AMERICAN JOURNAL zyxwvu OF PHYSICAL ANTHROPOLOGY 57:501-544 zy (1982) zy Pliocene Hominid Mandibles From the Hadar Formation, Ethiopia: 1974-1 977 Collections TIM D. WHITE AND DONALD C. JOHANSON Department ofdnthmplogy, zyxwvu The University of California, Berkeley, California 94720 (T.D.W.);Cleveland Museum of Natuml History, Cleveland, Ohio 44106 (D.C.J.); Institute of Human Origins, 2700 Bancmf? Way, Berkeley, California (D.CJ) KEY WORDS zyxwvut Hominid, Pliocene, Mandible ABSTRACT Ethiopia are described anatomically. The Pliocene hominid mandibles of A. afarensis from Hadar, This paper constitutes a full anatomical de- scription of hominid mandibles from Hadar, Ethiopia. The stratigraphic placement, phy- logenetic assessment, and taxonomic desig- nation for these specimens is provided by Jo- hanson and Taieb in an introductory paper to this volume. See Appendix I for a list of spec- imens described and a guide to description con- tents. The descriptive format and terminology em- ployed in these descriptions follow White (1977). Tooth roots and crowns in the speci- mens described here are assessed in companion papers (Johanson, White, and Coppens; Ward and Johanson, this volume). Descriptions for A.L. 288-11, the “Lucy” mandible, appear in Johanson et al. on pages 410-413 of this volume. All measurements are in millimeters. Appendix 1 is an index to these descriptions.’ DESCRIPTIONS A.L. 128-23 (Fig. zyxwvu 1) The specimen consis@ of a right mandible corpus with crowns of C-M,. Preservation: The ramus is broken imme- diately above its root. The gonial angle is miss- ing and only the anterosuperior portion of the masseteric fossa remains. Midline is preserved across a small portion of inferior transverse torus and through the basal contour, rising 12.0 onto the anterior corpus. Medial breakage is irregular, the broken surface rising through the root and crown of RI,. The base is preserved for only 15.0 to the right of the midline. Basal breakage appears to be fresh, “green bone” flaking. Much corpus surface is etched and weathered, especially the masseteric fossa and the area behind the mental foramen. The al- veolar margin suffers minor flaking, especially medial to MI, and the M3 crypt is exposed. Distortion is minimal; several thin, matrix- filled cracks occur below 12-P4/M1, but these expand corpus dimensions only by a maximum of 1.0. Two possible carnivore puncture marks lie 4.0 below the lateral alveolar margin at P3 and P4. Morphology: the corpus Lateral aspect. Alveolar and lateral occlu- sal margins diverge anteriorly. The C crown is not fully erupted, its enamel line about 3.7 below that of the P3 in lateral view. The C was tall, projecting high above the occlusal plane. Since the C tip is broken and the M3 was une- rupted (no interproximal facet on the M,), the Curve of Spee cannot be ascertained. It prob- ably would have been strong. The alveolar margin is sharp and straight lateral to M, and M2. It is broken but clearly dips strongly lat- eral to the C. A lateral prominence lies lateral to the me- dial Mz level, below and continuous with the ramus root. The anterior edge of the promi- nence is eroded and the course of the oblique line is obscured. The ramus root inserts on the corpus immediately above the lateral promi- nence. In true lateral aspect it arises to obscure distal M,. The leading edge of the ramus is 8.5 lateral to the alveolar margin at mid-M,. The extramolar sulcus opens anteroinferiorly, lat- eral to M1/M2. Its relative corpus height cannot be assessed, but the sulcus was probably high and shallow. ‘Appendix 1 and Tables 1-10 are located after the Literature Cited Received March 17, 1981; accepted December 10,1981. Section. 0002-9483/82/5704-0501$11.50 zyxwvuts 0 1982 ALAN R. LISS. INC.