New Specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia

Two new specimens of the oviraptorid theropod Nemegtomaia barsboldi from the Nemegt Basin of southern Mongolia are described. Specimen MPC-D 107/15 was collected from the upper beds of the Baruungoyot Formation (Campanian-Maastrichtian), and is a nest of eggs with the skeleton of the assumed parent of Nemegtomaia on top in brooding position. Much of the skeleton was damaged by colonies of dermestid coleopterans prior to its complete burial. However, diagnostic characters are recovered from the parts preserved, including the skull, partial forelimbs (including the left hand), legs, and distal portions of both feet. Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs. The second new specimen, MPC-D 107/16, was collected a few kilometers to the east in basal deposits of the Nemegt Formation, and includes both hands and femora of a smaller Nemegtomaia individual. The two formations and their diverse fossil assemblages have been considered to represent sequential time periods and different environments, but data presented here indicate partial overlap across the Baruungoyot-Nemegt transition. All other known oviraptorids from Mongolia and China are known exclusively from xeric or semi-arid environments. However, this study documents that Nemegtomaia is found in both arid/aeolian (Baruungoyot Formation) and more humid/fluvial (Nemegt Formation) facies

Modeling the interactions between river morphodynamics and riparian vegetation

The study of river-riparian vegetation interactions is an important and intriguing research field in geophysics. Vegetation is an active element of the ecological dynamics of a floodplain which interacts with the fluvial processes and affects the flow field, sediment transport, and the morphology of the river. In turn, the river provides water, sediments, nutrients, and seeds to the nearby riparian vegetation, depending on the hydrological, hydraulic, and geomorphological characteristic of the stream. In the past, the study of this complex theme was approached in two different ways. On the one hand, the subject was faced from a mainly qualitative point of view by ecologists and biogeographers. Riparian vegetation dynamics and its spatial patterns have been described and demonstrated in detail, and the key role of several fluvial processes has been shown, but no mathematical models have been proposed. On the other hand, the quantitative approach to fluvial processes, which is typical of engineers, has led to the development of several morphodynamic models. However, the biological aspect has usually been neglected, and vegetation has only been considered as a static element. In recent years, different scientific communities (ranging from ecologists to biogeographers and from geomorphologists to hydrologists and fluvial engineers) have begun to collaborate and have proposed both semiquantitative and quantitative models of river-vegetation interconnections. These models demonstrate the importance of linking fluvial morphodynamics and riparian vegetation dynamics to understand the key processes that regulate a riparian environment in order to foresee the impact of anthropogenic actions and to carefully manage and rehabilitate riparian areas. In the first part of this work, we review the main interactions between rivers and riparian vegetation, and their possible modeling. In the second part, we discuss the semiquantitative and quantitative models which have been proposed to date, considering both multi- and single-thread river

The first oviraptorosaur (Dinosauria: Theropoda) bonebed: Evidence of gregarious behaviour in a maniraptoran theropod

A monodominant bonebed of Avimimus from the Nemegt Formation of Mongolia is the first oviraptorosaur bonebed described and the only recorded maniraptoran bonebed from the Late Cretaceous. Cranial elements recovered from the bonebed provide insights on the anatomy of the facial region, which was formerly unknown in Avimimus. Both adult and subadult material was recovered from the bonebed, but small juveniles are underrepresented. The taphonomic and sedimentological evidence suggests that the Avimimus bonebed represents a perimortem gregarious assemblage. The near absence of juveniles in the bonebed may be evidence of a transient age-segregated herd or ‘flock’, but the behaviour responsible for this assemblage is unclear. Regardless, the Avimimus bonebed is the first evidence of gregarious behaviour in oviraptorosaurs, and highlights a potential trend of increasing gregariousness in dinosaurs towards the end of the Mesozoic

Molecular evidence for bacterial mediation of calcite formation in cold high-altitude caves

Three samples of moonmilk from high-altitude caves in northeast Italy were analysed for their lipid biomarker content, providing the first organic geochemical investigation into the relationship between cave bacterial communities and calcitic speleothems. The results demonstrate a positive association between the moonmilk deposits analysed and bacterial input, which we propose relates to bio-mediation of calcite nucleation processes. Comparison of the analysed moonmilk and a stalagmite from a geographically and climatically related cave suggest that this association is at least partially driven by the characteristics of the soil and overlying vegetation, thus demonstrating the potential use of moonmilk in palaeoenvironmental research