Oreobates barituensis
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publication ID |
https://doi.org/ 10.1007/s13127-020-00467-8 |
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persistent identifier |
https://treatment.plazi.org/id/5529E94F-3047-F67E-B30A-5A63FB0F2720 |
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treatment provided by |
Felipe |
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scientific name |
Oreobates barituensis |
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Oreobates barituensis View in CoL
Cranial ontogeny At TS10, cranial trabeculae are visible as rod-like cartilages located ventrolateral to the brain. They are united posteriorly by the future basal plate, and they approach one another rostrally. In the olfactory region, only the solum, tectum, and septum nasi are developed. A thin pila antotica ascends dorsally from each trabecula; the pila metoptica begins to develop as a small bump rostral to the pila antotica. The trabecular horns and suprarostral cartilages never form. The otic capsules are large (44% of the cranium length) and rounded. The palatoquadrate is very thin, weakly Alcianophilic, not connected to the neurocranium, and orient- ed at an angle of 30° relative to its anteroposterior axis. The lower jaw has an inverted U-shape. The medial region corresponds to the infrarostral cartilages, which are medially fused through a thick symphysis; Meckel’ s cartilages are thin, curved caudally, and reach the plane of the pila metoptica; they are fully fused to the infrarostral cartilages forming a single rod of cartilage. In the hyobranchial skeleton, the ceratohyals already resemble the hyale of metamorphic stages; they are long, with similar width along their entire length, and curve posteriorly; the anterior processes are short and stout. Unfortunately, Alcian blue staining was too weak for us to resolve ceratobranchial configuration.
At TS11–12 ( Fig. 1a View Fig ), the skull is completely cartilaginous. The developing nasal capsules include inferior prenasal cartilages, planum antorbitale, antorbital process, and planum triangulare. The pila antotica and pila metoptica extend dorsally and are connected to each other through cartilaginous bridges. The orbital cartilage begins to develop completing the lateral walls of the cranium. In the otic region, an operculum is already developed and a thin tectum synoticum projects
Developmental stages follow Townsend and Stewart (1985) CFBH, amphibian collection of Célio F. B. Haddad, Departamento de Zoologia, Instituto de Biociências, Universidade Estadual Paulista, Campus de Rio Claro, São Paulo; FML, herpetological collection of Fundación Miguel Lillo; IBIGEO, Instituto de Bio y Geociencias del NOA, CONICET; MSA, collection of Mauricio S. Akmentins; MNRJ, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro
* The same cleared and stained specimen was later sectioned medially from the dorsal aspect of each otic capsule. The palatoquadrate cartilage is short and oriented at an angle of 45° relative to the anteroposterior axis of the neurocranium; it is not attached to the neurocranium. The articular process is stout and articulates with Meckel’ s cartilage, whereas the posterior extreme is thin and does not reach the otic capsule. The pterygoid process is stout and long and directed rostrally reaching almost the anterior margin of the orbit; caudal to the pterygoid process, the palatoquadrate becomes slightly taller, likely representing a much reduced muscular process. In the lower jaw, Meckel’ s cartilages have grown longer to reach the pila antotica. The hyobranchial skeleton ( Fig. 1b View Fig ) has a weak hypobranchial plate; the hyale are curved and have more prominent anterior processes. Ceratobranchials I are still distinct, long and thin, and ceratobranchials II are fully reduced to small processes on the lateral margins of the hypobranchial plate; posterior processes are thin, short, and divergent. No ossifications are evident in whole-mount preparations, but histological sections reveal angulosplenials developing on the ventral aspect of Meckel’ s cartilage.
At TS13, the palatoquadrate is visible as a thin, cartilaginous structure oriented at an angle of about 55° relative to the anteroposterior axis of the neurocranium. The dorsal extreme is the otic process that approaches the anterolateral region of the otic capsule; the ventral extreme is the articular process that articulates with the posterior edge of Meckel’ s cartilage. Maxillary and pterygoid processes join at this stage. In the hyobranchial apparatus, the ceratobranchials I are fully reduced, and small anterolateral processes remain instead. Ossifications of the angulosplenials and squamosals are present, and a slight coloration indicates the beginning of differentiation of the maxillae in the upper jaw.
At TS14, the cartilaginous skeleton undergoes further changes in the nasal region. Alary, oblique, superior and inferior prenasal cartilages, subnasal crest, lateral commissures, and the laminae superior and inferior (which delimit principal, medial, and inferior nasal cavities) are differentiated ( Fig. 2 View Fig ). Posteriorly, a thin planum antorbitale is visible, with a long, ventrally oriented antorbital process; a short and weak maxillary anterior process; and a long, posterior pterygoid process. Premaxillae and small dentaries ossify. Meckel’ s cartilages become thinner and longer and extend to almost the posterior end of the otic capsules. The palatoquadrate cartilages acquire a perpendicular arrangement regarding the neurocranium axis.
At TS15 ( Fig. 3 View Fig ), the cranium is still almost completely cartilaginous. In the cranial roof, the taenia tecti transversalis grows from the taenia tecti marginales, and a small taenia tecti medialis develops from the anterior margin of the tectum synoticum ( Fig. 3a View Fig ). The jaw suspension is located ventral and anterior to the otic capsules. The dorsal otic process is formed, and histological sections of a hatched specimen show an additional, stout pseudobasal process. The region corresponding to infrarostral cartilages is very small and weak, and Meckel’ s cartilages are stout. The hyobranchial skeleton has almost the adult shape ( Fig. 3b View Fig ). The long anterior processes of the hyalia run parallel in rostral direction; the posterior extreme of each hyale is dorsally curved to reach close contact with the otic capsule. The hyoid plate is quadrangular and weakly chondrified; on its lateral margins, the antero- and posterolateral processes are outlined. Caudally, the posteromedial processes are long and divergent. Discrete ossifications at this stage are the premaxillae, maxillae, septomaxillae, and nasals ( Fig. 3c View Fig ), angulosplenials, dentaries, very thin pterygoids dorsal to the caudal edge of pterygoid processes ( Fig. 3d View Fig ), and squamosals with stout ventral and otic rami, and a small zygomatic ramus; frontoparietals are present as narrow slivers dorsal to the orbital cartilages. Parasphenoid and prootics are slightly outlined on the ventral aspect of the cranium floor and the anterior surface of the otic capsules, respectively.
Postcranial ontogeny At TS10, the cartilaginous precursors of all eight presacral and the sacral vertebrae are present as paired condensations that develop dorsolaterally to the notochord. Anterior vertebrae appear more defined with atlas condensations wider than those of the other vertebrae. A small postsacral vertebra also develops at this stage, evident as a pair of condensations. By TS12, the neural arches primordia remain as paired condensations, although larger ( Fig. 1c View Fig ). Vertebrae II and III exhibit incipient, short transverse processes. Postsacral 2 appears as a pair of neural arch pedicels posterior to postsacral 1. Next, the transverse process of vertebra IV develops. All vertebrae present incipient postzygapophyses. Ossification begins with two bony centers on the cartilaginous centrum of the atlas. Ossification centers also occur in the dorsal half of the atlas pedicels and in the pedicels of all presacral vertebrae underneath transverse processes. At TS13, the hypochord appears as a small cartilaginous bar at the level of the neural arches of the first postsacral vertebra, parallel and ventral to the notochord. At TS14–15, the neural arch laminae of all presacral vertebrae are expanded medially ( Fig. 4a). Vertebrae II–VIII have well-defined, although small, transverse processes (III> II> IV> V = VI = VII = VIII). All presacral vertebrae bear small pre- (except the atlas) and postzygapophyses; the postzygapophyses of presacral vertebrae I–VI seem to articulate with the prezygapophyses. The sacrum bears a pair of small rounded diapophyses. At hatching, both counterparts of the postsacral vertebra 1 remain separated and each side has an anterior cotyle, whereas both halves of postsacral vertebra 2 are well differentiated. An additional cartilaginous growth of the posterior margin of postsacral vertebra 2 suggests the development of a third postsacral vertebra. Boundaries between the neural arch pedicels of postsacral vertebrae 1 and 2 and between those of postsacral vertebrae 2 and 3 are indicated by the presence of large foramina. Therefore, at hatching, both counterparts of the coccyx are present. Ossification of the hypochord is slightly noticeable at this stage.
In the pectoral girdle, at TS10, each half is composed of two cartilaginous primordia that correspond to the scapula and the coracoid. By TS12, the procoracoid cartilage is differentiated and it fuses with the scapula and coracoid to define the glenoid fossa ( Fig. 1d View Fig ). The suprascapular cartilage appears as a flat sheath next to the scapula. By TS13, the epicoracoid is fully formed forming the cartilaginous bridge between the coracoid and the procoracoid. The endochondral ossification of the coracoid and scapula occurs earlier than the dermal ossification of the clavicle and the cleithrum ( Fig. 4b). Mineralization of the suprascapulae is evident from TS14. Sternum elements are not differentiated in prehatching stages.
Forelimb development is depicted in Figs. 1f View Fig and 4d and summarized in Fig. 5a View Fig . At TS10, the first elements to appear are those related to the primary axis, i.e., the ulnare, distal cartilage; is, ischium; ma, manus; mc, Meckel’ s cartilage; mt, metatarsalia; nc, nasal capsule; oc, otic capsule; oca, orbital cartilage; p, phalanges; pc, procoracoid; pp, pterygoid process; pq, palatoquadrate; prs, presacral vertebrae; pts, postsacral vertebra; pu, pubis; r, radius; s, sacrum; sc, scapula; ssc, suprascapula; tf, tibia–fibula; ti, tibiale; ts, tectum synoticum; u, ulna. The asterisk shows the remaining ceratobranchial I in the hyobranchial skeleton. Scale bars = 1 mm
carpale 5-4, and finger IV. The preaxial process of the ulnare (interpreted as the cartilage intermedium by Fabrezi and Barg 2001) is present at this stage. The radiale and the element Y are formed by the secondary fusions of two embryonic condensations each. The last fusion of carpal elements (distal carpale 5-4 plus distal carpale 3) begins at TS12. An unidentified condensation appears postaxially and close to the distal end of the ulna. Fusion of radius and ulna begins at their proximal ends by TS13, simultaneously with the fusion of condensations forming the element Y and the radiale. By TS14, the proximal element of prepollex and the terminal phalanges of fingers III–V differentiate. The ossification begins after TS10 and occurs proximodistally and preaxially. Before hatching, diaphyses of all long bones (humerus, radioulna, metacarpalia, and phalanges) are ossified.
Regarding the pelvic girdle, at TS10, the first elements to appear are the ilia and the pubes as two independent cartilaginous condensations on each side of the girdle, at the level of the first postsacral vertebra. As development progresses, ilia elongate anteriorly. Condensations of the ischia appear and migrate toward each other and fuse to form, together with the medially attached pubes, the acetabula. As ilia elongate, ossification begins from a center near the midpoint of their shafts by TS12 ( Fig. 1e View Fig ). Before hatching, ossification of ilial shafts spreads anteriorly and posteriorly reaching the acetabula, while the ischia show the first signs of ossification in their posterior margins. Ilia attach to the developing sacral diapophyses by thin ligaments.
Hind limb development is slightly faster than that of the forelimbs ( Figs. 1g View Fig , 4e, and 5b View Fig ). At TS10, postaxial dominance of the primary axis is evident with the early differentiation of the proximal phalanx of toe IV. By TS12, three condensations are distinct in the tarsus, distal to the enlarged proximal tarsalia (fibulare and tibiale): the distal tarsale 3-2 (primary fusion), distal tarsal 1, and two condensations of the element Y. This latter acquires its definitive configuration at TS13, via the fusion of both primary independent condensations. Concomitant with this, the proximal element of the prehallux arises as a single condensation. At TS14, terminal phalanges are differentiated. Ossification begins before TS12,
Abbreviations: ac, alary cartilage; ipc, inferior prenasal cartilage; li, lamina inferior; ls, lamina superior; map, maxillary anterior process; oc, oblique cartilage; pt, planum terminale; sc, subnasal crest; sn, septum nasi; spc, superior prenasal cartilage; tn, tectum nasi. Scale bars = 1 mm (a, b) and 0.1 mm (c)
earlier than the ossification in the manus, and it takes place in a proximodistal and postaxial–preaxial direction as well. All diaphyses of metatarsals and phalanges are ossified before hatching. Distal tarsal bones remain cartilaginous at hatching, and the distal prehallical element is still cartilaginous in adult specimens. The T-shape of terminal phalanges of toes and fingers is acquired after hatching.
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