67 (1): 1 – 122 © Senckenberg Gesellschaft für Naturforschung, 2017. 30.6.2017 A Systematic Review of the Turtle Family Emydidae Michael E. Seidel1 & Carl H. Ernst 2 1 4430 Richmond Park Drive East, Jacksonville, FL, 32224, USA and Department of Biological Sciences, Marshall University, Huntington, WV, USA; [email protected] — 2 Division of Amphibians and Reptiles, mrc 162, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 200137012, USA; [email protected] Accepted 19.ix.2016. Published online at www.senckenberg.de / vertebrate-zoology on 27.vi.2016. Abstract Family Emydidae is a large and diverse group of turtles comprised of 50 – 60 extant species. After a long history of taxonomic revision, the family is presently recognized as a monophyletic group defined by unique skeletal and molecular character states. Emydids are believed to have originated in the Eocene, 42 – 56 million years ago. They are mostly native to North America, but one genus, Trachemys, occurs in South America and a second, Emys, ranges over parts of Europe, western Asia, and northern Africa. Some of the species are threatened and their future survival depends in part on understanding their systematic relationships and habitat requirements. The present treatise provides a synthesis and update of studies which define diversity and classification of the Emydidae. A review of family nomenclature indicates that RAFINESQUE, 1815 should be credited for the family name Emydidae. Early taxonomic studies of these turtles were based primarily on morphological data, including some fossil material. More recent work has relied heavily on phylogenetic analyses using molecular data, mostly DNA. The bulk of current evidence supports two major lineages: the subfamily Emydinae which has mostly semi-terrestrial forms ( genera Actinemys, Clemmys, Emydoidea, Emys, Glyptemys, Terrapene) and the more aquatic subfamily Deirochelyinae ( genera Chrysemys, Deirochelys, Graptemys, Malaclemys, Pseudemys, Trachemys). Within subfamilies, some generic relationships have become well defined, supporting sister group relationships (e.g. Emydoidea + Emys, Malaclemys + Graptemys, and Trachemys + Graptemys/ Malaclemys). There is also strong evidence that Glyptemys and Deirochelys are outgroups (early sister lineages) to all of the other taxa in their respective subfamilies. The phylogenetic position of other genera (e.g. Clemmys, Chrysemys, Actinemys) remains enigmatic or controversial. Similarly, many species relationships have been clarified within recent decades, but several remain poorly resolved such as those belonging to Pseudemys, Trachemys, and Terrapene. Overall, our systematic knowledge of emydid turtles has rapidly progressed and ongoing studies are targeting broader and more comprehensive sampling of populations. Key words Emydidae, Turtles, Systematics, Phylogeny, Taxonomy, Actinemys, Chrysemys, Clemmys, Deirochelys, Emydoidea, Emys, Glyptemys, Grapt emys, Malaclemys, Pseudemys, Terrapene, Trachemys. Contents Prologue ........................................................................................................................................................................ 2 Introduction ................................................................................................................................................................... 3 Early Taxonomic Recognition and Family Assignments .............................................................................................. 3 Nomenclatural History of the Family Emydidae .......................................................................................................... 8 Birth of a Modern Restricted Family Emydidae RAFINESQUE, 1815 ............................................................................ 12 The Relationship Between Deirochelys and Emydoidea ............................................................................................ 18 Two Major Phyletic Lines of Emydids ....................................................................................................................... 20 ISSN 1864-5755 1 Seidel, M.E. & Ernst, C.H.: A Systematic Review of the Turtle Family Emydidae Subfamily Emydinae RAFINESQUE, 1815. The Semiterrestrial Emydids ................................................................ 20 Emys DUMÉRIL, 1805 ...................................................................................................................................... 30 Actinemys AGASSIZ, 1857 ............................................................................................................................... 36 Clemmys RITGEN, 1828 .................................................................................................................................. 38 Emydoidea GRAY, 1870 ................................................................................................................................. 40 Glyptemys AGASSIZ, 1857 ............................................................................................................................... 41 Terrapene MERREM, 1820 .............................................................................................................................. 45 Subfamily Deirochelyinae AGASSIZ, 1857. The Aquatic Emydids ........................................................................ 49 Deirochelys AGASSIZ, 1857 ............................................................................................................................ 54 Chrysemys GRAY, 1844 .................................................................................................................................. 54 Graptemys AGASSIZ, 1857 .............................................................................................................................. 57 Malaclemys GRAY, 1844 ................................................................................................................................ 67 Pseudemys GRAY, 1856a ................................................................................................................................ 68 Trachemys AGASSIZ, 1857 .............................................................................................................................. 77 Epilogue ...................................................................................................................................................................... 91 Acknowledgments ....................................................................................................................................................... 92 References ................................................................................................................................................................... 93 Table 1. Extant Taxa Assigned to the Family Emydidae .......................................................................................... 117 Glossary of Currently Used Scientific Names for Living Turtles in the Family Emydidae ..................................... 120 Prologue Defining diversity and developing a reliable classifica- SPINKS et al., 2016). Nevertheless, morphology continues tion system for organisms is more important today than to be important in classifying organisms, considering that ever before. Natural habitats throughout the World are the vast majority of taxa are diagnosed by their pheno- threatened by expanding human populations and in- typic structures. Systematists now rely heavily on phylo- dustrialization. Stability of our ecosystems depends on genetic methods, and certainly turtle taxonomists are no maintaining species diversity, which can only be mea- exception. It is clear that defining ancestral relationships sured by a reliable taxonomy. As a group of vertebrate is critical to the development of a natural classification animals, turtles (order Testudines) have been especially system. impacted (TUrtLE TAXONOMY WORKING GROUP, 2014). The family Emydidae is the largest group of turtles in Turtle populations are declining throughout the World, the New World. It has a rich history of classification over primarily due to habitat loss and human exploitation. the last two centuries, including extensive revision of spe- Many turtle species are extremely vulnerable due to their cies and genera. Thus it provides a good example of the restricted geographic distribution, small population size, challenges turtle systematists face. As authors (M.E.S. long generation time, and low fecundity. Understanding and C.H.E.), we have research experience with historical systematic relationships and developing a stable taxon- and current taxonomic problems of this group. In review- omy for turtles is crucial to promoting their protection ing the systematics of Emydidae, we provide an account and survival. of how approaches to classification have developed over In modern times, the discipline of systematics entails the years, and an update on the current taxonomic status the study of diversity and relationships among organ- of these turtles. Thus, our goal is to provide a histori- isms, reflecting the results of evolution. Taxonomy is the cal perspective and summary for future investigators and theory and practice of describing, naming, and ordering students of emydid classification. We have not included groups of organisms (taxa). It is often viewed as the prod- formal synonymies, detailed species descriptions, or geo- uct of systematics. The collective discipline