A revision ofPlesiobaena(Testudines: Baenidae) and an assessment of baenid ecology across the K/T boundary

Abstract

Over the course of the last two decades, the baenid taxonPlesiobaenahas typically been thought to consist of two named species,Plesiobaena antiqua(Campanian) andPlesiobaena putorius(Paleocene), along with an unnamed species from the Maastrichtian, but the interrelationship of these three taxa was never explored in an explicit phylogenetic context. Herein we present or re-describe a number of relevant specimens and provide a cladistic analysis of Baenidae using species only as terminal taxa. The phylogenetic analysis clearly reveals thatPlesiobaenain the traditional sense is a paraphyletic assemblage relative to the clade formed byGamerabaena sonsallaandPalatobaenaspp., thus demanding some nomenclatural adjustments. In particular,Plesiobaena putoriusis moved to a new genus,Cedrobaena, and the unnamed taxon from the Maastrichtian is formally namedPeckemys brinkman.Many of the newCedrobaena putoriusandPeckemys brinkmanspecimens described herein were found at the Turtle Graveyard locality in Slope County, North Dakota, along with four other turtle taxa, increasing the turtle diversity of this locality to at least six taxa. Although this indicates that Turtle Graveyard is the world's most diverse fossil turtle thanatocoenosis, a comparable diversity is found in modern river systems in the southeastern United States today. Our phylogenetic analysis indicates that seven out of nine latest Cretaceous baenid turtle lineages survived into the Paleocene, four of which are interpreted as being durophagous.