Two partial vertebral columns of Australopithecus sediba grant insight into aspects of early hominin spinal mobility, lumbar curvature, vertebral formula, and transitional vertebra position. Au. sediba likely possessed five non-rib-bearing lumbar vertebrae and five sacral elements, the same configuration that occurs modally in modern humans. This finding contrasts with other interpretations of early hominin regional vertebral numbers. Importantly, the transitional vertebra is distinct from and above the last rib-bearing vertebra in Au. sediba, resulting in a functionally longer lower back. This configuration, along with a strongly wedged last lumbar vertebra and other indicators of lordotic posture, would have contributed to a highly flexible spine that is derived compared with earlier members of the genus Australopithecus and similar to that of the Nariokotome Homo erectus skeleton.
The pelagic zone of large, deep freshwater lakes features pronounced horizontal and vertical gradients of physicochemical parameters, which in turn might allow for a nonuniform occurrence of specifically adapted bacterial taxa. We, therefore, studied the spatial distribution patterns of different heterotrophic bacteria, picocyanobacteria, and the dominant primary producer, the filamentous cyanobacterium Planktothrix rubescens, in a large, canyon-shaped, prealpine lake (Lake Zurich, Switzerland), in six vertical profiles along a 21.7-km longitudinal transect. Highest total densities and proportions of cells with high nucleic acid content were in the warm epilimnion and the hypoxic zone of the hypolimnion. P. rubescens formed a dense layer in the metalimnion throughout the lake, whereas picocyanobacteria populated the water layers above. The epilimnion was mainly inhabited by ultramicrobacteria related to the LD12-lineage of Alphaproteobacteria and to Actinobacteria; the latter group preferred the shallow regions. Cytophaga-Flavobacteria, in particular a population related to Fluviicola sp. were more frequent in and below the layer of maximal P. rubescens abundances. Betaproteobacteria, on the other hand, were highly abundant in the epi-and hypolimnion, but not in the P. rubescens layer. Four betaproteobacterial subpopulations with contrasting longitudinal and/or vertical habitat preferences were distinguished: putatively methylotrophic bacteria of the LD28 lineage (beta IV) preferentially inhabited the hypolimnion, Polynucleobacter acidiphobus was found throughout the epilimnion, Limnohabitans (R-BT065) more in the shallow regions of the lake, and Polynucleobacter necessarius ssp. asymbioticus only in hypoxic waters. Our results stress the potential importance of spatial niche differentiation in freshwater bacterioplankton.
BackgroundPlacement of the glenoid baseplate is of paramount importance for the outcome of anatomical and reverse total shoulder arthroplasty. However, the database around glenoid size is poor, particularly regarding small scapulae, for example, in women and smaller individuals, and is derived from different methodological approaches. In this multimodality cadaver study, we systematically examined the glenoid using morphological and 3D-CT measurements.MethodsMeasurements of the glenoid and drill hole tunnel length for superior baseplate screw placement were recorded to define size of the glenoid and the distance to the scapular notch on cadaveric specimens. Glenoid angles were determined on both, 3D-CT-scans of the thoraxes using the Friedman method and on subsequently isolated scapulae from 18 male and female donors (average 84 years, range 60–98 years).ResultsMean glenoid height was 36.6 mm ± 3.6, and width 27.8 mm ± 3.1 with a significant sex dimorphism (p ≤ 0.001): in males, glenoid height 39.5 mm ± 3.5, and width 30.3 mm ± 3.3, and in females, glenoid height 34.8 mm ± 2.2, and width 26.2 mm ± 1.6. The average distance from the superior screw entry to its exit in the scapular notch measured by calliper was 27.2 mm ± 6.0 with a sex difference: in males, 29.4 mm ± 5.7, and in females, 25.8 mm ± 5.9 mm with a minimum recorded distance of 15 mm. Measured by CT, the mean inclination angle for male and female donors combined was 13.0° ± 7.0, and the ante-/retroversion angle −1.0° ± 4.0°.ConclusionThis study is one of the first to combine dissection, including drill holes, with anatomical measurements and radiological data. In some women and smaller individuals, smaller baseplates should be selected. The published safe zone of 20 mm is generally feasible for superior screw placement, however, in small patients this distance may be substantially shorter than expected and start as of 13 and 15 mm, respectively. No correlation between glenoid height or width with the length of our drilling canal towards the scapular notch was found. Preoperative CT-based treatment planning to determine version and inclination angles is recommended.
Although the early postural reconstructions of the Neandertals as incompletely erect were rejected half a century ago, recent studies of Neandertal vertebral remains have inferred a hypolordotic, flat lower back and spinal imbalance for them, including the La Chapelle-aux-Saints 1 skeleton. These studies form part of a persistent trend to view the Neandertals as less “human” than ourselves despite growing evidence for little if any differences in basic functional anatomy and behavioral capabilities. We have therefore reassessed the spinal posture of La Chapelle-aux-Saints 1 using a new pelvic reconstruction to infer lumbar lordosis, interarticulation of lower lumbar (L4-S1) and cervical (C4-T2) vertebrae, and consideration of his widespread age-related osteoarthritis. La Chapelle-aux-Saints 1 exhibits a pelvic incidence (and hence lumbar lordosis) similar to modern humans, articulation of lumbar and cervical vertebrae indicating pronounced lordosis, and Baastrup disease as a product of his advanced age, osteoarthritis, and lordosis. Our findings challenge the view of generally small spinal curvatures in Neandertals. Setting aside the developmentally abnormal Kebara 2 vertebral column, La Chapelle-aux-Saints 1 is joined by other Neandertals with sufficient vertebral remains in providing them with a fully upright (and human) axial posture.
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