Lithoxini Isbrücker, 1980

Armbruster, Jonathan W. & Lujan, Nathan K., 2024, New tribe-level classification of Hypostominae (Loricariidae) based on optimization of morphological states on DNA-based relationships, with descriptions of three new tribes and two new genera, Neotropical Ichthyology (e 240108) 22 (4) : -

Tribe Lithoxini Isbrücker, 1980

Included genera.

Avalithoxus Lujan et al., 2018:10 . Type-species: Lithoxus jantjae Lujan, 2008

Lithoxus Eigenmann, 1910:405 . Type-species: Lithoxus lithoides Eigenmann, 1912 .

Exastilithoxus Isbrücker, Nijssen in Isbrücker, 1979:88. Type-species: Pseudacanthicus (Lithoxus) fimbriatus Steindachner, 1915 .

Paralithoxus Boeseman, 1982:46 . Type-species: Ancistrus bovallii Regan, 1906 .

Phylogenetic diagnosis. Reversal to a short, narrow accessory process of the first ceratobranchial (7:1, 8:1), reversal to a narrow fifth ceratobranchial (10:0), loss of the accessory process on the first epibranchial (14:0), loss of the posterior shelf on the fourth epibranchial (17:0), reversal to a narrow hypohyal (20:0), an elongate first hypobranchial (23:1), reversal to the anterohyal being located on or behind the hyomandibula (26:0), reversal to a round upper pharyngeal jaw with evenly distributed teeth (30:0), lateral wall of posterohyal absent so that posterohyal forms a half cylinder (32:1), reversal to no mesial contact of hyomandibula and quadrate (33:0), posterior portion of hyomandibula forming a shelf dorsally such that suture to pterotic-supracleithrum is nearly perpendicular to preoperculo-hyomandibular ridge (40:1), posterior process of hyomandibula incorporated into main body of hyomandibula (41:1, unique), branched preoperculo-hyomandibular ridge (48:1), reversal to loss of metapterygoid channel and dorsal surface of the metapterygoid being only slightly split, forming a narrow channel (52:1, 53:0), dentary tooth rows forming acute angle (69:0), maxilla expanded ventrally (71:1), bar-shaped opercle (75:2), two to four plates between canal plate and opercle (88:2), reversal to small mesethmoid disk (100:1), wide ventral process of sphenotic (116:1), bifid hemal spines (122:1), first neural spine anterior to first dorsal-fin pterygiophore (125:1), tip of transverse process of Weberian complex centrum not contacting compound pterotic (135:1), reduction of exposed portion of cleithral process (157:1), reversal to large space between posterior process of coracoid strut and posterior process of cleithrum (164:0), curved anterolateral processes of basipterygium meeting or nearly meeting at midline (167:0), loss of posteroventral ridge of basipterygium (173:0), enlarged teeth (205:2).

Comparative diagnosis. The Lithoxini can be separated from all except Leporacanthicus by having a nearly round, flat oral disk with mandibular barbels located and directed anterolaterally (vs. lips oval and mandibular barbels located and directed posterolaterally) and from Leporacanthicus by having more than two premaxillary teeth and all teeth of similar length (vs. two teeth per premaxilla and premaxillary teeth much longer than dentary teeth; see Lujan et al., 2018, for more detail).

Geographical distribution. Lithoxini is distributed exclusively within the Guiana Shield, from right bank tributaries of the Orinoco River , to the upper Negro and Branco rivers, to north-flowing basins from the Essequibo eastward to the Oyapock, and drainages flowing south from the Guianas into the lower Amazon.