A new species of Leptocycas (Zamiaceae) from the Upper Triassic sediments of Liaoning Province, China

Abstract

A new cycad, Leptocycas yangcaogouensis sp. nov., was found in sediments from the Late Triassic in western Liaoning, China. The pinnately compound leaves (Pseudoctenis type) are screwed in a crown on the stem top. The leaflets are linear, with parallel veins and decurrent bases on the rachis. The leaf bases are persistent. The cataphylls intermix with the leaves. The female cone is ovoid in shape. The characteristics of the new plant are more similar to those of Leptocycas gracilis, a Triassic cycad from North America, but the new species differs from L. gracilis in the size of its stem (7-8 vs. 3-5 cm in diameter, respectively), leaves (length × width 100 × 16 vs. 30 × 7 cm, respectively) and leaf density along the stem (4-6 vs. 1-2 bases/1 cm length, respectively). Both L. gracilis and L. yangcaogouensis, having leaves of the Pseudoctenis type, show a closer relationship to the extant Dioon of Zamiaceae. The present study provides evidence for the origin of the genus Dioon, which may have come from Leptocycas plants of the Triassic. It would be assumed that the extent cycads in Zamiaceae originate from the pteridosperms in the Late Paleozoic and have evolved through the stage of L. gracilis and L. yangcaogouensis in Late Triassic, and reaching the extant Dioon.

A new cycad stem from the Cretaceous in Argentina and its phylogenetic relationships with other Cycadales

“…The cones resemble pollen cones and are located on the stem apex. A new species, Leptocycas yangcaogouensis Zhang, Yao, Chen & Li, was described in Late Triassic China (Zhang et al ., ). The fossil remains belong to the upper part of the stem, which has leaves, cataphylls and a female cone.…”

Patterns of chloroplast DNA variation in Cycas debaoensis (Cycadaceae): conservation implications

“…The earliest fossil evidence in Gansu province from the Carboniferous era reveals that cycads may originate from northern China (Li et al 1976;Li 1982). The hitherto most completely preserved cycad specimen is also collected from northeast China (Liaoning) and can be traced back to the Upper Triassic (Wang et al 2009;Zhang et al 2010). These discoveries contribute much to our understanding of the morphology and evolution of cycads.…”

The Historical Demography and Genetic Variation of the Endangered Cycas multipinnata (Cycadaceae) in the Red River Region, Examined by Chloroplast DNA Sequences and Microsatellite Markers

“…The Cycad is considered an old lineage because of its ancient morphological characters and fossil records which could date to the Early Permian [ 1 ] or possibly even the late Carboniferous period (approximately 300 million years ago) [ 2 ]. Cycads became a dominant plant group during the Mesozoic, as shown by numerous fossils of megasporophylls and ovalate strobili, as well as vegetative shoots, leaves and trunks [ 3 – 9 ]. However, one recent fossil-calibrated molecular phylogenetic study based on multiple DNA sequence data proposed that extant Cycads originated no more than 12 million years ago; the Cycads underwent a recent synchronous global rediversification beginning in the late Miocene, followed by a slowdown towards the recent [ 10 ].…”