A new genus and species of characid fish from the Amazon basin: the recognition of a relictual lineage of characid fishes (Ostariophysi: Cheirodontinae: Cheirodontini)

Abstract

Amazonspinther dalmata, a new miniature characid from the streams of rio Purus and rio Madeira, right bank tributaries of the rio Amazonas, is described as a new genus and species of the subfamily Cheirodontinae. The unique characters of the new genus and species are the three remarkable black blotches on the base of the dorsal, anal, and caudal fins, the anteriormost proximal radial of the anal fin with an anteriorly extended lamina entering the abdominal cavity, and the extremely elongate caudal peduncle. The reduced number of ventral procurrent caudal-fin rays (7-9), and the hemal spines of only posterior one, two, or sometimes three caudal vertebrae directly articulating with the ventral procurrent caudal-fin rays further diagnoses the new taxon from remaining genera of the tribe Cheirodontini. The results of a phylogenetic analysis strongly support a close relationship between A. dalmata and Spintherobolus in the tribe Cheirodontini on the basis of fifteen unambiguous synapomorphies. Ten of these characters, previously hypothesized as exclusive synapomorphies for Spintherobolus, were now also identified in Amazonspinther, such as the pattern of exposed neuromasts on the head, the presence of a second pseudotympanum anterior to the first pleural rib, and the nearly discoidal coracoid bone. A discussion about the phylogenetic position of the closely related fossil †Megacheirodon to Spintherobolus and Amazonspinther is also provided. Convergent characters shared between Amazonspinther and the characid Priocharax are discussed in relation to miniaturization. Biogeographical implications of the diversification of Amazonspinther, Spintherobolus, and Megacheirodon lineages are discussed.<br>Amazonspinther dalmata, um novo caracídeo miniatura de igarapés dos rios Purus e Madeira, afluentes da margem direita do rio Amazonas, é descrito como um novo gênero e nova espécie da subfamília Cheirodontinae. Os caracteres únicos ao novo gênero são as manchas pretas conspícuas na base das nadadeiras dorsal, anal e caudal, o radial proximal mais anterior da nadadeira anal com uma lâmina estendida anteriormente entrando na cavidade abdominal e o pedúnculo caudal extremamente alongado. Caracteres adicionais que diagnosticam o novo táxon dos demais gêneros da tribo Cheirodontini incluem o número reduzido de raios procorrentes caudais (7-9) e os espinhos hemais de somente uma, duas, ou às vezes três das vértebras caudais, diretamente articulados com os raios procorrentes caudais ventrais. Os resultados de uma análise filogenética suportam fortemente uma relação de proximidade entre A. dalmata e Spintherobolus na tribo Cheirodontini com base em quinze sinapomorfias não ambíguas. Dez destes caracteres foram previamente propostos como sinapomorfias exclusivas de Spintherobolus, mas agora são reconhecidos também em Amazonspinther, e.g. o padrão de distribuição de neuromastos expostos na cabeça, o segundo pseudotímpano anterior à primeira costela pleural e o coracóide aproximadamente discóide. Uma discussão a respeito da posição filogen...

Feeding ecology of Serrapinnus notomelas (Characiformes: Cheirodontinae) in small forest streams in the Machado River basin, Rondônia, Brazil

“…Over 1500 Characiformes species have been described to date . Although the subfamily Cheirodontinae is one of the best-known groups of Characidae in terms of phylogeny and taxonomy (Malabarba 2003;Bührnheim et al 2008), there is a dearth of studies on the ecology of this subfamily (Benitez and Súarez 2009), and most of the available information is on the biological aspects of Cheirodontinae species in southern Brazil (Santi-Rampazzo et al 2008;Benitez and Súarez 2009;Gonçalves et al 2011). (Eigenmann, 1915) shows ornamental importance (Regulatory Directive 001/2012-MPA/MMA) and contributes 0.0009% of the total ornamental fish exports of Brazilian inland waters caught in the states of Amazonas and Pará (IBAMA 2008).…”

Molecular phylogeny and biogeographic history of the Neotropical tribe Glandulocaudini (Characiformes: Characidae: Stevardiinae)

“…A relaxed clock with an uncorrelated lognormal distribution was used (Drummond et al, 2006); a starting tree was obtained from the Bayesian analysis; a macroevolutionary Birth-Death model for the diversification likelihood values; and under GTR+I+G model (as estimated in MrModeltest). Two calibration points were included based on fossil records of the characids †Paleotetra Weiss, Malabarba, Malabarba (Eocene-Miocene, Weiss et al, 2012) and †Megacheirodon unicus (Travassos, Santos) (Late Oligocene-Early Miocene, Malabarba, 1998;Bührnheim et al, 2008). According to Mirande et al (2013), the genus †Paleotetra is included in a clade who is closely related to ((Aphyocharacinae (Aphyoditeinae, Cheirodontinae)), Stevardiinae).…”

“…This estimated date was based on the mean of the minimum age of 30-25 Mya proposed to †M. unicus (Malabarba, 1998;Bührnheim et al, 2008), which was hypothesized as closely related to Spintherobolus by Bührnheim et al (2008). Forest (2009) was followed to choose the crown and stem groups.…”

A new stem fossil characid (Teleostei: Ostariophysi) from the Eocene-Oligocene of southeastern Brazil

“…These pores and grooves are associated to superficial neuromasts usually arranged in pitlines and constitutes a synapomorphy for the Characinae. Superficial neuromasts are further observed in other three unrelated characid groups: Astyanax hubbsi and A. mexicanus (Teyke, 1990), Coptobrycon bilineatus (Langeani & Serra, 2010) and as a synapomorphy of Spintherobolus (Weitzman & Malabarba, 1999) + Amazonspinther (Bührnheim et al, 2008). All these taxa, however, lack a supraorbital, are more deeply inserted in the phylogeny of the Characidae and cannot be hypothesized as closely related to †Bryconetes enigmaticus.…”