Reconsidering pectoral girdle and fin morphology in Anguillidae (Elopomorpha: Anguilliformes)

Abstract

The morphology of the pectoral girdle and fin of Anguillidae is reconsidered via the inclusion of skeletal components that have previously been unassessed. For example, the pectoral girdle and fin in Anguilla were erroneously reported to lack a scapular bone, a cartilaginous scapulocoracoid plate and a cartilaginous propterygium. The pectoral morphology of Anguilla is also compared with the closely related genus Nemichthys, including additional data on the anatomy of this eel family.

Morphological evolution and diversity of pectoral fin skeletons in teleosts

“…We showed that some species in teleosts have different numbers of proximal radials (Fig. 2), and we also found some examples in Anguilliformes (da Silva and Johnson, 2018; da Silva, Datovo and Johnson, 2019), Osteoglossiformes (Cavin and Forey, 2001), Alepocephaliformes (Johnson and Patterson, 1996), Siluriformes (Starks, 1930; Brousseau, 1976b), Stomiatiformes (Fink, 1985), Gadiformes and Lophiiformes (Starks, 1930). These species seem to have secondarily deviated from the four-basal rule (Fig 6, 7, black and white circles).…”

“…In previous studies (Starks, 1930; da Silva and Johnson, 2018; da Silva, Datovo and Johnson, 2019), pectoral fin skeletons in the other 11 species of Anguilliformes, 3 species of Elopiformes and 1 species of each Albuliformes and Notacanthiformes in Elopomorpha have been reported. Regarding Anguilliformes, while some species such as blackbelly spoonbill eel ( Nessorhamphus danae ) and narrownecked oceanic ell ( Derichthys serpentinus ) have retained four proximal radials, others show an increase or decrease in the number of proximal radials (da Silva and Johnson, 2018; da Silva, Datovo and Johnson, 2019). For example, in some species, such as common false moray ( Kaupichthys diodontus ) or margintail conger ( Paraconger caudilimbatus ) the number of proximal radials was reduced to three, while in some such as Klausewitz’s garden eel ( Gorgasia klausewitzi ) or American eel ( Anguilla rostrata ) the number of proximal radials was increased in the range of five to seven, and these proximal radials were basically rectangular.…”

“…In previous studies (Starks, 1930; da Silva and Johnson, 2018; da Silva, Datovo and Johnson, 2019), pectoral fin skeletons in the other 11 species of Anguilliformes, 3 species of Elopiformes and 1 species of each Albuliformes and Notacanthiformes in Elopomorpha have been reported. Regarding Anguilliformes, while some species such as blackbelly spoonbill eel ( Nessorhamphus danae ) and narrownecked oceanic ell ( Derichthys serpentinus ) have retained four proximal radials, others show an increase or decrease in the number of proximal radials (da Silva and Johnson, 2018; da Silva, Datovo and Johnson, 2019).…”

“…For example, in some species, such as common false moray ( Kaupichthys diodontus ) or margintail conger ( Paraconger caudilimbatus ) the number of proximal radials was reduced to three, while in some such as Klausewitz’s garden eel ( Gorgasia klausewitzi ) or American eel ( Anguilla rostrata ) the number of proximal radials was increased in the range of five to seven, and these proximal radials were basically rectangular. All of the eels in Anguilliformes lack the mesocoracoid (da Silva and Johnson, 2018; da Silva, Datovo and Johnson, 2019). However, in Elopiformes and Albuliformes, the number of proximal radials is not variable and the mesocoracoid is retained (Starks, 1930).…”

Phylogenetic interrelationships of the eel families Derichthyidae and Colocongridae (Elopomorpha: Anguilliformes) based on the pectoral skeleton

“…The analysis included all bony and cartilaginous elements of the pectoral girdle, radials and dermal rays (lepidotrichia). The anatomical terminology followed Starks (1930), Jessen (1972), Grande (2010), Hilton, Grande, and Bemis (2011), and Silva and Johnson (2018). The character matrix was assembled in Mesquite v. 3.51 (Maddison & Maddison, 2018).…”