The smallest Zosterophyllum plant from the Lower Devonian of South China and the divergent life history strategies in zosterophyllopsids

Plants have evolved different life history strategies to overcome the limited amount of available resources; however, when and how divergent strategies of sexual reproduction evolved in early land plants is not well understood. As one of the notable and vital components of early terrestrial vegetation, the Zosterophyllopsida and its type genus Zosterophyllum, reached maximum species diversity during the Pragian (Early Devonian; ca. 410.8–407.6 million years ago). Here we describe a new species, Z. baoyangense sp. nov., based on well-preserved specimens from the Pragian-aged Mangshan Group of Duyun, Guizhou Province, China. The new plant is characterized by its small size, K-shaped branching, and tiny spikes with five to ten sporangia. This plant is most likely r-selected, completing its whole lifespan in a short time, and such a strategy contributes to reproduction in a suitable window time. By contrast, most other species of Zosterophyllum and the zosterophyllopsids on a broader scale ..., (a) Morphological measurements of Zosterophyllum species
The morphological descriptors of Zosterophyllum species are shown in Figure S2, including the width and length of spikes, width, and length of axes, sporangial height and width, etc. These descriptors are commonly used in the documentation of fossil plants and can be easily obtained.
Compared to extant plants, the fertile investment involving the total number of spores and survival rate of spores cannot be obtained from plant fossils. Here, we define a new descriptor, total sporangial accommodation (TSA), to evaluate the mass or energy investment for spore production in each plant. The TSA is estimated by the following formula for each fertile axis:
TSA = n·(h·w·t)
where the total number of visible sporangia in a spike or fertile region is symbolized as n, and the sporangial height, width, and thickness are symbolized as h, ,w and t respectively.
The sporangial thickness is rarely observed, but it is seemingly stable as observed i..., , # The smallest *Zosterophyllum* plant from the Lower Devonian of South China and the divergent life history strategies in zosterophyllopsids

## **Authors**

Pu Huang [[e-mail]](mailto:[e-mail])

Jia-Shu Wang [[e-mail]](mailto:[e-mail]) 

Yi-Ling Wang [[e-mail]](mailto:[e-mail])

Lu Liu [[e-mail]](mailto:[e-mail])

Jing-Yu Zhao [[e-mail]](mailto:[e-mail])

Jin-Zhuang Xue [[e-mail]](mailto:[e-mail])

## **File list**

Huang_tables_figures_ESM.pdf

source_data_of_figure_2.zip

source_data_of_figure_3.zip

The_rscript_Zosterophyllum.R

## **File descriptions**

**Huang_tables_figures_ESM.pdf** — The file contains supplementary figures S1–S5 and supplementary tables S1–S4, including traffic map of the fossil locality and lithological column of the Mangshan Group at the Baoyang section with plant-bearing bed (figure S1); sketch illustrations of morphological descriptors of ...