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Brief Communication: Molar development and crown areas in early Australopithecus
Author(s) -
Lacruz Rodrigo S.,
Ramirez Rozzi Fernando V.,
Wood Bernard A.,
Bromage Timothy G.
Publication year - 2012
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.22089
Subject(s) - biology , australopithecus , crown (dentistry) , homo sapiens , evolutionary biology , cusp (singularity) , lineage (genetic) , clade , dentition , phylogenetic tree , paleontology , orthodontics , geography , genetics , gene , geometry , archaeology , mathematics , medicine
Abstract Recent studies suggest that the hypodigms representing the two earliest Australopithecus ( Au. anamensis and Au. afarensis ) form an ancestor‐descendant lineage. Understanding the details of this possible transition is important comparative evidence for assessing the likelihood of other examples of ancestor‐descendant lineages within the hominin clade. To this end we have analyzed crown and cusp base areas of high resolution replicas of the mandibular molars of Au. anamensis (Allia Bay and Kanapoi sites) and those of Au. afarensis (Hadar, Laetoli, and Maka). We found no statistically significant differences in crown areas between these hypodigms although the mean of M 1 crowns was smaller in Au. anamensis , being the smallest of any Australopithecus species sampled to date. Intraspecies comparison of the areas of mesial cusps for each molar type using Wilcoxon signed rank test showed no differences for Au. anamensis . Significant differences were found between the protoconid and metaconid of Au. afarensis M 2 s and M 3 s. Furthermore, the area formed by the posterior cusps as a whole relative to the anterior cusps showed significant differences in Au. afarensis M 1 s and in Au. anamensis M 2 s but no differences were noted for M 3 s of either taxon. Developmental information derived from microstructural details in enamel shows that M 1 crown formation in Au. anamensis is similar to Pan and shorter than in H. sapiens . Taken together, these data suggests that the overall trend in the Au. anamensis ‐ Au. afarensis transition may have involved a moderate increase in M 1 crown areas with relative expansion of distal cusps. Am J Phys Anthropol , 2012. © 2012 Wiley Periodicals, Inc.