Normal table of embryonic development in the Chinhai Spiny Newt Echinotriton chinhaiensis (Salamandridae).

Following standardized vertebrate embryonic staging criteria, this study establishes a normal developmental staging table for the critically endangered Chinhai Spiny Newt, Echinotriton chinhaiensis, a narrowly distributed salamandrid species endemic to Ningbo, Zhejiang Province, eastern China. At a constant temperature of 20 °C, the entire embryonic period from oviposition to hatching lasted approximately 31.4 days, and the full developmental process was subdivided into 36 sequential stages. Stages 1-17 encompassed cleavage and neurulation, whereas Stages 18-36 corresponded to organogenesis-including tail bud outgrowth, external gill development, eye formation, and limb differentiation-until hatching. We systematically documented the diagnostic morphological traits of key embryonic structures and generated a concise chronological schematic illustrating the complete 36-stage developmental sequence. Comparative analyses across caudate species revealed evident heterochronic developmental shifts. The unique ontogenetic characteristics of E. chinhaiensis likely represent adaptive modifications to its ephemeral breeding microhabitats. This refined staging system improves our understanding of amphibian embryonic developmental patterns, clarifies how phylogenetic constraints and ecological selection shape evolutionary developmental trajectories, and provides fundamental baseline data for future comparative ontogenetic studies and conservation efforts for this endangered newt.