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The larval chondrocranium of the large-headed leptodactylid frog, Chacophrys pierotti (Ceratophryinae), is described in detail. Descriptions include the ontogeny of the chondrocranium and osteogenesis of the cranial skeleton. The chondrocranium of C. pierotti is profoundly different from the chondrocrania previously described for the other genera of the Ceratophryinae (Ceratophrys and Lepidobatrachus). The chondrocranium of Chacophrys is longer than wide and not particularly robust or laterally expanded; that of Ceratophrys is very robust, whereas the chondrocranium of Lepidobatrachus is widely expanded laterally. These differences are particularly apparent in the elements associated with the jaw (i.e., suprarostral, infrarostral, Meckel's cartilage, palatoquadrate, cornua trabeculae), which are robust in Ceratophrys and thin and elongate in Lepidobatrachus. Unlike Ceratophrys and Lepidobatrachus, which possess highly specialized carnivorous larva, the chondrocranium of Chacophrys more closely resembles the typical microphagous herbivore morphology characteristic of other leptodactylid frogs for which the chondrocrania are known. These data suggest that Chacophrys is the basal taxon within the monophyletic Ceratophryinae. The ontogeny of the chondrocranium of Chacophrys, as well as the cranial ossification sequence, do not differ greatly from those described for Ceratophrys. Detailed descriptions of the ontogeny of the chondrocranium and the bony skeleton are needed for additional taxa within the Ceratophryinae (especially Lepidobatrachus). Such descriptive ontogenetic studies promise new insight into the phylogeny and morphological evolution of this remarkable group of large-headed frogs., (Copyright 1999 Wiley-Liss, Inc.)

The adult skeleton and tadpole chondrocranium of the leptodactylid frog, Ceratophrys cornuta (Ceratophryinae), are described in detail, including the ontogenetic development of the chondrocranium and the ossification sequence of the skeleton. The chondrocranium of the carnivorous larvae is unique in lacking a frontoparietal fontanelle and possessing a complete dorsal roof of cartilage. Furthermore, the chondrocranium is extremely robust, particularly those elements involved in the feeding mechanism; these include large palatoquadrate cartilages, stout Meckel's, supra-, and infrarostral cartilages, and short, wide, cornua trabeculae. The chondrocranium of C. cornuta resembles that described for Ceratophrys cranwelli, but differs from the chondrocrania reported for the species of Lepidobatrachus. The large adult skull is hyperossified; most elements are fused into a single unit, and nearly all dermal elements are ornamented, casqued, and co-ossified. Calcification is present in nearly every cartilaginous element of the skeleton in larger (older) adults. Several osteological characters previously used in ceratophryine systematics, such as the otic ramus of the squamosal and the columella, are reassessed. Contrary to previous reports, the ossified, dorsal dermal shield above the vertebral column in many ceratophryine anurans is absent in C. cornuta. With few exceptions, the ossification sequence relative to metamorphosis is consistent with those that are known for other anurans. The squamosal arises from three distinct centers of ossification, including an otic element. The frontoparietal arises from two centers of ossification that fuse early in development. A robust postorbital arch is formed primarily by the otic flange of the frontoparietal, which articulates laterally with the medial border of the otic ramus of the squamosal. Changes in the timing of development, or heterochrony, are involved with the evolution of the unusual skull and skeleton of ceratophryine frogs.