Most species of the frog genus Leptodactylus occur in South America, and all authors who have treated the zoogeography of the genus have concluded that it originated somewhere in South America (e.g., Savage 1982). Savage (1982,518) summarized the historical herpetofaunal units of the Neotropics as follows: "All evidence points to an ancient contiguity and essential similarity of a generalized tropical herpetofauna that ranged over tropical North, Middle, and most of South America in Cretaceous-Paleocene times. Descendents of this fauna are represented today by the South and Middle American tracks (Elements). To the north of this fauna ranged a subtropical-temperate Laurasian derived unit, today represented by the Old Northern Element (track). By Eocene, northern and southern fragments of the generalized tropical units had become isolated in Middle and South America, respectively. Differentiation in situ until Pliocene produced the distinctive herpetofaunas that became intermixed with the establishment of the Isthmian Link."
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Heyer, W. R., R.O. de Sá, and S. Muller. 2005. The enigmatic distribution of the Honduran endemic Leptodactylus silvanimbus (Amphibia: Anura: Leptodactylidae). In M. A. Donnelly, C. Guyer, & M. H. Wake (editors), Ecology and Evolution in the Tropics: A Herpetological Perspective. Chapter 4, pages 81-101, University of Chicago Press. https://press.uchicago.edu/ucp/books/book/chicago/E/bo3534562.html