first record from Paraguay:
Corydoras undulatus Regan, 1912

published in:
Bono, A., L.F.C. Tencatt, F. Alonso, P. Lehmann (2019):
Redescription of Corydoras undulatus Regan, 1912 (Siluriformes: Callichthyidae), with comments on the identity of Corydoras latus Pearson, 1924.
PLoS ONE 14(1): e0211352. 24 p.

abstract (from publication):
A redescription of Corydoras undulatus Regan, 1912 is presented. The original description of C. undulatus is very succinct, as is its diagnosis, which is based only on external morphology. Additional information in the scientific literature on this species is scarce. Specimens from the distribution area of this species were analyzed; Parana´ and Paraguay river basins in Argentina, Uruguay river basin in Argentina, Brazil and Uruguay, and the Laguna dos Patos system in Brazil. Morphological analysis, principal component analysis (PCA), meristic comparison and osteological description were performed. Corydoras undulatus can be distinguished from its congeners mainly by having the following combination of characters: mesethmoid short, with anterior tip short, smaller than 50% of the entire bone length; posterior margin of the pectoral-fin spine with nearly all serrations directed towards origin of spine; pectoral-fin spine with conical serrations; and its peculiar color pattern. The analysis of the material from the different basins did not indicate relevant morphological differences, suggesting that the species presents a wide distribution in La Plata and Laguna dos Patos drainages. The shared geographic distribution between these two systems is also present in other fish species. The current work presents data about the type locality, taxonomy, osteology, distribution and ontogenetic variation of color pattern in C. undulatus. Comments on the identity of a very similar congener, Corydoras latus, will also be provided.

remarks (from publication):
Corydoras undulatus is known from the Paraguay River basin in Paraguay and Argentina, Paraná River basin in Argentina, in the Uruguay river basin in Uruguay, Argentina and Brazil and the Laguna dos Patos in Rio Grande do Sul, Brazil.
After revising the pictures of C. undulatus corresponding to lots deposited in the Swedish Museum of Natural History from the Paraguay River drainage in Paraguay, we conclude that those specimens probably correspond to C. undulatus [catalog numbers: NRM 23550, NRM 31026, NRM 31483, NRM 33556, NRM 45056, NRM 45060 and NRM 65433].