Exploring macroevolutionary patterns and processes using fossil records is vital to understanding how developmental drivers and ecological pressures shape biodiversity. Size is one of the most conspicuous organismal traits and serves as a crucial factor in determining how organisms interact with their environment, making patterns of animal body size evolution a focus of macroevolutionary research. Nevertheless, the macroevolutionary patterns of body size across numerous major metazoan clades and their constraining mechanisms remain enigmatic. Recently, Dr. SUN Zhixin, supervised by Professors ZHAO Fangchen and ZHU Maoyan from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), collaborated with Dr. ZENG Han (NIGPAS) and Pro. Douglas H. Erwin from the Santa Fe Institute to conduct a comprehensive study on body size evolution in trilobites, a highly representative group of fossil invertebrates. This research was published in Science Advances on May 2th, 2025.