Yilingia

Embargo until September 04, 2019 at 18:00 (London time) or September 04, 2019 at 13:00 (US Eastern Time)

Quotes from Shuhai Xiao:

The discovery of Yilingia spiciformis and associated trace fossils shed important light on the early evolution of segmentation and motility in animals.

Yilingia is a fossil animal of the Ediacaran Period (roughly 635-540 million years ago). Specimens of Yilingia were unearthed from carbonate rocks of the late Ediacaran Shibantan Member in the Yangtze Gorges area of South China. These carbonate rocks were deposited in balmy shallow waters between 550 and 540 million years ago, more than twice older than the oldest dinosaurs.

Yilingia is a long and slender strap-like soft-bodied animal with a bilaterally symmetric and segmented body. Like trilobites, Yilingia has a segmented and trilobate body; each of its body segments has three lobes — a central lobe and two lateral lobes. Unlike trilobites, however, Yilingia does not have a hardened skeleton and, although it has a head and a tail, its body segments do not show much difference along the body length whereas body segments of trilobites are patently different in the head, thorax, and tail. Rather, Yilingia is rather wormy in its soft-bodied strap-like body.

An unusual specimen of Yilingia was found to be preserved and physically connected with a trail it made just before death. This kind of trace fossils are called mortichnia or traces produced during a death march. The Shibantan mortichnium leaves no doubt that Yilingia was a mobile animal and allows us to infer the direction of movement. The mortichnium also builds a bridge to understand similar trails that are preserved in isolation. This is critically important because, although trace fossils such as burrows, trails, and tracks are abundant in late Ediacaran rocks, it is often impossible to determine what animals produced them. Without this information, trace fossils offers only limited insights into early animal evolution.

Yilingia is neither the oldest segmented animal nor the oldest motile animal, but it is thus far the oldest known segmented and motile animal capable of producing long and continuous trails. As such, it has important implications for the early evolution of animal segmentation and motility. The origin of segmentated and motile animals is a monumental innovation that shaped the Earth’s surface environment. Today, mobile animals leave unmistakable footprints on Earth, both literally and metaphorically. Animals (including humans) are movers and shakers on modern Earth, in a large part due to their ability to move. However, animal motility had a modest start more than half billion years ago!

About Shuhai Xiao: Dr. Xiao is a professor of geobiology and a Patricia Caldwell faculty fellow in the Department of Geosciences at Virginia Tech. He studies the co-evolution of life and its environments in Earth history, and teaches undergraduate and graduate courses in Earth-life history. His research to understand the geological past of the Earth-life system is inspired by its uncertain future, and his enthusiasm for teaching is motivated by the need for a new generation of globally engaged science workforce. He was a Guggenheim fellow, a winner of the Paleontological Society Charles Schuchert Award, and a winner of the Virginia Outstanding Scientist Award.