Medullosales, Callistophytales and Peltaspermales. Their discovery attracted considerable attention at the time, as the pteridosperms were the first extinct group of vascular plants to be identified solely from the fossil record. In the 19th century the Carboniferous Period was often referred to as the "Age of Ferns" but these discoveries during the first decade of the 20th century made it clear that the "Age of Pteridosperms" was perhaps a better description. During the 20th century the concept of pteridosperms was expanded to include various Mesozoic groups of seed plants with fern-like fronds, such as the Corystospermaceae. Some palaeobotanists also included seed plant groups with entire leaves such as the Glossopteridales and Gigantopteridales, which was stretching the concept. In the context of modern phylogenetic models, the groups often referred to as pteridosperms appear to be liberally spread across a range of clades, and many palaeobotanists today would regard pteridosperms as little more than a paraphyletic 'grade-group' with no common lineage. One of the few characters that may unify the group is that the ovules were borne in a cupule, a group of enclosing branches, but this has not been confirmed for all "pteridosperm" groups. Phylogeny An alternative phylogeny of spermatophytes based on the work by Novíkov & Barabaš-Krasni 2015 with plant taxon authors from Anderson, Anderson & Cleal 2007 showing the relationship of extinct clades. Taxonomy Family ?†Nystroemiaceae Wang & Pfefferkorn 2009 Order ?†Alexiales Anderson & Anderson (2003) Family †Alexiaceae Anderson & Anderson (2003) Order ?†Calamopityales Němejc (1963) [Buteoxylales Taylor & Taylor (1992)] Family †Calamopityaceae (Solm. (1896)) Scott (1909) [Buteoxylaceae Barnard & Long (1973); Stenomyelaceae Scott (1923)] Order ?†Erdtmanithecales Friis and Pedersen (1996) Family †Erdtmanithecaceae Friis and Pedersen (1996) Order ?†Hlatimbiales Anderson & Anderson (2003) Family †Hlatimbiaceae Anderson & Anderson (2003) Order †Umkomasiales Doweld (2001) [Corystospermales; Ptilozamitales (Němejc 1950)] Family †Angaropeltidaceae Doweld (2001) [Cardiolepidaceae Meyen 1977] Family †Umkomasiaceae Petriella (1981) (Corystospermaceae (Thomas (1933)) Stockey & Rothwel nom. illeg.; Zuberiaceae Němejc (1968); Pachypteridaceae de Zigno; Ptilozamitaceae Němejc (1950)] Class ?†Arberiopsida Doweld (2001) [Clealopsida; Dicranophyllopsida Němejc 1968] Order †Dicranophyllales Meyen (1984) emend. Anderson, Anderson & Cleal (2007) Family †Dicranophyllaceae Němejc (1959) ex Archangelsky & Cúneo (1990) Order †Aberiales Meyen (1978) ex Meyen (1984) Family †Schmeissneriaceae Zhou (1997) Family †Arberiaceae (Rigby (1972) Anderson & Anderson (1985) Class †Moresnetiopsida Doweld (2001) [Moresnetiophyta Doweld (2001); Elkinsiophytina] Order †Tetrastichiales Němejc (1968) Family †Tetrastichiaceae Němejc (1968) Order †Pullarithecales Doweld (1998) Family †Gnetopsidaceae Doweld (2001) Family †Pullarithecaceae Doweld (1998