 Reference Base  Population structure and implications for social behavior... |
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Mihlbachler, M.C., 1999. Population structure and implications for social behavior in Miocene Florida rhinoceroses. Journal of Vertebrate Paleontology 19, Supplement to no. 3: 64A
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| Location: |
America |
| Subject: |
Taxonomy - Evolution |
| Species: |
Fossil |
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The Florida Miocene fossil localities, Love Bone Bed (late Clarendonian) and Mixon's Bone Bed (early Hemphilian) contain large attritional samples of paleopopulations of two rhino genera, Teleoceras and Aphelops. Each Teleoceras population contains over 50 individuals. Measures of crown heights and wear stages of the deciduous and adult cheek teeth reveal discrete age categories indicating seasonality in births, and that deaths tend to be seasonal or that Teleoceras was migratory, only inhabiting the two localities during a certain portion of the year. Juveniles are well represented and the sample contains unerupted deciduous premolars with incompletely formed enamel crowns, suggesting that birthing took place at these localities. There is a sharp increase in mortality during the sixth wear stage, or 6th year, that corresponds to the ruption of the lower tusks. Based on the sexually dimorphic tusks, males outnumber females 3/1 at Love and 4/1 at Mixon's. Nearly two thirds of the males are young adults or adolescents. Sexual maturity, thus, occurs at six years of age and intense inter-male competition and territoriality is probably the cause of the increased mortaility. Because both Love and Mixon's were shallow water environments, the population structure of Teleoceras indicates that shallow bodies of water were the centers of social behaviour for this genus, not unlike the living Indian rhino, Rhinoceros unicornis.
The Aphelops samples are smaller but discrete wear categories seem to be absent. Sex ratios are nearly 1/1. Juveniles and young adults are rare while old adults are common, suggesting that Aphelops was less gregarious with reduced inter-male competition. Shallow water environments do not seem to be important centers of social behavior in this genus.
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