Catshark Pectoral Fin (IMAGE) Center for Genomic Regulation Caption Figure 1: This is a catshark pectoral fin and a mouse forelimb. (a) Skeletal pattern. In a catshark fin, three basal bones are connected to the pectoral girdle, whereas in a mouse limb, a single basal bone is connected to the body trunk. (b) Expression patterns of genes involved in anterior-posterior patterning of fins/limbs. The balance of anterior field (Alx4, Pax9-positive region) and posterior field (Hand2-positive field) shifted in between a catshark pectoral fin and a mouse forelimb. Credit Mikiko Tanaka, Tokyo Institute of Technology Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.