The oldest human ancestor is a 540-million-year speck-size creature without an anus, a new study finds. Researchers found the remains of ancient critter in central China which resembles a bag-like sea organism. The researchers find the creature to be so novel, and the lack of presence of anus suggests that it consumed food and excreted from the same orifice.

The discovery was carried out by an international team of scientists from the UK, China, and Germany. "To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail was jaw-dropping", Prof. Simon Conway Morris, one of the researchers from the University of Cambridge says. Saccorhytus measures about a millimeter in size and is thought to have resided between grains of sand on the seabed.

The creature has been named Saccorhytus. "Saccus" translates to "sac" in Latin, and "rhytis" refers to "wrinkle" in Greek. Basically, its name refers to its wrinkled, sac-like body. Due to its oval body and large mouth, the oldest human ancestor is likely a deuterostome, the Live Science says.

A deuterostome is a group composed of all vertebrates, including humans, and some invertebrates, such as starfish. The microscopic sea animal is the most prehistoric creature on the evolutionary path that led to fish and, ultimately, to humans. Scientists have remarked how "exquisitely well preserved" the fossilized traces of the microscopic creature are.

According to the BBC, details of the discovery appear in the journal Nature. Researchers say that most striking feature is its ridiculously large mouth. They conclude that it probably fed by engulfing food particles, or even other creatures.

Other interesting features are the conical structures on its body. The scientists suggest that this might have allowed the water that it swallowed to escape. Essentially, this means that the oldest human ancestor might have had a very early version of gills.