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Number of species[edit]

This page should say how many species of rhyniophytes there are. --Savant13 14:02, 21 December 2006 (UTC)

Devonian radiation?[edit]

The following paper gives the impression I'm familiar with that the radiation occurred during the late Silurian. Indeed, Cooksonia is a rhyniophyte, and is known from the Wenlock (Silurian).

Kenrick, P.; Crane, P.R. (1997). "The origin and early evolution of plants on land" (PDF). Nature 389 (6646): 33. 

I think the problem is that there are two meanings of "radiation" (1) diversification of clades (2) rise in numbers to achieve "dominance". While there is strong circumstantial evidence that the major vascular plant clades had evolved prior to the Devonian, there is little evidence they had risen to dominance.
In any case, Kenrick & Crane's book makes it clear that there are no known fossils of Rhyniophyta prior to the Devonian. They exclude Cooksonia from the Rhyniophyta because it is not a coherent taxon; many fossils of Cooksonia do not have vascular tissue, and none of them belong to the Rhyniophyta in their analysis of the fossils. --EncycloPetey 18:46, 7 November 2007 (UTC)

I see. I didn't have the book to hand but in the paper, they do include Cooksonia as a rhyniophyte; I'm pretty sure there are Siluian "rhyniophytes" but this may be an issue of semantics. As you say, I suppose the issue is what we decide to call a radiation. I've just been looking at a recent paper (below) which has an interesting graph of "mean axis diameter vs. time" which does seem to agree that a drastic stemmed-organism rise occurred in the Pragnian; it may be worth clarifying in the article that that's to what you refer. Verisimilus T 19:01, 7 November 2007 (UTC)
Clack, J. A. 2007. Devonian climate change, breathing, and the origin of the tetrapod stem group. Integrative and Comparative Biology 47, 510-523
When you say "stemmed-organism" do you mean taxa belonging to the "stem taxon" or "plants with stems"? Remember that recent studies (by Kenrick in particular) show that some of the fossils previously believed to be vascular plants are actually upright bryophytes that lack xylem (defined by having lignin and the mature wall patterning of xylem), and instead have hydroids (a conducting tissue known today only among bryophytes). --EncycloPetey 19:07, 7 November 2007 (UTC)
The graph shows a rapid increase in mean axis diameter during the Pragnian, which I'd taken to mean that plants with stems (but not necessarily vascularised stems) were becoming larger/more abundant. Thanks for pointing out the recent Kenrick work, that sounds worth reading; I'll take a look! Verisimilus T 09:17, 8 November 2007 (UTC)

"Class" rank in taxobox[edit]

As much as I know, Rhyniophytes are divided into three classes: Rhyniopsida, Zosterophytopsida and Horneophytopsida; so I am not sure if we should include "Classis" rank in the taxobox as it is included right now. Maybe we should make subpages for classes or smth? Klon-immortal 13:57, 8 November 2007 (UTC)

Please check the cited references (both by Kenrick & Crane) and other recent references. The Zosterophyllopsida and Horneophytopsida are not in the same clade. The zosterophylls are sister to the Lycopodiophyta and the Horneophytopsida are not vascular plants. The Rhyniophyta sensu Banks and others has been dismantled as a result of more careful morphological analysis of the fossils. So the Rhyniophyta classes are actually three clades in a paraphyletic basal assemblage of polysoprangiates. (See the cladogram on the Plant article.) --EncycloPetey 14:05, 8 November 2007 (UTC)

Image of Agalophyton[edit]


I see that an image of Agalophyton has been added and removed from this article. Its overall morphology is similar to that of the Rhyniophytes; would it perhaps be better to include the image with a caption detailing the caveats, so that people unfamiliar with the topic at least get an idea of what the plant looked like?

Verisimilus T 15:52, 28 November 2007 (UTC)

No, because it doesn't belong to this group. That would be like adding a conifer picture to illustrate a page on angiosperms, or using an amphibian to illustrate an article on reptiles. Aglaophyton is a non-vascular plant; the rhyniophytes are vascular plants. --EncycloPetey (talk) 16:16, 28 November 2007 (UTC)
(Addendum) In any case, the recent reconstructions I've seen for Rhynia don't look like Aglaophyton at all. --EncycloPetey (talk) 16:50, 28 November 2007 (UTC)
Okay. My point was that you can't tell from the outer morphology whether or not a plant is vascular; in my hazy memory the two looked similar enough for the picture to be of passing help. Clearly not - thanks for clarifying! Verisimilus T 19:11, 28 November 2007 (UTC)

What mosses evolved from...?[edit]

We are tought in university that Rhyniophyta are ancestors not only of vascular plants, but of mosses too... We are tought that mosses evolved because of reduction of sporophyte and progress of gametophyte. As I see from the cladogram in this article, it's not true? Or it's not clear yet? Vikte (talk) 21:58, 29 March 2008 (UTC)

That hypothesis has been around for a long time, but it has not been supported by any research. All recent studies indicate that vascular plants are a monophyletic group, and the bryophytes are an ancestral assemblage from which the vascular plants evolved. There are no recent studies that support the evolution of bryophytes from a rhyniophyte ancestor. --EncycloPetey (talk) 22:26, 29 March 2008 (UTC)

Article title[edit]

As noted above, the original "Rhyniophyta" of Banks has been discredited; the Rhyniopsida are not within the Rhyniophyta in recent cladistic analyses. So (1) the article as of 29 Jan 2011 is out of date (2) the title is wrong: it would be better as Rhyniopsida with a brief comment on the former classification. I proposed to make these changes. Peter coxhead (talk) 17:28, 29 January 2011 (UTC)