Fig. 1

Claw-associated protrusion in Xenopus tropicalis. a, b, Feet of an adult X. tropicalis (Nigerian A line) female (a) and male (b) with the claw-associated protrusion (inset). c, d, Feet of an X. tropicalis (Ivory Coast line) female (c) and male (d) that exhibit a clawed protrusion (inset). e–h, Feet of an adult X. laevis (e, f) and X. borealis (g, h) female and male with a tiny clawless protrusion (inset). Scale bar in a–h: 10 mm. Images are in ventral view in a–h. i–l, Bone and cartilage staining of the protrusion in X. tropicalis froglet (i) and adult (j) and the prehallux in X. laevis froglet (k) and adult (l). Scale bars: 200 μm in i, k and 1 mm in j, l. Images are in anterior view in i–l