Fossil plants are extinct plants whose remains (referred to as plant fossils) are found preserved in sedimentary deposits. Plant fossils are classified using fossil-taxa as defined in the International Code of Nomenclature. Fossil-taxa differ conceptually from taxa of living plants in that they often do not refer to whole organisms, but to the remains of one or more parts of the parent organism, in one or more preservational states. There can be complications when two parts of a plant are shown to be connected, or when two preservational states are correlated, and to avoid disrupting the wider palaeobotanical taxonomy it is often best to keep the fossil-taxa separate. Extinct fossil plants reconstructed by piecing together the plant fossils are best not given formal
Linnean taxonomic names. There can also be problems using living plant taxa for fossils, even when there is a close morphological similarity of particular plant parts. Fossil-taxa for different plant parts can reflect different taxonomic ranks of the parent plants so care must be taken when using such taxa in floristic or phylogenetic studies. Because of taphonomic factors, a number of “artificial” fossil-taxa have proved useful, despite that they do not fully reflect the systematic positions of the parent plants.