Abstract Detail

Paleobotany

Kustatscher, Evelyn [1], Nowak, Hendrik [1].

Microspores in macroplant fossils from the Triassic of Central Europe.

Spores and pollen are produced in large numbers by plants (thousands in each sporangium) and distributed by wind, water or animals up to tens of thousands of kilometers away from the source area. Thanks to this and their high preservation potential (chemically resistant wall), they are particularly useful for the reconstruction of environments and biotic responses to the climate of the past. This works very well in relatively young sediments containing spores/pollen from extant plants. However, the older the rocks are, the higher is the percentage of spores and pollens originating from extinct plants. In order to reconstruct their botanical affinity, we have to identify the original plant, and in particular the corresponding reproductive organs. Spores or pollen from a single plant species or even an individual plant or sporangium may vary in shape to a point that equivalent forms that were found dispersed in the sediment have been described as different species or even genera. In addition, not all these organs were ripe at the moment of the burial, and therefore they do not always contain completely developed microspores. Our study aims to reconstruct the various ontogenetic stages of the microspores and to identify the ranges and drivers of intraspecific variability. A special focus lies on verifying the percentage of "abnormal/mutated" grains within single sporangia, since high abundances of such forms have lately been related to environmental stress during mass extinctions. Our material comes from various localities with well-preserved Triassic floras in Europe. One important source area are the Dolomites (Northern Italy), where are a number of outcrops yielding Middle Triassic plant fossils in an exceptional state of preservation are located. Dozens of different species of horsetails, lycophytes, ferns, seed ferns, cycads and conifers have been found, mainly in the form of vegetative organs (stems, branches, leaves) but often also with male and female reproductive organs. The detailed study of the fertile structures allowed us to identify the paleobotanical affinity of dispersed spores and pollen in the sediment. In order to determine possible adverse effects of acid treatment, we performed a series of variations of the standard technique for the maceration of in situ sporomorphs on sporangia of Asterotheca merianii, a marattiaceous fern that is common in Carnian floras in Europe. Our results showed that variations in the treatment parameters had less impact on the observable characters than differences between individual plants and within sporangia.

1 - Museum of Nature South Tyrol, Bindergasse 1, Bolzano, BZ, 39100, Italy

Keywords:
In situ spores
Triassic
Ferns
intraspecific variability.

Presentation Type: Oral Paper
Session: PAL3, Paleobotany I: Paleozoic and Mesozoic Paleobotany
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 10:45 AM
Number: PAL3004
Abstract ID:584
Candidate for Awards:None