Distribution and Biogeography of Non-Marine Cretaceous Turtles

Abstract

During the Cretaceous, non-marine turtles show strong patterns of provincialism, mirroring the pattern of land masses resulting from the breakup of Pangea since the Jurassic. These patterns are a result of several factors, of which vicariancy and ecological controls on the distribution of groups of turtles are considered the most significant. The large scale patterns, such as the dominance of pleurodires in the southern land masses, including Africa, South America, and India, and the dominance of Cryptodires in the northern land masses cannot be strictly attributed to vicariancy because exceptions to both distributional patterns are present. The pleurodires in Europe and North America during the Late Cretaceous may reflect the removal of the barriers that prevented the terrestrial faunal interchange between the northern and southern continents. Two groups of cryptodires that occurred in the southern continents during the Cretaceous, the Meiolaniidae and Otwayemys, seem to reflect a widespread distribution of the very primitive cryptodires which were diverse prior to the breakup of Pangea in the Early or possibly Middle Jurassic. In Laurasia, three regions of turtle diversity can be identified, the North American region, the European region, and the Asian region. In the Early Cretaceous, North American region is dominated by members of the Paracryptodira, and the Asian region is dominated by members of the Eucryptodira. Europe includes taxa from both groups. In the Late Cretaceous, Eucryptodires become increasingly more abundant and diverse in North America. The Baenidae which are not found outside North America appears to be truly endemic to this region. Two groups of “modern,” non-marine cryptodires or Chelomacryptodira, the Testudinoidea and the Trionychoidea, appear to have an Asian origin. Both have their earliest record in the Neocomian of Japan.