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Welcome to this special edition of our journal. This issue brings together the historical accounts of fifteen major museum based molluscan collections in the U.S., in addition to an introductory article prepared by curators, collection managers, and collection associates involved in the project. Throughout its 139-year existence, The Nautilus has endeavored to promote collection-based malacological research, so it is only natural that the journal would be the vehicle to disseminate this “historical” compilation. The articles are an outcome of the National Science Foundation-sponsored Thematic Collections Network (TCN) grants collectively known as Mobilizing Millions of Mollusks of the Eastern Seaboard (ESB). Each tells the story of an institutional mollusk collection from its earliest days to its present involvement in community-wide efforts. The introductory article reflects on the changing roles of U.S. malacological collections in a digital world, summarizes common needs and concerns, and points to the uniqueness and innovative nature of the ESB project. The editors want to acknowledge the indispensable assistance of the following peer reviewers, many of whom reviewed more than one manuscript in the course of this work: Arthur E. Bogan, Christopher Boyko, Eugene V. Coan, Kevin Cummings, Emilio F. García, Daniel Graf, Lindsey Groves, M. G. Harasewych, Alan Kabat, Rafael Lemaitre, Charles Lydeard, Paula M. Mikkelsen, Aydin Örstan, Shirley Pomponi, Carrie Schweitzer, Elizabeth K. Shea, Leslie Skibinski, John Slapcinsky, Ángel Valdés, and some others who preferred to remain anonymous. This assemblage of historical accounts could only come to fruition thanks to the cooperative and collegial environment of the ESB consortium; we hope that you find as much enjoyment reading these narratives as we did organizing and editing them. Support for this publication under National Science Foundation award DBI-2001510 is gratefully acknowledged. 

Abstract Against a background of the climate and biodiversity crises, there is an urgent need for robust and citable biodiversity information for policy and management decisions. Species are fundamental units of biodiversity and underpin communication in biology. Delineating, describing, and naming species provide the foundation for tracking biodiversity. Taxonomists recognise over 2 million described species, the scientific names of which follow provisions of codes of nomenclature, providing stability for communication about biodiversity. However, described species represent only a fraction of global biodiversity. Current advances in the fields of molecular biology and the growing use of image-based identifications have resulted in an explosion of informal species names globally, herein referred to as temporary names, increasing the rate of discovery of undescribed species and cryptic species complexes. We define two categories of temporary names: Type 1 names that are delineated in a local context but not further assessed; and Type 2 names that have been taxonomically assessed and recognised as either new or part of an unresolved species complex. We explore the different types and uses of temporary names, indicate how they can be managed in a robust and standardised manner and demonstrate how biodiversity databases, such as WoRMS, can be expanded to allow the tracking of both formal and informal scientific names. We propose a solution for the expanding problem of temporary names by defining and recommending the addition of Type 2 temporary names to nomenclatural databases such as WoRMS. We provide practical recommendations on how such names should be selected for entry and then entered to databases in a standardised way. These recommendations are a small step forward, but their broad adoption would support the robust integration of informal and formal taxonomies. 

Among biocollections, mollusks are a particularly powerful resource for a wide range of studies, including biogeography, conservation, ecology, environmental monitoring, evolutionary biology, and systematics. U.S. mollusk collections are housed in stand-alone natural history museums, at universities, and in a variety of governmental and non-governmental institutions. Differing in their histories, specializations, and uses, they share common needs for long-term development, and collectively contribute to biodiversity knowledge at regional, national, and global scales. Commitment by dedicated staff, collectors, and volunteers, institutional investments, philanthropy, and governmental funding have built and maintained these collections and their support infrastructure. Efforts by the North American malacological collection community since the early 1970s led to coordination in database design but left the data isolated in individual institutions. Collection digitization developed through a combination of individual/institutional initiatives and federally supported projects funded by the National Science Foundation (NSF) and the Institute of Museum and Library Services (IMLS). Advances in digital technology enabled the shift toward nationally and globally unified collections. Networking and collaboration were greatly accelerated by NSF’s Advancing Digitization of Biodiversity Collections (ADBC) program, which created a central coordinating organization (iDigBio) and funded Thematic Collections Network (TCN) projects. One such TCN was developed to mobilize nearly 90% of the known U.S. museum-collections-based data of the U.S. Atlantic and Gulf coasts (Mobilizing Millions of Marine Mollusks of the Eastern Seaboard—ESB). The project, involving 16 museum collections (plus the Smithsonian Institution as federal partner), combines data from approximately 4.5 million specimens collected from the ESB region and makes them available to the TCN portal InvertEBase and other aggregators such as iDigBio and GBIF. In addition to fostering community and expanding the corpus of available digitized mollusk records through new data entry and georeferencing (GEOLocate, CoGe) and standardizing taxonomy, the project drove key innovations for the invertebrate collections community. For instance, it worked with the Biodiversity Information Standards (TDWG) group to create a new Darwin Core standard term, “Vitality”, expanded GEOLocate to support complex geospatial types, integrated global elevation and bathymetric datasets directly into georeferencing workflow, and developed various education and outreach public outreach products. Synthesizing from the 15 following articles with individual histories of ESB-participating mollusk collections, several topics are discussed—such as what defines a “good” mollusk collection in the digital age and the importance of federal support for this national resource. 

Analyses of evolutionary dynamics depend on how phylogenetic data are time-scaled. Most analyses of extant taxa assume a purely bifurcating model, where nodes are calibrated using the daughter lineage with the older first occurrence in the fossil record. This contrasts with budding, where nodes are calibrated using the younger first occurrence. Here, we use the extensive fossil record of bivalve molluscs for a large-scale evaluation of how branching models affect macroevolutionary analyses. We time-calibrated 91% of nodes, ranging in age from 2.59 to 485 Ma, in a phylogeny of 97 extant bivalve families. Allowing budding-based calibrations minimizes conflict between the tree and observed fossil record, and reduces the summed duration of inferred ‘ghost lineages’ from 6.76 billion years (Gyr; bifurcating model) to 1.00 Gyr (budding). Adding 31 extinct paraphyletic families raises ghost lineage totals to 7.86 Gyr (bifurcating) and 1.92 Gyr (budding), but incorporates more information to date divergences between lineages. Macroevolutionary analyses under a bifurcating model conflict with other palaeontological evidence on the magnitude of the end-Palaeozoic extinction, and strongly reduce Cenozoic diversification. Consideration of different branching models is essential when node-calibrating phylogenies, and for a major clade with a robust fossil record, a budding model appears more appropriate.