2/24/2024 0 Comments Rhinoceros unicornis comiendoObservational studies of the African rhinoceroses have revealed some interesting behaviors, including aggression ( Leuthold, 1977), a complex social structure ( Owen-Smith, 1971), ear movements signaling intimidation ( Leuthold, 1977), acute olfactory capabilities ( Cave, 1966), and differences in the duration of a sleep bout between males and females ( Santymire et al., 2012). The black and white rhinoceros are iconic species of the African continent with the white rhinoceros being the second largest terrestrial mammal after the African elephant. After much debate regarding the phylogenetic relationships of these living species, it has been established that the Asian and African lineages diverged approximately 26 million years ago ( Tougard, 2001). The Rhinoceritidae includes five extant species: the black ( Diceros bicornis) and white ( Ceratotherium simum) African rhinoceroses, the Indian rhinoceros ( Rhinoceros unicornis), the Javan rhinoceros ( Rhinoceros sondaicus) and the Sumatran rhinoceros ( Dicerorhinus sumatrensis) ( Wilson and Reeder, 1993). The order Perissodactyla is comprised of the Rhinoceritidae, Tapiridae, and Equidae families. The fossil record of Perissodactyla places its earliest members in the upper Palaeocene ( Radinsky, 1969), yet molecular studies suggest that the Perissodactyla diverged from Cetartiodactyla 97.5 – 83.4 million years ago ( Eizirik et al., 2001 Price and Bininda-Emonds, 2009) or Carnivora approximately 80 million years ago ( Springer et al., 2003). We conclude that the brains of the black and white rhinoceros exhibit a typically mammalian organization at a superficial level, but histological studies may reveal specializations of interest in relation to rhinoceros behavior. In addition, the volumetric analyses indicate that the size of the various regions of the rhinoceros brain measured, as well as the extent of gyrification, are what would be predicted for a mammal with their brain mass when compared allometrically to previously published data. The rhinoceros brains display no obvious neuroanatomical specializations in comparison to other mammals previously studied. The morphology of both black and white rhinoceros brains is very similar to each other, although certain minor differences, seemingly related to diet, were noted, and both brains evince the general anatomy of the mammalian brain. For both species, we use magnetic resonance images (MRI) to develop a description of the internal anatomy of the rhinoceros brain and to calculate the volume of the amygdala, cerebellum, corpus callosum, hippocampus, and ventricular system as well as to determine the gyrencephalic index. Here, we provide descriptions of the surface of the brain of each rhinoceros. The black rhinoceros is typically solitary whereas the white rhinoceros is social, and both are members of the Perissodactyl order. The morphology and volumetrics of the understudied brains of two iconic large terrestrial African mammals: the black ( Diceros bicornis) and white ( Ceratotherium simum) rhinoceroses are described. 2Department of Radiology, Wits Donald Gordon Medical Centre, University of the Witwatersrand, Johannesburg, South Africa.1School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.Adhil Bhagwandin 1 Mark Haagensen 2 Paul R.
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