Taxacom: "Early Permian" angiosperms... real or not real taxa/names?

[John Grehan]

All of the latest comments by Tony just go to show how tricky some aspects
of the fossil record can be, especially when a fossil may be interpreted
according to what kind of ancestral model one has in mind. Heck - if there
is no clear cut difference between an inflorescence and a flower in living
angiosperms, how can anyone be certain about anything ancestral? But
fossils are not the only form of evidence for the age of taxa. Take for
example the distribution of  the angiosperm genus Dianella. Its western
boundary lies on the Mwenetzi monocline which formed along the split
between Africa and Antarctica beginning about 185 Ma. This puts the
existence of this genus well into the Jurassic. The Lebombo-Mwenetzi
monocline has also been found to be correlated with differentiation between
the subfamilies Rutoideae and Aurantioideae (Rutaceae) (Heads 2012: fig.
9-2), between the Vepris-Flindersia and Diosmeae-Galipeeae clades of
Rutaceae (Heads 2012: fig. 9-3), and between Canellaceae and Winteraceae
(Heads 2012: fig. 9.5). So from the biogeography alone it is evident that
'crown' angiosperms were in existence by the late Jurassic - never mind
what the fossil record should or should not say about this.

Cheers, John Grehan

On Sat, Jun 4, 2022 at 4:10 PM Tony Rees <tonyrees49 at gmail.com> wrote:

> Dear all, I have done a bit more digging regarding the early angiosperm
> fossil record - as mentioned earlier, I am by no means a specialist in this
> area, but do have a few paleobotany books on my shelf for reference/general
> interest (plus a botanical degree from many years ago now...).
>
> Apart from the evidence/hypotheses/indications based on rates of molecular
> evolution, D. Silvestro et al., 2021. "Fossil data support a pre-Cretaceous
> origin of flowering plants", Nature Ecology & Evolution 5: 449-457,
> presented back-calculations indicating that, 198 angiosperm clades (APG IV
> families) "several families [of angiosperms: namely Lardizabalaceae,
> Papaveraceae and Triuridaceae] with living descendants originated in the
> Jurassic". However, in a response to this paper published as yet only on
> bioRxiv, G.E. Budd et al., (2021, "Fossil data do not support a long
> pre-Cretaceous history of flowering plants", doi 10.1101/2021.02.16.431478)
> dispute Silvestro et al's methodology and state: "their results are
> entirely compatible with an origin of angiosperms in the Cretaceous", and
> further, "If we take the results of Silvestro et al. at face value, they
> imply that many eudicot lineages (united by their distinctive tricolpate
> pollen, modified into tricolporate and triporate within the clade) extend
> deep into the Jurassic. This would conflict strongly with the sequential
> appearance of monosulcate, tricolpate and tricolporate pollen in the
> Cretaceous dispersed pollen record, which represents a vastly broader
> stratigraphic and geographic sample of the world’s past vegetation than the
> record of other plant parts", which is a point I have alluded to earlier:
> especially since the fossil record of Cretaceous, Jurassic, Triassic and
> even Permian pollen and spores is by now extremely well documented.
>
> Nevertheless, a few "modern" claims of pre-Cretaceous angiosperm fossils
> have continued to surface. Persons interested in this area may have come
> across Archaefructus Sun, Dilcher, Zheng & Zhou, 1998 (Science 282:
> 1692-1695), described as from the Upper Jurassic of China, however later
> re-dated to Early Cretaceous (c.125 million years old). More recently,
> Nanjinganthus Fu et al., 2018 has been described as an Early Jurassic
> fossil angiosperm from China, however its claimed angiosperm affinities
> have been disputed by others, e.g. Coiro et al., 2018 who believe that the
> fossils represent a conifer (ref/s on Wikipedia and elsewhere). Most
> recently, Florigerminis Cui et al., 2022 has been described from
> the Middle–Late Jurassic Jiulongshan Formation of Inner Mongolia, although
> there have been suggestions in the past (refuted by Cui et al.) that this
> formation is Early Cretaceous; this report is too new to have yet been
> assessed by other works in the field.
>
> Other than Florigerminis as above, the oldest other "accepted" angiosperm
> fossil, along with Archaefructus, appears currently to be Montsechia
> vidalii (Zeiller) Teixeira from the Barremian (in other words, not even the
> earliest Cretaceous, with the Hauterivian, Valanginian, and Berriasian
> preceding it), as more fully described by Gomez et al, 2015, "Montsechia,
> an ancient aquatic angiosperm", PNAS 112(35) 10985-10988,
> doi: 10.1073/pnas.1509241112. This genus is considered by Gomez et al. to
> be a representative of a new, extinct family of its own, basal in the
> Ceratophyllales, although historically even this plant has not always been
> considered to be an angiosperm on account of its unusual appearance, being
> placed by previous workers in liverworts, horsetails, conifers, and
> Gnetales before its angiosperm features were established (refer Gomez et
> al. refs 9 through 12).
>
> All the above is just supporting information, which nonetheless does
> indicate to me that a degree of skepticism should apply to Wachtler's
> claims of well-developed angiosperm flowers in the Early Permian. Unless
> other opinions are forthcoming, my present inclination is to accept the
> dating of the sediments from which Wachtler's fossils have been extracted
> (which do seem to be corroborated elsewhere, however with a more
> conventional "gymnosperm" flora), but treat his taxonomic assignment as
> questionable, for example to assign his genus names to Spermatophytina
> incertae sedis in my system (thus not placed explicitly in either
> Angiospermae or Gymnospermae), as accepted taxa at this time (thus not
> nomina dubia or taxa inquirenda, which are alternative available options);
> or indeed, perhaps "taxon inquirendum" would most applicable. All further
> thoughts welcome!
>
> Regards - Tony
>