The Genus Sinularia encompasses a large amount of very similar looking soft corals, so coming down with an exact ID is rather difficult in most instances. This is actually common for most of the Leather Corals, and similar problems often arise when attempting to ID Toadstool Leathers
(Genus Sarcophyton).
I ran into this issue a few months ago when trying to properly identify all the corals in my tank... what a mess. :rolleye1: :lol:
Anyway, here's a very useful link regarding Sinularia & Soft Coral Identification:
http://www.wetwebmedia.com/alcyoniidsii.htm
Sinularia Dura is commonly known as the "Cabbage Leather" and most look quite different. However, if you check the link above, one of the pictures does look similar to the
Sinularia Flexibis. From everything I've read, I don't think classification is color specific. Like I said, there are so many different variations, most everywhere just has them generically listed as
Sinularia sp.
Here are some of the "most common" images I found.
Sinularia Dura
Sinularia Felxibis
Here's mine... It's a greenish/yellow
Sinularia Felxibis (Finger Leather or Spaghetti Leather). Although looking at the link... it could fit into a few different classifications. It's under intense lighting with my SPS, grows like a weed, and has crazy extension. It's actually one of my favorite corals in the tank. (btw... thanks Kevin :thumbsup: )
Here's a picture when I first got it... About the size of a quarter.
Here it is now in the lower left hand side of my tank, about 8" tall fully extended. I rarely see it in the "skinny finger" :lol: form like your initial picture though. It may have something to do with the flow of the water... I couldn't tell you, but 90% of the time it looks like the lower picture.