Calvert Formation
Geologic formation in the United States
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.
01Fossils
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
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 | ||||
| Carcharias | C. cuspidatus | Odontaspididae | |||||
| Carcharoides | C. catticus | Lamnidae | |||||
| Isurus | I. oxyrinchus
I. retroflexus |
Lamnidae | |||||
| Carcharodon | C. hastalis
C. subserratus |
Lamnidae | |||||
| Otodus | O. chubutensis | Otodontidae | |||||
| Parotodus | P. benedenii | incertae sedis | |||||
| Alopias | A. cf. vulpinus | 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 | |||
| 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
- Mobula pectinata
- Mobula fragilis
- Mobula loupianensis
- Plinthicus stenodon
- Rhinoptera cf. R. studeri
- Aetobatus arcuatus
- Pteromylaeus sp.
- Dasyatis probsti
- Dasyatis rugosa
- Pristis sp.
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 | 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 | |||||
| Nanosiren | N. sp | Dugongidae | Plum Point | ||||
| Corystosiren | Aff. C. sp. | Dugongidae | Lower Calvert |
- Cynarctus marylandica
- Tomarctus brevirostris
- Gomphotherium calvertensis
- Hipparion cf. phosphorum
- Amphicyon cf. frendens
- Amphicyon intermedius
- Aphelops sp.
- Archaeohippus cf. blackbergi
Cetaceans
- Atlanticetus patulus
- Squalodon calvertensis
- Eurhinodelphis sp.
- Parietobalaena palmeri
- Eobalaenoptera harrisoni
- Cephalotrophis coronatus
- Araeodelphis
- Cetotherium
- Zarhachis flagellator
- Pelocetus
- Xiphiacetus
Pinnipeds
Crocodilians
- Thecachampsa antiquus
- Thecachampsa sericodon
Invertebrates
- Chesapecten nefrens
- Chesapecten coccymelus
- Isognomon sp.
- Ecphora
- Architectonica trilineata
Birds
Sources and credits
This article is adapted from the Wikipedia article “Calvert Formation”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- 2016-07-20 10 17 03 Cliffs to the south of Grays Creek in Calvert Cliffs State Park, Calvert County, Maryland.jpg by Famartin, CC BY-SA 4.0
- Calvert Zone 10 Calvert Co MD 2.jpg by Wilson44691, CC0
- Meg in gravel.jpg by Mason Hintermeister, CC BY-SA 4.0
- Rhincodon typus fgbnms.jpg by FGBNMS/Eckert, Public domain
- Isurus oxyrinchus by mark conlin3.jpg by Mark Conlin, SWFSC Large Pelagics Program, Public domain
- Hemipristis serra FLMNH.jpg by Geekgecko, CC BY 4.0
- Knight Gomphotherium.jpg by Charles Robert Knight, Public domain
- Metaxytherium crataegense FLMNH.jpg by Geekgecko, CC BY 4.0
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