A study finds an early mammaliaform displaying tooth anatomy that gives insight into the development of structures such as complex molars and multiple roots. One evolutionary milestone in the development of mammalian teeth can be found in haramiyidan mammaliaforms, which developed double rows of cusps on molar-like teeth adapted for omnivorous feeding. However, the origin of the multicusped pattern is unclear. Grzegorz Niedzwiedzki and colleagues used CT scanning to analyze the dentary and tooth structure of a recently described mammaliform species, Kalaallitkigun jenkinsi, discovered on the eastern coast of Greenland and dating from the late Triassic. The species exhibits the earliest known mandibular fossil with two rows of cusps on molars and double-rooted teeth. The dentary anatomy and tooth structure place K. jenkinsi in an intermediate position between haramiyidans and morganucodontids, although with teeth nearly twice the size of morganucodontids and similar in size to haramiyidans. The species offers insight into mammalian tooth evolution, particularly the development of double-rooted teeth. Biomechancial analysis found that double-rooted teeth are better able to withstand mechanical stresses, including those of upper and lower tooth contact during biting, compared with single-rooted teeth. According to the authors, the results suggest that molar-like teeth with crowns may have developed together with biomechanically optimized dual roots.
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Article #20-12437: "The earliest-known mammaliaform fossil from Greenland sheds light on origin of mammals," by Tomasz Sulej et al.
MEDIA CONTACT: Grzegorz Niedzwiedzki, Uppsala University, SWEDEN; e-mail: < grzegorz.niedzwiedzki@ebc.uu.se >
Proceedings of the National Academy of Sciences