The early period of life is crucial for the development of species-specific traits and, as such, for a correct understanding of the evolutionary constraints and adults’ adaptations. However, this critical aspect of life history is usually inaccessible for extinct mammals. One of the exceptions is the cave bear ( Ursus spelaeus ), whose hibernacula have yielded a sufficient number of cub remains at various ontogenetic stages. Unfortunately, although they have been studied for over a century, there is no consensus regarding their interpretation, which hinders their unambiguous integration into palaeobiological models. New excavations in Barová Cave (Czech Republic) have yielded unique finds of several partially preserved bear skeletons of various ages. Along with the cub skeletons from the Goyet Cave (Belgium) and isolated juvenile long bones from both localities, they enabled us to critically assess our knowledge of cave bear development during first year of cave bear life and solve thus this long-time controversy. Our results reveal that: (i) cave bear cub skeletal development during the first active season was quicker than in brown bears; (ii) tooth eruption timing was generally the same for both species and, thus, one of the main mortality peaks of cave bear cubs took place late during their first active season; (iii) mortality patterns of cubs are the same for cave bear hibernacula from Spain to the Urals. We connected the mortality peak during the active season with an unsuccessful transition to an adult diet.
Amongst the most extraordinary extinct ophiuroids is the genus Astrosombra from the Upper Cretaceous of Germany. Initially known from isolated ossicles only, the extremely expanded lateral arm plates suggested an aberrant body shape comparable to that seen in the extraordinary astrophiurid genus Astrophiura . Here, we describe the first articulated specimen of Astrosombra rammsteinensis , the type and only known species of the genus, from the type locality of the taxon, showing the highly modified lateral arm plates in their anatomical context and providing insights into the general skeletal morphology. The new specimen confirms the presence of extremely widened arms, formed by the aberrantly expanded lateral arm plates articulating with unusually wide vertebrae and covered dorsally by multiple rows of dorsal arm plates. The width of the arms is further increased by large, flat, feather-like arm spines. MicroCT images of the articulated disc revealed morphological details, in particular, high oral plates with wing-like expansions, suggesting transfer of Astrosombra from the Amphilimnidae to the Ophiopsilidae. In analogy with Astrophiura , the extremely widened arms, the fringe of flat arm spines, the large tentacle pores and the overall flat body shape suggest that Astrosombra inhabited the small, patchy hard substrates formed by the skeletal remains of other organisms.
Two temnospondyl specimens from the Ruthweiler deposit (M8) in the early Permian Meisenheim Formation of the Saar-Nahe Basin are identified as pertaining to a new branchiosaurid taxon, Schoenfelderpeton brevifrons . They are distinct from all other temnospondyls in the region by the delta-shaped skull, small orbits, and short frontals. The maxilla fails to contact the cheek and has tiny, pin-shaped teeth, a feature that persists in the mature specimen. Schoenfelderpeton brevifrons is found to nest with Leptorophus and “ Melanerpeton ” humbergense and forms the sister taxon to Schoenfelderpeton prescheri , with which it shares the short gape, open cheek, and an emarginated squamosal embayment.
Estimating diversity patterns from the fossil record is essential for understanding the factors that shape biodiversity. The Jurassic/Cretaceous transition 143.1 million years (Ma) ago is a particular interval of pronounced ecological turnover accompanied by a global sharp diversity decline, disproportionately affecting larger and more specialised terrestrial taxa such as Sauropoda. Sauropods are a diverse group of large herbivorous dinosaurs, considered a good model for studying long-term biodiversity trends because of their prominent ecological roles and abundant fossil record. In this study, we analyse paleodiversity patterns for Diplodocoidea as a whole and for each of its subclades. Diplodocoidea is a subgroup of neosauropods that includes three main subclades: Dicraeosauridae, Diplodocidae, and Rebbachisauridae. The Flagellicaudata (= Dicraeosauridae + Diplodocidae) were notably affected by the Jurassic/Cretaceous faunal turnover, whereas Rebbachisauridae originated and persisted into the Early to mid-Cretaceous. Our key findings are: (1) high diversity during the Late Jurassic; (2) a sharp decline in diversity just before or during the Jurassic/Cretaceous transition; (3) a diversity peak in the Early Cretaceous Aptian stage; (4) overall higher Diplodocoidea diversity in the Early Cretaceous compared to the Late Jurassic; and (5) distinct geographic distributions, with Flagellicaudata restricted to high latitudes, while Rebbachisauridae occupied the full latitudinal range of Diplodocoidea. Our results suggest that the observed paleodiversity patterns were likely influenced by abiotic factors, and that Flagellicaudata and Rebbachisauridae may have been subject to distinct climatic constraints, potentially reflecting different ecological strategies. Additionally, this study underscores the impact of sampling biases on diversity estimates and challenges previous assumptions about sauropod diversity patterns, opening new directions for future research.
Bioerosion of fossil bones provides insights into trophic relationships as well as carcass decomposition processes in past ecosystems. Despite this potential, however, exhaustive documentation of traces of bioerosion for specific deep-time vertebrate assemblages is rarely done. Such occurrences are present in the uppermost Cretaceous continental deposits from Haţeg Basin, famous for their rich, island-dwelling vertebrate faunas, that previously yielded several examples of bioerosion on bones although only few instances have been described in detail and those are largely limited to a single lithostratigraphic unit. For this study, an extensive survey of these vertebrate assemblages was conducted, yielding several new examples from three further lithostratigraphic units. The newly identified traces occur on turtle and dinosaur remains, and include six morphotypes attributable to termites, dermestid beetles, and multituberculate mammals. These results demonstrate that bioerosional traces are more widely distributed in the uppermost Cretaceous of Haţeg Basin, both spatially and temporally, than previously recognized and occur on bones from various paleoenvironmental settings. Notably, all traces indicate a prolonged exposure before final burial, which appears to have been a consistent feature of the sampled paleoenvironments. Nonetheless, regional differences are evident, and bioerosional traces are less common in poorly drained paleoenvironments than in better-drained ones. Finally, the mode of carcass decomposition appears to have been similar across all sampled localities, irrespective of geological age or depositional environment, and involved a consistent set of saprophagous animals, suggesting a stable composition of the saprophagous communities, aligning well with the presumed faunal stability of Haţeg Island.
