Calvert Formation

Calvert Formation
Calvert Formation
Stratigraphic range: Early to Middle Miocene (Aquitanian-Langhian) PreꞒ Ꞓ O S D C P T J K Pg N
	Outcrops of the Calvert Formation at the Calvert Cliffs State Park
Type	Formation
Unit of	Chesapeake Group
Underlies	Choptank Formation
Overlies	Old Church Formation
Location
Region	Maryland, Virginia, Delaware
Country	United States
Type section
Named for	Calvert County

The Calvert Formation is a geologic formation in Maryland, Virginia, and Delaware. It preserves fossils dating back to the early to middle Miocene epoch of the Neogene period, between 23 and 14 million years ago.^[1] It is one of the three formations which make up the Calvert Cliffs, all of which are part of the Chesapeake Group.

Fossils

The Calvert Formation is extremely fossiliferous, although the most fossiliferous layers constitute a relative small section of it, dating to about 16 to 14.5 million years ago. Sediments under these layers are composed of either fine sand with few shells or (for the earliest layers) diatomite.^[1] Some of the fossil species represented include the following:^[2]^[3]

Chondrichthyes

Holocephalians


Genus	Species	Family	Material	Notes
Edaphodon	Edaphodon sp.	Callorhynchidae	two well preserved mandibular plates	Similar to E. sweeti
Ischyodus	Ischyodus sp.	Callorhynchidae	many tooth fragments occasional mandibular plates
Chimaera	Chimaera sp.	Chimaeridae

Elasmobranchii


Genus	Species	Family	Material	Notes	Images
Notorynchus	N. primigenius^[2]	Hexanchidae		Similar to extant N. cepedianus but differs in distribution.^[2]
Hexanchus	H. gigas^[2]	Hexanchidae		Far less common then N. primigenus^[2]
Echinorhinus	E. blakei^[2]	Echinorhinidae	Teeth and bramble thorns^[2]	One of the rarest sharks in the cliffs, prefers deeper waters^[2]
Squalus	Squalus sp. 1 Squalus sp. 2^[2]	Squalidae	Very rare^[2]	Two forms of teeth, one (S. sp. 2) similar to Squalus acanthias^[2]
Squatina	Squatina sp.^[2]	Squatinidae	Teeth and Dermal thorns^[2]
Rhincodon	R. typus^[2]	Rhincodontidae		Very similar to modern R. typus^[2]	A living whale shark
Carcharias	C. cuspidatus C. taurus C. reticulatus^[2]	Odontaspididae
Carcharoides	C. catticus^[2]	Lamnidae
Isurus	I. oxyrinchus I. retroflexus^[2]	Lamnidae			Living Isurus oxyrinchus
Carcharodon	C. hastalis C. subserratus^[2]	Lamnidae
Otodus	O. chubutensis O. megalodon^[2]	Otodontidae
Parotodus	P. benedenii^[2]	incertae sedis
Alopias	A. cf. vulpinus A. cf. superciliosus A. grandis^[2]	Alopiidae		A second large species of Alopias is known from teeth with larger and coarser serrated cutting edges then A. grandis
Cetorhinus	Cetorhinus sp.^[2]	Cetorhinidae	Known exclusively from vertebral centra^[2]	Two species C. parvus and C. maximus are known from the time making identification difficult^[2]
Scyliorhinidae sp.^[2]		Scyliorhinidae
Mustelus	Mustelus sp^[2].	Triakidae		A smooth-hound shark
Hemipristis	H. serra^[2]	Hemigaleidae	Teeth and vertebra, a partial skeleton is held in private collection^[2]	Teeth where found in association with a Squalodon skeleton, possibly from predation or scavenging^[2]	Reconstructed fossil jaw of the shark Hemipristis serra, Florida Museum of Natural History
Galeocerdo	Galeocerdo aduncus^[2]	Galeocerdonidae		Teeth have two morphologies and it is unclear whether this is because of sexual dimorphism or both are produced by the same individuals^[2]
Physogaleus	P. hemmooriensis^[2]
Carcharhinus	C. cf. altimus C. falciformis C. leucas C. macloti C. perezii C. priscus C. plumbeus^[2]	Carcharhinidae	Teeth distinctive to each species and indeterminate vertebral remains^[2]	C. cf. altimus is known from teeth similar to modern bignose shark^[2] Teeth from C. falciformis have been found in association with Squalidon remains^[2] C. leucas teeth from the Calvert cliffs reach a maximum height of 18mm smaller then modern examples of the species^[2]
Negaprion	N. eurybathrodon ^[2]	Carcharhinidae		A lemon shark
Rhizoprionodon	R. sp^[2]	Carcharhinidae		Formerly assigned to R. ficheuri due to similarity of teeth but due to high endemism in modern genus this is probably not the case^[2]
Sphyrna	Sphyrna laevissima^[2]			An early hammerhead^[2]

Rays and other cartilaginous fish

Bony fish

Acipenseridae indet.
Bagre sp.
Brotula sp.
Pogonias sp.
Sciaenops sp.
Tautoga sp.
Acanthocybium cf. solandri
Thunnus sp.
Istiophorus cf. platypterus
Ranzania grahami
Ranzania tenneyorum
Ariopsis stauroforus
Trisopterus sculptus
Micromesistius cognatus
Prionotus
Lophius sp.
Paralbula dorisiae
Morone
Lophokatilus ereboorensis
Rachycentron sp.
Pomatomus sp.
Lagodon sp.
Micropogonias sp.
Sphyraena sp.
Sarda sp.
Makaira cf. nigricans
Chilomycterus sp.

Mammals

Afrotheria


Genus	Species	Family	Stratigraphic Position	Notes	Images
Gomphotherium	G. calvertense^[4]	Gomphotheridae	Plum Point^[4]	Gomphotherium sp may be known from the Fairhaven member^[4]
Metaxytherium	M. crataegense^[2]	Dugongidae			M. crataegense skull
Nanosiren	N. sp^[2]	Dugongidae	Plum Point^[2]
Corystosiren	Aff. C. sp.^[2]	Dugongidae	Lower Calvert^[2]

Cynarctus marylandica
Tomarctus brevirostris
Gomphotherium calvertensis
Hipparion cf. phosphorum
Amphicyon cf. frendens
Amphicyon intermedius
Aphelops sp.
Archaeohippus cf. blackbergi

Cetaceans

Pinnipeds

Callophoca obscura
Leptophoca

Crocodilians

Thecachampsa antiquus
Thecachampsa sericodon

Invertebrates

Birds

References

1 2 Carnevale, Giorgio; Godfrey, Stephen James (2018). "Miocene bony fishes from the Calvert, Choptank, St. Marys and Eastover Formations, Chesapeake Group, Maryland and Virginia". Smithsonian Contributions to Paleobiology (100).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Godfrey, Stephen J., ed. (2018-09-25). "The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA". Smithsonian Contributions to Paleobiology (100): 2–274. doi:10.5479/si.1943-6688.100. ISSN 1943-6688.
↑ "Paleobiology Collections Search". collections.nmnh.si.edu. Retrieved 2020-08-14.
1 2 3 smithsonian.figshare.com. doi:10.5479/si.32085168 https://smithsonian.figshare.com/articles/book/The_Geology_and_Vertebrate_Paleontology_of_Calvert_Cliffs_Maryland_USA_Volume_3_Elephants_Land_Mammals_and_Seals/32085168. Retrieved 2026-08-15. {{cite web}}: Missing or empty |title= (help)

[:0-1] 1 2 Carnevale, Giorgio; Godfrey, Stephen James (2018). "Miocene bony fishes from the Calvert, Choptank, St. Marys and Eastover Formations, Chesapeake Group, Maryland and Virginia". Smithsonian Contributions to Paleobiology (100).

[:1-2] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Godfrey, Stephen J., ed. (2018-09-25). "The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA". Smithsonian Contributions to Paleobiology (100): 2–274. doi:10.5479/si.1943-6688.100. ISSN 1943-6688.

[3] "Paleobiology Collections Search". collections.nmnh.si.edu. Retrieved 2020-08-14.

[:2-4] 1 2 3 smithsonian.figshare.com. doi:10.5479/si.32085168 https://smithsonian.figshare.com/articles/book/The_Geology_and_Vertebrate_Paleontology_of_Calvert_Cliffs_Maryland_USA_Volume_3_Elephants_Land_Mammals_and_Seals/32085168. Retrieved 2026-08-15. {{cite web}}: Missing or empty |title= (help)

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