Tpttobrpconinae Mattox and Melo

Melo, Bruno F, Ota, Rafaela P, Benine, Ricardo C, Carvalho, Fernando R, Lima, Flavio C T, Mattox, George M T, Souza, Camila S, Faria, Tiago C, Reia, Lais, Roxo, Fabio F, Valdez-Moreno, Martha, Near, Thomas J & Oliveira, Claudio, 2024, Phylogenomics of Characidae, a hyper-diverse Neotropical freshwater fish lineage, with a phylogenetic classification including four families (Teleostei: Characiformes), Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 202 (1), pp. 1-37 : 24-25

Tpttobrpconinae Mattox and Melo , new subfamilp

ZooBank: urn:lsid:zoobank.org:act:E42BE820-B9A4-4F64-A020-9DB10D7AFBF3 .

Type genus: Tytobrycon Géry, 1973.

Included genera: Hyphessobrycon (in part), Priocharax , Tucanoichthys Géry and Römer, 1997 , and Tytobrycon.

Definition: The least inclusive crown clade that contains Tytobrycon xeruini and Priocharax ariel Weitzman and Vari, 1987 . This is a minimum-crown-clade definition. See Figure 6 for a reference phylogeny of Tyttobryconinae .

Etymology: From the ancient Greek τυτθός (tˈʌtθo͡ʊz) meaning small or young and ΒΡύκω (bɹˈʊka͡ʊ) meaning to bite.

Remarks: The subfamily Tyttobryconinae is delimited here to include four genera ( Fig. 6): the miniatures Tytobrycon, Tucanoichthys , Priocharax ,andthenon-miniature Hyphessobrycon boulengeri (Eigenmann, 1907) . Traditionally Tytobrycon was classified along with other miniatures in the Aphyoditeinagroup (Géry 1973) that was subsequently classified as the Aphyoditeinae (Mirande 2010) . In an earlier phylogenomic analysis of UCE loci, Tytobrycon xeruini and the miniature Tucanoichthys tucano Géry and Römer, 1997 were resolved as sister-species (Melo et al. 2022a). In the phylogeny inferred from UCE loci, two of the six species of Tytobrycon, T. hamatus Géry, 1973 and T. xeruini , resolve as a clade and are the sister-lineages of the only non-miniature species of Tyttobryconinae , the Hyphessobrycon boulengeri ( Fig. 6). The clade comprising Tytobrycon and H. boulengeri is sister to a clade of exclusively miniature species: Tucanoichthys tucano and species of Priocharax ( Fig. 6). There are no known morphological synapomorphies for the clade we delimit here as Tyttobryconinae .

Four of the seven valid species of Priocharax were included in the phylogenetic analysis of the UCE loci and resolved as a monophyletic group ( Fig. 6). This is the first attempt to include Priocharax in a broad molecular phylogeny, as examination of voucher specimens of the samples of Priocharax in previous studies revealed an instance of misidentification (see: Souza

et al. 2022). When Priocharax was described, it was hypothesized as closely related to lineages classified here as Characinae (Weitzman and Vari, 1987) . The morphological reductions in Priocharax , interpreted as developmental truncations, have made it difficult to use morphological characters to resolve the phylogenetic relationships of the lineage among Characiformes (Mattox and Toledo-Piza 2012, Mattox et al. 2016).

Priocharax and the enigmatic Tucanoichthys tucano resolve as sister-lineages in the UCE phylogeny ( Fig. 6). A detailed anatomical study revealed many similarities between the skeletons of T. tucano and Priocharax (Mattox and Conway 2021) . Many of the skeletal similarities are developmental truncations common to other miniature characid lineages, such as reduction in laterosensory system, reduced squamation, reduced number of fin rays, and specific bones that are absent or exhibit truncated development. Clearly any potential morphological synapomorphies among miniature characid lineages require a cautious interpretation due to the potential for convergent or parallel loss or reduction of traits (Weitzman and Fink 1983). There are two striking morphological characters that may represent reductive morphological synapomorphies for the clade containing Priocharax and Tucanoichthys : absence of the claustrum in the Weberian apparatus and the shape of the opercle that is developed ventrally but leaves a gap dorsally exposing part of the branchial chamber (Mattox et al. 2016, Mattox and Conway 2021). The claustrum is absent in all species of Priocharax with the exception of a rudimentary claustrum present in P. nanus Toledo-Piza et al., 2014 and P. toledopizae Mattox et al., 2023 ( Toledo-Piza et al. 2014, Mattox et al. 2023). Tucanoichthys and Priocharax also share a peculiar shape of the maxilla, with a long series of strictly conical teeth extending to the distal tip of the bone (Géry and Römer 1997, Mattox and Conway 2021), which is uncommon among small characids. It is interesting to note the relatively long branches of all miniature species throughout the phylogeny inferred from the UCE loci (Supporting Information, Figs S1–S 3), something noted above for other miniature taxa (e.g. Oxybrycon , Trochilocharax ). Species of Tyttobryconinae occur in Amazonia, with the exception of Hyphessobrycon boulengeri that is distributed in Atlantic coastal rivers ( Fig. 6).