Caytoniales

Caytoniales is an extinct order of seed plants traditionally regarded as gymnosperms. They lived from the Late Permian to the Middle Triassic, roughly 260 to 235 million years ago, and include several genera, with Caytonia being the best known.

The most distinctive feature of Caytoniales is the cupule, a protective structure formed from modified leaf bases that surrounds one or more seeds (ovules). Seeds were often arranged in clusters or on short stalks beneath the cupule, producing an enclosed reproductive unit that superficially resembles a flower or an ovary in angiosperms. This cupulate organization has made Caytoniales central to discussions about the origins of angiosperms, though they are not considered direct ancestors of flowering plants, and their precise phylogenetic position among seed plants remains debated.

Anatomy and leaf impressions indicate a suite of gymnosperm traits, including tracheid-based wood, and the group likely exhibited a range of growth forms from smaller herbaceous to more woody plants. The morphology of Caytoniales suggests diverse leafy and reproductive structures, but the best data come from preserved reproductive organs.

Fossil records are found in Eurasia and North America, consistent with Permian–Triassic ecosystems. The Caytoniales are frequently cited in paleobotanical studies as a possible evolutionary intermediate between earlier seed plants and more derived gymnosperms, and as part of the broader discussion on the evolution of seed-enclosing structures.

See also: Gymnosperms, Bennettitales, Angiosperm evolution.