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P V Tobias

Publications and source records attributed to P V Tobias.

At least 19 recordsLinked to original sources
PubMed2006

Bone breccias, bone dumps, and sedimentary sequences of the western Limeworks, Makapansgat, South Africa.

The sediments in the western side of the Makapansgat Limeworks were either precipitated as speleothems, represented in the earlier massive deposits, or were deposited as coarsening clastic sediments, mainly representing later deposits. Between the earlier deposits and the main sedimentary phase, the stratigraphic sequence was inverted twice to a considerable height by the unusual deposition of subaqueous speleothem. Bone-bearing deposits, including the Main Quarry Bone Breccia and the well-known Grey Breccia belong, in time, to the lower part of the clastic deposits called the Red Silts. Australopith fossils have been found in the Grey Breccia dumped material and, in situ, from the dolomite clast breccia on the Main Quarry entrance buttress. Whatever the problems may be in provenancing some of the material from the Limeworks dumps, there is no doubt that the three rows of blocks on the southern side of the dumps belong to the Grey Breccia, and other rows contain red sediment sufficient for them to be safely associated with the Red Silts. There is no reason why this material should not be prepared with confidence as to its stratigraphic provenance. In any case, stratigraphic evidence, presented here, shows that there is little difference in time between the deposition of the bone-bearing breccias.

Animals↗
PubMed2001

Re-creating ancient hominid virtual endocasts by CT-scanning.

Probably the first radiographic study of human fossils, that by D. Gorganovic-Kramberger on Neandertal remains from Krapina, Croatia, was published in 1906, only 11 years after Röntgen announced the discovery of X-rays. Many subsequent studies on fossil hominids used regular clinical diagnostic radiological apparatus, as depicted in Atlas of Radiographs of Early Man by M.F. Skinner and G.H. Sperber (1982). Some specimens such as crania filled with heavily calcified matrix proved intractable. Ordinary radiographs of such specimens usually failed to reveal endocranial structure, as fossilized bone and calcified endocast were approximately equally radio-opaque. Thus, neither endocranial volume nor structural details were detectable. The only invasive method that could have been employed involved mechanical removal of the solid matrix, but this entailed hazards to the cranial vault and the destruction of the natural endocranial cast. In 1983--1984, G.C. Conroy and M. Vannier utilized recent advances in high-resolution computed tomography to produce non-invasive, intracranial capacity measurements of matrix-filled fossil skulls. They tried the method on two fossil mammal skulls filled with hard sandstone matrix (1984, Science 26:456-458), and then successfully applied it to a South African, matrix-filled cranium of the ancient hominid (hominin) species, Australopithecus africanus from Makapansgat (Conroy et al. 1990, Science 247:838-841). Details of the morphology of the endocranial surface of the braincase were revealed, including the pattern of venous sinus drainage in the posterior cranial fossa. A group based in St. Louis, Vienna, Paris, Rome, and Johannesburg has taken such studies further. Beautiful "virtual endocasts" have been produced on a large male specimen of A. africanus from Sterkfontein, South Africa, and the endocranial capacity has been determined (1998). The methods make it possible to re-create "virtual endocasts" of ancient hominids.

Cephalometry↗
PubMed1999

Hip bone trabecular architecture shows uniquely distinctive locomotor behaviour in South African australopithecines.

Cancellous bone retains structural and behavioural properties which are time and strain-rate dependent. As the orientation of the trabeculae (trajectories) follows the direction of the principal strains imposed by daily loadings, habitual postural and locomotor behaviours are responsible for a variety of trabecular architectures and site-specific textural arrangements of the pelvic cancellous network. With respect to the great ape condition, the human trabecular pattern is characterized by a distinctive ilioischial bundle, an undivided sacropubic bundle, and a full diagonal crossing (approximately 100 degrees) over the acetabulum between the ilioischial and the sacropubic bundles. Advanced digital image processing (DIP) of hip bone radiographs has revealed that adolescent and adult South African australopithecines retained an incompletely developed human-like trabecular pattern associated with gait-related features that are unique among the extant primates.

Adolescent↗
PubMed1999

A large male hominin cranium from Sterkfontein, South Africa, and the status of Australopithecus africanus.

Stw 505 is the most complete hominin cranium discovered in Sterkfontein Member 4 since Broom's excavations. It was found in situ in Member 4 breccia in 1989 and is larger, on the whole, than any other cranium from Sterkfontein that has comparable parts. Displacement due to breakage, as well as plastic deformation, has affected Stw 505 in several areas, especially the face and the vault. Diagnosticmorphology is nevertheless abundant in the specimen. In several areas-the distinct anterior pillar, the straight inferior border of the zygoma, the pattern of cresting on the naso-alveolar clivus, the basal aspect of the temporal bone-Stw 505 closely matches the morphology of specimens of Australopithecus africanus and is distinct from other hominins. Some isolated characters overlap with other groups, mainly early Homo and/or A. robustus. However, only the hypodigm of A. africanus can accommodate the entire suite of morphology.In some cases, Stw 505 introduces more variation into the Sterkfontein sample. For example, prominent superciliary eminences occupy the medial portions of the supraorbital region and flow medially into a strongly protruding glabellar mound. These characteristics are probably attributable to sexual dimorphism. In many respects, Stw 505 highlights similarities between A. africanus and early Homo. Comparison with other species suggests that males of A. africanus do not show derived features of A. robustus that are not also present in females, and that cranial differences between A. afarensis and A. africanus have, if anything, been understated.

Animals↗
PubMed1998

Endocranial capacity in an early hominid cranium from Sterkfontein, South Africa.

Two- and three-dimensional computer imaging shows that endocranial capacity in an approximately 2.8- to 2.6-million-year-old early hominid cranium (Stw 505) from Sterkfontein, South Africa, tentatively assigned to Australopithecus africanus, is approximately 515 cubic centimeters. Although this is the largest endocranial capacity recorded for this species, it is still markedly less than anecdotal reports of endocranial capacity exceeding 600 cubic centimeters. No australopithecine has an endocranial capacity approaching, let alone exceeding, 600 cubic centimeters. Some currently accepted estimates of early hominid endocranial capacity may be inflated, suggesting that the tempo and mode of early hominid brain evolution may need reevaluation.

Animals↗
PubMed1998

The mixed dentition and associated skull fragments of a juvenile fossil hominid from Sterkfontein, South Africa.

In April-May 1983, the late A.R. Hughes and his field team recovered more than 40 bone fragments and teeth from a single solution pocket of the Sterkfontein Formation. After preparation and reconstruction by JMC, it was recognised that these fragments represent a single juvenile individual (Stw 151), consisting of more than 40 cranial and dental parts, with mixed dentition. It constitutes the most complete set of jaws and teeth of an early hominid child since the Taung child was recovered in 1924. In this paper, the morphological and metrical features of the individual teeth are described. The other associated skull fragments (right ramus of the mandible, left petrous bone, right glenoid region) are also described. Comparisons are made with other South (and East) African fossil hominids. The beautiful preservation simultaneously of most of the deciduous teeth and of the permanent teeth exposed in their crypts allows an accurate analysis of the developmental sequence. A report on the dental developmental status of this juvenile is presented. On the basis of the microanatomical study of the developing permanent teeth, the estimated age at death is 5.2-5.3 years. Reconstructions of the maxillary and mandibular arcades are also offered. The morphological and metrical features of Stw 151 raise the possibility that it may represent a hominid more derived towards an early Homo condition than the rest of the A. africanus sample from Member 4.

Animals↗
PubMed1995

Sterkfontein member 2 foot bones of the oldest South African hominid.

Four articulating hominid foot bones have been recovered from Sterkfontein Member 2, near Johannesburg, South Africa. They have human features in the hindfoot and strikingly apelike traits in the forefoot. While the foot is manifestly adapted for bipedalism, its most remarkable characteristic is that the great toe (hallux) is appreciably medially diverged (varus) and strongly mobile, as in apes. Possibly as old as 3.5 million years, the foot provides the first evidence that bipedal hominids were in southern Africa more than 3.0 million years ago. The bones probably belonged to an early member of Australopithecus africanus or another early hominid species.

Animals↗
PubMed1995

Fossil Homo femur from Berg Aukas, northern Namibia.

The proximal half of a hominid femur was recovered from deep within a paleokarst feature at the Berg Aukas mine, northern Namibia. The femur is fully mineralized, but it is not possible to place it in geochronological context. It has a very large head, an exceptionally thick diaphyseal cortex, and a very low collodiaphyseal angle, which serve to differentiate it from Holocene homologues. The femur is not attributable to Australopithecus, Paranthropus, or early Homo (i.e., H. habilis sensu lato). Homo erectus femora have a relatively longer and AP flatter neck, and a shaft that exhibits less pilaster than the Berg Aukas specimen. Berg Aukas also differs from early modern femora in several features, including diaphyseal cortical thickness and the degree of subtrochanteric AP flattening. The massive diaphyseal cortex of Berg Aukas finds its closest similarity within archaic H. sapiens (e.g., Castel di Guido) and H. erectus (e.g., KNM-ER 736) samples. It has more cortical bone at midshaft than any other specimen, although relative cortical thickness and the asymmetry of its cross-sectional disposition at this level are comparable with those of other Pleistocene femora. The closest morphological comparisons with Berg Aukas are in archaic (i.e., Middle Pleistocene) H. sapiens and Neandertal samples.

Adult↗
PubMed1993

Brief communication: Gladysvale: first early hominid site discovered in South Africa since 1948.

We report here the discovery of fossil hominid teeth at Gladysvale, near Johannesburg in the southern Transvaal. This find makes the site the seventh in South Africa to yield australopithecine remains and the first new early hominid-bearing locality to be found in this region since 1948. Apart from the hominid specimens, our excavations at Gladysvale have added appreciably to the abundant Plio-Pleistocene fauna previously recorded from the cave deposit. The fauna indicates that savanna conditions prevailed during deposition of at least part of the fill. Preliminary faunal dating gives an age of deposition of between c1.7 and c2.5 mya.

Animals↗
PubMed1993

The contributions of J. C. Boileau Grant to the teaching of anatomy.

J. C. B. Grant (1886-1973) as been hailed as one of the greatest teachers of anatomy in the English language. Except for those who attended his lectures at Manitoba, Toronto and Los Angeles, his reputation rests on three textbooks, the first editions of which he produced between 1937 and 1943 and which, collectively, have run to 30 editions. Salient aspects of Grant's life and of these three fine books are reviewed and appraised and, unusually in modern times, tribute is paid to him as a writer, not of research works, but of textbooks.

Anatomy↗