Calyptocephalella is nowadays only represented by the emblematic Chilean Helmeted Water Toad C. gayi, restricted to water bodies of Central Chile. Numerous fossil remains from latest Cretaceous to Miocene sedimentary rocks at the east of Los Andes have been attributed to this genus and several extinct Calyptocephalella species were erected. The relationships of these taxa, including the monophyly of the genus and the validity of some species, are however still unresolved. Here, we described a fossil anuran from the late Miocene of the northern Argentine Patagonia, which we attributed to a new extinct species of Calyptocephalella after analyzing the osteology and shared characters of all presumed species of the genus. These characters, whose co-occurrence seems to be exclusive of Calyptocephalella, include ornamented skull, extensive nasal processes contacting maxillae, broad nasal-frontoparietal contact, occipital artery enclosed by bone, maxilla contributing to the orbital margin and contacting squamosal, squamosal zygomatic and otic rami forming a continuous plate, scapula with a well-developed anterior lamina, and high iliac dorsal crest. The new species is differentiable in the proportion of the maxillary partes, the presence of a triangular maxillary postorbital process, a narrow maxillary contribution to the orbital margin, and an oblique frontoparietal-squamosal suture. We also analyzed the putative morphological and ecological diversity of Calyptocephalella along the geological record, from which this fossil is nowadays the youngest and northernmost record east of Los Andes. We concluded that Calyptocephalella would be a successful lineage that inhabited Patagonia since, probably, the latest Cretaceous and during most of the Cenozoic, whose diversification might be related with the environmental changes that took place in southern South America during the these times, and from which C. gayi is only a vestigial representative.

Calyptocephalella现在仅以具有象征意义的智利头盔水蟾蜍C. gayi为代表，仅限于智利中部的水体。从安第斯山脉东部的最新白垩纪到中新世沉积岩的许多化石遗迹都归于该属，并竖立了几种已灭绝的Calyptocephalella物种。然而，这些分类群的关系，包括属的单一性和某些物种的有效性，仍然没有得到解决。在这里，我们描述了来自阿根廷北部巴塔哥尼亚的中新世晚期的一种无尾龙化石，我们将其归因于一种新的灭绝物种Calyptocephalella在分析了该属所有假定物种的骨学和共有特征之后。这些角色，它们的共现似乎不包括Calyptocephalella，包括装饰性颅骨，广泛的鼻突接触上颌骨，广泛的鼻额顶接触，枕骨动脉被骨骼包围，上颌骨有助于眶缘并接触鳞状骨、鳞状骨颧骨和耳支，形成一个连续的板，肩胛骨前部发育良好椎板和高髂背嵴。新物种在上颌部分的比例、三角形上颌眶后突的存在、上颌对眶缘的狭窄贡献以及倾斜的额顶-鳞状缝线等方面是可区分的。我们还分析了沿地质记录的Calyptocephalella的推定形态和生态多样性，该化石是当今洛斯安第斯山脉以东最年轻和最北端的记录。我们得出的结论是Calyptocephalella将是巴塔哥尼亚的一个成功谱系，可能是在最近的白垩纪和新生代的大部分时间，其多样化可能与这些时期南美洲南部发生的环境变化有关，而C. gayi只是一个退化的代表。