The age of flowering plants is unknown

Abstract

The origin of flowering plants (angiosperms) was one of the most transformative events in the history of our planet. Despite considerable interest from multiple research fields, numerous questions remain, including the age of the group as a whole. Recent studies have reported a perplexing range of estimates for the crown-group age of angiosperms, from ca. 140 Ma (Early Cretaceous) to 270 Ma (Permian). Both ends of the spectrum are now supported by both quantitative analyses of the fossil record and fossil-calibrated molecular dating analyses. Here, we first clarify and distinguish among the three ages of angiosperms: the age of their divergence with acrogymnosperms (stem age), the age(s) of emergence of their unique, distinctive features including flowers (morphological age), and the age of the most recent common ancestor of all their living species (crown age). We then demonstrate, based on recent studies, that fossil-calibrated molecular dating estimates of the crown-group age of angiosperms have little to do with either the amount of molecular data or the number of internal fossil calibrations included. Instead, we argue that this age is almost entirely conditioned by its own prior. Lastly, we discuss which future discoveries or novel types of analyses are most likely to bring more definitive answers. In the meantime, we propose that the age of angiosperms is best described as unknown (140–270 Ma) and that future work that depends on the time scale of flowering plant diversification be designed to integrate over this vexing uncertainty.

The Angiosperm Terrestrial Revolution and the origins of modern biodiversity

“…The origins of flower characters are widely debated (Sauquet et al, 2022). Bisexual reproductive structures superficially similar to flowers evolved independently in Bennettitales, as did a form of Table 2 List of angiosperm key innovations, which presumably played a central role in their extraordinary diversification and rise to ecological dominance (see also Fig.…”

“…The origins of flower characters are widely debated (Sauquet et al ., 2022). Bisexual reproductive structures superficially similar to flowers evolved independently in Bennettitales, as did a form of double fertilization in Gnetales, but angiosperms have both, giving them huge advantages.…”

Trait-dependent diversification in angiosperms: patterns, models and data

“…Angiosperms form a clade of more than 350,000 extant species, despite their relatively young age of a 140 to 270 million years (Crepet & Niklas, 2009; Foster et al, 2017; Li et al, 2019; Magallón et al, 2015; Sauquet et al, 2021; Silvestro et al, 2021). Almost all of terrestrial life is linked, directly or indirectly to angiosperms (Benton et al, 2021) and their success makes them an ideal study group for uncovering the intrinsic traits and extrinsic factors driving their diversification.…”

Case not closed: the mystery of the origin of the carpel

“…To reconstruct the structure that preceded the carpel (also referred to as the ancestor of the carpel, not to be confused with the ancestral or original carpel) it is useful to know at which point in the stem lineage of the angiosperms that structure appeared and what the closest relatives to that point are. There are several reasons why these questions remain some of the biggest mysteries of plant evolution, namely, the great morphological gap between the carpel and the reproductive structures of their closest living relatives [ 11 , 12 ]. In addition, important gaps in the fossil record of early angiosperms means the relationships within its stem lineage and between extant angiosperms and extant gymnosperms remain inconclusive [ 13 , 14 ].…”

“…Corystosperms fossils have a central axis on which fertile branches are helically arranged, each producing a seed-bearing cupule. Although some analysis group these and other cupule producing fossils, including Caytonia, under the same umbrella of morphological traits [ 16 ], most current studies group Corystosperms within gymnosperms, close to Cycadales [ 7 , 11 ] (Fig. 1 B).…”