Calvert Formation

Calvert Formation
Stratigraphic range: Early to Middle Miocene (Aquitanian-Langhian)
Outcrops of the Calvert Formation at the Calvert Cliffs State Park
TypeFormation
Unit ofChesapeake Group
UnderliesChoptank Formation
OverliesOld Church Formation
Location
RegionMaryland, Virginia, Delaware
CountryUnited States
Type section
Named forCalvert 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. It is one of the three formations which make up the Calvert Cliffs, all of which are part of the Chesapeake Group.

Fossils

Fossils from the Calvert Formation, Zone 10, Calvert Co., MD (Miocene)

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. Some of the fossil species represented include the following:

Chondrichthyes

Carcharocles megalodon partially buried in gravel along the Calvert Cliffs, Maryland

Holocephalians

Genus Species Family Location Stratigraphic Position Material Notes Images
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 Location Family Stratigraphic Position Material Notes Images
Notorynchus N. primigenius Hexanchidae Similar to extant N. cepedianus but differs in distribution.
Hexanchus H. gigas Hexanchidae Far less common then N. primigenus
Echinorhinus E. blakei Echinorhinidae Teeth and bramble thorns One of the rarest sharks in the cliffs, prefers deeper waters
Squalus Squalus sp. 1

Squalus sp. 2

 Squalidae Very rare Two forms of teeth, one (S. sp. 2) similar to Squalus acanthias
Squatina Squatina sp. Squatinidae Teeth and Dermal thorns
Rhincodon R. typus Rhincodontidae Very similar to modern R. typus
A living whale shark
Carcharias C. cuspidatus

C. taurus C. reticulatus

 Odontaspididae
Carcharoides C. catticus Lamnidae
Isurus I. oxyrinchus

I. retroflexus

 Lamnidae
Living Isurus oxyrinchus
Carcharodon C. hastalis

C. subserratus

 Lamnidae
Otodus O. chubutensis

O. megalodon

 Otodontidae
Parotodus P. benedenii incertae sedis
Alopias A. cf. vulpinus

A. cf. superciliosus A. grandis

 Alopiidae A second large species of Alopias is known from teeth with larger and coarser serrated cutting edges then A. grandis
Cetorhinus Cetorhinus sp. Cetorhinidae Known exclusively from vertebral centra Two species C. parvus and C. maximus are known from the time making identification difficult
Scyliorhinidae sp. Scyliorhinidae
Mustelus Mustelus sp. Triakidae A smooth-hound shark
Hemipristis H. serra Hemigaleidae Teeth and vertebra, a partial skeleton is held in private collection Teeth where found in association with a Squalodon skeleton, possibly from predation or scavenging
Reconstructed fossil jaw of the shark Hemipristis serra, Florida Museum of Natural History
Galeocerdo Galeocerdo aduncus Galeocerdonidae Teeth have two morphologies and it is unclear whether this is because of sexual dimorphism or both are produced by the same individuals
Physogaleus P. hemmooriensis
Carcharhinus C. cf. altimus

C. falciformis C. leucas C. macloti C. perezii C. priscus C. plumbeus

 Carcharhinidae Teeth distinctive to each species and indeterminate vertebral remains C. cf. altimus is known from teeth similar to modern bignose shark

Teeth from C. falciformis have been found in association with Squalidon remains

C. leucas teeth from the Calvert cliffs reach a maximum height of 18mm smaller then modern examples of the species
Negaprion N. eurybathrodon Carcharhinidae A lemon shark
Rhizoprionodon R. sp 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
Sphyrna Sphyrna laevissima An early hammerhead
Rays and other cartilaginous fish

Bony fish

Mammals

Afrotheria

Genus Species Family Location Stratigraphic Position Material Notes Images
Gomphotherium G.

calvertense

 Gomphotheridae Plum Point Gomphotherium sp may be known from the Fairhaven member
Metaxytherium M. crataegense Dugongidae
M. crataegense skull
Nanosiren N. sp Dugongidae Plum Point
Corystosiren Aff. C. sp. Dugongidae Lower Calvert

Cetaceans

Pinnipeds

Crocodilians

Invertebrates


Birds

See also

References

  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).
  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.
  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)