Angiosperm-like pollen and Afropollis from the Middle Triassic (Anisian) of the Germanic Basin (Northern Switzerland).

Susanne Feist-Burkhardt,Peter A Hochuli

doi:10.3389/fpls.2013.00344

Abstract

Here we report on angiosperm-like pollen and Afropollis from the Anisian (Middle Triassic, 247.2–242.0 Ma) of a mid-latitudinal site in Northern Switzerland. Small monosulcate pollen grains with typical reticulate (semitectate) sculpture, columellate structure of the sexine and thin nexine show close similarities to early angiosperm pollen known from the Early Cretaceous. However, they differ in their extremely thin inner layer (nexine). Six different pollen types (I–VI) are differentiated based on size, reticulation pattern, and exine structure. The described pollen grains show all the essential features of angiosperm pollen. However, considering the lack of a continuous record throughout the lower part of the Mesozoic and the comparison with the oldest Cretaceous finds we suggest an affinity to an angiosperm stem group. Together with the previously published records from the Middle Triassic of the Barents Sea area the angiosperm-like pollen grains reflect a considerable diversity of the parent plants during the Middle Triassic. Sedimentological evidence and associated palynofloras also suggest a remarkable ecological range for these plants. Associated with these grains we found pollen comparable to the genus Afropollis. Representatives of this genus are commonly recorded in Lower Cretaceous sediments of low latitudes, but until now had no record from the lower part of the Mesozoic.

Highlights

In spite of extensive research the origin and temporal and spatial distribution of early flowering plants are still a matter of debate
In this paper we focus on fossil evidence, presenting the so far oldest angiosperm-like pollen from the Middle Triassic, a record that predates the generally accepted first occurrence of angiosperm pollen by more than 100 Ma
From the same area as the angiospermlike pollen grains we report on the oldest occurrence of the genus Afropollis

Summary

INTRODUCTION

In spite of extensive research the origin and temporal and spatial distribution of early flowering plants are still a matter of debate. The first broadly accepted records of angiospermous pollen grains are known from the earlier part of the Early Cretaceous (Valanginian—early Hauterivian) (Gübeli et al, 1984; Trevisan, 1988; Brenner, 1996) Within this interval they are extremely rare; continuous records exist only from the Barremian onwards, and this only for low and mid-latitudes (Hickey and Doyle, 1977; Crane and Lidgard, 1989; Hughes, 1994; Schrank and Mahmoud, 2002). Cornet (1977, 1989b) was the first who reported on occurrences of pollen grains with angiospermous features from Triassic sediments These records are commonly regarded as inadequate evidence for an earlier origin of the group (e.g., Friis et al, 2011). This assemblage is interpreted to be of middle to late Anisian (Pelsonian/Illyrian) age (see Kürschner and Herngreen, 2010; Hochuli et al, 2012)

MATERIALS AND METHODS

CONCLUSIONS