Cloverly Formation


Cloverly Formation
Cloverly Formation
Stratigraphic range: Early Cretaceous
Type Geological formation
Location
Region North America

The Cloverly Formation are Lower Cretaceous strata located in Montana and Wyoming, in the western United States. The term now includes strata that had formerly been called the Dakota Formation in central and southern Wyoming.[citation needed]

Contents

Members

In the Bighorn Basin region along the Montana - Wyoming border, the Cloverly is divided into several members.

Brightly colored Himes Member of the Cloverly Formation near Shell, Wyoming. These Lower Cretaceous rocks have produced numerous dinosaurs.
  • Pryor Conglomerate lies at the base and contains abundant black chert. It is named from thick beds exposed on the west side of the Pryor Mountains.
  • The Little Sheep Member lies in the middle and is composed of pale-purple, gray to almost white, bentonitic mudstone. A radiometric date of 115 +/- 10 MA has been obtained from low in the member (Chen and Lubin 1997), and other near the top at 108.5 +/- 0.2 MA (Burton et al. 2006). These dates confirm that the Cloverly is Aptian-Albian in age.
  • The uppermost member is the Himes Member contains some coarse grained channel deposits, but is primarily brightly, multicolored (variegated) mudstones.

Vertebrate fauna

Animals recovered include the dinosaurs Deinonychus, Microvenator Tenontosaurus, Zephyrosaurus and Sauropelta as well as fragmentary remains of Titanosaurs and Ornithomimids. As well, two genera of turtle Naomichelys and Glyptops and the lungfish Ceratodus.

Dinosaur eggs have been found in Montana.[1]

References for data: Ostrom 1970; Cifelli et al. 1998; Cifelli 1999; Nydam and Cifelli 2002. Possible goniopholidid remains are known from the formation.

Ornithischians

Ornithischians reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Sauropelta[2]

S. edwardsorum[2]

Known from "several articulated skeletons" and its armor plates are common fossils.[2] Only one partial skull is known."."[3]

Articulated skeletons are often encased in carbonate caliche deposits that require acid to be removed safely.[2]

Tenontosaurus[2]

T. tilleti[2]

Its remains are the most common of any dinosaur of the formation.[2]

Juvenile remains are sometimes found together, suggesting that young Tenontosaurus lived in sibling groups. Deinonychus teeth are sometimes associated with Tenontosaurus remains suggesting a predator-prey relationship between the two.[2]

Zephyrosaurus[2]

Z. schaffi[2]

Its remains are "very rare."[2]

Saurischians

Theropod eggshell fragments are known from the formation. A partial titanosaurid skeleton catalogued as MOR 334 and possible gastroliths are known from the formation.[2] Unidentifiable ornithomimmid remains are present and most commonly represented by toe bones.[2] Indeterminate allosauroid remains are known from the formation. Remains identified by John Ostrom as Ornithomimus are suspected by Jack Horner to be of a new ornithomimid genus.[2]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Discredited taxon Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative data are in small text; crossed out data are discredited.
Saurischians reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Deinonychus[2]

D. antirrhopus[2]

Its remains are "very rare."[2]

Tenontosaurus remains have been recovered in association with Deinonychus teeth on several occasions suggesting a predator-prey relationship between the two.[2]

Microvenator[2]

M. celer[2]

Its remains are "extremely rare."[2] Known only from a "[p]artial skeleton with partial skull."[5] The specimen lacks feet and is catalogued as AMNH 3041.[6]

The type specimen AMNH 3041[2] was recovered by Barnum Brown from Cloverly strata in Montana in 1933.

Ornithomimus[7]

O. velox[7]

Later found to be indeterminate ornithomimid remains.[7]

Pleurocoelus[7]

Indeterminate[7]

Lizards

Lizards reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes

Paramacellodus

P. keebleri

Mammals

Mammals reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Corviconodon

C. montanensis

Gobiconodon

G. ostromi

Montanalestes

M. keebleri

Turtles

Possible goniopholidid remains are known from the formation.

Turtles reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes

Glyptops[2]

G. pervicax[2]

G. plicatulus[2]

Naomichelys[2]

N. speciosa[2]

Bony fish

Indeterminate amiiformes are known from the formation.

Osteichthyes reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Ceratodus[2]

C. frazieri[2]

See also

Footnotes

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  1. ^ a b c "3.11 Montana, United States; 1. Cloverly Formation," in Weishampel, et al. (2004). Page 556.
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai Horner. Pp. 93-100.
  3. ^ "Table 17.1," in Weishampel, et al. (2004). Page 365.
  4. ^ a b c d e "3.12 Wyoming, United States; 2. Cloverly Formation," in Weishampel, et al. (2004). Page 556.
  5. ^ "Table 8.1," in Weishampel, et al. (2004). Page 167.
  6. ^ "Table 5.1," in Varricchio (2001). Page 44.
  7. ^ a b c d e "3.11 Wyoming, United States; 1. Cloverly Formation" and "3.12 Montana, United States; 2. Cloverly Formation," in Weishampel, et al. (2004). Page 556.

References

  • Burton, D., Greenhalgh, B.W., Britt, B.B., Kowallis, B.J., Elliott, W.S., and Barrick, R. 2006. New radiometric ages from the Cedar Mountain Formation, Utah and the Cloverly Formation, Wyoming: implications for contained dinosaur faunas. Geological Society of America Abstracts with Programs 38(7): 52.
  • Chen, Z.-Q. and Lubin, S. 1997. A fission track study of the terrigenous sedimentary sequences of the Morrison and Cloverly Formations in northeastern Bighorn Basin, Wyoming. The Mountain Geologist 34:51-62.
  • Cifelli, R.L. 1999. Tribosphenic mammal from the North American Early Cretaceous. Nature 401:363-366.
  • Cifelli, R.L., Wible, J.R., and Jenkins, F.A. 1998. Triconodont mammals from the Cloverly Formation (Lower Cretaceous), Montana and Wyoming. Journal of Vertebrate Paleontology 18: 237-241.
  • Horner, John R. Dinosaurs Under the Big Sky (Cloverly Formation). Mountain Press Publishing Company. pp. 93–100. ISBN 0-87842-445-8.
  • Nydam, R.L., and Cifelli, R.L. 2002. Lizards from the Lower Cretaceous (Aptian-Albian) Antlers and Cloverly Formations. Journal of Vertebrate Paleontology 22: 286-298.
  • Ostrom, J. H. 1970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana. Peabody Museum Bulletin 35:1-234
  • Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42–57 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis, Indiana.
  • Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.

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