Abstract: Hyomandibular is a paired and endochondral bone related to the upper part of the hyoid arch. Since it is present in very primitive to modern fishes, it is highly important in taxonomy. In this research, the early development of hyomandibular from one to 30 dph (day post hatching) has been studied. For this survey, 350 specimens of different ages were sampled from Nowchah, a village near Mashhad, Iran. Samples after anesthesia were fixed using buffered formalin and then the osteology was studied using the double staining protocol of Alcian Blue and Alizarin Red. The qualitative observations were converted to the quantitative data and then were analyzed by MTLAB software. Based on these results, the origin of this bone was endochondral and the time of presence was after its hatching. Finally its existence period was determined, while the ossification started from 13 dph and seems to be continued after 30 dph.

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