Ectocranial (top right) and endocranial (top left) close-up views of the OH 81 fossil, accompanied by magnifications of the porotic hyperostosis paleopathology as observed ectocranially (lower left) and edge-on at the diploic-table junction (lower right).

<p>Scale = 1 mm.</p

Aerial view of Olduvai Gorge (Tanzania) with the approximate site of SHK indicated.

<p>The inset shows the current excavations at the site.</p

Endocranial (bottom left) and and ectocranial (bottom right) views of the OH 81 fossil (lower) compared to a parietal fragment of a modern human child in the same views.

<p>The parietomastoid suture and the lambdoid sutures form the inferior border of OH 81. Superior is up in both images, anterior is to the left in the lefthand image and to the right in the righthand image. Scale = 1 cm.</p

PCA showing the OH80 radius compared to other australopithecine and Homo fossils.

<p>A, confirmatory PCA of the variables analyzed for several fossil hominin proximal radial specimens (excluding the variable AP ratio, since predictive diagrams suggested that it was not diagnostic and that it had three times more predictive error margin than the variable with the smallest error and 50% more error than the other variables). The PCA yielded a two-component solution, which accounted for 91.9% of the sample variance. Dimension 1 accounted for 70% of the sample variance; dimension 2 explained the remaining 21.9% of variance. The variables showing the highest scores in factor 1 were MIA (.51), RAPA (−.50), RMPA (−.48) and RFD (−.47). In the second factor, RFE yielded the highest score (.97). B, A similar distribution of the sample can be observed in a MDS analysis, which reached a solution after 77 iterations, consisting of a two-dimensional solution explaining 89.2% of sample variance. The first dimension (71% of inertia) showed the same variables selected as in the PCA but with different scores: MIA (.89), RAPA (.28), RMPA (−.23), RFD(.24). The second dimension is defined by RFD (−.73). Abbreviations: medial proximal-distal intersecting angle (MIA); relative fovea diameter (RFD); relative fovea eccentricity (RFE); relative anterior proximal articular surface width (RAPA); relative medial proximal articular surface width (RMPA) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080347#pone.0080347-Patel1" target="_blank">[25]</a>. Horizontal axes display the first dimension and vertical axes show the second dimension of data. Fossils (catalog number, species): KNM-ER 20419, <i>Australopithecus anamensis</i>; AL-288-1p, <i>Australopithecus afarensis</i>; StW 431, <i>Australopithecus africanus</i>; StW 139, <i>Australopithecus africanus</i>; SKX 3699, <i>Paranthropus robustus</i>; SKX 24601, <i>Paranthropus robustus</i>; KNM-ER 1500, <i>Paranthropus boisei</i>; SK18b; <i>Homo erectus</i>; SK 2045, (?) <i>Homo erectus</i>.</p

Section properties of proximal femora (at 80% length[1 cm inferior to the lesser trochanter]) of two <i>Paranthropus robustus</i> specimens [37] and OH80.

<p>CA, cortical area; MA, medullary area; TA, total periosteal area; %CA, [(CA/TA) · 100); Ix, second moment of area about X (ML) axis (AP bending rigidity); Iy, second moment of area about y (AP) axis (ML bending rigidity); J, polar second moment of area. Areas in mm², second moments of area in mm⁴.</p>*<p>Measurements from the proximal shaft were obtained near the top of the preserved section, slightly at the same undertrochanteric section as suggested by Ruff et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080347#pone.0080347-Ruff1" target="_blank">[37]</a>.</p

Hominin dental remains from Level 4 at the BK site.

<p>Teeth are shown in approximate anatomical position on a schematic dental arcade; anterior teeth are shown in labial view, postcanine teeth in occlusal view (A). Labial views of the anterior teeth are shown in (B). Photographs of individual teeth by J Trueba and MJ Ortega; composition by JL Heaton.</p

Cross-sectional properties of femoral 50% sections of OH80 and KNM-ER 1808 (<i>Homo erectus</i>).

<p>CA, cortical area; MA, medullary area; TA, total periosteal area; %CA, [(CA/TA) · 100); Ix, second moment of area about X (ML) axis (AP bending rigidity); Iy, second moment of area about y (AP) axis (ML bending rigidity); J, polar second moment of area. Areas in mm², second moments of area in mm⁴.</p>*<p>Measurements taken directly on the proximal break of the shaft at the mid-section.</p

Ulna (OH36) found in upper Bed II and attributed to Paranthropus (upper) compared to the OH80-11 radius (lower) (Photo: Mario Torquemada).

<p>Ulna (OH36) found in upper Bed II and attributed to Paranthropus (upper) compared to the OH80-11 radius (lower) (Photo: Mario Torquemada).</p

Comparative metric analysis of the OH80 dentition and the <i>Paranthropus boisei</i> available sample (obtained from the reference 9 and the Human Origins Data Base: http://humanoriginsdatabase.org), including OH5.

*<p>Paranthropus boisei.</p><p>Data for <i>Paranthropus boisei</i> include mean values plus range (minimum and maximum). Measurements are in mm.</p

The right femur (OH 80-12; left side of image) and right radius (OH 80-11; right side of image) of the OH 80 hominin from Level 4 at the BK site.

<p>Both fossils are shown in posterior view; superior is at the top of the image; the bar scale = 1 cm.</p