This species is also traded as 'hi-fin ram' 'Bolivian butterfly' or 'ruby crown cichlid' and is arguably a better choice for less-experienced aquarists than its congener M. ramirezi.
The genus Mikrogeophagus currently contains three recognised species. The third was described in 2022 from the upper Rio Guaporé drainage in Mato Grosso, Brazil. The other two are separated from one another in a geographical sense with M. ramirezi occurring in Venezuela and Colombia and M. altispinosus native to Bolivia and western Brazil. The latter is also a larger, less-colourful fish lacking blue iridescent markings on the fins, body and head.
The grouping has a confused taxonomic history with the correct placement and spelling of type species M. ramirezi a source of confusion for several decades prior to the publication of Kullander (2011). It was described as a member of the genus Apistogramma but later affiliated with the name Microgeophagus in an aquarium book by Hans Frey (1957) who did not provide diagnostic characters and only suggested it might be placed into that genus in the future.
The latter name did not achieve general acceptance until 1971 when Axelrod used it in a popular book about breeding aquarium fishes, although Klee (1971) rejected this and suggested that the species should instead be included in Geophagus. Kullander (1977) described the new genus Papiliochromis with P. ramirezi as type species, and in the same paper considered Microgeophagus to be an unavailable name without providing precise detail as to why.
Papiliochromis was accepted in both hobbyist and scientific literature until Bailey and Robins (1982)[4] concluded that Microgeophagus sensu Axelrod (1971) was the oldest available name for a cichlid genus with A. ramirezi as type species, and thus should be considered valid.
Géry (1983, 1986) argued that Microgeophagus sensu Frey (1957) is the oldest available name for the genus, while Allgayer (1985) considered Papiliochromis valid. Kullander (1998) used Mikrogeophagus, a name he considered the oldest available based on its inclusion as a valid name in Jeg har akvarium, a Danish language aquarium book published in 1968, with Microgeophagus sensu Frey (1957) an unavailable nomen nudum lacking both a diagnosis and type species.
The genus Mikrogeophagus is thus attributed to Jens Meulengracht-Madsen, 1968, who authored the relevant sections in the book (it was edited by Schiøtz and Christensen), but it is considered an 'involuntary' nomenclatural act because the author believed he was using an existing name.
Mikrogeophagus therefore became widely-accepted following Kullander (1998), although a number of authors evidently did not agree.
After a period of inactivity Isbrücker (2011) re-opened the issue and argued that Microgeophagus sensu Frey (1957) is actually the oldest available name for the genus, but this was definitively rejected by Kullander (2011) who published a detailed analysis of the different generic names that have been used for the species, the majority of which were derived from aquarium, rather than scientific, literature.
Although Mikrogeophagus is now generally accepted to be correct the species M. ramirezi commonly appears in older aquarium literature as Apistogramma ramirezi, Microgeophagus ramirezi, or Papiliochromis ramirezi.
Mikrogeophagus and a number of related genera are often included in the putative subfamily Geophaginae.
Kullander (1998) conducted a morphology-based phylogenetic study in which the neotropical Cichlidae was divided into six subfamilies of which the Geophaginae contained 16 genera divided among three ‘tribes’:
Acarichthyini - Acarichthys and Guianacara.
Crenicaratini - Biotoecus, Crenicara, Dicrossus and Mazarunia.
Geophagini - Geophagus, Mikrogeophagus, ‘Geophagus‘ brasiliensis group, ‘Geophagus‘ steindachneri group, Gymnogeophagus, Satanoperca, Biotodoma, Apistogramma, Apistogrammoides and Taeniacara.
Later molecular studies by Farias et al. (1999, 2000, 2001) resulted in the additions of Crenicichla and Teleocichla to the Geophaginae, a result supported by López-Fernández et al. (2005) who conducted the most detailed molecular analysis of the grouping to date including 16 of the 18 genera and 30 species.
However their conclusions regarding interrelationships between genera did vary somewhat from previous hypotheses and can be summarised by the following loosely-defined groups:
- a weakly-supported sister group relationship between Acarichthys and Guianacara.
- a well-supported 'Satanoperca clade' comprising Satanoperca, Apistogramma, Apistogrammoides and Taeniacara.
- a 'big clade' with Geophagus, Mikrogeophagus, ‘Geophagus‘ brasiliensis group, ‘Geophagus‘ steindachneri group, Gymnogeophagus, Biotodoma, Crenicara and Dicrossus.
- a 'crenicarine clade' with Biotoecus and Crenicichla.
No representatives of Teleocichla or Mazarunia were included in the study but the former is well-established as sisterto Crenicichla while the latter has grouped closely with Dicrossus and Crenicara in earlier works.
The other main conclusions of the paper are confirmation that Geophaginae is a monophyletic group exhibiting strong signs of having undergone rapid adaptive radiation (diversification of a species or single ancestral type into several forms that are each adaptively specialised to a specific environmental niche).
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