Turtle Graveyard locality: Late/Upper Maastrichtian, North Dakota
collected by Marmarth Research Foundation 1996-2011

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
Reptilia
Theropoda indet. (Marsh 1881)
Lyson and Joyce 2009
'a few isolated bones'
Crocodylia indet. (Owen 1842)
Lyson and Joyce 2009 1 specimen
dentary
Reptilia - Baenidae
Baenidae indet. Cope 1882
Joyce et al. 2019
new species
Palatobaena cohen n. sp. Lyson and Joyce 2009
Lyson and Joyce 2009 5 specimens
YPM 57498, (holotype) a complete uncrushed skull, mandible, and shell; MRF 257, complete skull and mandible; MRF 259, complete skull; MRF 263, complete skull; MRF 123, shell missing part of carapace
Cedrobaena putorius (Gaffney 1972)
Lyson and Joyce 2009
MRF 239 complete skull
Peckemys brinkman Lyson and Joyce 2009
Lyson and Joyce 2009 1 specimen
recombined as Cedrobaena brinkman
MRF 231 (skull)
Reptilia - Testudines - Trionychidae
Axestemys infernalis Joyce et al. 2019
Joyce et al. 2019
Reptilia - Testudines
Gilmoremys lancensis (Gilmore 1916)
12 specimens
MRF 275, nearly complete skull; MRF 277, nearly complete skull; MRF 309, nearly complete skull and anteroposteriorly crushed skull; MRF 758, nearly complete skull (Fig. 6); MRF 759, partial skull, associated jaw and articulated anterior cervical column; MRF 525, nearly complete carapace; MRF 516, a left hyoplastron; MRF 565, a right hyoplastron; MRF 536, a right hyoplastron; MRF 534, a left hypoplastron; MRF 467, a right hypoplastron; MRF 549, a right xiphiplastron; MRF 575, a left xiphiplastron
Chondrichthyes - Rajiformes - Rhinobatidae
Myledaphus sp. Cope 1876
Lyson and Joyce 2009
cartillaginous jaw elements
see common names

Geography
Country:United States State/province:North Dakota County:Slope
Coordinates: 46.3° North, 104.0° West (view map)
Paleocoordinates:52.6° North, 77.4° West
Basis of coordinate:based on political unit
Geographic resolution:small collection
Time
Period:Cretaceous Epoch:Late/Upper Cretaceous
Stage:Maastrichtian 10 m.y. bin:Cretaceous 8
Key time interval:Late/Upper Maastrichtian
Age range of interval:72.10000 - 66.00000 m.y. ago
Stratigraphy
Geological group:Montana Formation:Hell Creek
Stratigraphic resolution:member
Stratigraphy comments: Stratigraphically the quarry is placed in the lower third of the Hell Creek Formation (latest Maastrichtian), approximately 65 m below the Fort Union
formational contact.
The site is located in the lower third of the [Hell Creek] formation, approximately 65 m below the formational contact with the Fort Union Formation
Lithology and environment
Primary lithology: sandstone
Secondary lithology:tabular mudstone
Includes fossils?Y
Lithology description: The fossil-bearing layer varies laterally in thickness from 80–120 cm over a distance of 16 m (Fig. 1). It lies on top of an undulatory, tabular mudstone with scour marks bearing 245degrees southeast. Directly overlying the scoured bed is a structureless layer of rip-up clasts and sand that varies in thickness from 1–12 cm (Fig. 1). The clasts are typically 1 or 2 cm in diameter; however, clasts 3 to 4 cm in diameter are not uncommon. The fossil material, as well as numerous lignified logs, is found in or on top of this layer (Fig. 1). Hollow sandstone moulds up to 10 cm in diameter preserve many of these logs three dimensionally. Branches and turtle shells commonly extend into the overlying unconsolidated sandstone layer. The upper portion of this fining upward unit preserves heterolithic cross-beds dipping approximately 20degrees to the southeast. The bed is 60–70 cm thick in the southeastern part of the quarry and it pinches out into a laminated clay unit on the northwestern portion of the quarry. Discontinuous lag stringers with clay clasts ranging in size from a few mm to 3 cm in diameter are found throughout this portion of the sequence. This layer is overlain with a laminated clay unit, which varies laterally in thickness from 2–18 cm (Fig. 1). The textural and structural data indicate that the entire sequence was the result of deposition from fluvial currents of decreasing energy (Boggs, 2006).
Environment:lacustrine - small
Geology comments: 2009: The unit in which the fossils are preserved is overlain with a series of sandstone units, a large structureless conglomerate-like unit with clay clasts up to 40 cm in diameter that cuts into the underlying sandstone unit and pinches out to the southeast, and a series of laminated clay units that lie in between sandstone units (Fig. 1). The alternating sequence of high velocity sandstone deposits and zero velocity laminated clay units, as well as the incising channels, indicate an ephemeral paleo-environment, such as a pond or shallow stream, which would periodically flood and dry out (Murphy et al., 2003).

2011: The depositional setting is interpreted as an oxbow lake in which many turtles aggregated and perished during a drought and where the slightly disarticulated carcasses were later washed together after the onset of rains.
Taphonomy
Modes of preservation:body
Lagerst�tten type:concentrate
Degree of concentration:-single event
Size of fossils:macrofossils
Spatial orientation:random
Abundance in sediment:abundant
Fragmentation:occasional
Temporal resolution:snapshot
Spatial resolution:autochthonous
Collection methods and comments
Collection methods:selective quarrying,surface (in situ),field collection
Collection size:100 specimens
Reason for describing collection:taxonomic analysis
Collectors:Marmarth Research Foundation Collection dates:1996-2011
Collection method comments: MRF, Marmarth Research Foundation, Marmarth, North Dakota, U.S.A.
This locality is an approximately 125 square meter large quarry, in which a single, fossiliferous layer has been mined by MRF for vertebrate fossil remains over the course of the last 15 years.
Taxonomic list comments:2011: To date, the quarry has produced more than 100 turtle specimens, mostly baenids, including the skull and shell of Palatobaena cohen Lyson and Joyce 2009a, a skull each of Peckemys brinkman Lyson and Joyce 2009b and Cedrobaena putorius (Gaffney, 1972), and a large series of skulls and shells of an unnamed representative of Eubaena (Lyson and Joyce, 2009a, 2009b).


2009: The locality, named Turtle Graveyard, has yielded an unsurpassed number of slightly disarticulated baenid turtle specimens including more than 70 shells, 35 skulls, and other postcranial remains partial, disarticulated trionychid turtle skeletons, teeth, and cartilaginous jaw elements from the ray fish Myledaphus, a lone unidentified crocodile dentary, and a few isolated bones from an unidentified theropod
Metadata
Database number:122903
Authorizer:R. Benson, E. Vlachos, D. Nicholson Enterer:R. Benson, D. Nicholson, E. Vlachos
Modifier:M. Carrano Research group:vertebrate
Created:2012-01-07 02:43:19 Last modified:2021-05-05 11:12:07
Access level:the public Released:2012-01-07 02:43:19
Creative Commons license:CC BY
Reference information

Primary reference:
39183. W. G. Joyce and T. R. Lyson. 2011. New material of Gilmoremys lancensis nov. comb. (Testudines: Trionychidae) from the Hell Creek Formation and the diagnosis of plastomenid turtles. Journal of Paleontology 5(3):422-459 [R. Benson/R. Benson]

Secondary references:

70995 W. J. Joyce, D. B. Brinkman, and T. R. Lyson. 2019. A new species of trionychid turtle, Axestemys infernalis sp. nov., from the Late Cretaceous (Maastrichtian) Hell Creek and Lance formations of the Northern Great Plains, USA. Palaeontologia Electronica 22(3):72:1-28 [E. Vlachos/E. Vlachos/P. Mannion]
39184 T. R. Lyson and W. G. Joyce. 2009. A new species of Palatobaena (Testudines: Baenidae) and a maximum parsimony and Bayesian phylogenetic analysis of Baenidae. Journal of Paleontology 83(3):457-470 [R. Benson/R. Benson/P. Mannion]
39185 T. R. Lyson and W. G. Joyce. 2009. A revision of Plesiobaena (Testudines: Baenidae) and an assessment of baenid ecology across the K/T boundary. Journal of Paleontology 83(6):833-853 [R. Benson/R. Benson]