Hyoid Skeleton, Its Related Muscles, and Morphological Novelties in the Frog Lepidobatrachus (Anura, Ceratophryidae)

Abstract

Many traits of the skull of ceratophryines are related to the capture of large prey independently of aquatic or terrestrial feeding. Herein, detailed descriptions of the development of hyoid skeleton and the anatomy of muscles responsible for hyoid and tongue movements in Lepidobatrachus laevis and L. llanensis are provided and compared with those of other neobatrachians. The aquatic Lepidobatrachus has special features in its hyoid skeleton that integrates a set of derived features convergent with the conditions observed in non-neobatrachian anurans and morphological novelties (e.g., dorsal dermal hyoid ossification) that deviate from the generalized pattern found in most frogs. Further, reduction of fibers of muscles of buccal floor, reduction or loss of hyoid muscles (m. geniohyoideus rama lateralis, anterior pair of m. petrohyoideus posteriores), small tongue, and simplified tongue muscles are also morphological deviations from the pattern of terrestrial ceratophryines, and other aquatic ceratophryids (e.g., Telmatobius) that seem to be related to feeding underwater. The historical derived features shared with Chacophrys and Ceratophrys involved in megalophagy are conserved in Lepidobatrachus and morphological changes in the hyoglossal apparatus define a unique functional complex among anurans.

The ontogeny of the olfactory system in ceratophryid frogs (Anura, Ceratophryidae)

“…Our results on the adult morphology of the olfactory system support previous work (Fabrezi, ; Fabrezi & Lobo, ; Fabrezi & Quinzio, ; Fabrezi et al, ; Quinzio &Fabrezi, 2012, 2014) showing that Chacophrys and Ceratophrys show an ancestral typical terrestrial morphology, while in Lepidobatrachus there is a trend within the genus of morphological change related to a derived aquatic life, with L. asper the least aquatic and L. laevis the most aquatic (Figure ). Thus, we added data, from the olfactory system, to the derived morphology of adult L. laevis and its evolutionary trend to a secondarily aquatic life.…”

“…laevis are uniquely integrated with other derived morphological traits defining a distinctive body plan, both within the group and with respect to other Neobatrachia. The early ontogenetic acquisition of many of these features, reducing the morphological differences between larval and adult body plans, seems to be correlated with the absence of the aquatic to terrestrial shift in these frogs (Fabrezi, ; Fabrezi & Lobo, ; Fabrezi & Quinzio, ; Fabrezi et al, ; Quinzio & Fabrezi, ).…”

“…All three genera have exostotic (sculptured and hyperosified) skulls (Fabrezi, ; Wild, ) and keratinized metatarsal tubercles adapted to digging, and there are bony dorsal shields in species of both Ceratophrys and Lepidobatrachus (Fabrezi, ; Lynch, ; Quinzio & Fabrezi, ). In Lepidobatrachus , these features are integrated with others that appear related to an aquatic life: some examples include the complete webbing of the feet, a hyoglossal apparatus and associated musculature modified for feeding underwater (Fabrezi & Lobo, ) and the postmetamorphic presence of the lateral line system (Fritzsch, Drewes, & Ruibal, ; Quinzio & Fabrezi, ).…”

Heterochrony in Growth and Development in Anurans from the Chaco of South America

“…Lepidobatrachus is aquatic with some distinctive traits (flattened stout body covered with loose skin, very broad head, prominent dorsally located eyes, small tympanum, short legs, webbed toes with keratinized claws, subarticular tubercles reduced or absent, a functional lateral line system in L. laevis, discontinuous ceratohyalia, single dermal ossification dorsally located in the hyoid, reduction or loss of hyoid and tongue muscles, small tongue) deviated from the pattern of terrestrial and aquatic ceratophryids (i.e. Telmatobius) (Fabrezi and Lobo 2009).…”

“…The ceratophryines share a set of numerous morphological features (Haas 2003;Fabrezi and Emerson 2003;Fabrezi 2006;Quinzio et al 2006;Fabrezi and Quinzio 2008;Fabrezi and Lobo 2009). Besides, they also share an accelerated growth of their larvae.…”