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The Paucituberculata are a group of marsupials endemic to South America, recorded from the Early Eocene to the present. In terms of taxonomy and qualitative morphology, paucituberculatans are a quite diverse and disparate group, especially considering their extinct representatives. This study aimed to investigate the variability in the quantitative morphology of paucituberculatans in the context of the largest morphometric study of the group performed to date. Due to the fragmentary fossil record, this work focused on lower dental morphology which allowed us to compare around 95% of paucituberculatan species through the measurement and analysis of almost 1500 specimens. Dental measurements of 27 variables were analysed by Principal Component Analysis and Partial Least Squares correlation as exploratory methods. As a result, it is shown that the continuous variability is expressed not only in size differences among species but also in morphological variability of individual teeth, and differences in size and proportions along the molar row. We conclude that paucituberculatans are a group of important morphological diversity regarding quantitative morphology. Many of the quantitative taxonomic features discussed in the literature were corroborated in this study. In addition, we discussed potential evolutionary and palaeoecological implications of this study, highlighting prospects for future studies. [ABSTRACT FROM AUTHOR]

Hystricognath rodents arrived in South America from Africa during the Paleogene. The oldest South American rodents (Caviomorpha) were intensively studied in recent years. One of these assemblages is the caviomorph paleofauna from Santa Rosa, Peru. Their age was originally estimated as ?Eocene. Here, we report new caviomorph fossils from Santa Rosa and review the previously described rodents taking into account new dates and updated caviomorph information. We identified 18 genera and 22 species, including one new genus and species (Vucetichimys pretrilophodoncia gen. et sp. nov.), and two new species (Shapajamys minor sp. nov. and Ucayalimys amahuacensis sp. nov.). All taxa are brachydont, with visible cusps, and thin crests. The Santa Rosa rodents are one of the oldest and the most diverse caviomorph paleofaunas known from low latitudes of South America. Similarities between these caviomorphs and other Paleogene assemblages lead us to propose an early Oligocene age for those rodents from the Yurúa River (Brazil) and a close temporal relationship with the oldest known levels from Contamana. This new biochronological scenario has deep implications in the origin and early evolution of caviomorphs. A middle Eocene? entrance of one or several waves of African rodents arriving in South America is possible. [ABSTRACT FROM AUTHOR]

Numerous isolated teeth recovered from the Upper Triassic Tiki Formation of India have high, cylindrical, triangular to conical crowns with serrated mesial and distal carinae, and oval/subcircular and elliptical crown bases. Within this overall morphology, the teeth are subdivided into six morphotypes based on crown proportions, nature of carinae and serration and crown-base ratios. These ziphodont teeth are compared with those of other dominant Late Triassic carnivores of India to show similarity with that of the phytosaurs based on their shape, recurved nature, crown proportions, the presence of carina(e), nature of serrations and serration density. The different morphotypes reflect positional heterodonty, and three upper jaw dental sets are identified. This finding is corroborated by PCA, where the morphotypes form distinctly separate clusters, though partial overlapping of these convex hull polygons suggests that these teeth belonged to a single phytosaur taxon. As tripartite dentition is a derived condition; it may be concluded that these isolated teeth belonged to a more derived phytosaur, yet to be recovered from the Tiki Formation. The study highlights the importance of examining isolated teeth in order to identify the fossil forms which are yet to be discovered. [ABSTRACT FROM AUTHOR]

Mosasaurus lemonnieri is a mosasaurine mosasaurid first unearthed from the lower Maastrichtian of the Mons Basin, southern Belgium. Even though numerous well-preserved specimens have been attributed to the taxon, the knowledge of its anatomy is surprisingly poor and merely limited to some general characteristics. Here I describe the morphology of the marginal dentition of M. lemonnieri based on the holotype and 14 referred individuals originating from the upper Campanian and Maastrichtian of Belgium. The dental variability is assessed through linear discriminant analyses aimed to appraise the tooth crown distinguishability between (1) individuals, (2) tooth-bearing elements (premaxillae, maxillae, and dentaries), and (3) within particular jaw regions (anterior, middle, and posterior). The overall dental distinguishability between individuals was, expectedly, poor though the rates of correctly classified teeth differed for particular specimens, which can have taxonomic implications. The premaxillary and maxillary teeth were inferred to be more distinguishable than the dentary teeth. The dental distinguishability of M. lemonnieri is further compared to that of other sympatric and potentially sympatric taxa. The use of mosasaurid dental measurements substantially facilitates the comparisons of mosasaurid teeth on both inter- and intraspecific scale, increasing the accuracy of the studies appraising the patterns of mosasaurid dental evolution. [ABSTRACT FROM AUTHOR]

Dental homologies and evolutionary transformations within caviomorph rodents have long been disputed. Here, we participate in these debates in providing new insights from the dental morphology of Paleogene caviomorphs from Peruvian Amazonia (Contamana and Shapaja). Their analyses and comparisons with many hystricognaths allow (1) to generalize some hypotheses previously proposed about occlusal morphology of caviomorph cheek teeth, and (2) to propose new ones. In caviomorphs, the third crest of upper teeth would correspond either to a mesoloph or to a mesolophule or to a combination of both. The transformation from a pentalophodont pattern to a tetralophodont pattern would be explained by the disappearance of the metaloph. Likewise, the transformation from a tetralophodont pattern to a trilophodont pattern is observed by the loss of the third crest. A direct transformation from a pentalophodont pattern to a trilophodont pattern is also observed. Concerning lower teeth, discrepancies of homologies are centered on the mesial cristids, which can be notably distinguished depending on their compositions and connections with other structures. The ancestral patterns of caviomorph lower molars and dp4s were likely tetralophodont and pentalophodont, respectively. However, schemes with five and four (even three) transverse cristids cannot be ruled out for the two loci, respectively. [ABSTRACT FROM AUTHOR]