Search

The Kirkwood Formation of South Africa has long been recognized as having the potential to fill an important gap in the Mesozoic terrestrial fossil record. As one of the few fossil-bearing deposits from the lowermost Cretaceous, the Kirkwood Formation provides critical information on terrestrial ecosystems at the local, subcontinental (southern Gondwana), and global scale during this poorly sampled time interval. However, until recently, the dinosaurian fauna of the Kirkwood Formation, especially that pertaining to Sauropoda, has remained essentially unknown. Here we present comprehensive descriptions of several relatively well-preserved sauropod vertebrae collected from exposures throughout the formation. We identify at least four taxonomically distinct groups of sauropod, comprising representatives of Diplodocidae, Dicraeosauridae, Brachiosauridae, and a eusauropod that belongs to neither Diplodocoidea nor Titanosauriformes. This represents the first unequivocal evidence of these groups having survived into the earliest Cretaceous of Africa. The taxonomic composition of the Kirkwood Formation shows strong similarities to Upper Jurassic deposits, and raises questions regarding the taxonomic decline across the Jurassic/Cretaceous boundary that has been previously inferred for Sauropoda. Investigation of the sauropod fossil record of the first three geological stages of the Cretaceous suggests that reconstruction of sauropod macroevolutionary patterns is complicated by a combination of sampling bias, an uneven and poorly dated rock record, and spatiotemporal disparity in the global disappearance of certain sauropod groups. Nonetheless, the close ecological relationship consistently observed between Brachiosauridae and Diplodocidae, as well as their approximately synchronous decline, suggests some equivalence in response to the changing faunal dynamics of the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The osteology of Diamantinasaurus matildae , the most complete Cretaceous sauropod described from Australia to date, is comprehensively reassessed. The preparation of additional material from the type locality, pertaining to the same individual as the holotype, sheds light on the morphology of the axial skeleton and provides additional information on the appendicular skeleton. The new material comprises two dorsal vertebrae, an incomplete sacrum (including four partial coalesced vertebrae), the right coracoid, the right radius, an additional manual phalanx, and a previously missing portion of the right fibula. In this study we identify thirteen autapomorphic characters of Diamantinasaurus , and an additional five characters that are locally autapomorphic within Titanosauriformes. This work provided an opportunity to revisit the phylogenetic placement of Diamantinasaurus . In two independent data matrices, Diamantinasaurus was recovered within Lithostrotia. One analysis resolved Diamantinasaurus as the sister taxon to the approximately coeval Tapuiasaurus from Brazil, whereas the second analysis recovered Diamantinasaurus as the sister taxon to Opisthocoelicaudia from the latest Cretaceous of Mongolia. The characters supporting the recovered relationships are analysed, and the palaeobiogeographical implications of the lithostrotian status of Diamantinasaurus are explored. A brief review of the body fossil record of Australian Cretaceous terrestrial vertebrates suggests close ties to South America in particular, and to Gondwana more generally. [ABSTRACT FROM AUTHOR]

Abstract: Determining the relationships of mid-Late Cretaceous African taxa is central to understanding the timing and resultant palaeobiogeographical patterns of Gondwanan fragmentation. The early Late Cretaceous (Cenomanian) Kem Kem beds of southeastern Morocco preserve a diverse vertebrate fauna, including sauropod dinosaurs. Sauropod material includes the holotype of the rebbachisaurid diplodocoid Rebbachisaurus garasbae and fragmentary remains representing indeterminate titanosauriforms and rebbachisaurids. Here, we describe two new specimens from the Kem Kem beds. A dorsal neural arch with complex internal pneumaticity is tentatively attributed to a somphospondylan titanosauriform. A caudal vertebra possessing several rebbachisaurid synapomorphies is excavated by a large and pervasive lateral pneumatic foramen, a feature undocumented in other rebbachisaurids. However, caudal vertebrae are currently unknown for the sympatric R. garasbae, so this element could be referable to that taxon or a second, previously unknown, rebbachisaurid species. Interestingly, this new caudal vertebra displays a mosaic of features otherwise restricted to limaysaurine or nigersaurine rebbachisaurids, suggesting a placement basal to these clades, which is the position usually recovered for R. garasbae in phylogenetic analyses. A review of the mid-Cretaceous African sauropod fossil record removes the Cretaceous record of dicraeosaurids from Africa, restricting this clade to a single post-Jurassic occurrence in Argentina. All diagnostic sauropod remains can be attributed to titanosauriforms or rebbachisaurids. Whereas rebbachisaurids were seemingly restricted to northwestern Africa and disappeared post-Cenomanian, titanosauriforms were widespread across the African continent and survived until the latest Cretaceous. The development of the mid-Cretaceous Trans-Saharan Seaway might have acted as a dispersal barrier for rebbachisaurids and other vertebrate groups. In contrast, titanosauriforms might have been able to cross this barrier, but it is possible that they were also unable to disperse, and that northwestern African titanosauriforms were not closely related to taxa from the rest of the African continent. New materials and a better understanding of titanosaur interrelationships will be crucial in teasing these scenarios apart. [Copyright &y& Elsevier]

Abstract: Rebbachisauridae is a poorly understood clade of diplodocoid sauropod dinosaurs, currently known only from the Cretaceous of Africa, Europe and South America. European representatives are particularly rare and fragmentary. Here, we report an anterior caudal vertebra from the Barremian (Early Cretaceous) Wessex Formation of the Isle of Wight, off the southern coast of England. This specimen possesses several features known only in rebbachisaurids and shares two synapomorphies with the Afro-European taxa Demandasaurus darwini and Nigersaurus taqueti, both pertaining to the morphology of the neural spine. These features are the development of triangular lateral processes and the presence of an elliptical fossa on the lateral surface, bounded by the lateral lamina and postspinal rugosity. The Isle of Wight specimen also shares several features solely with Demandasaurus, indicating a close relationship with the Spanish taxon. These include the presence of a hyposphenal ridge, as well as an anteriorly excavated caudal rib that is restricted almost entirely to the neural arch. However, it differs from Demandasaurus in a number of ways, including the lack of excavation on the posterior surface of the caudal rib, the orientation of the neural spine, and the composition and morphology of the lateral lamina. In addition, the Isle of Wight vertebra possesses one potential autapomorphy: bifurcation of the elliptical fossa on the neural spine. However, because of the fragmentary nature of the material, a new name is not erected. Along with Demandasaurus and Histriasaurus boscarollii, this caudal vertebra indicates the presence of at least three European rebbachisaurid taxa and provides new anatomical information on this enigmatic clade of sauropod dinosaurs. [Copyright &y& Elsevier]

The article outlines two types of metric for quantifying the completeness and the quality of the sauropodomorph dinosaur fossil remains through geological and historical time. In this study, early Carnian until late Carnian-Norian exhibited high completeness level attributed to the presence of well-preserved prosauropod and basal sauropod skeletons from the upper Elliot and Clarens formation of South Africa and lower Lufeng Formation of the People's Republic of China. Rhaetian, meanwhile, had lower completeness level. Analysis showed the average completeness percentages for a selection of sauropodomorh clades and grades. Results also suggest the correlation of high sea level with low average completeness scores during the control of the quality of sauropodomorph fossil record.

The article discusses a study which presented a quantitative paleoecological analysis of environmental associations in sauropod dinosaurs. Findings revealed a positive association between non-titanosaurs and coastal environments, between titanosaurs and inland environments, between narrow-gauge trackways and coastal environments, and between wide-gauge trackways and inland environments. Results showed the preference of titanosaur sauropods for inland environments such as fluvio-lacustrine systems, while non-titanosaurs preferred coastal environments such as carbonate platforms. Body fossil records such as that of carcasses and trackway data sets supported the environmental preferences in sauropod dinosaurs.

Abstract: Rebbachisauridae is one of the most enigmatic and poorly understood clades of sauropod dinosaurs. They are considered to be basal diplodocoids, are known solely from the Cretaceous (Hauterivian-Coniacian), and have only been recovered from Africa, South America, and Europe. As a result of their extreme skeletal reduction, rebbachisaurid material is highly susceptible to destructive taphonomic processes and thus most remains are highly incomplete and fragmentary. Previous remains attributed to rebbachisaurids from England are restricted to isolated teeth. Here a sauropod scapula from the Lower Cretaceous (Barremian) Wessex Formation of the Isle of Wight, England, is described. Although incomplete, this scapula possesses both the extreme dorsoventral expansion of the scapular blade and the “hook”-like acromial process that are characteristic of rebbachisaurids. This study has also enabled the recognition of a putative local synapomorphy of Rebbachisauridae, with the highest point on the dorsal margin of the scapula blade equal to or exceeding that of the dorsal margin of the proximal plate. This scapula is one of the oldest known examples of a rebbachisaurid and represents the first postcranial remains of this clade to be described from the United Kingdom. In addition, it provides further support for the presence of rebbachisaurids in the Early-mid Cretaceous of Europe. [Copyright &y& Elsevier]