Reconstructed Homo habilis Suggests Homo (Human) Genus Family Tree Rather Bushy

Reconstructed Homo habilis type OH 7 suggests deep-rooted species diversity in early Homo

Authors:

Spoor et al

Abstract:

Besides Homo erectus (sensu lato), the eastern African fossil record of early Homo has been interpreted as representing either a single variable species, Homo habilis1, or two species. In the latter case, however, there is no consensus over the respective groupings, and which of the two includes OH 7, the 1.8-million-year-old H. habilis holotype. This partial skull and hand from Olduvai Gorge remains pivotal to evaluating the early evolution of the Homo lineage, and by priority names one or other of the two taxa. However, the distorted preservation of the diagnostically important OH 7 mandible has hindered attempts to compare this specimen with other fossils. Here we present a virtual reconstruction of the OH 7 mandible, and compare it to other early Homo fossils. The reconstructed mandible is remarkably primitive, with a long and narrow dental arcade more similar to Australopithecus afarensis than to the derived parabolic arcades of Homo sapiens or H. erectus. We find that this shape variability is not consistent with a single species of early Homo. Importantly, the jaw morphology of OH 7 is incompatible with fossils assigned to Homo rudolfensis and with the A.L. 666-1 Homo maxilla. The latter is morphologically more derived than OH 7 but 500,000 years older, suggesting that the H. habilis lineage originated before 2.3 million years ago, thus marking deep-rooted species diversity in the genus Homo. We also reconstructed the parietal bones of OH 7 and estimated its endocranial volume. At between 729 and 824 ml it is larger than any previously published value, and emphasizes the near-complete overlap in brain size among species of early Homo. Our results clarify the H. habilis hypodigm, but raise questions about its phylogenetic relationships. Differences between species of early Homo appear to be characterized more by gnathic diversity than by differences in brain size, which was highly variable within all taxa.

Reconstruction of the Hind Limb of Santacrucian Miocene Neogene Sloths From Patagonia

Muscular Reconstruction and Functional Morphology of the Hind Limb of Santacrucian (Early Miocene) Sloths (Xenarthra, Folivora) of Patagonia

Authors:

Toledo et al

Abstract:

This article presents a morphofunctional analysis of the hind limb of Santacrucian (Early Miocene) sloths from southernmost Patagonia (Argentina). These fossil sloths were mid sized to large animals, ranging from 40 to 120kg, and their postcranial skeleton was markedly different in shape compared to that of extant tree sloths, which vary from 2 to 10kg. The functional anatomy of the hind limb of Santacrucian sloths was compared with that of living xenarthrans (tree sloths, anteaters and armadillos), which involved reconstruction of the hind limb musculature and comparative and qualitative morphofunctional analyses, and hypotheses on the biological role of the hind limb in terms of preferences in substrate, posture and strategies of locomotion were formulated. The hind limb of Santacrucian sloths bears strong resemblances to that of living South American anteaters in stoutness of skeletal elements, form of the characteristics related to muscular and ligamentous attachments, and conservative, pentadactylous strong-clawed pes. The musculature was very well developed, allowing powerful forces, principally in entire limb adduction, crus flexion and extension, pes extension and toe prehension. These functional features, together with those of the forelimb, are congruent with climbing behavior, and support the hypothesis that Santacrucian sloths were good but slow climbing mammals. However, their climbing strategies were limited, owing principally to their comparatively large body size, and they relied to a large extent on their powerful musculature and curved manual and pedal unguals for both moving and standing on the arboreal supports. This article is protected by copyright. All rights reserved.

Proterozoic Isotopic Evidence Patagonia was Linked to Africa and Antarctica

Mesoproterozoic and Paleoproterozoic subcontinental lithospheric mantle domains beneath southern Patagonia: Isotopic evidence for its connection to Africa and Antarctica

Authors:

Mundl et al

Abstract:

New isotopic studies on mantle xenoliths from Santa Cruz Province, southern Patagonia, Argentina, reveal that at least three discrete subcontinental lithospheric mantle (SCLM) domains—the Deseado Massif, Tres Lagos, and Pali Aike—form the southernmost part of South America. Re-Os systematics yield early Paleoproterozoic (up to 2.5 Ga) SCLM formation ages (rhenium depletion ages, TRD) for Pali Aike spinel peridotites, while samples from the Deseado Massif and Tres Lagos indicate a younger SCLM origin with Neoproterozoic to Mesoproterozoic (0.9–1.3 Ga) and Mesoproterozoic to late Paleoproterozoic (1.3–1.9 Ga) TRD ages, respectively. Hf-Sr-Nd isotopic compositions indicate metasomatic overprinting of the majority of the samples, which, however, has not affected the Os isotopic system. Based on similar formation ages, the geological evolution of the Deseado Massif is most likely connected to the evolution of the Namaqua-Natal belt of South Africa. TRD ages from SCLM domains underneath Tres Lagos and Pali Aike indicate a common origin with crustal sections from Shackleton Range, Antarctica, positioning the southern tip of South America closer to west Antarctica in the reconstructed Rodinia supercontinent than previously assumed.

The Tussle Over the Croc-like Spinosaurus Goes on

link.

a 3d Video Reconstruction of a 410 million Year old Pragian/Lochkovian Devonian Arachnid

Researchers from The University of Manchester and the Museum für Naturkunde, Berlin, used exceptionally preserved fossils from the Natural History Museum in London to create the video showing the most likely walking gait of the animal; the study is published in a special issue of the Journal of Paleontology today (Wednesday).

The scientists used the fossils - thin slices of rock showing the animal's cross-section - to work out the range of motion in the limbs of this ancient, extinct early relative of the spiders. From this, and comparisons to living arachnids, the researchers used an open source computer graphic program called Blender to create the video showing the animals walking.

"When it comes to early life on land, long before our ancestors came out of the sea, these early arachnids were top dog of the food chain," said author Dr Russell Garwood, a palaeontologist in the University of Manchester's School of Earth, Atmospheric and Environmental Sciences. "They are now extinct, but from about 300 to 400 million years ago, seem to have been more widespread than spiders. Now we can use the tools of computer graphics to better understand and recreate how they might have moved – all from thin slivers of rock, showing the joints in their legs."

Co-author Jason Dunlop, a curator at the Museum für Naturkunde, Berlin, said: "These fossils – from a rock called the Rhynie chert – are unusually well-preserved. During my PhD I could build up a pretty good idea of their appearance in life. This new study has gone further and shows us how they probably walked. For me, what's really exciting here is that scientists themselves can make these animations now, without needing the technical wizardry – and immense costs – of a Jurassic Park-style film.

link.

The Three-dimensional Structure of NeoArchean Microbialites

Unraveling the three-dimensional morphology of Archean microbialites

Authors:

Juarez Rivera et al

Abstract:

Fenestrate microbialites from the 2521±3 Ma Gamohaan Formation, South Africa, are composed of calcite with traces of kerogen that represent the remains of ancient microbial mats. To delineate the 3-D geometry of these microbialites, specimens were serial-sectioned; sequential slices were polished in 120 μm increments and scanned to yield an image stack, which was rendered into a virtual model of the microbialites. The resulting virtual representation allowed for visualization and characterization of microbial growth geometries that were not visible from 2-D surfaces. Several new insights into the structure of microbialites emerged from characterizing their 3-D structure including the recognition of two new features, linear structures and tubular structures. The long, thin nature of these structures makes them difficult to identify in two dimensions. However, in three dimensions, they can be traced as thin ropes of fossilized microbial communities emerging from more typical microbial mat structures. Overall, these results demonstrate a new set of microbial features in the Gamohaan Formation that were only characterized by reconstructing the full geometry of the microbialites in three dimensions.

A New Reconstruction of Anomalocaris

Morphology of Anomalocaris canadensis from the Burgess Shale

Authors:

Daley et al

Abstract:

Recent description of the oral cone of Anomalocaris canadensis from the Burgess Shale (Cambrian Series 3, Stage 5) highlighted significant differences from published accounts of this iconic species, and prompts a new evaluation of its morphology as a whole. All known specimens of A. canadensis, including previously unpublished material, were examined with the aim of providing a cohesive morphological description of this stem lineage arthropod. In contrast to previous descriptions, the dorsal surface of the head is shown to be covered by a small, oval carapace in close association with paired stalked eyes, and the ventral surface bears only the triradial oral cone, with no evidence of a hypostome or an anterior sclerite. The frontal appendages reveal new details of the arthrodial membranes and a narrower cross-section in dorsal view than previously reconstructed. The posterior body region reveals a complex suite of digestive, respiratory, and locomotory characters that include a differentiated foregut and hindgut, a midgut with paired glands, gill-like setal blades, and evidence of muscle bundles and struts that presumably supported the swimming movement of the body flaps. The tail fan includes a central blade in addition to the previously described three pairs of lateral blades. Some of these structures have not been identified in other anomalocaridids, making Anomalocaris critical for understanding the functional morphology of the group as a whole and corroborating its arthropod affinities.

The Face of the Hobbit (H. floresiensis)

It seems overly human to me, in the nose, at least, but I am not a forensic anthropologist.

Also seen here.