User:TriNotch/Acanthobunocephalus scruggsi

Description
The dark-colored aspredinid,Acanthobunocephalus scruggsi, found in the Amazon Basin in the Purus river, can be identified by its decreased number of pectoral and dorsal fin rays compared to other members of its family, who typically average 5 or more pectoral fins and 3 or more dorsal fins relative to the Acanthobunocephalus scruggsi characterized by its 4 pectoral fins and 2 dorsal fins. Acanthobunocephalus scruggsi also presents with 5 pelvic fin rays, which is unique to this species of Asperinidae (Tiage, Reis 2020). Hailing from the Aspredinidae family commonly known as Banjo catfishes due to their morphological similarity to the shape of the North American instrument, the Banjo (Tiage, Reis 2020). The skin of A.scruggsi has been described as rough, with unculiferous tubercles, a feature shared among Banjo Catfish (Friel, 1995) throughout its body which is notably smaller in size on the head when compared to the rest of their body(Tiage,Reis 2020).Its eyes are known to proturde from their head and the overall size of A.scruggsi has been found to be 22.1mm, but the ranges of size for this species are not fully known due to limited specimen recovery, but is considered to be a miniature species amongst its genus (Tiage, Reis 2020). The mouth of Acanthobunocephalus scruggsi does present needle shaped teeth on its dentary bone in rows ranging from one to three, and also has a notably slender maxilla bone (Tiage, Reis 2020).

Taxonomy
Acanthobunocephalus scruggsi can be classified as a member of the apredinidae family, commonly known as Banjo Catfishes, which is comprised of 44 species(Carvalho,Sabaj 2018) The classification of the Apredinidae clade is well defined by several physical homologies, such as the feature of unculiferous tubercles in rows on the bodies of the cogeners (Carvalho,Sabaj 2018), and well as by their noted out skin shedding(Friel, 1995). The Acanthobunocephalus Genus which Acanthobunocephalus scruggsi belongs is found to be most similar to the Bunocephalus and Amaralia families, and is a genus comprised of currently one other species excluding A.scruggsi (Tiage,Reis 2020) The classification of Acanthobunocephalus scruggsi into this relatively small genus has been made apparent by its distinctive features shared with its cogener, A.nicoi, such as the lack of pro-current caudal fin-rays and the notable dorsal splintlet being associated with the rigid dorsal fin spine, which is unique to these two species, alongisde reduced ornamanetation seen in the skull roof.However, certain morphologies which differ between Acanthobunocephalus nicoi and Acanthobunocephalus scruggsi have been analyzed which allow for Acanthobunocephalus scruggsi to be classified as a different species,such as the relativly darker shade of pigmentation seen in Acanthobunocephalus scruggsi on the pectoral fin compared to the pectoral fin of Acanthobunocephalus nico.The use of osteological comparison of the two cogeners also allowed for further analysis to cement the claim of these two organisms as seperate species under the phylogenetic model (Tiage,Reis 2020).

Discovery and Naming
A.scruggsi falls under the category of catfishes commonly named Banjo Catfishes stemming from their unique shape resembling the North American Instrument. A.scruggsi lacks any common name, as the species is newly discovered. Its scientific name however follows the linnaean binomial nomenclature, which grants it the name Acanthobunocephalus scruggsi. The discovery of A. Scruggs in 2020 comes from phylogenetic analysis of its genus, Acanthobunocephalus, revealing distinctions in the recovered specimens to warrant a new species via the phylogenetic species concept (Tiage, Reis 2020), through both molecular and morphological lines of evidence. Its cogener, A.nicoi, has several morphological differences from A. scruggsi which warranted its position as a new species such as A.scruggsi's range of 4-5 anal fin rays, compared to A.nicoi and most other Bnajo catfishes presenting with 6 or more(Tiage,Reis 2020). The discovery of A. scrugssi also warrants new research on the autapomorphies of the genus due to the distinctions of A. scruggsi from A.nicoi., as it is the second member of its genus to be discovered.

Etymology
Acanthobunocephalus scruggsi derives part of its name from Earl Scruggs, a prominent banjo player who was known for popularizing a banjo picking style called the “Scruggs style” (Carvalho, Reis). As revealed by the word scruggsi, Acanthobunocephalus scruggsi resembles the shape of the musical instrument banjo. The first part of the species’ name, Acanthobunocephalus, refers to a genus of banjo catfishes found in South America. Acanthobunocephalus itself stems from the Greek word akanthos, which means spine, and bunocephalus, which refers to the rigid, locked spine of the genus (Friel 1995). Acanthobunocephalus is also gender masculine (Friel 1995). A. scruggsi is distinguished for its ray fins and unique spine shape.

Modern Classification (Phylogeny + Evolutionary Relationships)
Acanthobunocephalus scruggsi is evolutionarily distinct from the rest of the banjo catfish taxon. Although A. scruggsi morphologically resembles the aspredinid family, which consists of many species of South American banjo catfishes, it is unique for its reduced number of fin rays; it has four pectoral-fin rays, two dorsal-fin rays, five pelvic-fin rays, four to five anal-fin rays, and nine caudal-fin rays (Carvalho, Reis). In contrast, the members of the aspredinid family typically have five or more pectoral-fin rays, three or more dorsal-fin rays (except Amaralia hypsiura), six or more pelvic-fin rays (except Bunocephalus verrucosus), and 10 caudal-fin rays (except Hoplomyzontinae, Amaralia, Platystacus, Bunocephalus chamaizelus, and Bunocephalus minerim) (Carvalho, Sabaj 2020).

The genus Acanthobunocephalus itself is a sister group to the aspredinid and bunocephalus family, minus Psuedobunocephalus (Carvalho, Reis). This has been determined through morphological and molecular data, although phylogenetic evidence is relatively weak and more research is needed to expand on evolutionary relationships. The sister group relation is supported by the commonality of six morphological character-states: possession of a connection between the opercle and interopercle, possession of an anteriorly directed lamina in the anterior ceratohyal, absence of fifth epibranchial, broad contact between fourth and fifth parapophyses, possession of laterally directed bony lamina on posterior vertebral centra, and hemal spines bifid articulating with anal-fin pterygiophores (Carvalho, Sabaj 2020). Acanthobunocephalus is further distinguished from the other South American banjo catfishes by the presence of “a dorsal spinelet associated with a rigid dorsal spine, an anteriorly expanded parieto-supraoccipital, a reduced posterior portion of the cranial fontanel, a horizontal bony lamina developed only on the last three centra and the compound ural centrum, and the absence of procurrent caudal-fin rays” (Carvalho, Sabaj 2020). The following phylogenetic tree proposed by ichthyologist Tiago P. Carvalho et. al is drawn and shown to the side:

Subdivision
Among the Acanthobunocephalus are A. scruggsi and A. nicoi. Acanthobunocephalus was originally considered to be monotypic (consisting of only a single species, A. nicoi); however, size differences and differing locations of A. scruggsi and A. nicoi suggest that the two are separate species rather than a single population subdivision (Carvalho, Manuela 2019). Both are miniature species of the banjo catfishes, but A. nicoi are found in the upper Orinoco River basin, including the Sipapo, Ramoni and Casiquiare rivers in and near Venezuela, whereas A. scruggsi have been documented in Lower Purus River Basin in the Amazon Basin in Brazil (ITIS). Furthermore, in contrast to A. nicoi, A. scruggsi possesses lateral wings on urohyal, has an extension of the contact between parapophysis of complex vertebrae and fifth vertebra reduced (vs. contact large, same extension of lateral blade of parapophysis of complex vertebrae), has hemal spines contacting anal-fin pterygiophores simple (vs. bifid), has modally two ribs (vs. modally five), has ossified infraorbital canal tubules present (vs. absent), among other structural differences (Carvalho, Manuela 2019). A current phylogenetic tree might show A. scruggsi and A. nicoi as sister species branching from the same node, although to establish this claim, further molecular and morphological evidence would be needed. Not much data is available about subdivision within the A. scruggsi species itself, as the population is small. It is considered a vulnerable species, but since the lakes and rivers in the region are conserved, the population is considered to be stable (Rodriquez-Olarte 2021). A. scruggsi has not been documented outside of the Lower Purus River Basin in the Amazon Basin in Brazil, which suggests that population subdivision has not yet occurred. The conditions of the river and lakes also suggest no evolutionary pressure for subdivision. Further research is needed to gather more details in this area.

Diet
Most members of the Aspredinidae family are generalized omnivores that feed on aquatic and terrestrial invertebrates and organic debris (Friel 1995). It is assumed that the Acanthobunocephalus scruggsi follow similar feeding patterns. For example, the A. nicoi is homologous to the A. scruggsi, so information has been provided from their similarities. Due to their slow-moving nature, they tend to stick with earthworms, bloodworms, and tubifex. More data and research is needed on A. scruggsi to reach a definitive answer of its diet in relation to other members of its family.

Distribution and Habitat
This species lives in inland wetlands and freshwater areas. Acanthobunocephalus scruggsi, like most species of the Aspredinidae family, is a benthic (demersal) species which inhabits forested lentic habitats (lagoons) or slow currents (igarapés, creeks) with black and acid waters, very low concentration of dissolved solids and usually associated with plant debris (Carvalho, Reis). This species has been found to be distributed within the Purus River of the Brazilian Amazon centered on the middle Solimões region.

Conservation
There are no explicit laws, regulations, or educational programs in place to safeguard the Acanthobunocephalus scruggsi. This species is thought to live in several protected areas in the Purus river valley, including Resex Canutama, Parna Nascentes do Lago Jari, Rebio do Abufari, and RDS Piagacu-Purus (IUCN and UNEP-WCMC 2020). Species must always be aware of their surroundings and communicate with one another. However, according to the International Union for Conservation of Nature Red List, this genus is of Least Concern, albeit some conservation measures are recommended (Carvalho, Reis). Although it has a limited population, this species faces no serious threats.