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Bujurquina omagua sp. nov. urn:lsid:zoobank.org:act: 8E478708-58F1-4E97-960C-9FCD93107C9A Figs 6–10; Table 1 Bujurquina sp. Oran Říčan et al. 2022. Bujurquina sp. Peru 1 Říčan et al. 2022. Diagnosis Bujurquina omagua sp. nov. is highly apomorphic compared to other described species in the genus because it is unique in several character states. These include: 1) shape and pattern of the suborbital stripe in adults, which is bend and with a blotch at the postero-ventral end (vs straight or absent, with or without a blotch), with an ontogenetic change with juveniles and subadults having a straight stripe running diagonally postero-ventrally and starting from below the eye in juveniles (i.e., not bend as in adults) and without a blotch, 2) orange cheek and lower head coloration with alternating opalescent lines and series of spots on snout and spotted on cheek and lower head, 3) spinous portion of dorsal fin with a single thin diagonal black line per membrane, or two lines per membrane in holotype and largest adults (vs unpatterned in all Southern group species, or with circular blotches, with several thick diagonal black lines per membrane, or two thick horizontal bands across the dorsal fin in all other Northern group species), 4) longest snout of all species without overlap (mean 15.5%, 14.4–16.4% of SL; followed by B. oenolaemus with a mean of 11.4%, 10.3–13.1 of SL), and 5) most delicate LPJ, expressed by being shortest of all species with widest horns (length/width ratio 0.42–0.45 vs 0.50–0.64 in all other species), one of the smallest dentigerous areas (length of dentigerous area/width of LPJ ratio 0.33–0.34 vs 0.34–0.44 except B. tambopatae, B. moriorum and B. huallagae where also 0.33–0.34), and the least robust dorso-ventrally (bone at posterior end of dentigerous area less thick or equal to length of largest posterior teeth vs much thicker than teeth in other species). Bujurquina omagua sp. nov. is additionally diagnosed by the following unique combination of morphometric characters, the most pronounced of which characterize the robust head of the species: 1) second to third longest head (after B. oenolaemus and together with B. labiosa; both with a mean 37.0%, 36.3–38.0% of SL in B. omagua vs mean 39.1%, 38.6–40.4% of SL), 2) third longest preorbital distance (after B. robusta and B. oenolaemus; mean 9.3%, 8.5–10.0% of SL), 3) large interocular distance (largest mean value of all species, 12.5% of SL vs 9.7–12.4% however with large overlap of ranges with the other species), 4) rather wide head (mean 19.9%, range 19.1–20.7% of SL), 5) rather long preorbital distance (mean 9.3%, range 8.5–10.0% of SL, third longest based on mean value), 6) robust head which has rather small eyes (mean 11.3%, range 10.3–12.0% of SL), 7) very deep body (mean 45.1%, range 43.2–46.8% of SL, based on mean the second after B. vitatta), but 8) with rather long and shallow caudal peduncle (CPL mean 13.8%, range 12.6–15.6% of SL; CPD mean 16.6%, range 15.5–17.1% of SL), and 9) rather short last spine in the dorsal fin (mean 15.6%, range 12.3–17.1% of SL). Etymology The specific epithet ‘ omagua ’ is a noun in apposition given after the Omagua people, which were at the time of first contact with Europeans in the 16 th century the dominant people along the banks of the Amazon River upstream from the mouth of the Negro River well into Peru. Type material Holotype PERU • adult ♂, 97.4 mm; Amazonas river basin, Department Loreto, Maynas Province, District Las Amazonas, close to Oran village, Quebrada Sabalillo, cabeceras upper locality P18-17; 3° 27´08.4˝ S, 72° 29´11.8˝ W; 97 m a.s.l. based on GPS, 115 m a.s.l. based on Google Earth; 28 Jun. 2018; Říčan leg.; clear-water stream with blackish tinge; ID tag 1189; MUSM 70225 (Figs 6, 8–9). Paratypes All from Peru, Amazonas river basin, Department Loreto, Maynas Province, District Las Amazonas, close to Oran village, 9 ex. PERU • 1 adult, 78.6 mm; same collection data as for holotype; ID tag 1188; GenBank: OP436199; MUSM 70224 • 1 adult, 98.9 mm; same collection data as for holotype; ID tag 1190; GenBank: OP436200; MUSM 70226 (Figs 7–9) • 1 adult, 69.7 mm; same collection data as for holotype; ID tag 1191; GenBank: OP436201; MUSM 70227 (Fig. 7) • 1 adult, 77.1 mm; same collection data as for holotype; ID tag 1192; GenBank: OP436202; MUSM 70228 (Fig. 7) • 1 adult, 78.7 mm; Amazonas river basin, Department Loreto, Maynas Province, District Las Amazonas, close to Oran village, Qebrada Sabalillo on trail from mouth, P18-15; 3° 27´45.6˝ S, 72° 29´22.5˝ W; 90 m a.s.l. based on GPS, 110 m a.s.l. based on Google Earth; 27 Jun. 2018; Říčan leg.; clear-water stream with blackish tinge; ID tag 1182; GenBank: OP436196; MUSM 70221 (Figs 7, 9) • 1 adult, 79.9 mm; Amazonas river basin, Department Loreto, Maynas Province, District Las Amazonas, close to Oran village, cabeceras of Quebrada Sabalillo, lower loc., P18-16; 3° 27´17.5˝ S, 72° 29´22.8˝ W; 75 m a.s.l. based on GPS, 117 m a.s.l. based on Google Earth; 28 Jun. 2018; Říčan leg.; clear-water stream with blackish tinge; ID tag 1185; GenBank: OP436197; MUSM 70222 (Figs 7, 10) • 1 adult, 92.6 mm; same collection data as for preceding; ID tag 1186; GenBank: OP436198; MUSM 70223 (Fig. 7) • 1 adult; Amazonas river basin, Department Loreto, Maynas Province, District Las Amazonas, close to Oran village, small unnamed quebrada just before entering Oran creek, P18-21; 3° 27´21.2˝ S, 72° 30´43.2˝ W; 82 m a.s.l. based on GPS, 104 m a.s.l. based on Google Earth; 3 Jul. 2018; Říčan leg.; clear-water stream with blackish tinge; ID tag 1200; GenBank: OP436204; MUSM 70229 (Fig. 7) • 1 juvenile; same collection data as for preceding; GenBank: OP436205; MUSM 70230. Description Compound, based on eight specimens from Sabalillo creek, 69.7–98.9 mm. Refer to Figs 6–10. Measurements summarized in Table 1. SHAPE. Moderately elongate, rather robust, deep bodied (body depth mean 45.1%, range 43.2–46.8% of SL). Head especially robust, long (head length mean 37.0%, 36.3–38.0% of SL), wide (head width mean 19.9%, range 19.1–20.7% of SL), with large interocular distance (mean 12.5%, range 11.6–14.2% of SL). Frontal outline straight, nape and snout curved, anterior half of dorsal-fin base contour curved. Ventral outline curved. Snout long (mean 15.5%, 14.4–16.4% of SL). Preorbital distance long (mean 9.3%, range 8.5–10.0% of SL), preorbital bone much longer than high. Robust head with rather small eyes (mean 11.3%, range 10.3–12.0% of SL). Lips rather narrow, not turgid. Corner of mouth not reaching vertical from anterior margin of orbit, especially in largest specimens. Rather long and shallow caudal peduncle (CPL mean 13.8%, range 12.6–15.6% of SL; CPD mean 16.6%, range 15.5–17.1% of SL), and rather short last spine in dorsal fin (mean 15.6%, range 12.3–17.1% of SL). SCALES. Squ. long. (E1) scales 24 (5), 25 (3); 2 scales between L1 and dorsal fin anteriorly, 2 scales between L1 and L2. Upper lateral line (L1) with 15 (1), 16 (7) scales. Lower lateral line (L2) with 9 (4), 10 (3), 11 (1) scales; canal bearing scales on caudal fin: 0 in dorsal, 0-1 in median and 0 in ventral sequence. Cheek scales in 3 (8) series. Anterior portion of caudal fin scaly. FINS. Dorsal fin XII.11 (1), XIII.10 (1), XIII.11 (1), XIV.9 (1), XIV.10 (4). Soft anal fin pointed, 3 rd ray longest, reaching to middle of caudal fin or slightly beyond. Anal fin III.8 (8). Pectoral fin with rounded tip, reaching to above genital papilla to anal-fin origin (to 2 nd spine in one specimen); Pectoral fin 13 (8). Pelvic fin pointed, first ray slightly produced, reaching to origin of anal fin or base of 1 st spine of anal fin. Caudal fin rounded, without well-developed streamers or with only short streamers. GILL-RAKERS. 1 epibranchial, 1 in angle, and 5 (3), 6 (4), 7 (1) ceratobranchial rakers externally on first arch. JAW TEETH. An outer series of stronger, conical, sharply pointed, slightly recurved teeth, slightly increasing in size anteriorly, not worn, 15–22 in outer hemiseries in upper jaw. LOWER PHARYNGEAL JAW AND TEETH. Lower pharyngeal jaw (LPJ) as examined in two specimens (79.8– 98.9 mm) (Fig. 10) very delicate, most delicate LPJ of all described species of Bujurquina, very shallow vertically dorso-ventrally (bone at posterior end of dentigerous area less thick than length of largest posterior teeth in the smaller specimen, almost so in the larger specimen vs thicker than the teeth in all other species). LPJ also shortest and widest of all species, length/width ratio 0.42–0.45 (vs 0.50–0.64 in all other species). LPJ tooth-plate (due to the longest arms within Bujurquina) also one of the shortest in genus, length of dentigerous area/width of LPJ ratio 0.33–0.34 (vs 0.34–0.44 except B. tambopatae, B. moriorum and B. huallagae where also 0.33–0.34), Teeth slightly laterally compressed (most pronounced in posterior row), slightly bicuspid with main cusp posterior, central and posterior teeth largest, smaller towards outside, central teeth with flat-worn apex, others with pronounced tip. Coloration in alcohol Coloration limited to melanin patterns in preserved state, ground colour light yellowish-brownish, lighter towards whitish on chest and anterior abdomen, dusky greyish on anterior head, snout, and dorsum. Dark diffuse and wide interorbital band. Operculum silvery greyish. Up to four clearly defined grey lines between eye and mouth corner and on anterioir cheek interspersed with spots, rest of cheek as well as opercular series richly spotted. Suborbital stripe rather marrow and of uniform width, diffuse and ghost-like, bend from behind eye forward to cheek and then postero-ventrally to a variously developed suborbital stripe blotch in adults (never ocellated and with diffuse borders). In one collected juvenile specimen and in subadults straight (i.e., not bend), running from below eye (vs from behind eye) diagonally postero-ventrally. Midlateral band continuous from head to penultimate vertical bar on body, strongly pigmented and black, very wide anteriorly and gradually narrowing posteriorly. No interruption in vertical bar 5 (sensu Říčan et al. 2005), midlateral blotch (usually present and dominant in bar 5 in cichlasomatine cichlids) is absent. Lateral band continued on head across nape close behind eye. Body with five vertical bars plus one caudal peduncle bar and a caudal peduncle blotch (usually vertically elongated). The five body bars correspond to ontogenetic bars 2–5 with the anteriormost ontogenetic bars 6–7 fused into one wide bar below midlateral band but visible as two above it. Posterior body bars (2–4) narrow and tightly spaced, anterior bars (5, 6+ 7) wide and widely spaced. Bars darkest dorsally, reaching ventrally approximately to level of lower edge of caudal peduncle. Bars do not extend onto dorsal fin. Body scale centres (below midlateral band) with dark blotches, more pronounced in zones of vertical bars. Dorsal fin light grey, lappets indistinct, with a single narrow grey diagonal stripe per membrane in spinous part, with blotches on ventral portion of soft part. Anal fin light grey, with spots on last about four membranes. Caudal fin light grey with minute slightly elongate dark dots on anterior half, distally membranes hyaline with grey edges. Pelvic fin light grey, edge and produced portion of first ray white. Coloration in life Melanin patterns as in preserved. Lower head, cheek, and opercular series yellow-orange, with opalescent golden to azure blue lines and spots, arranged as up to four clearly defined lines between eye and mouth corner and on anterioir cheek interspersed with spots, rest of cheek as well as opercular series richly spotted. Fins orange, pelvic fin yellow, edge and produced portion of first ray white (opalescent). Spinous portion of dorsal fin with a single thin diagonal black line per membrane in juveniles and subadults, and with two lines per membrane in holotype and large adults. Lower lip pale greyish to indistinctly light azure blue. Midlateral blotch present only as a paler reflective area within the dark midlateral band (hence absent from coloration of preserved specimens). Habitat Bujurquina omagua sp. nov. was found only in small rainforest streams within the basins of the Sabalillo and Oran creeks. The localities (Fig. 11) were around 2 m wide streams, with shallow water (less than 1 m except in deeper pools) but deep mud and accumulated debris, blackish water, and only weak or moderate current. Bujurquina omagua has not been collected from the main streams of the Oran creek or from the lower sections of the Oran and Sabalillo creeks (Fig. 12), which have muddy water and where B. syspilus was found. Distribution Bujurquina omagua sp. nov. is only known from the Sabalillo and Oran creeks which empty into the Amazon River on either side of the village of Oran located on the first high ground just downstream from the mouth of the Napo into the Amazon, District Las Amazonas, Maynas Province, Department Loreto, Perú (Figs 1, 13). Morphometric differentiation of Bujurquina omagua sp. nov. Bujurquina omagua sp. nov. has a highly apomorphic head and body shape that sets it apart from the sympatric/parapatric species. When analyzed through PCA these species are arranged along the main tentic-lotic axis as corresponding to their lowland-upland habitats (Figs 14–15). The lotic/lentic ecomorphology dichotomy is in the PCA analyses best correlated with caudal peduncle length (long vs short), caudal peduncle depth (narrow vs deep), body depth (narrow vs deep), the size of the eye (orbital diameter; small vs large), pectoral fin length (short vs long), and last dorsal fin spine length (short vs long). The remaining characters are not correlated with the main ecomorphological dichotomy (i.e., interocular distance, head width, head length, preorbital distance, snout length, and first ventral fin ray length) (Figs 14–15). The lotic/lentic ecomorphology dichotomy is best visible in the analysis including all central western Amazonian species (Figs 1 and 14), while the diagnostic characters of Bujurquina omagua sp. nov. are best visible in the analysis excluding the westernmost and most highland species B. zamorensis (Fig. 15). Bujurquina omagua is in the PCAs distinguished from the sympatric/parapatric species predominantly by characters not correlated with the lotic-lentic, namely large head, wide head, long snout, and long preorbital dostance. All these diagnostic characters are in line with the diagnosis of the species based on means and ranges of the morphometric characters (see above). Bujurquina omagua sp. nov. has an outlying LPJ shape that can be described as the most delicate LPJ found among the valid species of Bujurquina (Fig. 16). The LPJ of Bujurquina omagua (studied in two specimens, see above) as expressed by proportional measurements is the shortest and widest of all species (L/W ratio) and the LPJ tooth-plate is the shortest in the genus (Ld/W ratio). Additionaly to this the LPJ is very shallow vertically dorso-ventrally, but this character was scored as binary, in comparison to the length of teeth (see Results), and thus not included in the PCA analysis. Paradoxically, the most delicate LPJ of B. omagua sp. nov. is associated with one of the largest heads among species of Bujurquina (together with B. labiosa) and with the longest snout among species of Bujurquina. A similar head and snout shape in B. oenolaemus is however associated with the most robust LPJ (Fig. 16) of this molluscivorous species. A similar combination of a long snout and large head with a very delicate LPJ as in B. omagua sp. nov. is however also known from the cichlid genus Australoheros Říčan & Kullander, 2006 in the species A. forquilha Říčan & Kullander, 2008 and A. ykeregua Říčan, Piáleck, Almirón & Casciotta, 2011 (Říčan & Kullander 2008; Říčan et al. 2011). Phylogeny of Bujurquina and phylogenetic position of Bujurquina omagua sp. nov. Phylogenetic analyses of the 1055 characters cytb data matrix performed with MP in PAUP* (including all ingroup sequences) and BI analyses in MrBayes and BEAST (performed with the corresponding haplotypes data matrix) provided robust and very similar results. BI runs in independent analyses with the best-fitting model of evolution (GTR+I+G) converged well (ESS>200 for all parameters; burn-in 10%) and led to identical topologies under the same settings. The NJ and MP analyses were done with the complete dataset, the BI and BEAST analyses with the haplotype dataset. No phylogenetic differences were found between the MP, BI and BEAST analyses, and hence only the BEAST analysis is shown in Fig. 17. The phylogenetic reconstructions divide Bujurquina into two main clades that can be diagnosed by patterned vs unpatterned dorsal fin, corresponding in geographical terms to Northern vs Southern group (Figs 1 and 17). The main biogeographic dichotomy within the genus between the Southern and Northern groups is within the present upper Ucayali basin in Peru (Fig. 1). The two main clades of Bujurquina are dated as having diverged at 16.6 Ma. Within the Southern group the two southern-most species from Argentina, Paraguay, Brazil and Bolivia are sister species (B. vittata and B. oenolaemus), and they are a sister group to the clade composed of the Peruvian B. eurhinus and B. tambopatae as sister species, followed by the Bolivian B. sp. Bolivia and then the Peruvian B. robusta. The phylogenetically basal-most species of the Southern group is the Peruvian B. labiosa. The Peruvian species are thus in basal positions within the Southern group, and they also have the longest internodes and the earliest dates of divergence based on molecular clock dating, with the time frame of divergence among the Peruvian species dated between 12.4 Ma and 3.0 Ma (Fig. 17). The Northern group of Bujurquina is made up of two highly divergent clades (Fig. 17) unlike the situation in the Southern group. The first clade within the Northern group shows a younger basal divergence at 3.9 Ma and includes, as a basal species, the here described B. omagua sp. nov., and then, among the Peruvian species, B. huallagae and B. syspilus. Samples of the morphologically and biogeographically Southern group species B. megalospilus are found within B. syspilus together with some samples of the Southern gro