Ben Creisler
Some new or not yet mentioned dinosaur-related papers:
Bruce M. Rothschild & Florian Witzmann (2021)
Identification of growth cessation in dinosaurs based on microscopy of long bone articular surfaces: preliminary results.
Alcheringa (advance online publication)
doi:
https://doi.org/10.1080/03115518.2021.1921273 https://www.tandfonline.com/doi/full/10.1080/03115518.2021.1921273As applied to bone, 'determinate growth' identifies an upper limit to size and the point when normal endochondral ossification ceases. This contrasts with 'indeterminate growth', which proceeds through the entire life of the animal. In this study, a non-destructive method, epi-illumination surface microscopy of the articular surfaces of long bones, is applied for the first time in 40 taxa of non-avian dinosaurs to determine cessation of endochondral growth. Thereby, the presence or absence of articular vascular channels between the endochondral bone and the cartilage is assessed. As articular vascular channels are the major source of nutrients for continued longitudinal growth, atrophy or loss of those channels would preclude continued growth of bone. We correlated our findings with published histological data and bone length measurements. We found articular vascular channels in all assessed dinosaur groups, but some individuals showed a loss of detectable articular vascular channels -- what we interpret as evidence of longitudinal skeletal growth cessation. This observation contrasts with the hypothesis of continuous indeterminate growth in dinosaurs, at least for the taxa identified here, in which channels have been documented as closed or closing over. The new method introduced here provides a phylogenetic tool for definitively distinguishing new 'dwarf' species from juveniles of known species. Furthermore, this study confirms the rarity of skeletally mature dinosaurs discovered to date and indicates that we have only begun to witness the full extent of dinosaur growth.
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Free pdf:
The discovery of theropod shed teeth associated with sauropod remains is relatively common in Cretaceous deposits of Patagonia. However, only a handful of studies have thoroughly explored the phylogenetic affinities of the theropod dental material. Here, we describe and identify twelve theropod shed teeth associated with a partially complete skeleton of a titanosaur sauropod from the Allen Formation (middle Campanian-lower Maastrichtian; Upper Cretaceous) of Paso CÃrdoba, RÃo Negro, Argentina. Using three methods, namely a cladistic analysis performed on a dentition-based data matrix, and a discriminant and cluster analyses conducted on a large dataset of theropod teeth measurements, we identify three dental morphotypes which are confidently referred to abelisaurid theropods. Whether the morphotypes represent different abelisaurid subclades or different positional entities within the jaw of the same abelisaurid species, is unknown. Such an identification, nevertheless, provides additional evidence of abelisaurids feeding on sauropod carcasses. This study highlights the importance of using combined qualitative and quantitative methodologies to identify isolated theropod teeth, especially those that can provide direct information on feeding ecology.
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Not yet mentioned on the DML:
Free pdf:
In October 2020, five dinosaur tracks were discovered on the bedding plane of the siltstone of the Lower Cretaceous Cangxi Formation in Tongjiang County, the northern margin of Sichuan Basin.Their morphology is similar to the classic theropods tracks of Eubrontes (such as bipedal, a broad pes, functionally tridactyl with a relatively short digit â). These tracks reveal that the medium to large-sized Eubrontes were widely distributed in the Lower Cretaceous of Sichuan Basin.This new discovery is of important significance to the paleoclimate, paleogeography and stratigraphic contrast of the northern margin of the Sichuan Basin.
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Free pdf:
The Upper Cretaceous in China is featured by fluvial deposits, such as channels and floodplains, in which abundant hadrosaur-dominated dinosaurs and dinosaur trace fossils are preserved. Whether these Late Cretaceous fluvial deposits belonged to certain large-scale paleoriver systems or not, and how the distribution pattern of paleoriver systems affected the evolution of terrestrial ecosystems, have not been well studied. In this paper, U-Pb ages of 2357 detrital zircons from nine Late Cretaceous terrestrial basins in China are collected. Based on provenance analysis on these detrital zircons, the distribution pattern of the Late Cretaceous paleoriver systems and provenance directions are discussed. The results show that there existed SW-NE oriented, large-scale river systems in southern China in the Late Cretaceous. Contrary to the eastward and southeastward drainage directions of modern river systems, the Late Cretaceous paleoriver systems drained from an inferred coastal plateau in eastern China to the west and southwest, and resulted in widespread web-like riverbank and floodplain deposits in southern China. In contrast, basins in northern China were separated by paleo-uplifts, from which most of the sediments were derived. The drainage systems of the studied basins in northern China were largely independent from each other. These complex drainage basins in northern China created many isolated habitats where a unique East Asia hadrosaur fauna evolved. In contrast, the riverine deposits of the river systems in southern China are featured by fossils of dinosaur eggs and footprints, and only few dinosaur skeleton fossils. This feature probably resulted from the hot and arid climate in southern China, which was not suitable to hadrosaur-dominated dinosaurs as a perennial habitat. They instead may have migrated through or laid eggs along the river systems seasonally.
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