Article

Hominid mandibular corpus shape variation and its utility for recognizing species diversity within fossil Homo.

Natural Sciences & Mathematics, The Richard Stockton College of New Jersey, Pomona, NJ 08240-0195, USA.
Journal of Anatomy (Impact Factor: 2.36). 01/2009; 213(6):670-85. DOI: 10.1111/j.1469-7580.2008.00989.x
Source: PubMed

ABSTRACT Mandibular corpora are well represented in the hominin fossil record, yet few studies have rigorously assessed the utility of mandibular corpus morphology for species recognition, particularly with respect to the linear dimensions that are most commonly available. In this study, we explored the extent to which commonly preserved mandibular corpus morphology can be used to: (i) discriminate among extant hominid taxa and (ii) support species designations among fossil specimens assigned to the genus Homo. In the first part of the study, discriminant analysis was used to test for significant differences in mandibular corpus shape at different taxonomic levels (genus, species and subspecies) among extant hominid taxa (i.e. Homo, Pan, Gorilla, Pongo). In the second part of the study, we examined shape variation among fossil mandibles assigned to Homo (including H. habilis sensu stricto, H. rudolfensis, early African H. erectus/H. ergaster, late African H. erectus, Asian H. erectus, H. heidelbergensis, H. neanderthalensis and H. sapiens). A novel randomization procedure designed for small samples (and using group 'distinctness values') was used to determine whether shape variation among the fossils is consistent with conventional taxonomy (or alternatively, whether a priori taxonomic groupings are completely random with respect to mandibular morphology). The randomization of 'distinctness values' was also used on the extant samples to assess the ability of the test to recognize known taxa. The discriminant analysis results demonstrated that, even for a relatively modest set of traditional mandibular corpus measurements, we can detect significant differences among extant hominids at the genus and species levels, and, in some cases, also at the subspecies level. Although the randomization of 'distinctness values' test is more conservative than discriminant analysis (based on comparisons with extant specimens), we were able to detect at least four distinct groups among the fossil specimens (i.e. H. sapiens, H. heidelbergensis, Asian H. erectus and a combined 'African Homo' group consisting of H. habilis sensu stricto, H. rudolfensis, early African H. erectus/H. ergaster and late African H. erectus). These four groups appear to be distinct at a level similar to, or greater than, that of modern hominid species. In addition, the mandibular corpora of H. neanderthalensis could be distinguished from those of 'African Homo', although not from those of H. sapiens, H. heidelbergensis, or the Asian H. erectus group. The results suggest that the features most commonly preserved on the hominin mandibular corpus have some taxonomic utility, although they are unlikely to be useful in generating a reliable alpha taxonomy for early African members of the genus Homo.

0 Bookmarks
 · 
83 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Investigating ontogenetic variation and allometry in the mandible can provide valuable insight and aid in addressing questions related to the ontogeny of the skull. Here, patterns of ontogenetic shape change and allometric trajectories were examined in the mandible of 187 sub-adult and adult humans, bonobos, and chimpanzees. Procrustes-based geometric morphometrics was employed to quantify and analyze mandibular form. Thirty three-dimensional landmarks were used to capture the overall morphology of the mandible, and the landmarks were analyzed as a whole and subdivided into separate anterior and posterior units. Principal component analyses in Procrustes shape-space and form-space, and multivariate regressions were used to examine patterns of ontogenetic and allometric shape change. Results suggest that humans are distinct from Pan both in their mandibular morphology, particularly in the anterior-alveolar region, and direction of allometric trajectory. Chimpanzees and bonobos have parallel ontogenetic trajectories, but also show differences in mandibular shape. Species-specific features and adult mandibular shape are established before or by the eruption of the deciduous dentition. This suggests that developmental processes prior to deciduous teeth eruption have a stronger effect establishing taxa-specific phenotypes than later postnatal effects. This additionally implies that divergent trajectories between Pan and Homo do not contribute much to the adult mandibular shape after deciduous teeth eruption. Separate analyses of the anterior-alveolar region and ascending ramus show that these regions are semi-independent in their developmental pattern of shape change and allometry. This implies that allometric variation and ontogenetic shape change in the hominoid mandible is decoupled. Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 12/2013; · 1.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Since the announcement of the species Australopithecus sediba, questions have been raised over whether the Malapa fossils represent a valid taxon or whether inadequate allowance was made for intraspecific variation, in particular with reference to the temporally and geographically proximate species Au. africanus. The morphology of mandibular remains of Au. sediba, including newly recovered material discussed here, shows that it is not merely a late-surviving morph of Au. africanus. Rather-as is seen elsewhere in the cranium, dentition, and postcranial skeleton-these mandibular remains share similarities with other australopiths but can be differentiated from the hypodigm of Au. africanus in both size and shape as well as in their ontogenetic growth trajectory.
    Science 04/2013; 340(6129):1232997. · 31.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Summary form only given. Coherent transient optical memories and signal processors (CTOMs and CTOPs) take advantage of an inhomogeneously broadened absorber (IBA) to store and process temporal waveforms with data bandwidths exceeding 10 GHz and with extermely high storage and processing densities. In this paper, we propose and demonstrate techniques to compensate for the deleterious effects of dephasing in CTOMs and CTOPs. Compensation is achieved by applying an intensity ramp, which matches the inverse of the decay while maintaining roughly the same pulse area in the pattern stream to be recorded. We used the 783-nm transition of Tm/sup 3+/:YAG (0.1 at.%) at cryogenic temperatures to demonstrate the compensation techniques.
    Lasers and Electro-Optics, 1996. CLEO '96., Summaries of papers presented at the Conference on; 07/1996

Full-text (2 Sources)

View
22 Downloads
Available from
May 28, 2014