Ischnocnema henselii

Vera Candioti, Florencia, Goldberg, Javier, Akmentins, Mauricio S., Nogueira Costa, Paulo, Goulart Taucce, Pedro Paulo & Pombal, José, 2020, Skeleton in the closet: hidden diversity in patterns of cranial and postcranial ontogeny in Neotropical direct-developing frogs (Anura: Brachycephaloidea), Organisms Diversity & Evolution (New York, N. Y.) 20 (4), pp. 763-783 : 772

Ischnocnema henselii

Cranial ontogeny At TS11–12, the chondrocranium is slightly more advanced than those of Oreobates and Haddadus ( Fig. 10a, b ). Main differences are the more chondrified orbital cartilages, the almost perpendicular palatoquadrates, and in the hyobranchial skeleton, the differentiated anterior processes and completely reduced ceratobranchials. Nonossified anlagen of the angulosplenials and squamosals are outlined at this stage. At TS13, these ossified elements, plus the dentaries, maxillae, parasphenoid, and small premaxillae, are present in serial sections. Frontoparietals and pterygoids ossify at TS14. Finally, hatched specimens of I. henselii ( Fig. 11 ) show almost all adult bones ossified, including the neopalatines (a difference regarding Haddadus ), plus the mentomeckelians, quadratojugals, vomers, and hyoid posterior processes (differences regarding Oreobates ); only the sphenethmoid differentiates at some point during juvenile stages.

Postcranial ontogeny Postcranial development is also faster than in the two previous species ( Figs. 10c–g and 12 ). Fundamental differences with hatched specimens of the other species include a coccyx well developed although not fully ossified at hatching, a cartilaginous sternum already evident, and in the limbs, most bony elements, including the T-shaped terminal phalanges, differentiated; only the carpal bones remain cartilaginous. A single proximal prepollical element is discernible. Two prehallical cartilaginous elements are differentiated at hatching.

Figures

Fig. 10 Skeletal morphology of Ischnocnema henselii at TS11–12. a Skull dorsal and lateral views. b Hyobranchial apparatus, ventral view. Inset: detail of the palatoquadrate cartilage, showing a primordium of the squamosal. c Vertebral column, dorsal view. d Pectoral girdle, ventral view. e Pelvic girdle, lateral view. f Forelimb, dorsal view. g Hind limb,

Fig. 11 Cranial skeleton of Ischnocnema henselii at hatching. Dorsal, ventral, lateral, and frontal views. Abbreviations: as, angulosplenial; d, dentary; eo, exoccipital; fp, frontoparietal; m, maxilla; n, nasal; np, neopalatine; pm, premaxilla; po, prootic; ps, parasphenoid; pt, pterygoid; qj, quadratojugal; sm, septomaxilla; sq, squamosal; v, vomer. Scale bar = 1 mm

Fig. 12 Postcranial skeleton of Ischnocnema henselii at hatching. a Vertebral column and pelvic girdle, dorsal view. b Pectoral girdle, ventral view. c Forelimb, dorsal view. d Hind limb, dorsal view. The inset shows detail of the medial region of articulated pectoral girdle,