The Community of Practice framework has been used theoretically and empirically to describe the diverse ways people learn from one another through social interaction in a variety of specific contexts. To date, most research of this genre has favored investigating the community and domain constructs of the theory over the authentic practice construct. Those interested in recognizing and supporting science learning in non-school contexts across a lifespan are then limited in efforts to delineate how communities engage in domain-specific practice. This is especially relevant in the study of online environments which afford more democratic forms of participation. With the goal of adding to both theoretical and practical knowledge, this study explored practices that members enacted on a community-based website specific to the domain of paleontology. We used a multiple case study approach to provide comparative and contrasting narratives concerning the development of practice within an online, scientific community. Methods consisted of downloading data from the website, including members’ self-described attributes within member profiles, followed by their contributions to three of the website’s features: the forums, activity feed, and messages. An analytical framework which typified members based on their self-described attributes was applied, then members’ contributions were coded using an empirically based Communities of Practice framework. For one of the first times, we identified practice within an online, scientific community through comparing the contributions of three community members, finding that practice consisted of providing social support to other community members and having domain-based conversations.