The stranding of 571 post-larval and juvenile Macroramphosus gracilis (Lowe, 1839) specimens on the shoreline of the Strait of Messina in spring 2025 allowed us to study their morphological features and how they change throughout development. This was also possible thanks to the rather broad size range (9–52 mm Standard Length) of the stranded specimens.

Individuals of this species were long mistaken for juvenile stages of the congeneric M. scolopax, from which they are clearly distinguishable by coloration and appearance, as well as by the morphometric relationships highlighted in the scientific literature. Careful observation and measurement of the specimens we examined allowed us to provide additional morphometric data on Macroramphosus gracilis, helping to bridge the knowledge gap due to the aforementioned historical confusion with M. scolopax.

Furthermore, we observed morphological characteristics not found in the existing literature to date, in particular the presence of dorsocephalic, supraorbital, supraopercular, and lateral spinules. The smallest individuals possessed spinules in all listed anatomical parts, while the largest (over 46 mm SL) lacked them entirely.

This evidence allowed us to establish different size classes, corresponding to various stages of post-larval development, highlighting how the various morphological changes (progressive disappearance of spinules, elongation of the beak and spiny ray of the dorsal fin) are consistent with the habitat shift during the development of M. gracilis, from hyponeustonic (larvae and post-larvae) to benthopelagic (adult individuals).