Paravandellia, MirandaRibeiro, 1912

Pinna, Mário de & Dagosta, Fernando Cesar Paiva, 2022, A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus, Papéis Avulsos de Zoologia 62, pp. 1-90 : 78-80

Monophyly of Paravandellia

The nomenclatural history of Paravandellia MirandaRibeiro, 1912 is surprisingly complex, considering the relative simplicity of the biological situation. No less than three genera have been erected to acommodate species now in Paravandellia : Branchioica Eigenmann, 1917 , Parabranchioica Devicenzi & Vaz-Ferreira, 1939 , and Pleurophysus Miranda-Ribeiro, 1918 all, based on species from the Paraná-Paraguay-Uruguay drainage complex. Synonymy of Branchioica under Paravandellia was suggested by Eigenmann (1918: 269 and Miles, 1943: 367) and subsequently implemented by Miranda-Ribeiro (1947), who added Parabranchioica as an additional synonym. The enigmatic Pleurophysus was identified as still another synonym of Paravandellia by Miranda-Ribeiro (1956: 3), a move later corroborated (de Pinna & Woiacki, 2003).

Morphological diversity in Paravandellia is relatively limited, despite a geographical distribution that is even broader than that of Paracanthopoma . There are probably a number of different taxa in the Paravandellia , but their differentiation is far more subtle than that among species of Paracanthopoma . As expected given their relative morphological uniformity, Paravandellia is an easily-recognizable monophyletic group. Below is a list of synapomorphies for the genus identified herein or in previous works, including the most detailed work by DoNascimiento (2012). One of the characters proposed as synapomorphic for Paravandellia by DoNascimiento (2012) was the insertion of the ligament between the hyomandibula and the neurocranium on the sphenotic only. In other trichomycterids the ligament inserts either on the pterotic or on the pterotic and sphenotic. While confirmed in Paravandellia species examined here, the condition of available material of Paracanthopoma did not allow reliable observation of the ligament in all species. The condition of this character in the genus, and thus its phylogenetic distribution, must await more complete data.

10 Maxilla greatly expanded, plate-like: The maxilla in species of Paravandellia is markedly expanded, resembling a roundish plate covering the lateral side of the distal portion of the premaxilla ( Fig. 46 ).This state contrasts with the normal condition in other vandelliines and remaining trichomycterids where the maxilla, despite several other variations of shape, has a longer and less expanded configuration. Among vandelliines, the only similar condition is seen in Pl. diabolicus , an occurrence hypothesized as convergent because of the phylogenetic distance between the two taxa ( DoNascimiento, 2012; Pl. diabolicus is closer to a number of closely-related yet undescribed forms and Vandellia , than to Paravandellia ; the latter,in turn, is closer to Paracanthopoma ).

DoNascimiento (2012: 120, character 181) reports on the absent maxilla in two unidentified (probably undescribed) taxa of Paravandellia , one from the Caquetá and the other from the Orinoco, proposing this loss as a synapomorphy for cis-Andean Paravandellia . Material examined for this paper includes species from the Paraná-Paraguay and Amazon, all of which have maxillas with the expected morphology described above. From the Orinoco basin, of seven c&s specimens examined of Paravandellia sp. (FMNH 110042), two have visible maxillas, one of which well-calcified and the other uncalcified. The bone is difficult to visualize but in the expected position flush with the dorsolateral surface of the distal portion of the premaxilla. There is clearly a trend for reduction of the maxilla in the Paravandellia form(s) from the Orinoco, which seems to reach total absence in some specimens. Still, the shape of the maxilla in those specimens where it is present corresponds to the shape typical for the genus.

11 Anterior margin of mesethmoid with small median notch, bordered by bilateral prominences: The anterior margin of median portion of the mesethmoid in the majority of vandelliines and other trichomycterids is continuous, lacking pronounced relief features. In Paravandellia , the mesethmoid in dorsal view has a small median concavity, or notch ( Fig. 46B ). Laterally to the notch on each side are small prominences. This set of modifications is unique to Paravandellia . Ochmacanthus has a broad median concavity on the mesethmoid where the ascending process of the median premaxilla articulates. That concavity is a major structural feature of the mesethmoid in that genus, and not simply a disruption of the otherwise straight anterior profile. It also lacks bilateral prominences. Such anatomical differences plus the phylogenetic distance between Ochmacanthus and Paravandellia ( DoNascimiento, 2012) indicate that the two states are homoplastic.

12 Coronoid process of lower jaw formed exclusively by anguloarticular: In Paravandellia , the coronoid process is formed exclusively by the anguloarticular,a condition exclusive to the genus among vandelliines. The process is most prominent in Pv. phaneronema . In all cases, however, the process retains a cartilage lining. Other cases of a coronoid process composed only of the anguloarticular are seen in the stegophilines Megalocentor and Pareiodon , and in Tridentinae (including Potamoglanis ) ( DoNascimiento, 2012: 99, character 121). In all of the latter, the coronoid process is not well differentiated from the rest of the lower jaw,but instead continuous in a long slope with the toothed portion of the dentary, a situation is structurally different from that in Paravandellia . As seen above (character 2), a derived condition opposite to that in Paravandellia is seen in Paracanthopoma , where the coronoid process is formed mostly or totally by the the dentary. In vandelliines other than Paracanthopoma and Paravandellia , the process includes both anguloarticular and dentary components, as is the widespread condition in other siluriforms.

13 Ventral strut of orbitosphenoid (forming ventral part of optic foramen) very narrow, curved or slanted laterally in dorsal view: The orbitosphenoid has much variation which is still uncharted in trichomycterids. Normally in the family, the bone is trespassed by the optic foramen, which leaves a wide bony area ventrally to it. In species of Paravandellia , the portion of the orbitosphenoid ventral to the optic foramen is narrow, in the form of a bony strut slightly directed or curved laterally ( Fig. 46B, C ). The condition is most pronounced in Pv.oxyptera where the strut is very narrow, forming just a thin frame for the ventral part of the optic foramen. DoNascimiento (2012: 69, character 47) partly expressed this character as the relative size of the optic foramen, but with a different circumscription that applies also to Vandellia . As described here, the condition is exclusive to Paravandellia .

14 Ventral arm of orbitosphenoid distantly connected by long stretch of cartilage to corresponding anterior arm of compound sphenotic-prootic-pterosphenoid: The posteroventral portion of the orbitosphenoid in species of Paravandellia contacts the corresponding anteroventral arm of the sphenotic-prootic-pterosphenoid by a long cartilage. The bony portions of the two bones are distant from each other ( Fig. 46B, C ). The plesiomorphic condition, seen in most other trichomycterids, including all other vandelliines, is to have the bony parts of the two arms closely positioned, with only a narrow intervening cartilage. As in the preceding character, here the condition in Pv.oxyptera is more extreme than in Pv. phaneronema . A similar delimitation of this character, assignable to Paravandellia and Trichogenes , was proposed by DoNascimiento (2012: 71, character 52). As defined here, it is exclusive to the latter.

15 Ascending process of opercle as a simple diverging rod: The ascending (or dorsal) process of the opercle in trichomycterids is the main site of insertion of the dilatator and levator muscles ( Datovo & Bockmann, 2010). In all species of Paravandellia , the ascending process of the opercle is a simple diverging rod, abruptly emerging from the dorsal surface of the opercle ( Fig. 46A, B ). This condition contrasts with that seen in all other vandelliines and other trichomycterids where the anterior margin of the ascending process has an oblique flange connecting it to the opercle (e.g., Fig. 26A ). The unique condition in Paravandellia is apparently caused by a loss of the bony flange seen in other taxa. The condition of this character is not comparable in taxa either lacking the ascending process of the opercle ( Pc. saci , among vandelliines).

16 Lateral surface of opercle adjacent to articulation with hyomandibula expanded to form a partial shield between the margin of the opercle and the posterior margin of the hyomandibula: Usually in trichomycterids and a majority of other siluriforms, the articulation between the opercle and the hyomandibula is exposed laterally. In Paravandellia , the opercle has a small shield-like expansion laterally protecting its articulation with the hyomandibula ( Fig. 46B ). The shape of the expansion differs among taxa, being anteriorly round in Pv. phaneronema and pointed in Pv.oxyptera A similar structure is seen,supposedly convergently due to phylogenetic distance among relevant taxa (cf., DoNascimiento, 2012), in species of Potamoglanis .

17 Head of urohyal with anterior processes widely spaced: The anterior arms of the urohyal in trichomycterids and other siluriforms are usually closely positioned, or maximally separated by a space equivalent to the length of one individual arm. This is also the condition most vandelliines. Exceptionally, species of Paravandellia have very broad structure of the anterior portion of the urohyal, so that the anterior arms are widely separated by a large space, equivalent to at least three times the length of one arm ( Fig. 46C ). This set of modifications results in a urohyal which is very typically identifiable as belonging to the genus, with no parallels among trichomycterids and clearly synapomorphic. The anterior head of the urohyal is hypertrophied relative to the rest of the bone in Pl.diabolicus , but the relative distance between the arms is not different from the plesiomorphic condition. This character is not comparable in taxa where the urohyal horns are vestigial ( Pc. malevola and Pc. satanica ) or absent ( Pc.daemon , Pc.irritans , and Pc.saci ), but in all such cases the narrow structure of the anterior portion of the urohyal is not physically compatible with widely spaced out processes. So, they cast little doubt on the condition as synapomorphic for Paravandellia .

18 Fourth ceratobranchial ossification vestigial or absent: All vandelliines lack the fifth ceratobranchial, a synapomorphy for the subfamily with rare parallel occurrences among teleosts ( Baskin 1973; de Pinna, 1998). Uniquely, species of Paravandellia lack also the fourth ceratobranchial. In some case (as in some specimens of Pv.oxyptera ), the fourth ceratobranchial ossification is very reduced but still present as a small bony nodule (sometimes with a remnant proximal cartilage plug) adjacent to the lower portion of the row of gill filaments of the fourth arch. This vestigial condition is often bilaterally asymmetrical, with one of the sides sometimes reduced to a tiny ossified nodule. Despite the reduction or absence of the fourth ceratobranchial ossification, the fourth epibranchial and the respective row of gill filaments and associated soft structures of the fourth branchial arch are still present. This character was offered as a synapomorphy for Paracanthopoma plus Paravandellia by DoNascimiento (2012). However, the fourth ceratobranchial is present in all specimens examined of Paracanthopoma and therefore its absence is herein considered as diagnostic for Paravandellia only. DoNascimiento (pers. comm.) informs that his observations were confirmed in five specimens of Pc. irritans from the Orinoco (a population that may actually represent a distinct species from Pc. irritans ; see Remarks on Pc. irritans ). In that case, the loss of the fourth ceratobranchial in that lineage is probably homoplastic with that in Paravandellia .

Figures

Figure 26. Paracanthopoma malevola, holotype,INPA 59836, CTscan images of head skeleton,(A) Lateral;(B) Dorsal;(C) Ventral.

Figure 46. Paravandelliaphaneronema, MCZ 35874,CT scan images of head and anterior portion of body,(A) Lateral;(B) Dorsal;(C) Ventral.