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
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 FamilyLocationStratigraphic PositionMaterialNotes ImagesEdaphodon Edaphodon sp.Callorhynchidae two well preserved mandibular platesSimilar to E. sweetiIschyodusIschyodus sp.Callorhynchidae many tooth fragments occasional mandibular platesChimaeraChimaera sp.Chimaeridae
Elasmobranchii +GenusSpeciesLocationFamilyStratigraphic PositionMaterialNotesImagesNotorynchusN. primigeniusHexanchidaeSimilar to extant N. cepedianus but differs in distribution.Hexanchus H. gigasHexanchidaeFar less common then N. primigenusEchinorhinusE. blakeiEchinorhinidaeTeeth and bramble thornsOne of the rarest sharks in the cliffs, prefers deeper watersSqualusSqualus sp. 1 Squalus sp. 2SqualidaeVery rareTwo forms of teeth, one (S. sp. 2) similar to Squalus acanthiasSquatinaSquatina sp.SquatinidaeTeeth and Dermal thornsRhincodonR. typusRhincodontidaeVery similar to modern R. typusCarchariasC. cuspidatus C. taurus C. reticulatusOdontaspididae CarcharoidesC. catticusLamnidaeIsurusI. oxyrinchus I. retroflexusLamnidaeCarcharodonC. hastalis C. subserratusLamnidaeOtodusO. chubutensis O. megalodonOtodontidaeParotodus P. benedeniiincertae sedisAlopiasA. cf. vulpinus A. cf. superciliosus A. grandisAlopiidaeA second large species of Alopias is known from teeth with larger and coarser serrated cutting edges then A. grandisCetorhinusCetorhinus sp.CetorhinidaeKnown exclusively from vertebral centraTwo species C. parvus and C. maximus are known from the time making identification difficultScyliorhinidae sp.Scyliorhinidae MustelusMustelus sp.TriakidaeA smooth-hound sharkHemipristisH. serraHemigaleidaeTeeth and vertebra, a partial skeleton is held in private collectionTeeth where found in association with a Squalodon skeleton, possibly from predation or scavengingGaleocerdo Galeocerdo aduncusGaleocerdonidaeTeeth have two morphologies and it is unclear whether this is because of sexual dimorphism or both are produced by the same individualsPhysogaleusP. hemmooriensisCarcharhinus C. cf. altimus C. falciformis C. leucas C. macloti C. perezii C. priscus C. plumbeusCarcharhinidaeTeeth distinctive to each species and indeterminate vertebral remainsC. 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 speciesNegaprionN. eurybathrodon CarcharhinidaeA lemon sharkRhizoprionodonR. spCarcharhinidaeFormerly assigned to R. ficheuri due to similarity of teeth but due to high endemism in modern genus this is probably not the caseSphyrnaSphyrna laevissimaAn 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 FamilyLocationStratigraphic PositionMaterialNotes ImagesGomphotheriumG. calvertenseGomphotheridaePlum PointGomphotherium sp may be known from the Fairhaven memberMetaxytherium M. crataegense DugongidaeNanosirenN. spDugongidaePlum PointCorystosirenAff. C. sp.DugongidaeLower 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
Callophoca obscura Leptophoca
Crocodilians
Thecachampsa antiquus Thecachampsa sericodon
Invertebrates
Chesapecten nefrens Chesapecten coccymelus Isognomon sp. Ecphora Architectonica trilineata
Birds
Mergus miscellus Morus loxostylus Calonectris kurodai Heliadornis ashbyi Miocepphus Pelagornis
See also
List of fossiliferous stratigraphic units in Virginia Paleontology in Virginia Paleontology in Maryland Calvert Cliffs State Park List of fossiliferous stratigraphic units in Maryland Chesapeake Group
References