Complex Skeletons Might Be Older Than Anyone Thought

Gizmodo ^ | Sunday, November 8, 2015 | Kiona Smith-Strickland

[SunkenCiv]

Most of the major groups in the animal kingdom we know today first appeared in the fossil record around 540 million years ago, which geologists consider the beginning of the Cambrian Period. It’s likely that the ancestors of these groups already existed, but since the fossil record depends mostly on skeletons being preserved in sediment that later becomes rock, the ancestors of today’s animals couldn’t really leave their mark on the fossil record until they evolved hard skeletons. And about 540 million years ago, that’s exactly what they did...

Some animals had evolved the trick of building skeletons for themselves before the Cambrian period, such as sponges and corals, but these are some of the most primitive animals on Earth; their body structures are very simple, and they haven’t changed much since pre-Cambrian times. These primitive organisms aren’t believed to be the ancestor of any of today’s more complex species.

And until recently, scientists thought about N. hermanastes was more closely related to sponges: a primitive organism, unrelated to today’s more complex marine life...

When Wood and her colleagues took a closer look at some especially well-preserved specimens, however, they discovered that its calcium carbonate skeleton was more complex than those of sponges or coral, and in fact resembled those of today’s mollusks and other marine organisms that live at the bottom of the ocean.

They also found that the tiny goblet-shaped animal shows early signs of bilateral symmetry, meaning that its body can be divided into left and right halves. Animals with bilateral symmetry are usually more complex than animals like sponges, which have no symmetry at all, or animals like the sea anemone, which have radial symmetry.

[SunkenCiv]