Would a trilobite count as a chelicerate?

Although the thymus is shrinking with age, it is still functional in adults, thereby this statement is incorrect  

Explanation:

The thymus is a specialized primary lymphoid organ that has a key role in the production and maturation of T cells (i.e., thymus-derived cells). The thymus grows until puberty, but during adulthood, this vital organ starts to shrink, a process known as 'thymic involution'. During all life, the thymus plays roles in immunity and autoimmunity. The thymus produces progenitor cells that mature into T-cells, which are one of the main components of the adaptive immune system. These cells function by killing infected/sick cells (for example, cancer cells), by activating other immune cells, by synthesizing signaling molecules (i.e., cytokines), etc.