[Paleontology • 2015]
Ugrunaaluk kuukpikensis • A New Arctic Hadrosaurid from the Prince Creek Formation (lower Maastrichtian) of northern Alaska
Ugrunaaluk kuukpikensis
Mori, Druckenmiller & Erickson, 2015
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The Liscomb bonebed in the Price Creek Formation of northern Alaska has
produced thousands of individual bones of a saurolophine hadrosaurid
similar to Edmontosaurus; however, the specific identity of this
taxon has been unclear, in part because the vast majority of the remains
represent immature individuals. In this study, we address the taxonomic
status of the Alaskan material through a comparative and quantitative
morphological analysis of juvenile as well several near adult-sized
specimens with particular reference to the two known species of Edmontosaurus,
as well as a cladistic analysis using two different matrices for
Hadrosauroidea. In the comparative morphological analysis, we introduce a
quantitative method using bivariate plots to address ontogenetic
variation. Our comparative anatomical analysis reveals that the Alaskan
saurolophine possesses a unique suite of characters that distinguishes
it from Edmontosaurus, including a premaxillary circumnarial
ridge that projects posterolaterally without a premaxillary vestibular
promontory, a shallow groove lateral to the posterodorsal premaxillary
foramen, a relatively narrow jugal process of the postorbital lacking a
postorbital pocket, a relatively tall maxilla, a relatively gracile
jugal, a more strongly angled posterior margin of the anterior process
of the jugal, wide lateral exposure of the quadratojugal, and a short
symphyseal process of the dentary. The cladistic analyses consistently
recover the Alaskan saurolophine as the sister taxon to Edmontosaurus annectens + Edmontosaurus regalis.
This phylogenetic assessment is robust even when accounting for
ontogenetically variable characters. Based on these results, we erect a
new taxon, Ugrunaaluk kuukpikensis gen. et sp. nov.
that contributes to growing evidence for a distinct, early
Maastrichtian Arctic dinosaur community that existed at the northernmost
extent of Laramidia during the Late Cretaceous.
Key words: Dinosauria, Hadrosauridae, Saurolophinae, Edmontosaurini, Ugrunaaluk, Edmontosaurus, ontogeny, Cretaceous, Prince Creek Formation, Arctic.
Ugrunaaluk kuukpikensis illustrates a scene from ancient Alaska during the Cretaceous Period.
illustration: James Havens
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Fig. 4. Cranial reconstruction of Ugrunaaluk kuukpikensis gen. et sp. nov. from the early Maastrichtian Prince Creek Formation in left lateral view. |
Systematic Paleontology
Ornithischia Seeley, 1887
Ornithopoda Marsh, 1881
Hadrosauridae Cope, 1869
Saurolophinae Brown, 1914 sensu Prieto-Márquez, 2010a
Edmontosaurini Brett-Surman, 1989
Genus Ugrunaaluk nov.
urn:lsid:zoobank.org:act:8B8256BA-F280-4460-B0F0-31762267586E
Etymology: Transliterated from the Alaskan Iñupiaq noun ugruŋnaq, referring to a grazing animal with a long set of grinding teeth, and the adjective -aluk, old. Literally, “ancient grazer”.
Intended pronunciation: “oo-GREW-nah-luk”. The name honors the Alaskan
Native Iñupiaq culture from the area where the type material was
discovered.
Type species: Ugrunaaluk kuukpikensis sp. nov., monotypic
urn:lsid:zoobank.org:act:1CAF186F-11A2-4A9E-A8F9-C3789B97459F
Figs. 4–10.
Etymology: The specific name is derived from the Iñupiaq word kuukpik,
which refers to the Colville River, Alaska, USA along which the
type material was found.
Type locality: Liscomb bonebed, along the Colville River,
northern Alaska, USA. The exact location is on file with the Bureau of
Land Management Arctic Field Office.
Type horizon: Upper portion of the Prince Creek Formation, lower Maastrichtian (Upper Cretaceous).
Fig. 2. Temporal distribution of Edmontosaurus species and the Prince Creek Formation taxon in the Late Cretaceous. |
Conclusions
In this study, we; (i) identify and name a new taxon of saurolophine hadrosaurid, Ugrunaaluk kuukpikensis gen. et sp. nov.
from the Prince Creek Formation of Alaska; (ii) demonstrate that
skeletally immature specimens can be reliably used in addressing
taxonomic problems within
Hadrosauridae based on a detailed understanding of the growth patterns of closely related taxa; and (iii) show that Ugrunaaluk kuukpikensis gen. et sp. nov. does not represent a juvenile form of either recognized species of Edmontosaurus. Further morphological description of the new Alaskan taxon and greater clarification of its differences from Edmontosaurus will require discovery of adult material from the Prince Creek Formation and/or description of other juvenile specimens from E. regalis and E. annectens.
The establishment of a new species of hadrosaurid, Ugrunaaluk kuukpikensis gen. et sp.
nov. further clarifies the faunal composition of the Prince Creek
Formation and contributes to a growing body of evidence that the
paleo-Arctic hosted a distinct and endemic polar, early Maastrichtian
dinosaurian fauna. Ongoing field work in the formation and taxonomic
clarifications of existing material will help to further establish the
faunal composition of the unit and add critical new data to test
hypotheses of dinosaur provinciality in Laramidia during the latest
Cretaceous.
Hirotsugu Mori, Patrick S. Druckenmiller, and Gregory M. Erickson. 2015.
A New Arctic Hadrosaurid from the Prince Creek Formation (lower
Maastrichtian) of northern Alaska. Acta Palaeontologica Polonica. in press. doi: 10.4202/app.00152.2015
Alaskan duck-billed dinosaur find spurs physiological mystery http://www.slashgear.com/alaskan-duck-billed-dinosaur-find-spurs-physiological-mystery-22405828/ via @slashgear
Newly discovered hadrosaur dino was one serious, cold-winter survivor
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