Cenozoic Indo-Pacific warm pool controlled by both atmospheric CO2 and paleogeography

The Indo-Pacific warm pool (IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation of sea surface temperature (SST) records (mainly since the middle Miocene) and multimodel paleoclimate simulations, our results indicated that the extent, intensity and warmest temperature position of the IPWP changed markedly during the Cenozoic. Specifically, its extent decreased, its intensity weakened, and its warmest temperature position shifted from the Indian to western Pacific Ocean over time. The atmospheric CO2 dominated its extent and intensity, while paleogeography, by restricting the distribution of the Indian Ocean and the width of the tropical seaways, controlled the shift in its warmest temperature position. In particular, the eastward shift to the western Pacific Ocean from the middle to late Miocene inferred from compiled SST records likely resulted from the constriction of tropical seaways. Furthermore, by changing the atmospheric thermal structure and atmospheric circulation, the reduced extent and intensity of the IPWP decreased the annual precipitation in the western Indian Ocean, eastern Asia and Australia, while the shift in the warmest temperature position from the Indian to western Pacific Ocean promoted aridification in Australia. Qualitative model-data agreements are obtained for both the IPWP SST and regional climate. From the perspective of past warm climates with high concentrations of atmospheric CO2, the expansion and strengthening of the IPWP will occur in a warmer future and favor excessive precipitation in eastern Asia and Australia.

Intra-island patterns of cryptic diversity within an oceanic island: Insights from the differentiation of Schizidium Verhoeff, 1901 (Oniscidea, Armadillidiidae) within Cyprus, with descriptions of two new species

Cyprus is a Mediterranean island of volcanic origin isolated for at least 5.3 Myr from surrounding continental areas. The present study focuses on the diversification of the isopod genus Schizidium within the island, including also specimens from surrounding continental areas. The genus Schizidium sensu lato is probably non monophyletic, comprising 26 species distributed from Greece to Iran. Up to date the only representative of the genus reported from Cyprus was Schizidium fissum. Aiming to investigate the patterns of genetic diversity within the focal island, to evaluate the morphology-based taxonomy of the species in the genus, and at the same time to explore phylogenetic relationships with mainland populations, we applied genome-wide ddRADseq as well as Sanger sequencing targeting three mitochondrial (16S, COI and 12S) and the nuclear NaK loci. Results of phylogenetic analyses support the existence of two distinct epigean Schizidium clades with well-defined geographic boundaries that conform to the known paleogeography of Cyprus, plus one endogean clade with restricted distribution within the island. Genetic data and morphology corroborate the assignment of this latter endogean clade to a new species, Schizidium myrrae n. sp. The two epigean clades are also considered as distinct species, one corresponding to the known S. fissum at the eastern part of the island (Pentadaktylos massif) and the other to the newly described S. christosi n. sp. distributed along the western part of the island (Troodos massif). Even though detailed examination of many specimens could not retrieve any morphological differences among representatives of these two clades, clado-chronological analysis indicates a long isolation between them, estimated at ∼ 9 Mya, as well as the sharing of a common ancestor with S. tiberianum from Israel at ∼ 15 Mya. Hence, we can consider these epigean Schizidium species as one more case of cryptic diversity on Cyprus, exhibiting similar patterns with the recently described case in the genus Armadillo.

Reconstructing Squamate Biogeography in Afro-Arabia Reveals the Influence of a Complex and Dynamic Geologic Past

The geographic distribution of biodiversity is central to understanding evolutionary biology. Paleogeographic and paleoclimatic histories often help to explain how biogeographic patterns unfold through time. However, such patterns are also influenced by a variety of other factors, such as lineage diversification, that may affect the probability of certain types of biogeographic events. The complex and well-known geologic and climatic history of Afro-Arabia, together with the extensive research on reptile systematics in the region, makes Afro-Arabian squamate communities an ideal system to investigate biogeographic patterns and their drivers. Here we reconstruct the phylogenetic relationships and the ancestral geographic distributions of several Afro-Arabian reptile clades (totaling 430 species) to estimate the number of dispersal, vicariance and range contraction events. We then compare the observed biogeographic history to a distribution of simulated biogeographic events based on the empirical phylogeny and the best-fit model. This allows us to identify periods in the past where the observed biogeographic history was likely shaped by forces beyond the ones included in the model. We find an increase in vicariance following the Oligocene, most likely caused by the fragmentation of the Afro-Arabian plate. In contrast, we did not find differences between observed and expected dispersal and range contraction levels. This is consistent with diversification enhanced by environmental processes and with the establishment of a dispersal corridor connecting Africa, Arabia and Eurasia since the middle Miocene. Finally, here we show that our novel approach is useful to pinpoint events in the evolutionary history of lineages that might reflect external forces not predicted by the underlying biogeographic model.

Preservation of latest Cretaceous (Maastrichtian)-Paleocene frogs (Eorubeta nevadensis) of the Sheep Pass Formation of east-central Nevada and implications for paleogeography of the Nevadaplano

Here we report on exceptional preservation of remains of the frog Eorubeta nevadensis in deposits of the Sheep Pass Formation, ranging from Late Cretaceous to Eocene, in the south Egan Range, Nevada. This formation represents a lacustrine basin within the Sevier retroarc hinterland. The formation is subdivided into six members (A-F); of interest here are members B and C. The base of member B is ?uppermost Cretaceous-Paleocene, while member C is Paleocene. Member B frogs are preserved in three taphonomic modes. Mode 1 frogs are nearly complete and accumulated under attritional processes, with frogs settling on microbial mats, as evidenced by crenulated fabric of entombing limestone. Mode 2 involves accumulation of frogs as a result of attritional processes. These frogs are mostly complete with some showing evidence of invertebrate scavenging. Possible scavengers are gastropods, ostracods, and decapods. Mode 3 is represented by isolated, reworked remains of frogs as a result of storm activity, supported by the association of elements with disarticulated bivalves and mud rip-up clasts. Member C preserves frogs in two taphonomic modes. Mode 4 are nearly complete frogs that accumulated during discrete mass mortality events. Numerous individuals are preserved along bedding planes in identical preservational states. Mode 5 is beds of frog bone hash, which represent increased energy to the depositional system (likely tempestites) and reworking of previously buried frog remains. Taphonomy of the frogs, along with the associated fauna and flora, are consistent with preservation in a cool, temperate lake basin, supporting previous interpretations that the Nevadaplano was an elevated plateau during the late Cretaceous through the Eocene. This is a period of time coincident with a climatic thermal optimum, thus the most parsimonious explanation for a temperate lake at the latitude of east-central Nevada is to invoke high elevation, which is consistent with independent structural and clumped stable isotope studies.

Least-cost pathway models indicate northern human dispersal from Sunda to Sahul

Archaeological records from Australia provide the earliest, indirect evidence for maritime crossings by early modern humans, as the islands to the north-west of the continent (Wallacea) have never been connected to the mainland. Suggested in 1977 by Joseph B. Birdsell, the two main routes from Sunda (mainland Southeast Asia) to Sahul (Australia-New Guinea), still in debate today, are a northern route through Sulawesi with a landing in New Guinea, or a southern route through Bali, Timor and thence landing in northern Australia. Here we construct least-cost pathway models of human dispersal from Sunda to Sahul at 65 ka and 70 ka by extending previous out-of-Africa least-cost models through the digitization of these routes. We recover overwhelming support for a northern route into Sahul, with a landing location on present-day Misool Island. Minimal support is also recovered for the southern route at 70 ka, with a possible crossing to Sahul from eastern Timor. Review of archaeological records on the Wallacean islands crossed by our northern route indicate a dearth of archaeological research in this region. Meanwhile, the comparatively better studied southern islands still lack any archaeological dates comparable to those known for initial occupation in Sunda and Sahul. Based on our model results we suggest Misool Island as the initial landing site for early modern humans on Sahul and recommend a future focus on archaeological fieldwork in the northern Wallacean islands.

Geological data indicate that the interpretation for the age-calibrated phylogeny for the Kurixalus-genus frogs of South, South-east and East Asia (Lv et al., 2018) needs to be rethought

Recently, Lv et al. (2018) published an age-calibrated phylogenetic tree for the Kurixalus frogs, members of which occur across parts of South, South-east and East Asia. A clade on Taiwan, represented by Kurixalus idiootocus and the Kurixalus eiffingeri species complex, is deemed to have been resident since the middle Cenozoic; its closest congeners are in southern Indochina (not in the adjacent parts of south-east China), and the split between the two is dated at 32.8 Ma. Furthermore, a sub-population of Kurixalus eiffingeri is believed to have colonized islands in the western Ryukyus c. 13.5 Ma. There is, however, a problem with this scenario: the landmass regarded as modern-day Taiwan has existed only for 4-5 million years (it results from a young and ongoing tectonic-plate collision). Assuming the Kurixalus phylogeny and the dating of its branchings are correct, then a palaeobiogeographical scenario involving an older, alternative land surface with later transfer to Taiwan, possibly involving over-water dispersal, would reconcile the biology, but testing this may be difficult/impossible. If the ages of the nodes in the proposed tree are found to be significantly overestimated, the geology and biology might more easily be accommodated.

Palaeogeographic implications of a new iocrinid crinoid (Disparida) from the Ordovician (Darriwillian) of Morocco

Complete, articulated crinoids from the Ordovician peri-Gondwanan margin are rare. Here, we describe a new species, Iocrinus africanus sp. nov., from the Darriwilian-age Taddrist Formation of Morocco. The anatomy of this species was studied using a combination of traditional palaeontological methods and non-destructive X-ray micro-tomography (micro-CT). This revealed critical features of the column, distal arms, and aboral cup, which were hidden in the surrounding rock and would have been inaccessible without the application of micro-CT. Iocrinus africanus sp. nov. is characterized by the presence of seven to thirteen tertibrachials, three in-line bifurcations per ray, and an anal sac that is predominantly unplated or very lightly plated. Iocrinus is a common genus in North America (Laurentia) and has also been reported from the United Kingdom (Avalonia) and Oman (middle east Gondwana). Together with Merocrinus, it represents one of the few geographically widespread crinoids during the Ordovician and serves to demonstrate that faunal exchanges between Laurentia and Gondwana occurred at this time. This study highlights the advantages of using both conventional and cutting-edge techniques (such as micro-CT) to describe the morphology of new fossil specimens.

Hypothesis of homeothermy evolution on isolated South China Craton that moved from equator to cold north latitudes 250-200Myr ago

Based on avian and mammalian fossils found in the northeastern Chinese province of Liaoning and physiological traits linked to homeothermy, a hypothesis of evolution of homeothermic animals is proposed. It is based on the importance of muscle function in cold environment, as a strong selection pressure that favors endothermic metabolism during periods of cold climates. The presented hypothesis postulates that in progressively cooling environment, animals will develop thermal insulation, increased basal metabolism if food is available, and torpor when food is scarce. Since late Permian, Triassic and Cretaceous global temperatures were high, an exceptional place that gradually became cold was needed for the homeothermy evolution. South China Craton is here proposed as a plausible candidate for that role since it drifted across the Paleo-Tethys ocean, from equator to high northern latitudes in a journey that lasted from 250 to 200Myr ago. After this small continent collided with North China Craton some 200Myr ago, the already cold-adapted animals had spread to large, mostly empty spaces on the North China Craton, due to their evolutionary advantage of making active living in the cold environment. The most advantageous early homeothermic animals went further north to the cold Liaoning to start an oasis that delivered modern birds during next 50Myr. Modern mammals possibly evolved somewhere in the cold vicinity. This made Liaoning and similarly cold places the cradles of early birds and early mammals since for the following millions of years these places remained too cold for poikilotherms to enter and warm enough for homeotherms to dwell, until the Cretaceous-Paleogene extinction event and subsequent global cooling that diminished poikilotherms. Homeothermy was probably even more important as a survival advantage in cooler climates of Paleogene, when mammals and birds became dominant animals. This interpretation is probably supported by a recent report that a small primate Archicebus achilles dated ~55Myr ago was found in the more south central China Hubei Province, while Hadrocodium wui, extinct mammaliaform that lived 195Myr ago in what is now the Yunnan province in southwestern China. The final confirmation of the proposed scenario would be to find somewhere in South China avian fossils older than those found in Liaoning, or to find the cradle of early mammals somewhere in Northern China.