Paläontologische Zeitschrift

, Volume 85, Issue 2, pp 125–142 | Cite as

A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the origin of the Dermatemys mawii lineage

  • Georgia E. Knauss
  • Walter G. JoyceEmail author
  • Tyler R. Lyson
  • Dean Pearson
Research Paper


A nearly complete turtle shell from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Slope County, North Dakota, represents the most complete remains to date of a Mesozoic kinosternoid turtle and a new species, Hoplochelys clark nov. sp. The new taxon is diagnosable from other representatives of Hoplochelys by the plesiomorphic placement of the humeral/femoral sulcus behind the hyo/hypoplastral suture and the autapomorphic development of an interrupted median (neural) keel. All six previously named Paleocene (Puercan and Torrejonian) representatives of Hoplochelys lack diagnostic characters and are synonymized as Hoplochelys crassa. A phylogenetic analysis reveals that Hoplochelys spp. and Agomphus pectoralis are most parsimoniously placed within Kinosternoidea along the phylogenetic stem of the extant Mesoamerican River Turtle Dermatemys mawii, extending that taxon’s stem lineage from the early Eocene to the late Maastrichtian. The two primary crown lineages of Kinosternoidea are thus known from the Mesozoic and split prior to the late Campanian. The presence of a thickened cruciform plastron, true costiform processes, only three inframarginals, and the reduction of the medial contact of the abdominals are synapomorphies of Chelydroidea, the clade formed by Chelydridae and Kinosternoidae.


Hell Creek Formation North Dakota Maastrichtian Late Cretaceous Kinosternoidea Hoplochelys clark n. sp. Dermatemys mawii 


Eine fast komplette Schildkrötenschale, die in der spätkretazischen (Maastrichtium) Hell Creek Formation in Slope County, Norddakota, gefunden wurde, stellt den bisher vollständigsten mesozoischen Rest einer kinosternoideen Schildkröte dar und wird hier als neue Art Hoplochelys clark beschrieben. Anhand der plesiomorphen Lage des humero/femoralen Sulcus hinter der hyo/hypoplastralen Sutur und des autapomorphisch unterbrochenen medianen Kiels kann die neue Schildkröte von anderen Hoplochelys Arten unterschieden werden. Allen sechs bisher bekannten Arten aus dem Paläozän (Puercium und Torrejonium) fehlen diagnostische Merkmale. Daher werden sie als Hoplochelys crassa synonymisiert. Die phylogenetische Analyse ergibt, dass es am sparsamsten ist, Hoplochelys spp. und Agomphus pectoralis entlang der Stammlinie der heute lebenden Tabascoschildkröte Dermatemys mawii zu platzieren. Das Alter dieser Stammliniengruppe wird daher vom Früheozän ins Spätmaastrichtium zurückverlegt. Die zwei primären Stammlinien der Kinosternoidea sind somit aus dem Mesozoikum bekannt und spalteten sich voneinander vor dem Spätcampanium ab. Die Ausbildung eines verdickten, kreuzförmigen Plastrons, echte rippenartige Fortsätze des Nuchale, nur drei Inframarginalschilder und der Verlust des medianen Kontaktes der Abdominalscuta sind Synapomorphien des Monophylums Chelydroidea, welches von Chelydridae und Kinosternoidea gebildet wird.


Hell Creek Formation Norddakota Maastrichtium Oberkreide Kinosternoidea Hoplochelys clark n. sp. Dermatemys mawii 



We thank Dan Brinkman (YPM), Don Brinkman (TMP), Matt Carrano and Kevin de Queiroz (USNM), Pat Holroyd (UCMP), Carl Mehling (AMNH), Alan Resetar (FMNH), and Greg Watkins-Colwell (YPM) for access to material under their care. R. Sullivan is particularly thanked for providing us access to unpublished material collected by him in New Mexico. Thanks to the Horse Creek Grazing Association for allowing PTRM to collect and curate fossils from the dinosaur site PTRM V95018 where the holotype of H. clark was collected. John Brown and family are also thanked for allowing PTRM to conduct surveys of their land and to collect numerous fossils sites, including two that produced the specimens referred herein to H. clark. Additional referred specimens were collected from public lands managed by the Bureau of Land Management in Montana and North Dakota and the United States Forest Service in North Dakota; we would like to thank numerous staff members for their assistance with obtaining access. Yvonne Lichtenfelt is thanked for preparation of the holotype. Numerous PTRM and YPM students and volunteers helped recover the described material. Don Brinkman and Jim Parham helped improve the quality of this manuscript. Funding for this project was provided by the Doris O. and Samuel P. Welles Research Fund (UCMP) and the University of Iowa Department of Geoscience Littlefield Fund to G.K., a National Science Foundation Graduate Research Fellowship to T.R.L., and by a grant from the University of Tübingen to W.G.J.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Georgia E. Knauss
    • 1
    • 2
  • Walter G. Joyce
    • 3
    • 4
    Email author
  • Tyler R. Lyson
    • 5
    • 6
  • Dean Pearson
    • 7
  1. 1.SWCA Environmental Consultants, Inc.SheridanUSA
  2. 2.Department of GeoscienceUniversity of IowaIowa CityUSA
  3. 3.Institut für GeowissenschaftenUniversity of TübingenTübingenGermany
  4. 4.Division of Vertebrate PaleontologyYale Peabody Museum of Natural HistoryNew HavenUSA
  5. 5.Department of Geology and GeophysicsYale UniversityNew HavenUSA
  6. 6.Marmarth Research FoundationMarmarthUSA
  7. 7.Pioneer Trails Region MuseumBowmanUSA

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