Origin, Evolution and Biogeographic History of South American Turtles

Turtles (Testudinata) are arguably among the most enigmatic groups of living vertebrates. From a temporal and ecological standpoint, turtles must be considered a compelling evolutionary success story, because the turtle bauplan has persisted since the Late Triassic and because turtles are conspicuous faunal elements in most warm terrestrial and aquatic habitats to this very day. Given that turtles typically live in environments in which sediments are deposited (i.e., flood plains, rivers, swamps, and oceans), the fossil record of the group is generally thought to be excellent. However, only few attempts have been made to synthesize the evolutionary history of turtles beyond the regional scale. In the book titled “Origin, Evolution and Biogeographic History of South American Turtles,” de la Fuente, Sterli, and Maniel summarize the known record of turtles from the South American continent. The book has seven chapters. The first, introductory chapter provides a taxonomic synopsis of all turtles known from South American, both extant and extinct, and draws the insightful conclusion that the diversity of most groups correlates with the timing of their origin or arrival on the South American continent. Despite its title, this chapter does not serve as an introduction to the book, but rather as its synopsis. The following six chapters are primarily organized by taxonomic groups. Chapter 2 is dedicated to aquatic crown cryptodires (i.e., pond turtles, mud and snapping turtles, and soft-shelled turtles), whereas chapter 3 is focused on terrestrial crown cryptodires (i.e., tortoises). Chapter 4 and 5 summarize the taxonomy of chelid and pelomedusoid pleurodires (side-necked turtles), respectively. Finally, chapter 6 is dedicated to meiolaniiform turtles (a group of extinct stem turtles that includes the perplexing cow-horned turtles), whereas chapter 7 summarizes most stem turtle lineages from the Triassic and Jurassic. The book is almost entirely focused on taxonomy and biogeography and is notable for listing all currently recognized fossil and living turtles. All higher taxonomic units are characterized in terms of their global taxonomic composition, their global biogeographic distribution, and the reader is referred to the most important morphological and molecular phylogenetic hypothesis. The authors meticulously provide for all 82 valid species that they recognize, both extinct and extant, the type specimen, spatial and temporal distribution (including highly useful map), a citation for the most recent definition or diagnosis, and, finally, a summary of the most important taxonomic debates. Each chapter is concluded by a short discussion on the biogeographic history of each group. Although only little new evidence is provided throughout the book, I personally find these discussions to be particularly original, balanced, and insightful. A series of 15 grey art turtle images disperse the book, of which the 12 reconstructions of fossil turtles are especially noteworthy. Although the title of the book promises a comprehensive review of all turtles from the South American continent, it is apparent that marine turtles were omitted. I find this absence regrettable, because the omitted group of turtles is most certainly polyphyletic, the exact paleoecology of various fossil turtles is debatable, and inclusion would have only minimally expanded the magnitude of the book while providing a truly comprehensive record of turtles from this southern continent. In conclusion, this is only the second book to summarize the taxonomic literature of fossil turtles at the species level and at a continental scale and only the first such book to include all extant taxa as well. This volume is therefore an important resource for any neontologists or paleontologists interested in the evolution of turtles or South American faunas and will hopefully inspire the compilation of similar compendia from other continents in the near future.