 Reference Base  Skull evolution in living and fossil rhinoceroses: morpho... |
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Bales, G.S., 1994. Skull evolution in living and fossil rhinoceroses: morphometric analyses of within and between group variation. Journal of Morphology 220 (3): 322-323
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| Location: |
World |
| Subject: |
Taxonomy - Evolution |
| Species: |
All Rhino Species |
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Rhinoceroses comprise a long-lived and once diverse group with a relatively large fossil record and a few surviving taxa. Skull evolution was studied using living analogues as gauges of intraspecific variation. Analyses were done on 15 extinct and 4 extant genera using 19 measurements of adult crania (83 living, 103 fossil), and 11 measurements of adult mandibles (80 living, 84 fossil). Within-group variation was observed by principal components. Sources of variation within extant genera included geography, sex dimorphism, and taxonomic differentiation. Diceros (black rhino, n = 48) showed the greatest intraspecific variation and was the most homogeneous sample (monospecific, geographically circumscribed, no siginificant dimorphism). Variation within fossil genera was partitioned into subgroups based on morphological, geographical, and temporal criteria. Variation within subgeneric groups was often more consistent with living analogues. Canonical variates were used to observe morphological variation and relationships among groups defined by principal components analysis. Affinites were observed with respect to familial and subfamilial taxa, horn arrangements, hypothesized phylogenies, and temporal trajectories of small to large size. Affinities were less clear with respect to browsing versus grazing adaptations, and skull characters used in recent cladistic analyses. Rhinoceros skull evolution appears to have been a mosaic of shape changes accompanying significant size changes both within and between genera.
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