Ancestor of all animals identified in Australian fossils

A wormlike creature that lived more than 555 million years ago is the earliest bilaterian

Date: March 23, 2020

Source: University of California - Riverside

A team led by UC Riverside geologists has discovered the first ancestor on the family tree that contains most familiar animals today, including humans.

The tiny, wormlike creature, named Ikaria wariootia, is the earliest bilaterian, or organism with a front and back, two symmetrical sides, and openings at either end connected by a gut. The paper is published today in Proceedings of the National Academy of Sciences.

The earliest multicellular organisms, such as sponges and algal mats, had variable shapes. Collectively known as the Ediacaran Biota, this group contains the oldest fossils of complex, multicellular organisms. However, most of these are not directly related to animals around today, including lily pad-shaped creatures known as Dickinsonia that lack basic features of most animals, such as a mouth or gut.

The development of bilateral symmetry was a critical step in the evolution of animal life, giving organisms the ability to move purposefully and a common, yet successful way to organize their bodies. A multitude of animals, from worms to insects to dinosaurs to humans, are organized around this same basic bilaterian body plan.

Evolutionary biologists studying the genetics of modern animals predicted the oldest ancestor of all bilaterians would have been simple and small, with rudimentary sensory organs. Preserving and identifying the fossilized remains of such an animal was thought to be difficult, if not impossible.

For 15 years, scientists agreed that fossilized burrows found in 555 million-year-old Ediacaran Period deposits in Nilpena, South Australia, were made by bilaterians. But there was no sign of the creature that made the burrows, leaving scientists with nothing but speculation.

Continued

Oldest Panda Fossils Found in Surprising Place

All giant pandas may come from China, but fossils reveal that the oldest known ancestor of the lineage dwelled in Spain, researchers say.

The giant panda (Ailuropoda melanoleuca) is known worldwide for its black-and-white fur. The giant panda is unique among bears for dining almost entirely on bamboo — other members of the bear family are omnivorous or mostly carnivorous.

Genetic evidence suggests the ancestors of giant pandas diverged from other bears 18 million to 22 million years ago. However, much remains uncertain about what early giant pandas were like and how this lineage of bears changed over time — before the new find, the earliest undisputed giant panda fossils recovered were about 8.2 million years old at most, and were from China.

Read on:  http://www.livescience.com/24788-oldest-panda-fossils.html