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The Endocast of MH1, Australopithecus sediba

Science  09 Sep 2011:
Vol. 333, Issue 6048, pp. 1402-1407
DOI: 10.1126/science.1203922

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  1. Fig. 1

    Virtual endocast of MH1 in (A) superior, (B) inferior, (C) left lateral, and (D) anterior views. Scale bar is 2 cm.

  2. Fig. 2

    Left lateral view of the MH1 virtual endocast with major surface features indicated. (A) Precentral sulcus (inferior). (B) Precentral sulcus (superior). (C) Inferior frontal sulcus. (D) Superior frontal sulcus. (E) Fronto-orbital sulcus. (F) Anterior inferior frontal gyrus. (1) Middle branch of the middle meningeal artery. (2) Posterior branch of the middle meningeal artery. (3) Coronal suture. Scale bar, 2 cm.

  3. Fig. 3

    Comparisons of virtual endocasts in (A) superior, (B) inferior, (C) anterior, and (D) left lateral views. MH1 is in the center of each cluster surrounded by a representative modern human at the top, then proceeding clockwise, Sts 60 (Australopithecus africanus), a representative chimpanzee, and Sts 5 (Au. africanus). All endocasts are scaled to the estimated volume of the MH1 endocast (420 cm3) for illustration purposes. Scale bars, 2 cm.

  4. Fig. 4

    Illustration of measurements taken on endocasts by using landmark definitions in (5), unless noted otherwise (SOM materials and methods S3). Data are reported in Table 1. Because the occipital pole in the MH1 endocast is missing, we measured absolute dimensions rather than projected dimensions in basal view (5). Mbat is the midpoint of a line drawn between the most rostral points of the temporal lobes (bat) in basal view. Mat occurs at the lateral extension of the bat-bat line to the edge of the frontal lobe in basal view. Rof is a landmark at the most rostral position on the orbital surface of the frontal lobe in basal view. This is not necessarily the same point as the frontal pole. We use the three-dimensional (3D) coordinates of the left (rof-l) and right (rof-r) landmarks to establish a mid-point (rof) on the line joining rof-l and rof-r (fig. S3). 3D coordinates of the mid-point (rof) were used to generate a landmark that was used in measuring absolute 3D linear dimensions (such as mbat-rof). Cob is the caudal boundary of the olfactory bulbs, corresponding to the cribriform plate in basal view. Rob is the rostral boundary of the olfactory bulbs, corresponding to the cribriform plate in basal view.

  5. Fig. 5

    Bivariate plots of endocast dimensions. (A) Frontal breadth at rob versus mat-mat. (B) Rob-rof versus mat-mat. (C) Mbat-cob versus mat-mat. (D) Frontal breadth at cob versus mat-mat. All units are millimeters. Open circles, adult Homo sapiens; solid circles, H. sapiens with M3 erupting or not yet erupted (same condition as in MH1); solid triangles, adult Pan troglodytes verus; open triangles, P. t. verus with M3 erupting or not yet erupted (same condition as in MH1); asterisk, MH1 (Australopithecus sediba); “Y” symbol, Sts 5 (Au. africanus); cross, Sts 60 (Au. africanus). Bracketed numbers correspond to measurements in Table 1 and definitions in Fig. 4. For comparative fossil measurements (also absolute rather than projected dimensions), see Table 1.

  6. Fig. 6

    Bivariate plot of first and second principal components. Open circles, adult Homo sapiens; solid circles, H. sapiens with M3 erupting or not yet erupted (same condition as in MH1); solid triangle, adult Pan troglodytes verus; open triangles, P. t. verus with M3 erupting or not yet erupted (same condition as in MH1); asterisk, MH1 (Australopithecus sediba); “Y” symbol, Sts 5 (Au. africanus); cross, Sts 60 (Au. africanus). The dashed lines (ellipse area) indicate 95% group membership and are computed from the bivariate normal distribution fit of principal component (PC) 1 and 2. If the ellipse collapses diagonally, the correlation between variables strengthens; a more circular ellipse indicates relatively uncorrelated variables. Dimensions driving PC 1 and PC 2 are discussed in the text and in greater detail in SOM text S4. MH1 fits just within the 95% ellipse for modern humans, whereas Sts 5 falls just beyond it, and Sts 60 is situated between modern human and chimpanzee 95% ellipses.