[Most Recent Entries] [Calendar View]
Wednesday, March 6th, 2024
| Time | Event | ||||
| 11:25a | [Paleontology • 2024] Khinjaria acuta • A bizarre new plioplatecarpine mosasaurid (Squamata: Mosasauridae) from the Maastrichtian of Morocco
Abstract The Upper Maastrichtian of Morocco has produced a remarkably diverse fauna of mosasaurids, the most diverse known for any time or place. As apex predators, Mosasauridae provide a picture of the marine ecosystem just before the end-Cretaceous mass extinction. Here we describe a bizarre new plioplatecarpine mosasaurid, Khinjaria acuta, characterized by enlarged, dagger-like anterior teeth, short, robust jaws, and posterior elongation of the skull. Khinjaria is related to Goronyosaurus nigeriensis from Nigeria and Niger, and Gavialimimus almaghribensis from Morocco. These species form a distinct clade of specialized mosasaurids so far unknown outside of Africa. Mosasaurids show high endemism in the Maastrichtian, with different lineages occurring in different regions, implying that mosasaurid diversity is underestimated because of limited geographic sampling. The large size, robust jaws, akinetic skull, and bladelike teeth of Khinjaria suggest it was an apex predator, but the unusual skull and jaw differ from those of contemporary predators like Hainosaurus, Thalassotitan, and Mosasaurus, suggesting a distinct feeding strategy. Mosasaurids became increasingly specialized in the latest Cretaceous, repeatedly evolving to occupy the apex predator niche, suggesting a diverse marine ecosystem persisted up to the K-Pg boundary. Late Cretaceous marine ecosystems differ from modern marine ecosystems in the high diversity of large predators.    Khinjaria acuta   Nicholas R. Longrich, Michael J. Polcyn, Nour-Eddine Jalil, Xabier Pereda-Suberbiola and Nathalie Bardet. 2024. A bizarre new plioplatecarpine mosasaurid from the Maastrichtian of Morocco. Cretaceous Research. In Press, 105870. DOI: 10.1016/j.cretres.2024.105870   | ||||
| 1:37p | [PaleoOrnithology • 2024] Imparavis attenboroughi • First Edentulous Enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Avifauna
Abstract Among Mesozoic birds, enantiornithines exhibit great morphological variation, which likely reflects their species diversity, range, and overall success throughout the Cretaceous. The majority of enantiornithines come from the Lower Cretaceous Jehol deposits (130–120 Ma) in northeastern China. In contrast to living birds, most enantiornithines were fully toothed. However, the rostral lengths, appendicular proportions, and pedal morphologies of extant birds can still inform on possible diet, flight mode, and ecology. Both partial (e.g., Longipterygidae) and complete tooth loss (e.g., Yuornis, Gobipteryx) are observed among enantiornithines, with edentulous rostra previously restricted to Upper Cretaceous taxa. Here, we describe the first edentulous enantiornithine from the Lower Cretaceous, Imparavis attenboroughi gen. et sp. nov., indicating a toothless beak evolved in this group 48 Ma earlier than previously recognized. Additionally, we reinterpret Chiappeavis as edentulous which together with the discovery of Imparavis indicates the complete loss of teeth in enantiornithines was not uncommon although still less frequent than observed in ornithuromorphs. The absence of gastroliths in all known enantiornithines suggests that the loss of teeth evolved under different pressures in these two ornithothoracine clades. Differences in rostral occlusion between Imparavis and Chiappeavis suggest they utilized different foraging strategies and possibly diet. Appendicular morphology in Imparavis suggest the capacity for relatively high wing beat frequency and powerful take-off capabilities. Together with the morphology of the hindlimb, we suggest Imparavis was primarily a terrestrial forager that could utilize sudden bursts of flight to escape into arboreal settings as a prey evasion strategy.
Systematic paleontology Aves Linnaeus, 1758 Pygostylia Chiappe, 2002 Ornithothoraces Chiappe, 1995 Enantiornithes Walker, 1981 Imparavis attenboroughi gen. et sp. nov. Locality and horizon. Collected near the village of Toudaoyingzi, Jianchang County, Liaoning Province, PR China; Lower Cretaceous Jiufotang Formation, 120 Ma (Lower Aptian) (He et al., 2004; Pan et al., 2013). Conclusions: Imparavis attenboroughi represents the first known edentulous enantiornithine from the Lower Cretaceous. The discovery of this taxon contributes to the multiple independent evolutionary occurrences of complete tooth loss among Mesozoic birds. The loss of teeth in enantiornithines may be linked to shifts in feeding behavior; however, as yet there is no evidence that this shift was driven by herbivory as is suggested for ornithuromorphs and non-avian dinosaurs. Rostral occlusion in Imparavis .... Xiaoli Wang, Alexander D. Clark, Jingmai K. O'Connor, Xiangyu Zhang, Xing Wang, Xiaoting Zheng and Zhonghe Zhou. 2024. First Edentulous Enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Avifauna. Cretaceous Research. 159, 105867. DOI: 10.1016/j.cretres.2024.105867 |
| << Previous Day |
2024/03/06 [Calendar] |
Next Day >> |