AbstractA standard development embryological series is the primary basis to organize information of any embryological study and is also used to determine the age of eggs and embryos in field conditions. In this article, we calibrate developmental series of the broad‐snouted caiman, Caiman latirostris, against an established series for Alligator mississippiensis. Morphometric measures and extend of the opaque‐shell banding were also related to embryo age. In earlier stages, external morphological features alone can account for embryo age, but we suggest that morphometric measurements should be introduced later in the development. Unlike morphologic and morphometric attributes, the opaque patch was not a useful age predictor. As expected, a close correlation between embryonic development of C. latirostris and A. mississippiensis was observed. genesis 46:401–417, 2008. © 2008 Wiley‐Liss, Inc.