The phrase "pectoral fins" refers to the fins located on the sides of a fish's body, around the chest area. These fins help the fish with stability, balance, and steering while swimming. Full definition
To determine whether shifts in the balance of anterior and posterior field occurred during fin - to - limb evolution, Onimaru, postdoctoral researcher currently at Sharpe's lab (CRG), and his colleagues carefully compared the expression, function and regulation of genes involved in anterior - posterior patterning in pectoral fins of catsharks, with those of mice. (sciencedaily.com)
We hypothesise that the medial orientation of the forces on pectoral fins would result in unreasonably high bone stresses in early amphibious fish with fins, which would explain why the evolutionary invasion of land by vertebrates was accomplished instead by tetrapods with limbs with digits.» (sciencedaily.com)
They found that, in pectoral fin of catshark embryos, Gli3 expression was intensified posteriorly, and the balance of the anterior and posterior fields was shifted. (sciencedaily.com)