ectrosyndactyly

https://doi.org/10.1351/goldbook.10637

Congenital absence or deficiency of one or more of the central digits of the hand or foot with fusion of the existing ones.

Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 747 [Terms] [Paper]