Study on macro- and sporemorphology of a new species of Coniopteris (Dicksoniaceae) from the Middle Jurassic of western Liaoning, Northeast China

Abstract

Coniopteris Brong. emend. Harris, 1961 is an abundant and diverse fern taxon during the Mesozoic period, and it is commonly interpreted as a dicksoniaceous fern. With a probably Late Triassic origin, it flourished twice, in the Middle Jurassic and Early Cretaceous, respectively, then gradually disappeared after the late Early Cretaceous. Over 80 species have been ascribed to Coniopteris worldwide, of which at least 65 species were once found in China. In this paper, a new species, Coniopteris haifanggouensis sp. nov., is described, based on a well-preserved fertile frond with in-situ spores from the Middle Jurassic Haifanggou Formation in Beipiao City, western Liaoning Province, Northeast China. The frond is at least bipinnate. The fertile pinnae are lanceolate in shape, alternately arranged on the rachis, and the laminae are reduced to a stalk bearing long elliptical or rounded sorus at the tip. It is tentatively proposed that the frond type of C. haifanggouensis should be dimorphic. The spores are rounded-tetrahedral, with granular or wrinkled surfaces, and long and straight triradiate cracks. Compared to the dispersed spores preserved in the Haifanggou Formation, the in-situ spores of C. haifanggouensis are most similar to Deltoidospora magna in both gross morphology and microstructural details. The present finding enriches the species diversity of Coniopteris in China, and provides new evidence for further understanding of the characteristic of in-situ spores and frond types of the genus.