heterochrony

noun

het·​er·​och·​ro·​ny -ˈräk-rə-nē 

plural heterochronies

1

: deviation from the typical embryological sequence of formation of organs and parts as a factor in evolution

2

: irregularity in time relationships

specifically : the existence of differences in chronaxies among functionally related tissue elements

heterochronous

-ˈräk-rə-nəs 

adjective