Lateral view of anterior portion of snout of A, Sternarchorhynchus oxyrhynchus, ANSP 162670; and B, Sternarchorhynchus caboclo, INPA 10594, showing differing degree of development of mouth and fold of skin at rear of rictus.

Contexts in source publication

Context 1

... of internal features of U. magdalenensis by Albert (2001) and Triques (2005) apparently was limited to characters shown in the partial illustra- tions of head osteology in the original description by Miles (1945: fig. 11). This impediment resulted in numerous uncoded characters and was encumbered by apparent errors in those illustrations. Of note is the lateral ethmoid which, although present in speci- mens of Ubidia examined in this study, was absent from the illustration with its absence versus presence coded as unknown by Triques (2005). A lateral ...

Context 2

... of the proximate outgroups (Orthosterna- rchus, Sternarchorhamphus), along with Sternarch- ella orthos and all species of Sternarchorhynchus with the exception of S. goeldii and S. oxyrhynchus, have notably short mouths with the posterior limit of the gape falling short of the vertical through the posterior nares (state 0; Fig. 1B). Although the mouths in S. goeldii and S. oxyrhynchus are quite short along the snout axis compared to those in most fishes including many gymnotiforms (e.g. Magosternarchus, Lundberg et al., 1996: fig. 2) they are, nonetheless, distinctly longer than the form of the mouth present in all remaining species of Sternarchorhynchus. As a ...

Context 3

... (e.g. Magosternarchus, Lundberg et al., 1996: fig. 2) they are, nonetheless, distinctly longer than the form of the mouth present in all remaining species of Sternarchorhynchus. As a consequence, the gape in S. goeldii and S. oxyrhyn- chus extends posteriorly distinctly beyond the vertical running through the posterior nares (state 1; Fig. 1A) rather than terminating short of that landmark. This character could not be coded for the species of Platyurosternarchus or the outgroups other than Orthosternarchus, Sternarchorhamphus, and Sterna- rchella orthos. In those taxa the proportionally dis- tinctly posterior location of the nares relative to the location of the apertures ...

Context 4

... in the Amazon basin, a region outside the known range of the species and is likely to represent another species. Our analy- sis found that the upper lip lacks a skin fold in the species of Orthosternarchus, Platyurosternarchus, and Sternarchorhamphus. Within Sternarchorhynchus the fold is similarly absent in S. goeldii and S. oxyrhyn- chus (Fig. 1A). Both of those species of Sternarcho- rhynchus also share a mouth form unique in the genus (see character 1). All other species of Sternar- chorhynchus have a distinct fold within the skin of the upper lip ( Fig. 1B) with that feature also present in Sternarchella orthos amongst the more distant ...

Context 5

... and Sternarchorhamphus. Within Sternarchorhynchus the fold is similarly absent in S. goeldii and S. oxyrhyn- chus (Fig. 1A). Both of those species of Sternarcho- rhynchus also share a mouth form unique in the genus (see character 1). All other species of Sternar- chorhynchus have a distinct fold within the skin of the upper lip ( Fig. 1B) with that feature also present in Sternarchella orthos amongst the more distant ...

Context 6

... of premaxillary teeth is the common con- dition across the Gymnotiformes. The species of Orthosternarchus (Hilton et al., 2007: fig. 12), Sterna- rchorhynchus ( Figs 2, 3), and Sternarchorhamphus (Campos-da-Paz, 1995: fig. 4) have premaxillary teeth present, albeit with the form of the dentition on the bone varying amongst those taxa. Premaxillary den- tition is, in contrast, lacking in P. crypticus and P. macrostoma. Amongst the more distant outgroups included in the ...

Context 7

... anterior portion of the maxilla in most species of Sternarchorhynchus is moderately expanded into a plate-like region (state 0; Fig. 4A) with a similar condition also present amongst the examined out- group species in the included species of Apteronotus, along with Orthosternarchus tamandua (Hilton et al., 2007: fig. 12), Sternarchorhamphus muelleri and Ster- narchogiton labiatus. Sternarchorhynchus axelrodi and S. mormyrus have that portion of the maxilla proportionally further expanded into an approxi- mately square plate with irregular margins (state 2; Fig. 4B). Two other species of Sternarchorhynchus (S. goeldii, S. oxyrhynchus) alternatively ...

Context 8

... have a smooth, variably convex ventral margin of the main body of the bone (state 0; Fig. 4C). Other examined Sternarchorhynchus species alterna- tively, have distinct concavities along the main body of the maxilla (state 1; Fig. 4A, B). Such a concavity of the maxilla is also present in Orthosternarchus tamandua (Hilton et al., 2007: fig. 12) amongst the examined ...

Context 9

... anterior portion of the fleshy covering of the dentary is slightly to moderately developed in out- groups to Sternarchorhynchus along with most members of the genus (state 0; Fig. 1B). Sternarcho- rhynchus goeldii and S. oxyrhynchus, in contrast, have a very well-developed, somewhat distally pointed, fleshy pad at the anterodorsal limit of the dentary (state 1; Fig. 1A). This dorsally directed pad overlaps the anterior portion of the snout when the mouth is ...

Context 10

... of the fleshy covering of the dentary is slightly to moderately developed in out- groups to Sternarchorhynchus along with most members of the genus (state 0; Fig. 1B). Sternarcho- rhynchus goeldii and S. oxyrhynchus, in contrast, have a very well-developed, somewhat distally pointed, fleshy pad at the anterodorsal limit of the dentary (state 1; Fig. 1A). This dorsally directed pad overlaps the anterior portion of the snout when the mouth is ...

Context 11

... ossification running along the dorsal margin of the anguloarticular and the posterior portion of the well-developed Meckel's cartilage (Fig. 5). Comparable overall morphologies of the bone occur in the other outgroup taxa in this analysis [A. albifrons, A. cuchillo, A. rostratus, 'A.' apurensis, Orthosternarchus tamandua (Hilton et al., 2007: fig. 12b), Sternarchella orthos, and Sternar- chorhamphus muelleri (Campos-da-Paz, 1995: fig. 5)]. A small, round ossification positionally comparable to the coronomeckelian bone of other gymnotiforms is present in an approximately 40 mm TL specimen of an unidentified species of Sternarchorhynchus stew- arti. That element is comparable to the ...

Context 12

... cartilage is well developed across gymno- tiforms and immediate outgroups to Sternarchorhyn- chus [Orthosternarchus tamandua (Hilton et al., 2007: fig. 12b), Platyurosternarchus (Fig. 5), Sternar- chorhamphus muelleri (Campos-da-Paz, 1995: fig. 5)]; a condition comparable to that in most fishes. Within the Gymnotiformes, Meckel's cartilage most often has the form of an anteriorly attenuating body arising posteriorly from a distinct process on the medial wall of the anteromedial process of ...

Context 13

... than the posteroventral process of the dentary. The latter process runs ventral to the anguloarticular and some- times along at least a portion of the ventral margin of the retroarticular (state 0; Fig. 5) (for conditions in some more distantly related gymnotiform taxa see Mago-Leccia, 1978: fig. 8; Mago-Leccia et al., 1985: fig. 3;Albert, 2001: fig. 10). The species of Sternar- chorhynchus alternatively have posterodorsal and posteroventral processes of the dentary of approxi- mately identical lengths or in some instances with the dorsal process slightly longer (Figs 6, 7). This condi- tion is approximated in Sternarchella orthos (Lund- et al., 1996: fig. 3c) amongst the outgroup ...

Context 14

... posteroventral process of the dentary that extends ventral of the anterior portion of the angu- loarticular is typically a relatively robust process in gymnotiforms including proximate outgroups such as Orthosternarchus tamandua (Hilton et al., 2007: fig. 12), both species of Platyurosternarchus (Fig. 5), and Sternarchorhamphus muelleri (Campos-da-Paz, 1995: fig. 4). That morphology also occurs in the other outgroup apteronotids included in this study. Amongst all of those taxa, the process is either rela- tively broad vertically along most of its anteroposte- rior extent or gradually ...

Context 15

... in the other outgroup apteronotids included in this study. Amongst all of those taxa, the process is either rela- tively broad vertically along most of its anteroposte- rior extent or gradually tapers to a point distally with a resultant overall triangular morphology (MagoLeccia, 1978: fig. 8; Mago-Leccia et al., 1985: fig. 3; Albert, 2001: fig. 10). The species of Sternarchorhyn- chus have the posteroventral process of the dentary dramatically restructured into a very narrow strut of bone that borders a major portion of the ventral margin of the anteroposteriorly elongate anguloar- ticular (Figs 6, ...

Context 16

... in S. mesensis) have the posteroventral process of the dentary extending further posteriorly (state 0; Fig. 6), with resultant contact of the posteroventral process of the dentary with the posteroventral process of the angulo- articular. A comparable contact between those ele- ments occurs in Orthosternarchus tamandua (Hilton et al., 2007: fig. 12), Sternarchorhamphus muelleri (Campos-da-Paz, 1995: fig. 4), the species of Platyurosternarchus, and the more distant out- groups of this analysis (state ...

Context 17

... anterior portion of the anguloarticular that articulates with the posterior region of the dentary is relatively broad in most gymnotiforms (e.g. Albert, 2001: fig. 10) including the proximate outgroups to Sternarchorhynchus in this study [Orthosternarchus tamandua (Hilton et al., 2007: fig. 13), the species of Platyurosternarchus, and Sternarchorhamphus muel- leri]. All of the outgroups also have a distinct process that arises from the medial surface of the anguloar- ticular and serves as the ...

Context 18

... anterior portion of the anguloarticular that articulates with the posterior region of the dentary is relatively broad in most gymnotiforms (e.g. Albert, 2001: fig. 10) including the proximate outgroups to Sternarchorhynchus in this study [Orthosternarchus tamandua (Hilton et al., 2007: fig. 13), the species of Platyurosternarchus, and Sternarchorhamphus muel- leri]. All of the outgroups also have a distinct process that arises from the medial surface of the anguloar- ticular and serves as the posterior limit of Meckel's cartilage (Fig. 5). Amongst the species of Sternarcho- rhynchus, the anterior portion of the ...

Context 19

... highly divergent forms of the posteroventral portion of the anguloarticular are found in Sternar- chorhynchus and the other gymnotiforms incorpo- rated into this study. In Sternarchorhamphus muelleri (Campos-da-Paz, 1995: fig. 5) and Orthoster- narchus tamandua (Hilton et al., 2007: fig. 12b) the posteriormost portion of the anguloarticular is situ- ated within the dorsal portion of the joint between the anguloarticular and retroarticular. This portion of the anguloarticular is incorporated into the socket receiv- ing the articular condyle of the quadrate. The retroar- ticular in these two species has an anteriorly ...

Context 20

... receiv- ing the articular condyle of the quadrate. The retroar- ticular in these two species has an anteriorly directed process extending under the posterior portion of the anguloarticular (state 0) with this condition also present in the other outgroups. The process is mod- erately developed in Orthosternarchus tamandua (Hilton et al., 2007: fig. 12) and extends further ante- riorly in Sternarchorhamphus muelleri. The species of Platyurosternarchus and Sternarchorhynchus have the posteroventral portion of the anguloarticular extending further posteriorly, forming a distinct pos- teriorly attenuating process that extends under the anterior portion of the retroarticular (state 1; ...

Context 21

... of Sternarchorhynchus and its immediate outgroup species, P. crypticus and P. macrostoma, along with the basal apteronotids Orthosternarchus tamandua (Hilton et al., 2007: fig. 12) and Sternar- chorhamphus muelleri have teeth arranged in one or more rows along the dorsal portion of the dentary. These taxa also bear a patch of comparable dentition on the ventral surface of the premaxilla other than for the species of Platyurosternarchus, which lack upper jaw dentition. The tooth form differs amongst these taxa, ...

Context 22

... of the teeth on the dentary is consis- tently on the inner surface of the dentary in the species of Sternarchorhynchus, Sternarchorhamphus muelleri (Campos-da-Paz, 1995: fig. 5), Orthosternar- chus tamandua (Hilton et al., 2007: fig. 12), and the other apteronotid outgroups in this study other than P. crypticus and P. macrostoma. The dentition in Platyurosternarchus instead attaches to the outer surface of the dentary. Megadontognathus, an apter- onotid genus not amongst the outgroup taxa of this study, has teeth arising from the outer surface of the dentary. Dentary ...

Context 23

... anterior portion of the palatoquadrate cartilage (the pars autopalatine of Hilton et al., 2007: fig. 11) ranges from moderately to well developed in most of the apteronotids incorporated into this study. Although the palatoquadrate cartilage is somewhat reduced in Platyurosternarchus relative to the condi- tion in some other apteronotids, the cartilage remains an overall moderately well-developed, triangular structure (Fig. 8). ...

Context 24

... chus species have an unusual endopterygoid that is very narrow along the anteroposterior axis and reduced along the transverse plane. As a consequence, the endopterygoid is proportionally higher vertically than wide transversely state 1; (Figs 9, 10). ...

Context 25

... rhynchus, and Ubidia by Triques (2005; ossification termed the mesopterygoid therein). The landmark delimiting those portions of the bone was not identi- fied. That issue aside, although the endopterygoid is distinctly elongate in Sternarchorhynchus (Fig. 9), the proportional length of the bone in Platyurosternar- chus ( Fig. 8; Albert, 2001: fig. 31a) is comparable to that not only in Ubidia (Miles, 1945: fig. 11) but also species of Apteronotus (e.g. A. albifrons, Chardon & De La Hoz, 1974: fig. 6; Apteronotus bonapartii, Hilton & Cox-Fernandes, 2006: fig. 5). Elongation of the element is thus of broader occurrence and a more encompassing analysis is necessary to determine the ...

Context 26

... mesopterygoid therein). The landmark delimiting those portions of the bone was not identi- fied. That issue aside, although the endopterygoid is distinctly elongate in Sternarchorhynchus (Fig. 9), the proportional length of the bone in Platyurosternar- chus ( Fig. 8; Albert, 2001: fig. 31a) is comparable to that not only in Ubidia (Miles, 1945: fig. 11) but also species of Apteronotus (e.g. A. albifrons, Chardon & De La Hoz, 1974: fig. 6; Apteronotus bonapartii, Hilton & Cox-Fernandes, 2006: fig. 5). Elongation of the element is thus of broader occurrence and a more encompassing analysis is necessary to determine the phylogenetic level at which it is ...

Context 27

... typical form of the posterior portion of the endopterygoid in gymnotiforms including Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11), the species of Platyurosternarchus (Albert, 2001: fig. 31a), Sternarchorhamphus muelleri (Albert, 2001: fig. 31b), and examined outgroups is a vertically relatively expansive ossification closely applied and tightly attached to the lateral surface of portions of the quadrate and metapterygoid (state 0; Fig. 8). Sterna- rchorhynchus ...

Context 28

... typical form of the posterior portion of the endopterygoid in gymnotiforms including Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11), the species of Platyurosternarchus (Albert, 2001: fig. 31a), Sternarchorhamphus muelleri (Albert, 2001: fig. 31b), and examined outgroups is a vertically relatively expansive ossification closely applied and tightly attached to the lateral surface of portions of the quadrate and metapterygoid (state 0; Fig. 8). Sterna- rchorhynchus has the vertical extent of the posterior region of the ...

Context 29

... typical form of the posterior portion of the endopterygoid in gymnotiforms including Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11), the species of Platyurosternarchus (Albert, 2001: fig. 31a), Sternarchorhamphus muelleri (Albert, 2001: fig. 31b), and examined outgroups is a vertically relatively expansive ossification closely applied and tightly attached to the lateral surface of portions of the quadrate and metapterygoid (state 0; Fig. 8). Sterna- rchorhynchus has the vertical extent of the posterior region of the endopterygoid dramatically reduced to an elongate process ...

Context 30

... the reduced posterior portion of the endopterygoid with the lateral surface of the quadrate in the species of Sternarcho- rhynchus. Maximal connectivity of the endopterygoid and quadrate is achieved in S. goeldii and S. oxyrhyn- chus where these bones are fused into a single ossi- fication without trace in adults of the original line of contact ( Fig. 10; see character ...

Context 31

... other but separate in examined outgroup gymnotiforms and in all species of Sternarchorhyn- chus other than S. goeldii and S. oxyrhynchus (state 0; Fig. 9). These two species have the quadrate and endopterygoid fused into a single anteroposteriorly elongate ossification without any indication of the original joint between those elements (state 1; Fig. ...

Context 32

... gymnotiforms have a variably elongate, dorsally directed ascending process of the endoptery- goid arising from the dorsal surface of that bone (e.g. Sternarchella sima, Albert, 2001: fig. 31c). Such a process is present in S. mormyrus but absent across all of the other members of the genus exam- ined osteologically (state 1). The feature was, none- theless, included in the analysis because it may serve to define a small assemblage of species once the remaining recognized members of the genus are examined osteologically or ...

Context 33

... examined outgroups along with S. caboclo, Sternarchorhynchus chaoi, S. curvirostris, S. curumim, S. goeldii, Sternarchorhynchus higuchii, Sternarchorhynchus mendesi, S. mesensis, S. mormyrus, S. oxyrhynchus, and S. roseni, the liga- ment attaches onto the suspensorium solely via a small dorsal process extending from the endoptery- goid (state 0; Fig. 11A) that is best viewed from an oblique dorsoventral angle. Sternarchorhynchus brit- skii, Sternarchorhynchus cramptoni, S. gnomus, Ster- narchorhynchus hagedornae, Sternarchorhynchus inpai, Sternarchorhynchus jaimei, Sternarchorhyn- chus mareikeae, Sternarchorhynchus montanus, Ster- narchorhynchus retzeri, Sternarchorhynchus starksi, S. ...

Context 34

... have the quadrate also contributing the attachment of the pterygocra- nial ligament on the suspensorium. This attachment site most often has the form of a dorsal process extending along the surface of the dorsal process of the entopterygoid and often completely overlapping the corresponding portion of the entopterygoid from medial view (state 1; Fig. 11B). We were unable to code S. axelrodi for this feature from radiographs of the type ...

Context 35

... gymnotiforms in this study including the immediate outgroups in this analysis (e.g. P. macros- toma, Sternarchorhamphus muelleri; Albert, 2001: fig. 31a, b) have a variably well-developed plate-like process of the quadrate that extends dorsal of the articular condyle that contacts the lower jaw (state 0; Fig. 8). In the species of Sternarchorhynchus, the quadrate is dorsoventrally shallower and lacks this dorsal process on the bone (state 1; Figs 9, ...

Context 36

... straight or convex dorsal margin along the plate- like dorsal process of the quadrate typifies most gym- notiforms including all proximate outgroups for Sternarchorhynchus in this analysis [e.g. Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11); Ster- narchorhamphus muelleri (Albert, 2001: fig. 31a, b)]. As described under character 28, Sternarchorhynchus species have the quadrate reduced vertically. Sterna- rchorhynchus axelrodi, S. goeldii, S. mormyrus, and S. oxyrhynchus, nonetheless, retain a straight to slightly convex dorsal margin of the reduced quadrate comparable to ...

Context 37

... straight or convex dorsal margin along the plate- like dorsal process of the quadrate typifies most gym- notiforms including all proximate outgroups for Sternarchorhynchus in this analysis [e.g. Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11); Ster- narchorhamphus muelleri (Albert, 2001: fig. 31a, b)]. As described under character 28, Sternarchorhynchus species have the quadrate reduced vertically. Sterna- rchorhynchus axelrodi, S. goeldii, S. mormyrus, and S. oxyrhynchus, nonetheless, retain a straight to slightly convex dorsal margin of the reduced quadrate comparable to the form of that portion of the ossifi- cation in outgroups ...

Context 38

... As described under character 28, Sternarchorhynchus species have the quadrate reduced vertically. Sterna- rchorhynchus axelrodi, S. goeldii, S. mormyrus, and S. oxyrhynchus, nonetheless, retain a straight to slightly convex dorsal margin of the reduced quadrate comparable to the form of that portion of the ossifi- cation in outgroups (state 0; Fig. 10). All other members of Sternarchorhynchus have a distinctly concave dorsal margin to the quadrate (state 1; Fig. ...

Context 39

... have the lateral surface of the quadrate unelaborated (state 0), with the posterolateral region of this bone overlapped laterally by the endopterygoid [e.g. Orthosternarchus tamandua (Hilton et al., 2007: fig. 11)]. The posterolateral portion of the quadrate is exposed laterally but unelaborated in all Sternarcho- rhynchus species other than S. goeldii and S. oxy- rhynchus and is consequently coded as state 0 for these taxa (Fig. 9). Sternarchorhynchus goeldii and S. oxyrhynchus bear a lateral expansion of the lateral surface of the ...

Context 40

... coded as state 0 for these taxa (Fig. 9). Sternarchorhynchus goeldii and S. oxyrhynchus bear a lateral expansion of the lateral surface of the posterodorsal portion of the quadrate, with the expanded region having the form of a raised, laterally rounded, longitudinally aligned ridge termi- nating in a distinct posterior facet (state 1; Fig. 10) that articulates with a corresponding facet on the anterior surface of the metapterygoid (see character ...

Context 41

... joint in examined outgroups to Sternarchorhynchus and in all species in the genus other than S. curvirostris, S. goeldii, and S. oxyrhyn- chus (state 0; Fig. 9). These three species have the articulation of these ossifications shifted distinctly posteriorly relative to that landmark and situated ventral of the metapterygoid (state 1; Fig. ...

Context 42

... S. mareikeae, and S. starksi have a further development dorsally of the bony sheet such that it overlaps the lateral surface of the notch in the posteroventral portion of the quadrate. This expansion results in the lateral overlap of the anteroventral corner of the metapterygoid by the dorsal process of the quadrate in these species (state 1; Fig. ...

Context 43

... 4) or have a relatively short process that terminates approximately at, or slightly poste- rior of, the vertical through the ventral portion of the area of contact of the metapterygoid and quadrate (state 0). The latter condition is present in all exam- ined outgroups to Sternarchorhynchus [e.g. Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11); Platyurosternarchus (Albert, 2001: fig. 31a); Sternar- chorhamphus muelleri (Albert, 2001: fig. 31b)]. Ster- narchorhynchus species have a much more elongate posteroventral process of the quadrate. This process extends from the body of the ossification as a narrow flange of bone running ventral of the symplectic to a point at least as ...

Context 44

... terminates approximately at, or slightly poste- rior of, the vertical through the ventral portion of the area of contact of the metapterygoid and quadrate (state 0). The latter condition is present in all exam- ined outgroups to Sternarchorhynchus [e.g. Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11); Platyurosternarchus (Albert, 2001: fig. 31a); Sternar- chorhamphus muelleri (Albert, 2001: fig. 31b)]. Ster- narchorhynchus species have a much more elongate posteroventral process of the quadrate. This process extends from the body of the ossification as a narrow flange of bone running ventral of the symplectic to a point at least as far posterior as the vertical located ...

Context 45

... the vertical through the ventral portion of the area of contact of the metapterygoid and quadrate (state 0). The latter condition is present in all exam- ined outgroups to Sternarchorhynchus [e.g. Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11); Platyurosternarchus (Albert, 2001: fig. 31a); Sternar- chorhamphus muelleri (Albert, 2001: fig. 31b)]. Ster- narchorhynchus species have a much more elongate posteroventral process of the quadrate. This process extends from the body of the ossification as a narrow flange of bone running ventral of the symplectic to a point at least as far posterior as the vertical located two-thirds of the distance along the length of the ...

Context 46

... slender symplectic that from a lateral view gradually increases posteriorly in its vertical extent. As a consequence, the height of the posteriormost portion of the symplectic is approxi- mately one-fifth of its length (state 0). This symplectic form also occurs in A. cuchillo, A. rostratus, Orthoster- narchus tamandua (Hilton et al., 2007: fig. 11), P. crypticus, and Sternarchorhamphus muelleri in the outgroups (state 0). Sternarchorhynchus axelrodi, S. chaoi, S. goeldii, S. mormyrus, and S. oxyrhynchus have instead a distinctly more posterodorsally angled dorsal margin of the symplectic with a resultant greater disparity in the height of the anterior versus posterior portions ...

Context 47

... dorsal margin of the symplectic is straight to variably irregular in outgroups to Sternarchorhyn- chus (Hilton et al., 2007: fig. 11, for condition in Orthosternarchus tamandua) and nearly all species of the genus (state 0; Fig. 9). Sternarchorhynchus cramptoni, S. curumim, S. curvirostris, S. goeldii, S. hagedornae, S, mareikeae, S. oxyrhynchus, S. retzeri, S. starksi, and S. stewarti rather have the dorsal portion of the symplectic elaborated into an anteriorly ...

Context 48

... metapterygoid in outgroups to Sternarchorhyn- chus is approximately triangular [e.g. Orthosternar- chus tamandua (Hilton et al., 2007: fig. 11); Platyurosternarchus (Albert, 2001: fig. 31a); Sternar- chorhamphus (Albert, 2001: fig. 31b)] with the poste- rior portion tapering to a variably distinct point (state 0; Fig. 8). Species of Sternarchorhynchus, in contrast, have a more elongate metapterygoid with an overall quadrilateral form (state 1; Figs 9, ...

Context 49

... metapterygoid in outgroups to Sternarchorhyn- chus is approximately triangular [e.g. Orthosternar- chus tamandua (Hilton et al., 2007: fig. 11); Platyurosternarchus (Albert, 2001: fig. 31a); Sternar- chorhamphus (Albert, 2001: fig. 31b)] with the poste- rior portion tapering to a variably distinct point (state 0; Fig. 8). Species of Sternarchorhynchus, in contrast, have a more elongate metapterygoid with an overall quadrilateral form (state 1; Figs 9, ...

Context 50

... metapterygoid in outgroups to Sternarchorhyn- chus is approximately triangular [e.g. Orthosternar- chus tamandua (Hilton et al., 2007: fig. 11); Platyurosternarchus (Albert, 2001: fig. 31a); Sternar- chorhamphus (Albert, 2001: fig. 31b)] with the poste- rior portion tapering to a variably distinct point (state 0; Fig. 8). Species of Sternarchorhynchus, in contrast, have a more elongate metapterygoid with an overall quadrilateral form (state 1; Figs 9, ...

Context 51

... S. oxyrhynchus have a lateral elaboration of the dorso- lateral portion of the metapterygoid expanded into a thickened, laterally rounded, anteroposteriorly aligned ridge. This metapterygoid expansion is par- ticularly well developed anteriorly, where it forms a broad facet that articulates with a corresponding process of the quadrate (state 1, Fig. 10; see also character ...

Context 52

... Sternarchorhynchus and S. goeldii, S. oxyrhynchus, and S. mormyrus have the elongate posteroventral process of the quadrate running along and closely applied to the dorsal margin of the hori- zontal arm of the preopercle. In that condition the tip of the quadrate process is neither enveloped posteri- orly nor dorsally by the preopercle (state 0; Fig. 10). We were unable to code this feature for S. axelrodi. All remaining species of Sternarchorhynchus have the dorsal margin of the preopercle expanded dorsally in the region posterior to the tip of the posteroventral process of the quadrate. Consequently, the posterior- most portion of the quadrate lies within a depression along the ...

Context 53

... S. higuchii, S. inpai, S. jaimei, S. mareikeae, S. mendesi, S. mesen- sis, S. oxyrhynchus, S. retzeri, S. roseni, S. severii, and S. stewarti instead possess an anteroposteriorly longer horizontal arm of the preopercle terminating anteriorly somewhat, to distinctly, anterior of the vertical through the ventral portion of this joint (state 1; Fig. ...

Context 54

... S. gnomus, S. higuchii, S. hagedornae, S. inpai, S. jaimei, S. mareikeae, S. mendesi, S. mesen- sis, S. montanus, S. roseni, S. starksi, and S. stewarti also have concave canal segments such as those in congeners, but with the convexity of the laterosensory canal segments much less pronounced and in the form of distinctly shallow arcs (state 0; Fig. 13B). State 0 is also present in the outgroups in the three examined species of Apteronotus, Orthosternarchus tamandua, P. crypticus, Sternarchella orthos, Sternarchogiton labiatus, and Sternarchorhamphus ...

Context 55

... condition also occurs amongst more distant outgroups in A. albifrons, A. cuchillo, 'A.' apurensis, and Sternarchogiton labiatus. Sternarcho- rhynchus, in contrast, has the opercular margin dis- tinctly concave (Figs 9, 10) with this condition (state 1) also present amongst outgroups in A. rostratus, Orthosternarchus tamandua (Hilton et al., 2007: fig. 11), and Sternarchella orthos (Lundberg et al., 1996: fig. ...

Context 56

... The fourth element has a variable area of attachment ranging from the lateral surface of the posterior portion of the anterior ceratohyal to the lateral surface of the anterior region of the posterior ceratohyal. A fifth ray, when present, attaches to the area of the joint of the anterior and posterior ceratohyals (see MagoLeccia, 1978: fig. 13 for illustration of this arrange- ment of five rays in Eigenmannia virescens) or to the lateral surface of the posterior ceratohyal (see de Santana & Nogueira, 2006: fig. 3 for illustration of this condition in S. caboclo). Various authors have used total ray counts to advance hypotheses of phy- logenetic relationships (e.g. ...

Context 57

... it appears that loss of branchiostegal rays proceeds in an anterior posterior sequence that leads us to cast the discussion within that framework. The first ray is absent in Orthosternarchus tamandua, which also lacks the apparent second ray, retaining only a single branchiostegal ray attaching to the anterior ceratohyal (Hilton et al., 2007: fig. 13). The first ray is missing in all species of Platyuroster- narchus, the examined species of Apteronotus, and Sternarchella orthos, Sternarchogiton labiatus, and Sternarchorhamphus muelleri amongst the outgroup taxa (state 0) and uniquely in S. caboclo within Ster- narchorhynchus. Although this condition is autapo- morphic for S. caboclo ...

Context 58

... the anterior region of the posterior ceratohyal. Variation in the area of attachment forms a con- tinuum across the examined taxa and we coded only presence versus absence of the ray in this analysis. This posteriormost branchiostegal ray is absent (state 1) in both Sternarchorhamphus muelleri and Orthosternarchus tamandua (Hilton et al., 2007: fig. 13), but present in Platyurosternarchus and Ster- narchorhynchus (state 0). This ray is similarly present in the examined species of Apteronotus and Sternarchella orthos and Sternarchogiton ...

Context 59

... scheme of five total rays detailed above) of a length equal to, or shorter than, 1.5 times the distance from anterior limit of the ventral hypohyal to posterior limit of posterior cera- tohyal. Fourth branchiostegal rays of comparable relative lengths also occur in more distantly related outgroups [e.g. Eigenmannia virescens (Mago-Leccia, 1978: fig. 15)]. Sternarchorhamphus muelleri and Orthosternarchus tamandua have significantly longer fourth rays of lengths approximately three or more times the distance from the anterior limit of the ventral hypohyal to the posterior limit of the posterior ceratohyal (see Hilton et al., 2007: fig. 13 for Orthosternarchus tamandua). Although the ...

Context 60

... outgroups [e.g. Eigenmannia virescens (Mago-Leccia, 1978: fig. 15)]. Sternarchorhamphus muelleri and Orthosternarchus tamandua have significantly longer fourth rays of lengths approximately three or more times the distance from the anterior limit of the ventral hypohyal to the posterior limit of the posterior ceratohyal (see Hilton et al., 2007: fig. 13 for Orthosternarchus tamandua). Although the derived elongation of the fourth branchiostegal ray is not pertinent to the question of relationships within Ster- narchorhynchus, we included the character to provide structure to the outgroup phylogeny. A comparable elongation of the second branchiostegal ray attaching to the lateral ...

Context 61

... Orthosternarchus tamandua, Sternarchorham- phus muelleri, S. goeldii, S. mormyrus, and S. oxy- rhynchus, the anterior portion of the urohyal is narrow relative to the overall size of the bone with its transverse width approximately one-fifth or less of the length of the main body (state 0; Fig. 14A). Because of the reduction of the overall proportional length of the urohyal, the anterior portion of the urohyal is relatively wide relative to the overall size of the bone in species of Sternarchorhynchus other than S. goeldii, S. mormyrus, and S. oxyrhynchus. This is reflected in a transverse width of the urohyal that is ...

Context 62

... the anterior portion of the urohyal is relatively wide relative to the overall size of the bone in species of Sternarchorhynchus other than S. goeldii, S. mormyrus, and S. oxyrhynchus. This is reflected in a transverse width of the urohyal that is approximately one-third or more of the length of the main body of the ossification (state 1; Fig. 14B). The urohyal is dramatically reduced in size and modi- fied in form in the outgroup apteronotids other than P. crypticus, P. macrostoma, and Sternarchella orthos but, nonetheless, fits the definition of state 1 and was coded accordingly. This character was not coded for Sternarchogiton labiatus and the three examined species of ...

Context 63

... anterior margin of the urohyal is transversely nearly straight or at most slightly irregular in Orthosternarchus tamandua, P. crypticus, P. macros- toma, Sternarchorhamphus muelleri, and most Sternarchorhynchus species (state 0; Fig. 14A). Ster- narchorhynchus chaoi, S. cramptoni, S. curumim, S. hagedornae, S. higuchii, S. jaimei, S. mesensis, S. montanus, S. roseni, and S. stewarti alternatively have a distinct medial notch along the anterior margin of the urohyal (state 1; Fig. 14B). This char- acter could neither be coded for the other outgroup apteronotids in which ...

Context 64

... P. macros- toma, Sternarchorhamphus muelleri, and most Sternarchorhynchus species (state 0; Fig. 14A). Ster- narchorhynchus chaoi, S. cramptoni, S. curumim, S. hagedornae, S. higuchii, S. jaimei, S. mesensis, S. montanus, S. roseni, and S. stewarti alternatively have a distinct medial notch along the anterior margin of the urohyal (state 1; Fig. 14B). This char- acter could neither be coded for the other outgroup apteronotids in which the urohyals are dramatically reduced in relative size and also modified in form, nor for S. starksi, which had a deformed urohyal in the single available cleared and stained specimen of the species and S. axelrodi in the absence of cleaned and ...

Context 65

... the anterior portions of the first hypobranchials, the typical position for the end of the basihyal and as such it appears that basibranchial 1 is absent. We consequently identify the elongate anterior ossification as the basihyal. Apteronotus albifrons, A. cuchillo, A. rostratus, 'A.' apurensis, Orthosternarchus tamandua (Hilton et al., 2007: fig. 14), P. crypticus, P. macrostoma, Sternarch- ella orthos, Sternarchogiton labiatus, and Sternar- chorhamphus muelleri have this ossification ranging from rod-like to slightly expanded transversely ante- riorly, but without distinct lateral processes (state 0; Fig. 15). Within Sternarchorhynchus an unelaborated form of the basihyal (state ...

Context 66

... A. rostratus, 'A.' apurensis, Orthosternarchus tamandua (Hilton et al., 2007: fig. 14), P. crypticus, P. macrostoma, Sternarch- ella orthos, Sternarchogiton labiatus, and Sternar- chorhamphus muelleri have this ossification ranging from rod-like to slightly expanded transversely ante- riorly, but without distinct lateral processes (state 0; Fig. 15). Within Sternarchorhynchus an unelaborated form of the basihyal (state 0) is restricted to S. britskii, S. goeldii, S. higuchii, S. jaimei, S. oxyrhyn- chus, and S. roseni. Other species of Sternarchorhyn- chus have definite lateral processes along at least the posterior half of the bone (state 1; Figs 16, ...

Context 67

... majority of species of Sternarchorhynchus along with all of the examined outgroups have the second basibranchial constricted to a variable, but nonetheless pronounced, degree along its midlength (state 0). As a consequence, the element has a vari- able hour-glass shape from dorsal view (Figs 15, 16). In some outgroup taxa [e.g. ...

Context 68

... along with all of the examined outgroups have the second basibranchial constricted to a variable, but nonetheless pronounced, degree along its midlength (state 0). As a consequence, the element has a vari- able hour-glass shape from dorsal view (Figs 15, 16). In some outgroup taxa [e.g. Orthosternarchus tamandua (Hilton et al., 2007: fig. 14)], the second basibranchial is proportionally more elongate with a relatively less pronounced but still obvious midlength constriction. A subset of the species of Sternarcho- rhynchus (S. chaoi, S. cramptoni, S. curvirostris, S. hagedornae, S. jaimei, S. mesensis, S. mormyrus, S. retzeri, S. severii, S. starksi, and S. stewarti) have a ...

Context 69

... A subset of the species of Sternarcho- rhynchus (S. chaoi, S. cramptoni, S. curvirostris, S. hagedornae, S. jaimei, S. mesensis, S. mormyrus, S. retzeri, S. severii, S. starksi, and S. stewarti) have a bony plate extending laterally from the lateral margins of the constricted portion of the main body of the second basibranchial (state 1; Fig. 17). These lateral extensions result in parallel lateral margins to the second basibranchial from a dorsal view, albeit with the constricted main body of the bone still obvious; more so, in transmitted light (state 1). This character could not be coded for S. axelrodi from ...

Context 70

... region that extends along the lateral margin of the second basibranchial. Although outgroups to Sternarcho- rhynchus along with S. goeldii and S. oxyrhynchus have the anterior portion of this ossification some- what pointed overall, the region is not developed into a distinct narrow, often somewhat slightly medially curving process (state 0; Fig. 15). All Sternarchorhyn- chus species other than S. goeldii and S. oxyrhynchus have the anterior portion of the second hypobranchial more attenuate, with this anterior extension often slightly medially curving anteriorly (state 1; Figs 16, 17). 60. Degree of development of medial portion of second hypobranchial in adults: (0) with ...

Context 71

... (state 0; Figs 15, 17). Uniquely amongst the species examined herein, S. caboclo and S. higuchii lack that medial process of the second hypobranchial. They instead have the contralateral ossifications completely sepa- rated by the second basibranchial and the cartilage that lies between that ossification and the third basi- branchial (state 1; Fig. 16). This character could not be coded for in S. axelrodi from ...

Context 72

... viewed from the dorsal view, the fourth cera- tobranchial has nearly parallel lateral and medial margins, or tapers slightly anteriorly in Orthosterna- rchus tamandua (Hilton et al., 2007: fig. 14) and Ster- narchorhamphus muelleri (state 0). Most examined apteronotids and more distantly related gymnotiform taxa either retain that morphology of the fourth cera- tobranchial or have on occasion a lateral expansion of the anterior portion of that ossification (e.g. Rhabdoli- chops troschelii, Mago-Leccia, 1978: fig. 7). Species of ...

Context 73

... fourth infrapharyngobranchial is an anteropos- teriorly elongate, posteriorly wider cartilaginous body without ossification centres in both Orthosternarchus tamandua (Hilton et al., 2007: fig. 14) and Sternar- chorhamphus muelleri. An entirely cartilaginous fourth infrapharyngobranchial is, furthermore, general amongst other outgroups in the Apter- onotidae (e.g. Adontosternarchus, Mago-Leccia et al., 1985: fig. 5) and across the Gymnotiformes (e.g. the sternopygids Eigenmannia and Rhabdolichops, Mago- Leccia, 1978: figs 9, 17). ...

Context 74

... (e.g. the sternopygids Eigenmannia and Rhabdolichops, Mago- Leccia, 1978: figs 9, 17). It thus represents the primi- tive condition across the Gymnotiformes (state 0). The species of Sternarchorhynchus and Platyurosternar- chus have a well-ossified fourth infrapharyngobran- chial with an overall triangular, posteriorly widening form (state 1; Fig. 18). The ossified portion of the fourth infrapharyngobranchial is bordered anteriorly by a small cartilage cap that contacts the cartilages of the third epibranchial and third infrapharyngobran- chial and terminates posteriorly along a transversely elongate cartilage that broadly articulates with the cartilage along the anterior margin of ...

Context 75

... primary conditions of the cartilages along the anterior limits of the first epibranchial and the second infrapharyngobranchial occur in Sternarchorhynchus and its proximate outgroups. Orthosternarchus tamandua (Hilton et al., 2007: fig. 14), Sternar- chorhamphus muelleri, and other examined outgroup apteronotids have a moderately sized cartilage along the anterior margin of the first epibranchial. This cartilage extends solely along the lateral margin of the cartilage that caps the anterior limit of the ossi- fied portion of the second infrapharyngobranchial. In this ...

Context 76

... varying degrees along the anterior margin of that cartilage. As a consequence of this expansion of the anterior cartilage of the first epibranchial, the carti- lage at the anterior margin of the second infrapharyn- gobranchial in Platyurosternarchus and Sternarch- orhynchus lacks a broadly exposed margin anteriorly; a derived condition (state 1; Fig. 1). Myorhadoi are the superficial series of the inter- muscular bones that extend along the length of the body in gymnotiforms and are variably present in other fishes. The most common form of the large series of these ossifications present across the Gym- notiformes is a bony rod that progressively subdivides distally at both ends with ...

Context 77

... myorhadoi series located in the region of the body approximately one-quarter the distance between the rear of the abdominal cavity and the end of the anal fin. The myorhadoi in that region have a relatively long, curving, anteromedially directed extension arising from the medial surface of the rod-like central portion of the bone (states 1 and 2; Fig. 19A, B). Sternarchorhynchus chaoi uniquely also has a shorter anterodorsally orientated process arising from the dorsal surface of the myorhadoi at a point approxi- mately directly opposite to the base of the larger anteroventral extension of the ossification (state 2; Fig. 19B). This character could not be coded for S. axelrodi solely based ...

Context 78

... surface of the rod-like central portion of the bone (states 1 and 2; Fig. 19A, B). Sternarchorhynchus chaoi uniquely also has a shorter anterodorsally orientated process arising from the dorsal surface of the myorhadoi at a point approxi- mately directly opposite to the base of the larger anteroventral extension of the ossification (state 2; Fig. 19B). This character could not be coded for S. axelrodi solely based on radiographs of the ...

Context 79

... positionally somewhat similar expansions on the lateral margin of the ventral ethmoid in examined species of Apteronotus, along with Orthosternarchus tamandua (Hilton et al., 2007: fig. 10c), Sternarchella orthos, Sternarchogiton labiatus, and Sternar- chorhamphus muelleri lack the scythe-shaped process present in the vast majority of Sternarchorhynchus species. These outgroups have, in contrast, postero- laterally directed articular surfaces on the ventral ethmoid that form the anterior limit of anteroposte- riorly ...

Context 80

... genus spans approximately one-half the distance between the tip of the snout and the anterior margin of the opercle (state 1; Campos-da-Paz, 2000: fig. 6), with the extension reflected in the relative length of the mesethmoid versus the frontal. Juveniles of Sterna- rchorhynchus have a proportionally much shorter mesethmoid (compare Albert, 2001: fig. 17A, B) with that ossification progressively increasing in length ontogenetically. Although Orthosternarchus tamandua amongst the proximate outgroups also has an elongate overall head, the proportional elon- gation of the mesethmoid is much less pronounced in that species (Hilton et al., 2007: fig. 10) than in Sternarchorhynchus. We also ...

Context 81

... much shorter mesethmoid (compare Albert, 2001: fig. 17A, B) with that ossification progressively increasing in length ontogenetically. Although Orthosternarchus tamandua amongst the proximate outgroups also has an elongate overall head, the proportional elon- gation of the mesethmoid is much less pronounced in that species (Hilton et al., 2007: fig. 10) than in Sternarchorhynchus. We also did not encounter dra- matically elongated mesethmoids amongst outgroup apteronotids in this study (state ...

Context 82

... a lateral ethmoid as a synapomorphy for Platyurosternarchus plus Sternarchorhynchus was a consequence of optimization resulting from the lack of an ossified lateral ethmoid in the examined specimens of Orthosternarchus tamandua. An ossified lateral ethmoid was, however, reported as present in Orthosternarchus tamandua by Hilton et al. (2007: 6, fig. 10), albeit reduced in size and shifted anteriorly relative to the typical condition in apteronotids. A lateral ethmoid is similarly present in the cleared and stained material of Orthosternarchus tamandua examined herein. In light of the consequent recoding of the condition in Orthosternarchus from lateral ethmoid absent to present, the ...

Context 83

... orbitosphenoid extends ventrally from the frontal to contact the dorsal margin of the parasphe- noid in gymnotiforms and many other ostariophysans. In the case of Orthosternarchus tamandua (Hilton et al., 2007: fig. 10b), the species of Platyurosternar- chus crypticus, and Sternarchorhamphus muelleri the ventral portion of the orbitosphenoid proximate to the parasphenoid is anteroposteriorly elongate with a definite anterior extension along the dorsal surface of the latter bone. This condition (state 0) occurs in the examined outgroup species of ...

Context 84

... outgroups to Sternarchorhynchus and all species of that genus other than S. axelrodi and S. mormyrus have a continuous vertical cartilaginous joint between the orbitosphenoid and pterosphenoid [state 0; Fig. 20A; see also Hilton et al. (2007: fig. 10b), for illustration of ventral portion of joint]. Cleared and stained and radiographed individuals of S. mormyrus instead have a distinctly anteriorly concave posterior margin of that portion of the orbito- sphenoid. Contact between the orbitosphenoid and the pterosphenoid is thus limited to separate areas of articulation situated ...

Context 85

... component of the fontanel system is proportionally elongate with the anterior limit of the aperture being situated anterior of the orbitosphenoid. This condition (state 0) is also present in the outgroups Apteronotus and 'Apteronotus' along with Sternarchella orthos and Sternarchogiton labia- tus. Orthosternarchus tamandua (Hilton et al., 2007: fig. 10a) and Sternarchorhynchus species have less extensive frontal fontanels that fall distinctly short of the anterior limit of the orbitosphenoid (state ...

Context 86

... mesocoracoid is a relatively small, vertically elongate ossification running between the cleithrum dorsally and the region of the joint between the cora- coid and scapula ventrally. The possession of a meso- coracoid is typical for gymnotiforms [e.g. species of Gymnotus (Albert & Miller, 1995: fig. 5; fig. 16)] and this ossification is present in Orthosternarchus tamandua (Hilton et al., 2007: fig. 18b) and Sternarchorhamphus muelleri. A meso- coracoid is absent in Platyurosternarchus and Sterna- rchorhynchus and amongst the outgroups of immediate interest also in the species of Apteronotus and 'Apteronotus' along with Sternarchella orthos ...

Context 87

... ossification running between the cleithrum dorsally and the region of the joint between the cora- coid and scapula ventrally. The possession of a meso- coracoid is typical for gymnotiforms [e.g. species of Gymnotus (Albert & Miller, 1995: fig. 5; fig. 16)] and this ossification is present in Orthosternarchus tamandua (Hilton et al., 2007: fig. 18b) and Sternarchorhamphus muelleri. A meso- coracoid is absent in Platyurosternarchus and Sterna- rchorhynchus and amongst the outgroups of immediate interest also in the species of Apteronotus and 'Apteronotus' along with Sternarchella orthos and Sternarchogiton labiatus (state ...

Context 88

... coracoid extends anteriorly as an elongate, typically anteriorly attenuating splint of bone amongst gymnotiforms. This condition similarly occurs in outgroups to Sternarchorhynchus examined in this study (Hilton et al., 2007: fig. 18 for condition in Orthosternarchus tamandua). Anteriorly, this portion of the bone lies proximate to the medial surface of the cleithrum and is capped by at most a small cartilage body. This morphology of the coracoid process (state 0) also characterizes all Sternarcho- rhynchus species other than S. britskii and S. caboclo. In these ...

Context 89

... has a single large, plate-like postcleithrum partially over- lapped by the pectoral girdle (Hilton et al., 2007: fig. 18). This element and the ossifications in the species of Platyurosternarchus along with Sternar- chorhamphus muelleri are positionally equivalent to the first postcleithrum in the Characiformes [e.g. Brycon meeki (Weitzman, 1962: fig. 18)] including the basal families Distichodontidae and Citharinidae (Vari, 1979: fig. 35). Ossifications located in this posi- tion in Orthosternarchus and Sternarchorhamphus are homologous with the first postcleithrum of other orders of the Ostariophysi. A comparable first postcleithrum is also present in Sternarchorhynchus, with the ...

Context 90

... the purposes of the following discussion, we utilize a positional concept for postcleithra. The element partially overlapped by the posterior portion of the cleithrum is herein coded as the first postclei- thrum in keeping with its positional equivalence to the ossification of that name in other ostariophysans [e.g. Brycon meeki (Weitzman, 1962: fig. 18)]. Sequen- tially posterior elements in that series are termed the second and third postcleithra. In light of this conven- tion, the ossification(s) situated anterodorsal to the first postcleithrum in Adontosternarchus, Gymnotus, and some species of Sternarchorhynchus coded under character 75 are elements of uncertain ...

Context 91

... independent ossification situated posterior of the cleithrum and anterodorsal to the first postclei- thrum occurs in S. axelrodi, S. britskii, S. chaoi, S. curvirostris, S. gnomus, S. goeldii, S. hagedornae, S. inpai, S. montanus, S. mormyrus, S. oxyrhynchus, S. severii, and S. starksi (state 1; Fig. 21). Amongst the outgroup apteronotids examined in this study, this ossification is present in 'A.' apurensis. No ossification occurs in this region (state 0) in the remaining Ster- narchorhynchus species or in A. albifrons, A. rostra- tus, Orthosternarchus tamandua, P. crypticus, P. macrostoma, Sternarchella orthos, Sternarchogiton ...

Context 92

... located anterodorsal to first postcleithrum: (0) rounded or ovoid; (1) elongate (CI = 0.250; RI = 0.400). When present, the independent ossification reported under character 75 has either of two forms in Sternarchorhynchus and other examined apter- onotids. A rounded, ovoid, or slightly irregularly rect- angular form of the bone (state 0; Fig. 21A) occurs in S. chaoi, S. gnomus, S. hagedornae, S. inpai, S. montanus, S. severii, and S. starksi and in the out- group in 'A.' apurensis. In contrast, an anterodorsally distinctly elongate form of the ossification (state 1; Fig. 21B) is present in S. axelrodi, S. britskii, S. curvirostris, S. goeldii, S. mormyrus, and S. oxyrhyn- chus. ...

Context 93

... other examined apter- onotids. A rounded, ovoid, or slightly irregularly rect- angular form of the bone (state 0; Fig. 21A) occurs in S. chaoi, S. gnomus, S. hagedornae, S. inpai, S. montanus, S. severii, and S. starksi and in the out- group in 'A.' apurensis. In contrast, an anterodorsally distinctly elongate form of the ossification (state 1; Fig. 21B) is present in S. axelrodi, S. britskii, S. curvirostris, S. goeldii, S. mormyrus, and S. oxyrhyn- chus. This ossification is absent and could not be coded in the remaining Sternarchorhynchus species examined osteologically along with A. albifrons, A. rostratus, Orthosternarchus tamandua, P. crypticus, P. macrostoma, Sternarchella ...

Context 94

... single postcleithrum (state 0), the first postclei- thrum under the numbering system discussed above, is the only element of that series present in Orthosternarchus tamandua (Hilton et al., 2007: fig. 18) and Sternarchorhamphus muelleri. A second postcleithrum located posterior to the first postclei- thrum is present in Platyurosternarchus and Ster- narchorhynchus for a total of at least two postcleithra in these genera [states 1 (Fig. 20A, B) and 2]. Outgroups with a second postcleithra are A. cuchillo, 'A.' apurensis, and ...

Context 95

... overlapped, in turn, by the posterior margin of the cleithrum. Two morphologies of the second postcleithrum occur within Platyuro- sternarchus, Sternarchorhynchus, and the other examined apteronotids bearing that ossification. In P. crypticus, P. macrostoma, S. goeldii, S. mormyrus, and S. oxyrhynchus the bone is horizontally elongate (state 1; Fig. 21B), whereas in all other species of Sternarchorhynchus the ossification is either round or only slightly longitudinally ovoid (state 0; Fig. 21A). An elongate morphology of the second postcleithrum (state 1) also occurs in A. cuchillo and 'A.' apurensis. This character could not be coded for outgroups that lack a second postclei- thrum ...

Context 96

... Sternarchorhynchus, and the other examined apteronotids bearing that ossification. In P. crypticus, P. macrostoma, S. goeldii, S. mormyrus, and S. oxyrhynchus the bone is horizontally elongate (state 1; Fig. 21B), whereas in all other species of Sternarchorhynchus the ossification is either round or only slightly longitudinally ovoid (state 0; Fig. 21A). An elongate morphology of the second postcleithrum (state 1) also occurs in A. cuchillo and 'A.' apurensis. This character could not be coded for outgroups that lack a second postclei- thrum or for S. axelrodi based on radiographs of the ...

Context 97

... ossified hypural plate is common to both Ster- narchorhynchus and Platyurosternarchus, whereas the plate is cartilaginous in Orthosternarchus tamandua (Hilton et al., 2007: fig. 17a) and Sternar- chorhamphus muelleri [state 1; note: the specimen illustrated by Fink & Fink (1981) as Sternarchorham- phus with an ossified hypural plate is rather P. cryp- ticus]. The plate is also ossified in other examined outgroup apteronotids, although with some specimens of A. rostratus having only a slightly developed ossi- ...

Context 98

... the Apteronotidae, the very different forms of the elongation of the anterior region of the head in Compsaraia and Apteronotus relative to the snout morphology in Sternarchorhynchus brings to the fore questions as to the equivalence of the preor- bital expansion in these taxa (Cox-Fernandes et al., 2002: fig. 1;and Hilton & Cox Fernandes, 2006: fig. 1, relative to the species of Apteronotus;and Mago-Leccia, 1994: fig. 90, for Compsaraia compsus identified as Porotergus compsus therein). More sig- nificantly, neither Compsaraia nor the species of Apteronotus with elongate preorbital regions are closely related to Sternarchorhynchus (Albert, 2001;Crampton & Albert, 2006; results of ...

Context 99

... discussed above, grasp-suction or suction assisted by mechanical grasping is unique to two genera amongst freshwater fishes; Sternarchorhyn- chus in the Neotropics and Campylomormyrus, a member of the order Mormyriformes that inhabits rivers in the western and central portions of sub- Saharan Africa (Feulner et al., 2007: fig. 1). Notwith- standing the striking convergence between these two genera in their feeding systems, numerous differences occur in the underlying osteological systems in Ster- narchorhynchus versus Campylomormyrus. Given the pronounced phylogenetic distance between these genera, this result is expected and in the interests of efficiency, we ...

Context 100

... of Sternarchorhynchus render its speciose nature all the more impressive in terms of proportional density of species. In part this density is made possible by the ability by many species of Sternarchorhynchus to exploit deep river habitats, which contrasts with the absence of all genera of the Gymnotidae from such habitats (Crampton, 2007: 302 fig. 1) demonstrate particularly striking sexual dimorphic remodelling of the lower jaw of various forms. Some males with well-developed testes amongst the Ster- narchorhynchus species in clade 17 have the dentary anteriorly lengthened and transversely expanded into a dorsally bulbous structure that is rounded from a dorsal view ( Fig. 25A; ...

Context 101

... anal-fin rays 166-178 [173] (N = 13). Scales above lateral line at midbody 11-13 [13] (N = 13). Scales present along mid-dorsal line in region anterior to origin of midsaggital electroreceptive filament. ...

Context 102

... dark overall with stripe of darker pigmentation extending anteriorly from orbit for distance one-half to two-thirds length of snout. Dorsal region of dark pigmentation on head forms lateral margin of narrow, Figure 31. Sternarchorhynchus chaoi sp. ...

Context 103

... fin origin located slightly posterior of vertical through anterior margin of opercle. Anterior unbranched anal- fin rays 17-29 [24] (N = 15). Total anal-fin rays 180- 221 [221] (N = 24); number of rays apparently increases ontogenetically given evident correlation between greater body size and increased numbers of anal-fin rays amongst examined specimens. ...

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... collected by W. G. R. Crampton, 19.ii.2001;MCP 41638, 1 (331) (3°27′22″S, 60°45′21″W); collected by Angela Zanata et al., 1.viii.1996;FMNH 115490, 7 (133-315 Diagnosis: Sternarchorhynchus curumim is distin- guished from congeners by the following combina- tion of characters: a short gape that terminates posteriorly at, or slightly short of, the vertical through anterior nares, the presence of a definite series of scales along the mid-dorsal region of the body, the absence of a more lightly coloured narrow band of mid-dorsal pigmentation on the head and mid-dorsal region of the body anterior of the origin of the electroreceptive filament, the lateral line that extends to the base of the caudal fin, the dusky anal fin without a distinct dark band along its distal margin, the possession of seven to ten teeth on the premaxillary, seven to eight teeth in the outer row of the dentary, 15 precaudal vertebrae, 23-24 ante- rior unbranched anal-fin rays, 179-189 total anal-fin rays, ten to 11 scales above the lateral line at the midbody, 13-15 caudal-fin rays, the greatest body depth (9.0-10.0% of LEA), the distance from the anus to the anal-fin insertion (8.3-13.5% of HL), the preanal distance (12.4-14.4% of LEA), the caudal length (10.9-12.2% of LEA), the head length (18.7- 20.6% of LEA), the snout length (60.2-62.5% of HL), the mouth length (3.5-5.6% of HL), the eye diam- eter (4.1-5.0% of HL), the internarial distance (2.4- 2.8% of HL), the postocular distance (33.6-39.2% of HL), the pectoral-fin length (34.5-37.8% of HL), the tail depth (10.6-11.9% of caudal length), and the caudal length (10.9-12.2% of LEA). ...

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... form of dentary or dentary dentition apparent in examined samples. Dentary with two rows of teeth. Outer row consisting of 13-20 curved conical teeth and inner row with three to five teeth (N = 7). Mouth terminal. Gape of mouth aligned with main axis of snout, elongate and extending pos- teriorly distinctly beyond vertical through posterior naris (Fig. 1A). Lower jaw with terminal fleshy pad that extends anteriorly beyond vertical through ante- rior limit of snout. Fleshy pad directed dorsally and overlaps tip of snout when mouth ...

Context 106

... rays ii + 11-13 [ii + 13] (N = 14). Anal- fin origin located slightly posterior of vertical through anterior margin of opercle. ...

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... fin origin located slightly posterior of vertical through anterior margin of opercle. Anterior unbranched anal- fin rays 23-31 [28] (N = 14). Total anal-fin rays 162- 178 [171] (N = 15). ...

Context 108

... with dorsomedial fleshy ridge on anterior half of snout; ridge absent in female. Ridge makes that portion of snout of male overall distinctly deeper than in female (compare Figs 51, 52). Mouth moderate, with opening anterodorsally orientated, and rictus located at, or slightly posterior of, vertical through anterior naris. ...

Context 109

... ontogenetic variation or seasonality in the expression of that modification. The male also has a well-developed, mid-dorsal fleshy ridge along the anterior half of the snout that is lacking in the female (compare Figs 51, 52). This feature is unique to this species within Sternarchorhynchus. ...

Context 110

... broad ranges occur in some fish species that have been critically analysed across those basins within the Apteronotidae (e.g. Sternarchorhamphus muelleri, Campos-da-Paz, 1995: fig. 2) and other major groups in those ichthyofaunas (e.g. Siluriformes: Hoplosternum littorale, Reis, 1997: fig. 4; Cetopsis coecutiens, Vari, Ferraris & de Pinna, 2005: fig. 19. Cichlidae: Cichla ocellaris, Cichla temensis, Kullander & Ferreira, 2007: figs 9, 75. Characidae: Roeboides affinis, de Lucena, 2007 fig. ...

Context 111

... teeth in region situated short distance posterior of symphysis shifted somewhat laterally and pointed slightly dorsolaterally. Outer tooth row with six associated replacement teeth in that specimen. Mouth terminal. Gape of mouth aligned with main axis of snout, elongate and extending posteriorly distinctly beyond vertical through posterior naris (Fig. 1A). Lower jaw with terminal fleshy pad that extends beyond vertical through anterior limit of snout. Pad orientated dorsally and overlaps tip of snout in closed ...

Context 112

... Orinoco, near mouth of Río Caura (7°38′N, 64°52′W); ANSP 163044, 1 (283). Delta Amacuro: Río Orinoco, shallow river, north side of river across from Isla Tres Caños, 131.8 nautical miles (= 243.8 km) from sea buoy (8°39′48″N, 62°01′W); USNM 228787, 8 (1 CS, 207314). Río Orinoco, deep river channel, at Isla Tres Caño, 130 nautical miles (= 240.5 km) upstream from sea buoy (8°40′N, 61°59′W); USNM 228788, 1 (348); MBUCV 10886, 2 (227-297). ...

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... Amacuro: Río Orinoco, shallow river, north side of river across from Isla Tres Caños, 131.8 nautical miles (= 243.8 km) from sea buoy (8°39′48″N, 62°01′W); USNM 228787, 8 (1 CS, 207314). Río Orinoco, deep river channel, at Isla Tres Caño, 130 nautical miles (= 240.5 km) upstream from sea buoy (8°40′N, 61°59′W); USNM 228788, 1 (348); MBUCV 10886, 2 (227-297). Río Orinoco, north shore, in front of Isla Tres Caños (approximately 8°39′48″N, 62°01′W); MBUCV 11853, 1 (305); MBUCV 10691, 1 (250). ...

Context 114

... 63-65; TABLE 11) Sternarchorhynchus cf. roseni -Crampton, 2007: 320, fig. 11.13c [sexual dimorphism in form of anterior portion of ...

Context 115

... fin origin located slightly posterior of vertical through anterior margin of opercle. Anterior unbranched anal-fin rays 17-27 [27] (N = 12). Total anal-fin rays 198-225 [225] (N = 14); number of rays apparently increases ontogenetically based on correlation between increased body length and greater numbers of rays in examined samples. ...

Context 116

... unbranched anal-fin rays 17-27 [27] (N = 12). Total anal-fin rays 198-225 [225] (N = 14); number of rays apparently increases ontogenetically based on correlation between increased body length and greater numbers of rays in examined samples. Scales above lateral line at midbody ten to 11 [10] (N = 20). ...

Context 117

... sexual dimorphism in the form of the dentary and in the position of the anus and urogenital opening. At least some males have the dentary extended further ante- riorly and widened transversely into a dorsally bulbous structure that is distinctly rounded from dorsal view and bears a series of enlarged, posteriorly recurved teeth (Crampton, 2007: fig. 11.13c; species identified therein as S. cf. roseni). Juveniles and adults without these elaborations instead have the anus and urogenital opening positioned approxi- mately along the vertical through the eye. Males as evidenced by the presence of a well-developed patch of teeth on the anterior portion of the dentary have these structures ...

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... compressed and of moderate length, ending in small and elongate caudal fin. Caudal-fin rays 12-16 [16] (N = 14). ...

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... rays ii + 12-13 [ii + 12] (N = 13). Anal- fin origin located anterior to vertical through margin of opercle. ...

Context 120

... anal-fin rays 161-175 [164] (N = 12). Scales above lateral line at midbody seven to 12 [9] (N = 13). Scales clearly present along mid-dorsal line of body to origin of midsaggital electroreceptive filament. ...