Muscle tissue is a soft tissue, and is one of the four fundamental types of tissue present in animals. There are three types of muscle tissue recognized in vertebrates: Read more ...

Animals first flex their muscles: Earliest fossil evidence for animals with muscles   Science Daily - August 28, 2014
A new fossil discovery identifies the earliest evidence for animals with muscles. An unusual new fossil discovery of one of the earliest animals on earth may also provide the oldest evidence of muscle tissue -- the bundles of cells that make movement in animals possible. The fossil, dating from 560 million years ago, was discovered in Newfoundland, Canada.

A new fossil discovery identifies the earliest evidence for animals with muscles. An unusual new fossil discovery of one of the earliest animals on earth may also provide the oldest evidence of muscle tissue -- the bundles of cells that make movement in animals possible. The fossil, dating from 560 million years ago, was discovered in Newfoundland, Canada. On the basis of its four-fold symmetry, morphological characteristics, and what appear to be some of the earliest impressions of muscular tissue.

Historically, the origin, evolution and spread of animals has been viewed as having begun during the Cambrian Explosion, a period of rapid evolutionary development starting 541 million years ago when most major animal groups first appear in the fossil record. However, in recent decades, discoveries of preserved trackways and chemical evidence in older rocks, as well as molecular comparisons, have indirectly suggested that animals may have a much earlier origin than previously thought.

Ancient muscle tissue extracted from 18 million year old salamander fossil   PhysOrg - November 5, 2009
Scientists have extracted organically preserved muscle tissue from an 18 million years old salamander fossil. The discovery by researchers from University College Dublin, the UK and Spain, reported in the Proceedings of the Royal Society B shows that soft tissue can be preserved under a broader set of fossil conditions than previously known. The scientists claim that their discovery is unequivocal evidence that high-fidelity organic preservation of extremely decay prone soft tissues is more common in the fossil record - the only physical record of the history of life on earth.