I've been reading again papers on fossil Sphenophytes since a few months now, and one strange thing i've noticed is the relationship between the genus Equisetum and Equisetites.
While the wide array of species attributed to the later clearly represents an heterogenous group, some of them (especially the mid-late Mesozoic examples) seem to resemble a lot the modern genus, to such an extent that several papers directly attribute some species (E. columnare, E. lateral) to Equisetum and describe Equisetites as being pretty much indistinguishable from the Holocene genus.
Meanwhile, other papers adopt a seemingly more conservative approach, essentially attributing all species to Equisetites on the simple basis of their Mesozoic age.
This brings sort of a question ; would it be wiser to attribute some of the clearly related species to the genus Equisetum, thus possibly better reflecting real-life affinities but taking the risk of conflating unrelated clades, or to keep them in Equisetites, avoiding such problems but keeping them in wastebasket taxon hell ?
Hello Ellio
I think your question is a fundamental one, but not that important.
As long as we are convinced of biological evolution we understand that a new species arises from another species, which preexisted, just as does a new genus. Natura not facit saltum as already said Linné (on a fixist background, but that's another story). The question of the limits is clearly fundamental.
When dealing with fossils, i.e. having acces (almost) only to morpho-anatomical features we cannot explore this question in deep, we are condamned to deal with appearances only. So Equisetites or Equisetum is not that important, as long as we remember that a fossil cannot be safely assigned to a extant taxon, at least for Pleistocene or older times.
It might more commiting to use our brain time to think to what this fossils tell us or not, isn't it?
Lo que pasa es que Equisetites es el nombre genérico del fósil.
Y Equisetum es el nombre genérico de la planta actual .los dos son muy similares y se supone que no son idénticos, pues hay diferencia de miles o millones de años de acuerdo a la edad del fósil encontrado.
The name Equisetites was introduced by Sternberg (1833) mainly for fossil-species of stems and rhiozomes (mainly of Mesozoic age) that resemble Equisetum but for which reproductive structures are unknown. As far as I am aware (I am a Palaeozoic rather than a Mesozoic palaeobotanist!) this is how the name is still used today. The type is taken as Equisetites muensteri Stbg following Harris (1931).
There is a problem, however. Although Sternberg in his discussion suggested that he was using Equisetites for such ambiguous Equisetum-like stems and rhizomes, in his systematic treatment he stated that he did in fact have strobili for one species, E. muensteri. Sternberg also mentioned what seem to be strobili in the generic diagnosis ("Spica globosa"). This seems to have been based on Sternberg's pl. 16 fig, 5, but this is far from clear from the figures, and as far as I am aware the specimen has never been restudied or refigured.
The situation is clearly ambiguous, but as I have said, Equisetites is normally used today for fossil stems and rhizomes that are similar to the living plant Equisetum, but for which strobili are unknown. They may well have come form an extinct plant that, if you saw it living, you would assign to Equisetum, but you cannot be sure.
There have been too many cases in the past where plant fossils seem at first to resemble a modern-day, living taxon and have been named as such. And then as we get to know the fossils better we see that the resemblance is superficial. This is why we now use fossil-taxa (as defined in the Code) for fossilised remains of particular parts of plants, in different modes of preservation and at different life-history stages.
I realise that many botanists (and even palaeobotanists) do not understand fully how fossil-taxa work. I have attached paper that Barry Thomas and I recently published on some of the issues.
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