The initiative to produce a comprehensive global checklist of all hornworts and liverworts began at a workshop held at the Field Museum in 2009.

Bringing together specialists from around the world, the project aimed to synthesize existing knowledge of hornwort and liverwort taxonomy and nomenclature. As the work progressed, it became clear that the task was far more extensive than initially anticipated. Numerous nomenclatural issues were uncovered, and many unresolved taxonomic questions were identified that required further investigation.

To address these challenges, the collaborators published 74 papers in the Notes on Early Land Plants Today series (see ELPT Publications), involving 41 authors from 18 countries. These contributions resolved many nomenclatural problems and provided a framework for a more stable and consistent classification.

The culmination of this international effort was the publication of the World Checklist of Hornworts and Liverworts in 2016 (Söderström et al. 2016, PhytoKeys 59: 1–828). This landmark work represented the first comprehensive global synthesis of hornwort and liverwort diversity, recognizing 7,486 accepted species, 398 genera, and 92 families.

ELPT builds upon this foundation by documenting and discussing subsequent taxonomic and nomenclatural developments. The current platform provides updated concepts and interpretations for individual taxa, reflecting ongoing research and advances in our understanding of early land plant diversity.