Abstract

Euchelicerata is a diverse group encompassing Xiphosura, Chasmataspidida, Eurypterida, and Arachnida. Xiphosura represents an extant group with a rich fossil record dating back to the Ordovician period. Xiphosurans are often referred to as “living fossils” due to their seemingly unchanged morphology over millions of years. Numerous studies have contributed to the understanding of xiphosuran development, revealing changes in the timing and rate of their growth. These changes have been mainly associated with the freshwater invasion of early xiphosuran forms. However, limited research has been conducted to compare the developmental patterns of xiphosurans with other euchelicerates inhabiting aquatic environments.