From 508b952228e9cbe68f8cf3bf01b7424a8eb5412c Mon Sep 17 00:00:00 2001 From: ggserver Date: Fri, 13 Dec 2024 12:56:34 +0000 Subject: [PATCH] Add updates up until 2024-12-13 12:51:30 --- .../87/039B87BCFFB857072250CF94FDB9F8EC.xml | 3327 +++++++++++++++++ 1 file changed, 3327 insertions(+) create mode 100644 data/03/9B/87/039B87BCFFB857072250CF94FDB9F8EC.xml diff --git a/data/03/9B/87/039B87BCFFB857072250CF94FDB9F8EC.xml b/data/03/9B/87/039B87BCFFB857072250CF94FDB9F8EC.xml new file mode 100644 index 00000000000..a1887f9077b --- /dev/null +++ b/data/03/9B/87/039B87BCFFB857072250CF94FDB9F8EC.xml @@ -0,0 +1,3327 @@ + + + +The neurocranium of Potamotrygonidae: morphology and phylogenetic significance + + + +Author + +Araújo, Marcus V. G. +Laboratório de Ictiologia (LABICT), Departamento de Sistemática e Ecologia, Universidade Federal da Paraíba, João Pessoa, Brazil + + + +Author + +Vaz, Diego F. B. +Natural History Museum, London, United Kingdom & Biorepository Collaboratorium Guam EPSCoR, Marine Laboratory, University of Guam, Mangilao, United States + + + +Author + +Medeiros, Jade +Laboratório de Ictiologia (LABICT), Departamento de Sistemática e Ecologia, Universidade Federal da Paraíba, João Pessoa, Brazil + + + +Author + +Arthur + + + +Author + +Lima +Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil + + + +Author + +Rosa, Ricardo S. +Laboratório de Ictiologia (LABICT), Departamento de Sistemática e Ecologia, Universidade Federal da Paraíba, João Pessoa, Brazil + + + +Author + +Loboda, Thiago S. +Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil + + + +Author + +B., João Paulo C. + + + +Author + +Silva +Laboratório de Ictiologia (LABICT), Departamento de Sistemática e Ecologia, Universidade Federal da Paraíba, João Pessoa, Brazil + +text + + +Zoological Journal of the Linnean Society + + +2024 + +2024-09-21 + + +202 + + +1 + + +1 +24 + + + + +http://dx.doi.org/10.1093/zoolinnean/zlae104 + +journal article +10.1093/zoolinnean/zlae104 +0024-4082 + + + + + +Morphological description of the neurocranium in +Potamotrygonidae + + + + + +Ethmoid region + + +The neurocranium in +Potamotrygonidae +is elongated, with its greatest width at the middle portion of the nasal capsules (ncs). The nasal capsules are located on the anteriormost region, being ventrolaterally expanded and with their openings directed ventrally. In + +Styracura + +the nasal capsules are oval and bear a median indentation in-between the convex anterior margins ( +Fig. 1C +; Supporting Information, File S1). The same morphology is seen in the species of + +Potamotrygon + +and + +Plesiotrygon + +( +Fig. 1A, B +) (Supporting Information, Files S2, S3, S4). In + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon + +the nasal capsules are ventromedially divided by a thin nasal septum that is one-sixth the width of the nasal aperture ( +Fig. 2 +). + +Heliotrygon + +and + +Paratrygon + +have comparatively shorter nasal capsules anteroposteriorly ( +Fig. 3 +) (Supporting Information, Files S5, S6), with the anterior margin of the capsules also convex, but less rounded when compared to the general pattern present in the other genera. The nasal septum in + +Heliotrygon +and +Paratrygon + +is wider, with nearly half the width of the nasal aperture ( +Fig. 4 +). + +Paratrygon + +shows a small rostral projection (rpj) in-between the anterior margin of the two nasal capsules, which can also be seen in some species of + +Potamotrygon + +( +Figs 3B +, +4B +; Supporting Information, File S6). + + +The condyles for the articulation with the antorbital cartilage (cac) are situated laterally on the nasal capsules. In + +Styracura + +, + +Paratrygon + +, and species of + +Potamotrygon + +this condyle is bean-shaped ( +Figs 5A, C +, +6B +), while on + +Plesiotrygon + +and + +Heliotrygon + +this condyle is rounded ( +Figs 5B +, +6A +). The anteroposteriorly flattened antorbital cartilages (anto) extend posterolaterally from the nasal capsules. In + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon + +the antorbital cartilage’s length is one-third of the width of the nasal capsules, whilst in + +Heliotrygon + +and + +Paratrygon + +they are smaller and not as posteriorly oriented, with its length corresponding to a quarter of the nasal capsule’s width ( +Figs 1 +, +2 +). In + +Heliotrygon + +the antorbital cartilage has a foramen (acf) that is absent on the other genera ( +Fig. 7 +). + + +The nasal capsules, which are ventrally projected, form a slope in relation to the basicranium. In + +Styracura + +and + +Potamotrygon + +this ventral projection forms an angle of nearly 130° in relation to the basicranium ( +Fig. 5A, C +), while in + +Plesiotrygon + +this angle is less accentuated, close to 170° ( +Fig. 5B +). In + +Heliotrygon + +and + +Paratrygon + +the inclination is more accentuated and closer to 100° in relation to the basicranium ( +Fig. 6 +). In + +Styracura + +, + +Potamotrygon + +, + +Plesiotrygon + +, and + +Heliotrygon + +the condyle for the articulation with the antorbital cartilage is anteroventral to the preorbital process ( +Figs 5 +, +6A +), while in + +Paratrygon + +this condyle is situated ventrally and at a level with the preorbital process ( +Fig. 6B +). Furthermore, + +Heliotrygon + +can be distinguished from the other potamotrygonins by having two pairs of condyle-like structures (nco) on the anterior face of its nasal capsules ( +Fig. 7 +). These condyles articulate with the anterior segment of the propterygium (apro) and are absent in the other genera. + + +The preorbital process (prp) is posterodorsal to the nasal capsules. In + +Styracura + +, + +Potamotrygon + +, and + +Paratrygon + +it extends laterally beyond the longitudinal line with the lateral margin of the nasal capsules ( +Figs 1A, C +, +3B +). In + +Plesiotrygon + +the preorbital process reaches the longitudinal line with the nasal capsules, while in + +Heliotrygon + +the preorbital process is shorter and does not reach that same longitudinal line at the lateral limit of the nasal capsules ( +Figs 1B +, +3A +). Furthermore, only in + +Styracura + +and + +Potamotrygon + +does the preorbital process project posterolaterally, while in + +Plesiotrygon + +, + +Heliotrygon + +, and + +Paratrygon + +the preorbital process projects laterally ( +Figs 1 +, +3 +). The anterior foramen for preorbital canal (afpc) and the posterior foramen for preorbital canal (pfpc) pierce the base of the preorbital process dorsally, and are housed in a fossa that opens anteriorly. In + +Heliotrygon + +and + +Paratrygon + +this fossa is placed medially ( +Fig. 3 +), while in the other genera it is lateral and closer to the edge of the preorbital process ( +Fig. 1 +). Differently from the other genera, in + +Heliotrygon + +the foramen for preorbital canal is not divided into two openings. In + +Styracura + +, + +Potamotrygon + +, and + +Paratrygon + +the ventral opening of afpc occupies the anterior portion of the base of the preorbital process, while pfpc opens ventrally at the posterior region of the base of the preorbital process ( +Figs 5A, C +, +6B +), except in + +Styracura + +, where the pfpc is positioned further back beyond the base of the preorbital process ( +Fig. 5C +). In + +Plesiotrygon + +both the foramen for anterior and posterior preorbital canal open posteroventrally at the base of the preorbital process ( +Fig. 5B +; Supporting Information, Files S2, S7). + + + +Figure 1. +Neurocrania of + +Potamotrygon albimaculata + +(A), + +Plesiotrygon iwamae + +(B), and + +Styracura schmardae + +(C) in dorsal views. Anatomical abbreviations: afpc, anterior foramen for preobirtal canal; anto, antorbital cartilage; elf, endolymphatic foramina; epp, epiphysial process; fpf, frontoparietal fontanelle; ncs, nasal capsules; pcf, precerebral fontanelle; plf, perilymphatic foramina; pop, postorbital process; prp, preorbital process; soc, supraorbital crest; sp, supraorbital process. + + + + +Figure 2. +Neurocrania of + +Potamotrygon albimaculata + +(A), + +Plesiotrygon iwamae + +(B), and + +Styracura schmardae + +(C) in ventral views. Anatomical abbreviations: acvf, anterior cerebral vein foramen; afpc, anterior foramen for preobirtal canal; anto, antorbital cartilage; as, articular surface; icaf, internal carotid artery foramen; nap, nasal aperture; pfpc, posterior foramen for preorbital canal; pop, postorbital process; prp, preorbital process; sp, supraorbital process; II, optic nerve foramen. + + + +The precerebral fontanelle (pcf) is rounded in + +Styracura + +, + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +, while in + +Heliotrygon + +the precerebral fontanelle is elliptical and narrow ( +Figs 1 +, +3 +). Posterior to the precerebral fontanelle there is an epiphysial process (epp), which delimits the two fontanelles of the neurocranium, except for + +Styracura + +, where this structure is absent. In + +Heliotrygon + +the epiphysial process is the shortest among all genera analysed (with one-third the width of the supraorbital process) ( +Fig. 3A +), while + +Potamotrygon + +and + +Plesiotrygon + +have the longest epiphysial process, which is longer than the supraorbital process ( +Fig. 1A, B +). + +Paratrygon + +shows an intermediate state and its epiphysial process has nearly the same length of the supraorbital process ( +Fig. 3B +). + + + +Figure 3. +Neurocrania of + +Heliotrygon rosai + +(A) and + +Paratrygon aiereba + +(B) in dorsal views. Anatomical abbreviations: afpc, anterior foramen for preobirtal canal; anto, antorbital cartilage; elf, endolymphatic foramina; epp, epiphysial process; fpc, foramen for preorbital canal; fpf, frontoparietal fontanelle; nco, nasal condyles; ncs, nasal capsules; pcf, precerebral fontanelle; plf, perilymphatic foramina; pop, postorbital process; prp, preorbital process; rpj, rostral projection; soc, supraorbital crest; sp, supraorbital process. + + + +Dorsal optic region + + +Thesupraorbitalcrest (soc) ispiercedbyaseriesofsmallforamina for the superficial ophthalmic nerve (sup). They appear posterior to the preorbital process and extend posteriorly throughout the orbital region, reaching the small (half the postorbital process length at most) and triangular supraorbital process (sp). In all genera the lateral extension of the supraorbital crest in relation to the basicranium is short, except for + +Heliotrygon + +, in which the crest is a well-developed, shelf-like structure ( +Figs 4A +, +8 +). The supraorbital process is triangular-shaped and laterally projected, except for + +Styracura + +, in which the supraorbital process is anteriorly oriented ( +Fig. 1C +). + + +The postorbital process (pop) is posterior to the supraorbital process, being a rectangular and shelf-like plate that extends anterolaterally from the anterodorsal portion of the otic region of the neurocranium. In + +Styracura + +the postorbital process is larger than the other four genera, with its base wider than the length of the otic region ( +Fig. 1C +). In + +Heliotrygon + +the distal margin of the postorbital process is concave, distinct from the other four genera, in which this margin is straight ( +Fig. 3A +). In relation to its base, the distal margin of the postorbital process is only narrower in + +Plesiotrygon + +( +Fig 1B +). In + +Styracura + +, + +Potamotrygon + +, and + +Paratrygon + +the anterolateral portion of the postorbital process surpasses anteriorly the lateral tip of the supraorbital processes, while in + +Heliotrygon + +and + +Plesiotrygon + +it is horizontally aligned with the lateral tip of the supraorbital process ( +Figs 1 +, +3 +). Furthermore, the posterior margin of the postorbital process is straight in all genera, except for + +Styracura + +, which has a slight convex projection near its distal tip ( +Fig. 1C +). + + +The frontoparietal fontanelle (fpf) is slender and elongated in all genera ( +Figs 1 +, +3 +). In + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon + +the frontoparietal fontanelle is wider anteriorly, narrowing posteriorly, being somewhat triangular in shape ( +Fig. 1 +). In + +Potamotrygon + +the frontoparietal fontanelle bears a slight constriction at its midportion, giving it an hourglass-shape ( +Fig. 1A +). In + +Heliotrygon + +and + +Paratrygon + +the frontoparietal fontanelle has the same width throughout ( +Fig. 3 +). In + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon + +the width of the anterior portion of the frontoparietal fontanelle occupies approximately one-third of the dorsal surface of the neurocranium ( +Fig. 1 +), while in + +Paratrygon + +and + +Heliotrygon + +it occupies a quarter of the dorsal surface of the neurocranium ( +Fig. 3 +). + + + +Figure 4. +Neurocrania of + +Heliotrygon rosai + +(A) and + +Paratrygon aiereba + +(B) in ventral views. Anatomical abbreviations: acvf, anterior cerebral vein foramen; afpc, anterior foramen for preobirtal canal; anto, antorbital cartilage; as, articular surface; fpc, foramen for preorbital canal; icaf, internal carotid artery foramen; lc, lateral commissure; nap, nasal aperture; nco, nasal condyles; obf, orbital fissure; pfpc, posterior foramen for preorbital canal; pop, postorbital process; prp, preorbital process; rpj, rostral projection; soc, supraorbital crest; sp, supraorbital process; II, optic nerve foramen. + + + +Orbital region + + +The neurocranium is pierced laterally by several foramina. Ventrally at the base of the preorbital process all genera bear two foramina for the preorbital canal ( +Figs 5 +, +6B +), except for + +Heliotrygon + +, which has only one ( +Fig. 6A +). In + +Styracura + +the position of the posterior foramen for preorbital canal is completely posterior to the preorbital process ( +Fig. 5C +), while in the other genera this posterior opening is located on the posterior margin of the preorbital process. Only in + +Plesiotrygon + +, both foramina for the preorbital canal are on the posterior margin of the preorbital process ( +Fig. 5B +). The anteriormost foramen on the orbital wall is the anterior cerebral vein foramen (acvf). In all genera its position is anterior to, and close to, the dorsal margin of the optic nerve foramen (II). Only + +Plesiotrygon + +presents a different placement of this foramen, which is anterodorsal and not at the same level of the dorsal margin of the optic nerve foramen ( +Fig. 5B +). The wide (at least the same size as the orbital fissure) and oval optic nerve foramen (II) is situated centrally on the orbital wall. The trochlear nerve foramen (IV) is located dorsally to the optic nerve foramen, and may vary in its position amongst genera of +Potamotrygonidae +. In + +Styracura + +, + +Potamotrygon + +, + +Plesiotrygon + +, and + +Heliotrygon + +it is dorsal to the midportion of the optic nerve foramen ( +Figs 5 +, +6A +); in + +Paratrygon + +it is posterior to the midportion of the optic nerve foramen ( +Fig. 6B +). + + +In + +Styracura + +and + +Paratrygon + +the distance between the trochlear nerve foramen and the optic nerve foramen is less than half the height of the optic nerve foramen ( +Figs 5C +, +6B +), while in + +Plesiotrygon + +this distance is equal to the height of the optic nerve foramen ( +Fig. 5B +). In + +Potamotrygon + +and + +Heliotrygon + +this distance is intermediate ( +Figs 5A +, +6A +). Posterior to the optic nerve foramen is the eye stalk (es), which is rounded, except for + +Heliotrygon + +, in which the eye stalk is oval ( +Fig. 6A +). Immediately dorsal to the eye stalk is the oculomotor nerve foramen (III). In + +Potamotrygon + +and + +Heliotrygon + +the oculomotor nerve foramen is anterodorsal to the eye stalk ( +Figs 5A +, +6A +). + + +The efferent spiracular artery foramen (esaf) is ventral to the eye stalk, although in + +Styracura + +and + +Potamotrygon + +it is anteroventral and in-between the eye stalk and the optic nerve foramen ( +Fig. 5A, C +). The internal carotid foramen (icaf) is positioned anterior to the hyomandibular branch of the facial nerve foramen (VII) and in + +Styracura + +, + +Plesiotrygon + +, and + +Heliotrygon + +it is ventrolaterally positioned, occupying the margin that divides the orbital wall and the basicranium ( +Figs 5B, C +, +6A +). In contrast, + +Potamotrygon + +and + +Paratrygon + +present this foramen positioned ventrally on the basicranium ( +Figs 2A +, +3B +). The orbital fissure (obf) is situated on the posteriormost portion of the orbital region. In + +Heliotrygon + +, + +Paratrygon + +, and + +Plesiotrygon + +the orbital fissure is about the same size as the optic nerve foramen, while in + +Styracura + +and + +Potamotrygon + +it is about half the size of the optic nerve foramen ( +Figs 5 +, +6 +; Supporting Information, Files S1, S3, S4). In + +Potamotrygon + +and + +Heliotrygon + +the orbital fissure is covered laterally by the posterodorsal wall of the neurocranium, immediately ventral to the postorbital process ( +Figs 5A +, +6A +), while in the other genera the fissure is completely visible laterally. + + + +Figure 5. +Neurocrania of + +Potamotrygon albimaculata + +(A), + +Plesiotrygon iwamae + +(B), and + +Styracura schmardae + +(C) in left lateral views. Anatomical abbreviations: acvf, anterior cerebral vein foramen; afpc, anterior foramen for preobirtal canal; cac, condyle for the antorbital cartilage; es, eye stalk; esaf, efferent spiracular artery foramen; hmdf, hyomandibular facet; icaf, internal carotid artery foramen; lc, lateral commissure; ncs, nasal capsules; obf, orbital fissure; pfpc, posterior foramen for preorbital canal; pop, postorbital process; prp, preorbital process; jla, jugal arch; sp, supraorbital process; II, optic nerve foramen; III, oculomotor nerve foramen; IV, trochlear nerve foramen; VII, hyomandibular branch of the facial nerve foramen; IX, glossopharyngeal nerve foramen. + + + + +Figure 6. +Neurocrania of + +Heliotrygon rosai + +(A) and + +Paratrygon aiereba + +(B) in left lateral views. Anatomical abbreviations: acvf, anterior cerebral vein foramen; afpc, anterior foramen for preobirtal canal; cac, condyle for the antorbital cartilage; es, eye stalk; esaf, efferent spiracular artery foramen; fpc, foramen for preorbital canal; hmdf, hyomandibular facet; icaf, internal carotid artery foramen; lc, lateral commissure; ncs, nasal capsules; obf, orbital fissure; pfpc, posterior foramen for preorbital canal; pop, postorbital process; prp, preorbital process; sp, supraorbital process; II, optic nerve foramen; III, oculomotor nerve foramen; IV, trochlear nerve foramen; VII, hyomandibular branch of the facial nerve foramen; IX, glossopharyngeal nerve foramen. + + + +Otic region + + +The lateral commissure (lc) is an arch that bridges over the foramen for the hyomandibular branch of the facial nerve. In + +Styracura + +and + +Plesiotrygon + +the lateral commissure is septate (bears two openings) and connects medially with the lateral wall of the otic region ( +Fig. 5B, C +). The hyomandibular facet (hmdf), which is posterior to the lateral commissure, corresponds to a nearly elliptical and oblique depression. In + +Styracura + +and + +Plesiotrygon + +the hyomandibular facet is oval and not with its anterior portion wider than its posterior portion ( +Fig. 5B, C +). Moreover, + +Heliotrygon + +is the only genus in which the ventral margin of the hyomandibular facet is somewhat arched medially ( +Fig. 6A +). + +Plesiotrygon + +differs from all the other genera by the presence of a chondrified jugal arch (jla) that bridges laterally on the otic region, immediately posterior to the hyomandibular facet ( +Fig. 5B +; Supporting Information, File S2). + + + +Figure 7. +Neurocranium of + +Heliotrygon rosai + +in frontal view. Anatomical abbreviations: acf, antorbital cartilage foramen; anto, antorbital cartilage; fpc, foramen for preorbital canal; nco, nasal condyles; ncs, nasal capsules; pcf, precerebral fontanelle; prp, preorbital process. + + + + +Figure 8. +Neurocrania of + +Heliotrygon rosai + +(A) and + +Potamotrygon albimaculata + +(B) in anterior oblique views. A1, anterior view of the cutting section dividing the neurocranium of + +Heliotrygon rosai + +on anterior and posterior regions. B1, anterior view of the cutting section dividing the neurocranium of + +Potamotrygon albimaculata + +on anterior and posterior regions. Anatomical abbreviations: acf, antorbital cartilage foramen; afpc, anterior foramen for preorbital canal; anto, antorbital cartilage; epp, epiphyseal process; fpc, foramen for preorbital canal; fpf, frontoparietal fontanelle; nco, nasal condyles; ncs, nasal capsules; oc, occipital condyle; pcf, precerebral fontanelle; pop, postorbital process; prp, preorbital process; soc, supraorbital crest; sor, supraotic ridge; sp, supraorbital process; spr, sphenopterotic ridge; II, optic nerve foramen; IX, glossopharyngeal nerve foramen. + + + + +Figure 9. +Neurocrania of + +Potamotrygon albimaculata + +(A), + +Plesiotrygon iwamae + +(B), and + +Styracura schmardae + +(C) in posterior views. Anatomical abbreviations: as, articular surface; elf, endolymphatic foramina; flb, foramen of the lateralis branch of the vagus nerve; fm, foramen magnum; hmdf, hyomandibular facet; oc, occipital condyle; plf, perilymphatic foramina; pop, postorbital process; jla, jugal arch; sor, supraotic ridge; spr, sphenopterotic ridge; IX, glossopharyngeal nerve foramen; X, vagus nerve foramen. + + + +The glossopharyngeal nerve foramen (IX) varies in its position, and is somewhere between the otic and occipital regions. In + +Heliotrygon + +and + +Paratrygon + +this foramen is visible laterally, on the posteroventral portion of the otic region ( +Fig. 6 +). In the other three genera the glossopharyngeal nerve foramen is dorsolateral to the occipital condyles and occupies the ventral lateral portion of the occipital region, being visible in posterior oblique view ( +Fig. 5 +). The sphenopterotic ridge (spr) projects dorsally on the lateral portions of the otic region, with the supraotic ridge (sor) extending laterally from the otic region walls above the hyomandibular facet. In + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon + +the spr is as long as the lateral extension of the sor ( +Fig. 9 +). Dorsally, a pair of endolymphatic foramina (elf) is followed posteriorly by a pair of perilymphatic foramina (plf). In + +Heliotrygon + +and + +Potamotrygon + +the perilymphatic foramina are not immediately posterior, but posterolateral and posteromedial to the endolymphatic foramina, respectively ( +Figs 1A +, +3A +). In + +Heliotrygon + +and + +Plesiotrygon + +both pairs of foramina are clearly different in size, with the perilymphatic foramina being the largest in + +Heliotrygon + +(three times the size of the endolymphatic foramina) ( +Fig. 3A +). + + +Occipital region + + +The large and oval foramen magnum (fm) is located in-between a pair of vagus nerve foramina (X). Only in + +Styracura + +is the foramen magnum taller than wider, and the lateral limit of the vagus nerve foramen reaches the medial level of the sphenopterotic ridge ( +Fig. 9C +). The foramen magnum is the smallest (eight times the aperture of the vagus nerve foramen) in + +Heliotrygon + +and the largest in + +Styracura + +and + +Potamotrygon + +(12 times the aperture of the vagus nerve foramen) ( +Figs 9A, C +, +10A +). The vagus nerve foramen is positioned dorsal to the midportion of the foramen magnum, closer to its dorsal margin in +Styraruca +and + +Potamotrygon + +( +Fig. 9A, C +), while in the other genera it is situated level with the midportion of the foramen magnum ( +Figs 9B +, +10 +). The foramen of the lateralis branch of the vagus nerve (flb) is juxtaposed to the vagus nerve foramen in + +Heliotrygon + +, + +Potamotrygon + +, and + +Plesiotrygon + +( +Figs 9A, B +, +10A +), while in + +Styracura + +and + +Paratrygon + +this foramen is positioned far from the vagus nerve foramen ( +Figs 9C +, +10B +). The articular surface (as) is located in-between a pair of occipital condyles (oc), which are horizontally arranged and immediately ventral to the foramen magnum. + +Plesiotrygon + +presents the narrowest articular surface (one-third of the occipital condyle’s width), while + +Heliotrygon + +has the widest in relation to the occipital condyles (two-thirds of the occipital condyle’s width) ( +Figs 9B +, +10A +). In + +Potamotrygon + +and + +Plesiotrygon + +the ventral margin of the occipital condyles is medially arched ( +Fig. 9A, B +), while in the other three genera the ventral margin is straight. + +Paratrygon + +and + +Heliotrygon + +have medially and laterally inclined occipital condyles, respectively ( +Fig. 10 +), instead of the usual horizontal orientation seen in + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon +. + +The occipital condyles extend posteriorly from the basicranium and in + +Styracura + +, + +Potamotrygon + +, and + +Plesiotrygon + +this extension is shorter than half the length of the hyomandibular facet ( +Fig. 9 +), while in + +Heliotrygon + +and + +Paratrygon + +the posterior extension of the condyles is greater, around two-thirds the length of the hyomandibular facet ( +Fig. 10 +). In + +Heliotrygon + +and + +Paratrygon + +the occipital condyles reach the lateral limit of the occipital region, resulting in a straighter posterior outline of the neurocranium, while in the other genera they are shorter and the shape of the occipital region is irregular ( +Fig. 10 +). + + + +Figure 10. +Neurocrania of + +Heliotrygon rosai + +(A) and + +Paratrygon aiereba + +(B) in posterior views. Anatomical abbreviations: as, articular surface; elf, endolymphatic foramina; flb, foramen of the lateralis branch of the vagus nerve; fm, foramen magnum; hmdf, hyomandibular facet; oc, occipital condyle; plf, perilymphatic foramina; pop, postorbital process; sor, supraotic ridge; spr, sphenopterotic ridge; X, vagus nerve foramen. + + + +Character descriptions + +The descriptions of 60 newly proposed morphological characters based on the anatomy of the neurocranium, 15 of them consisting of multistate ordered characters, is given below. Characters are organized by regions of the neurocranium. + +Ethmoid region + + +1. +Rostral projection: (0) absent; (1) present. + + +In + +Styracura + +(outgroup), + +Plesiotrygon + +, and + +Heliotrygon + +the neurocranium does not present an anteromedian rostral projection (0). In + +Potamotrygon + +the rostral projection is polymorphic, with the majority of the species lacking this structure, while the rostral projection is present in + +Potamotrygon marquesi + +, + +Potamotrygon signata + +, and + +Potamotrygon wallacei + +(0,1). In + +Paratrygon + +a small chondrified rostral projection is present in-between the anterior margin of the nasal capsules (1) ( +Figs 3B +, +4B +). This character was previously explored by +Rosa (1985) +. + + +2. +Nasal septum; width: (0) one-sixth the width of the nasal aperture; (1) half the width of the nasal aperture. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, and + +Plesiotrygon + +the nasal septum, which divides the two nasal capsules medially, is one-sixth the width of the nasal aperture (0) ( +Fig. 2 +). In + +Heliotrygon + +and + +Paratrygon + +the nasal septum is wider and about half the width of the nasal aperture (1) ( +Fig. 4 +). This character was previously explored by +Carvalho and Lovejoy (2011) +. + + +3. +Condyles on the anterior margin of the nasal capsules: (0) absent; (1) present. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the nasal capsules do not bear condyles on their anterior margin (0) ( +Figs 1 +, +2 +, +3B +, +4B +). In + +Heliotrygon + +the anterior margin of the nasal capsules has two pairs of condyles for the articulation with the distal segment of the propterygium (1) ( +Figs 3A +, +4A +, +7 +). + + +4. +Condyle for the articulation with the antorbital cartilage; position: (0) anteroventral in relation to the preorbital process; (1) ventral in relation to the preorbital process. + + +In + +Styracura + +(outgroup), + +Plesiotrygon + +, + +Potamotrygon + +, and + +Heliotrygon + +the condyle for the articulation with the antorbital cartilage is anteroventral in relation to the preorbital process (0) ( +Figs 5 +, +6A +). In + +Paratrygon + +the condyle for the articulation with the antorbital cartilage is ventral and vertically aligned to the preorbital process (1) ( +Fig. 6B +). + + +5. +Condyle for the articulation with the antorbital cartilage; shape: (0) bean-shaped; (1) round. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the condyle for the articulation with the antorbital cartilage is nearly bean-shaped (0) ( +Figs 5C +, +6B +). In + +Potamotrygon + +this character is polymorphic, with + +Potamotrygon brachyura + +, + +Potamotrygon histrix + +, and + +Potamotrygon orbignyi + +with the condyle for the articulation with the antorbital cartilage being round in format, while it is bean-shaped on the remaining species (0,1). In + +Plesiotrygon + +and + +Heliotrygon + +the condyle for the articulation with the antorbital cartilage is rounded (1) ( +Figs 5B +, +6A +). + + +6. +Condyle for the articulation with the antorbital cartilage; depression: (0) anterior; (1) dorsal. + + +In + +Styracura + +(outgroup) the condyle for the articulation with the antorbital cartilage has a depression on its anterior region (0) ( +Fig. 5C +). In + +Potamotrygon + +this character is polymorphic (0,1), with + +Potamotrygon pantanensis + +bearing a dorsal depression on the condyle for the articulation with the antorbital cartilage. In + +Paratrygon + +the depression is dorsal on the condyle for the articulation with the antorbital cartilage (1) ( +Fig. 6B +). + + +7. +Antorbital cartilage; length: (0) half the width of the nasal capsules; (1) one-third the width of the nasal capsules; (2) a quarter the width of the nasal capsules [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the length of the antorbital cartilage is one-third the width of the pair of nasal capsules (0) ( +Figs 1 +, +2 +). In + +Potamotrygon + +this character is polymorphic and the antorbital cartilage can be both half or one-third the width of the nasal capsules (0,1). In + +Heliotrygon + +and + +Paratrygon + +the antorbital length is a quarter the width of the pair of nasal capsules (2) ( +Figs 3 +, +4 +). This character was previously explored by +Carvalho and Lovejoy (2011) +. + + +8. +Antorbital cartilage foramen: (0) absent; (1) present. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +,and + +Paratrygon + +the antorbital cartilage foramen is absent (0). In + +Heliotrygon + +the antorbital cartilage is pierced by a foramen (1) ( +Fig. 7 +). + + +9. +Nasal capsules in relation to the basicranium; angulation in lateral view: (0) 170°; (1) 130°; (2) 100° [multistate ordered]. + + +In + +Styracura + +(outgroup) the nasal capsules are curved ventrally and forming an angle of nearly 130° in relation to the basicranium (1) ( +Fig. 5A, C +). In + +Potamotrygon + +this character is polymorphic. In + +Potamotrygon scobina + +the nasal capsules form an angle of nearly 170°, while in the remaining species this angle is closer to 130° (0,1). In + +Plesiotrygon + +the nasal capsules are slightly curved ventrally and forming an angle of nearly 170° in relation to the basicranium (0) ( +Fig. 5B +). In + +Paratrygon + +and + +Heliotrygon + +the nasal capsules are considerably curved ventrally and forming an angle of nearly 100° in relation to the basicranium (2) ( +Fig. 6 +). + + +10. +Preorbital process; orientation: (0) posteriorly curved; (1) laterally projected. + + +In + +Styracura + +(outgroup) and + +Potamotrygon + +the preorbital process is curved posteriorly (0) ( +Figs 1A, C +, +2A, C +). In + +Plesiotrygon + +, + +Heliotrygon + +, and + +Paratrygon + +the preorbital process extends laterally without curving posteriorly (1) ( +Figs 1B +, +2B +, +3 +, +4 +). + + +11. +Preorbital process; lateral extension in relation to the nasal capsules: (0) preorbital process extends laterally beyond the longitudinal line with the lateral margin of the nasal capsules; (1) preorbital process extends laterally and is longitudinally aligned with the lateral margin of the nasal capsules; (2) preorbital process fails to reach the longitudinal line with lateral margin of the nasal capsules [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the preorbital process extends laterally beyond the longitudinal line with the lateral margin of the nasal capsules (0) ( +Figs 1A, C +, +3B +). In + +Potamotrygon + +this character is polymorphic, with the preorbital process extending laterally beyond or aligned with the longitudinal line with lateral margin of the preorbital process (0,1). In + +Plesiotrygon + +the lateral extension of the preorbital process extends laterally and is longitudinally aligned with the lateral margin of the nasal capsules (1) ( +Fig. 1B +). In + +Heliotrygon + +the preorbital process fails to reach the longitudinal line with the lateral limit of the nasal capsules (2) ( +Fig. 3A +). This character was previously explored by +Carvalho and Lovejoy (2011) +. + + +12. +Precerebral fontanelle; development in relation to the frontoparietal fontanelle: (0) at least one-third wider than the frontoparietal fontanelle; (1) as wide as the frontoparietal fontanelle. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +, the precerebral component of the fontanelle is at least one-third wider than the frontoparietal component (0) ( +Figs 1 +, +3B +). In + +Heliotrygon + +both components of the fontanelle have the same width (1) ( +Fig. 3A +). + + +13. +Precerebral fontanelle; shape: (0) rounded; (1) elliptical. + + +In + +Styracura + +(outgroup), + +Plesiotrygon + +, and + +Paratrygon + +the precerebral fontanelle is as wide as it is long, being rounded in shape (0) ( +Figs 1 +, +3B +). In + +Potamotrygon + +, only + +Potamotrygon schroederi + +has an elliptical precerebral fontanelle (0,1). In + +Heliotrygon + +the precerebral fontanelle is anteroposteriorly elongated, with its width about half its length (1) ( +Fig. 3A +). This character was previously explored by +Carvalho and Lovejoy (2011) +. + + +14. +Epiphysial process: (0) absent; (1) present. + + +In + +Styracura + +(outgroup) the epiphysial process is absent (0) ( +Fig. 1C +). In all members of Potmotrygoninae, namely + +Potamotrygon + +, + +Plesiotrygon + +, + +Paratrygon + +, and + +Heliotrygon + +the chondrified epiphysial process is present (1) ( +Figs 1A, B +, +3 +). + + +15. +Epiphysial process; development: (0) with one-third the length of the supraorbital process; (1) with the same length of the supraorbital process; (2) one-third longer than the length of the supraorbital process [multistate ordered]. + + +In + +Heliotrygon + +the epiphysial bar is short, with about one-third the length of the supraorbital process (0) ( +Fig. 3A +). In + +Paratrygon + +the epiphysial bar extends medially having the same length of the supraorbital process (1) ( +Fig. 3B +). In + +Plesiotrygon + +the epiphyseal bar is one-third longer than the length of the supraorbital process (2) ( +Fig. 1B +). In + +Potamotrygon + +this character is polymorphic, with all three character states occurring among the species (0,1,2) (Supporting Information, Files S3, S4). This character is inapplicable for + +Styracura + +( +Fig. 1C +). + + +16. +Epiphysial process; orientation: (0) medially projected; (1) anteromedially projected. + + +In + +Heliotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the epiphysial bar is oriented medially (0) ( +Fig. 1B +, +3 +). In + +Potamotrygon + +the epiphysial bar can be anteromedially or medially oriented (0,1) ( +Fig. 1A +; Supporting Information, Files S3, S4). This character is inapplicable for + +Styracura + +. + + +Dorsal optic region + + +17. +Frontoparietal fontanelle; width in relation to the neurocranium: (0) one-third the width of the neurocranium on its anteriormost portion; (1) a quarter the width of the neurocranium on its anteriormost portion. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the anterior portion of the frontoparietal fontanelle is one-third the width of the neurocranium (0) ( +Fig. 1 +). In + +Paratrygon + +and + +Heliotrygon + +the width of the frontoparietal fontanelle is a quarter the width of the neurocranium (1) ( +Fig. 3B +). In + +Potamotrygon + +this character is polymorphic and the width of the frontoparietal fontanelle can be one-third or a quarter the width of the neurocranium (0,1). This character was previously explored by +Carvalho and Lovejoy (2011) +. + + +18. +Frontoparietal fontanelle; ratio between anterior and posterior regions: (0) anterior region 1.5 times wider than its posterior portion; (1) anterior region as wide as its posterior portion. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the anterior region of the frontoparietal fontanelle is around 1.5 times wider than its posterior region (0) ( +Fig. 1B, C +). In + +Heliotrygon + +and + +Paratrygon + +the anterior and posterior portions of the frontoparietal fontanelle have the same width (1) ( +Fig. 3 +). In + +Potamotrygon + +the anterior portion of the frontoparietal fontanelle can be 1.5 times wider or may have the same width as its posterior portion (0,1). This character was previously explored by +Carvalho and Lovejoy (2011) +. + + +19. +Frontoparietal fontanelle; midportion constriction: (0) absent; (1) present. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the frontoparietal fontanelle has no constriction on its midlength (0) ( +Figs 1B, C +). In some + +Potamotrygon +species + +the frontoparietal fontanelle has a midlength extension of the neurocranium ceiling forming a constriction, resulting in an hourglass-like outline of the fontanelle, while other species lack such constriction, making this character polymorphic (0,1) ( +Fig. 1A +). This character is coded as inapplicable for + +Heliotrygon + +and + +Paratrygon +. + + + +20. +Supraorbital crest; development: (0) with one-fifth or less the width of the supraorbital process; (1) as wide as the supraorbital process. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the lateral extension of the supraorbital crest is about one-fifth or less the width of the supraorbital process (0) ( +Figs 2 +, +4B +, +8 +) (Supporting Information, Files S1–S4, S6). In + +Heliotrygon + +the supraorbital crest is clearly developed, being as wide as the supraorbital process (1) ( +Figs 3A +, +4A +, +8 +; Supporting Information, File S5). + + +21. +Postorbital process; distal margin: (0) straight; (1) concave. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the distal margin of the postorbital process has a straight outline (0) ( +Figs 1 +, +3B +). In + +Heliotrygon + +the distal margin of the postorbital process is concave (1) ( +Fig. 3A +). + + +22. +Postorbital process; width of its distal margin in relation to its proximal region: (0) its distal portion a quarter narrower in relation to its proximal region; (1) its distal portion a quarter wider than its proximal region; (2) its distal portion with twice the width of its proximal region [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the distal margin of the postorbital process is nearly a quarter wider than its proximal region (1) ( +Figs 1C +, +3B +). In + +Heliotrygon + +the distal margin of the postorbital process has twice the width of its proximal region (2) ( +Fig. 3A +). In + +Plesiotrygon + +the distal portion of the postorbital process is a quarter narrower in relation to its proximal region (0) ( +Fig. 1B +). This character is polymorphic in + +Potamotrygon + +and the distal margin of the postorbital process can be both a quarter narrower or a quarter wider than its proximal region (0,1). + + +23. +Postorbital process; anterolateral extension: (0) surpassing anteriorly the lateral tip of the supraorbital process; (1) aligned with the lateral tip of the supraorbital process. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the anterolateral portion of the postorbital process extends anteriorly surpassing the lateral tip of the supraorbital process (0) ( +Figs 1C +, +3B +). In + +Plesiotrygon + +and + +Heliotrygon + +the anterolateral portion of the postorbital process is horizontally aligned with the lateral tip of the supraorbital process (1) ( +Figs 1B +, +3A +). In + +Potamotrygon + +this character is polymorphic. In some species the anterolateral portion of the postorbital process surpasses the lateral tip of the supraorbital process, while in others it is horizontally aligned with it (0,1) ( +Fig. 1A +). + + +24. +Supraorbital process; length: (0) with one-fifth the length of the postorbital process; (1) with one-third the length of the postorbital process; (2) with half the length of the postorbital process [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the supraorbital process corresponds to one-third the length of the postorbital process (1) ( +Fig. 1B, C +). In + +Paratrygon + +the supraorbital process is shorter, corresponding to one-fifth the length of the postorbital process (0) ( +Fig. 3B +). In + +Heliotrygon + +the lateral projection of the supraorbital process is half the length of its postorbital process (2) ( +Fig. 3A +). In + +Potamotrygon + +the three character states can be found (0,1,2) ( +Fig. 1A +). + + +25. +Supraorbital process; orientation: (0) anterolaterally oriented; (1) laterally oriented. + + +In + +Styracura + +(outgroup) the supraorbital process is anterolaterally oriented (0) ( +Fig. 1C +). In + +Potamotrygon + +, + +Plesiotrygon + +, + +Paratrygon + +, and + +Heliotrygon + +the supraorbital process is laterally oriented (1) ( +Figs 1A, B +, +3 +). + + +26. +Postorbital process; length: (0) its anterolateral portion failing to reach the longitudinal level of the lateral tip of the preorbital process; (1) its anterolateral portion longitudinally aligned with the lateral tip of the preorbital process; (2) its anterolateral portion extending laterally beyond the lateral tip of the preorbital process [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Heliotrygon + +the anterolateral edge of the postorbital process is longitudinally aligned with the lateral tip of the preorbital process (1) ( +Figs 1C +, +3A +). In + +Potamotrygon + +the anterolateral edge of the postorbital process may be longitudinally aligned with the lateral tip of the preorbital process or may fail to reach its lateral extension (0,1) ( +Fig. 1A +). In + +Plesiotrygon + +and + +Paratrygon + +the postorbital process extends laterally beyond the lateral edge of the preorbital process (2) ( +Fig. 1B +, +3B +). + + +27. +Posterior margin of postorbital process; shape: (0) slightly convex; (1) straight. + + +In + +Styracura + +(outgroup) the posterior margin of the postorbital process is slightly convex near its distal portion (0) ( +Fig. 1C +). In + +Plesiotrygon + +, + +Paratrygon + +, and + +Heliotrygon + +the posterior margin of the postorbital process is straight (1) ( +Figs 1B +, +3 +). In + +Potamotrygon + +this character is polymorphic and can be slightly convex or, as in most of the species here observed, straight (0,1) ( +Fig. 1A +). + + +28. +Postorbital process; angle in relation to the otic wall: (0) 120°; (1) 90°. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the angle of the postorbital process in relation to the otic wall is nearly 120° (0) ( +Figs 1 +, +3B +). In + +Heliotrygon + +the angle of the postorbital process in relation to the otic wall is close to 90° (1) ( +Fig. 3A +). + + +Orbital region + + +29. +Foramen for preorbital canal; number: (0) two; (1) one. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +there are two foramina for the preorbital canal (0) ( +Figs 5 +, +6B +). In + +Heliotrygon + +there is a single foramen for the preorbital canal(1) ( +Fig. 6A +; Supporting Information, File S6). + + +30. +Anterior foramen for preorbital canal; position: (0) anteroventral to the preorbital process; (1) posteroventral to the preorbital process. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, and + +Paratrygon + +the anterior foramen for preorbital canal opens ventrally, anterior to the base of the preorbital process (0) ( +Figs 5A, C +, +6B +). In + +Plesiotrygon + +the anterior foramen for preorbital canal opens ventrally, posterior to the base of the preorbital process (1) ( +Fig 5B +; Supporting Information, File S3). + +Heliotrygon + +has a single branch of the foramen for preorbital canal and is coded as inapplicable. + + +31. +Posterior foramen for preorbital canal; position: (0) posterior to the preorbital process; (1) posteroventral to the preorbital process. + + +In + +Styracura + +(outgroup) the posterior foramen for preorbital canal is posterior to the preorbital process (0) ( +Fig. 5C +). In + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the posterior foramen for preorbital canal is posteroventral to the preorbital process (1) ( +Figs 5A, B +, +6B +). + +Heliotrygon + +lacks this foramen and is coded as inapplicable ( +Fig. 6A +). + + +32. +Anterior cerebral vein foramen; position: (0) anterior, longitudinally aligned with the anterodorsal margin of the optic nerve foramen; (1) anterodorsal to the optic nerve foramen. + + +In + +Styracura + +(outgroup), + +Heliotrygon + +, + +Paratrygon + +, and + +Potamotrygon + +, the anterior cerebral vein foramen is anterior and at level with the dorsal margin of the optic nerve foramen (0) ( +Figs 5A, C +, +6 +). In + +Plesiotrygon + +the anterior cerebral vein foramen is anterodorsal in relation to the optic nerve foramen (1) ( +Fig. 5B +). + + +33. +Trochlear nerve foramen; position: (0) dorsal to the midportion of the optic nerve foramen; (1) dorsal to the posterior margin of the optic nerve foramen. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Plesiotrygon + +, and + +Heliotrygon + +the trochlear nerve foramen is dorsal to midportion of the optic nerve foramen (0) ( +Figs 5 +, +6A +). In + +Paratrygon + +the oculomotor nerve foramen is dorsal and closer to the posterior margin of the optic nerve foramen (1) ( +Fig. 6B +). + + +34. +Trochlear nerve foramen; distance from the optic nerve foramen: (0) less than half the height of the optic nerve foramen; (1) half the height of the optic nerve foramen; (2) the same height as the optic nerve foramen [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the distance of the oculomotor nerve foramen in relation to the optic nerve foramen is less than half the height of the optic nerve foramen (0) ( +Figs 5C +, +6B +). In + +Heliotrygon + +the distance of the oculomotor nerve foramen in relation to the optic nerve foramen is half the height of the optic nerve foramen (1) ( +Fig. 6A +). In + +Potamotrygon + +the distance of the oculomotor nerve foramen in relation to the optic nerve foramen can be less than or half the height of the optic nerve foramen (0,1) ( +Fig. 5A +). In + +Plesiotrygon + +the distance between the oculomotor nerve foramen and the optic nerve foramen is equal to the height of the optic nerve foramen (2) ( +Fig. 5B +). + + +35. +Efferent spiracular artery foramen; position: (0) anteroventral to the eye stalk; (1) ventral to the eye stalk. + + +In + +Styracura + +(outgroup) and + +Potamotrygon + +the efferent spiracular artery foramen is positioned anteroventrally to the eye stalk, in the space between it and the optic nerve foramen (0) ( +Figs 5A, C +). In + +Plesiotrygon + +, + +Paratrygon + +, and + +Heliotrygon + +the efferent spiracular artery foramen is located ventral to the eye stalk (1) ( +Figs 5B +, +6 +). + + +36. +Eye stalk; morphology: (0) rounded; (1) oval. + + +In + +Styracura + +(outgroup), + +Plesiotrygon + +, and + +Paratrygon + +the eye stalk is rounded (0) ( +Figs 5B, C +, +6A +). In + +Heliotrygon + +the eye stalk is oval (1) ( +Fig. 6A +). In + +Potamotrygon + +both states are present, with species bearing a rounded or oval eye stalk (0,1) ( +Fig. 5A +). + + +37. +Internal carotid artery foramen; position: (0) ventrolateral; (1) ventral. + + +In + +Styracura + +(outgroup), + +Plesiotrygon + +, and + +Heliotrygon + +the internal carotid foramina are positioned ventrolaterally on the neurocranium at the limit between the ventral face and the lateral face of the neurocranium (0) ( +Figs 5 +, +6A +). In + +Paratrygon + +the internal carotid foramina are ventrally positioned, occupying only the basicranium (1) ( +Fig. 4B +). This character is polymorphic for + +Potamotrygon + +, with species presenting the internal carotid foramina positioned ventrally or ventrolaterally (0,1) ( +Fig. 5A +). + + +38. +Oculomotor nerve foramen; position: (0) dorsal to the eye stalk; (1) anterodorsal to the eye stalk. + + +In + +Styracura + +(outgroup), +Plesiorygon +, and + +Paratrygon + +the oculomotor nerve foramen is immediately dorsal to the eye stalk (0) ( +Figs 5B, C +, +6B +). In + +Heliotrygon + +the oculomotor nerve foramen is anterodorsal in relation to the eye stalk (1) ( +Fig. 6A +). In + +Potamotrygon + +this character is polymorphic and the oculomotor nerve foramen can be anterodorsal or dorsal in relation to the eye stalk (0,1) ( +Fig. 5A +). + + +39. +Postorbital wall; anterolateral projection: (0) not anterolaterally extended; (1) extends anterolaterally, partially covering the orbital fissure; (2) extends anterolaterally over the orbital fissure, covering it entirely [multistate ordered]. + + +In + +Styracura + +(outgroup), + +Paratrygon + +, and + +Plesiotrygon + +, the postorbital wall of the neurocranium is not anterolaterally expanded, leaving the orbital fissure uncovered and completely visible laterally (0) ( +Figs 5B, C +, +6B +). In + +Heliotrygon + +, the postorbital wall extends anterolaterally covering the orbital fissure completely (2) ( +Fig. 6A +). In + +Potamotrygon + +this character is polymorphic. The majority of the species have states 1 or 2, and + +Potamotrygon schroederi + +is the only species in which the orbital fissure is completely exposed, and coded as 0 (0,1,2) ( +Fig. 5A +). + + +40. +Orbital fissure; proportion: (0) one-third the diameter of the optic nerve foramen; (1) half the diameter of the optic nerve foramen; (2) the same size of the optic nerve foramen [multistate ordered]. + + +In + +Styracura + +(outgroup) the orbital fissure has half the size of the optic nerve foramen (1) ( +Fig. 5C +). In + +Heliotrygon + +, + +Paratrygon + +, and + +Plesiotrygon + +the orbital fissure has the same size of the optic nerve foramen (2) ( +Figs 5B +, +6 +). In + +Potamotrygon + +this character is polymorphic and the orbital fissure may have one-third, half, or the same size of the optic nerve foramen (0,1,2) ( +Fig. 5A +). + + +Otic region + + +41. +Otic region; length: (0) shorter than the proximal portion of the postorbital process; (1) 1.5 times longer than the proximal portion of the postorbital process; (2) 3 times the proximal portion of the postorbital process [multistate ordered]. + + +In + +Styracura + +(outgroup) the length of the otic region is shorter than the proximal portion of the postorbital process (0) ( +Fig. 1C +). In + +Potamotrygon + +, + +Plesiotrygon + +, and + +Paratrygon + +the length of the otic region is 1.5 times the proximal portion of the postorbital process (1) ( +Figs 1A, B +, +3B +). In + +Heliotrygon + +the length of the optic region has 3 times the proximal portion of the postorbital process (2) ( +Fig. 3A +). + + +42. +Perilymphatic foramina; position in relation to the endolymphatic foramina: (0) posterior; (1) posterolateral; (2) posteromedial. + + +In + +Styracura + +(outgroup), +Plesitorygon +, and + +Paratrygon + +the perilymphatic foramina are posterior and longitudinally aligned with the endolymphatic foramina (0) ( +Figs 1B, C +, +3B +). In + +Heliotrygon + +the perilymphatic foramina are posterolateral in relation to the endolymphatic foramina (1) ( +Fig. 3A +). In the majority of + +Potamotrygon +species + +the perilymphatic foramina are posteromedial in relation to the endolymphatic foramina, and only in some of them the perilymphatic foramina are posterior (0,2) ( +Fig. 1A +). + + +43. +Perilymphatic foramen; size: (0) same diameter as the endolymphatic foramen. (1) 2 times the size of the endolymphatic foramen; (2) 3 times the size of the endolymphatic foramen [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the perilymphatic foramen has the same diameter as the endolymphatic foramen (0) ( +Figs 1C +, +3B +). In + +Plesiotrygon + +the perilymphatic foramen’s diameter is twice the diameter of the endolymphatic foramen (1) ( +Fig. 1B +). In + +Potamotrygon + +this character is polymorphic and the perilymphatic foramen may have the same size or be twice the size of the endolymphatic foramen (0,1) ( +Fig. 1A +). In + +Heliotrygon + +the perylimphatic foramen’s diameter is three times that of the endolymphatic foramen (2) ( +Fig. 3A +). + + +44. +Lateral commissure; shape: (0) medially septate on its anterior margin; (1) not septate medially. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the lateral commissure bears a chondrified median septum and two openings anteriorly (0) ( +Fig. 5B, C +). In + +Potamotrygon + +, + +Paratrygon + +, and + +Heliotrygon + +the lateral commissure is not septate, forming a simple arch over the foramen for the hyomandibular branch of the facial nerve (1) ( +Figs 5A +, +6 +). + + +45. +Hyomandibular facet; shape: (0) its anterior region wider than its posterior region; (1) same width throughout its extension. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the hyomandibular facet is wider at its anterior region, resulting in a nearly ovalshaped structure (0) ( +Figs 5B, C +). In + +Paratrygon + +and + +Heliotrygon + +the hyomandibular facet has the same width anteroposteriorly (1) ( +Fig. 6 +). Both states can be found in species of + +Potamotrygon + +(0,1) ( +Fig. 5A +). + + +46. +Hyomandibular facet; ventral margin: (0) convex; (1) straight; (2) concave. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the ventral margin of the hyomandibular facet is convex (0) ( +Fig. 5B, C +). In + +Paratrygon + +the ventral margin of the hyomandibular facet is straight (1) ( +Fig. 6B +). In + +Heliotrygon + +the ventral margin of the hyomandibular facet is medially concave (2) ( +Fig. 6A +). In + +Potamotrygon + +this character is polymorphic and the ventral margin of the hyomandibular facet can be convex or straight (0,1) ( +Fig. 5A +). + + +47. +Jugal arch: (0) absent; (1) present. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, + +Paratrygon + +, and + +Heliotrygon + +the neurocranium lacks a jugal arch (0) ( +Figs 5A, C +, +6 +). In + +Plesiotrygon + +the jugal arch is present and posterior to the hyomandibular facet (1) ( +Fig. 5B +). However, it’s important to highlight that it is unclear if the jugal arch may be present in the other genera of +Potamotrygoninae +as an unchondrified arch considering that this fragile structure may be damaged during dissection. + + +Occipital region + + +48. +Sphenopterotic ridge; development: (0) as long as the lateral extension of the supraotic ridge; (1) shorter than the lateral extension of the supraotic ridge. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the dorsal projection of the sphenopterotic ridge is as long as the lateral extension of the supraotic ridge (0) ( +Fig. 9B, C +). In + +Heliotrygon + +and + +Paratrygon + +the dorsal projection of the sphenopterotic ridge is shorter than the lateral extension of the supraotic ridge (1) ( +Fig. 10 +). In + +Potamotrygon + +the sphenopterotic ridge may be as long as or shorter than the lateral extension of the supraotic ridge (0,1) ( +Fig. 9A +). + + +49. +Vagus nerve foramen; diameter: (0) one-third the width of the foramen magnum; (1) one-fifth the width of the foramen magnum; (2) one-fourteenth the width of the foramen magnum [multistate ordered]. + + +In + +Styracura + +(outgroup) the vagus nerve foramen diameter is one-third the width of the foramen magnum (0) ( +Fig. 9C +). In + +Paratrygon + +and + +Plesiotrygon + +the vagus nerve foramen diameter is one-fifth the width of the foramen magnum (1) ( +Figs 9B +, +10B +). In + +Potamotrygon + +the vagus nerve foramen may have a diameter equal to one-third or one-fifth the width of the foramen magnum (0,1) ( +Fig. 9A +). In + +Heliotrygon + +the diameter of the vagus nerve foramen is one-fourteenth of the width of the foramen magnum (2) ( +Fig. 10A +). + + +50. +Vagus nerve foramen; dorsal margin: (0) closer to the dorsal margin of the foramen magnum; (1) at the midlength of the foramen magnum. + + +In + +Styracura + +(outgroup) the dorsal margin of the vagus nerve foramen is closer to the dorsal margin of the foramen magnum (0) ( +Fig. 9C +). In + +Paratrygon + +, + +Plesiotrygon + +, and + +Heliotrygon + +the dorsal margin of the vagus nerve foramen does not reach the same level as the dorsal margin of the foramen magnum (1) ( +Figs 9B +, +10 +). In + +Potamotrygon + +this character is polymorphic (0,1) ( +Fig. 9A +). + + +51. +Foramen of the lateralis branch of the vagus nerve; position: (0) dorsolateral to the vagus nerve foramen; (1) dorsal to the vagus nerve foramen. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the foramen of the lateralis branch of the vagus nerve is dorsolateral to the vagus nerve foramen (0) ( +Figs 9C +, +10B +). In + +Heliotrygon + +and + +Plesiotrygon + +the foramen of the lateralis branch of the vagus nerve is immediately dorsal to the vagus nerve foramen (1) ( +Figs 9B +, +10A +). In + +Potamotrygon + +most species have the foramen of the lateralis branch of the vagus nerve dorsal to the vagus nerve foramen and few species have it positioned dorsolateral and farther from the vagus nerve foramen (0,1) ( +Fig. 9A +). + + +52. +Articular surface; width: (0) one-third the width of the occipital condyle; (1) half the width of the occipital condyle; (2) two-thirds the width of the occipital condyle [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Paratrygon + +the width of the articular surface is half the width of the occipital condyle (1) ( +Figs 9C +, +10B +). In + +Plesiotrygon + +the articular surface has one-third the width of the occipital condyle (0) ( +Fig. 9B +). In + +Potamotrygon + +the articular surface may have half or one-third the width of the occipital condyle (0,1) ( +Fig. 9A +). In + +Heliotrygon + +the articular surface is wider, with two-thirds the width of the occipital condyle (2) ( +Fig. 10A +). + + +53. +Foramen magnum; shape: (0) taller than wider; (1) wider than taller. + + +In + +Styracura + +(outgroup) the opening of the foramen magnum is oval and taller than wider (0) ( +Fig. 9C +). In + +Plesiotrygon + +, + +Heliotrygon + +, and + +Paratrygon + +the foramen magnum is also ovoid but is wider than taller (1) ( +Figs 9B +, +10 +). In + +Potamotrygon + +this character is polymorphic, but in most of the species the foramen magnum is wider than taller (0,1) ( +Fig. 9A +). + + +54. +Occipital condyle; ventral margin, shape: (0) straight; (1) concave. + + +In + +Styracura + +(outgroup), + +Heliotrygon + +, and + +Paratrygon + +the occipital condyles are straight and devoid of a concavity on their ventral margin (0) ( +Figs 9C +, +10 +). In + +Plesiotrygon + +the occipital condyles are arched on their mid portion and have a clear concavity on their ventral margin (1) ( +Fig. 9B +). In + +Potamotrygon + +the occipital condyles may be straight or arched (0,1) ( +Fig. 10A +). + + +55. +Occipital condyles; orientation: (0) horizontal; (1) medially inclined, with its lateral portion dorsal to its medial portion; (2) laterally inclined, with its medial portion dorsal to its lateral portion. + + +In + +Styracura + +(outgroup) and + +Potamotrygon + +the occipital condyles are horizontally oriented (0) ( +Fig. 9A, C +). In + +Paratrygon + +the occipital condyles are medially oblique, with their lateral portions dorsal to their medial portions (1) ( +Fig. 10B +). In + +Heliotrygon + +and + +Plesiotrygon + +the condyles are laterally obliquely, with their medial portions dorsal in relation to their lateral portions (2) ( +Fig. 10A +). + + +56. +Occipital condyle; posterior extension in relation to the basicranium: (0) one-third the length of the hyomandibular facet; (1) two-thirds the length of the hyomandibular facet. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, and + +Plesiotrygon + +the posterior extension of the occipital condyle corresponds to one-third the length of hyomandibular facet (0) ( +Fig. 5 +). In + +Paratrygon + +and + +Heliotrygon + +the posterior extension of the occipital condyle corresponds to two-thirds the length of the hyomandibular facet (1) ( +Fig. 6 +). + + +57. +Occipital condyles; lateral extension: (0) medial to the lateral surface of otic capsules; (1) at level with the lateral surface of otic capsules. + + +In + +Styracura + +(outgroup), + +Potamotrygon + +, and + +Plesiotrygon + +the lateral extension of the occipital condyles does not reach the lateral surface of the otic capsules (0) ( +Figs 2 +, +9 +). In + +Heliotrygon + +and + +Paratrygon + +the lateral extension of the occipital condyles is aligned with the lateral surface of the otic capsules (1) ( +Figs 4 +, +10 +). + + +58. +Glossopharyngeal nerve foramen; position on the occipital region: (0) ventrolateral; (1) posteroventral. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the glossopharyngeal nerve foramen is situated ventrolaterally on the occipital region, and visible on a posterior oblique view (0) ( +Fig. 5 +, +9 +). In + +Heliotrygon + +and + +Paratrygon + +the glossopharyngeal nerve foramen is placed posteroventrally on the otic region and is only visible in lateral view, being immediately posterior to the hyomandibular facet (1) ( +Fig. 6 +). In species of + +Potamotrygon + +the glossopharyngeal nerve foramen may be seen on posterior oblique view or only laterally (0, 1) ( +Fig. 9A +). + + +59. +Otic region; lateral wall: (0) concave; (1) convex. + + +In + +Styracura + +(outgroup), + +Plesiotrygon + +, and + +Paratrygon + +the lateral wall of the otic region is concave (0) ( +Fig. 9B, C +, +10B +). In + +Heliotrygon + +the lateral wall of the otic region is convex (1) ( +Fig. 10A +). In + +Potamotrygon + +the lateral wall of the otic region is concave in most of the species, except for + +Potamotrygon limai + +(0, 1) ( +Fig. 9A +). + + +60. +Supraotic ridge; lateral projection: (0) surpassing the lateral limit of the hyomandibular facet; (1) reaching the lateral limit of the hyomandibular facet; (2) failing to reach the lateral limit of the hyomandibular facet [multistate ordered]. + + +In + +Styracura + +(outgroup) and + +Plesiotrygon + +the lateral extension of the supraotic ridge is similar to the lateral extension of the hyomandibular facet (1) ( +Fig. 9B, C +). In + +Heliotrygon + +and + +Paratrygon + +the lateral extension of the supraotic ridge is shorter than that of the hyomandibular facet (2) ( +Fig. 10 +). In + +Potamotrygon + +this character is polymorphic and the lateral projection of the supraotic ridge may surpass, reach or fail to reach the lateral limit of the hyomandibular facet (0, 1, 2) ( +Fig. 9A +). + + +Phylogenetic analyses + + +A matrix with five terminal taxa and 60 characters from the neurocranium yielded a single most parsimonious tree with 79 steps, consistency index (CI) of 0.899, and retention index (RI) of 0.636 ( +Figs 11 +and +12 +). The characters above correspond to those from the matrix (Supporting Information, File S8). The resulting tree supports the monophyly of the subfamily +Potamotrygoninae +, and indicates that + +Potamotrygon + +and + +Plesiotrygon + +are successive sister-groups to a clade formed by + +Heliotrygon + +and + +Paratrygon + +( +Figs 11 +, +12 +). + + + + \ No newline at end of file