This chimeric remodeling describes an extinct species that displayed major characteristics of both the hippopotamus and the tortoise, featuring minor characteristics of both a rhinoceros and a walrus. Its life history explains the evolutionary pressures that led to the decline of Choeropelonoidensis kirkimus . All modern-day hippopotamuses and tortoises are herbivorous, due to the last common predatory carnivorous ancestor (the pygmy hippopototortoise) failing in its niche as a semiaquatic oophagous and piscivorous species. Its weak legs and bulky shelled body did not allow for efficient predation, and its large crocodilian predators were better at protecting their eggs than the hippopototortoise was at eating them. This led to the divergence into 2 herbivorous populations, one in the presence of its predator, maintaining its shell for protection, and one in an herbaceous pond without predators, allowing for the loss of shell, resulting in modern hippopotamuses and tortoises.
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