There was an error in the supplementary data of Development (2018) 145, dev160945 (doi: 10.1242/dev.160945).

Two panels in Fig. S1 were reproduced from the supplementary material (Fig. S4) of an earlier paper, Development (2017) 144, 4522-4529 (doi: 10.1242/dev.153262).

The panels in Fig. S1 have been replaced. The images in both cases show the same genotype but, for one panel, at a slightly different stage (E10 as opposed to E10.5). The updated file is now available online at http://dev.biologists.org/content/145/18/dev160945.supplemental.

This error does not affect the conclusions of the paper. The authors apologise to readers for this mistake.