Ceratophrys ameghinorum 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 : 45-46

publication ID	https://doi.org/ 10.11646/zootaxa.4658.1.2
publication LSID	lsid:zoobank.org:pub:16EDCB6E-49D1-4214-AEB3-203C19CA56A0
persistent identifier	https://treatment.plazi.org/id/3C7387AF-FFA2-FF9A-19E5-F96221B054D4
treatment provided by	Plazi
scientific name	Ceratophrys ameghinorum Fernicola 2001
status

Treatment

Ceratophrys ameghinorum was named by Fernicola (2001) on the basis of a series of remains collected in sediments of the Monte Hermoso Formation (Late Miocene–Early Pliocene; reviewed by Cione et al., 2007) exposed at the Farola Monte Hermoso locality ( Fig. 1 View FIGURE 1 , locality 3). Additional material collected in sediments exposed in several coastal localities in the province of Buenos Aires ( Table 1 View TABLE 1 ) was also assigned to this species but, in most cases, the stratigraphic data are somewhat equivocal. Most of the fossils were recovered from coastal cliffs exposed between the cities of Mar del Plata and Miramar ( Fig. 1 View FIGURE 1 , locality 8); these sediments have been interpreted to represent one or several units deposited during the Plio-Pleistocene (reviewed by Zarate 2005). Specimen MLP 52.IX.27.11 from Mar del Sur, a locality south of the city of Miramar, was assigned by Frenguelli (1921) to C.ornata ( Fernicola 2001) View in CoL ; but it also was thougt to represent C. ameghinorum ( Fernicola 2001; contra Stoesel et al. 2008). Frenguelli ascribed this fossil to the Aimaran Horizon, a paleosol considered equivalent to the inferior part of Fm. La Postrera (late Pleistocene–early Holocene fide Tonni et al. 2002).

Osteological features. Examination of all the material attributed to Ceratophrys ameghinorum ( Table 1 View TABLE 1 ) reveals that the general osteology of this robust toad resembles that of other species of Ceratophrys ( Fig. 2 View FIGURE 2 ). The skull is high, although its greatest height is less than a half of its greatest width. The squamosal otic plate is subtriangular in dorsal aspect ( Fig. 2B View FIGURE 2 ), projects dorsally beyond the dorsal surface of the skull roof ( Fig. 2H View FIGURE 2 ), and extends posteriorly beyond the level of the occipital condyles ( Fig. 2B View FIGURE 2 ). Laterally, the squamosal otic ramus projects ventrally as a robust lateral wall ( Fig. 2H View FIGURE 2 ). A smooth crest is present along the lateral edge of the otic ramus separating its dorsal and lateral portions; the crest continues anteriorly over the zygomatic ramus of squamosal and the maxilla ( Fig. 2H View FIGURE 2 ). The vomers are dentate. A delicate ventral process is present on the anterior ramus of the pterygoid ( Fig. 2K View FIGURE 2 ). The atlas possesses cotyles with discrete articular surfaces. A dorsal shield formed by several plates lies dorsal to Presacral Vertebrae I–IV.

Remarks. Ceratophrys ameghinorum possesses all proposed and possible synapomorphies of Ceratophryidae and Ceratophrys . Rovereto (1914) mentioned that C. ameghinorum (as C. prisca ) differed from C. ornata in the shape of the squamosal otic plate (as squamosal expansion) and the presence of a crest. Fernicola (2001) considered that C. ameghinorum differs from all other species of the genus in the shape and orientation of the squamosal otic plate, the presence of a lateral crest, and the separation of the atlantal cotyles. Certainly, the squamosal of C. ameghinorum differs from those of other Ceratophrys because no other Ceratophrys possesses squamosal otic plates that project dorsally beyond the dorsal surface of the skull roof. The shape and extension of this plate, however, is shared with the [ C. calcarata – C.cornuta ] clade ( Fig. 2 View FIGURE 2 ). The lateral wall observed in the otic ramus of C. ameghinorum also occursin the [ C. calcarata – C.cornuta ] and [ C. aurita – C. joazeirensis ] clades ( Fig. 2 View FIGURE 2 G−I). The skulls of C. calcarata and the [ C. aurita – C. joazeirensis ] clade have similar lateral crests to those of C. ameghinorum . In the [ C. aurita – C. joazeirensis ] clade, however, these crests are more conspicuous, perhaps because they are associated with a series of depressions in the skull roof that are absent in C. ameghinorum . A separation between the atlantal cotyles also characterizes other Ceratophrys (e.g. C. cranwelli FML 5472; 5474). It should be noted that C. ameghinorum resembles the species of the southeastern clade of Ceratophrys in having a dorsal shield composed of several plates.

Neither the presence of a lateral crest, nor the morphology of the atlantal cotyles are unique to Ceratophrys ameghinorum as has been previously thought. Nevertheless, this species possesses an exclusive combination of characters ( Table 2 View TABLE 2 ), including a distinct orientation of the squamosal otic plate, that support its status as a distinct species. The binomium C. ameghinorum may need to be corrected because it seems to represent the same species described by Rovereto in 1914—i. e., the holotype and some paratypes of C.ameghinorum correspond to the material studied by this author; thus, the names of Rovereto’s varieties, as well as prisca , may be available ( ICZN Arts. 45.6.4.; 45.1−2). The phylogenetic position of C. ameghinorum within Ceratophrys awaits a phylogenetic analysis, given the mixture of characters it possesses of different clades of the genus.