A Hominin Femur with Archaic Affinities from the Late Pleistocene of Southwest China
Authors:
Curnoe et al
Abstract:
The number of Late Pleistocene hominin species and the timing of their extinction are issues receiving renewed attention following genomic evidence for interbreeding between the ancestors of some living humans and archaic taxa. Yet, major gaps in the fossil record and uncertainties surrounding the age of key fossils have meant that these questions remain poorly understood. Here we describe and compare a highly unusual femur from Late Pleistocene sediments at Maludong (Yunnan), Southwest China, recovered along with cranial remains that exhibit a mixture of anatomically modern human and archaic traits. Our studies show that the Maludong femur has affinities to archaic hominins, especially Lower Pleistocene femora. However, the scarcity of later Middle and Late Pleistocene archaic remains in East Asia makes an assessment of systematically relevant character states difficult, warranting caution in assigning the specimen to a species at this time. The Maludong fossil probably samples an archaic population that survived until around 14,000 years ago in the biogeographically complex region of Southwest China.
Late Miocene vegetation dynamics under monsoonal climate in southwestern China
Authors:
Li et al
Abstract:
To better understand vegetation dynamics and the Asian monsoonal climate in the Neogene, we reconstructed the vegetational succession and climate of Wenshan basin in southwestern China during the late Miocene (11.62-5.33 Ma). We used newly available palynological data and the results of a quantitative bioclimatic analysis. The late Miocene palynoflora in Wenshan basin resembles that of modern evergreen broadleaf vegetation in subtropical East Asia. Based on pollen elements and reconstructed palaeoclimates in 72 samples, we found the composition of the vegetation in the Wenshan basin fluctuated during the late Miocene and was likely driven by natural climate variability. Quantitative estimates suggest that the mean annual temperature (MAT) ranged from 16.6 to 17.5°C; the mean annual precipitation (MAP) was ~ 1500 mm; and the monsoon intensity index (MSI) ranged from 11.3 to 17.1. Our results indicate the Wenshan basin experienced a warm, wet, and temperate to subtropical climate. By comparison with other late Miocene sites in Yunnan, we show that temperatures differed slightly from region to region and, overall, annual and seasonal precipitation levels were higher in the late Miocene than at present, but with a weaker monsoon intensity than in the Wenshan basin today.
Early Middle Triassic stromatolites from the Luoping area, Yunnan Province, Southwest China: Geobiologic features and environmental implications
Authors:
Luo et al
Abstract:
An early Middle Triassic stromatolite deposit is documented from the Guanling Formation of the Luoping area, Yunnan, SW China. The Luoping stromatolite shows five types of constructional microbial forms in various magnifications: 1) typical stratified columnar structures, up to 20 cm high, with crinkled laminae. Dark coloured laminae, 1 mm thick, are composed of upright filamentous tubes, averagely 29.4 μm in diameter, showing a vertical growth fabric. 2) Laminoid fenestrae, 0.5–1 mm wide, and 3) prostrate filaments, which are reflected by strong fluorescence in sharp contrast to dolomite cement in fluorescent images. 4) Rod-like aggregates, 4.6–18 μm in diameter, composed of minute dolomite rhombs, are very common in stromatolitic laminae; they resemble present-day cyanobacterial trichome, and thus may represent putative fossilized cyanobacteria. 5) Moreover, small pits, coccoid-like spheroids, calcified biofilms, and fibrous structures are also common in stromatolitic laminae. The last two may represent calcified extracellular polymeric substances (EPS) that contributed to the development and lithification of stromatolites. Authigenic quartz grains are common and may also have involved biological processes in stromatolite formation. Of these microbial functional-groups driving accretion and lithification processes of stromatolite documented in literature, both lithified cyanobacteria/oxygenic phototrophs and possible sulfate-reducing bacteria (SRB), which induced microbial formation of dolomite and contributed to the accretion of the Luoping stromatolite, are suggestive of biogenic origin. The Luoping stromatolite differs from the Permian–Triassic boundary microbialites (PTBMs) in having abundant filamentous structures and growing in an oxic marine environment. Both sedimentary facies analysis and abundant fossilized cyanobacteria may indicate proliferation of oxygenic phototrophs in a normal, oxic habitat during the middle Anisian (early Middle Triassic), a period when hospitable environments, coupled with biotic diversification, prevailed in South China and set an agenda for the full recovery of marine ecosystems in middle–late Anisian. However, the post-extinction stromatolites and other anachronistic facies are not necessarily indicative of anoxic or oxic conditions, and their environmental settings are much more complex than previously thought.
