Syndactyly type 1 (SD1), also named zygodactyly in the past, is a distal limb malformation characterized by complete or partial webbing between the 3th and 4th fingers and/or the 2nd and 3rd toes. The disease is Monarch Disease Ontology entry MONDO_0008512 (syndactyly type 1). Also known as: syndactyly, type 1, with or without craniosynostosis.