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| the Prince Creek Formation, DMNH 21183 comes from the juvenile dromaeosaurid on the branch close to the adult
in Chiarenza, Fiorillo, Tykoski, et al., 2020.
Illustration: Andrey Atuchin
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Abstract
Compared to the osteological record of herbivorous dinosaurs from the Late Cretaceous Prince Creek Formation of northern Alaska, there are relatively fewer remains of theropods. The theropod record from this unit is mostly comprised of isolated teeth, and the only non-dental remains known can be attributed to the troodontid cf. Troodon and the tyrannosaurid Nanuqsaurus. Thus far, the presence of members of Dromaeosauridae has been limited to isolated teeth. Here we describe a symphyseal portion of a small dentary with two ziphodont teeth. Based on tooth shape, denticle morphology, and the position of the Meckelian groove, we attribute this partial dentary to a saurornitholestine dromaeosaurid. The fibrous bone surface, small size, and higher number of mesial denticles compared to distal ones point to a juvenile growth stage for this individual. Multivariate comparison of theropod teeth morphospace by means of principal component analysis reveals an overlap between this dentary and Saurornitholestinae dromaeosaurid morphospace, a result supported by phylogenetic analyses. This is the first confirmed non-dental fossil specimen from a member of Dromaeosauridae in the Arctic, expanding on the role of Beringia as a dispersal route for this clade between Asia and North America. Furthermore, the juvenile nature of this individual adds to a growing body of data that suggests Cretaceous Arctic dinosaurs of Alaska did not undergo long-distance migration, but rather they were year-round residents of these paleopolar latitudes.
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| Fig 3. DMNH 21183. Anterior portion of a dromaeosaurid dentary in lateral (A), medial (B), dorsal view (C) views and close up of the interdental plates and 3rd tooth in medial view (D). Curved arrows represent features hidden on that view.
Abbreviations: a2, 2nd alveolus; a3, 3rd alveolus; rdt2, 2nd dentary tooth; rdt3, 3rd dentary tooth; rdt4, 4th dentary tooth; ave, antero-ventral process; idp, interdental plate; lr, lateral ridge; mg, Meckelian groove; mf, Meckelian foramina. Scale bar: 2 mm.
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Dinosauria
Theropoda
Dromaeosauridae
Eudromaeosauria
Saurornitholestinae indet.
Referred specimen: DMNH 21183. The anterior portion of a right dentary, preserving two teeth and four alveoli (Fig 3).
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| Fig 10. Life reconstruction of the Alaskan saurornitholestine in its environment. Artistic restoration by scientific illustrator Andrey Atuchin depicts a riparian setting in the Prince Creek Formation, matching the geological evidence described in this paper. DMNH 21183 comes from the juvenile dromaeosaurid on the branch close to the adult, while a subadult (foreground) stalks an individual of Unnuakomys hutchisoni, a methatherian known from this locality. Individuals of the sympatric ceratopsid Pachyrhinosaurus perotorum rest in the background. |
Alfio Alessandro Chiarenza, Anthony R. Fiorillo, Ronald S. Tykoski, Paul J. McCarthy, Peter P. Flaig and Dori L. Contreras. 2020. The First Juvenile Dromaeosaurid (Dinosauria: Theropoda) from Arctic Alaska. PLoS ONE. 15(7): e0235078. DOI: 10.1371/journal.pone.0235078
