Arundel Formation

Arundel Formation Stratigraphic range: Lower Cretaceous
Type	sedimentary
Unit of	Potomac Group
Underlies	Patapsco Formation
Overlies	Patuxent Formation
Thickness	up to 125 feet[1]
Lithology
Primary	clay
Location
Region	Maryland, Washington D. C.
Country	United States
Type section
Named by	W. B. Clark, 1897[1]

The Arundel Formation, also known as the Arundel Clay, is a clay-rich sedimentary rock formation, within the Potomac Group, found in Maryland^[2] of the United States of America. It is of Aptian age (Lower Cretaceous). This rock unit had been economically important as a source of iron ore, but is now more notable for its dinosaur fossils. Although often considered a formation, it may be only oxbow swamp facies within the Potomac Group.^[3]

Vertebrate paleofauna

Dinosaurs

Dinosaurs present include possibly the large theropod Acrocanthosaurus,^[4][5] the poorly known theropods "Allosaurus (or "Dryptosaurus") medius", "Creosaurus (or "Dryptosaurus") potens" (also known as "Capitalsaurus"), and "Coelurus gracilis", the ornithomimosaurian "Coelosaurus affinis", the sauropods Astrodon and Pleurocoelus, the nodosaurid Priconodon,^[6] a possible basal ceratopsian, and potentially the ornithopod Tenontosaurus.^[3] Other vertebrates are not as well-known from the formation, but include a freshwater shark, a lungfish, at least three genera of turtles, and at least one crocodilian.^[3]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Dinosaurs reported from the Arundel Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Allosaurus[7]	"A." medius[7]	Maryland[7]		"Tooth."[8]	An indeterminate theropod tooth.	Astrodon Deinonychus Tenontosaurus
Astrodon[9]	A. johnstoni[9]	Maryland[7] Washington D.C.[10]		"Tooth."[11]
"Capitalsaurus"[12]	"C." potens	Maryland[7]		"Vertebra."[8]	A neotheropod.
Coelosaurus[7]	C. affinis[7]				Junior synonym of "Dryosaurus" grandis
Coelurus[7]	"C." gracilis			"Manual ungual and teeth."[8]	Probably a dromaeosaurid.
Creosaurus[7]	"C." potens[7]				Reclassified as "Capitalsaurus" potens
Deinonychus[7]	Indeterminate[7]	Maryland[7]			A dromaeosaurid
Dryosaurus	"D." grandis	Maryland[7]		"Limb elements."[13]	An indeterminate theropod sometimes considered a species of Ornithomimus and originally described as a species of the ornithischian Dryosaurus
Dryptosaurus	"D." medius				Synonym of "Allosaurus" medius
	"D." potens[7]				Synonym of "Capitalsaurus" potens
Ornithomimus	"O." affinis				Junior synonym of "Druosaurus" grandis
Pleurocoelus[7]	P. altus[7]	Maryland[7]		"Tibia [and] fibula."[14]
	P. nanus[7]	Maryland[7]
	Indeterminate[10]	Washington D. C.[10]
Priconodon[7]	P. crassus[7]	Maryland[7]		"Teeth, tibia."[15]
Tenontosaurus[16]	Indeterminate[16]	Maryland[7]

Pterosaurs

Unassigned pteradactyloid tracks.^[17]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Pterosaurs of the Arundel Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Pteraichnus[17]				[17]

Other fossils

W. B. Clark (1897) described lignitized trunks of trees often found in upright positions with their roots still intact.^[1]

G. J. Brenner (1963) described spores and pollen within the formation.^[18]

See also

• List of dinosaur-bearing rock formations

Footnotes

1. Clark, W.B., 1897, Outline of present knowledge of the physical features of Maryland: Maryland Geological Survey Volume Series, v. 1, pt. 3, p. 172-188.
2. "Geologic Map Legends". Coastal Plain Rocks and Sediments. Maryland Geological Survey. Archived from the original on 26 May 2011. Retrieved 27 June 2011.
3. Kranz, Peter M. (1998). "Mostly dinosaurs: a review of the vertebrates of the Potomac Group (Aptian Arundel Formation), USA". In Lucas, Spencer G.; Kirkland, James I.; & Estep, J.W. (eds.). Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin 14. pp. 235–238.
4. Harris, Jerald D. (1998). "Large, Early Cretaceous theropods in North America". In Lucas, Spencer G.; Kirkland, James I.; & Estep, J.W. (eds.). Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin 14. pp. 225–228.
5. Lipka, Thomas R. (1998). "The affinities of the enigmatic theropods of the Arundel Clay facies (Aptian), Potomac Formation, Atlantic Coastal Plain of Maryland". In Lucas, Spencer G.; Kirkland, James I.; & Estep, J.W. (eds.). Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin 14. pp. 229–234.
6. Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loueff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth M.P.; Noto, Christopher N. (2004). "Dinosaur distribution". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 517–606. ISBN 0-520-24209-2.
7. "3.25 Maryland, United States; 1. Arundel Clay," in Weishampel, et al. (2004). Page 556.
8. "Table 4.1," in Weishampel, et al. (2004). Page 78.
9. "3.25 Maryland, United States; 1. Arundel Clay" and "3.34 Washington D. C., United States; 1. Arundel Clay," in Weishampel, et al. (2004). Page 556.
10. "3.34 Washington D. C., United States; 1. Arundel Clay," in Weishampel, et al. (2004). Page 556.
11. "Table 13.1," in Weishampel, et al. (2004). Page 270.
12. Kranz, D. 1998. Mostly Dinosaurs: A Review of the Vertebrates of the Potomac Group (Aptian Arundel Formation), USA, in Lucas, Kirkland and Estep, eds., 1998: 235-238.
13. "Table 6.1," in Weishampel, et al. (2004). Page 139.
14. "Table 13.1," in Weishampel, et al. (2004). Page 266.
15. "Table 17.1," in Weishampel, et al. (2004). Page 368.
16. Listed as "?Tenontosaurus sp." in "3.25 Maryland, United States; 1. Arundel Clay," in Weishampel, et al. (2004). Page 556.
17. Lockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. ISSN 1612-4138.
18. Brenner, Gilbert J., 1963, The spores and pollen of the Potomac Group of Maryland: Maryland Geological Survey Bulletin, no. 27, 215 p.

References

• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.

Coordinates: 39°3′N 76°38′W / 39.050°N 76.633°W