A Primula from the Miocene - P. riosiae

The Miocene is a geological period extending from 23 million to 5.3 million years ago. It is during this time period that the apes arose and humans split to become their own lineage, open grasslands became more prominent and by the end of it almost 95% of modern seed plant families existed.

 

Evolutionary studies about our own primitive human ancestors makes the news with each exciting discovery, but behind the scenes, the evolution of the Primulaceae is also the focus of ongoing studies. Though genetic studies help us understand the relationships between species, other characteristics, such as seed morphology can be used to help differentiate plant species and to group related species. These days imaging seeds is easily done with clear results. See my Blog post Bringing Seeds into Focus.

 

Seeds are a goods means of exchanging plant material with like-minded enthusiasts worldwide. Many plant societies offer seed exchanges for their members including the American Primrose Society, Scottish Rock Garden Club, Alpine Garden Society and North American Rock Garden Society which all list Primula in their seed lists. But those are seeds of plants growing today. What would a Primula look like growing in the Miocene?

Primula riosiae from the original description

That is in part what Primula evolutionary studies hope to uncover but we can peek into the past and seed what a Primula seed looked like. The image above is the result of a Paleocarpological study done from samples collected in a lignite mine at Berzdorf, Germany which were dated to the lower and upper Miocene. Three seeds were found and they were then described by Alexander Czaja as a new species called Primula riosiae after Mrs. Anabel Rios in a paper titled "Paläokarpologische Untersuchungen von Taphozönosen des Unter- und Mittelmiozäns aus dem Braunkohlentagebau Berzdorf/Oberlausitz (Sachsen)" published in Palaeontographica Abteilung B Band 265 Lieferung 1-6 (2003), p. 49. The description is brief, but it is noted that the seed shows cells on the surface characteristic of many modern Primula seeds and that the seed bears a resemblance to Primula ruprechtii Kusn., which is considered a synonym of Primula elatior. Two recent papers which have used P. riosiae in their studies are : "Heterostyly accelerates diversification via reduced extinction in primrose" by de Vos et. al. and "Phylogeny and biogeography of Primula sect. Armerina: implications for plant evolution under climate change and the uplift of the Qinghai-Tibet Plateau" by Ren et. al.