Dioscoreales contains the family Dioscoreaceae, which notably includes the yams (Dioscorea) and several other bulbous and tuberous plants, some of which are heavily cultivated as staple food sources in certain countries.

parts of Southern Africa), and have adapted to this harsh environment as caudex-forming, perennial caudiciformes, including Dioscorea elephantipes, the "elephant's foot" or "elephant-foot yam".

Synapomorphies include tuberous roots, glandular hairs, seed coat characteristics and the presence of calcium oxalate crystals.

[5] Other characteristics of the order include the presence of saponin steroids, annular vascular bundles that are found in both the stem and leaf.

Plants in Nartheciaceae show successive microsporogenesis which is one of the traits indicating that the family is sister to all the other members included in the order.

[15] The new phyletic approach changed the way that taxonomists considered plant classification, incorporating evolutionary information into their schemata, but this did little to further define the circumscription of Dioscoreaceae.

[20] In Dahlgren's third and final version (1985)[22] that broader circumscription of Dioscoreales was created within the superorder Lilianae, subclass Liliidae (monocotyledons), class Magnoliopsida (angiosperms) and comprised the seven families Dioscoreaceae, Petermanniaceae, Smilacaceae, Stemonaceae, Taccaceae, Trichopodaceae and Trilliaceae.

[9] The increasing availability of molecular phylogenetics methods in addition to morphological characteristics in the 1990s led to major reconsiderations of the relationships within the monocotyledons.

[24] In that large multi-institutional examination of the seed plants using the plastid gene rbcL the authors used Dahlgren's system as their basis, but followed Thorne (1992)[25] in altering the suffixes of the superorders from "-iflorae" to "-anae".

In APG II (2003),[27] a number of changes were made to Dioscoreales, as a result of an extensive study by Caddick and colleagues (2002),[5][28] using an analysis of three genes, rbcL, atpB and 18S rDNA, in addition to morphology.

Although further research on the deeper relationships within Dioscoreales continues,[30][31][23] the APG IV (2016) authors felt it was still premature to propose a restructuring of the order.

[32][1] Acorales Alismatales Petrosaviales Dioscoreales Pandanales Liliales Asparagales Arecales Poales Zingiberales Commelinales The data for the evolution of the order is collected from molecular analyses since there are no such fossils found.

It is estimated that Dioscoreales and its sister clade Pandanales split up around 121 million years ago during Early Cretaceous when the stem group was formed.

They are mainly tropical or subtropical representatives, but some members of families Dioscoreaceae and Nartheciaceae are found in cooler regions of Europe and North America.

Nartheciaceae on the other hand is a family composed of herbaceous plants with a rather lily-like appearance (Aletris) while Burmanniaceae is entirely myco-heterotrophic group.

Many members of Dioscoreaceae produce tuberous starchy roots (yams) which form staple foods in tropical regions.