Thank you and good questions. They didn't just sacrifice their mobility off the bat for the digging benefits down the road. They were already a fossorial species, and probably modestly adapted for that life-style. Their ribs began shifting and widening to serve as forelimb-anchors because that fit well with that particular lifestyle. The trade off was that it did make them slower, however since they spent the large amount of their time underground, speed was not the most pressing issue (it wasn't until turtles took to the water that we believe they started to compensate for their slow speed by developing a protective shell). So yes, they did sacrifice their speed, but it was to increase qualities that made their immediate life easier.
Buccal pumping probably evolved alongside the ribs. We still don't know exactly how that method of respiration arose (it's still up for debate) but it probably developed as the ribs were expanding and making normal respiration more difficult. I think it will be a while before we have an answer to that question.
You are viewing a single comment's thread from: