 Reference Base  A morphometric contribution to rhinoceros phylogeny. Can... |
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Bales, G.S., 2001. A morphometric contribution to rhinoceros phylogeny. Canonical variate studies of extant and fossil skulls (Rhinocerotoidea: Perissodactyla). Journal of Vertebrate Paleontology 21 (Suppl. To no. 3): 31A
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| Location: |
Asia |
| Subject: |
Taxonomy - Evolution |
| Species: |
All Rhino Species |
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The five species, four-genus view of living rhinos has been stable, but the relationships among genera have been variably interpreted. The problem includes a confounding of biogeography and horn number by Dicerorhinus. It is geographically Asian but has two horns. Rhinoceros, also Asian, is one-horned, while the African genera (Diceros, Ceratotherium) are two-horned. Among proposed hypotheses are these three: (1) horn number primary, geography secondary (Diceroorhinus belongs in an African group). (2) geography primary, horn number secondary (Dicerorhinus belongs in an Asian group). (3) geography and horns both primary (Dicerorhinus is basal). A recent molecular study supports the first hypothesis.
This study investigates shape relationships among extant and fossil genera in a canonical variates (CV) morphospace using skull measurements. Previous principal components (PC) analyses showed that the degrees of infrageneric, interspecific and intraspecific variation for crania and mandibles have been similar across time and taxa, giving a good estimate of within-group variation. CV morphospace ordinates the genera along axes of minimum separation, having accounted for within-groups variation.
PC studies also showed that the measurements detected shape differences to the geographic and interquarry level within species. If the 'core' rhino skull shape is Conservative (as it seems), then skull shape may contain some extractable phylogenetic information, since closely related taxa 'stick' close to each other morphologically (shared derived shape).
Preliminary CV's have shown a mixture of results for shape associations of Dicerorhinus. All the plots separate Rhinoceros from Ceratotherium and Diceros, but show Dicerorhinus as basal (similar to Aphelops) or similar to Diceros (in an isometric size-free approach). Mandile plots place Dicerorhinus closest to Diceros, but with a unique shape (not basal).
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