Descendants of the Jurassic turiasaurs from Iberia found refuge in the Early Cretaceous of western USA

Sauropod dinosaur teeth from the lower Upper Cretaceous Winton Formation of Queensland, Australia and the global record of early titanosauriforms

The Upper Cretaceous Winton Formation of Queensland, Australia, has produced several partial sauropod skeletons, but cranial remains-including teeth-remain rare. Herein, we present the first description of sauropod teeth from this formation, based on specimens from three separate sites. An isolated tooth and a dentary fragment from the Diamantinasaurus matildae type locality are considered to be referable to that titanosaurian taxon. A single tooth from the D. matildae referred specimen site is similarly regarded as being part of that individual. Seventeen teeth from a new site that are morphologically uniform, and similar to the teeth from the two Diamantinasaurus sites, are assigned to Diamantinasauria. All sauropod teeth recovered from the Winton Formation to date are compressed-cone-chisel-shaped, have low slenderness index values (2.00-2.88), are lingually curved at their apices, mesiodistally convex on their lingual surfaces, and lack prominent carinae and denticles. They are markedly different from the chisel-like teeth of derived titanosaurs, more closely resembling the teeth of early branching members of the titanosauriform radiation. This provides further support for a 'basal' titanosaurian position for Diamantinasauria. Scanning electron microscope microwear analysis of the wear facets of several teeth reveals more scratches than pits, implying that diamantinasaurians were mid-height (1-10 m) feeders. With a view to assessing the spatio-temporal distribution of sauropod tooth morphotypes before and after deposition of the Winton Formation, we provide a comprehensive continent-by-continent review of the early titanosauriform global record (Early to early Late Cretaceous). This indicates that throughout the Early-early Late Cretaceous, sauropod faunas transitioned from being quite diverse at higher phylogenetic levels and encompassing a range of tooth morphologies at the start of the Berriasian, to faunas comprising solely titanosaurs with limited dental variability by the end-Turonian. Furthermore, this review highlights the different ways in which this transition unfolded on each continent, including the earliest records of titanosaurs with narrow-crowned teeth on each continent.

Enigmatic tracks of solitary sauropods roaming an extensive lacustrine megatracksite in Iberia

Sauropod remains are abundant on the Iberian Peninsula across the Jurassic-Cretaceous transition. Where the osteological record shows a high diversity of this kind of dinosaur, the ichnological findings are mainly limited to sauropod tracks characterized by kidney-shaped manus (with or without pollex impressions) and pes impressions with three claw imprints oriented laterally. Here, we present a new sauropod ichnotaxon, Iniestapodus burgensis, found at several exposures within the Las Sereas megatracksite (Burgos, Spain). These are preserved within lacustrine limestone strata of the Rupelo Formation (Tithonian-Berriasian). Iniestapodus burgensis is characterized by: semicircular manus tracks with small pollex impressions; unusual tetradactyl pes tracks with evidence of four claws oriented anteriorly (I-II) and laterally (III-IV), of variable sizes (short claw I and IV impressions, claw II and III being the largest). The combination of features and comparison with the osteological record allows us to propose a non-titanosaurian titanosauriform as a possible trackmaker. All the Iniestapodus tracks are represented by at least two different size classes of small and medium-sized individuals, and their trackways show different multidirectional orientations. The paleoenvironmental and paleoecological data suggest that Iniestapodus trackmakers were solitary individuals, likely representing different age classes, that crossed and used the Las Sereas shallow lacustrine-palustrine areas as their preferred habitat.

Origin and evolution of turiasaur dinosaurs set by means of a new ‘rosetta’ specimen from Spain

Turiasauria is a non-neosauropod eusauropod clade of dinosaurs known since 2006, when the description of Turiasaurus was published. This group, including Losillasaurus, was originally thought to have been restricted to the Late Jurassic of Spain. However, over the last decade, our knowledge of this group has improved with the discovery of new taxa such as Zby from the Portuguese Late Jurassic, Tendaguria from the Tanzanian Late Jurassic and Mierasaurus and Moabosaurus from the Early Cretaceous of the USA. Here, we describe a new specimen of Losillasaurus from Spain, which allows us to better understand the character variation in the cranial and postcranial skeleton. The review of some sauropod fauna of Madagascar, and inclusion of some specimens of Turiasauria, suggest that this clade might have arisen in the Middle Jurassic. According to our phylogenetic results, a specimen found in the early 19th century in Madagascar is shown to be the oldest and only member of Turiasauria represented in the Middle Jurassic thus far. This is named Narindasaurus thevenini gen. & sp. nov.. Turiasauria is thus known from the Middle Jurassic in Pangaea, diversified in the Late Jurassic in Gondwana and Laurasia, and dispersed during the Early Cretaceous to North America.

Redescription of Brachiosaurid Sauropod Dinosaur Material From the Upper Jurassic Morrison Formation, Colorado, USA

Like many long-standing dinosaur taxa, Brachiosaurus altithorax from the Upper Jurassic Morrison Formation of North America suffers from taxonomic issues stemming from a relatively incomplete holotype. Lack of anatomical overlap has precluded definitive referral of important specimens, including a mostly complete skull discovered in 1883. We redescribe this skull and some other significant brachiosaurid specimens based on new preparation and computed tomographic (CT) data. We argue that these elements are most parsimoniously referred to B. altithorax. Including these tentatively referred elements in a phylogenetic analysis does not alter the hypothesized relationships of B. altithorax, congruent with the presence of a single brachiosaurid taxon across western North America in the Late Jurassic. Based on CT data, we estimate that B. altithorax had a slower tooth replacement rate than Camarasaurus or the diplodocoids it shared Morrison Formation landscapes with, which suggests a difference in diet and/or feeding strategy. Anat Rec, 303:732-758, 2020. © 2019 Wiley Periodicals, Inc.

A turiasaurian sauropod dinosaur from the Early Cretaceous Wealden Supergroup of the United Kingdom

The Jurassic/Cretaceous (J/K) boundary, 145 million years ago, has long been recognised as an extinction event or faunal turnover for sauropod dinosaurs, with many ‘basal’ lineages disappearing. However, recently, a number of ‘extinct’ groups have been recognised in the Early Cretaceous, including diplodocids in Gondwana, and non-titanosauriform macronarians in Laurasia. Turiasauria, a clade of non-neosauropod eusauropods, was originally thought to have been restricted to the Late Jurassic of western Europe. However, its distribution has recently been extended to the Late Jurassic of Tanzania (Tendaguria tanzaniensis), as well as to the Early Cretaceous of the USA (Mierasaurus bobyoungi and Moabosaurus utahensis), demonstrating the survival of another ‘basal’ clade across the J/K boundary. Teeth from the Middle Jurassic–Early Cretaceous of western Europe and North Africa have also tentatively been attributed to turiasaurs, whilst recent phylogenetic analyses recovered Late Jurassic taxa from Argentina and China as further members of Turiasauria. Here, an anterior dorsal centrum and neural arch (both NHMUK 1871) from the Early Cretaceous Wealden Supergroup of the UK are described for the first time. NHMUK 1871 shares several synapomorphies with Turiasauria, especially the turiasaurs Moabosaurus and Tendaguria, including: (1) a strongly dorsoventrally compressed centrum; (2) the retention of prominent epipophyses; and (3) an extremely low, non-bifid neural spine. NHMUK 1871 therefore represents the first postcranial evidence for Turiasauria from European deposits of Early Cretaceous age. Although turiasaurs show clear heterodont dentition, only broad, characteristically ‘heart’-shaped teeth can currently be attributed to Turiasauria with confidence. As such, several putative turiasaur occurrences based on isolated teeth from Europe, as well as the Middle Jurassic and Early Cretaceous of Africa, cannot be confidently referred to Turiasauria. Unequivocal evidence for turiasaurs is therefore restricted to the late Middle Jurassic–Early Cretaceous of western Europe, the Late Jurassic of Tanzania, and the late Early Cretaceous of the USA, although remains from elsewhere might ultimately demonstrate that the group had a near-global distribution.

Cranial anatomy of Bellusaurus sui (Dinosauria: Eusauropoda) from the Middle-Late Jurassic Shishugou Formation of northwest China and a review of sauropod cranial ontogeny

Bellusaurus sui is an enigmatic sauropod dinosaur from the Middle-Late Jurassic Shishugou Formation of northwest China. Bellusaurus is known from a monospecific bonebed preserving elements from more than a dozen juvenile individuals, including numerous bones of the skull, providing rare insight into the cranial anatomy of juvenile sauropods. Here, we present a comprehensive description of the cranial anatomy of Bellusaurus, supplementing the holotypic cranial material with additional elements recovered from recent joint Sino-American field expeditions. Bellusaurus is diagnosed by several unique autapomorphies, including a neurovascular foramen piercing the ascending process of the maxilla at midheight, the frontal process of the nasal extending farther posteriorly onto the frontal than the prefrontal, and U-shaped medial and lateral notches in the posterior margin of the ventral process of the squamosal. Several features identified here, including a preantorbital opening in the maxilla, a stepped dorsal margin of the vomerine process of the pterygoid, and the partitioning of the dorsal midline endocranial fossae associated with the dural venous sinuses into anterior and posterior components by a transverse ridge of the parietal, are consistent with recent phylogenetic hypotheses that recover Bellusaurus as a basal macronarian or close relative of Neosauropoda. We review the current state of knowledge of sauropod cranial ontogeny, placing several aspects of the cranial anatomy of Bellusaurus in an ontogenetic context and providing explicit hypotheses of ontogenetic transformations that can be tested by future discoveries of ontogenetic variants of sauropod skulls. While scoring ontogenetically variable characters as unknown may help to alleviate the biasing effects of ontogeny on the phylogenetic position of juvenile specimens, we caution that this approach may remove phylogenetically informative character information, and argue that inference methods that are known to be less sensitive to homoplasy than equal weights parsimony (i.e., implied weights parsimony; Bayesian approaches) should also be employed.