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[Display omitted] • SHRIMP age of Kamthai carbonatite-hosted REE deposit is 68.4 ± 1.8 Ma. • Unambiguously links it to the Deccan Large Igneous Province. • One of earliest manifestations of the Réunion hotspot in the Indian sub-continent. • CO 2 outgassing, by carbonatitic eruptions, triggered K-Pg boundary mass extinction. The carbonatite plug at Kamthai in the Late Cretaceous polychronous (66–89 Ma) Sarnu- Dandali alkaline complex (SDAC), NW India, is India's only known carbonatite-hosted rare- earth-element deposit. The SDAC intrudes the Neoproterozoic (∼750 Ma) Malani silicic igneous suite in the Aravalli raton. The Kamthai carbonatite is a calcio-carbonatite dominated by calcite along with barite, strontianite, quartz, zircon and REE-bearing minerals. Textural features suggest an open-system exchange of the magma chamber at varying depths of crystallization. REE patterns are smooth and characterized by strong LREE enrichment, as typical of carbonatites. SHRIMP dating of 12 spots on three magmatic zircons from the carbonatite yielded a concordia age of 66.1 ± 1.4 Ma and an indistinguishable average 206Pb/238U mean age of 68.4 ± 1.8 Ma. The obtained U-Pb ages unambiguously link the carbonatite emplacement to the Deccan Large Igneous Province, i.e. the Réunion hotspot near the K-Pg (Cretaceous-Paleogene) boundary in the polychronous set-up of the SDAC. These ages are also indistinguishable from the 68.53 ± 0.16 Ma magmatic pulse recorded from the nearby Mundwara polychronous alkaline complex and the 69.7 ± 0.2 Ma alkaline sills from the Tethyan suture zone in Pakistan, which are regarded to be earliest manifestations of the Réunion hotspot in the Indian sub-continent. Our results in the context of REE mineralization in the Kamthai deposit have also implications with respect to CO 2 outgassing, induced by at least four near-synchronous carbonatitic eruptions in NW India, and to triggering the mass extinction near the K-Pg boundary. [ABSTRACT FROM AUTHOR]

Vertebrates developed tooth replacement over 400 million years ago. Then, 200 million years later, the combination of vertical tooth replacement with the thecodont implantation (teeth in bone sockets) appeared a key morphological innovation in mammalian evolution. However, we discovered that an extinct fish taxon, Serrasalmimus secans, showed the same innovation in the lineage Serrasalmimidae, which survived the end Cretaceous mass extinction event. The carnassial teeth are known in both mammals and pycnodont fish, but these teeth do not share the same tissues or developmental processes. Therefore, this serrasalmimid pycnodont fish might have independently acquired mammal-like tooth replacement and implantation, indicating that the fish and mammals convergently evolved the carnassial dental morphologies at about the same time, approximately 60 My ago, in separate ecosystems.

The Cretaceous-Paleogene Boundary (KPB), the only known global impact ejecta layer, resulted from the Chicxulub Impact Event (66 Ma). KPB is well-documented across the different distal locations (paleodistances >5000 km), yet an understanding on the preservation of KPB remains evasive. Identification of the different preservation controls is thus quintessential, especially when the distal KPB maintains a constant thickness of 2–5 mm globally. We evaluate 84 distal KPB sites (as exposed on land today) through review and assessment of different parameters. The parameters include current geological provinces, nearest active tectonic boundary, geomorphic setting, lithological associations, paleoposition (at 66 Ma), paleodistance from impact point (at 66 Ma), paleoclimate and paleobathymetry. The most common geological province, closest plate boundary type and geomorphic setting are accretionary complex (43 sites), collisional boundary (53 sites) and bedrock mountain (35 sites), respectively. KPB layer manifests in different lithologies, but most commonly in clay, marl, clay-limestone, and clay-marl dominant litho-units. At 66 Ma, 68 KPB deposited in marine settings, meanwhile only 16 in terrestrial conditions. Cenozoic paleobathymetry depicts the increased exposure of KPB sites to non-marine settings as time progresses (Paleocene-Holocene). During Cenozoic, the warm temperate climate remains the dominant climate across majority of the distal KPB sites. Evaluation of the different parameters leads to the conclusion that the preservation of KPB is aided by deposition within sedimentary basins in marine conditions during early Paleocene, presence of thick sedimentary units overlying KPB and dominance of low-denudational climates (warm temperate/subtropical arid) during Cenozoic. Furthermore, the study weighs the Chicxulub ejecta transport mechanisms by assessing the different chemical (Ir-anomaly, boundary clay) and physical attributes (impact spherules, shocked minerals, Ni-rich spinels) at KPB. The observations support the dust cloud (non-ballistic) model of ejecta transportation and emplacement over the ballistic ejecta plume model. [Display omitted] • Reviewed 84 distal Cretaceous-Paleogene Boundary (KPB) sites. • Ejecta distribution trends favour the dust cloud model of ejecta emplacement. • Ir-anomaly found across 52 KPB, even at paleodistance of 16,549 km. • Accretionary complexes and collisional boundaries are associated with majority of the KPB sites. • Marine sedimentary basins are ideal sites for distal KPB preservation. [ABSTRACT FROM AUTHOR]

Modern tropical rainforests have the highest biodiversity of terrestrial biomes and are restricted to three low-latitude areas. However, the actual timeframe during which tropical rainforests began to appear on a global scale has been intensely disputed. Here, we used the moonseed family (Menispermaceae), an important physiognomic and structural component of tropical rainforests on a worldwide basis, to obtain new insights into the diversification of this biome., We integrated phylogenetic, biogeographic and molecular dating methods to analyse temporal and spatial patterns of global diversification in Menispermaceae., Importantly, a burst of moonseed diversification occurred in a narrow window of time, which coincides with the Cretaceous-Paleogene (K-Pg) boundary. Our data also suggest multiple independent migrations from a putative ancestral area of Indo-Malay into other tropical regions., Our data for Menispermaceae suggest that modern tropical rainforests may have appeared almost synchronously throughout the three major tropical land areas close to, or immediately following, the K-Pg mass extinction. [ABSTRACT FROM AUTHOR]

Vertebrates developed tooth replacement over 400 million years ago. Then, 200 million years later, the combination of vertical tooth replacement with the thecodont implantation (teeth in bone sockets) appeared a key morphological innovation in mammalian evolution. However, we discovered that an extinct fish taxon, Serrasalmimus secans , showed the same innovation in the lineage Serrasalmimidae, which survived the end Cretaceous mass extinction event. The carnassial teeth are known in both mammals and pycnodont fish, but these teeth do not share the same tissues or developmental processes. Therefore, this serrasalmimid pycnodont fish might have independently acquired mammal-like tooth replacement and implantation, indicating that the fish and mammals convergently evolved the carnassial dental morphologies at about the same time, approximately 60 My ago, in separate ecosystems.

Determining the timing of diversification of modern birds has been difficult. We combined DNA sequences of clock-like genes for most avian families with 130 fossil birds to generate a new time tree for Neornithes and investigated their biogeographic and diversification dynamics. We found that the most recent common ancestor of modern birds inhabited South America around 95 million years ago, but it was not until the Cretaceous-Paleogene transition (66 million years ago) that Neornithes began to diversify rapidly around the world. Birds used two main dispersion routes: reaching the Old World through North America, and reaching Australia and Zealandia through Antarctica. Net diversification rates increased during periods of global cooling, suggesting that fragmentation of tropical biomes stimulated speciation. Thus, we found pervasive evidence that avian evolution has been influenced by plate tectonics and environmental change, two basic features of Earth's dynamics.