@article{cruz_shimabukuro-dias_oliveira_foresti_2011,  title={Karyotype description and evidence of multiple sex chromosome system X1X1X2X2/X1X2Y in Potamotrygon aff. motoro and P. falkneri (Chondrichthyes: Potamotrygonidae) in the upper Paraná River basin, Brazil},  volume={9},  ISSN={1679-6225},  url={https://doi.org/10.1590/S1679-62252011000100020},  DOI={10.1590/S1679-62252011000100020},  number={1},  journal={Neotropical Ichthyology},  publisher={Sociedade Brasileira de Ictiologia},  author={Cruz, Vanessa Paes da and Shimabukuro-Dias, Cristiane Kioko and Oliveira, Claudio and Foresti, Fausto},  year={2011},  month={Mar},  pages={201–208} }