Okay, so just in case anyone else's dogs decide to eat a starfish…
It depends on what kind of starfish. Some supposedly are toxic. Apparently the ones my kids ate are not that big of a deal. I think Miles got most of it. He threw up about a third of it five hours after consuming it. I knew this because Lexi came up to me with a leg that was about and inch and a half sticking out of her mouth. I pulled it out (while she growled at me... she NEVER does this... apparently starfish are like doggie crack) and it was soggy. Gross. Anyway, I found starfish parts and bile all over the kitchen floor and Miles sitting calmly with a "I don't feel good" look on his fuzzy little face. Other than being gassy and vomiting one time, it really did not seem to affect him. Lexi was not affected at all-- My guess is that she did not have a chance to eat any. She's usually the one with a sensitive stomach.
The starfish they ate was not one of those prickly orange ones. It was one of the smooth white ones. I was actually more worried there was some sort of preservative or something on it.
Oh-- And PS-- The National Animal Poison Control will cost you $60 to ask a question.