Since 2011 I have been involved in the GARD project (http://www.gardinitiative.org/index.html) led by Shai Meiri. For this project I assembled a global dataset of the extant (and recently extinct – after ~1500AD) turtles and crocs of the world. This dataset included information on their distribution, phylogeny, ecology, morphology, life-history and physiology. This dataset was included in the analyses of several studies and I am doing my best to periodically update it. I view turtles as an especially important taxon to research considering its ancient history, great biological diversity, and poor conservation status.
The turtle data has been included in several studies of global patterns of terrestrial vertebrates, including body size patterns (of turtles here, and of reptiles here), turtle ecology (here), reptile distributions (here and here), conservation studies (here and here), and life history studies (here and here).