Biology subjects

Kunimatsu, Y.

Publications and source records attributed to Kunimatsu, Y..

3 recordsLinked to original sources

bioRxiv2024

Anatomy of the mandibular symphysis of extant cercopithecids: taxonomy and variation

The symphyseal anatomy of extant and fossil cercopithecids has not yet been demonstrated as a useful tool for taxonomic discrimination, and the source of variation in cercopithecid symphysis has not been addressed on a broad taxonomic scale. Here, we used linear and angular dimensions to quantify symphysis shape. Using univariate, multivariate data and allometric regressions (partial least squares and phylogenetic generalized least square regressions), we addressed the hypothesis that extant cercopithecids can be distinguished by symphysis shape. Significant differences in univariate and multivariate data and allometric regressions permitted to distinguish cercopithecids at the subfamilial, tribal, and genus levels. We showed that multivariate data followed the distribution expected under Brownian Motion and significantly discriminates taxa at different taxonomic levels. Colobine symphysis are characterized by developed inferior transverse tori, short planum alveolare, and short symphysis, whereas cercopithecine symphysis are characterized by developed superior transverse tori, long planum alveolare, and long symphysis. Exceptions to this pattern exist within each subfamily, and this study underlines the particular anatomy of Colobus and Presbytis among the colobines, Allenopithecus among the Cercopithecini, and Theropithecus and Lophocebus among the Papionini. We also demonstrate that the relative development of the transverse tori, the relative length of the planum alveolare and symphyseal inclination are dimorphic traits. Specifically, we show that the symphysis of Procolobus verus, Nasalis larvatus, and Papio anubis is strongly dimorphic.

zoology↗

bioRxiv2024

Anatomy of the mandibular corpus of extant cercopithecids : taxonomy and variation

This study aims to discriminate cercopithecid taxa of higher taxonomic levels (subfamily, tribe, subtribe, and genus) on the basis of corpus shape in transverse cross-section at the M1-M2 junction and to assess its variation using 2D geometric morphometrics. Specifically, we evaluated the effect of allometry and sexual dimorphism on differences in corpus shape at interspecific and intraspecific levels, respectively. We also investigated whether corpus variation among cercopithecids was following Brownian motion using Pagels {lambda}. Taxonomic discrimination and sexual dimorphism were established using Analysis of Variance on Principal Component scores. Allometry was studied using phylogenetic least-squares regressions and partial least-squares regressions. We demonstrated that, using corpus shape, extant cercopithecids can be significantly discriminated at the subfamilial, tribal, and subtribal levels. In addition, the main axis of variation of the Principal Component Analysis follows a distribution expected under Brownian motion, validating the presence of a phylogenetic signal in corpus shape. Colobines exhibit a robust corpus (superoinferiorly short and transversely broad) with large lateral prominences while cercopithecines have a gracile corpus (superoinferiorly long and transversely thin in its distal portion) with marked corpus fossae in African papionins. Exception to the typical subfamilial or tribal shape pattern exist, with the best examples being Trachypithecus, Presbytis and Pygathrix within colobines, Allenopithecus within Cercopithecini, and Macaca, Theropithecus and Cercocebus within Papionini. Sexual dimorphism is a confounding factor in shape discrimination, as there are significant differences between sexes, notably in Papio anubis, Nasalis larvatus and Procolobus verus . Intriguingly, sexual dimorphism in corpus shape does not seem to follow the dimorphism deduced in canine and molar crown dimensions. This discrepancy is illustrated by the low degree of dimorphism in corpus shape in Piliocolobus badius, despite dimorphic canine and molar dimensions. Overall, our findings concerning corpus shape variation in cercopithecids will greatly benefit to paleontological studies that seek to identify taxa in the fossil record, and to neontological studies aiming to explore the ecomorphological value of the cercopithecid mandible.

zoology↗

bioRxiv2024

Description of new mandibular remains of Microcolobus from Nakali (ca. 10 Ma, Kenya): implications on the evolution of Miocene colobines.

We have described mandibular specimens of fossil colobines from the late Miocene site of Nakali (Kenya). Using qualitative and quantitative dental and mandibular traits, we compared them to an extensive sample of extant colobines and Miocene fossil colobines. We tested the hypothesis that i) only one species was present in this newly described fossil sample, ii) this species is phenetically distinct from fossil colobines from Ngerngerwa and Ngorora, iii) this species is phenetically distinct from hitherto documented fossil Miocene colobines, and iv) this species is phenetically more different from extant African colobines than from Asian colobines. Bootstrap analyses demonstrated that the Nakali specimens belong to a single fossil species. Dental and symphyseal morphometric ratios and a morphometric geometric analysis of the corpus cross-section showed that the Nakali colobines belong to Microcolobus tugenensis. Bootstrap analyses failed to unambiguously confirm the distinct taxonomic status of isolated dental specimens from Ngerngerwa and Ngorora, and suggest that they may represent, along with the Nakali sample, a single species. A linear discriminant analysis established on dental linear dimensions of four Nakali specimens classified them within the African colobine tribe (Colobini). Microcolobus have a P4 occlusal morphology, a breadth differential of the symphyseal transverse tori, and an inclination of the symphysis similar to extant African colobines. However, the corpus shape of Microcolobus is closer to that of primitive cercopithecoids, in addition to the lack of the diagnostic mesiodistal elongation of the lower canine of extant African colobines, suggesting that Microcolobus is likely a stem Colobinae.

paleontology↗