Bryconops gracilis

When it was originally described by German-American ichthyologist Carl H. Eigenmann in 1908, B. gracilis was named Creatochanes gracilis.^[3] It is still occasionally referenced under that name.^[8]

Eigenmann's original nomenclature retains an element of validity in the current day. This is because there are two subgenera in Bryconops, Bryconops and Creatochanes, and the latter draws from Eigenmann's work. However, B. gracilis belongs to the subgenus Bryconops, making its full name Bryconops (Bryconops) gracilis.^[6] It shares this subgenus with congener B. alburnoides, with which it has been confused in the past, but similar congener B. melanurus is in Creatochanes.^[9]

Bryconops gracilis is an iguanodectid (part of the family Iguanodectidae).^[10] This is a fairly recent classification, and was prompted by a review of the family Characidae in 2011 wherein the genera Bryconops, Piabucus, and Iguanodectes were all moved from Characidae to Iguanodectidae.^[11] Some sources still list B. gracilis as a characin.^[12]

The specific epithet gracilis means "slender" (note the similarity to the word "graceful"), and is in reference to the narrow, elongated body.^[13] It shares this specific epithet with multiple other species, such as Hemiodus gracilis and Pseudanos gracilis.^[14]

In terms of a common name, B. gracilis is sometimes called the "lambari",^[1] but this is a name that also applies to other small species of fish in nearby regions. These fish include Astyanax altiparanae,^[15] Bryconamericus lambari,^[16] and Deuterodon iguape.^[17] Otherwise, B. gracilis has no accepted common name.^[18]

Bryconops gracilis is native to Brazil, found only in the Tapajos river basin.^[19] Three of its congeners have also been described therein: B. durbinae, B. munduruku, and B. transitoria.^[9]

Though B. gracilis is currently listed as least concern by the International Union for the Conservation of Nature (IUCN),^[1] the Tapajos river is under constant threat of human impact. The water is sometimes so full of sediments kicked up by illegal mining that entire portions of the river turn entirely brown.^{[citation needed]} Factors like this place B. gracilis, as well as other species endemic to the area, under greater survival pressure.^[20]