Casts are sediment-infillings that completely fill the space where a biologic structure used to be.  Many plant fossils, such as tree roots and tree trunks, are preserved as casts.


Eospermatopsis tree trunk cast from the Ithaca Formation (lower Upper Devonian) at Riverside Quarry, Gilboa, southern Schoharie County, southeastern New York State, USA (FMNH P21740, Field Museum of Natural History, Chicago, Illinois, USA).  This taxon has erroneously been called the oldest seed fern.  Its botanical identity is undetermined, but it has been suggested to be the trunk of Aneurophyton, a progymnosperm or a non-progymnosperm.



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