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Fossil Friday: Is Triassic Angiosperm-Like Pollen a Solution to Darwin’s Abominable Mystery?

Photo: Angiosperm-like pollen Type I from the Middle Triassic of Switzerland, modified after Hochuli & Feist-Burkhardt 2013 in Frontiers, CC BY 4.0.

In a series of articles (Bechly 2021b2021c2021d2021e2022a) and podcasts (Bechly 2021a) I have thoroughly discussed Darwin’s abominable mystery of the abrupt appearance of flowering plants in the Early Cretaceous. I also showed that all alleged pre-Cretaceous fossils of flowering plants have been refuted by experts (Sokoloff et al. 2019Bateman 2020) as misidentified gymnosperms.

However, there is one remaining issue to address, which is palynology, the science of fossil pollen. Despite their tiny size, plant pollen are extremely durable and well-represented as microfossils throughout the Phanerozoic fossil record, even in sediments that otherwise lack any discernible fossils. Some scientists have described fossil pollen from the Triassic period (252-201 million years ago), which have unique angiosperm characteristics such as a single furrow (monosulcate) and a reticulate-columellar sculpture (Pocock & Vasanthy 1988Cornet 1989bZavada 1990, Doyle & Hotton 1991, Hochuli & Feist-Burkhardt 20042013). This Fossil Friday features microphotographs of angiosperm-like pollen of type 1 from the Middle Triassic of Switzerland (Hochuli & Feist-Burkhardt 2013). These angiosperm-like pollen have been interpreted by some as evidence for a much earlier origin of flowering plants, and you can also find this claim in media reports (Palmer 1994Anderson 2013University of Zurich 2013). Even some creationists have uncritically embraced these claims (Thomas & Clarey 2013), because they erroneously believed that it supports their young earth scenario. However, do these claims really hold water at all?

Flies in the Ointment

The first fly in the ointment was early considerations that monosulcate pollen from the Triassic of North America may have independently acquired angiosperm-like characteristics (Zavada 1990). The same holds for the angiosperm-like wind dispersal mechanism in a Triassic plant seed, which is “probably representing a case of convergent evolution of a similar structure in a gymnosperm” (Axsmith et al. 2013).

Doyle (2005) mentioned that the angiosperm-like Triassic Crinopolles grains possess a gymnosperm-like thick endexine layer, which is unexpected under common schemes of angiosperm evolution. However, he proposed a new scheme (Doyle 2001), which could make this feature equally likely to be a retained primitive character that was later reduced in angiosperm evolution. He concluded that “more evidence on the plants that produced Crinopolles pollen is needed to determine whether they were angiosperm relatives or an extinct convergent line.”

Herendeen et al. (2017) reviewed molecular and paleontological evidence for the age of angiosperms and remarked that “angiosperm-like pollen grains with reticulate pollen walls [were] recorded from the Middle and Late Triassic, but so far their botanical affinity remains uncertain.” They concluded that a “critical assessment of these reports shows that, so far, none provide unequivocal evidence of pre-Cretaceous angiosperms.” They cautioned that “it may also be significant that similar reticulate angiosperm­-like grains have not been reported from the Jurassic.” They also cautioned that tricolpate pollen (Eucommiidites) from the Triassic and Jurassic was previously misidentified as angiosperm pollen resembling the extant genus Eucommia, but later was shown “to have been produced by an extinct group of non­-angiosperm seed plants, Erdtmanithecales,” likely related to living gnetophytes (Friis & Pedersen 1996). This is especially relevant, because according to the authors, the Crinopolles not only share with Eucommiidites grains the non-angiosperm-like thick endexine but also a similar unusual distribution of apertures.

A Disturbing Discrepancy

Coiro et al. (2019), co-authored by the very James Doyle mentioned before, studied the disturbing discrepancy between molecular clock datings and the fossil record of angiosperms. They found that the sequence of pollen types in the Lower Cretaceous strongly conflicts with any earlier datings for the origin of angiosperms. It would simply make no sense that features which clearly appear in a sequence in the Cretaceous were already present all along in the Triassic, but absent throughout the Jurassic period, and then miraculously reappear in a particular order that suggests a Cretaceous sequential origin. The authors furthermore concluded that “critical scrutiny shows that supposed pre-Cretaceous angiosperms either represent other plant groups or lack features that might confidently assign them to the angiosperms.”

The most recent study by Zavialova & Tekleva (2021) reviewed all the angiosperm-like pollen from pre-Cretaceous deposits that lack angiosperm macrofossils. They concluded: “The general morphology, sculpture, exine ultrastructure, as well as some available data on associations with macroremains allow us to interpret with sufficient confidence an overwhelming majority of such finds as gymnosperm pollen.” That’s pretty unambiguous and finally buries the whole thing. Concerning the remaining finds they likewise clarified: “The finds of Pre-Cretaceous reticulate pollen seem the most controversial; however, those from the Permian are also known from conifer sporangia, and a gymnosperm variant of the endexine was revealed in one of Triassic reticulates.”

Thus, the alleged Triassic angiosperm pollen fossils just seem to repeat the same pattern of misidentified gymnosperms as the alleged Jurassic angiosperm plant fossils we have discussed in my previous articles. It looks like the strong desire to find what Darwins’s theory would predict strongly biases the interpretations of some experts. Instead, the consistent failure of all these claims should be considered as conflicting evidence and failed predictions that challenge the theory. With all counterarguments now decisively refuted, Darwin’s abominable mystery remains a sting in the flesh of Darwinists, as part of the general inconvenient pattern of abrupt appearances in the fossil record that suggest intelligent design (Bechly & Meyer 2017Bechly 2021f).

P.S.: The above mentioned studies (e.g., Crane 1987Herendeen et al. 2017Coiro et al. 2019) also rejected Triassic macrofossils of supposed angiosperm origin, i.e., Sanmiguelia (Cornet 1986, 1989a), either as misidentified gymnosperms or at least insufficiently justified.