Ceratophrys cf. ornata (Fernicola, 2001)

Nicoli, Laura, 2019, The fossil record of Ceratophrys Wied-Neuwied (Anura: Ceratophryidae): a revision and update of fossil South American horned frogs, Zootaxa 4658 (1), pp. 37-68 : 57-59

Unidentified Ceratophrys cf. ornata from Chuquisaca, Bolivia ( Vergnaud-Grazzini 1968)

Two partial skulls, an isolated premaxilla, and a series of postcranial elements from Ñuapua locality ( Fig. 1 , locality 9) in the department of Chuquisaca, Bolivia, have been attributed to Ceratophrys cf. ornata by Vergnaud-Grazzini (1968). These remains were collected in the second member of the Ñuapua Formation, Ñuapua 2, which was attributed to the Holocene ( Marshall et al. 1984; Vergnaud-Grazzini 1968). Vergnaud-Grazzini (1968) briefly described and partially illustrated (photographs) the remains (plate XXXVII figs. 1 – 9). The author did not report where the specimens were deposited, but they were located in the Paleontological Collection of the Muséum National d’Histoire Naturelle and they lack collection numbers. In addition to the published photograph of the material, the museum provided photographs of the remains.

Osteological features. Neither skull is complete. One consists of most of the ossified neurocranium and skull roof, and part of the left maxilla ( Fig. 6C, D ), whereas the other is the posterior part of the central cranium ( Fig. 6E ). Both resemble these respective areas in all other Ceratophrys . The condition of the teeth cannot be described because none is completely preserved. Likewise, the poor preservation obviates description of the shape and extension of the squamosal otic plate ( Fig. 6C ). The vomers are in medial contact and bear dentigerous processes in most complete specimen ( Fig. 6D ); however, I could not determine whether true vomerine teeth were present. No crests are evident in the preserved skull roofs.

The isolated premaxilla of this assemblage ( Fig. 6F, G ) possesses a high, but incomplete, alary process, which is as long as the pars dentalis of the bone. The anterior surface is rounded. In lingual view, the premaxilla lacks a pars palatina, but possesses a distinct, well-developed palatine process. A well-developed, short maxillary process, with a sharp, dorsally directed end also is evident ( Fig. 6F ).

Vergnaud-Grazzini (1968) provides information and illustrations of the postcranial elements of the assemblage. The vertebrae attributed to Ceratophrys have neural arches considerably wider than long ( Vergnaud-Grazzini 1968: pl. XXXVIII, figs. 2–4; 9). The atlantal vertebrae have discrete, rather than contiguous cotyles. The transverse processes and diapophyses of the vertebrae are nearly as long as the corresponding neural arches.

Half of a pectoral girdle is represented by three fused elements—scapula, clavicle, and coracoid. The scapula is extremely wide, with the glenoid fossa being nearly three times the shaft width; the pars acromialis is not expanded and the lateral margin is not posteriorly deflected ( Vergnaud-Grazzini 1968: pl. XXXVIII, fig. 7).

Remarks. The most complete skull of the assemblage ( Fig. 6C, D ) has all the proposed synapomorphies for Ceratophryidae (skull exostosis, parieto-squamosal arch, maxilla-squamosal contact, expanded squamosal otic ramus overlapping prootic, and absence of pars palatina on anterior maxilla) and Ceratophrys (robust, bar-shaped maxillary processes of nasals, postorbital fenestra). Although its attribution to Ceratophrys is well supported, it is not possible to associate it with a less-inclusive taxon.

Although the other skull of the assemblage ( Fig. 6C ) is morphologically similar to those of Ceratophrys , it lacks any diagnostic osteological features of the genus. The skull seems to be exostosed. However, exostosis is a highly homoplastic character among anurans and certainly not exclusive to Ceratophryidae ; thus, its occurrence in this fossil does not support attribution to the family.

The premaxilla ( Fig. 6F, G ) has all of the proposed diagnostic characters of this bone for Ceratophryidae (absence of pars palatina, long alary process) but it lacks those proposed for Ceratophrys . The premaxillae of Ceratophrys lack anteriorly convex alary processes, like those of Lepidobatrachus , Chacophrys , and this fossil. Likewise, members of Ceratophrys lack the discrete palatine process and short, acuminate maxillary process present in this fossil. Thus, the attribution of this element to Ceratophryidae is well supported, whereas its assignment to Ceratophrys is questionable. Assuming that this element represents the same taxon as the most complete skull in the assemblage would require that the assemblage of remains represents a taxon with a combination of characters different from that of all known Ceratophryidae . Given the disarticulated condition of the fossils and the presence of other anurans in the same levels, it is more reasonable to conclude that the fossils represent different taxa.

The vertebrae attributed to Ceratophrys by Vergnaud-Grazzini (1968) for which photographs are available lack the possible synapomorphies of Ceratophryidae proposed for these elements. The atlantal cotyles are separate and the transverse processes of the anterior vertebrae shorter than (or of equivalent length to) the corresponding neural arch widths. The neural arches are considerably wider than long ( Vergnaud-Grazzini 1968: pl. XXXVIII, figs. 2–4). Thus, the attribution of these elements to Ceratophryidae is not supported.

The pectoral girdle remains are consistent with the morphology of the pectoral girdle of Ceratophryidae . No possible synapomorphies are recognized in these elements, given their similarities with the elements of the pectoralgirdle of the possible closed related Odontophrynidae .

The occurrence of Ceratophrys at this fossiliferous locality is evidenced by the most complete skull described herein. However, only the premaxilla in the remaining elements, can be attributed to Ceratophryidae , and no evidence supports its placement in Ceratophrys . The pectoral girdle remains could represent ceratophryids in the assemblage, although they cannot be unequivocally attributed to this clade. There is no evidence to assign the vertebrae to Ceratophryidae .

Figures

FIGURE 1. Distributional map of extant and fossil Ceratophrys. The phylogeny of the extant species of Ceratophyrs were proposed by Faivovich et al.(2014). The numbers in circles represent the fossiliferous localities mentioned in the article: 1, Arroyo Chasicó; 2, Arroyo Tapalqué; 3, Conchillas; 4, Farola Monte Hermoso; 5, Fortín Necochea; 6, Lagoa Santa; 7, Laguna de Los Tres Reyes; 8, Mar del Plata and Miramar cities; 9, Ñuapua; 10, Olivos; 11, Puerta de Corral Quemado; 12, Quehué; 13, San Antonio and Paso Alsina; 14, Tarija. Black circles: localities where the presence of Ceratophrys was confirmed; white circles: the presence of Ceratophrys remains unconfirmed. The distributions of the extant species of Ceratophrys are represented by areas that approximately include all the reported records for each species; the distribution of most species, however, is not well known. Distributions are based on Lynch (1982) with corrections and additions from Barrio-Amorós 2004; Barrio 1980; Langone 1995; Maciel et al. 2013; Maneyro & Langone 2001; Ortiz et al. 2013; Peters 1967; Rivero 1961; Stuart et al. 2008.

FIGURE 6. Quaternary fossils attributed to Ceratophrys. A, fossil columella (MLP 86.VIII.1.5) from Laguna Los Tres Reyes Locality, province of Buenos Aires, Argentina, attributed Ceratophrys cf. ornata by Perí (1993). B, columella of C. cranwelli (FML 5475). C–G, two incomplete skulls (C–E) and a premaxilla (F, G) from Ñuapua, Bolivia, attributed to Ceratophrys cf. ornata by Vergnaud-Grazzini (1968). H–K, fossils from the Arroyo Tapalqué locality, Buenos Aires, Argentina, listed as Ceratophrys sp. by Mercadal de Barrio & Barrio (2002); H–J, MLP 86.III.25.150: squamosal (H) and right maxilla (I, J); K, MLP 86.III.25.151: frontoparietals. A,C, H, K, dorsal views; B, ventral views; D, J, lingual views; E, I, labial views. Abbreviations: as, angulosplenial; d, dentary; fp, frontoparietal; pp, premaxillary palatine process; ppa, discrete pars palatina absent; lc, lateral crest; mk, mentomeckelian; mop, material of preparation; mp, maxillary process of nasal; mpp, maxillary process ofpremaxilla; mps, socket that would receive the maxillary process of premaxilla; ncs, socket that would have received the ossification of the nasal cartilages; oc, occipital condyle; otc, otic capsule; pas, socket that would have received the ossifications of the planumantorbitale; pf, pars facialis; pof, space delimiting by the showed bone that corresponds to the postorbital fenestra; pp, pars palatina; ppa, discrete pars palatina absent; psa, portion of the bone that forms the parieto-squamosal arch; psf, parasphenoid; pt, pterygoid; ptp, pterygoid process; qj, quadratojugal; th, teeth; slw, squamosal lateral world; sop, squamosal otic plate; sf, space delimiting by the showed bone that corresponds to the subtemporal fenestra; v, vomer; vr, squamosal ventral ramus; zr, squamosal zygomatic ramus. Scale bar is 5 mm.