In situ pollen of voltzialean conifers from the Middle Triassic in Central Europe

Abstract

Conifers of the order Voltziales were important components of Triassic floras. Their pollen is likewise abundant in microfloras from this period. Voltzialean pollen grains are known to have a considerable range of morphologies, but taxonomic distinctions based on these differences require thorough descriptions of in situ pollen from well-preserved male cones. We studied the pollen grains extracted from male cones from the palaeofloras of the Dont Formation in Italy, the Grès à Voltzia in France (both Anisian, lower Middle Triassic), and the Erfurt Formation in Germany (Ladinian, upper Middle Triassic). Pollen cones from the Dont Formation contain taeniate bisaccate pollen that are otherwise known only from Paleozoic conifers, as well as in one case multi-taeniate pollen grains resembling those commonly associated with seed ferns. By contrast, in situ pollen grains from the Grès à Voltzia and the Erfurt Formation are mostly comparable to Illinites, Angustisulcites or alete forms such as Voltziaceaesporites, Alisporites, and Klausipollenites. Malformations are usually rare, but notable are recurring patterns of smaller or larger than normal corpus sizes, which could lead to different taxonomic assignments if found dispersed. Overall, pollen grain sizes in general can vary considerably within a sample and even more between samples from different specimens of the same species. By contrast, size ranges of different species are overlapping significantly.