Two new species of Late Devonian seed Cosmosperma from Zhejiang and Anhui, South China

Abstract

The earliest ovules or seeds widely reported from the Late Devonian (Famennian) are crucial for understanding the evolution of seed plants. Cosmosperma, the first Devonian seed documented in China and East Asia, is characterized by cupules with multiple segments enclosing a single ovule and covered by prickles. Two new Cosmosperma species, Cosmosperma dicrana sp. nov. and Cosmosperma lepta sp. nov., are now identified from the Upper Devonian (Wutong Formation) of Zhejiang and Anhui provinces, China, respectively. C. dicrana exhibits dichotomized fertile branches terminating in pairs of cupulate ovules, with centrifugally extending cupule segments at their distal portions. C. lepta displays slender cupulate ovules on pinnate fertile branches. Both species possess prickles on their cupules. A comparison with coeval seed plant taxa reveals differences in fertile branch types and suggests different evolutionary levels. The potentially weak dispersal ability of Cosmosperma is suggested by the absence of specialized structures for wind or water transport. Prickles on Cosmosperma cupules do not suggest adaptations for epizoochory but facilitate entanglement and friction. The adaptations for short-distance dispersal can be advantageous in a disturbed and heterogeneous environment. The presence of Late Devonian seed plant taxa with dispersal-adapted traits hints at habitat divergence, with some possibly inhabiting uplands or areas away from the coast. The prickles may also be an adaptation for maintaining stability in small- to medium-sized plants of the Late Devonian coastal communities.

Keywords

Cosmosperma / cupulate ovules / dispersal strategy / fertile branches / Late Devonian

RIGHTS & PERMISSIONS

2024 Institute of Botany, Chinese Academy of Sciences.