Cetopsorhamdia, Bockmann & Reis, 2021
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publication ID |
https://doi.org/ 10.11606/1807-0205/2021.61.56 |
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publication LSID |
lsid:zoobank.org:pub:C5CF39C6-4841-41A7-AACB-A41CC95994B7 |
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persistent identifier |
https://treatment.plazi.org/id/F5338795-FF95-797B-FC14-028BA271F242 |
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treatment provided by |
Felipe |
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scientific name |
Cetopsorhamdia |
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Monophyly of Cetopsorhamdia View in CoL View at ENA
The genus Cetopsorhamdia is morphologically diagnosed by four synapomorphies ( Bockmann, 1998: clade 118): (1) presence of a medial ossification over the median portion of the skull, covering the epiphyseal bar and leaving reduced anterior and posterior fontanels; (2) orbital (= optic) foramen small; (3) mouth ventral; and (4) snout conical. The first character is notably present in both Cetopsorhamdia clathrata ( Fig. 6B View Figure 6 ) and C. spilopleura ( Fig. 16B View Figure 16 ). Plesiomorphically, the cranium of most catfishes has a dorsal fontanel divided into two by a narrow epiphyseal bridge. The anterior fontanel is delimited anteriorly by the mesethmoid and posterolaterally by the frontals, while the posterior fontanel is framed anteriorly and laterally by the frontals and posterolaterally by the supraoccipital. Among heptapterids, this generalized configuration has been illustrated for species of Gladioglanis Ferraris-Jr. & Mago-Leccia, 1989 (cf. Ferraris-Jr. & Mago-Leccia,1989: fig. 5; Lundberg et al., 1991: fig. 1), Mastiglanis Bockmann, 1994 ( Bockmann, 1994: fig. 4), Pimelodella Eigenmann & Eigenmann, 1888 ( Bockmann & Miquelarena, 2008: fig. 21; Slobodian & Pastana, 2018: fig. 3), Rhamdella Eigenmann & Eigenmann, 1888 ( Miquelarena & Menni, 1999: fig. 7; Bockmann & Miquelarena, 2008: fig. 7), and Rhamdiopsis Haseman, 1911 ( Bockmann & Castro, 2010: fig. 4A). We have found that all species of Cetopsorhamdia share the frontals with superficial outgrowths along their inner margins so as to obliterate the epiphyseal bar, the posterior half of anterior fontanel, and the anterior half of posterior fontanel. This condition has been noticed by Eigenmann (1916, 1922) for C. nasus , described as “a small frontal fontanel, far removed from the long parietal fontanel”, and by Eigenmann (1922) for C. boquillae , described as “frontal fontanel and occipital fontanel […] shorter than the roofed space between them”. Although we have not examined in detail the skeleton of C. nasus (only a radiograph of the holotype was available), the type species of the genus, that feature was illustrated for this species by Ortega-Lara (2012: fig. 6). Ruiz-C. & Román-Valencia (2006: fig. 4a) illustrated this condition for C. boquillae , but they were unaware about the presence of the epiphyseal bar, ignoring that it was indeed covered by the superficial ossifications along the medial margins of frontals. These authors also described and illustrated the anterior fontanel of a heptapterid identified as C. nasus as being wide and bifurcated (Ruiz-C. & Román-Valencia, 2006: fig. 4b). It is not clear what the authors mean by bifurcated, but their observation of a broad fontanel is probably owed to their inability in determining the correct limits of anterior fontanel in a poorly-calcified cleared and stained specimen (cf. Ruiz-C. & Román-Valencia, 2006: 129, fig. 4b). The weak calcification of that specimen is also indicated by the broadly cartilaginous composition of the anterior portion of the palatine, which was mistakenly recognized as a diagnostic characteristic for C.nasus by Ruiz-C.& Román-Valencia (2006). On the other hand, the limits of the posterior fontanel are well defined, and its shape represens the plesiomorphic configuration.This character,in addition to the presence of relatively large eyes, long maxillary barbel, fins with convex distal profile, long adipose-fin base, dorsal caudal-fin lobe longer than the ventral lobe, and total number of vertebrae indicate that the correct identification of C. nasus by Ruiz-C. & Román-Valencia (2006: fig. 2) is Imparfinis usmai Ortega-Lara, Milani, DoNascimiento, Villa-Navarro & Maldonado-Ocampo (cf. Ortega-Lara et al., 2011). Among heptapterids, a state like that exhibited by Cetopsorhamdia is also present in Taunayia Miranda-Ribeiro, 1918 , a condition thought to be homoplastic, considering that these genera are distantly related to each other (cf. Bockmann, 1998; Silva et al., 2021). In members of Brachyglanis Eigenmann, 1912 , Brachyrhamdia Myers, 1927 , Leptorhamdia Eigenmann, 1918 , and Myoglanis Eigenmann, 1912 , and in Rhamdella aymarae Miquelarena & Menni, 1999 , Rhamdia enfurnada Bichuette & Trajano, 2005 , Rhamdia guasarensis DoNascimiento, Provenzano & Lundberg, 2004 , and Rhamdia quelen (Quoy & Gaimard, 1824) , the posterior cranial fontanel is totally or partially closed (cf. Lundberg & McDade, 1986; Bockmann, 1998; Silfvergrip, 1996; Miquelarena & Menni, 1999; DoNascimiento et al., 2004; Bichuette & Trajano, 2005; Slobodian & Bockmann, 2013) but due to a non-homologous configuration. In those taxa the closure of the posterior fontanel is produced by the approximation of the internal borders of the posteri- or portion of the frontals and the anterior portion of the supraoccipital, at the region corresponding to the midportion of posterior fontanel.
Regarding the second character, the foramen for the optic nerve in C. clathrata ( Figs. 6A, C View Figure 6 ) and C. spilopleura ( Figs. 16A, C View Figure 16 ) is undoubtedly smaller than in those of most heptapterids (cf. Bockmann, 1998; Bockmann & Miquelarena, 2008), having approximately half the length of the trigeminofacial foramen. A further reduction in the foramen for the optic nerve to ¼ or less the length of the trigeminofacial foramen is observed in C. boquillae , C.iheringi , C.insidiosa , and C.picklei . Ortega-Lara (2012) did not describe or illustrate the foramen for the optic nerve in C. nasus , so that its state for this trait cannot be accessed.
The third and fourth synapomorphies proposed for Cetopsorhamdia by Bockmann (1998), i.e., the ventral mouth and conical snout, are not derived characters for the genus. Instead, they are likely synapomophies for a more restricted group of species within the genus (see below). A ventral mouth, with its anterior border forming a wide arch, sometimes being almost straight in ventral view,is clearly present in C.iheringi (cf. Schubart & Gomes, 1959: fig. 1), C. insidiosa (cf. Steindachner, 1915: pl. 12, fig. 7), C. nasus (cf. Eigenmann, 1922: pl. 4, fig. 1; Ortega- Lara, 2012: figs. 1-2, 4, 19), and C. picklei (cf. Schultz, 1944: p. 2, fig. D). In both C. clathrata ( Figs. 1-3 View Figure 1 View Figure 2 View Figure 3 , 5A View Figure 5 ) and C. spilopleura ( Figs. 12-14 View Figure 12 View Figure 13 View Figure 14 , 15A View Figure 15 ), the mouth also has a ventral position, but not at the extent of the species above mentioned, nor does it have an almost straight edge. The mouth of C. boquillae , on the other hand, has the widespread heptapterid configuration, being subterminal and bearing a contour markedly arched (cf. Eigenmann, 1922: pl. 1, fig. 3; Ruiz-C. & Román-Valencia, 2006: fig. 1). Likewise, the snouts of C. iheringi (cf. Schubart & Gomes, 1959: fig. 1), C. insidiosa (cf. Steindachner, 1915: pl. 12, fig. 7), C. nasus (cf. Eigenmann, 1922: pl. 4, fig. 1; Ortega- Lara, 2012: figs. 1-2, 4, 19), and C. picklei (cf. Schultz, 1944: pl. 2, fig. D) are distinctly conical, almost triangular, when viewed dorsally. The snout of C. clathrata ( Figs. 1 View Figure 1 , 4 View Figure 4 , 5B View Figure 5 ) and C. spilopleura ( Figs. 12 View Figure 12 , 14 View Figure 14 , 15B View Figure 15 ), although also conical, is much more attenuated, bearing ellipsoid contour in dorsal view. Cetopsorhamdia boquillae , in turn, exhibits a snout with an anterior contour characteristically round- ed in dorsal view, which is the typical plesiomorphic morphology among heptapterids (cf. Bockmann, 1998). These last two characters should, therefore, be excluded from the list of Cetopsorhamdia synapomorphies.
On the other hand, our study allowed us to hypothesize other two putative synapomorphies for the genus Cetopsorhamdia . One of them, the presence of a vertical, dark band at caudal peduncle, on the region of insertion of caudal-fin rays, had already been mentioned by Eigenmann (1916) in the original description of the genus. Eigenmann (1916) described it as “a dark band at base of caudal”, considering it characteristic of C. nasus . This condition was explicitly mentioned and illustrated for C. iheringi , C. insidiosa , and C. picklei in their original descriptions (cf. Steindachner, 1915; Schultz, 1944; Schubart & Gomes, 1959). Although this mark cannot be verified in the types of C. boquillae because they are strongly faded, the examination of a photograph of a live specimen provided by Armando Ortega leaves no doubt about its presence in the species. Ruiz-C. & Román-Valencia (2006) also reported this caudal mark for C. boquillae . Cetopsorhamdia clathrata ( Figs. 1-3 View Figure 1 View Figure 2 View Figure 3 ) and C. spilopleura ( Figs. 12-14 View Figure 12 View Figure 13 View Figure 14 ) exhibit a state different from the remaining species of Cetopsorhamdia , in which the mark is smaller, being mostly restricted to the central portion of the caudal peduncle. In C. boquillae , C. iheringi , C. insidiosa , C. nasus , and C. picklei the caudal mark is larger,W-shaped, distinctly extending towards the dorsal and ventral borders of the caudal peduncle.
In the course of this investigation we identified another character in the hyomandibular bone that also seems to corroborate the monophyly of Cetopsorhamdia . All species of the genus, including C. clathrata ( Fig. 21A View Figure 21 ) and C. spilopleura ( Fig. 22A View Figure 22 ), have an oblique keel ( HK) at the posterodorsal region of the lateral surface of the hyomandibula.In spite of Ortega-Lara (2012) had not described such a structure in the hyomandibula of C.nasus , it is possible to identify it, albeit faintly, in his photograph of a c&s specimen (cf. Ortega-Lara, 2012: fig. 10).
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