maximum weight estimated at for females, while arctic lion's mane jellyfish may reach comparable sizes. The longest animal on record is also thought to be a soft-bodied organism, a long thread-like bootlace worm, Lineus longissimus found on a Scottish beach 1864. Siphonophores may grow to considerable sizes too, though they are colonial organisms, and each single animal is small. Most soft-bodied organisms are as small or smaller, even microscopic. The various organisms grouped as mesozoans and the curious Placozoa are typically composed of just a few hundred cells. Fossil record The lack of hard parts in soft-bodied organisms makes them extremely rare in the fossil record. Accordingly, the evolutionary histories of many of the soft-bodied groups are poorly known. The first major find of fossil soft-bodied animals was from the Burgess Shale in Canada. Today, several sites with Burgess Shale type preservation are known, but the history of many groups of soft-bodied animals is still poorly understood. References Zoology Biological classification