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Botanical affinity of the taxa encountered in the Maywood Formation

Citation

Zaton, Michal; Mingxi, Hu; di Pasquo, Mercedes; Myrow, Paul (2021), Botanical affinity of the taxa encountered in the Maywood Formation, Dryad, Dataset, https://doi.org/10.5061/dryad.wwpzgmsk7

Abstract

This dataset lists the species of palynomorphs occurring in the Middle Devonian (Givetian) deposits of the Maywood Formation of Cottonwood Canyon, Wyoming, USA. The palynological investigation was carried out in order to decipher the age and paleoenvironment of the microconchid tubeworms (Tentaculita) which were described from the deposits of the Maywood Formation. The retrieved data suggest a likely brackish water origin for the deposits studied, although temporary fully freshwater conditions cannot be ruled out. Indeed, the terrestrial spores recovered from the Maywood samples belong to progymnosperm, lycopsid and primitive fern groups (see the data attached), which were major components of swamp plant communities, suggesting very close proximity of fresh water sources to the depositional paleoenvironment of the Maywood Formation. The highly abundant progymnosperm Geminospora spp., in particular, specifically suggests deposition in, or adjacent to, fluvio-lacustrine, lower floodplain, or paralic environments. Fine granular and fibrous amorphic organic matter with orange fluorescence has been linked with various terrestrial and algal aquatic sources. In addition, well-preserved terrestrial spores, and the presence of megaspores, tetrads, and pyrite, all support a brackish, shallow-water depositional setting. This is in agreement with other fossiliferous and lithologic evidence provided in this and in previous studies.

Methods

The palynomorphs were retrieved in order to better determine the age of the investigated deposits of the Maywood Formation and decipher their paleoenvironments. Four samples of organic rich shale, calcareous shale, and calcisiltite were subjected to standard palynologic maceration which was followed using HCl (10%) and HF (70%) and several washes with distilled water allowed the neutralization of residues, which were sieved using 5 µm meshes. Four slides mounts were made using a drop of residue mixed with one drop of polyvinyl alcohol. After drying, one drop of clear casting resin was added and the cover slip turned and sealed. The residues were oxidized with 3 ml of Schultz solution in a hot bath for a short time, and after washing and centrifuging until neutralization, a 10% solution of NH4OH was added. The residues were then placed in a hot water bath for two minutes, and washed three or four times. Two sets of slides were created: one set with oxidized residues and another set with oxidized residues stained with a drop of Bismarck Brown Y.

Usage Notes

The dataset attached is supplementary to the article entitled "Adaptive function and phylogenetic significance of novel skeletal features of a new Devonian microconchid tubeworm (Tentaculita) from Wyoming, U.S.A." by Michał Zatoń, Mingxi Hu, Mercedes Di Pasquo and Paul M. Myrowwhich will appear in Journal of Paleontology.

The dataset only includes the list of palynomorphs detected in deposits of the Maywood Formation in Cootonwood Canyon, Wyoming, USA and their stratigraphic ranges.