A new turtle: Chelus orinocensis

The mata mata turtle is a large (45 cm, up to 15 kg) freshwater turtle found in South America, mostly in the in the Amazon and Orinoco basins.  They have a very distinct look and are therefore available in the exotic pet trade, quite expensive to obtain. 

These turtles are carnivorous and predominantly feed at night in muddy water with limited visibility. However, they have very good eyesight with eyes that reflect light, similar to other nocturnal reptiles. 

The species name of the new discovery refers to the Orinoco drainage as its core distribution range. 

For the experts: The matamata is one of the most charismatic turtles on earth, widely distributed in northern South America. Debates have occurred over whether or not there should be two subspecies or species recognized due to its geographic variation in morphology. Even though the matamata is universally known, its natural history, conservation status and biogeography are largely unexplored. In this study we examined the phylogeographic differentiation of the matamata based on three mitochondrial DNA fragments (2168 bp of the control region, cytochrome oxidase subunit I, and the cytochrome b gene), one nuclear genomic DNA fragment (1068 bp of the R35 intron) and 1661 Single Nucleotide Polymorphisms (SNPs). Our molecular and morphological analyses revealed the existence of two distinct, genetically deeply divergent evolutionary lineages of matamatas that separated in the late Miocene (approximately 12.7 million years ago), corresponding well to the time when the Orinoco Basin was established. As a result of our analyses, we describe the genetically and morphologically highly distinct matamata from the Orinoco and Río Negro Basins and the Essequibo drainage as a species new to science (Chelus orinocensis sp. nov.). Chelus fimbriata sensu stricto is distributed in the Amazon Basin and the Mahury drainage. Additionally, the analyses revealed that each species displays phylogeographic differentiation. For C. orinocensis, there is moderate mitochondrial differentiation between the Orinoco and the Río Negro. For C. fimbriata, there is more pronounced differentiation matching different river systems. One mitochondrial clade was identified from the Amazon, Ucayali, and Mahury Rivers, and another one from the Madeira and Jaci Paraná Rivers. The C. orinocensis in the Essequibo and Branco Rivers have haplotypes that constitute a third clade clustering with C. fimbriata. Phylogenetic analyses of the R35 intron and SNP data link the matamatas from the Essequibo and Branco with the new species, suggesting past gene flow and old mitochondrial introgression. Chelus orinocensis is collected for the pet trade in Colombia and Venezuela. However, neither the extent of the harvest nor its impact are known. Hence, it is crucial to gather more information and to assess its exploitation throughout its distribution range to obtain a better understanding of its conservation status and to design appropriate conservation and management procedures.