ISSN:
1573-7055
Keywords:
Cartesian
;
transformation
;
splines
;
rhinoceros
;
skull
;
evolution
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Cartesian transformation, applied as a landmark morphometric method, is used to investigate some of the evolutionary shape changes leading to the skulls of the modern rhinoceroses. The early Oligocene genusSubhyracodon serves as the primitive shape from which the extant genera (Dicerorhinus, Rhinocerso, Diceros, andCeratotherium) have been transformed. Coordinate data for 21 landmarks, defined in lateral view, are analyzed by the computer program Thinplate Splines. Each of the four transformations are interpreted separately as shape change fromSubhyracodon. Computed results forRhinoceros are also compared with previous results obtained by visual interpretation (the classic method). Among the extant genera,Ceratotherium andRhinoceros have the most derived shapes and are opposites with respect to orientation of the occiput and relative size of the mandible angle. The significance of these foci of change is discussed in terms of the functions of the masseter and posterior temporalis muscles. In head positions associated with feeding on short vs. tall grasses, the two skull shapes are consistent with a role for these muscles in support of a large mandible against gravity. This common factor may help to explain both shapes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01458183
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