Ernstichthys taquari, Dagosta & Pinna, 2021

Dagosta, Fernando Cesar Paiva & Pinna, Mário de, 2021, Two new catfish species of typically Amazonian lineages in the Upper Rio Paraguay (Aspredinidae: Hoplomyzontinae and Trichomycteridae: Vandelliinae), with a biogeographic discussion, Papéis Avulsos de Zoologia (Pap. Avulsos Zool., S. Paulo) 61, pp. 1-23 : 9-12

publication ID	https://doi.org/ 10.11606/1807-0205/2021.61.47
publication LSID	lsid:zoobank.org:pub:31481179-ADAD-48BF-BD7E-F326BEE7999A
persistent identifier	https://treatment.plazi.org/id/03A087F5-FF8F-356A-FEBF-FC2A4616475F
treatment provided by	Carolina
scientific name	Ernstichthys taquari
status	sp. nov.

Treatment

Ernstichthys taquari sp. nov.

http://zoobank.org/ 17ADE44D-AB3D-407A-AA08-9011EFE0F470 ( Figs. 4-6 View Figure 4 View Figure 5 View Figure 6 )

Holotype: MZUSP 125825 View Materials , 22.8 View Materials mm SL, Brazil, Mato Grosso do Sul, Alcinópolis, Rio Taquarizinho (tributary to rio Taquari , rio Paraguay drainage) (18°12′14.8″S, 53°34′11.3″W), elev. 363 m, col. F. Dagosta, A. Ferreira, R. Zanon, 18 Sep 2019. GoogleMaps

Paratypes: MZUSP 125826, 2 ex, 20.2-22.7 mm SL, collected with holotype.

Diagnosis

Ernstichthys taquari differs from all congeners by: 1) the relatively narrow bilateral bony shields on dorsal and ventral series, which do not overlap or contact each other anywhere in both series (vs. adjacent shields contacting or overlapping along most or entire series; this trait also distinguishes the species from most hoplomyzontine species except those of Hoplomyzon ); 2) the presence of seven or eight serrations on the posterior margin of the pectoral spine (vs. 10-18); 3) the pectoral-fin spine only slightly larger than subsequent soft rays, so that there is a gradual transition between the spine and the rest of fin (vs. spine 25% longer or more than soft rays, leaving large portion of protruding spine without corresponding fin web distally). Further distinguished from E. megistus by the presence of a well-developed rictal barbel (vs. barbel absent or reduced to bump). Further distinguished from E. intosus by the unbranched maxillary barbel (vs. with thread-like secondary barbels); by the lack of dentations along the anterior margin of the pectoral fin (vs. dentations present); by the presence of two pairs of stout and regularly-positioned mental barbels ( Figs. 4-5 View Figure 4 View Figure 5 ; vs. over 100 thread-like and uniformly distributed barbels); by the presence of i+4 dorsal-fin rays (vs. i+7); by the presence of i+6 anal-fin rays (vs. viii+4); by the basipterygium entirely hidden in integument (vs. anterolateral arm of basipterygium exposed on the skin, forming rugose shield).

Description

General body aspect, shape and pigmentation in Figs. 4-5 View Figure 4 View Figure 5 . Morphometric data in Table 3. Dorsal and ventral profiles of body and head in nearly mirror images of each other, gently convex to origins of dorsal and anal fins, respectively, then straight along to nearly end of caudal peduncle. Greatest depth of body at posterior part of head and greatest width between bases of pectoral-fin spines. Caudal peduncle depressed for most of its length, except for compressed terminus near base of caudal fin. Caudal peduncle least deep at ca. threefourths of its length. Head depressed, gently convex in dorsal and ventral profiles. Mid-dorsal cephalic region with three bony prominences disposed in line, anterior one occipital, at limit between supraoccipital and neural complex of Weberian apparatus, second one formed by posterior part of neural complex of Weberian apparatus and third one immediately anterior to dorsal fin, formed by central portion of middle nuchal plate ( Fig. 6 View Figure 6 ). Anterior cranial fontanel large, elongate-ovoid, with anterior portion narrower than posterior one, occupying most of body of mesethmoid and anterior half of length of frontals.Posterior fontanel about 30% shorter and 10% narrower (at widest portion) than anterior one ( Fig. 6A View Figure 6 ), delimited mostly by frontals and only posterior end by supraoccipital. Frontals mostly separated from each oth- er at midline by fontanels, contacting at a small portion at their midlength, corresponding to the epiphyseal bar, with two frontals forming H-shaped configuration in dorsal view. Supratemporal fossa (not visible externally) roughly oval, positioned between posterior portion of mesial margin of pterotic and posterior portion of lateral margin of supraoccipital ( Fig. 6 View Figure 6 ). Transverse process of vertebra 5 slender, expanded distally and curved slightly posteriorly ( Fig. 6A View Figure 6 ), its distal edge exposed at surface of integument. Eye small, located dorsally on head slightly anteriorly to middle of HL, twice as close to midline as to lateral margin of head in dorsal view ( Figs. 4-5 View Figure 4 View Figure 5 ). Eye visible only partially in lateral view ( Figs. 4-5 View Figure 4 View Figure 5 ). Axillary gland pore small, slit-like when collapsed, located immediately posterodorsally to base of pectoral fin. Vent located slightly anterior to transversal through midlength of last pelvic-fin ray. Integument heavily covered with unculliferous papillae on dorsal part of head and dorsal and lateral sides of body, most prominently over area around margins of neurocranium, snout, basal half of dorsal surface of maxillary barbels and cheeks. Unculiferous tubercles homogeneously scattered on body, not arranged in rows or any other regular pattern. Ventral side of head with papillae softer and larger than those on dorsal side of head and rest of body.

Anterior nares encircled by short tubule, longer posteriorly,and separated from each other by distance short- er than interorbital. Posterior nostrils larger than anterior ones, separated from eye by one orbital diameter and partly covered by anteromesial flap of skin. Posterior nares more widely separated from each other than anteri- or ones, by distance approximately equal to interorbital. Mouth subterminal, slightly wider than interorbital, with both jaws in gentle continuous arcs, and lower jaw short- er than upper jaw. Teeth entirely absent on both jaws. Upper lip well delimited laterally by tumescent maxillary barbel bases, with large irregular-shaped and positioned papillae immediately at mouth opening. Lower lip smooth at edge of mouth but densely large-papillate further posteriorly, with papillate covering extending onto mental region. Mandibles thin and delicate, lacking bony contact at symphysis. Premaxillae shaped as large elongate plates jointly forming nearly continuous concave bony shield internally on upper jaw. Each premaxilla with large stout ascending process near midline, dorsoposteriorly accomodating mesethmoid cornua. Barbels eight: one pair maxillary, one pair rictal and two pairs mental. Maxillary barbel large, flat and expand- ed basally, forming most prominent feature on head. Maxillary barbel doubly adnate, dorsally from proximal two-thirds of its posterior margin to cheek and ventrally from base of rictal barbel to mental region immediately anterior to anterior mental barbel. Skin folds of adnation forming deep pocket lateral to rictus and anterior to coronoid process of mandible. Rictal barbel short, directed ventrally or ventrolaterally, inserted ventrally at anterior attachment of ventral adnation of maxillary barbel, Two pairs of mental barbels inserted close to lateral margin of ventral side of head; posterior one twice as long and thick as anterior one. Branchiostegal membranes broadly united to isthmus, without free fold. Gill openings ventral, reduced to small oblique slits anteromedial to insertions of pectoral spines, approximately twice as wide as width of pectoral-fin spine base. Branchiostegal rays four, first one short and thin, attached to middle of anterior ceratohyal. Remaining three branchiostegal rays longer and stouter than first one, attached to posterior end of anterior ceratohyal.

Pectoral fin large, I+6+i *(3), with soft branched rays thin and delicate, shorter than spinous ray but not to same degree as in other species of Ernstichthys . Pectoralfin spine long, 35-36% of SL, with triangular soft tissue cap distally. Anterior margin of spine smooth, without serrations. Posterior margin with seven large pungent antrorse serrations, progressively larger distally, plus one or two proto-spinous bony bumps basally. Cleithral bullae large and conspicuous, forming widest part of body and head in dorsal view. Postcleithral process large, broad and abruptly narrow and pointed distally, reaching to middle of Weberian centrum in lateral view,and almost to vertical through tip of coracoid process.Posterior coracoid process long, slightly curved mesially distally, its tip reaching half-length of basipterygium and almost to base of pelvic fin. Pelvic fin long and pointed, insert- ed well anteriorly to vertical through origin of dorsal fin, i+5*(3), with first ray thickest of series and 30% shorter than second. Second pelvic-fin ray longest of series and thicker than all other rays except first. Basipterygium with long pointed posterior process reaching almost to transversal through anterior tips of first ventral shield. Dorsal-fin origin well anterior to half of SL, entirely adnate posteriorly, to end of last fin ray. Dorsal spinelet (or first spine, or spine lock) absent, first ray (homologous to main dorsal-fin spine) not spinous, flexible, segment- ed and without serrations. Dorsal-fin rays I+4*(3). Four dorsal-fin pterygiophores broad and angulate in shape, pierced by large irregular fenestrae.Anterior nuchal plate absent. Remaining nuchal plates described above under dorsal shield series ( Fig. 6 View Figure 6 ). Adipose fin absent. Anal fin insertion at vertical through end of dorsal-fin base,partly adnate, to ca. two-thirds of last ray, with small free edge at end. Anal-fin rays i+6*(3), third and fourth rays longest. Seven anal-fin pterygiophores progressively smaller posteriorly, four anterior ones squarish and irregularly fenestrated, posterior three rectangular and lacking fenestrae. Caudal fin 5+4*(3), with lower lobe longer than upper one as consequence of elongate lower principal fin-rays. Profile of upper lobe straight or gently sinusoidal, that of lower lobe convex and round. All principal rays closely set, nearly adpressed at base. Outer rays thicker and with bases much stouter than that of remaining rays. Procurrent caudal-fin rays represented by single ventral element, spine-like and bent near base. Dorsal procurrent caudal-fin rays absent.

Body armored with three series of bony elements: dorsal, ventral and lateral, all of which heavily cov- ered with integument and not conspicuous on surface of body. Dorsal and ventral series running alongside mid-dorsal and mid-ventral lines, respectively. Lateral series extending along midlateral line of each side of body. Dorsal series formed by 21 heavily ornamented shields extending from immediately anterior to dorsal fin to end of body. Four of those shields disposed alongside base of dorsal fin. First shield of dorsal series formed by greatly expanded posterior nuchal plate, supported by bilateral dorsal processes of vertebra 8. Remaining 20 dorsal shields formed by expanded tips of bilateral dorsal processes ( Fig. 6 View Figure 6 ) on vertebrae 9 to compound ural centrum. Anterior fourteen vertebrae-derived shields bilateral, gradually closer together at the midline posteriorly. Posterior six shields median, progressively narrower posteriorly. Elements of dorsal shield series not overlapping each other and not contacting those of lateral series, except for last one which barely touches dorsal margins of penultimate and antepenultimate lateral plates. Ventral shield series with 16 heavily ornamented bony shields, with two anterior ones anterior to anal fin. First shield largest, formed by distal expansions of hemal arch of vertebra 9, broader anteriorly than posteriorly and with concave anterior and posterior margins, its anterior margins produced into anterolateral processes distally approaching posterior processes of basipterygia. Second ventral bony shield immediately anterior to anal fin, lozenge-shaped and formed by distally-expanded first anal-fin pterygiophore. Remaining 14 shields formed by distal expansions of bilateral ventrolateral vertebral processes, extending to posterior-most vertebra anterior to caudal centrum. Of those, nine anterior ones bilateral (six of which disposed alongside anal-fin base) and remaining five ones median, latter clearly formed by confluence of bilateral portions. Posterior five ventral shields broader than long, except for long isosceles-triangular last element. Ventral shields not overlapping each other and not contacting any element of lateral series. Lateral series composed of actual plates or scutes, contrary to dorsal and ventral series, and formed by modified and hypertrophied lateral-line ossicles lacking direct contact with vertebral column. Lateral shields not ornamented and covered with thick integument, not readily visible on external aspect of body. Transition of lateral line tubules into plates gradual, starting at ninth ossicle, approximately at vertical though end of dorsal-fin base, and progressively more expanded towards caudal fin. Overlap among plates starting at ossicle 15, forming complete shield on sides of body from that point on. Total of 34 plates, each with central blunt knob of thickened bone except for last one ( Fig. 6 View Figure 6 ), collectively forming lateral serration. Knobs gradually less prominent posteriorly, covered with thick soft skin and concentration of papillae. Knobs centrally located on anterior plates but gradually displaced dorsally starting on 24 th plate. Spacing between knobs slightly decreasing towards caudal fin.

Total vertebral count 29 (including those in Weberian complex). Ribs absent.