lol, now I hope Dr. Lundberg gets back to me as he is the one to split this species back in 2004.
This is what the abstract from his paper titled:
Brachyplatystoma capapretum: a New Species of Goliath Catfish from the Amazon Basin, with a Reclassification of Allied Catfishes (Siluriformes: Pimelodidae)
John G. Lundberg and Alberto Akama
Abstract
Brachyplatystoma capapretum n. sp., a pimelodid catfish from the Amazon River, is described and diagnosed by its fine, densely spaced outer jaw teeth and relatively few rows of straight, depressible inner teeth; juveniles with large dark blotches on and above lateral line; adults with exceptionally dark pigmentation dorsally, abruptly countershaded near lateral line; broad, shallowly forked caudal fin. The systematic position of the new species was investigated with a maximum parsimony phylogenetic analysis of morphological characters. The resulting cladograms identify a nested set of unambiguous characters supporting the following monophyletic groups and taxonomic recommendations. Brachyplatystomatini new tribe is established for Brachyplatystoma and Platynematichthys and supported by two synapormorphies: two-chambered gas bladder connected by paired lateral tubes; cleithrum with blade-like ventral crest between pectoral spine articulation and posterior process of cleithrum. The monotypic genera Goslinia and Merodontotus are placed in synonymy with Brachyplatystoma characterized here by two synapomorphies: suspensorium greatly expanded mediodorsally, forming a massive plate approaching parasphenoid; juveniles with greatly elongated caudal-fin filaments developed from single outermost, unbranched principal rays. Bleeker's genus group name Malacobagrus is employed as a subgenus within Brachyplatystoma to include B. filamentosum, B. capapretum, and B. rousseauxii. Monophyly of Malacobagrus is supported by five synapomorphies: adults developing extensive reticulated system of lateralis tubules on body; Weberian complex with thick, ventral bony platform at gas bladder attachment; subquadrangular shape of opercle; pectoral spine with sulcus along anterior edge; small, non-sutured endopterygoid. Two unique synapomorphies place B. capapretum and B. filamentosum together as sister species: juveniles with spots on and above lateral line; caudal peduncle subcircular in cross-section.
Not sure this abstract really helps any unless you plan on dissection to determine species. It does show that filamentosum and capapretum are sister species. Also they have their own subgenus with rousseauxii
