A New Giant Titanosauria (Dinosauria: Sauropoda) from the Late Cretaceous Bauru Group, Brazil

The origin of an invasive air sac system in sauropodomorph dinosaurs

One of the most remarkable features in sauropod dinosaurs relates to their pneumatized skeletons permeated by a bird-like air sac system. Many studies described the late evolution and diversification of this trait in mid to late Mesozoic forms but few focused on the origin of the invasive respiratory diverticula in sauropodomorphs. Fortunately, it is possible to solve this thanks to the boom of new species described in the last decade as well as the broad accessibility of new technologies. Here we analyze the unaysaurid sauropodomorph Macrocollum itaquii from the Late Triassic (early Norian) of southern Brazil using micro-computed tomography. We describe the chronologically oldest and phylogenetically earliest unambiguous evidence of an invasive air sac system in a dinosaur. Surprisingly, this species presented a unique pattern of pneumatization in non-sauropod sauropodomorphs, with pneumatic foramina in posterior cervical and anterior dorsal vertebrae. This suggests that patterns of pneumatization were not cladistically consistent prior to the arrival of Jurassic eusauropods. Additionally, we describe the protocamerae tissue, a new type of pneumatic tissue with properties of both camellae and camerae. This reverts the previous hypothesis which stated that the skeletal pneumatization first evolved into camarae, and derived into delicate trabecular arrangements. This tissue is evidence of thin camellate-like tissue developing into larger chambers. Finally, Macrocollum is an example of the gradual evolution of skeletal tissues responding to the fastly specializing Respiratory System of saurischian dinosaurs.

New specimens of Baurutitan britoi and a taxonomic reassessment of the titanosaur dinosaur fauna (Sauropoda) from the Serra da Galga Formation (Late Cretaceous) of Brazil

The description of new titanosaur specimens unearthed from deposits of the Serra da Galga Formation (Bauru Group, Late Cretaceous) at the BR-262 site, near Peirópolis (Uberaba, Minas Gerais State, Brazil), sheds light on the taxonomy of two taxa previously known from the same area and geological unit: Baurutitan britoi and Trigonosaurus pricei. A comparative revision indicates that T. pricei represents a junior synonym of Ba. britoi, and that the BR-262 specimens belong to that latter species. The information provided by the new specimens also revealed that the paratype of T. pricei (MCT 1719-R), a caudal vertebral series, actually represents a new taxon, named here as Caieiria allocaudata gen. et sp. nov.

First titanosaur dinosaur nesting site from the Late Cretaceous of Brazil

Titanosaurs were successful herbivorous dinosaurs widely distributed in all continents during the Cretaceous, with the major diversity in South America. The success of titanosaurs was probably due to several physiological and ecological factors, in addition to a series of morphological traits they achieved during their evolutionary history. However, the generalist nesting behaviour using different palaeoenvironments and strategies was key to accomplish that success. Titanosaur nesting sites have been found extensively around the world, with notable records in Spain, France, Romania, India, and, especially, Argentina. Here, we describe the first titanosaur nesting site from the Late Cretaceous of Brazil that represents the most boreal nesting site for South America. Several egg-clutches, partially preserved, isolated eggs and many eggshell fragments were discovered in an Inceptisol palaeosol profile of the mining Lafarge Quarry, at the Ponte Alta District (Uberaba Municipality, Minas Gerais State), corresponding to the Serra da Galga Formation (Bauru Group, Bauru Basin). Although classical mechanical preparation and CT scans have not revealed embryonic remains in ovo, the eggs and eggshell features match those eggs containing titanosaurian embryos found worldwide. The morphology of the egg-clutches and observations of the sedimentary characteristics bolster the hypothesis that these sauropods were burrow-nester dinosaurs, as was already suggested for the group based on other nesting sites. The egg-clutches distributed in two levels along the Lafarge outcrops, together with the geopalaeontological data collected, provide clear evidence for the first colonial nesting and breeding area of titanosaur dinosaurs in Brazil.

Exquisite air sac histological traces in a hyperpneumatized nanoid sauropod dinosaur from South America

This study reports the occurrence of pneumosteum (osteohistological structure related to an avian-like air sac system) in a nanoid (5.7-m-long) saltasaurid titanosaur from Upper Cretaceous Brazil. We corroborate the hypothesis of the presence of an air sac system in titanosaurians based upon vertebral features identified through external observation and computed tomography. This is the fifth non-avian dinosaur taxon in which histological traces of air sacs have been found. We provided a detailed description of pneumatic structures from external osteology and CT scan data as a parameter for comparison with other taxa. The camellate pattern found in the vertebral centrum (ce) of this taxon and other titanosaurs shows distinct architectures. This might indicate whether cervical or lung diverticula pneumatized different elements. A cotylar internal plate of bone tissue sustains radial camellae (rad) in a condition similar to Alamosaurus and Saltasaurus. Moreover, circumferential chambers (cc) near the cotyle might be an example of convergence between diplodocoids and titanosaurs. Finally, we also register for the first time pneumatic foramina (fo) and fossae connecting camellate structures inside the neural canal in Titanosauria and the second published case in non-avian dinosaurs. The extreme pneumaticity observed in this nanoid titanosaur contrasts with previous assumptions that this feature correlates with the evolution of gigantic sizes in sauropodomorphs. This study reinforces that even small-bodied sauropod clades could present a hyperpneumatized postcranial skeleton, a character inherited from their large-bodied ancestors.

The first dinosaurs from the Early Cretaceous Hami Pterosaur Fauna, China

The Early Cretaceous Hami Pterosaur Fauna in Northwest China preserves a large number of specimens of the sexually dimorphic pteranodontoid pterosaur Hamipterus tianshanensis, including 3D eggs and embryos. During the last decade, several more fossils have been collected in this area, including three somphospondylan sauropod specimens. The first is Silutitan sinensis gen. et sp. nov., which consists of an articulated middle to posterior cervical vertebrae series. The second, Hamititan xinjiangensis gen. et sp. nov., consists of an incomplete articulated caudal sequence that could be assigned to lithostrotian titanosaurs based on the strongly procoelous caudal vertebrae with lateral concave surface, as well as marked ventrolateral ridges. The third specimen consists of four sacral vertebral elements, apparently unfused, with exposed camellate internal bone and regarded as somphospondylan. Cladistic analyses based on different datasets recovered Silutitan sinensis as an euhelopodid closely related to Euhelopus and Hamititan xinjiangensis as a titanosaur. Besides the pterosaur Hamipterus and one theropod tooth, these dinosaurs are the first vertebrates reported in this region, increasing the diversity of the fauna as well as the information on Chinese sauropods, further supporting a widespread diversification of somphospondylans during the Early Cretaceous of Asia.

Two Late Cretaceous sauropods reveal titanosaurian dispersal across South America

South American titanosaurians have been central to the study of the evolution of Cretaceous sauropod dinosaurs. Despite their remarkable diversity, the fragmentary condition of several taxa and the scarcity of records outside Patagonia and southwestern Brazil have hindered the study of continental-scale paleobiogeographic relationships. We describe two new Late Cretaceous titanosaurians from Quebrada de Santo Domingo (La Rioja, Argentina), which help to fill a gap between these main areas of the continent. Our phylogenetic analysis recovers both new species, and several Brazilian taxa, within Rinconsauria. The data suggest that, towards the end of the Cretaceous, this clade spread throughout southern South America. At the same locality, we discovered numerous accumulations of titanosaurian eggs, likely related to the new taxa. With eggs distributed in three levels along three kilometres, the new site is one of the largest ever found and provides further evidence of nesting site philopatry among Titanosauria.

CroSSED sequence, a new tool for 3D processing in geosciences using the free software 3DSlicer

The scientific application of 3D imaging has evolved significantly over recent years. These techniques make it possible to study internal features by non-destructive analysis. Despite its potential, the development of 3D imaging in the Geosciences is behind other fields due to the high cost of commercial software and the scarce free alternatives. Most free software was designed for the Health Sciences, and the pre-settled workflows are not suited to geoscientific materials. Thus, an outstanding challenge in the Geosciences is to define workflows using free alternatives for Computed Tomography (CT) data processing, promoting data sharing, reproducibility, and the development of specific extensions. We present CroSSED, a processing sequence for 3D reconstructions of CT data, using 3DSlicer, a popular application in medical imaging. Its usefulness is exemplified in the study of burrows that have low-density contrast with respect to the host sediment. For geoscientists who have access to CT data and wish to reconstruct 3D structures, this method offers a wide range of possibilities and contributes to open-science and applied CT studies.

A new African Titanosaurian Sauropod Dinosaur from the middle Cretaceous Galula Formation (Mtuka Member), Rukwa Rift Basin, Southwestern Tanzania

The African terrestrial fossil record has been limited in its contribution to our understanding of both regional and global Cretaceous paleobiogeography, an interval of significant geologic and macroevolutionary change. A common component in Cretaceous African faunas, titanosaurian sauropods diversified into one of the most specious groups of dinosaurs worldwide. Here we describe the new titanosaurian Mnyamawamtuka moyowamkia gen. et sp. nov. from the Mtuka Member of the Galula Formation in southwest Tanzania. The new specimen preserves teeth, elements from all regions of the postcranial axial skeleton, parts of both appendicular girdles, and portions of both limbs including a complete metatarsus. Unique traits of M. moyowamkia include the lack of an interpostzygapophyseal lamina in posterior dorsal vertebrae, pronounced posterolateral expansion of middle caudal centra, and an unusually small sternal plate. Phylogenetic analyses consistently place M. moyowamkia as either a close relative to lithostrotian titanosaurians (e.g., parsimony, uncalibrated Bayesian analyses) or as a lithostrotian and sister taxon to Malawisaurus dixeyi from the nearby Aptian? Dinosaur Beds of Malawi (e.g., tip-dating Bayesian analyses). M. moyowamkia shares a few features with M. dixeyi, including semi-spatulate teeth and a median lamina between the neural canal and interpostzygapophyseal lamina in anterior dorsal vertebrae. Both comparative morphology and phylogenetic analyses support Mnyamawamtuka as a distinct and distant relative to Rukwatitan bisepultus and Shingopana songwensis from the younger Namba Member of the Galula Formation with these results largely congruent with newly constrained ages for the Mtuka Member (Aptian–Cenomanian) and Namba Member (Campanian). Coupled with recent discoveries from the Dahkla Oasis, Egypt (e.g., Mansourasaurus shahinae) and other parts of continental Afro-Arabia, the Tanzania titanosaurians refine perspectives on the development of African terrestrial faunas throughout the Cretaceous—a critical step in understanding non-marine paleobiogeographic patterns of Africa that have remained elusive until the past few years.

How has our knowledge of dinosaur diversity through geologic time changed through research history?

Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abundance curve, which are largely dependent on databases compiled from the primary published literature. However, how these ‘corrected’ diversity patterns are influenced by the history of publication remains largely unknown. Here, we investigate the influence of publication history between 1991 and 2015 on our understanding of dinosaur evolution using raw diversity estimates and shareholder quorum subsampling for the three major subgroups: Ornithischia, Sauropodomorpha, and Theropoda. We find that, while sampling generally improves through time, there remain periods and regions in dinosaur evolutionary history where diversity estimates are highly volatile (e.g. the latest Jurassic of Europe, the mid-Cretaceous of North America, and the Late Cretaceous of South America). Our results show that historical changes in database compilation can often substantially influence our interpretations of dinosaur diversity. ‘Global’ estimates of diversity based on the fossil record are often also based on incomplete, and distinct regional signals, each subject to their own sampling history. Changes in the record of taxon abundance distribution, either through discovery of new taxa or addition of existing taxa to improve sampling evenness, are important in improving the reliability of our interpretations of dinosaur diversity. Furthermore, the number of occurrences and newly identified dinosaurs is still rapidly increasing through time, suggesting that it is entirely possible for much of what we know about dinosaurs at the present to change within the next 20 years.