Two species of one-horned Asian rhinos differ significantly in appearance and behavior, a new study has found, challenging traditional classification and prompting a rethink of their taxonomic status. The study, led by zoologist Francesco Nardelli and paleontologist Kurt Heißig, focused on how millions of years of evolutionary pressure drove different adaptations in Indian rhinoceros (Rhinoceros unicornis) and Sunda rhinoceros (Rhinocerossondaicus).
The critically endangered Sunda rhinoceros has an elongated skull, a wider back, a shorter nose, and teeth suitable for chewing leaves. In contrast, the Indian rhinoceros has a stronger skull and taller teeth, which are suitable for eating grass.
"Adaptations of large terrestrial mammals to different environments are related to the diversity of food types they can eat, which is reflected in changes in their teeth and skull morphology. In the case of rhinos, these adaptations are reflected in their tooth structure and head posture," the researchers wrote in their paper published in the journal ZooKeys.
The Sunda rhinoceros is currently only found in the Ujung Kulon Peninsula of Java. It is a herbivore with a unique polygonal skin. Unlike other living rhinos, female rhinos do not have horns. In contrast, the Indian rhinoceros is a herbivore of the riparian grasslands of northern India and Nepal.
The Indian rhinoceros has deeply wrinkled skin and is heavier, making it much larger than its Sunda cousin. The Indian rhinoceros is second only to elephants and white rhinos in size, with males weighing over 2,000 kilograms and females weighing 1,600 kilograms.
Fossil evidence confirms that these differences evolved independently over long periods of time. The authors believe that they represent fundamental anatomical and ecological distinctions that reflect profound evolutionary adaptations. There are also significant differences in the behavior of the two species, with the Sunda rhinoceros being a solitary wanderer and the Indian rhinoceros forming temporary aggregations.
"Both species possess unique adaptations for survival, highlighting the importance of understanding their systemic nature for effective conservation," the researchers wrote in their paper.
Based on these findings, scientists proposed a more precise scientific name for the Sunda rhinoceros: Eurhinocerossondaicus. They assert: "Recognizing Eurhinocerossondaicus as a distinct genus more accurately reflects its evolutionary history and ecological specialization. This precise classification not only enhances our understanding of rhino evolution, but also provides a clearer framework for conservation planning, helping to develop strategies to protect these critically endangered animals."
Compiled from /ScitechDaily