Andersonia Boulenger 1900
Creators: name: Ferraris, Carl J.
name: Vari, Richard P.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Amphiliidae
Andersonia

description: Andersonia Boulenger, 1900
Andersonia Boulenger, 1900: 528 [Type species: Andersonia leptura Boulenger, 1900, by monotypy. Gender: Feminine]. Slatinia Werner, 1906a: 327 [Type species: Slatinia mongallensis Werner, 1906, by monotypy. Gender: Feminine].
Diagnosis. Andersonia is a member of the Doumeinae distinguished by the following combination of externally visible characters. The dorsal, pectoral and adipose fins each have a distinct spine anteriorly. A series of bony scutes cover the body posterior of the dorsal-fin origin. The lateral abdominal surface is not covered with superficial scutes. The scapulo-coracoid and clavicle lack superficial rugose plates.
Diogo (2003: 432) further diagnosed Andersonia by having a highly developed basioccipital that was larger than the prootic and a bony tube that extends transversely across the Weberian complex and attaches to the parapophyses.
Among the listed characters, the presence of spines on the dorsal and pectoral fins, and the absence of superficial scutes on lateral abdominal surface, scapulo-coracoid and clavicle are primitive states for the Doumeinae. Of the derived characters that have been proposed to diagnose Andersonia, only the large basioccipital appears to be unique to the genus within the Amphiliidae. Dorsolateral and ventrolateral extensions of the vertebrae that extend to the body surface and in many genera expand over the body surface as scutes that cover the posterior portion of the body are also found in Belonoglanis, Doumea, Phractura, Trachyglanis and appear to diagnose a clade within the Doumeinae consisting of all genera in the subfamily except Congoglanis (Ferraris et al., 2011). A spine at the origin of the adipose fin is also found in Trachyglanis (Harry, 1953), and a transverse tube across the Weberian complex occurs in the genera Leptoglanis and Zaireichthys (Diogo, 2003) of the subfamily Leptoglanidinae in the Amphiliidae.
Included species. Based on the evidence summarized below, we recognize only a single species in Andersonia, A. leptura.
Number of species in Andersonia. Boulenger (1918) distinguished Andersonia pellegrini from A. leptura by differences in the size of the eye and shape and length of the supraoccipital process. These purported differences were based on examination of a single specimen of each nominal species. In their analysis of a sample of the genus from the Chad system, Blache et al. (1964) found that the range in orbital sizes overlapped the difference in that feature originally cited by Boulenger to differentiate the species. Our broader geographic comparison confirms that the orbital size does not serve to delimit the nominal forms. Similarly the variation in the shape of the length of the supraoccipital process forms a continuum between populations in the Chad, Niger, Nile and Omo-Turkana basins. Direct comparisons of available samples of Andersonia from the four basins they inhabit revealed no differences in body shape or pigmentation pattern. A comparison of metric features readily amenable to examination similarly failed to reveal any between population differences (Table 1). As such, all populations are treated here as part of a single species. A. leptura that is widely distributed across the Nile, Omo-Turkana, Chad, and Niger basins.
Niger Nile Chad Anal-fin rays ii,6 1 1 ii,6, i 2 5 4 ii,7 1 4 [46] 6 ii,7, i 4
ii,8 4 [10] 1 ii,8, i 1 1
Caudal-fin rays i,5,5, i 2 [1]
i,5,6, i 3 3 [5]
i,6,5, i 1 2 7 i,6,6, i 1 10 [36] 6
Plates 23/ 22 1 2 1 (dorsolateral/ventrolateral) 23/23 1
24/ 23 1 8 7 24/ 24 5 1 25/ 24 3 1 3 26/ 25 1 1
Vertebrae 34 1 2 (including Weberian centra 35 5 13 15 and 1 ural centrum) 36 1
Ribs 4 5 12 18
5 2
Phylogenetic position. Although Boulenger (1900) initially considered Andersonia to be closely related to Phractura, He et al. (1999) recovered Andersonia as the sister group of a clade consisting of Belonoglanis, Doumea, Phractura and Trachyglanis [no species of what is now Congoglanis were included in the study] in a single most-parsimonious tree based on a suite of osteological characters. Conversely, neighbor-joining of the same matrix brought together Andersonia only with Belonoglanis and Trachyglanis. In a subsequent study that emphasized osteology and myology of the head region, Diogo (2003) concluded that Andersonia was sister to a clade composed of Belonoglanis and Trachyglanis. That hypothesis was based on the shared presence of a well-developed lateral lamina of the parieto-supraoccipital, a well-developed posteromedial process of the scapulo-coracoid, and a greatly reduced and modified posterior ceratohyal. Belonoglanis and Trachyglanis exhibit the derived superficial ossifications on the ribs, scapulo-coracoid and clavicle that are absent in Andersonia, which supported Diogo’s hypothesis that those genera were sister taxa. Diogo also proposed a more encompassing clade supported by numerous characters in which Phractura was the sister group to the clade formed by Andersonia, Belonoglanis and Trachyglanis. Problematically, the monophyly of Phractura in that phylogenetic scheme was supported solely on an unusual two-headed articulation between the hyomandibula and the opercle that was, however, observed in only one specimen of one species of Phractura (of the 13 species now recognized in the genus). That single observation, together with the lack of any additional reported derived characters in Phractura, leaves open a question of the monophyly of that genus.
One implication of the uncertainty as to whether Phractura represents a natural group is the possibility that Andersonia might be more closely related to a subset of the species of Phractura than to the remaining congeners. Such an eventuality might require a change in the definition and scope of Andersonia. A resolution of that issue requires a comprehensive phylogenetic analysis of the Doumeinae, which lies beyond the scope of this study and, more significantly, is being undertaken by another researcher. Based on published phylogenetic studies (He et al., 1999; Diogo, 2003), Andersonia leptura fits into a clade within the Doumeinae that includes Belonoglanis and Trachyglanis. Furthermore, under present concepts A. leptura cannot be assigned to either of those genera. Thus, the continued recognition of Andersonia is required because of current hypotheses of the monophyly of the two related genera and furthermore satisfies the interest of nomenclatural stability.
Remarks. Andersonia was initially reported to lack teeth in the jaws (Boulenger, 1900) and that characterization had been repeated by several authors (e.g., Harry, 1953; Poll and Gosse, 1995). Blache et al. (1964), however, reported teeth on the premaxilla of specimens from the Lake Chad basin and Golubtsov et al. (2004) determined that teeth were uniformly present in both jaws in large series of specimens from the White Nile system. Our observations confirm the broad occurrence of such dentition in samples from the Chad, Niger and Nile basins.
description: Published as part of Ferraris, Carl J. & Vari, Richard P., 2012, Review of the African catfish genus Andersonia (Teleostei: Siluriformes), pp. 39-49 in Zootaxa 3210 on pages 40-42, DOI: 10.5281/zenodo.280207