childrens chapter book about an iguanadon family

I’m looking for a small softback chapter book that I got at a museum as a kid in the late aughts/early tens. I think the word “red” may have been in the title, as well as a word like rock or sand. The book took place in prehistoric times and centered around the eldest son of a small iguanadon family.

The son has two sisters and at the climax he saves one of them from a t-rex. The family is trying to defend their herbavore community, and the iguanadons often dig their “thumbs” into the dirt before they fight. I’m pretty sure they measure time by moons too.

Thank you for the help! I really hope I didn’t just dream this book up lol