Creagrutus saxatilis Vari & Harold 2001

Creagrutus saxatilis, USNM 341480, 1, 47.6 mm, paratype; Brazil, Distrito Federal, Rio Maranhão

Creagrutus seductus, USNM 342231, 1, 60.8 mm, paratype; Brazil, Mato Grosso, upper Rio Araguaia basin, Município de Barra do Garças.

Creagrutus taphorni, USNM 357730, 2, 50.7–51.1 mm; Venezuela, Miranda, El Amoladero, Río Guiare. USNM 357729, 3, 40.7–62.7 mm; Venezuela, Río Guaire, near Caracas.

Creagrutus ungulus, USNM 303066, 3, 55.0–53.5 mm, paratypes; Peru, Madre de Dios, Río Alto Madre de Dios.

Creagrutus saxatilis

DIAGNOSIS.—The combination of the possession of premaxillary dentition arranged in the three components generalized for most of the species of Creagrutus and Piabina without a distinctly larger gap between the first and second teeth of the primary series, 2 or 3 teeth on the maxilla, 6, rarely 5, teeth in the primary tooth row of the premaxilla, 5 dentary teeth, 37 to 39 lateral line scales without a lamellar process over each pore, 9 to 11 predorsal median scales, 4 scale rows between the dorsal-fin origin and the lateral line, 3 scale rows between the anal-fin origin and the lateral line, 2 post-anal median scales to the anal-fin origin, 36 to 38 vertebrae, 11 or 12 branched anal-fin rays, 8 to 10 gill rakers on the upper limb of the first gill arch, 11 to 13 gill rakers on the lower limb of the first gill arch, the distance from the snout to the anal-fin origin (60.2%–65.8% of SL), the distance from the dorsal-fin origin to the anal-fin origin (28.3%–34.9% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (25.3%–30.6% of SL), the caudal peduncle depth (11.3%–12.2% of SL), the anal-fin length (14.9%–18.1% of SL), the dorsal-fin length (18.5%–22.7% of SL), the snout length (26.6%–31.7% of HL), the interorbital width (31.6%–36.4% of HL), the moderately developed third infraorbital with its anteroventral portion contacting the horizontal limb of the preopercle, the lack of a series of dark midlateral spots on the body, the vertically elongate humeral mark, and the absence of a discrete patch of dark pigmentation on the middle portion of the anterior dorsal-fin rays distinguishes Creagrutus saxatilis within the clade composed of Creagrutus and Piabina.

DESCRIPTION.—Morphometric and meristic data for Creagrutus saxatilis in Table 52. Head and anterior portion of body moderately robust in smaller specimens, distinctly robust in largest specimens examined. Greatest body depth at vertical through pelvic-fin insertion in smaller specimens, at that point or shifted slightly anteriorly in larger individuals. Dorsal profile of head distinctly convex from margin of upper lip to vertical through posterior nostril, straight to slightly convex from that point to tip of supraoccipital spine. Interorbital region distinctly convex transversely. Dorsal profile of body gently convex from tip of supraoccipital spine to dorsal-fin origin, with slight change in alignment relative to profile of head in larger specimens. Predorsal surface of body somewhat flattened transversely anteriorly in larger specimens, with middorsal ridge proximate to dorsal-fin insertion. Ventral profile of head with distinct obtuse angle at anteroventral cornerof dentary, nearly straight from that point to isthmus in smaller specimens, gently convex in that region in larger individuals. Prepelvic region of body nearly straight in smaller specimens of both sexes, becoming increasingly convex in larger individuals. Prepelvic region obtusely flattened transversely in smaller specimens, distinctly rounded transversely in larger females.

Characters A B

Morphometrics

Standard length 80.5 38.1–62.3

1. Snout to anal-fin origin 65.7 60.2–65.8

2. Snout to pelvic-fin insertion 48.1 43.1–49.0

3. Snout to pectoral-fin insertion 25.0 22.9–26.6

4. Snout to dorsal-fin origin 47.0 44.4–49.0

5. Dorsal-fin origin to hypural joint 59.5 54.2–59.0

6. Dorsal-fin origin to anal-fin origin 34.9 28.8–34.5

7. Dorsal-fin origin to pelvic-fin insertion 30.3 25.3–30.6

8. Dorsal-fin origin to pectoral-fin insertion 34.5 29.8–35.4

9. Caudal peduncle depth 11.8 11.3–12.2

10. Pectoral-fin length 20.1 15.4–22.0

11. Pelvic-fin length 15.7 14.1–17.4

12. Dorsal-fin length 19.4 18.5–22.7

13. Anal-fin length 16.4 14.9–18.1

14. Head length 26.1 24.7–26.9

15. Postorbital head length 46.7 41.6–47.7

16. Snout length 30.5 26.6–31.7

17. Bony orbital diameter 32.4 31.6–36.0

18. Interorbital width 34.2 31.6–36.4

Meristics

Lateral line scales 39 37–39

Scale rows between dorsal-fin origin and lateral line 4 4

Scale rows between anal-fin origin and lateral line 3 3

Predorsal median scales 10 9–11

Branched dorsal-fin rays 8 8

Branched anal-fin rays 11 11–12

Branched pelvic-fin rays 6 6–7

Pectoral-fin rays 12 11–13

Vertebrae 37 36–38

Head obtusely pointed in lateral view, more compressed in dorsal view. Upper jaw longer than, and overhanging, lower jaw. Snout slightly fleshy anteromedially and above upper lip, fleshiness less apparent in larger specimens, which have scattered papillae anteromedially and along lateral surface of lip. Papillae more concentrated on ventral margin of lip and on folds and plicae extending between outer and medial premaxillary teeth. Lower lip moderately fleshy, less so in largest specimens, with papillae mostly limited to dorsal margin.

Infraorbital series moderately developed. Anterior portion of ventral margin of third infraorbital barely approaching horizontal limb of preopercle in smaller specimens, in contact with preopercle along approximately one-third of its horizontal length in largest individuals examined. Posterior margins of third through fifth infraorbitals falling distinctly short of vertical limb of preopercle posteriorly. Gap between posterior margins of infraorbitals and vertical limb of preopercle narrowing dorsally.

Premaxillary dentition in three series: primary row curved, typically with 6 teeth, few specimens with only 5 teeth, without pronounced gap between first and second tooth of series but with medial tooth separated from anterior tooth of contralateral series; triangular cluster of 3 larger teeth; and single tooth of form similar to that of primary series occurring slightly anterolateral of fourth tooth of main premaxillary tooth row. Maxilla with 2 or 3 tricuspidate teeth. Dentary with 5 tricuspidate teeth, cusps on last tooth barely apparent; first and second teeth distinctly larger than other teeth in series, second tooth slightly larger than first tooth and approximately twice height of third tooth; fourth and fifth teeth graded in size, distinctly smaller than third tooth and compressed.

Dorsal-fin rays ii,8 in all specimens. Dorsal-fin origin at vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave. Anal-fin rays ii, 11–12. Profile of distal margin of anal fin concave in all specimens, more so in largest examined individuals. Mature males with hooks present on first and second branched anal-fin rays. Pectoral-fin rays i,10–12. Tip of pectoral fin extending posteriorly approximately to 1 or 2 scales from pelvic-fin insertion. Pelvic-fin rays i,6,i in most specimens, i,7 in two largest, apparently female, individuals. Tip of pelvic fin extending posteriorly to anus or to region between anus and anal-fin origin. Mature males with hooks on all branched pelvic-fin rays.

Gill rakers 8–10 + 13–14.

COLORATION IN ALCOHOL.—Overall coloration yellow to tan. Dorsal surface of head with numerous chromatophores, particularly overlying fontanelles and adjoining regions. Series of deep-lying, dark chromatophores on membranes overlying brain, with notable variation in concentration between comparable-sized specimens collected at same time. Deep-lying chromatophores overlying brain masked by bones of skull and intracranial adipose deposits in larger individuals. Chromatophore field more concentrated on snout and anteromedial portions of upper lip. Region anterior to nostrils with dark chromatophores somewhat more concentrated than in relatively dark proximate regions, but resultant crescent-shaped field not as apparent as in some congeners. Region ventral of nostrils and anteroventral to orbit with broad streak of dark chromatophores that terminate ventral of eye. Band of chromatophores ventral and posterior to orbit often present in many congeners absent. Dorsal portions of infraorbitals and opercle with scattered, dark chromatophores.

Scales of dorsolateral portion of body with relatively large, dark chromatophores arranged in irregular pattern along posterior scale margin and more concentrated on basal portion of exposed portion of scale. Chromatophore fields most concentrated and nearly continuous middorsally. Overall form of humeral mark variable, but vertically elongate overall, often with dorsal portion anteriorly inclined. Intensity of pigmentation typically greatest in lower two-thirds of humeral mark, with overall relative intensity more pronounced in smaller examined specimens. Diffuse midlateral body stripe formed by small, dark, surface chromatophores. Stripe more distinct in smaller specimens and extending posteriorly from humeral mark to rear of caudal peduncle. Stripe blending into background coloration in larger individuals and not, or barely, apparent in region anterior to vertical through dorsal-fin origin. Stripe vertically expanded posteriorly in some specimens.

Dorsal fin with scattered, dark chromatophores along distal two-thirds of anterior fin membranes. Anal fin with basal one-half to two-thirds of rays outlined by narrow lines of dark pigmentation. Caudal-fin rays irregularly outlined by dark chromatophores. Concentration of chromatophores over basal portion of middle caudal-fin rays forming diffuse spot in smaller specimens, spot continuous anteriorly with midlateral stripe on body. Caudal spot not obvious in all larger individuals examined. Pectoral and pelvic fins hyaline or with scattered, dark chromatophores on rays and membranes.

ETYMOLOGY.—The species name, saxatilis, from the Latin for among rocks, refer to the rocky substrate of the type locality of this species.

ECOLOGY.—The collecting locality for a portion of the paratype series (USNM 341480) is an upland river, approximately 30 m wide with a fast to moderate flow of moderately turbid water over a rocky and sandy bottom. Creagrutus saxatilis was collected sympatrically with C. menezesi at one locality in pools within the exposed riverbed below the dam of the Serra da Mesa Reservoir during the filling of the lake.

Stomach contents of the one specimen prepared for clearing and staining in this study consisted exclusively of chopped-up seeds.

DISTRIBUTION.—Creagrutus saxatilis is known only from the upper portions of the Rio Tocantins system in Goiás and Distrito Federal, Brazil (Figure 83, dots).

MATERIAL EXAMINED.—31 specimens (23, 38.1–81.7).

HOLOTYPE.—BRAZIL. Goiás: Niquelândia, Rio Indaial, left bank tributary of Rio Maranhão, upper Rio Tocantins basin (14°12′S, 48°37′W), collected by G.W. Nunan and D.F. Moraes, Jr., 9 Oct 1985, MNRJ 14544, 1 (80.5).

PARATYPES.—17 specimens (17, 38.1–62.3).

BRAZIL. Distrito Federal: Rio Maranhão, upper Rio Tocantins basin, approximately 35 air km N of Brasilia (approximately 15°32′S, 47°49′W), collected by W.C. Starnes et al., 14 Nov 1984, USNM 341480, 6 (39.9–48.4; one specimen cleared and counterstained for cartilage and bone). Goiás: Uruaçu, Córrego Novo, left bank tributary of Rio Palmeira, left bank tributary of Rio Maranhao, upper Rio Tocantins basin (14°30′S, 48°47′30″W), collected by G.W. Nunan and D.F. Moraes, Jr., 17 Oct 1985, MNRJ 12590, 3 (38.1–41.3). Niquelandia, Rio Indaial, left bank tributary of Rio Maranhão, upper Rio Tocantins basin (14°12′S, 48°37′W), collected with holotype, MNRJ 12641, 3 (60.1–62.3). Niquelândia, Arroio Arara, approximately 500 m from mouth of Rio Maranhão, in Rosariana (14°01′S, 48°25′W), MCP 15977, 2 (39.9–58.6). Minaçu-Colinas do Sul, Rio Tocantins, in pools formed by left bank riacho during filling of Serra da Mesa Reservoir (approximately 13°50′S, 48°19′W), collected by D.F. Moraes et al., 28 Oct to 3 Nov 1996, MNRJ 17335, 3 (39.3–46.1).

NONTYPE SPECIMENS.—13 specimens (5, 60.8–81.7).

BRAZIL. Goiás: Rio Maranhão into Rio Tocantins, CAS 69254, 5 (60.8–81.7). Minaçu-Colinas do Sul, Rio Tocantins, in pools formed by left bank riacho during filling of Serra da Mesa Reservoir (approximately 13°50′S, 48°19′W), MNRJ 17336, 4; USNM 350450, 4.