Ancient Mammaliaform Discovered In Greenland

A new genus and species of mammaliaform was described recently in Greenland from a single partial jaw specimen, and though there is a limited amount of information to work with regarding this find, the implications are quite significant!

This animal, which paleontologists named “Kalaallitkigun jenkinsi“, hails from around 215 million years ago, in what would have been the Late Triassic. Kalaallitkigun expands our current knowledge of the evolution of mammalian dental evolution and dietary evolution through it’s interesting dental structure. Kalaallitkigun is noted as displaying the earliest example of “double molariform” teeth known to science so far, meaning teeth with two roots. Our own molars would be a good example of double molariform teeth. This feature places Kalaallitkigun as a sort of transitionary animal, moving from insectivorous shrew-like creatures called morganucodontans to mammals as we know them today, swapping out strict insectivory for a more varied omnivorous diet.

An artistic rendition of the profile of Kalaallitkigun. Artist Credit: Marta Szubert

Kalaallitkigun was found at a site called the Liasryggen Site in Eastern Greenland. 215 million years ago, Greenland would have truly lived up to its name. Dense undergrowth, clear rivers and steaming forests would have sprawled across the landscape, serving as a stomping ground for early dinosaurs and early mammals alike. Previously, theropod footprints have been found at this site, and in the Triassic, these small mammaliaforms would have been scurrying away for dear life from early dinosaurs, which had spread to every corner of the Earth recently. We, as modern mammals, owe our existence to the resourcefulness and opportunism of early mammal ancestors like Kalaallitkigun.

Digital rendering of the holotype left dentary of Kalaallitkigun jenkinsi from the mid-to-late Norian of the Fleming Fjord Formation, East Greenland: (A) the life position of the preserved part of the dentary; (B-D) the dentary in labial (B), lingual (C), and occlusal (D) views; (E-G) the only preserved premolariform in labial (E), lingual (F), and occlusal (G) views; (H-J) the only preserved molariform (m2) in lingual (H), labial (I), and occlusal (J) views. M1-3 mark the position of molariforms (2 is double rooted); pm1-4 mark the position of the premolariforms (1 is single, 2 is double rooted); c marks the position of the canine; (A, G, and B) 1-b4 indicate cusp assignments in the molariform. Abbreviations: ang. reg. – angular region, cre. – crest, premolar. – premolariform, molar. – molariform, cor. pr. – coronoid process, cor. fos. – coronoid fossa, M. tempo. fos. – M. temporalis fossa, V3 no. – V3 notch for the mandibular nerve entering the mandibular canal, Mec. sul. – Meckel’s sulcus, mand. ca. for. – mandibular canal foramen, mas. fos. – masseteric fossa, lat. rid. – lateral ridge, postd. tr. – postdentary trough, med. rid. – medial ridge, and sym. – symphysis. Image credit: Sulej et al.

 

  • Tomasz Sulej et al. The earliest-known mammaliaform fossil from Greenland sheds light on origin of mammals. PNAS, published online October 12, 2020; doi: 10.1073/pnas.2012437117

 

 

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