Demopolis Chalk Explained

Demopolis Chalk
Type:	Geological formation
Age:	Upper Cretaceous
Period:	Campanian
Prilithology:	Chalk
Namedfor:	Demopolis, Alabama
Region:	Alabama, Mississippi, Tennessee
Country:	United States
Unitof:	Selma Group
Subunits:	Bluffport Marl Member
Underlies:	Ripley Formation
Overlies:	Mooreville Chalk Formation

The Demopolis Chalk is a geological formation in North America, within the U.S. states of Alabama, Mississippi, and Tennessee. The chalk was formed by pelagic sediments deposited along the eastern edge of the Mississippi embayment during the middle Campanian age of the Late Cretaceous.^[1] It is a unit of the Selma Group and consists of the upper Bluffport Marl Member and a lower unnamed member.^[2] Dinosaur and mosasaur remains are among the fossils that have been recovered from the Demopolis Chalk.^{[2] [3]}

Vertebrate paleofauna

Fish

Cartilaginous fish

Cartilaginous fish of the Demopolis Chalk Formation
Genus	Species	Presence	Notes	Images
Chimaeriformes indet.^[4]		Alabama
Cretolamna	C. appendiculata		An otodontid
Ischyrhiza	I. mira		A sclerorhynchid
Scapanorhynchus	S. texanus		A mitsukurinid
Serratolamna	S. serrata?		A lamniform shark
Squalicorax	S. kaupi	Alabama	Anacoracids
	S. pristodontus
	S. sp.

Bony fish

Bony fish of the Demopolis Chalk Formation
Genus	Species	Presence	Notes	Images
Enchodus	E. ferox	Alabama	Enchodontids
	E. gladiolus
	E. petrosus
Protosphyraena	P. sp.	Alabama	A pachycormiform
Saurodon	S. sp.	Alabama	An ichthyodectiform
Stratodus	S. sp.	Alabama	An aulopiform
Xiphactinus	X. vetus^[5]		An ichthyodectid

Reptiles

Dinosaurs

Indeterminate hadrosaurid remains have been found in Tennessee. Possible indeterminate tyrannosaurid remains have been found in Alabama.

Mosasaurs

Mosasaurs of the Demopolis Chalk
Genus	Species	Presence	Notes	Images
Clidastes	C. propython	Alabama	A mosasaurine
Halisaurus	H. sp.	Alabama	A halisaurine
Mosasaurus	M. conodon	Alabama	Mosasaurines
	M. cf. missouriensis
Platecarpus	P. cf. somenensis	Alabama	A plioplatecarpine
Plioplatecarpus	P. primaevus^[6]		A plioplatecarpine
Prognathodon	P. rapax		Mosasaurines
	P. cf. solvayi
Tylosaurus	T. sp.	Alabama	A tylosaurine

Turtles

Turtles of the Demopolis Chalk
Genus	Species	Presence	Notes	Images
Asmodochelys	A. parhami^[7]	Geographically present in Alabama and Mississippi.	A marine ctenochelyid turtle
Chedighaii	C. barberi	Alabama	A bothremydid
Ctenochelys	C. cf. tennuitesta	Alabama	A ctenochelyid
Prionochelys	P. matutina?	Alabama	A ctenochelyid
Protostega	P. gigas	Alabama	A protostegid

See also

• List of dinosaur-bearing rock formations
• List of fossil sites

Notes and References

1. 10.1671/0272-4634(2005)025[0119:ANGASO]2.0.CO;2 . Carr . T.D. . Williamson . T.E. . Schwimmer . D.R. . 2005 . A new genus and species of tyrannosauroid from the Late Cretaceous (middle Campanian) Demopolis Formation of Alabama . Journal of Vertebrate Paleontology . 25 . 1. 119–143 . 86243316 .
2. Kiernan . Caitlin R. . 2002 . Stratigraphic distribution and habitat segregation of mosasaurs in the Upper Cretaceous of western and central Alabama, with an historical review of Alabama mosasaur discoveries . Journal of Vertebrate Paleontology . 22 . 1 . 91–103 . 2024-06-12 . 10.1671/0272-4634(2002)022[0091:SDAHSO]2.0.CO;2 .
3. Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. .
4. Kejiri, T.. Ebersole, J.A.. Blewitt, H.L.. Ebersole, S.M.. 2013. An Overview of Late Cretaceous Vertebrates from Alabama. Bulletin of the Alabama Museum of Natural History. 31. 1. 46–71.
5. 10.1080/02724634.1997.10011007 . Schwimmer . D. R. . Stewart . 1997 . J. D. . Williams . G. Dent . Xiphactinus vetus and the Distribution of Xiphactinus Species in the Eastern United States . Journal of Vertebrate Paleontology . 17 . 3 . 610–615 .
6. Web site: The Platecarpus Collection: A virtual collection of Platecarpus specimens from Kansas and elsewhere . 2024-06-12 . Everhart . Mike . 2008-04-18 . Oceans of Kansas Paleontology . https://web.archive.org/web/20240317105348/http://www.oceansofkansas.com/mus-plat.html. 2024-03-17. live.
7. Andrew D. Gentry . Jun A. Ebersole . Caitlin R. Kiernan . 2019 . Asmodochelys parhami, a new fossil marine turtle from the Campanian Demopolis Chalk and the stratigraphic congruence of competing marine turtle phylogenies . Royal Society Open Science . 6 . 12 . Article ID 191950 . 10.1098/rsos.191950 . 31903219 . 6936288 . 2019RSOS....691950G .