St. Marys Formation

The St. Marys Formation is a geologic formation in Maryland and Virginia, United States. It preserves fossils dating back to the Miocene Epoch of the Neogene period. It is the youngest Miocene formation present in the Calvert Cliffs and is part of the Chesapeake Group.

St. Marys Formation
Stratigraphic range: Neogene
Type	Formation
Unit of	Chesapeake Group
Underlies	Eastover Formation
Overlies	Choptank Formation
Location
Region	Maryland, Virginia
Country	United States

Vertebrate paleofauna

A diverse vertebrate paleofauna is known from the St. Marys Formation:

Cartilaginous fish

Genus	Species	Notes	Tooth example	Ref.
Notorynchus	N. primigenius	This species is possibly synonymous with the broadnose sevengill shark.	Notorhynchus primigenius from the Calvert Formation	[1]
Hexanchus	H. gigas	A species of cow shark. This species is extremely rare in this formation.	Hexanchus gigas teeth (not from St. Marys Formation)	[1]
Squalus		Commonly known as the spurdog.		[1]
Squatina		Commonly known as the angel shark.		[1]
Rhincodon	R. typus	Commonly known as the whale shark. This species is extremely rare in this formation.	Modern Rhincodon typus teeth	[1]
Carcharodon	C. hastalis	Putative ancestor to the extant great white shark	Carcharodon hastalis from the Calvert Formation	[1]
Carcharomodus	C. escheri	Commonly known as Escher's mako. It is also known as Carcharodon subserratus and is sometimes placed in Isurus. It is extremely rare in this formation.	Carcharomodus escheri teeth from Germany	[1]
Otodus	O. megalodon	This is the largest shark known to have existed.	C. megalodon from Chile	[1]
Alopias	A. latidens	This species may be synonymous with the extant common thresher shark.	Alopias latidens from the Old Church Formation	[1]
Mustelus		Commonly known as smooth-hounds		[1]
Hemipristis	H. serra	Commonly known as the snaggletooth shark. It is related to the extant snaggletooth shark.	Hemipristis serra teeth (Bone Valley)	[1]
Carcharhinus	C. falciformus	Commonly known as the silky shark.	Carcharhinus falciformis upper teeth (modern)	[1]
	C. leucas	Commonly known as the bull shark	Carcharhinus leucas teeth (modern)	[1]
	C. perezii	Commonly known as the Caribbean reef shark	Carcharhinus perezii upper teeth (modern)	[1]
	C. priscus	An extinct requiem shark		[1]
	C. plumbeus	Commonly known as the sandbar shark	Carcharhinus plumbeus upper teeth (modern)	[1]
Negaprion	N. brevrostris	Commonly known as the lemon shark	Negaprion brevirostris upper teeth	[1]
Rhizoprionodon		Commonly known as the sharpnose shark		[1]
Pteromylaeus		Commonly known as the bull ray		[1]
Aetobatus		Commonly known as the eagle ray		[1]

Bony fish

Genus	Notes	Image	Ref.
Acipenseridae gen. indet.		Extant Japanese sturgeon (Acipenser schrenckii)	[1]
Lepisosteus		Extant spotted gar (Lepisosteus oculatus)	[1]
Amia	cf. A. calva	Extant Amia calva	[1]
Alosa		Extant Alosa maeotica	[1]
Ictalurus		Drawing of extant Ictalurus punctatus	[1]
Merluccius		Drawing of extant Merluccius merluccius	[1]
Belone	B. countermani	Extant Belona belona	[1][2]
Prionotus		Extant bandtail searobin (Prionotus ophryas)	[1]
Agonidae gen. indet.		Extant Agonus cataphractus	[1]
"Paralbula"	"P." dorisiae		[1]
Lagodon		Extant Lagodon rhomboides	[1]
Stenotomus		Extant Stenotomus chrysops	[1]
Pogonias		Extant black drum	[1]
Sciaenops		Extant Sciaenops ocellatus	[1]
Tautoga		Extant Tautoga onitis	[1]
Astroscopus	A. countermani	Artists rendition of Astroscopus countermani	[3][1]
Sphyraena		Extant school of Sphyraena barracuda	[1]
Istiophoridae gen. indet.		Extant Atlantic blue marlin	[1]

Reptiles

Genus	Species	Notes	Image	Ref.
Thecachampsa	T. antiquus	A Tomistominae	Thecachampsa sp. Vertebra possibly derived from this formation	[1]

Sea mammals

Type	Genus	Species	Notes	Image	Ref.
Sirenians (sea cows)	Metaxytherium	M. floridanum		Metaxytherium floridanum skeleton	[1]
Cetaceans (whales, dolphins and porpoises)	Aulophyseter	A. mediatlanticus	A sperm whale	Artists depiction of Aulophyseter	[4]
	Lophocetus	L. calvertensis			[5]
	Messapicetus			Messapicetus gregarius and M. longirostris skull diagrams	[6]
	Stenasodelphis	S. russellae			[7]

Terrestrial mammals

Name	Notes	Images	Ref.
Procamelus	cf. P. minor	Fossilized Procamelus mummy from Oklahoma	[8]
Desmathyus			[8]
Tapirus		Extant South American tapir (Tapirus terrestris)	[8]
Neohipparion lenticulare		Skeleton and artists rendition of Neohipparion	[8]
Equidae indet.	Larger than Parahippus		[8]
Rhinoceratidae			[8]
Cormohipparion		Cranium of Cormohipparion occidentale	[8]

See also

• Earth sciences portal
• Virginia portal
• Paleontology portal

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