HYPOSTOMINI, Kner, 1853

Armbruster, Jonathan W., 2004, Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae, Zoological Journal of the Linnean Society 141 (1), pp. 1-80 : 51-53

publication ID	https://doi.org/ 10.1111/j.1096-3642.2004.00109.x
publication LSID	lsid:zoobank.org:pub:E3B62DC6-FA3F-42C7-A2A9-D6DA00C7021D
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scientific name	HYPOSTOMINI
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HYPOSTOMINI

Within the Hypostomini , Hypostomus is a paraphyletic assemblage whose members are sisters to Aphanotorulus , Isorineloricaria , and Cochliodon ( Fig. 37 View Figure 37 ). Armbruster & Page (1996) and Armbruster (1998a) provide evidence that suggests that Aphanotorulus , Isorineloricaria , H. emarginatus , and H. squalinus form a monophyletic group (the H. emarginatus group).

Analysis including the characteristics suggested in the previous studies provides several potential synapomorphies for the H. emarginatus group: elongated first hypobranchial (23: 1), seven or more infraorbital plates (91: 2), contact between metapterygoid and lateral ethmoid shifted anteriorly (99: 1; Fig. 20D View Figure 20 ), an enlarged central papilla in the buccal cavity (178: 1), and hypertrophied odontodes on the bodies of breeding males (199: 1; Fig. 39A View Figure 39 ). The unique coloration of these species (white to tan ground colour with black spots; Figs 39A View Figure 39 , 40A View Figure 40 ) makes them readily identifiable from most other Hypostomus . In this analysis, a monophyletic H. emarginatus group was found in most of the most parsimonious trees; however, Isorineloricaria was restricted from the group in the strict consensus tree ( Fig. 37 View Figure 37 ). Montoya-Burgos et al. (1998) also suggest that Aphanotorulus and H. emarginatus are sisters; however, Isorineloricaria is the sister to Parancistrus (Ancistrini) in their analysis. A monophyletic group of Isorineloricaria and Parancistrus is not supported by any morphological evidence. Squaliforma was described in Isbrücker et al. (2001); however, no evidence was found to support Squaliforma Isbrücker , which consists of species of the H. emarginatus group minus Aphanotorulus and Isorineloricaria .

Cochliodon also appears to be a well-diagnosed group supported by the following synapomorphies: loss of the notch between the metapterygoid and hyomandibula (36: 0; Fig. 15A, H, I View Figure 15 ), a strongly curved maxilla (70: 1; Fig. 17C View Figure 17 ), and spoon-shaped teeth (205: 1; Fig. 35C View Figure 35 ). Evidence that Cochliodon is not as unique as taxonomy suggests is provided by Hypostomus hemicochliodon ( Fig. 37 View Figure 37 ). This species shares several synapomorphies with Cochliodon : preoperculohyomandibular ridge deflected posteriorly such that it is visible mesially (46: 1; Fig. 15D, I View Figure 15 ), a longitudinal ridge on the quadrate (68: 1; Fig. 15H, I View Figure 15 ; reversed in C. cochliodon ), dentaries forming an angle averaging less than or equal to 80∞ (69: 1), and two plates between the suprapreopercle and exposed opercle (81: 2; reversed in C. cochliodon ). However, H. hemicochliodon has teeth that, though tending towards the spoon-shaped teeth characteristic of Cochliodon , are not spoon-shaped ( Fig. 35B View Figure 35 ). Cochliodon uses its spoon-shaped teeth as chisels to remove small chips of wood from submerged logs ( Schaefer & Stewart, 1993; pers. observ.), and the vast majority of material in the intestine consists of small flakes of wood (pers. observ.). H. hemicochliodon predominantly has wood in the digestive tract, but has much more algae and detritus than typical Cochliodon . The placement of H. hemicochliodon in the phylogeny suggests that Cochliodon has evolved from algivorous Hypostomus .

Although the H. emarginatus group and Cochliodon (with the addition of H. hemicochliodon ) are probably monophyletic entities within the Hypostomini , there are no general trends in the relationships of the remainder of the species. There is very limited osteological differentiation among the various species of Hypostomus , and there are currently no characters that would allow one to break the Hypostomini into meaningful monophyletic groups. The Hypostomini is supported by the following synapomorphies: a hatchet-shaped opercle (78: 1; Fig. 19B View Figure 19 ), the anterior process of the pterotic-supracleithrum passing halfway through the orbit (112: 1), and a pointed cleithral process (156: 1). The decay index for the Hypostomini is fair (DI = 3) and equal to the decay index of many other similar groups). Because there is support for the Hypostomini as monophyletic, and because there is no information to suggest how to break the Hypostomini into smaller monophyletic entities, only Hypostomus is recognized, with Aphanotorulus, Cochliodon , Isorineloricaria , Squaliforma , and Watawata as synonyms. In the future, it would probably be useful to Tribe Genus