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The Arkadelphia Marl, also called the Arkadelphia Formation, is a geologic formation in Arkansas in Clark, Nevada, and Hempstead counties. It preserves fossils dating back to the late Maastrichtian stage of the Cretaceous period.

Paleofauna

Bony fish

Bony fish reported from the Arkadelphia Formation
Genus	Species	Presence	Material	Notes	Images
Albulidae indet.	Indeterminate	Cabot, Arkansas.	4 small, eroded otoliths.	A bonefish.
Ampheristus	A. cf. A. americanus	Cabot, Arkansas.	6 otoliths.	An ophidiiform.
Anguilla	A.? chickasawae	Cabot, Arkansas.	6 otoliths.	An eel.
Apateodus	A. crenellatus?	Cabot, Arkansas.	3 otoliths.	An aulopiform.
Arius	A.? subtilis	Cabot, Arkansas.	A well-preserved otolith (DMNH 2021-09-11).	A catfish.
Clupeiformes? indeterminate	Indeterminate	Cabot, Arkansas.	An eroded, broken otolith (DMNH 2021-09-10).	A clupeiform.
Echiophis	E. aff. E. semisphaeroides	Cabot, Arkansas.	11 otoliths.	An eel.
Elopothrissus	E. sp.	Cabot, Arkansas.	One otolith (DMNH 2021-09-03).	A bonefish.
Elops	E. sp.	Cabot, Arkansas.	A small, broken otolith (DMNH 2021-09-01).	A ladyfish.
Eutawichthys	E. maastrichtiensis	Cabot, Arkansas.	21 otoliths.	A beryciform.
	E. cf. E. stringeri	Cabot, Arkansas.	48 otoliths.	A beryciform.
	E. zideki	Cabot, Arkansas.	287 otoliths.	A beryciform.
Gadiformes indeterminate	Indeterminate	Cabot, Arkansas.	11 very small or broken otoliths.	A gadiform.
Genartina	G. sp. 1	Cabot, Arkansas.	One otolith (DMNH 2021-09-04).
Kokenichthys	K. navis	Cabot, Arkansas.	2 eroded otoliths.	An osteoglossiform.
Lapillus type 1	Indeterminate	Cabot, Arkansas.	A small, slightly eroded otolith (DMNH 2021-09-31).	An unidentified fish otolith.
Muraenanguilla	M.? sp.	Cabot, Arkansas.	2 worn, broken otoliths.	An eel.
Osmeroides	O. sp.	Cabot, Arkansas.	3 otoliths.
Palaeogadus	P.? belli	Cabot, Arkansas.	Multiple otoliths.	A gadiform.
	P. cf. P. weltoni	Cabot, Arkansas.	A small, slightly eroded otolith (DMNH 2021-09-23).	A gadiform.
Protobythites	P. brzobohatyi	Cabot, Arkansas.	4 otoliths.	An ophidiiform.
Tippaha	T. mythica	Cabot, Arkansas.	8 otoliths.	A holocentriform.
Vorishia	V. vulpes	Cabot, Arkansas.	1,537 otoliths.	A catfish.

Rays

Rays reported from the Arkadelphia Formation
Genus	Species	Presence	Material	Notes	Images
Dasyatis	D. sp.	Ouachita River northwest of Malvern, Arkansas.	3 oral teeth (AMNH 20194-20196)	A stingray.
Ischyrhiza	I. avonicola	Ouachita River northwest of Malvern, Arkansas.	8 teeth (AMNH 20164-20171).	A sawskate.
	I. mira	Ouachita River northwest of Malvern, Arkansas.	3 oral teeth (AMNH 20172-20174).	A sawskate.
Ptychotrygon	P. cf. P. vermiculata	Ouachita River northwest of Malvern, Arkansas.	4 oral teeth (AMNH 20183-20186).	A sawskate.
Raja	R. farishi	Ouachita River northwest of Malvern, Arkansas.	3 oral teeth (AMNH 20187-20189).	A skate.
Rhinobatos	R. casieri	Ouachita River northwest of Malvern, Arkansas.	4 oral teeth (AMNH 20160-20163).	A guitarfish.
Rhombodus	R. binkhorsti	Ouachita River northwest of Malvern, Arkansas.	4 oral teeth (AMNH 20190-20193)	A rajiforme.
Schizorhiza	S. cf. S. stromeri	Ouachita River northwest of Malvern, Arkansas.	5 rostral teeth (AMNH 20178-20182).	A sawskate.
Sclerorhynchus	S. sp.	Ouachita River northwest of Malvern, Arkansas.	3 rostral teeth (AMNH 20175-20177).	A sawskate.

Sharks

Sharks reported from the Arkadelphia Formation
Genus	Species	Presence	Material	Notes	Images
Carcharias	C. cf. C. holmdelensis	Ouachita River northwest of Malvern, Arkansas.	5 anterior teeth (AMNH 20139-20143).	A sand shark.
Galeorhinus	G. girardoti	Ouachita River northwest of Malvern, Arkansas.	4 lateral teeth (AMNH 20156-20159).	A houndshark.
Ginglymostoma	G. lehneri	Ouachita River northwest of Malvern, Arkansas.	4 lateral teeth (AMNH 20132-20135).	A carpet shark.
Odontaspis	O. aculeatus	Ouachita River northwest of Malvern, Arkansas.	2 lateral teeth (AMNH 20137 & 20138).	A sand shark.
Plicatoscyllium	P. cf. P. derameei	Ouachita River northwest of Malvern, Arkansas.	Lateroanterior tooth (AMNH 20136).	A carpet shark.
Serratolamna	S. serrata	Ouachita River northwest of Malvern, Arkansas.	6 teeth (AMNH 20144-20149).	A mackerel shark.
Squalicorax	S. kaupi	Ouachita River northwest of Malvern, Arkansas.	6 lateral teeth (AMNH 20150-10155).	A mackerel shark.
Squatina	S. hassei	Ouachita River northwest of Malvern, Arkansas.	4 lateral teeth (AMNH 20128-20131).	An angelshark.

See also

• List of fossiliferous stratigraphic units in Arkansas
• Paleontology in Arkansas

References

1. McFarland, John David (2004) . "Stratigraphic summary of Arkansas" (PDF). Arkansas Geological Commission Information Circular. 36: 31. Archived from the original (PDF) on 2016-12-21. Retrieved 2018-01-12.
2. Hill, R.T. (1888). "The Neozoic geology of southwestern Arkansas". Arkansas Geological Survey Annual Report 1888. 2: 33, 39, 53–56, 72, 188.
3. "ARKADELPHIA MARL/FORMATION". Archived from the original on 2016-08-19. Retrieved 2016-07-31.
4. "Arkadelphia Marl (ARKad;0)".
5. ^ Stringer, Gary L.; Sloan, James Carson (2023-05-25). "First Cretaceous teleostean otolith assemblage (Arkadelphia Formation, upper Maastrichtian) from Arkansas, USA, early Gadiformes, and the Western Interior Seaway". PaleoBios. 40 (3). doi:10.5070/P940361192. ISSN 2373-8189.
6. ^ Becker, Martin A.; Chamberlain Jr, John A.; Wolf, George E. (2006). "Chondrichthyans from the Arkadelphia Formation (Upper Cretaceous: Upper Maasstrichtian) of Hot Spring County, Arkansas". Journal of Paleontology. 80 (4): 700–716.

• Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.

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