant terrestrial species). We show that richness patterns of the other three tetrapod classes are good spatial surrogates for species richness of all reptiles combined and of snakes, but characterize diversity patterns of lizards and turtles poorly. Hotspots of total and endemic lizard richness overlap very little with those of other taxa. Moreover, existing protected areas, sites of biodiversity significance and global conservation schemes represent birds and mammals better than reptiles. We show that additional conservation actions are needed to effectively protect reptiles, particularly lizards and turtles. Adding reptile knowledge to a global complementarity conservation priority scheme identifies many locations that consequently become important. Notably, investing resources in some of the world’s arid, grassland and savannah habitats might be necessary to represent all terrestrial vertebrates efficiently.


Ronald Allan L. Cruz (2017)

Here Be Dragons: Using Dragons as Models for Phylogenetic Analysis

The American Biology Teacher 79(7):544-551. 2017 



Dragons are a staple of fantasy literature, and various aspects of the creatures (most notably their anatomy) have been explored scientifically across different forms of media. Their distinct anatomical characteristics and the variations therein among the recognized “species” of dragons make the taxa appropriate models for basic phylogenetic analysis in an undergraduate general biology or systematics class. The wyvern, an obviously more primitive, distant cousin of the “true” dragons, is also an appropriate outgroup for these estimations of shared evolutionary history. Separating metallic from chromatic dragons, the generated tree shows relationships among the species that are consistent with their separation in the Dungeons & Dragons games according to alignment, scale color, and religion, three characters that are not used in the analysis. Manual construction of a character matrix and cladogram of dragons followed by repetition of this process via conventional computer software allows the students to track their progress not only in terms of understanding such concepts as choice of character states and parsimony but also in terms of the applicability of said software.


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