It appears that the name of the Neotropical Rattlesnake was updated from Crotalus durissus to simus.
A tiny, common Leptodactylid, Physalaemus pustulosus (the Pustuled thin-toed frog) could easily be mistaken for a toad (Bufonidae) because of its warty skin. It lacks obvious paratid glands, but the adult is so small (probably a maximum of 4-g) that it’s difficult to identify. The first ones I saw had fallen in a bucket-trap during the day and had dried out, so I mistakenly identified them as toadlets.
The males are easily identified by their blotchy, dark chin.
A tentative herp count from my four months in Costa Rica: 62 species. It may increase (or decrease) slightly as I add and update photographs with uncertain identification and scientific names from Savage and Bolanos (Zootaxa 2009). The majority of the herps discovered were reptiles, which makes sense, given my extended stay in the dry forest. I missed out on much of the phenomenal diversity of anurans and didn’t see a single salamander because they tend to be more diverse in wetter parts of the country. When I was in those areas (i.e., the Osa Penninsula), it was the dry season, so many of the herps were hiding out.