scholarly journals Impact of K-Pg Mass Extinction Event on Crocodylomorpha Inferred from Phylogeny of Extinct and Extant Taxa

2021 ◽  
Author(s):  
Andrew F. Magee ◽  
Sebastian Höhna
Keyword(s):  
Mass Extinction ◽  
Likelihood Function ◽  
Simulated Data ◽  
Mass Extinctions ◽  
Holistic View ◽  
Occurrence Data ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
Biodiversity Changes ◽  
The Impact

AbstractCrocodilians and their allies have survived several mass extinction events. However, the impact of the K-Pg mass extinction event on crocodylomorphs is considered as minor or non-existent although other clades of archosaurs, e.g., non-avian dinosaurs and pterosaurs, went extinct completely. Previous approaches using fossil occurrence data alone have proven inconclusive. In this paper, we take a phylogenetic approach using extant and extinct species. The time-calibrated phylogeny of extant crocodilians provides insights into the pattern of recent biodiversity changes whereas fossil occurrence data provide insights about the more ancient past. The two data sources combined into a single phylogeny with extinct and extant taxa provide a holistic view of the historical biodiversity. To utilize this combined data and to infer the impact of the K-Pg mass extinction event, we derive the likelihood function for a time-varying (episodic) serially sampled birth-death model that additionally incorporates mass extinctions and bursts of births. We implemented the likelihood function in a Bayesian framework with recently developed smoothing priors to accommodate for both abrupt and gradual changes in speciation, extinction and fossilization rates. Contrary to previous research, we find strong evidence for the K-Pg extinction event in crocodiles and their allies. This signal is robust to uncertainty in the phylogeny and the prior on the mass extinctions. Through simulated data analyses, we show that there is high power to detect this mass extinction and little risk of false positives.

scholarly journals The impact of the Cretaceous–Paleogene (K–Pg) mass extinction event on the global sulfur cycle: Evidence from Seymour Island, Antarctica

2018 ◽  
Vol 230 ◽  
pp. 17-45 ◽  
Author(s):  
James D. Witts ◽  
Robert J. Newton ◽  
Benjamin J.W. Mills ◽  
Paul B. Wignall ◽  
Simon H. Bottrell ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Sulfur Cycle ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
The Impact ◽  
Seymour Island

scholarly journals Evidence for fungal proliferation following the Cretaceous/Paleogene mass-extinction event, based on chemostratigraphy in the Raton and Powder River basins, western North America

2020 ◽  
pp. 134-142
Author(s):  
Keith Berry
Keyword(s):  
Amino Acid ◽  
North America ◽  
Mass Extinction ◽  
River Basins ◽  
High Energy ◽  
Western North America ◽  
Ecosystem Recovery ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
The Impact

The presence of the amino acid α-aminoisobutyric acid (Aib) within Cretaceous/Paleogene (K/Pg) boundary clay in the Raton and Powder River basins in Colorado and Wyoming, respectively, has been described as compelling evidence that extraterrestrial Aib survived the high-energy Chicxulub impact. Based on contemporary experiments and simulations, however, it is highly unlikely that extraterrestrial Aib survived the impact, which had peak impact pressures and temperatures in excess of 600 GPa and 10,000 K, respectively. In other words, the amino acid signature of the carbonaceous chondritic asteroid that impacted Chicxulub was undoubtedly destroyed upon impact during formation of the vapor plume or so-called “fireball.” The only organisms known to produce Aib are the suite (more than 30 genera) of cosmopolitan saprotrophic filamentous fungi that include Trichoderma Pers., which has recently been hypothesized to have thrived during the K/Pg mass-extinction event. Therefore it is proposed that the Aib horizon in the K/Pg boundary clay in the Raton and Powder River basins correlates with the K/Pg boundary fungal spike, which thus far has only been observed in New Zealand (Southern Hemisphere). This proposition is based upon superimposing the Aib horizon on the well-known iridium and fern-spore spikes, as its stratigraphic position precisely matches that predicted by the fungal spike. If correct, this hypothesis alters the conventional perspective on the tempo and mode of terrestrial ecosystem recovery in western North America, as the heavily sampled K/Pg boundary section in the Raton Basin was instrumental in shaping the traditional narrative of the rapid recolonization of a denuded landscape by ferns via wind-blown spores in the immediate wake of regional deforestation caused by the K/Pg impact event. Perhaps more importantly, it could present an alternative to traditional palynological approaches for locating the fungal spike in other terrestrial K/Pg boundary sections and could provide additional support for the generalization that global mass-extinction events are frequently accompanied by fungal spikes.

scholarly journals Could a potential Anthropocene mass extinction define a new geological period?

2016 ◽  
Vol 3 (3) ◽  
pp. 208-217 ◽  
Author(s):  
Karen L Bacon ◽  
Graeme T Swindles
Keyword(s):  
Mass Extinction ◽  
Global Temperature ◽  
Current Debate ◽  
Mass Extinctions ◽  
Biodiversity Crisis ◽  
Extinction Event ◽  
Geological Boundaries ◽  
Near Term ◽  
Mass Extinction Event ◽  
Geological Period

A key aspect of the current debate about the Anthropocene focuses on defining a new geological epoch. Features of the Anthropocene include a biodiversity crisis with the potential to reach ‘mass extinction’ status alongside increasing global CO2 and temperature. Previous geological boundaries associated with mass extinctions, rises in atmospheric CO2 and rises in global temperature are more usually associated with transitions between geological periods. The current rapid increase in species extinctions suggest that a new mass extinction event is most likely imminent in the near-term future. Although CO2 levels are currently low in comparison with the rest of the Phanerozoic, they are rising rapidly along with global temperatures. This suggests that defining the Anthropocene as a new geological period, rather than a new epoch, may be more consistent with previous geological boundaries in the Phanerozoic.

scholarly journals Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Catherine G. Klein ◽  
Davide Pisani ◽  
Daniel J. Field ◽  
Rebecca Lakin ◽  
Matthew A. Wills ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Teleost Fishes ◽  
Mass Extinctions ◽  
Dispersal Patterns ◽  
Extinction Event ◽  
Living Species ◽  
Rapid Diversification ◽  
Molecular Dataset ◽  
Global Biodiversity ◽  
Mass Extinction Event

AbstractMass extinctions have repeatedly shaped global biodiversity. The Cretaceous-Paleogene (K-Pg) mass extinction caused the demise of numerous vertebrate groups, and its aftermath saw the rapid diversification of surviving mammals, birds, frogs, and teleost fishes. However, the effects of the K-Pg extinction on the evolution of snakes—a major clade of predators comprising over 3,700 living species—remains poorly understood. Here, we combine an extensive molecular dataset with phylogenetically and stratigraphically constrained fossil calibrations to infer an evolutionary timescale for Serpentes. We reveal a potential diversification among crown snakes associated with the K-Pg mass extinction, led by the successful colonisation of Asia by the major extant clade Afrophidia. Vertebral morphometrics suggest increasing morphological specialisation among marine snakes through the Paleogene. The dispersal patterns of snakes following the K-Pg underscore the importance of this mass extinction event in shaping Earth’s extant vertebrate faunas.

scholarly journals A Hiatus Obscures the Early Evolution of Modern Lineages of Bony Fishes

2021 ◽  
Vol 8 ◽  
Author(s):  
Carlo Romano
Keyword(s):  
Mass Extinction ◽  
Fossil Record ◽  
Middle Triassic ◽  
Early Evolution ◽  
Early Triassic ◽  
Triassic Boundary ◽  
Bony Fishes ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
The Impact

About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic. They appear during a time when global fish faunas consisted of mostly cosmopolitan taxa, and contemporary bony fishes belonged mainly to non-neopterygian (“paleopterygian”) lineages. In the Middle Triassic (Pelsonian substage and later), less than 10 myrs (million years) after the Permian-Triassic boundary mass extinction event (PTBME), neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. A major factor limiting our understanding of this “Triassic revolution” is an interval marked by a very poor fossil record, overlapping with the Spathian (late Olenekian, Early Triassic), Aegean (Early Anisian, Middle Triassic), and Bithynian (early Middle Anisian) substages. Here, I review the fossil record of Early and Middle Triassic marine bony fishes (Actinistia and Actinopterygii) at the substage-level in order to evaluate the impact of this hiatus–named herein the Spathian–Bithynian gap (SBG)–on our understanding of their diversification after the largest mass extinction event of the past. I propose three hypotheses: 1) the SSBE hypothesis, suggesting that most of the Middle Triassic diversity appeared in the aftermath of the Smithian-Spathian boundary extinction (SSBE; ∼2 myrs after the PTBME), 2) the Pelsonian explosion hypothesis, which states that most of the Middle Triassic ichthyodiversity is the result of a radiation event in the Pelsonian, and 3) the gradual replacement hypothesis, i.e. that the faunal turnover during the SBG was steady and bony fishes were not affected by extinction events subsequent to the PTBME. Based on current knowledge, hypothesis three is favored herein, but further studies are necessary to test alternative hypotheses. In light of the SBG, claims of a protracted diversification of bony fishes after the PTBME should be treated with caution.

scholarly journals The extinction and survival of sharks across the end-Cretaceous mass extinction

2021 ◽  
Author(s):  
Mohamad Bazzi ◽  
Nicolás E. Campione ◽  
Per E. Ahlberg ◽  
Henning Blom ◽  
Benjamin P. Kear
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Dental Morphology ◽  
Mass Extinctions ◽  
Morphological Response ◽  
Geometric Morphometric ◽  
Marine Predators ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
Early Paleogene

AbstractSharks (Selachimorpha) are iconic marine predators that have survived multiple mass extinctions over geologic time. Their fossil record is represented by an abundance of teeth, which traditionally formed the basis for reconstructing large-scale diversity changes among different selachimorph clades. By contrast, corresponding patterns in shark ecology, as measured through morphological disparity, have received comparatively limited analytical attention. Here, we use a geometric morphometric approach to comprehensively examine the dental morphology of multiple shark lineages traversing the catastrophic end-Cretaceous mass extinction — this event terminated the Mesozoic Era 66 million years ago. Our results show that selachimorphs maintained virtually static levels of dental disparity in most of their constituent clades during the Cretaceous/Paleogene transition. Nevertheless, selective extinctions did impact on apex predator lineages characterized by triangular blade-like teeth, and in particular, lamniforms including the dominant Cretaceous anacoracids. Other groups, such as, triakid carcharhiniforms, squalids, and hexanchids, were seemingly unaffected. Finally, while some lamniform lineages experienced morphological depletion, others underwent a post-extinction disparity increase, especially odontaspidids, which are typified by narrow-cusped teeth adapted for feeding on fishes. This disparity shift coincides with the early Paleogene radiation of teleosts, a possible prey source, as well as the geographic relocation of shark disparity ‘hotspots’, perhaps indicating a regionally disjunct pattern of extinction recovery. Ultimately, our study reveals a complex morphological response to the end-Cretaceous mass extinction event, the dynamics of which we are only just beginning to understand.

scholarly journals Dead clades walking are a pervasive macroevolutionary pattern

2021 ◽  
Vol 118 (15) ◽  
pp. e2019208118
Author(s):  
B. Davis Barnes ◽  
Judith A. Sclafani ◽  
Andrew Zaffos
Keyword(s):  
Mass Extinction ◽  
Bayesian Method ◽  
Marine Invertebrate ◽  
Mass Extinctions ◽  
Extinction Event ◽  
Genus Richness ◽  
Mass Extinction Event ◽  
Extinction Events ◽  
Mass Extinction Events

D. Jablonski [Proc. Natl. Acad. Sci. U.S.A. 99, 8139–8144 (2002)] coined the term “dead clades walking” (DCWs) to describe marine fossil orders that experience significant drops in genus richness during mass extinction events and never rediversify to previous levels. This phenomenon is generally interpreted as further evidence that the macroevolutionary consequences of mass extinctions can continue well past the formal boundary. It is unclear, however, exactly how long DCWs are expected to persist after extinction events and to what degree they impact broader trends in Phanerozoic biodiversity. Here we analyze the fossil occurrences of 134 skeletonized marine invertebrate orders in the Paleobiology Database (paleobiodb.org) using a Bayesian method to identify significant change points in genus richness. Our analysis identifies 70 orders that experience major diversity losses without recovery. Most of these taxa, however, do not fit the popular conception of DCWs as clades that narrowly survive a mass extinction event and linger for only a few stages before succumbing to extinction. The median postdrop duration of these DCW orders is long (>30 Myr), suggesting that previous studies may have underestimated the long-term taxonomic impact of mass extinction events. More importantly, many drops in diversity without recovery are not associated with mass extinction events and occur during background extinction stages. The prevalence of DCW orders throughout both mass and background extinction intervals and across phyla (>50% of all marine invertebrate orders) suggests that the DCW pattern is a major component of macroevolutionary turnover.

Chicxulub Structure: A Volcanic Sequence of Late Cretaceous Age

1994 ◽  
Vol 7 ◽  
pp. 425-436
Author(s):  
Charles B. Officer
Keyword(s):  
New Zealand ◽  
Residence Time ◽  
Late Cretaceous ◽  
Food Chain ◽  
Mass Extinction ◽  
Dust Cloud ◽  
Asteroid Impact ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
The Impact

The present Cretaceous/Tertiary extinction debate started with findings by Alvarez et al. (1980) of enhanced levels of iridium at K/T sections in Italy, Denmark and New Zealand. They postulated that the iridium was extraterrestrial in origin and related to a 10 km diameter asteroid impact which would have produced a crater some 200 km in diameter. They further suggested that a giant dust cloud would have been injected into the stratosphere from the impact with a residence time of several years and that the resulting darkness would have suppressed photosynthesis with a consequent elimination of succeeding members in the biological food chain — ergo, a mass extinction event.

scholarly journals Diversification Declines in Major Dinosaurian Clades are not Because of Edge Effects or Incomplete Fossil Sampling

2021 ◽  
Author(s):  
Manabu Sakamoto ◽  
Michael Benton ◽  
Chris Venditti
Keyword(s):  
Edge Effect ◽  
Mass Extinction ◽  
Taxonomic Diversity ◽  
Mass Extinctions ◽  
Model Framework ◽  
Extinction Event ◽  
Under Sampling ◽  
Phylogenetic Model ◽  
Mass Extinction Event

Abstract Signatures of catastrophic mass extinctions have long been reported to be obscured by the edge effect where taxonomic diversity appears to decline gradually. Similarly, models of diversification based on splitting of branches on a phylogenetic tree might also be affected by undersampling of divergences towards the edge. The implication is that long-term declines in diversification recovered from such models – e.g., in dinosaurs – may be artefacts of unsampled divergences. However, this effect has never been explicitly tested in a phylogenetic model framework – i.e., whether phylogenetic nodes (speciation events) close to the edge are under-sampled and if diversification declines are artefacts of such under-sampling. Here, we test whether dinosaur species in temporal proximity to the Cretaceous-Paleogene mass extinction event are associated with fewer nodes than expected, and whether this under-sampling can account for the diversification decline. We find on the contrary that edge taxa have higher numbers of nodes than expected and that accounting for this offset does not affect the diversification decline. We demonstrate that the observed diversification declines in the three major dinosaurian clades in the Late Cretaceous are not artefacts of the edge effect.

Rapid macrobenthic diversification and stabilization after the end-Cretaceous mass extinction event

Geology ◽  
2020 ◽  
Vol 48 (11) ◽  
pp. 1048-1052
Author(s):  
Francisco J. Rodríguez-Tovar ◽  
Christopher M. Lowery ◽  
Timothy J. Bralower ◽  
Sean P.S. Gulick ◽  
Heather L. Jones
Keyword(s):  
Mass Extinction ◽  
Rapid Recovery ◽  
Community Recovery ◽  
Scientific Drilling ◽  
Extinction Event ◽  
Chicxulub Impact Crater ◽  
Mass Extinction Event ◽  
International Ocean Discovery Program ◽  
Extinction Events ◽  
The Impact

Abstract Previous ichnological analysis at the Chicxulub impact crater, Yucatán Peninsula, México (International Ocean Discovery Program [IODP]/International Continental Scientific Drilling Program [ICDP] Site M0077), showed a surprisingly rapid initial tracemaker community recovery after the end-Cretaceous (Cretaceous-Paleogene [K-Pg]) mass extinction event. Here, we found that full recovery was also rapid, with the establishment of a well-developed tiered community within ∼700 k.y. Several stages of recovery were observed, with distinct phases of stabilization and diversification, ending in the development of a trace fossil assemblage mainly consisting of abundant Zoophycos, Chondrites, and Planolites, assigned to the Zoophycos ichnofacies. The increase in diversity is associated with higher abundance, larger forms, and a deeper and more complex tiering structure. Such rapid recovery suggests that favorable paleoenvironmental conditions were quickly reestablished within the impact basin, enabling colonization of the substrate. Comparison with the end-Permian extinction reveals similarities during recovery, yet postextinction recovery was significantly faster after the K-Pg event. The rapid recovery has significant implications for the evolution of macrobenthic biota after the K-Pg event. Our results have relevance in understanding how communities recovered after the K-Pg impact and how this event differed from other mass extinction events.

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