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The Zone 10 MaterialThe specimens below are illustrative of Zone 10 material. Hot spots in the photos go to additional photos, drawings and names of each species. Where there are rulers without numbers, the units are millimeters. |
As is obvious from the specimens, some layers of the Calvert Formation are shells with a little sand filling the cavities. The material is loosely consolidated and the specimens illustrated have all been stabilized with glue. The number of species can be significant. In the first piece there are thirteen bivalves, twelve gastropods, and one species each from hydrozoa, bryozoa, condrichthyes (sharks in the form of a tooth), and maxillapoda (barnacles). Heres is the list of species in this first specimen. |
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Bivalves |
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Anadara subrostrata |
Astarte cuniformis |
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There are several Astarte species in Zone10 including A. parma, A.vicina, and A. cuniformis.
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Astarte vicina |
Astarte parma |
Cardita granutata |
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Chlamys madisonius |
Corbula idonea |
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Corbula inaequalis |
Glycymeris parlis |
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This species is only present in the lower portion of the Calvert formation. |
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Isognomon maxillata |
Maracrassatella melinus |
Mercenaria rileyi |
Stewartia anodonta |
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Dosinia sp. |
Carditamera arata |
Venus mercenaria |
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Clorbula elevata |
Lirophora latilirata (Venus clam) |
Tellina producta |
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Gastropods |
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Chrysodomus patuentensis |
Crucibulum pileolum and costatum |
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These specimens are 1 cm in length. |
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Cylichna calvertensis |
Polinices heros |
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These tiny snails are very common. I sift the sand remaining after excavating larger specimens to find them. |
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Drilla pseudebunea |
Nisa lineate |
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Siphonalia devexa |
Turritella indentata |
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Turretilla plebia |
Turretilla variabilis |
Vermetus virginicus |
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These turritella species are very common in Zone 10. Having said that, T. indenta is less common than T. plebia or T. variabilis T. variabilis has been divided into several varities but I've made no attempt to distinquish them here. |
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Typhis acuticosta |
Ecphora tricostata |
Xenophora conchliophora |
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This genus is extant along the southern Atlantic coast in the U.S. What is unique about this specimen is the small stones the animal used to camouflage itself are still present. Usually the camouflage is lost on fossils. In this instance the size of the pebbles increase as the animal grew.
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Siphonalia sp. |
Busycon spiniger |
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Fissuridea marylandica |
Pleurotoma bellacrenata |
Epitonium pachpleuro |
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Calliostoma virginicum |
Terebra curvilineata v. calvertensis |
Scaphella solidaria |
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Scaphopoda |
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Dentalium attenuatum |
Dentalium caduloide |
Cadulus thallus |
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Hydrazoa |
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Hydractinia multispinosa |
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A paper (http://decapoda.nhm.org/pdfs/33728/33728.pdf) says that the presence of this hydrazoa is indicative of the presence of hermit crabs. This species is very common in Zone 10. |
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Vertebrates |
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Sharks |
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Bryozoa |
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| This is not a piece I found but is from the North Museum of Science and Natural History in Lancaster, PA. I came across this bryozoan encruting a scallop shell in the Plum Point collection while entering specimens in a digital database. It seems to be a new species of bryozoan. | The genus is Schizoporella. These other specimens are a result of looking for another example of the bryozoan to confirms the location and strata. If you have a similar specimen from Zone 10 of the Calvert Formation, please contact me. | |||||||
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List of species in the first specimen:
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