Is this algae or something else?

[swiss1939]

Got these squiggly lines growing on my dry rock that appear to have come from a small live rock i placed up against it. At first I thought it was possibly some form of worms or critters but was told it is probably algae.

Anyone know what type of algae this is? I find it's grow patterns interesting.

Center of photo, the dark brown swirly lines on the dry rock.

Another one dead center slightly smaller

And another one that is growing in more straight line

 

[susan ingram]

BUMP

 

[swiss1939]

Thanks for the bump. Here's an update on this.. I believe they are not algae, but are animal because the long one I circled has moved quite a bit from yesterday in a completely different pattern than before, which would require a complete move, not a growth pattern that is static once laid down.

 

[rwreef]

Almost looks like a spaghetti worm...but I could be wrong.

 

[swiss1939]

Definitely no a spaghetti worm as its only the tentacles, no worm body. I'm wondering if they are some sort of brittle star or possibly a bristle worm infant?