Angiosperms are almost everywhere. Around 90% of plant species are angiosperms, flowering plants. There are way more species of angiosperm than they have ever been of the other groups of land plants. Despite this success, they’re relative late-comers. In the fossil record, they only seem to get going around the end of the Jurassic or start of the Cretaceous periods, when they co-evolved with their pollinators and herbivores. That means we should expect flowers to be no older than 150 million years.

That would be fine except that when you build a ‘molecular clock’, by tracking the time it would take for differences in the genetic make-up to build up between angiosperms and their closest relatives, the gymnosperms, you get a different answer. Up to 300 million years. Effectively the molecular studies put the origin of flowering plants twice as far back. Two papers have come out recently independently tackling this discrepancy.

Constraining uncertainty in the timescale of angiosperm evolution and the veracity of a Cretaceous Terrestrial Revolution by Barba-Montoya et al., attempts to improve the molecular clock by using fossil calibration to fix certain points on the scale. They can then use Bayesian statistics to set a date range for the first angiosperms.