Abstract
Sandownids are a group of Early Cretaceous-Paleocene turtles that for several decades have been only known by cranial and very fragmentary postcranial elements. Here I report and describe the most complete sandownid turtle known so far, including articulated skull, lower jaw and postcranial elements, from the Early Cretaceous (upper Barremian-lower Aptian, >120 Ma), Paja Formation, Villa de Leyva town, Colombia. The new Colombian sandownid is defined here as Leyvachelys cipadi new genus, new species and because of its almost identical skull morphology with a previously reported turtle from the Glen Rose Formation, Texas, USA, both are grouped in a single and officially (ICNZ rules) defined taxon. Phylogenetic analysis including L. cipadi supports once again the monophyly of Sandownidae, as belonging to the large and recently redefined Pan-Chelonioidea clade. The morphology of L. cipadi indicates that sandownids were not open marine turtles, but instead littoral to shallow marine durophagous dwellers. Leyvachelys cipadi not only constitutes the first record of sandowinds in South America, but also the earliest global record for the group.
Highlights
Pan-cryptodires represent globally distributed and highly diverse turtles with a wide spectrum of environmental adaptations and body-plan (e.g., Perez-Garcıa, 2012; Anquetin, Puntener & Billon-Bruyat, 2014; Jansen & Klein, 2014; Rabi et al, 2014; Tong et al, 2014; Anquetin, Puntener & Billon-Bruyat, 2015; Zhou & Rabi, 2015)
Phylogenetical considerations A strict consensus tree from 96 most parsimonious trees was found from the global phylogenetic analysis including all taxa and all characters (Fig. 7)
With the aim to obtain a better understanding of the phylogenetic relationship of sandownids among Testudines, a second analysis was run, obtaining 3 most parsimonious trees Tree length (TL):949, consistency index (CI):0.778, retention index (RI):0.325
Summary
Pan-cryptodires (sensu Joyce, Parham & Gauthier, 2004) represent globally distributed and highly diverse turtles with a wide spectrum of environmental adaptations (coastal-littoral, freshwater, and terrestrial) and body-plan (e.g., Perez-Garcıa, 2012; Anquetin, Puntener & Billon-Bruyat, 2014; Jansen & Klein, 2014; Rabi et al, 2014; Tong et al, 2014; Anquetin, Puntener & Billon-Bruyat, 2015; Zhou & Rabi, 2015). Anatomical and paleoecological interpretations of sandownids have suggested that they were durophagous and bottom-dwelling turtles, inhabiting near-shore shallow marine environments (Vineyard, 2009; Tong & Meylan, 2013); whether they were adapted to open marine conditions as other lineages of turtles, (see Cadena & Parham, 2015, for discussion about marine lineages of turtles), is still poorly supported This is due to the lack of limbs and any other postcranial found associated to skull material. The first one corresponds to a protostegid, recently described as the potentially oldest marine turtle Desmatochelys padillai Cadena & Parham (2015)
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