Foss. Stud., Volume 3, Issue 4 (December 2025) – 3 articles

Coelacanths in the Family Mawsoniidae include ten genera with a primarily Gondwanan distribution. Two of the genera—Mawsonia and Axelrodichthys—show a related biogeographic pattern of occurrences in the Cretaceous of Brazil and Africa. This report documents the presence of Axelrodichthys in the Early Cretaceous of Niger based on a partial skull roof and partial extrascapular series from the Aptian ‘Fish Mountain’ site at Ingal (or Ingall) in central western Niger. Assignment of the specimen to Axelrodichthys is based on the presence of a median extrascapular along the posterior margin of the skull roof, an element that is absent in the sister-genus Mawsonia. This record from Niger fits into the broader pattern of the genus co-occurring in both northeastern Brazil and northwestern Africa, and then subsequently expanding its range across Africa during the Cretaceous—reaching Niger at an intermediate stage—and then eventually dispersing as far east as Madagascar and as far north as what is now southern Europe by the Late Cretaceous. Full article

At 47° S in Argentine Patagonia, the interaction between the Southern Westerly Winds (SWW) and the Andean barrier generates a steep climatic gradient, providing an ideal setting to evaluate Holocene vegetation responses. This study focuses on the extra-Andean sector, where new pollen records from La Tapera (LTap) and Cisne 7 provide insights into steppe vegetation dynamics under dry conditions. These sequences are contrasted with previously studied records further west (LF, ZB, CMN1, CMN2, and COCU) to assess west–east gradients in vegetation change and moisture availability throughout the Holocene. Western records indicate that the Early Holocene was dominated by grass–dwarf-shrub steppe under arid conditions, followed by increased humidity around 7600 cal yr BP that promoted the development of forest–steppe ecotonal environments. The Middle Holocene was characterised by aridity, reflected in shrub dominance and reduced forest signals, whereas the Late Holocene included a humid pulse between ~1750 and 1000 cal yr BP, followed by renewed aridity over the last millennium. In contrast, eastern records show persistent shrub–dwarf-shrub steppes since ~4700 cal yr BP, with vegetation changes expressed mainly as shifts in the relative dominance of shrubs and dwarf–shrubs rather than floristic replacements. Archaeological sites corroborated and complemented the continuous records, strengthening the reconstruction of environmental variability across different temporal windows. Overall, this west–east comparison highlights the differential sensitivity of ecosystems to SWW fluctuations, reinforcing their role as an important forcing of hydrological balance and vegetation dynamics in mid-latitude Patagonia. Full article

Onychophora (velvet worms) are rare, soil-dwelling invertebrates with a fragile body structure that limits their fossil record. Their current distribution across the Neotropics has long been shaped by vicariance and dispersal events. Here, we evaluate the hypothesis that the Cretaceous–Paleogene (K–Pg) asteroid impact played a role in shaping the modern biogeography of Onychophora by eliminating lineages within the affected zone. Using published molecular phylogenies and geological data on the Chicxulub impact, we assess whether extant clades are congruent with a post-impact recolonization scenario. We find that several clades have divergence dates incompatible with extinction at the K–Pg boundary and that current distributions do not show a clear biogeographic signature consistent with impact-induced extirpation. Our hypothesis test supports the survival of onychophoran lineages through the K–Pg event and calls for caution in attributing modern distributions to a single extinction event without integrating molecular, stratigraphic, and ecological data. Full article