Sauropod Research Articles

A new chelid turtle with an ornamented bony shell (Pleurodira: Chelidae) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina

ABSTRACT We describe Baalemys mansillai gen. et sp. nov. a chelid turtle, based on an articulated shell from the Portezuelo Formation of the Baal locality, northern shore of Barreales lake, Neuquén Province, Argentina. Baalemys mansillai gen. et sp. nov. is distinguished from other chelids by its oval shape, moderate size, distinctive granulated ornamentation, narrow nuchal plate, first hexagonal neural with short posterolateral margins, a second neural plate that is a regular hexagon, and a posterior lobe that is longer than both the anterior lobe and the bridge. This unique combination of features supports the establishment of a new genus and species. Baalemys mansillai gen. et sp. nov was discovered in the Baal locality with sauropod dinosaurs, theropod dinosaurs, crocodiles, pelomedusoid turtles and other genera of chelids; a similar biota was identified in other localities of the Portezuelo Formation. The identification of Baalemys mansillai gen. et sp. nov. significantly adds to our knowledge of the diversity of pleurodiran turtles from the Portezuelo Formation, the Neuquén Basin, and the broader Patagonian region.

Hydrologically sensitive carbonates: Tectonic and groundwater controls on synrift sedimentation in the Late Jurassic–Early Cretaceous of the western Cameros Basin, Northern Spain

AbstractBasin hydrology and subcrop are key controls on carbonate sedimentation in continental basins. Hydrologically sensitive carbonates can record groundwater fluctuations within an aquifer in deep time. Late Jurassic extension, footwall uplift, erosion and karstification of marine Jurassic carbonates in the western Cameros Basin (Spain) saw deposition of ?Upper Kimmeridgian‐Tithonian syntectonic alluvial fan deposits (Señora de Brezales Formation). Biogenic laminar calcretes and phreatophytic rhizocretions record roots exploiting capillary fringe groundwater. Progressive infill of rift topography and footwall erosion lowered sedimentary gradients and clastic supply during deposition of the ?Tithonian–Berriasian Rupelo Formation. Distal alluvial marls (Las Viñas Member) contain charophytes, with 2 m thick carbonate lenses at the top reflecting intermittent rise of groundwater in ponds on the basin floor. Stacked palustrine limestones with rare charophytes and laminar calcretes (Ladera Member) record overstep of seasonal carbonate wetlands onto basin margins and footwall highs with intense pedogenetic modification during lengthy seasonal exposure. Overlying Berriasian charophyte‐ostracod wackestones, displaying microkarst cavities and interbedded intraclastic conglomerates, with vivianite sauropod bones, footprints and polygonal desiccation cracks at the top (Mambrillas de Lara Member) record open lacustrine conditions with limited subaerial exposure and high water tables. Desiccation‐cracked limestones and marls with correlatable evaporite horizons (Rio Cabrera Member) contain marginal marine foraminifera and dasycladaceae at the top. Lagoonal conditions reflected transgression to seaward and intermittent marine connection via the Basco‐Cantabrian Basin. The distribution and thicknesses of hydrologically sensitive carbonates reflected onlap onto a faulted and karstified marine Jurassic carbonate pediment and the subtle influence on hydroperiod of fault (and potentially localised Triassic salt) controlled differential subsidence and transgressive groundwater rise. Hydrological facies evolution reflects progressive basin infilling and eustasy beyond. Transitions in this continental succession from clastic to carbonate facies and from closed to open hydrology record hydrological change over time rather than contemporaneous deposition under Walther's Law.

A new sauropod dinosaur hindlimb from the Lower Cretaceous Wessex Formation, Isle of Wight, UK.

The Barremian-aged Wessex Formation of the Isle of Wight, UK, offers a globally significant glimpse into the sauropod dinosaur faunas of the early Cretaceous. These deposits have yielded specimens of several neosauropod lineages, such as rebbachisaurids, titanosauriforms (including some of the earliest titanosaur remains), and possible flagellicaudatans. Here, we report an undescribed sauropod partial hindlimb from the Wessex Formation (NHMUK PV R16500) and analyse its phylogenetic affinities. This hindlimb preserves the left tibia, astragalus and pes, lacking only a few phalanges. NHMUK PV R16500 can be diagnosed based on two autapomorphies: an unusually high distal end to midshaft transverse width ratio in metatarsals III and IV, and the presence of small bump-like projections located in the centre of the proximal articular surfaces of the unguals of pedal digits I and II. The phylogenetic affinities of NHMUK PV R16500 are uncertain: although our analyses recover it as an early-branching somphospondylan, a single character change moves it to close to Flagellicaudata when extended implied weighting is applied. The possibility of flagellicaudatan affinities for NHMUK PV R16500 implies a potential ghost lineage that survived the Jurassic/Cretaceous boundary; however, we present evidence that the somphospondylan position is more probable and should be preferred.

Biomechanics and morphological comparisons of the caudal region of titanosaurs from the Cretaceous of Brazil: Paleobiology and paleoecology inferences.

Biomechanical studies in sauropod dinosaurs are mainly focused on neck posture and feeding strategy. Few works investigate other aspects such as tail movement and function, especially in the clade Titanosauria, the most diverse within Neosauropoda. This study applied biomechanical concepts of neutral pose (cartilaginous neutral pose) and range of motion to verify the shape and direction of the caudal region of the advanced titanosaurs Adamantisaurus mezzalirai and Baurutitan britoi, in addition to comparing it with other titanosaurs (e.g., Arrudatitan maximus, Lirainosaurus astibiae, and Trigonosaurus pricei). As a result, the tails analyzed have a sigmoidal-convex shape, probably close to the ground (but not touching it). The sigmoidal-convex shape could increase the moment arm for the M. caudofemoralis longus, making it possible to use the tail as a fifth stabilizing member. This work expands our knowledge about sauropod dinosaurs by exposing a diversity of shapes for the tails of titanosaur sauropods and brings new possibilities for how these dinosaurs could use their tails.

Revealing the use of dental indices to infer taxonomic variation in sauropod dinosaurs

AbstractSauropod teeth are commonly categorized taxonomically by two well‐established measurement indices: slenderness index (SI; apicobasal height/mesiodistal width), which quantifies breadth, and compression index (CI; labiolingual width/mesiodistal width), which quantifies cross‐sectional circularity. Although both indices are used to infer high‐level taxonomic affinities, little is known about the linear relationships between the constituent measurements or how the indices vary intra‐cranially and at lower taxonomic levels. Here, we evaluate these relationships using a novel dataset of sauropod teeth (N = 898) spanning all major sauropod groups. Results for both indices indicate significant differential scaling within Sauropodomorpha, both in slope and elevation. Broad‐crowned sauropods mostly display positive allometry in SI compared to isometry in narrow‐crowned sauropods. However, this distinction is less clear with CI as most sauropods display isometry, whilst non‐sauropod sauropodomorphs (e.g. Plateosauridae) display positive allometry. An anova reveals SI varies significantly with genus and tooth position. Specifically, jaw type (maxilla and dentary) is significant within Plateosauridae, whilst tooth position is significant within titanosaurs. Overall, variation within CI is restricted to genus. Our findings reveal that whilst indices have taxonomic utility, there are caveats. The measurements used to calculate the indices exhibit significant allometry, indicating that index values are size‐dependent. Furthermore, the indices may not accurately reflect size heterodont conditions present among early‐branching sauropodomorphs. Our study highlights the importance of quantifying taxonomic relationships of measurement data, which can be used to inform hypotheses regarding the physiological and palaeoecological drivers influencing tooth shape evolution.

A new ichnosite and ichnogenus from the Lower Cretaceous Rio do Peixe Basin, Brazil, with novel insights into the evolution of Titanosauriformes

ABSTRACT Sauropods were a successful group of herbivorous dinosaurs that colonised all continents throughout the Mesozoic. At first glance, the organisms in this group present a conservative shape of quadrupedal animals with elongated necks and tails. However, there was great diversification in the morphology of sauropods, which is still poorly understood in detail, especially during the Early Cretaceous. In this study, we describe a new ichnosite dated from the earliest stages of the Cretaceous of Brazil. The site includes a well-preserved trackway of a large sauropod dinosaur, with manus and pes prints, as well as tracks of theropods and indeterminate tetrapods. The sauropod trackway shows a unique set of characteristics that allowed the erection of a new ichnogenus and ichnospecies, Sousatitanosauripus robsoni igen. nov. et isp. nov. The probable trackmaker was a Titanosauriformes with a mosaic of basal and advanced features, bringing new insights into the diversity and evolution of the group.

Sauropod dinosaur tracks from the Purbeck Group (Early Cretaceous) of Spyway Quarry, Dorset, UK.

Dinosaur tracks have a long history of discovery and study in the UK, but track sites for sauropodomorph dinosaurs-the group that included the giant, graviportal herbivorous sauropods-are comparatively rare. Here, we provide a description of a sauropod dinosaur track site at Spyway Quarry in Dorset, southern England. The tracks at Spyway were discovered in the late 1990s and occur in the Stair Hole Member of the Durlston Formation in the Purbeck Limestone Group, of earliest Cretaceous age. More than 130 individual tracks of large sauropod dinosaurs are present at the site, but they are generally poorly preserved and do not form clear trackways, although it is likely that they represent multiple individuals. They provide further evidence for sauropods living in or passing through coastal lagoonal environments. Although poorly preserved, Spyway represents the largest in situ dinosaur track site currently accessible within the Purbeck Group, with considerable potential for further discoveries through ongoing quarrying in the surrounding area.

The axial biomechanics of Trigonosaurus pricei (Neosauropoda: Titanosauria) and the importance of the cervical–dorsal region to sauropod high-browser feeding strategy

Abstract Trigonosaurus pricei is a small to medium-sized sauropod dinosaur (Sauropoda: Titanosauria) from the Late Cretaceous Bauru Group of Brazil that is known from a significant amount of recovered axial elements [four cervical vertebrae, 10 dorsal vertebrae, sacrum (MCT 1488-R), and 10 caudal vertebrae (MCT 1719-R)]. In this biomechanical work, we approach the hypothesis of the cartilaginous neutral pose and the range of motion of the axial series of Trigonosaurus. The results show that this sauropod could be capable of high elevation of the neck resulting from morphological adaptations of the cervicodorsal region on dorsal (D) vertebrae D2 and D3 (e.g. postzygapophyses of D2 positioned over the vertebral centrum and prezygapophyses of D3 over the anterior vertebral centrum). This implies that D2 articulates (cartilaginous neutral posture) with D3 only at a strong dorsally directed angle, resulting in a shift in the direction of the neck to a more elevated posture. Furthermore, the tail attributed to Trigonosaurus as a paratype could be oriented in the horizontal ‘direction’ and presented a sigmoidal ‘shape’. This work contributes generally to the understanding of variation in the body plan of sauropods and, more specifically, to the feeding strategy of small and medium-sized titanosaurs from semi-arid regions of Gondwana.

Did large foraging migrations favor the enormous body size of giant sauropods? The case of Turiasaurus

We propose that the huge sizes attained by many sauropod dinosaurs can be explained in the context of a climate characterized by pronounced seasonal changes. Under these conditions, the large herbivores would have become migratory, forced to move great distances during the drier times of year, in which case large body size becomes an adaptive advantage, since large home ranges and the ability to travel great distances increase with size. In this way, the need for a large foraging radius is a potent source of selection for larger size, and the capacity for sauropods to migrate and explore new territory was significantly higher than in extant herbivores. Examples discussed are Turiasaurus riodevensis and Camarasaurus lentus; some of their anatomical structures, such as vertebral neural extensions and crests associated with nasal cavities, can also be explained under this scenario, as adaptations to drought conditions.

The first mamenchisaurid from the Upper Jurassic Dongxing Formation of Guangxi, southernmost China

ABSTRACT A new mamenchisaurid sauropod dinosaur, Jingia dongxingensis gen. et sp. nov. from the Upper Jurassic of Southernmost China is reported here. The holotype consists of partly preserved dorsal, sacral, and caudal vertebrae, left and right ulna, and right femur. Anatomical comparison and phylogenetic analysis indicate that the new taxon belongs to Mamenchisauridae and bears a unique combination of characteristics, such as the ratio of the length of the neural spine to the narrowest width of the neural arch of the dorsal vertebra is about 4.4; sacral centrum is opisthocoelous with shallow depression exists on the lateral surface; centrum of anterior caudal vertebrae are amphicoelous, and the articular surfaces are transversely compressed; the anterolateral and anteromedial processes of the ulna are generally perpendicular in proximal view. Phylogenetically, Jingia dongxingensis gen. et sp. nov. is located at the later diverged position in Mamenchisauridae. This discovery increases the diversity of Mamenchisauridae and provides additional information to help understand the evolutionary radiation of eusauropods in China. It also indicates that this lineage is more competitive than penecontemporaneous neosauropods to dominate the Late Jurassic of East Asia.

Reappraisal of sauropod dinosaur diversity in the Upper Cretaceous Winton Formation of Queensland, Australia, through 3D digitisation and description of new specimens.

Skeletal remains of sauropod dinosaurs have been known from Australia for over 100 years. Unfortunately, the classification of the majority of these specimens to species level has historically been impeded by their incompleteness. This has begun to change in the last 15 years, primarily through the discovery and description of several partial skeletons from the Cenomanian-lower Turonian (lower Upper Cretaceous) Winton Formation in central Queensland, with four species erected to date: Australotitan cooperensis, Diamantinasaurus matildae, Savannasaurus elliottorum, and Wintonotitan wattsi. The first three of these appear to form a clade (Diamantinasauria) of early diverging titanosaurs (or close relatives of titanosaurs), whereas Wintonotitan wattsi is typically recovered as a distantly related non-titanosaurian somphospondylan. Through the use of 3D scanning, we digitised numerous specimens of Winton Formation sauropods, facilitating enhanced comparison between type and referred specimens, and heretofore undescribed specimens. We present new anatomical information on the holotype specimen of Diamantinasaurus matildae, and describe new remains pertaining to twelve sauropod individuals. Firsthand observations and digital analysis enabled previously proposed autapomorphic features of all four named Winton Formation sauropod species to be identified in the newly described specimens, with some specimens exhibiting putative autapomorphies of more than one species, prompting a reassessment of their taxonomic validity. Supported by a specimen-level phylogenetic analysis, we suggest that Australotitan cooperensis is probably a junior synonym of Diamantinasaurus matildae, but conservatively regard it herein as an indeterminate diamantinasaurian, meaning that the Winton Formation sauropod fauna now comprises three (rather than four) valid diamantinasaurian species: Diamantinasaurus matildae, Savannasaurus elliottorum, and Wintonotitan wattsi, with the latter robustly supported as a member of the clade for the first time. We refer some of the newly described specimens to these three species and provide revised diagnoses, with some previously proposed autapomorphies now regarded as diamantinasaurian synapomorphies. Our newly presented anatomical data and critical reappraisal of the Winton Formation sauropods facilitates a more comprehensive understanding of the mid-Cretaceous sauropod palaeobiota of central Queensland.

A previously unreported form of dorsal rib pneumaticity in Apatosaurus (Dinosauria: Sauropoda) and implications for pneumatic variation among diplodocid dorsal ribs

ABSTRACT Postcranial pneumaticity is interpreted as a weight saving adaptation in sauropod dinosaurs, especially in the vertebral column. In some derived sauropods pneumatic features also occur on vertebral ribs. While pneumatic ribs are considered diagnostic of the clade Titanosauriformes, they are also infrequently found in diplodocid sauropods. Here, we describe a partial dorsal rib IV or V referable to Apatosaurus sp. that exhibits a series of superficial pneumatic fossae along its posterior surface. These fossae differ from the morphology found in other pneumatic dorsal ribs of diplodocids, including other apatosaurines and Supersaurus. Moreover, the pneumatic features of this rib are more distally located from the capitulum and tuberculum than in other diplodocids and titanosaurs. Based on our findings, we propose that rib pneumaticity among apatosaurine sauropods (and potentially all diplodocids) is individually variable, in addition to being a function of ontogeny. More broadly, we conclude that rib pneumaticity among diplodocids is morphologically variable when present and individually expressed rather than being ubiquitous throughout the clade. Our findings are consistent with the hypothesis that pneumatic ribs evolved independently between Diplodocidae and Titanosauriformes and make for poor clade-level characters among diplodocids.

Sauropod manus and pes prints with impressions of integument from the Ravenscar Group (Middle Jurassic) of Whitby, Yorkshire, England

Well-defined manus and pes print couple, likely from a trackway attributable to a sauropod dinosaur are revealed on a fallen block of Ravenscar Group sandstones in a cliff fall at Whitby, Yorkshire, England. The pes print displays four, possibly five toes and thus closely resembles that of the ichnogenera Brontopodus and Parabrontopodus. They are here referred to Brontopodus cf. pentadactylus Kim and Lockley, 2012. Impressions of a scaled integument are present around parts of the pes. The prints were likely made by a sauropod with a hip height of between 1.92 m and 2.83 m.

A new titanosaurian sauropod, Gandititan cavocaudatus gen. et sp. nov., from the Late Cretaceous of southern China

Large quadrupedal sauropod dinosaurs of the group Titanosauria were globally distributed in the Late Cretaceous. Many titanosaurian species have been discovered in eastern Asia, but most of them are controversial and represented by poorly preserved remains. Here, we describe a new titanosaur, Gandititan cavocaudatus gen. et sp. nov., based on a partial skeleton recovered from the lower Upper Cretaceous of Ganxian County, Ganzhou City, southern China, and comprising six articulated cervical vertebrae, two partial dorsal vertebrae, and a complete sacrum preserved in articulation with the first 17 caudal vertebrae and part of the right pelvis. Gandititan can be diagnosed on the basis of the following autapomorphies: long and narrow fossae present on the dorsal and ventral parts of the lateral surfaces of the cervical centra, sacral neural spines forming a dorsal platform with wave-shaped lateral margins, anteriormost six caudal vertebrae with bifurcated neural spines, the presence of prominent triangular flanges on the transverse processes of the anteriormost caudal vertebrae, a pair of slit-like foramina present on the ventral surface of each anterior caudal centrum, lateral surfaces of neural arches strongly excavated, additional spinoprezygapophyseal laminae present, and a prominent lamina extending horizontally between the bases of the pre- and postzygapophyses in some anterior caudal vertebrae. An expanded phylogenetic analysis places Gandititan as the sister taxon to Abdarainurus, within a clade of non-lithostrotian titanosaurs that also includes the Chinese titanosaurs Dongyangosaurus, Baotianmansaurus and Huabeisaurus, as well as the Argentine titanosaur Andesaurus. Such results imply the possible existence of a previously unrecognized group of titanosaurs in eastern Asia, and potential dispersal of titanosaurs between Asia and South America during the mid-Cretaceous. http://zoobank.org/urn:lsid:zoobank.org:pub:D0B258A9-2B3F-4159-8594-B19453B2F900

Bite and tooth marks on sauropod dinosaurs from the Morrison Formation.

Tooth-marked bones provide important evidence for feeding choices made by extinct carnivorous animals. In the case of the dinosaurs, most bite traces are attributed to the large and robust osteophagous tyrannosaurs, but those of other large carnivores remain underreported. Here we report on an extensive survey of the literature and some fossil collections cataloging a large number of sauropod bones (68) from the Upper Jurassic Morrison Formation of the USA that bear bite traces that can be attributed to theropods. We find that such bites on large sauropods, although less common than in tyrannosaur-dominated faunas, are known in large numbers from the Morrison Formation, and that none of the observed traces showed evidence of healing. The presence of tooth wear in non-tyrannosaur theropods further shows that they were biting into bone, but it remains difficult to assign individual bite traces to theropod taxa in the presence of multiple credible candidate biters. The widespread occurrence of bite traces without evidence of perimortem bites or healed bite traces, and of theropod tooth wear in Morrison Formation taxa suggests preferential feeding by theropods on juvenile sauropods, and likely scavenging of large-sized sauropod carcasses.

Exploring rebbachisaurid hind-limb anatomy on the basis of a new articulated specimen from the Huincul Formation (upper Cenomanian) of Neuquén Basin, Patagonia, Argentina

ABSTRACT Rebbachisauridae represents a group of diplodocoid sauropod dinosaurs known from the Early Cretaceous of Europe to the early Late Cretaceous of South America. Despite the rebbachisaurid fossil record being extended in recent years, most of the evidence is represented by incomplete and/or poorly preserved specimens; thus, the morphology of some body-sections, such as the cervical series, the pelvic girdle, and the limb elements, are poorly known or unknown. In this contribution we describe the complete and articulated hind-limbs of a new rebbachisaurid specimen MAU-Pv-EO-629 from the lower section of Huincul Formation (upper Cenomanian) of north-eastern Neuquén Basin (Neuquén Province, Patagonia, Argentina). The morphological features of the appendicular elements, especially of the femur and tibia, not only suggest rebbachisaurid affinities for MAU-Pv-EO-629, but also add new information on the hind-limb anatomy of Rebbachisauridae, which is poorly known to date. Indeed, this represents the first record of a reasonably complete pes in Rebbachisauridae, revealing a phalangeal reduction in rebbachisaurids with respect to other Diplodocoidea, and most sauropods. This new record from the upper Cenomanian of Neuquén Basin provides new information to reconstruct the last stages of the evolutionary history of Rebbachisauridae, before the post-Turonian faunal turnover.

New sauropod dinosaur from the Lower Cretaceous of Morella (Spain) provides new insights on the evolutionary history of Iberian somphospondylan titanosauriforms

Abstract A new somphospondylan titanosauriform from the Lower Cretaceous of Spain is described from the remains found at the Sant Antoni de la Vespa site (upper Barremian Arcillas de Morella Formation) located in Morella. Garumbatitan morellensis gen. et sp. nov. is diagnosed by 11 autapomorphies and eight local autapomorphies; and our phylogenetic analyses suggest that Garumbatitan morellensis might correspond to an early-branching somphospondylan. The presence of several somphospondylan traits in Garumbatitan morellensis supports the somphospondylan hypothesis. The phylogenetic distribution of some titanosauriform and somphospondylan novelties in the femur (markedly developed lateral bulge, high shaft eccentricity, linea intermuscularis cranialis, and trochanteric shelf) is discussed. The tarsus and pes of Garumbatitan morellensis are distinctive, being characterized by the loss of the calcaneum, relative slenderness of the metatarsals II, III, and IV when compared to the retracted metatarsals I and V, three pedal phalanges in digit IV, and reduced ungual III. The sauropod fauna of the Iberian Peninsula during the Hauterivian–Aptian shows a complex phylogenetic mosaic, including forms with Laurasian affinities, mainly titanosauriforms (Soriatitan, Garumbatitan, and possibly Tastavinsaurus and Europatitan), and Gondwanan affinities, the rebbachisaurid Demandasaurus. Faunal exchange during the Early Cretaceous between the Europe, North America, East Asia, and Africa is plausible.

A new record of saltasaurids in Africa; new evidence from the Middle Campanian, Western Desert, Egypt

ABSTRACT The Late Cretaceous deposits in the south of the Western Desert in the Dakhla Basin are well exposed, comprising variegated shales which contain a variety of vertebrates. In this contribution, we describe a new sauropod specimen from the Quseir Formation, represented by an almost complete humerus. The humerus shows a set of morphological features that allow us to refer it to the Saltasauridae, such as divided and well-developed distal condyles. Saltasaurids are ones of the smallest sauropod dinosaurs. The saltasaurids are newly recorded in Africa, although it was previously discovered on almost all the other continents in the Late Cretaceous. This study mentions the first record of saltasaurid humerus in Africa.

Evolution of the Earth Shakers: Sauropod dinosaurs are by far the biggest creatures ever to have walked on Earth. New research hints at how they got to be so gargantuan.

Evolution of the Earth Shakers: Sauropod dinosaurs are by far the biggest creatures ever to have walked on Earth. New research hints at how they got to be so gargantuan.

Rapid neck elongation in Sauropterygia (Reptilia: Diapsida) revealed by a new basal pachypleurosaur from the Lower Triassic of China

Neck elongation has appeared independently in several tetrapod groups, including giraffes and sauropod dinosaurs on land, birds and pterosaurs in the air, and sauropterygians (plesiosaurs and relatives) in the oceans. Long necks arose in Early Triassic sauropterygians, but the nature and rate of that elongation has not been documented. Here, we report a new species of pachypleurosaurid sauropterygian, Chusaurus xiangensis gen. et sp. nov., based on two new specimens from the Early Triassic Nanzhang-Yuan’an Fauna in the South China Block. The new species shows key features of its Middle Triassic relatives, but has a relatively short neck, measuring 0.48 of the trunk length, compared to > 0.8 from the Middle Triassic onwards. Comparative phylogenetic analysis shows that neck elongation occurred rapidly in all Triassic eosauropterygian lineages, probably driven by feeding pressure in a time of rapid re-establishment of new kinds of marine ecosystems.