Redescription of the Pez Graso, Rhizosomichthys totae (Trichomycteridae), of Lago de Tota, Colombia, and aspects of cranial osteology revealed by microtomography

SCHAEFER, S.A. & L. FERNANDEZ

COPEIA

American Society of Ichthyologists and Herpetologists

Lugar: Estados Unidos; Año: 2009 p. 510 - 522

0045-8511

Rhizosomichthys totae, the Pez Grasso, greasefish, or runcho of Lago de Tota, Colombia, is known from ten specimens and thought to be extinct. The species is unique among trichomycterids in possessing remarkable rings of extensive adipose tissues surrounding the body. Although its internal anatomy is poorly known, diagnosis of Rhizosomichthys totae and taxonomic status within Trichomycteridae have not been questioned. Non-destructive reconstruction of the osteology of one paratype based on computed microtomography, combined with broad character surveys of representatives of other trichomycterid genera, formed the basis for a redescription of R. totae and revealed the presence of four additional autapomorphies involving features of the cranium, autopalatine, and branchiostegal rays. This evidence further confirms the membership of Rhizosomichthys within the putatively non-monophyletic subfamily Trichomycterinae. We evaluate in R. totae the characters serving to diagnose the genera presently included in the Trichomycterinae.