The symmetry of the astragalar trochlea is considered an important morphofunctional and phylogenetic character in palaeontology. Here, we seek simpler methods to measure and evaluate it. We use a dataset of 89 genera from 56 families of Eutheria, including extinct Folivora, Litopterna, and Notoungulata. Several studies considered asymmetrical and shallow trochleas as characteristic of plantigrades, following the assumption that it would allow plantigrades greater eversion and inversion. However, here we observed that the eutherian upper ankle joint is a hinge joint restricted to a single principal movement. The symmetry index on eutherian plantigrades and digitigrades has considerable overlap, with plantigrades being more variable. The depth of the astragalar trochlea has more statistical significance than symmetry. Our results suggest plantigrady allows considerable morphological variation in the astragalar trochlea, while unguligrady and digitigrady are more restrictive. Eutherian mammals restraining movement of the foot to the parasagittal plane modify the transverse tarsal joint primarily, this joint being responsible for inversion-eversion movements. Smutsia and pilosans with a pivot-type transverse tarsal joint have the most asymmetrical trochleas. The trochlea in Pleistocene ground sloths has been described as an odontoid-discoid morphology. In our analysis, this highly asymmetrical trochlea tali shares the morphospace with the silky anteater and the giant pangolin, plantigrades ecologically very different from giant ground sloths. In the pangolin, the large lateral condyle is more related to the shape of the fibula than to the tibia. Our results question the use of the asymmetry of the astragalar trochlea to differentiate plantigrady and digitigrady. The plantigrade-digitigrade-unguligrade model may fall short in representing the relationship between feet and substrate, particularly when fossil diversity is included. A more nuanced approach, considering the complex interplay of various factors, is necessary to avoid premature conclusions.
Pleistoanser bravardi Agnol & iacute;n, 2006, was described as a tadornine anseriform from the Lower-Mid Pleistocene of southern Buenos Aires Province, Argentina. The genus and species were based on a partial associated forelimb (i.e. coracoid, humerus, radio, ulna, carpometacarpus) and was described as a small and very apomorphic duck. A restudy of the original specimen, and a reconstruction of the holotype humerus, allowed us to recognise that P. bravardi was not an anseriform bird but clearly belonged to Psittaciformes. The humerus shows strong anatomical similarities to the extant genus Cyanoliseus, resulting in the new combination Cyanoliseus bravardi (Agnol & iacute;n, 2006) nov. comb. With the reclassification of this species, there would be a total of four species of the genus Cyanoliseus described for the Pleistocene of the southern of South America, indicating that the clade of these desert-dwelling parrots was more speciose in past times.
The karst region of Lagoa Santa, eastern Brazil, represents one of the most significant Quaternary palaeontological records in South America, preserving a diverse assemblage of extinct and extant vertebrates. This study presents a comprehensive taxonomic, morphological, and taphonomic analysis of Cingulata remains recovered from two cave deposits. The analysed material comprises more than 1,200 specimens, including both skeletal elements and osteoderms. The first assemblage, which is quantitatively dominant, is characterised by dasypodid taxon assigned to Dasypus punctatus, an extinct species previously reported for the region. This attribution is supported by the diagnostic morphology of the osteoderms as well as by the robust dimensions of the appendicular elements. At least two individuals were identified in this assemblage, including one adult and one subadult. In contrast, the second locality yielded a comparatively small number of specimens, consisting primarily of isolated osteoderms attributable to both extinct and extant taxa, including the genera Dasypus, Cabassous, and Euphractus. While some osteoderms are consistent in size with D. punctatus, others correspond to extant species, suggesting the persistence of these lineages since the Late Pleistocene. Taphonomic analyses indicate distinct depositional histories for the two sites. The assemblage from the more abundant locality reflects predominantly in situ accumulation, followed by weathering, fragmentation, and limited sedimentary reworking, with partial preservation of anatomical associations. Conversely, the second assemblage consists mainly of isolated and occasionally polished osteoderms, indicating secondary deposition under moderate-energy conditions. The coexistence of extinct and extant taxa, combined with the ecological plasticity of the identified genera, suggests that Late Pleistocene environments in the Lagoa Santa region were not characterised by extreme climatic conditions. However, paleoenvironmental reconstructions remain constrained by the ecological generalism of the taxa and the potential effects of temporal mixing within the deposits.
Early studies on Cretaceous pycnodontiforms from the West Iberian Margin were based on isolated dental elements collected in the late nineteenth century. Mid-twentieth century fieldwork provided additional material, including articulated specimens, and later research by the University of Coimbra recovered further dental remains from Upper Cretaceous units of the Coimbra-Figueira da Foz region. Most of this material remains unpublished. Here, seven specimens are described, six of them for the first time. Although incomplete, they are well preserved and represent large-bodied pycnodonts individuals. These specimens offer novel insights into the anatomy of the dental apparatus and the palaeoecology of pycnodonts from the carbonate platforms of the West Iberian Margin, thereby enhancing our understanding of the structure and dynamics of coastal ecosystems in this branch of the southwest European Tethys Realm during the Late Cretaceous.
