MASSACHUSETTS: Researchers recently studied the broken pieces of suspected teeth or tusks from extremely early mammals that had been kept at multiple institutions in Africa and the US.
M. R. Whitney and colleagues brought the pieces of dicynodonts into the lab and examined their composition and formation under the microscope. They aspired to figure out whether the pieces were tusks or they were simply teeth.
So they came up with three main characteristics of tusks, i.e., a tusk had to be ever-growing, protrude from the mouth, and made of dentine (inner layer of the tooth) and couldn’t contain enamel (outermost layer of the tooth).
Whitney and her team fragmented the broken pieces even further for the study. The research showed that certain factors needed to be present for tusks to evolve, including flexible tooth ligaments and reduced rates of teeth-replacing themselves after coming out. The study also showed that tusks evolve on different timelines for different creatures.
Hence, the proposed features of an ever-growing dentition,i.e., reduced tooth replacement and a permanent soft-tissue attachment, are specified in the dentitions of crown-group mammals, which helps explain why tusks have been restricted to this group of extant vertebrates.