What are examples of tectum?

As a professional in the field of cryptocurrency and finance, I'm often curious about the intersections between our industry and other areas of expertise. One such area that piques my interest is the field of biology, specifically the concept of 'tectum'. Could you provide me with some examples of what tectum refers to in biological contexts? Is it a specific structure, tissue, or perhaps a function? I'm interested in understanding how the term might apply to various organisms, from microbes to mammals. Your insights could help me make connections between finance and other fields, potentially leading to innovative approaches or applications.