New fossil species of moonseed household present in Yunnan

The moonseed household (Menispermaceae) consists primarily of vines, uncommon shrubs or bushes with unisexual flowers, and drupaceous fruits. Up to now, six species and three unidentified species in morphogenus Palaeosinomenium have been reported. However, extra fossil proof is required to detect the morphological evolution between the morphogenus and the residing genera.

During their field work, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences collected an endocarp specimen of moonseed plant household from the Upper Eocene Shuanghe Formation within the Jianchuan Basin, Yunnan, China. The endocarp fossil was characterised by a novel bilaterally compressed condyle (Menispermum kind), and a horseshoe-shaped locule that may very well be assigned to the subfamily Menispermoideae.

After morphological research and literature overview, the researchers assigned the fossil endocarp from Jianchuan Basin to a brand new species and named it as Palaeosinomenium hengduanensis to discuss with its kind locality within the Hengduan Mountain Range. The new fossil species findings had been printed in Review of Palaeobotany and Palynology.

The new fossil species is characterised by a horseshoe-shaped endocarp, an excavated central space, surrounded by a barely asymmetrical C-shaped lateral ridge, and an elliptic aperture positioned close to the longer endocarp limb.

Moreover, the fossil species share related morphological traits with Sinomenium, which appeared within the southeastern margin of the Tibetan Plateau by the Eocene.

The fossil website is positioned within the fashionable distribution space of the residing species Sinomenium acutum, a possible nearest residing relative of the new species. The fashionable and the late Eocene local weather in Jianchuan are appropriate for tribe Menispermeae.

“The finding of P. hengduanensis supports that the divergence within the tribe Menispermeae might have occurred by the Late Eocene and the species similar to modern S. acutum appeared in the southeastern margin of the Tibetan Plateau as early as in the Late Eocene,” mentioned Su Tao of XTBG.