Biography of the Earth

The last era in the Phanerozoic Eon, the Cenozoic Era, is detailed in this chapter. The rise and radiation of the mammals occurred during Cenozoic after the devastation wrought by the Chicxulub Asteroid impact at the end of the Mesozoic Era. Ecological resources and niches vacated by the dinosaurs because of the mass extinction were filled by the mammals with concurrent developments in plants. Changes in climate and the mid-Miocene warming happened mid-era, then drying out and opening of grasslands followed by a plunge into ice ages and the Pleistocene extinction event. The late Cenozoic witnessed the development of humankind as the great ice sheets from the Pleistocene started to melt and the climate warm. The planet started to look similar to how it appears to humans today, and the current age of the Earth is the Cenozoic Era, Quaternary Period, Holocene Epoch, Meghalayan Age.

Asymmetry of extreme Cenozoic climate–carbon cycle events

The history of Earth’s climate and carbon cycle is preserved in deep-sea foraminiferal carbon and oxygen isotope records. Here, we show that the sub-million-year fluctuations in both records have exhibited negatively skewed non-Gaussian tails throughout much of the Cenozoic era (66 Ma to present), suggesting an intrinsic asymmetry that favors “hyperthermal-like” extreme events of abrupt global warming and oxidation of organic carbon. We show that this asymmetry is quantitatively consistent with a general mechanism of self-amplification that can be modeled using stochastic multiplicative noise. A numerical climate–carbon cycle model in which the amplitude of random biogeochemical fluctuations increases at higher temperatures reproduces the data well and can further explain the apparent pacing of past extreme warming events by changes in orbital parameters. Our results also suggest that, as anthropogenic warming continues, Earth’s climate may become more susceptible to extreme warming events on time scales of tens of thousands of years.

First record of a tomistomine crocodylian from Australia

Based on the known fossil record, the majority of crocodylians from the Cenozoic Era of Australia are referred to the extinct clade Mekosuchinae. The only extant crocodylians in Australia are two species of Crocodylus. Hence, the viewpoint that Crocodylus and mekosuchines have been the only crocodylians inhabiting Australia during the Cenozoic has remained largely undisputed. Herein we describe Australia’s first tomistomine crocodylian, Gunggamarandu maunala gen. et sp. nov., thus challenging the notion of mekosuchine dominance during most of the Cenozoic. The holotype specimen of Gunggamarandu maunala derives from the Pliocene or Pleistocene of south-eastern Queensland, marking the southern-most global record for Tomistominae. Gunggamarandu maunala is known from a large, incomplete cranium that possesses a unique combination of features that distinguishes it from other crocodylians. Phylogenetic analyses place Gunggamarandu in a basal position within Tomistominae, specifically as a sister taxon to Dollosuchoides from the Eocene of Europe. These results hint at a potential ghost lineage between European and Australian tomistomines going back more than 50 million years. The cranial proportions of the Gunggamarandu maunala holotype specimen indicate it is the largest crocodyliform yet discovered from Australia.

Out of the extratropics: the evolution of the latitudinal diversity gradient of Cenozoic marine plankton

Many ecological and evolutionary hypotheses have been proposed to explain the latitudinal diversity gradient, i.e. the increase in species richness from the poles to the tropics. Among the evolutionary hypotheses, the ‘out of the tropics’ (OTT) hypothesis has received considerable attention. The OTT posits that the tropics are both a cradle and source of biodiversity for extratropical regions. To test the generality of the OTT hypothesis, we explored the spatial biodiversity dynamics of unicellular marine plankton over the Cenozoic era (the last 66 Myr). We find large-scale climatic changes during the Cenozoic shaped the diversification and dispersal of marine plankton. Origination was generally more likely in the extratropics and net dispersal was towards the tropics rather than in the opposite direction, especially during the warmer climates of the early Cenozoic. Although migration proportions varied among major plankton groups and climate phases, we provide evidence that the extratropics were a source of tropical microplankton biodiversity over the last 66 Myr.

Multiple infiltration and cross-species transmission of foamy viruses across Paleozoic to Cenozoic era

Foamy viruses (FVs) are complex retroviruses that can infect humans and other animals. In this study, by integrating transcriptomic and genomic data, we discovered 412 FVs from 6 lineages in amphibians, which significantly increased the known set of FVs in amphibians. Among these lineages, salamander FVs maintained a co-evolutionary pattern with their hosts that could be dated back to the Paleozoic era, while, on the contrary, frog FVs were much more likely acquired from cross-species (class level) transmission in the Cenozoic era. In addition, we found three distinct FV lineages had integrated into the genome of a salamander. Unexpectedly, we identified a lineage of endogenous FV in caecilian expressed all complete major genes, demonstrating the potential existence of exogenous form of FV outside of mammals. Our discovery of rare phenomena in amphibian FVs has significantly increased our understanding of the macroevolution of the complex retrovirus. Importance Foamy viruses (FVs) represent, more so than other viruses, the best model of co-evolution between a virus and a host. This study represents so far, the largest investigation of amphibian FVs and revealed 412 FVs of 6 distinct lineages from three major orders of amphibians. Besides co-evolutionary pattern, cross-species and repeated infection were also observed during evolution of amphibian FVs. Remarkably, expressed FVs including a potential exogenous form were discovered, suggesting active FVs could be underestimated in nature. These findings revealed the multiple origin and complex evolution of amphibian FVs started from the Paleozoic era.

Stratigraphic Lexicon: The Onshore Cenozoic Sedimentary Formations of The Republic of Panama

The stratigraphic knowledge of Panama was, until now, spread over hundreds of scientific/geologic publications written during the past 120 years. The construction of the Panama Canal during the early twentieth century helped galvanizing the engineering and geological disciplines to understand the tectonic, sedimentation and biodiversity of the Cenozoic Era in this part of the world. Later, few petroleum companies arrived on the scene and contributed to our knowledge of the sub-surface. The past thirty years saw a surge of studies by many institutions in areas away from the Canal, such as in Darien, Azuero Peninsula, Bocas del Toro, and the Burica Peninsula near the Costa Rica Border. Our most recent knowledge came from the widening of the Panama Canal between 2007 and 2016. It is from all these older and recent studies that the present Lexicon draws its content. It provides the historical background of all described geological units in Panama and summarizes the lithological and paleontological knowledge of each units in an easy-to-search format.

The molecular systematics and diversification of a taxonomically unstable group of Asian cicada tribes related to Cicadini Latreille, 1802 (Hemiptera : Cicadidae)

The cicadas (Hemiptera: Cicadidae) related to tribe Cicadini exhibit some of the most remarkable phenotypes in the family, with many genera possessing striking colour patterns and unusual morphological features. This largely Asian group of 13 tribes has proven challenging for cicada taxonomists, in part because of likely convergent evolution or losses of these phenotypes. We present the first focused molecular phylogeny of this clade, including ~60 described genera. The genetic dataset contains 839 ingroup-informative sites (out of 2575) from mitochondrial cytochromec oxidase subunitI, nuclear elongation factor-1α, and nuclear acetyltransferase. We use Bayesian and maximum likelihood trees to test recent changes in tribe- and subtribe-level classification, and we reconstruct ancestral character states for potentially convergent traits influencing tribe descriptions. We use fossil and molecular clock calibrations to estimate the temporal and geographic context of the radiation. The tribes Gaeanini, Leptopsaltriini, Platypleurini, Psithyristriini, and Tosenini appear polyphyletic and in need of revision, in part because of convergent evolution of opaque wings and multiple convergent gains or losses of abdominal tubercles. Kalabita Moulton, 1923 is transferred from Platypleurini to Leptopsaltriini. Vittagaeana gen. nov. is established for Vittagaeana paviei comb. nov. and Vittagaeana dives comb. nov., formerly in Tosena. Sinosenini syn. nov. is synonymised with Dundubiina. Ayuthiini trib. nov. is established with two new subtribes for Ayuthia Distant, 1919 and Distantalna Boulard, 2009, formerly in Tosenini. For the earliest split in the tree, one common ancestor appears to have been Indian + Asian in geographic distribution and the other Asian. We estimate that the radiation began in the middle Cenozoic Era, possibly as recently as the early Miocene. The recent and steady pattern of diversification suggests that refinement of tribe diagnoses will prove challenging. http://zoobank.org:urn:lsid:zoobank.org:pub:5A6C16F4-5269-453B-BA5C-B29C3394683A

Reconciling atmospheric CO2, weathering, and calcite compensation depth across the Cenozoic

The Cenozoic era (66 to 0 million years) is marked by long-term aberrations in carbon cycling and large climatic shifts, some of which challenge the current understanding of carbon cycle dynamics. Here, we investigate possible mechanisms responsible for the observed long-term trends by using a novel approach that features a full-fledged ocean carbonate chemistry model. Using a compilation of pCO2, pH, and calcite compensation depth (CCD) observational evidence and a suite of simulations, we reconcile long-term Cenozoic climate and CCD trends. We show that the CCD response was decoupled from changes in silicate and carbonate weathering rates, challenging the continental uplift hypothesis. The two dominant mechanisms for decoupling are shelf-basin carbonate burial fractionation combined with proliferation of pelagic calcifiers. The temperature effect on remineralization rates of marine organic matter also plays a critical role in controlling the carbon cycle dynamics, especially during the warmer periods of the Cenozoic.