The first report of a large leptodactylid frog from Trinidad was made by R. R. Mole and F. W. Urich (1894) when they listed Leptodactylus pentadactylus as present. Thomas Barbour (1914) suggested it may have exterminated by over-hunting for human food. Barbour was at Harvard University's Museum of Comparative Zoology (MCZ) and in fact the musuem has a single specimen of a frog in the Leptodactylus pentadactylus Group (MCZ 8662) now recognized as L. knudseni Heyer from Trinidad. Its origin remains obscure because it lacks any other data. H. W. Parker compiled a list of Trinidad anurans in 1933 and included L. pentadactylus as present, but hypothesized that it may have been exterminated by the mongoose.
Frank Wonder, a mammal collector working on Trinidad in the late 1940's, collected several specimens of a large leptodactylid frog near Brickfield in central Trinidad.
In his now classic 1969 paper on Trinidad amphibians Julian Kenny reported Leptodactylus pentadactylus as present on Trinidad. based upon specimens he collected at five localities in Mayaro, as well as hearing it call it Nariva swamp. He also included a drawing of the tadpole and the photograph of an adult.
Morley Read was working on Trinidad in the 1980's and collected some large leptodactylids, as did I. By the late 1980's it was clear that a member of the Leptodactylus bolivianus-ocellatus group was living in Trinidad. A decade later, W. Ron Heyer identified some tadpoles thought to be from Tobago as belonging to the L. bolivianus-ocellatus Group. In my 1997 book I included accounts for Leptodactylus bolivianus and Leptodactylus knudseni; recognizing that knudseni was known from a single Trinidad specimen. No other specimens have been found to date.
In a recent paper Heyer and de Sa (2011) have revisited the leptodactylid frogs in the bolivianus Group, a group of species with a pair of distinct dorsolateral folds on the dorsum and well-developed lateral fringe on the toes. The bolivianus Group ranges from Costa Rica southward through Panama, extending across northern South America (east of the Andes) in the river valleys draining to the Caribbean, and throughout much of the Amazon basin with southernmost limits in the Bolivian departments of La Paz, Cochabamba, and Santa Cruz.
The authors analyzed variation in this complex of frogs throughout its geographic range and identified the Group to contain three species: L. bolivianus, L. insularum, and L. guianensis (a new species).
Barbour (1906) described Leptodactylus insularum from Saboga Island in the Gulf of Panama. Now, Heyer and de Sa have given its distribution as ranging from the mainland Pacific versant of Costa Rica, throughout lowland Panama, the Caribbean drainages of Colombia and Venezuela, and Trinidad.
Trinidad is exceptionally rich in leptodactylid frogs -eight species, and two of the species (knudseni and lineatus) are known from only one specimen each from the island; and one of the species is endemic (nesiotus) - and known only from the southwest peninsula. Note that other references show here can be found on the literature page.
Heyer WR, de Sa RO 2011 Variation, systematics, and relationships of the Leptodactylus bolivianus complex (Amphibia: Anura: Leptodactylidae). Smithsonian Contributions to Zoology 635:1-58.