Chinese scientists have unraveled the mystery of the origin of ctenophore phylum

Kunming, March 26 (Xinhua) -- Through systematic research on the chengjiang biota of difficult fossil foot cup worms, Chinese scientists have solved the mystery of the origin of ctenophores, confirming that ctenophores and stingrays jointly originate from benthic solid organisms. The results have been published online in the international journal Contemporary Biology and will be officially published on April 1 with a cover article.

The corresponding author of the paper, Cong Peiyun, a researcher at the Yunnan Provincial Key Laboratory of Paleontology Research of Yunnan University, introduced that ctenophores are bitenodermal animals, and there is a debate in the scientific community about their origins. Traditional textbooks refer to them together with spiny animals (such as corals, jellyfish, etc.) as coelenterates, and consider them to be transitional types between sponges and trioderms. However, recent molecular systematics studies have shown that ctenophores may be basal taxa of multicellular animals, suggesting that they may be branches of complex tissues and organs that have evolved independently in multicellular animals. In this context, the origin and evolution of ctenophores have become one of the major scientific issues in the study of the early evolution of multicellular animal phylum.

About 520 million years ago, the Chengjiang biota in Yunnan recorded the early radiation evolution of animal phyla during the Cambrian explosion of life, and was a treasure trove of fossils specifically buried in the early Cambrian period, of which the foot cup worms were a unique type of fossil. Under the guidance of his supervisor Cong Peiyun, Zhao Yang, a doctoral student at the Key Laboratory of Paleontology of Yunnan University, conducted a systematic study of many fossil specimens of peduncula in the Chengjiang biota, identified a new genus of Trichophyllum Dai flowerworm, and further studied the fossil species with similar morphological characteristics and body structure in the Cambrian Period, confirming that the composite cilia structure is a common feature of these fossil taxa, and is homologous with the ctenophores (cilia clusters) of living ctenophores.

Professor Hou Xianguang of Yunnan Provincial Key Laboratory of Paleontological Research of Yunnan University conducted a systematic analysis of the matrix constructed by 93 taxa and 278 morphological characteristics, and the results supported that benthic solid fossil taxa such as peduncles were the stem groups of living ctenophores, indicating that the composite cilia structure of early ctenophores was mainly used for filter feeding in the early days. The team first proposed a new hypothesis about the evolution of ctenophores' body shape, that is, living planktonic ctenophores evolved from early types of solid filter feeding through the specialization and degradation of different body structures. The results also show that the diversity of ctenophores has reached a high level during the Cambrian explosion of life, and the stem group of solid ctenophores and planktonic ctenophores coexisted in the same period of history.