Lepthoplosternum

The type species for this genus is Callichthys pectoralis. The name is derived from the Greek leptos, meaning "thin", the Greek hoplon, meaning "weapon", and the Greek sternon, meaning "chest" or "sternum".[1]

L. stellatum and L. ucamara are hypothesized to form a partially unresolved polytomy with L. pectorale and L. beni, which are sister-species to each other. L. tordilho is sister to these four species and L. altamazonicum is the most basal species.[2]

There are currently six recognized species in this genus:[1]

• Lepthoplosternum altamazonicum R. E. dos Reis, 1997
• Lepthoplosternum beni R. E. dos Reis, 1997
• Lepthoplosternum pectorale (Boulenger, 1895)
• Lepthoplosternum stellatum R. E. dos Reis & Kaefer, 2005
• Lepthoplosternum tordilho R. E. dos Reis, 1997
• Lepthoplosternum ucamara R. E. dos Reis & Kaefer, 2005

Lepthoplosternum is widely distributed in cis-Andean South America south of the Orinoco River basin.

Lepthoplosternum species usually inhabit lentic or slow flowing water bodies and are often associated with marginal or floating vegetation.[2] L. ucamara has even been found in hypoxic conditions.[2] However, the type locality of L. stellatum is a stream, permanently flowing and well oxygenated.[2]

Lepthoplosternum species are the smallest callichthyines (maximum standard length 60.3 mm) and are easily recognized by two synapomorphies: the lower lip with deep medial notch and a small, additional lateral notch forming fleshy projections on each side; and a single unbranched ray preceding the branched ones on the anal fin.[2]