A new species of Elachistocleis (Anura: Microhylidae) from the Brazilian Pantanal.A new species of from the Brazilian Pantanal is described. The new species differs from all other in having the following combination of characters: medium to large-sized species (26.9-40.3 mm); head length about 89% of head width; post-commissural gland poorly developed; dorsum in preservative (EtOH 70%) slightly rough, grayish, with minute, scattered white dots and a large, elongated dark gray spot on the mid-dorsum and posterior part of head; venter gray or brown with white spots separating dorsal and ventral regions; a single vocal sac dark gray; large, irregular, light cream spot on humerus; large, irregular light cream spots on groin; light cream, irregular stripe on posterior surfaces of thighs; and irregular, light cream spots on the proximal internal surface of each shank. This new species increases the number of Oval frogs for the state of Mato Grosso do Sul to four and demonstrates the value of the single the Maciço do Urucum are necessary to determine the diversity of the herpetofauna in that region. Keywords: biodiversity, Corumbá, Oval frogs, systematics, taxonomy.Resumo Uma nova espécie de Elachistocleis (Anura: Microhylidae) do Pantanal Brasileiro. Uma nova 40.3 mm); comprimento da cabeça com cerca de 89% da largura da cabeça; glândula pós-comissural 144 Phyllomedusa -16(2), December 2017 pobremente desenvolvida; dorso em preservativo (EtOH 70%) ligeiramente áspero, acinzentado, com pontos brancos pequenos e dispersos e uma mancha cinza escura alongada, grande no meio do dorso e na parte posterior da cabeça; ventre cinza ou marrom com manchas brancas separando as regiões dorsal e ventral; um único saco vocal cinza escuro; uma mancha creme claro grande e irregular no úmero; manchas creme claro grandes, irregulares na virilha; faixa creme claro irregular nas superfícies posteriores das coxas; e manchas creme claras irregulares na superfície interna proximal de cada do Sul para quatro e demonstra o valor da única área protegida em Corumbá para a conservação da biodiversidade e a importância de continuar as pesquisas de campo no Maciço de Urucum para determinar a diversidade da Herpetofauna.

We present an annotated list of anuran species found in the Parque Municipal de Piraputangas, a protected area of a semi-deciduous forest located in Corumbá, Mato Grosso do Sul, Brazil. Fieldwork was conducted three times per month between August 2012 and July 2013. We recorded 29 species from six families (Bufonidae, Dendrobatidae, Hylidae, Leptodactylidae, Microhylidae, and Phyllomedusidae), representing 30% of the anuran species known to occur in Mato Grosso do Sul and 50% of the anurans recorded in this state’s semi-deciduous forests. Microhylids, leptodactylids, and bufonids were associated with terrestrial substrates, whereas most hylids and phyllomedusids were found perched on vegetation. This study will fill gaps in the knowledge on the anuran fauna of the western border of the Pantanal and will serve as a basis for additional studies that are needed to understand how species respond to habitat loss or fragmentation, such as landscape conversions, commercial logging, or mining.