Examined material

This is the list of specimens examined for each ichnotaxon

The Taxonomic and Phylogenetic Affinities of <i>Bunopithecus sericus</i>, a Fossil Hylobatid from the Pleistocene of China

<div><p>Fossil hylobatids are rare, but are known from late Miocene and Pleistocene sites throughout East Asia. The best-known fossil hylobatid from the Pleistocene of China is a left mandibular fragment with M_2-3 (AMNH 18534), recovered from a pit deposit near the village of Yanjinggou in Wanzhou District, Chongqing Province. Matthew and Granger described this specimen in 1923 as a new genus and species, <i>Bunopithecus sericus</i>. Establishing the age of <i>Bunopithecus</i> has proved difficult because the Yanjinggou collection represents a mixed fauna of different ages, but it likely comes from early or middle Pleistocene deposits. Although the <i>Bunopithecus</i> specimen has featured prominently in discussions of hylobatid evolution and nomenclature, its systematic status has never been satisfactorily resolved. The present study reexamines the taxonomic and phylogenetic relationships of <i>Bunopithecus</i> by carrying out a detailed comparative morphometric study of its lower molars in relation to a large sample of modern hylobatids. Our results show that differences in M₂ and M₃ discriminate extant hylobatids fairly well, at least at the generic level, and that AMNH 18534 is not attributable to <i>Hylobates</i>, <i>Nomascus</i> or <i>Symphalangus</i>. Support for a close relationship between <i>Bunopithecus</i> and <i>Hoolock</i> is more equivocal. In most multivariate analyses, <i>Bunopithecus</i> presents a unique morphological pattern that falls outside the range of variation of any hylobatid taxon, although its distance from the cluster represented by extant hoolocks is relatively small. Our results support the generic distinction of <i>Bunopithecus</i>, which most likely represents an extinct crown hylobatid, and one that may possibly represent the sister taxon to <i>Hoolock</i>.</p></div

Fossil and recent comparative sample of hylobatid lower molars used in this study.

<p>*This sample includes representatives of the following species: <i>H</i>. <i>agilis</i> (M₂ = 32, M₃ = 20), <i>H</i>. <i>albibarbis</i> (M₂ = 9, M₃ = 6), <i>H</i>. <i>klossi</i> (M₂ = 10, M₃ = 8), <i>H</i>. <i>lar</i> (M₂ = 12, M₃ = 11), <i>H</i>. <i>moloch</i> (M₂ = 9, M₃ = 8), <i>H</i>. <i>muelleri</i> (M₂ = 22, M₃ = 16), <i>H</i>. <i>pileatus</i> (M₂ = 4, M₃ = 4), and <i>Hylobates</i> sp. (M₂ = 2, M₃ = 0).</p><p>Fossil and recent comparative sample of hylobatid lower molars used in this study.</p

Plot of the first two discriminant functions (DF1 and DF2) of the M₂ analysis using linear measurements, cusp angles and absolute areas.

<p>Eigenvalues: 4.19 (DF1) and 0.52 (DF2); variance: 84.44% (DF1) and 10.41% (DF2).</p

Hylobatid left lower molar showing dental variables taken.

<p>A) Linear dimensions: 1) mesiodistal length, 2) buccolingual width at mesial cusps, and 3) buccolingual width at distal cusps. B) Angles: 1) position of mesiobuccal cusp, 2) position of mesiolingual cusp, and 3) position of hypoconulid. C) Absolute cusp areas: 1) protoconid, 2) metaconid, 3) entoconid, 4) hypoconid, and 5) hypoconulid.</p

Plot of the first two discriminant functions (DF1 and DF2) of the M₃ analysis using linear measurements, cusp angles and absolute areas.

<p>Eigenvalues: 40.22 (DF1) and 0.31 (DF2); variance: 87.07% (DF1) and 6.80% (DF2).</p

Map of East and Southeast Asia showing the historical and present distribution of gibbons (<i>Hoolock</i>, <i>Hylobates</i> and <i>Nomascus</i>).

<p>The black star indicates the location of the village of Yanjinggou (Wanzhou District, Chongqing Province, China), where <i>Bunopithecus sericus</i> was found. Adapted from Gu [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131206#pone.0131206.ref007" target="_blank">7</a>], Gao et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131206#pone.0131206.ref030" target="_blank">30</a>] and Geissmann [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131206#pone.0131206.ref080" target="_blank">80</a>].</p

Plot of the first two discriminant functions (DF1 and DF2) in the analysis of size variables, M₂ and M₃ combined.

<p>Eigenvalues: 4.79 (DF1) and 0.73 (DF2); variance: 74.32% (DF1) and 11.41% (DF2).</p