Euryochus Pereira and Reis

Pereira, Edson H. L. & Reis, Roberto E., 2017, Morphology-based phylogeny of the suckermouth armored catfishes, with emphasis on the Neoplecostominae (Teleostei: Siluriformes: Loricariidae), Zootaxa 4264 (1), pp. 1-104 : 76-77

publication ID 10.5281/zenodo.574211

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Euryochus Pereira and Reis

gen. nov.

Genus Euryochus Pereira and Reis , New Genus

Included species. Euryochus thysanos , new species

Diagnosis. Euryochus is diagnosed by one exclusive autapomorphy: Dorsal concavity at anterior portion of mesethmoid (Char. 1.1). Non-exclusive autapomorphies include: ventral process of sphenotic absent or inconspicuous (Char. 12.0), anterior and posterior margins of each branchial filament fringed and ornamented with small epithelium expansions (Char. 27.1), cartilaginous mesial tip of first ceratobranchial narrow (Char. 34.0), third ceratobranchial rod-shaped, without any ventral process (Char. 36.0), anteroventral process of fifth ceratobranchial short and inconspicuous (Char. 38.0), anterodorsal margin of hyomandibula slightly expanded, projecting above posterior margin of metapterygoid (Char. 66.1), crest for insertion of levator arcus palatini oriented horizontally (Char. 77.2), crest for insertion of levator arcus palatini long, extending to margin of hyomandibula (Char. 78.1), lateral wall of metapterygoid incomplete, not extending along entire dorsal margin of metapterygoid canal (Char.

88.0), interoperculo-mandibular ligament present between anguloarticular and opercle (Char. 91.0), exit of preopercular canal lying anterior to posterior margin of quadrate (Char. 98.1), preopercle with small ventrolateral expansion forming concave area laterally (Char. 100.1), ventral laminar extension of quadrate short, distinctly shorter than depth of anterior condyle (Char. 103.1), supra-preopercle present as small plate with bony wings surrounding ossified sensory canal tube (Char. 111.2), seven precaudal vertebral centra (Char. 120.6), distal tip of sixth centrum rib slightly expanded (Char. 130.1), narrow bony lamina ventral to arrector bridge projecting anteriorly from the coracoid towards cleithrum (Char. 154.1), dorsal margin of pectoral-fin radial 3 with short dorsal expansion (Char. 177.1), ventrolateral margin of basipterygium lacking small bony process directed mesially (Char. 187.0), posterior process of basipterygium equally broad and short, with distal margin pointed (Char. 193.3), mesial end of lateral plates distinctly superposed to first anal-fin pterygiophore (Char. 211.2), lateral process of third anal-fin pterygiophore simple and without any expansion (Char. 214.0), dorsal and ventral lobes of hypural plate asymmetrical, with hypurals 1+2 extending slightly beyond posterior margin of hypurals 3+4+5 (Char. 216.1), ventral surface of caudal peduncle distinctly flat (Char. 228.1), and tooth cusps asymmetric and minor lateral cusp long reaching to or beyond half length of main mesial cusp (Char. 260.2).

Comparisons. In addition to the synapomorphies above, Euryochus can be readily distinguished from all other neoplecostomines by the shape of the caudal peduncle, which is somewhat flat dorsally and very flat ventrally (though Pareiorhina rudolphi and Pareiorhaphis bahianus also with a flat caudal peduncle ventrally), larger eye (16.1–19.7 % in HL versus 13.1–16.5 in Hirtella , 10.6–14.5 in Isbrueckerichthys , 12.0– 17.9 in Kronichthys , 5.0– 12.9 in Neoplecostomus , 8.6–18.8 in Pareiorhaphis , and 8.7–13.0 in Pareiorhina ), and by the general color pattern of the lateral portion of the caudal peduncle, which is usually brown dorsally and light cream ventrally, with a darker midline stripe. Euryochus is further distinguished from Neoplecostomus and Isbrueckerichthys by lacking plates in the abdomen, and from Pareiorhaphis and Hirtella by lacking large hypertrophied odontodes as a secondary sexual dimorphism of mature males. Finally, it is further distinguished from Pareiorhina by having a well-developed adipose fin (absent in Pareiorhina ) and from Kronichthys by its wide, rounded head shape in dorsal view (narrow and nearly rectangular in adult Kronichthys ).

Etymology. Euryochus , from the Greek Eurys , broad or large, and okkos, eye, in allusion to the noticeable larger eye of this genus compared to other neoplecostomines. Gender masculine.

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