Article

Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous sauropod diversity

September 2005
Journal of Systematic Palaeontology 3(03):283 - 318

DOI:10.1017/S1477201905001628

Authors:

The isolated skulls of Nemegtosaurus mongoliensis and Quaesitosaurus orientalis from the Nemegt Basin of Mongolia are among the most complete sauropod cranial remains known from the Late Cretaceous, yet their evolutionary relationships to other neosauropods have remained uncertain. Redescription of the skull of Nemegtosaurus identifies key features that link it and its closely related counterpart Quaesitosaurus to titanosaur sauropods. These include a posterolaterally orientated quadrate fossa, ‘rocker’-like palatobasal contact, pterygoid with reduced quadrate flange and a novel basisphenoid–quadrate contact. Other features are exclusive to Nemegtosaurus and Quaesitosaurus, such as the presence of a symphyseal eminence on the external aspect of the premaxillae, a highly vascularised tooth bearing portion of the maxilla, an enclosed ‘maxillary canal’, orbital ornamentation on the postorbital, prefrontal and frontal, exclusion of the squamosal from the supratemporal fenestra and dentary teeth smaller in diameter than premaxillary and maxillary teeth.

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

Article

Oct 2024

Sauropod 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.

Titanosaurian teeth from the South-central Pyrenees (Upper Cretaceous, Catalonia, Spain)

Article

Oct 2023
CRETACEOUS RES

A nearly complete skull of the sauropod dinosaur Diamantinasaurus matildae from the Upper Cretaceous Winton Formation of Australia and implications for the early evolution of titanosaurs

Article

Full-text available

Apr 2023

Titanosaurian sauropod dinosaurs were diverse and abundant throughout the Cretaceous, with a global distribution. However, few titanosaurian taxa are represented by multiple skeletons, let alone skulls. Diamantinasaurus matildae, from the lower Upper Cretaceous Winton Formation of Queensland, Australia, was heretofore represented by three specimens, including one that preserves a braincase and several other cranial elements. Herein, we describe a fourth specimen of Diamantinasaurus matildae that preserves a more complete skull—including numerous cranial elements not previously known for this taxon—as well as a partial postcranial skeleton. The skull of Diamantinasaurus matildae shows many similarities to that of the coeval Sarmientosaurus musacchioi from Argentina (e.g. quadratojugal with posterior tongue-like process; braincase with more than one ossified exit for cranial nerve V; compressed-cone–chisel-like teeth), providing further support for the inclusion of both taxa within the clade Diamantinasauria. The replacement teeth within the premaxilla of the new specimen are morphologically congruent with teeth previously attributed to Diamantinasaurus matildae, and Diamantinasauria more broadly, corroborating those referrals. Plesiomorphic characters of the new specimen include a sacrum comprising five vertebrae (also newly demonstrated in the holotype of Diamantinasaurus matildae), rather than the six or more that typify other titanosaurs. However, we demonstrate that there have been a number of independent acquisitions of a six-vertebrae sacrum among Somphospondyli and/or that there have been numerous reversals to a five-vertebrae sacrum, suggesting that sacral count is relatively plastic. Other newly identified plesiomorphic features include: the overall skull shape, which is more similar to brachiosaurids than ‘derived' titanosaurs; anterior caudal centra that are amphicoelous, rather than procoelous; and a pedal phalangeal formula estimated as 2-2-3-2-0. These features are consistent with either an early-branching position within Titanosauria, or a position just outside the titanosaurian radiation, for Diamantinasauria, as indicated by alternative character weighting approaches applied in our phylogenetic analyses, and help to shed light on the early assembly of titanosaurian anatomy that has until now been obscured by a poor fossil record.

Re-assessment of the Late Jurassic eusauropod Mamenchisaurus sinocanadorum Russell and Zheng, 1993, and the evolution of exceptionally long necks in mamenchisaurids

Article

Mar 2023

The sauropod genus Mamenchisaurus, from the Late Jurassic–Early Cretaceous of East Asia, has a convoluted taxonomic history. Although included in the first cladistic analysis of sauropods, only recently has the monophyly of Mamenchisaurus, and the anatomical diversity of the many penecontemporaneous East Asian eusauropods, been evaluated critically. Here, we re-describe the holotype and only specimen of M. sinocanadorum. Although the original diagnosis is no longer adequate, we identify several autapomorphies that support the validity of this species, including an elongate external mandibular fenestra and distinctive pneumatic structures on the cervical centra. We incorporate new data into a phylogenetic character matrix that also includes Bellusaurus and Daanosaurus, both of which are known only from juvenile material and are often hypothesized to be neosauropods (or close relatives thereof). We recover all species of Mamenchisaurus as part of a radiation of predominantly Middle–Late Jurassic East Asian eusauropods, but the genus is non-monophyletic, underscoring the need for further systematic revision of mamenchisaurid taxonomy. Analyses that score ontogenetically variable characters ambiguously recover Bellusaurus and Daanosaurus as juvenile mamenchisaurids, a hypothesis supported by several features that are unique to mamenchisaurids or exhibit little homoplasy, including anteriorly bifurcate cervical ribs. Finally, computed-tomography reveals extensive vertebral pneumaticity in M. sinocanadorum that is comparable to that of the largest sauropods, and updated scaling analyses imply a neck over 14 m long, rivalling estimates for other exceptionally long-necked sauropods. Previous work has suggested that the elongated cervical ribs of particularly long-necked sauropods such as M. sinocanadorum stabilized the neck by limiting its mobility. Given that extent of pneumaticity responds dynamically to a bone’s habitual loading, we propose that long cervical ribs – and other structural modifications that limited flexibility – promoted the evolution of increasingly long necks by producing a more predictable biomechanical milieu amenable to increased pneumatization.

A possible brachiosaurid (Dinosauria, Sauropoda) from the mid-Cretaceous of northeastern China

Article

Full-text available

Aug 2021

Brachiosauridae is a lineage of titanosauriform sauropods that includes some of the most iconic non-avian dinosaurs. Undisputed brachiosaurid fossils are known from the Late Jurassic through the Early Cretaceous of North America, Africa, and Europe, but proposed occurrences outside this range have proven controversial. Despite occasional suggestions that brachiosaurids dispersed into Asia, to date no fossils have provided convincing evidence for a pan-Laurasian distribution for the clade, and the failure to discover brachiosaurid fossils in the well-sampled sauropod-bearing horizons of the Early Cretaceous of Asia has been taken to evidence their genuine absence from the continent. Here we report on an isolated sauropod maxilla from the middle Cretaceous (Albian–Cenomanian) Longjing Formation of the Yanji basin of northeast China. Although the specimen preserves limited morphological information, it exhibits axially twisted dentition, a shared derived trait otherwise known only in brachiosaurids. Referral of the specimen to the Brachiosauridae receives support from phylogenetic analysis under both equal and implied weights parsimony, providing the most convincing evidence to date that brachiosaurids dispersed into Asia at some point in their evolutionary history. Inclusion in our phylogenetic analyses of an isolated sauropod dentary from the same site, for which an association with the maxilla is possible but uncertain, does not substantively alter these results. We consider several paleobiogeographic scenarios that could account for the occurrence of a middle Cretaceous Asian brachiosaurid, including dispersal from either North America or Europe during the Early Cretaceous. The identification of a brachiosaurid in the Longshan fauna, and the paleobiogeographic histories that could account for its presence there, are hypotheses that can be tested with continued study and excavation of fossils from the Longjing Formation.

Second specimen of the Late Cretaceous Australian sauropod dinosaur Diamantinasaurus matildae provides new anatomical information on the skull and neck of early titanosaurs

Article

Jan 2021
ZOOL J LINN SOC-LOND

The titanosaurian sauropod dinosaur Diamantinasaurus matildae is represented by two individuals from the Cenomanian-lower Turonian 'upper' Winton Formation of central Queensland, northeastern Australia. The type specimen has been described in detail, whereas the referred specimen, which includes several elements not present in the type series (partial skull, atlas, axis and postaxial cervical vertebrae), has only been described briefly. Herein, we provide a comprehensive description of this referred specimen, including a thorough assessment of the external and internal anatomy of the braincase, and identify several new autapomorphies of D. matildae. Via an expanded data matrix consisting of 125 taxa scored for 552 characters, we recover a close, well-supported relationship between Diamantinasaurus and its contemporary, Savannasaurus elliottorum. Unlike previous iterations of this data matrix, under a parsimony framework we consistently recover Diamantinasaurus and Savannasaurus as early-diverging members of Titanosauria using both equal weighting and extended implied weighting, with the overall topology largely consistent between analyses. We erect a new clade, named Diamantinasauria herein, that also includes the contemporaneous Sarmientosaurus musacchioi from southern Argentina, which shares several cranial features with the referred Diamantinasaurus specimen. Thus, Diamantinasauria is represented in the mid-Cretaceous of both South America and Australia, supporting the hypothesis that some titanosaurians, in addition to megaraptoran theropods and possibly some ornithopods, were able to disperse between these two continents via Antarctica. Conversely, there is no evidence for rebbachisaurids in Australia, which might indicate that they were unable to expand into high latitudes before their extinction in the Cenomanian-Turonian. Likewise, there is no evidence for titanosaurs with procoelous caudal vertebrae in the mid-Cretaceous Australian record, despite scarce but compelling evidence for their presence in both Antarctica and New Zealand during the Campanian-Maastrichtian. These later titanosaurs presumably dispersed into these landmasses from South America before the Campanian (~85 Mya), when seafloor spreading between Zealandia and Australia commenced. Although Australian mid-Cretaceous dinosaur faunas appear to be cosmopolitan at higher taxonomic levels, closer affinities with South America at finer scales are becoming better supported for sauropods, theropods and ornithopods.

Journal of Systematic Palaeontology Cranial anatomy of the Late Jurassic dwarf sauropod Europasaurus holgeri (Dinosauria, Camarasauromorpha): ontogenetic changes and size dimorphism Cranial anatomy of the Late Jurassic dwarf sauropod Europasaurus holgeri (Dinosauria, Camarasauromorpha): ontogenetic changes and size dimorphism

Article

Full-text available

Mar 2014

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

Article

Full-text available

Jun 2019
ANAT REC

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.

Complex overlapping joints between facial bones allowing limited anterior sliding movements of the snout in diplodocid sauropods

Book

Full-text available

Jan 2018

Digital reconstruction of the skull of Sarmientosaurus musacchioi, a titanosaur (Sauropoda, Dinosauria) from the Upper Cretaceous of Argentina

Article

Full-text available

Dec 2024

The study of titanosaur paleobiology has been severely hampered by the incomplete nature of their fossil record, particularly the scarcity of well-preserved and relatively complete cranial remains. Even the most complete titanosaur skulls are often fractured, incomplete, or deformed, which has resulted in a limited knowledge of the paleobiology related to cranial anatomy, especially functional morphology. In this context, we present the digital restoration of the skull of the Argentinean titanosaur Sarmientosaurus musacchioi, created using the open-source 3D modeling software Blender. The digitally restored model is freely accessible to other researchers, facilitating broader research and comparative studies.

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

Article

Jan 2024

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 nonlithostrotian 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.

The largest known titanosaur (Dinosauria, Sauropoda) tooth and other isolated dental elements from the Serra da Galga Formation (Cretaceous of Southeast Brazil)

Article

Jul 2023
CRETACEOUS RES

Titanosaur sauropods are a common component of the Upper Cretaceous fauna of the Serra da Galga Formation, Triângulo Mineiro region, Minas Gerais, Brazil. Among these, three distinct tooth morphotypes are recognized and described here. One of the teeth represents the largest titanosaur tooth ever found, whereas others correspond to possible juveniles. This diversity of morphologies, sizes, and ontogenetic stages shows that the Serra da Galga environment supported a diverse titanosaur fauna.

Dinosaur teeth from the mid-Cretaceous Sunjiawan Formation of western Liaoning Province, China

Article

Feb 2023

The mid-Cretaceous Sunjiawan Formation of western Liaoning Province, China has yielded a diverse of dinosaurs, yet without records of theropods. Recently, four isolated dinosaur teeth were discovered from the Sunjiawan Formation in Shuangmiao, Liangshuihe, Beipiao, Liaoning, China. They can be assigned to Tyrannosauroidea, Titanosauriformes and Hadrosauroidea based on morphological features. The tyrannosauroid tooth represents the first fossil record of Theropoda in the Sunjiawan Formation. The titanosauriform tooth is provisionally attributed to Borealosaurus considering that they are from the same horizon and locality. The hadrosauroid teeth represent a distinct taxon from Shuangmiaosaurus, the only known hadrosauroid from this formation. These findings increased the diversity of dinosaurs of the Sunjiawan Formation from three taxa to five.

Time for Giants: Titanosaurs from the Berriasian–Santonian Age

Chapter

Apr 2022

Titanosaurian sauropods were the most diverse and successful group of large-bodied terrestrial herbivores. Two aspects regarding their evolutionary history stand out, namely their great morphological diversity and their extensive record from various continental masses. In South America, and particularly in Argentina, the group has the richest record worldwide. This is mainly due to the conjunction of two factors: the extensive paleontological investigation carried out by South American researchers since the beginning of the twentieth century and the well-exposed outcrops of Cretaceous continental strata. With the exception of Tapuiasaurus from Brazil, the entire record of South American named titanosaurs discovered in the Berriasian–Santonian interval comes from Argentina, specifically from Patagonia, including the south of Mendoza, Neuquén, Río Negro, and Chubut Provinces. With a number of 22 valid taxa, the Early and ‘Mid’-Cretaceous titanosaur record of South America includes basally branching (‘basal’) forms (e.g., Andesaurus, Ninjatitan), basal and derived lithostrotians (e.g., Sarmientosaurus, Tapuiasaurus, and Epachthosaurus), and most of the colossosaurs (mainly the giant lognkosaurs Mendozasaurus, Futalognkosaurus, Patagotitan, and Notocolossus). After their origin in the Early Cretaceous, titanosaurians experienced a rapid increase in taxonomic diversity, which is maintained toward the Late Cretaceous. However, during the Berriasian–Santonian interval, the size of titanosaurs reached its climax, representing the largest vertebrate animals ever to inhabit the earth. Some South American titanosaurs from this time have been widely used to define new clades (e.g., Colossosauria, Lognkosauria, Rinconsauria) that clarified the main phylogenetic relationships at lower level. Moreover, studies in some key paleobiological aspects related with the estimation of size contributed to better understanding the biology of some species in the context of the process of gigantism.

Taphonomy: Overview and New Perspectives Related to the Paleobiology of Giants

Chapter

Apr 2022

Most taphonomy studies of South American sauropodomorphs have addressed extrinsic factors such as sedimentary environments, bone dispersal, and mineralogical processes that occurred during fossil diagenesis. These studies provide important data on the taphonomic modes which are associated with bone accumulations in different paleoenvironmental contexts. However, these analyses have generally not considered intrinsic factors like the shape, size, and structural integrity of the skeletal elements, variables that can produce some taphonomic bias. Sauropodomorphs include dinosaurs of highly varied sizes, ranging from small (less than 8 m long) to remarkably giant forms (around 30 m long). In the largest sauropods, such as the huge titanosaurs, very incomplete skeletons are commonly found and most notably skull and articulated pedes rarely are preserved. We focus here on some intrinsic anatomical factors as they relate to articulation in some key parts of the skeletons. Further, this study suggests that the preservation of fragile portions of sauropodomorph skeletons was possible only under specific combinations of sedimentological and biological processes.

New Data on Late Cretaceous Sauropods from the Bostobe Formation of the Northeastern Aral Sea Region (Kazakhstan)

Article

Full-text available

Apr 2022
DOKL EARTH SCI

The curved pencil-like sauropod teeth from the Bostobe Formation (Upper Cretaceous, Santonian-Campanian) of the Shakh-Shakh locality in Kazakhstan are referred to a representative of the Laurasian clade Opisthocoelicaudiidae known from the Upper Cretaceous (Campanian-Maastrichtian) of Mongolia. The teeth are slightly expanded near the apex and have in this part D-shaped cross-section. The enamel sculpturing consists of short longitudinal ridges or enamel is smooth in some parts of the crown. A similar dental morphotype is found in a titanosaur from the Bissekty Formation (Turonian) of Uzbekistan, which also may belong to the Opisthocoelicaudiidae.

5. Structure and Evolution of a Sauropod Tooth Battery

Chapter

Dec 2019

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

Article

Full-text available

Sep 2020
ZOOL J LINN SOC-LOND

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.

Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies

Article

Full-text available

Oct 2019
ANAT REC

Body size has thermal repercussions that impact physiology. Large‐bodied dinosaurs potentially retained heat to the point of reaching dangerous levels, whereas small dinosaurs shed heat relatively easily. Elevated body temperatures are known to have an adverse influence on neurosensory tissues and require physiological mechanisms for selective brain and eye temperature regulation. Vascular osteological correlates in fossil dinosaur skulls from multiple clades representing different body‐size classes were identified and compared. Neurovascular canals were identified that differentiate thermoregulatory strategies involving three sites of evaporative cooling that are known in extant diapsids to function in selective brain temperature regulation. Small dinosaurs showed similarly sized canals, reflecting a plesiomorphic balanced pattern of blood supply and a distributed thermoregulatory strategy with little evidence of enhancement of any sites of thermal exchange. Large dinosaurs, however, showed a more unbalanced vascular pattern whereby certain sites of thermal exchange were emphasized for enhanced blood flow, reflecting a more focused thermal strategy. A quantitative, statistical analysis of canal cross‐sectional area was conducted to test these anatomical results, confirming that large‐bodied, and often large‐headed, species showed focused thermal strategies with enhanced collateral blood flow to certain sites of heat exchange. Large theropods showed evidence for a plesiomorphic balanced blood flow pattern, yet evidence for vascularization of the large antorbital paranasal air sinus indicates theropods may have had a fourth site of heat exchange as part of a novel focused thermoregulatory strategy. Evidence presented here for differing thermoregulatory strategies based on size and phylogeny helps refine our knowledge of dinosaur physiology. Anat Rec, 303:1075–1103, 2020. © 2019 American Association for Anatomy

Rediscovery of the type localities of the Late Cretaceous Mongolian sauropods Nemegtosaurus mongoliensis and Opisthocoelicaudia skarzynskii: Stratigraphic and taxonomic implications

Article

Full-text available

Feb 2019

A new sauropod species from north-western Brazil: biomechanics and the radiation of Titanosauria (Sauropoda: Somphospondyli)

Article

May 2024
ZOOL J LINN SOC-LOND

Titanosaurs were the most diverse sauropod group during the Cretaceous period, with most of its diversity being found during the Late Cretaceous. In this work, Tiamat valdecii, gen. et sp. nov. is described, a new species of basal titanosaur prospected from the Açu Formation (Albian–Cenomanian), Potiguar Basin, Ceará state, north-east Brazil. Te new taxon is composed by an associated sequence of anterior to middle caudal vertebrae, being diagnosed by four diagnostic features: a marked accessory tuberosity dorsoventrally developed, located on the prezygapophyses; deeply medioventral excavated articulation facets of prezygapophysis and post-zygapophyses articular facets; presence of developed hypantrum–hyposphene articulations; and short middle centra with a well-marked articular facet for the haemal arch. Te phylogenetic analysis reveals that Tiamat valdecii was a basal member of Titanosauria. Tiamat is the first species of Early Cretaceous titanosaur known for the Açu Formation. Biomechanical analysis shows that the tuberosity and excavation of the zygapophyses of the middle caudal vertebrae of Tiamat provide greater stability against shear loads in the amphicoelous vertebrae presented; in addition, they allow greater range of lateral movements without afecting the integrity of the joints. These features may have been an evolutionary alternative for the stability of the middle of the caudal vertebral column. The discovery of T. valdecii in the Açu Formation not only increases the known dinosaur diversity for this unit, but also helps us elucidate part of the first titanosaur radiation.

Early-diverging Titanosauriform (Dinosauria, Sauropoda) Teeth from the Lower Cretaceous Yixian Formation of Southeastern Inner Mongolia, Northeast China

Article

Apr 2024

Three eusauropod teeth (SDUST‐V1064, PMOL‐AD00176, PMOL‐ADt0005) are reported from the Lower Cretaceous Yixian Formation of Ningcheng, southeastern Inner Mongolia, China. Two of them (SDUST‐V1064, PMOL‐AD00176) are assigned to early‐diverging titanosauriforms in having slightly mesiodistal expansion at the base of the tooth crown, a slenderness index value >2.0 and <4.0, and D‐shaped cross section. Furthermore, SDUST‐V1064 and PMOL‐AD00176 are referred as an Euhelopus ‐like titanosauriform on the basis of having a sub‐circular boss on the lingual surface and an asymmetrical crown‐root margin which slants apically, respectively. CT scan data of SDUST‐V1064 reveals new dental information of early‐diverging titanosauriforms, for example, the enamel on the labial side thicker than that on the lingual side, an enamel/dentine ratio of 0.26 and a boss present on the lingual side of the dentine of the crown.

A rebbachisaurid-mimicking titanosaur and evidence of a Late Cretaceous faunal disturbance event in South-West Gondwana

Article

Oct 2023
CRETACEOUS RES

A new titanosaur sauropod genus including an almost complete skull and axial elements to the hips, reflecting a convergent bauplan with the older rebbachisaurids sauropods.

New teeth of a basal Macronarian (Sauropoda) from the Jurassic–Cretaceous transition of SpainNuevos dientes de un macronario basal (Sauropoda) del Tránsito Jurásico-Cretácico de España

Article

Full-text available

Sep 2023

In this work, a dentary, and several teeth from the Valdepalazuelos-Tenadas del Carrascal site (Burgos, Spain) are studied. Geologically,this site is situatedat the base of the Rupelo Formation (Cuenca de Cameros), of Tithonian–Berriasian age. This formation has been interpreted as lacustrine-palustrine deposits with low gradient margins and with periodic changes in the water level. MDS-VPCR,851 is a fragment of the rostral symphyseal zone of a right dentary, a robust bone with a rostral ridge on its lingual surface, large diameter foramina on the lingual surface, a wide Meckelian canal extending from the rostroventral margin, semicircular symphysis arranged rostrolingually, and with two alveoli preserving two erupting teetheach. Although the functional teeth have not been preserved, each alveolus could contain one active tooth and at least two replacement teeth. Eight maxillary and mandibular teeth are described, with a spatulate crown, a rough enamel surface, a D-shaped croos-section, and a very marked cingulum. The dentary and teeth from this site have evident differences with those of other taxa and specimens described in the Kimmeridgian-Berriasian of the Iberian Peninsula. Its greatest similarities are with Camarasaurus , but in the specimens from Valdepalazuelos there are characters that seem to be unique and differ from that taxon. Consequently. the specimens described here are identified as belonging to a basal macronarian, close to Camarasaurus . This work points to the existence of two macronarian sauropods in the Tithonian–Berriasian transit of the Cameros Basin, and increases the diversity of the Iberian record of that time period.

Cranial osteology of Bajadasaurus pronuspinax (Sauropoda, Dicraeosauridae)

Article

May 2023

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

Article

Full-text available

Jul 2022

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.

The first turiasaurian sauropod of India reported from the Middle Jurassic (Bathonian) sediments of Jaisalmer Basin, Rajasthan, India

Article

May 2022
Neues Jahrbuch Geol Palaontol Abhand

This study presents the dental record of a non-neosauropod eusauropod from the Middle Jurassic rocks of the Jaisalmer Basin, India. An isolated, fragmentary heart-shaped crown of a turiasaur has been recovered from the intraformational conglomerate of the Badabag Member (Bathonian) of the Jaisalmer Formation. The heart-shaped, asymmetrical crowns with a labio-lingually compressed apex and apicobasal shallow grooves in the root are exclusive to the Turiasauria clade. This is the first record of a turiasaur from India as well as from Asia. This study extends the geographic distribution of the Turiasauria clade and provides new data about the diversity in the Jurassic sauropod fauna of India. The presence of heart-shaped teeth, from both Laurasia and Gondwanaland, shows a much wider geographic and stratigraphic distribution of the Turiasauria clade. There was a possibility of faunal exchange between the two big landmasses at least during the Jurassic. This study is one more step in bringing out the diversity in the vertebrate assemblage of the Jaisalmer Basin during the Middle Jurassic.

Fossil assemblage from the Khok Pha Suam locality of northeastern, Thailand: an overview of vertebrate diversity from the Early Cretaceous Khok Kruat Formation (Aptian-Albian)

Article

Full-text available

Mar 2022

The Khok Pha Suam locality in the province of Ubon Ratchathani, northeastern, Thailand, is known as “the last home of Thai dinosaurs”, because it belongs to the Lower Cretaceous Khok Kruat Formation (Aptian-Albian) which is currently the youngest Mesozoic vertebrate fossil producing formation in the Khorat Group. Here, we describe a diverse vertebrate assemblage, including hybodonts, ray-finned fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs from the Khok Pha Suam locality. The updated data on the Khok Kruat fauna provides a better understanding of the variety and distribution of Early Cretaceous continental ecosystems, which are useful for palaeoenvironmental reconstruction. In addition to consolidating unincorporated data on fauna, this study also provides the palaeontological data necessary to illustrate the palaeoecosystem to the general public, as well as improving the academic value of the Pha Chan-Sam Phan Bok Geopark.

The oldest centrosaurine: a new ceratopsid dinosaur (Dinosauria: Ceratopsidae) from the Allison Member of the Menefee Formation (Upper Cretaceous, early Campanian), northwestern New Mexico, USA

Article

Full-text available

May 2021

An associated incomplete skeleton of a ceratopsid dinosaur from the Campanian deposits of the Allison Member of the Menefee Formation in New Mexico, USA is described. Although it was originally described over two decades ago, newly prepared portions of the Menefee Formation skeleton and reinterpretations of previously known morphology, in addition to newly described specimens have provided new information on ceratopsids, and centrosaurines in particular. These new data allow for a thorough reassessment of the specimen and the erection of a new taxon: Menefeeceratops sealeyi gen. et sp. nov., potentially the oldest recognized member of Centrosaurinae. Menefeeceratops sealeyi is represented by diagnostic cranial and postcranial skeletal elements. The cranial elements include a portion of the left premaxilla, a nearly complete left postorbital horncore, a parietal fragment, the right and left squamosals, the left jugal, the predentary, and the left dentary. Postcranial material consists of two cervical vertebrae, eight dorsal vertebrae, a partial sacrum with six sacral vertebrae, 11 dorsal ribs, the distal left radius, proximal and distal portions of the left ulna, the left femur, and a left metatarsal II. The taxonomic validity of Menefeeceratops sealeyi is supported by a combination of several morphological characters. These include a lack of epiossifications on the lateroposterior edge of the parietal (shared with Machairoceratops), three epiossifications on the squamosal, and three smaller, secondary undulations as part of episquamosal locus S1. There are also two subequal embayments on the posterior free margin of the squamosal with the more dorsal embayment (between episquamosal loci 1 and 2) distinctly larger than the ventral (= lateroventral) one (between episquamosal loci 2 and 3), three ridges on the lateral (dorsolateral) surface of the squamosal, an elongate posterior portion of the squamosal, the presence of a shallow but distinct groove on the medial surface of the squamosal nearly paralleling the ventrolateral and ventroposterior edges, elongate postorbital (= supraorbital) horns that are anteriorly curved distally, and two elongate ridges on the lateral surface of the dentary that diverge anteriorly, creating a distinct anterior triangular fossa. Phylogenetic analysis of Menefeeceratops sealeyi places this new species as a basal centrosaurine, most closely related to Crittendenceratops krzyzanowskii, thus adding to the growing record of centrosaurines discovered in western North America. It thus provides new information about the diversity of morphologies throughout different species and the temporal and paleobiogeographic distribution of these animals throughout Laramidia during the Late Cretaceous. Its presence as one of the, if not the, oldest members of the Centrosaurinae also suggests centrosaurines originated in the southern portions of western North America and the southern Rocky Mountain region, and subsequently radiated north during the upper middle to late Campanian.

The prefrontal of Rinconsaurus caudamirus (Sauropoda, Titanosauria) as a crocodyliform ilium

Article

Apr 2021
CRETACEOUS RES

The holotype of the titanosaur sauropod Rinconsaurus caudamirus, from the Bajo de la Carpa Formation (Santonian, Upper Cretaceous, Neuquén Group), is based on an articulated series of 13 anterior-middle to middle posterior caudal vertebrae and two illia, in addition to cranial, axial and appendicular elements corresponding to several individuals. One of the skull elements originally identified as a prefrontal (MAU-Pv-CRS-102), is reinterpreted here as a mesoeucrocodylian right ilium, likely belonging to Pehuenchesuchus enderi, a crocodyliform found in the same quarry. Therefore, this element is excluded from the Rinconsaurus type materials, adding a new element to Pehuenchesuchus and increasing the knowledge of its anatomy.

Diversity and palaeoecology of Australia's southern‐most sauropods, Griman Creek Formation (Cenomanian), New South Wales, Australia

Article

Oct 2020

Predominately, occurances of Australian sauropods from the Early to mid‐Cretaceous of Queensland and Western Australia, lie between ~45° and 55°S palaeolatitude. The Cenomanian Griman Creek Formation, which straddles the New South Wales–Queensland border, preserves arguably one of the richest Cretaceous terrestrial faunas in Australia. Although sauropod postcranial elements are notably absent or as yet unidentified, isolated sauropod teeth are relatively well represented from exposures near Lightning Ridge (New South Wales), offering insights into the diversity and palaeoecology of these animals at ~60°S palaeolatitude. From a sample of 25 teeth, we identify five dental morphotypes from the Griman Creek Formation. Some of this variation is attributed to heterodonty; however, other distinctive morphologies partly agree with previous indications of at least two taxa of non‐titanosaur titanosauriforms together with a third, possible titanosaur in the Griman Creek Formation. An investigation of dental microwear found two teeth with identifiable wear features, but differences in these features suggest separate feeding strategies consistent with the hypothesis of ecological tiering between sympatric species. The presence of at least two non‐titanosaur titanosauriforms and a third species of titanosaur in the Griman Creek Formation is reminiscent of the roughly coeval Winton Formation in central Queensland, which preserves three titanosauriform species, and implies that diverse sauropod communities persisted during this interval into their most southern recorded range in Australia.

An unusual new sauropod dinosaur from the Late Cretaceous of Mongolia

Article

Full-text available

Feb 2020
J SYST PALAEONTOL

A new sauropod, Abdarainurus barsboldi gen. et sp. nov., is described based on several anterior and one middle caudal vertebrae and chevrons from the Late Cretaceous Alagteeg Formation at Abdrant Nuru, northern Gobi Desert, Mongolia. The new taxon is characterized by 16 unique or rare characters of the caudal skeleton, including opisthocoelous centra, longitudinal ridges on the neural canal walls, postprezygapophyseal processes, a hypertrophied postspinal fossa, mediolaterally constricted neural spines, and a deep pocket-like spinodiapophyseal fossa covered laterally by high postzygodiapophyseal lamina. Our preferred phylogenetic analysis places Abdarainurus as a basal titanosaurian sauropod, but this result could be affected by inadequate knowledge of basal titanosaurs. The new taxon likely represents a highly specialized lineage of Asian macronarian sauropods that was unknown previously. http://zoobank.org/urn:lsid:zoobank.org:pub::87174FD4-0616-4BD6-9209-C40C0455D2DA

First palaeoneurological study of a sauropod dinosaur from France and its phylogenetic significance Distributed under Creative Commons CC-BY 4.0

Article

Full-text available

Nov 2019

Despite continuous improvements, our knowledge of the palaeoneurology of sauropod dinosaurs is still deficient. This holds true even for Titanosauria, which is a particularly speciose clade of sauropods with representatives known from numerous Cretaceous sites in many countries on all continents. The data currently available regarding the palaeoneurology of titanosaurs is strongly biased towards Gondwanan forms (Argentina above all, but also India, Malawi and Australia). In contrast, the palaeoneurology of Laurasian titanosaurs is known only from a few taxa from Spain and Uzbekistan, despite the discovery in other countries of Laurasia of a number of neurocranial remains that would lend themselves well to investigations of this kind. To fill in this gap in our knowledge, we subjected a titanosaurian braincase from the uppermost Upper Cretaceous of southern France to X-ray computed tomographic scanning, allowing the generation of 3D renderings of the endocranial cavity enclosing the brain, cranial nerves and blood vessels, as well as the labyrinth of the inner ear. These reconstructions are used to clarify the phylogenetic position of the specimen from the Fox-Amphoux-Métisson site. A combination of characters, including the presence of two hypoglossal rami on the endocast, the average degree of development of the dorsal-head/ caudal-middle-cerebral vein system and the relatively short and subequal lengths of the ipsilateral semicircular canals of the labyrinth, are particularly revealing in this respect. They suggest that, compared with the few other Laurasian titanosaurs for which in-depth palaeoneurological data are available, the French taxon is more derived than the distinctly more ancient, possibly non-lithostrotian titanosaur from the Uzbek site of Dzharakuduk but more basal than derived saltasaurids, such as the coeval or slightly more recent forms from the Spanish locality of Lo Hueco.

New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography

Article

Full-text available

Aug 2019

Titanosaurs were a globally distributed clade of Cretaceous sauropods. Historically regarded as a primarily Gondwanan radiation, there is a growing number of Eurasian taxa, with several putative titanosaurs contemporaneous with, or even pre-dating, the oldest known Southern Hemisphere remains. The early Late Cretaceous Jinhua Formation, in Zhejiang Province, China, has yielded two putative titanosaurs, Jiangshanosaurus lixianensis and Dongyangosaurus sinensis. Here, we provide a detailed re-description and diagnosis of Jiangshanosaurus, as well as new anatomical information on Dongyangosaurus. Previously, a 'derived' titanosaurian placement for Jiangshanosaurus was primarily based on the presence of procoelous anterior caudal centra. We show that this taxon had amphicoelous anterior-middle caudal centra. Its only titanosaurian synapomorphy is that the dorsal margins of the scapula and coracoid are approximately level with one another. Dongyangosaurus can clearly be differentiated from Jiangshanosaurus, and displays features that indicate a closer relationship to the titanosaur radiation. Revised scores for both taxa are incorporated into an expanded phylogenetic data matrix, comprising 124 taxa scored for 548 characters. Under equal weights parsimony, Jiangshanosaurus is recovered as a member of the non-titanosaurian East Asian somphospondylan clade Euhelopodidae, and Dongyangosaurus lies just outside of Titanosauria. However, when extended implied weighting is applied, both taxa are placed within Titanosauria. Most other 'middle' Cretaceous East Asian sauropods are probably non-titanosaurian somphospondylans, but at least Xianshanosaurus appears to belong to the titanosaur radiation. Our analyses also recover the Early Cretaceous European sauropod Normanniasaurus genceyi as a 'derived' titanosaur, clustering with Gondwanan taxa. These results provide further support for a widespread diversification of titanosaurs by at least the Early Cretaceous.

Sauropod diversity in the Upper Cretaceous Nemegt Formation of Mongolia – a possible new specimen of Nemegtosaurus

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Full-text available

Apr 2019

Currently, there are two sauropod taxa known from the Upper Cretaceous (Maastrichtian) Nemegt Formation of Gobi Desert, Mongolia: Nemegtosaurus from the Nemegt locality and Opisthocoelicaudia from the Altan Uul IV locality. Both taxa are represented by not overlapping elements (skull and partial postcranial skeleton respectively), which arises question on their possible synonymy. Five articulated sauropod dorsal vertebrae (PIN 3837/P821, dorsals 6–10) were found in 1949 by the Mongolian Expedition of the Academy of Sciences of the USSR at the Nemegt locality. This specimen is similar to Opisthocoelicaudia in having a strong ventral ridge on dorsal centra, a low neural arch which is anteroposteriorly narrowest at the junction with the centrum and widens dorsally, and lack of hyposphene–hypantrum articulations. PIN 3837/P821 differs from Opisthocoelicaudia by having the less dorsoventrally flattened dorsal centra, a shallow ventral concavity of dorsal centra in lateral view, a vertical posterior centrodiapophyseal lamina (pcdl) in dorsals 8 and 9, a postzygodiapophyseal lamina (podl) that roofs the centrodiapophyseal fossa (pocdf), and strongly developed accessory laminae within the parapophyseal centrodiapophyseal fossa (pacdf). The sauropod femora from Nemegt Formation differ from the femur of Opisthocoelicaudia by the medial condyle extending more distally compared with the lateral condyle. Most likely these femora and PIN 3837/P821 belong to Nemegtosaurus, which would make this taxon distinct from Opisthocoelicaudia by discussed characters of dorsal vertebrae and femur.

Sauropod diversity in the Upper Cretaceous Nemegt Formation of Mongolia – a possible new specimen of Nemegtosaurus

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Full-text available

Jun 2019

A new giant basal titanosaur sauropod in the Upper Cretaceous (Coniacian) of the Neuquén Basin, Argentina

Article

Mar 2019

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

Article

Full-text available

Feb 2019
PLOS ONE

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.

A new basal iguanodont (Dinosauria: Ornithischia) from the Wealden (Lower Cretaceous) of England

Article

Aug 2010

A nearly complete right dentary originally noted by Mantell in 1848 is redescribed. The specimen, NHMUK 28660, was discovered in a quarry near Cuckfield, West Sussex, from the same formation as the original teeth of Iguanodon anglicus. Fresh examination reveals that NHMUK 28660 exhibits a single autapomorphy (a row of foramina extending from the ventral surface of the symphysis onto the lateral surface of the dentary) and a unique combination of characters that distinguish it from all other iguanodontian dentaries. In light of this and because I. anglicus is regarded as a nomen dubium to which additional material cannot be unambiguously referred, NHMUK 28660 is made the holotype of the new genus and species Kukufeldia tilgatensis.

Baalsaurus mansillai gen. et sp. nov. a new titanosaurian sauropod (Late Cretaceous) from Neuquén, Patagonia, Argentina

Article

Full-text available

Dec 2018
AN ACAD BRAS CIENC

We describe a dentary of a new titanosaur sauropod, Baalsaurus mansillai, gen. et sp. nov. from the Late Cretaceous of Patagonia, Argentina. The material comes from the Portezuelo Formation, Neuquén Group. Titanosaur sauropods lower jaws are scarce and only nine taxa with dentaries have been described. There are two types of morphology in titanosaur dentaries; “L” shaped or “U” shaped based on the shape, without a phylogenetic issue. In this paper; we recognize a new taxa, Baalsaurus mansillai, represented by an “L” shaped dentary with three apomorphic characters that are not present in other taxa: dentary alveoli with 10 teeth in the anterior ramus, a ventrally and anteriorly inclined symphysis and a wide ventral Meckelian groove surrounded by a thin lamina that forms a keel on the ventral border of the dentary.

A small sauropod trackway from the Upper Cretaceous Jindong Formation (Cenomanian), Goseong County, South Korea

Article

Oct 2024
CRETACEOUS RES

Cranial anatomy of Bagualia alba (Dinosauria, Eusauropoda) from the Early Jurassic of Patagonia and the implications for sauropod cranial evolution

Article

Oct 2024

Evolutionary trends in the skull morphology of sauropodomorph dinosaurs: a two-dimensional geometrical approach

Article

Full-text available

Sep 2024

Changyu Yun

The skull morphology of sauropodomorph dinosaurs has been used to examine the biomechanics, ecology, growth and phylogeny of this lineage. Previous works have suggested that roughly three cranial morphotypes occurred throughout sauropodomorph evolution: 1) a morphotype with a shallow skull, anteriorly positioned external naris and extended tooth row, seen in non-sauropod sauropodomorphs; 2) a morphotype that is characterized by a high, domed and robust (or boot-shaped) skull seen in early-diverging sauropods and basal macronarians; and 3) a morphotype with a low skull, downturned snout, retracted external naris and anteriorly restricted dental row, seen in diplodocoids and some titanosaurs. This geometric morphometric study reaffirms and supplements such previous conclusions with a more expanded dataset and detailed landmark analysis. Furthermore, this work demonstrates, or confirms that there was a great variation in skull depth among early sauropodomorphs, basal titanosaurs retained at least some cranial characters seen in early macronarians, and derived titanosaurs converged with diplodocoids in their skull shape to the extreme. Such variations were likely correlated with their diet or feeding ecology.

Fossils Explained 83: Diversity of skull morphology in the Titanosauria

Article

Jan 2023

Saurabh Pal

Titanosaurs were a globally distributed group of sauropod dinosaurs. They had diverse forms and a wide‐gauge stance, with a few of their species reaching immense sizes, such as Argentinosaurus huinculensis and Patagotitan mayorum (reaching >35 m in length). There are about 100 valid titanosaur species known so far, but most of the originally described species are no longer valid, due to the incomplete nature of fossil materials. Our understanding of titanosaur skull morphology is based on very few incomplete fragmented cranial materials and findings of the complete skull are even rarer. Understanding the skull morphology of extinct animals helps palaeontologists make deductions of feeding mechanisms and also provide an idea about their appearance when they were alive. Diversity in titanosaur skull morphology is greater than that of any other sauropod clade, indicating diversity in feeding mechanism among these dinosaurs. Titanosaurs were the last surviving clade of sauropod dinosaurs, occupying nearly every ecological niche around the world during the Late Cretaceous, and resulting in a rich diversity in this group. This article highlights diversity in the basic structure of sauropods with special emphasis on titanosaur skull morphology.

Titanosauria: A Critical Reappraisal of Its Systematics and the Relevance of the South American Record

Chapter

Full-text available

Apr 2022

Our understanding of sauropodomorph evolution is continually improved with the recognition of new species and their inclusion in phylogenetic data sets, along with the incorporation of novel characters. Whereas some subclades remain stable in terms of their original taxonomic content, the definitions of others have proven to be less easily applicable as increased taxon and character sampling has changed sauropodomorph interrelationships. Relatively minor differences in the position of clade specifiers between alternative phylogenies result in substantial differences in clade composition in several instances. Titanosauria is the most successful and diverse clade of sauropodomorph dinosaurs, but its interrelationships are poorly understood. With an ever-growing number of recognized species and increased taxon sampling in phylogenies, resulting in the recovery of newly identified, diverse subclades, the need to re-evaluate titanosaurian supra-specific taxonomy becomes increasingly important. Using fifteen phylogenetic data sets, we conducted a series of analyses to detect the most stable clades and taxa amongst Titanosauria. Based on this, we propose several changes to titanosaur systematics, including a newly defined node-stem triplet composed of Eutitanosauria and its constituent lineages, Colossosauria and Saltasauroidea, developing a new framework to improve stability and facilitate communication of phylogenetic results.

Last Titans: Titanosaurs From the Campanian–Maastrichtian Age

Chapter

Apr 2022

After the extinction of rebbachisaurids during the Cenomanian–Turonian interval, titanosaurs were the only group of sauropods to face the K–Pg event. This same global pattern also holds for the end-Cretaceous (Campanian–Maastrichtian) titanosaur record in South America, where their remains can be found from southern Argentina to Ecuador, with more frequent findings in Argentina and Brazil. In this chapter, we review these fossil findings and the main aspects of the taxonomy, systematics, and paleogeographic implications of this record and briefly discuss the importance of these occurrences for the understanding of titanosaur evolution. The diversity and abundance of end-Cretaceous titanosaur taxa in South America represent about 25% of the known Titanosauria species in the world, which makes them the most common group of large terrestrial herbivores of that time. Cretaceous titanosaurs from South America also vary highly in morphology and size, comprising small to large-sized taxa, for example. Their record mainly consists of appendicular and axial remains, including rare skull material, but also comprises eggs, nests, footprints, and coprolites. In South America, by the end of the Late Cretaceous, titanosaurs were generally represented by more derived titanosaurians that are mainly taxonomically assigned to more derived species within Aeolosaurini and Saltasaurinae.

Two Late Cretaceous sauropods reveal titanosaurian dispersal across South America

Article

Full-text available

Oct 2020

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.

New titanosauriform (Dinosauria: Sauropoda) specimens from the Upper Cretaceous Daijiaping Formation of southern China

Article

Full-text available

Dec 2019

Titanosauriform sauropod dinosaurs were once considered rare in the Upper Cretaceous of Asia, but a number of titanosauriforms from this stratigraphic interval have been discovered in China in recent years. In fact, all adequately known Cretaceous Asian sauropods are titanosauriforms, but only a few have been well studied, lending significance to any new anatomical information that can be extracted from Asia’s Cretaceous sauropod record. Here we give a detailed description of some titanosauriform bones recovered recently from the Upper Cretaceous Daijiaping Formation of Tianyuan County, Zhuzhou City, Hunan Province, southern China. The occurrence of this material in Hunan increases the known geographic range of titanosauriforms in eastern Asia. Although all of the specimens discussed in this paper can be assigned to Titanosauriformes at least tentatively, some bones display a limited number of features that are more typical of basal sauropods and/or derived diplodocoids, suggesting complex patterns of character evolution within Neosauropoda.

Repeated Evolution of Divergent Modes of Herbivory in Non-avian Dinosaurs

Article

Dec 2019
CURR BIOL

The importance of adaptation [1-4] versus organizational constraints [5-7] in shaping common macroevolutionary trends remains unclear [8]. The fossil record is key to this problem, as it provides data on repetitive trait evolution between lineages [4, 8]. However, quantitative analyses investigating these dynamics with fossil data are rare [8]. Herbivory evolved multiple times within Mesozoic dinosaurs [9, 10], allowing analysis of common phenotypic responses to dietary evolution. Whereas repeated patterns of character acquisition [9] and functional changes [11-13] are observed between some herbivorous dinosaur clades, biomechanical studies resolve significant differences between morphologically similar taxa [12-14]. However, previous biomechanical analyses have not accounted for phylogenetic non-independence (e.g., [13-16]) or been restricted to individual clades (e.g., [11, 12, 16]). Here, we use multivariate analysis of biomechanical characters, within a robust phylogenetic context, to investigate functional pathways to herbivory in a large sample of non-avian dinosaurs. Results demonstrate multiple solutions to herbivory. Notably, two fundamentally different modes are observed to evolve independently multiple times, with morphofunctional changes in the skull co-varying with digestive strategy. These modes distinguish between gut-processing sauropodomorphs and theropods tending toward gracile crania and low bite forces and ornithischian taxa exhibiting character complexes associated with extensive oral processing. Although convergence within these subsets of taxa is common, it is not observed between them due to functional constraints imposed during the early evolution of each group. This highlights the hierarchical nature of evolution, with adaptation driving convergence within regions of morphospace delimited by phylogenetic contingency.

Taxonomic affinities of the putative titanosaurs from the Late Jurassic Tendaguru Formation of Tanzania: Phylogenetic and biogeographic implications for eusauropod dinosaur evolution

Article

Jan 2019

The Late Jurassic Tendaguru Formation of Tanzania, southeastern Africa, records a rich sauropod fauna, including the diplodocoids Dicraeosaurus and Tornieria, and the brachiosaurid titanosauriform Giraffatitan. However, the taxonomic affinities of other sympatric sauropod taxa are poorly understood. Here, we critically reassess and redescribe these problematic taxa, and present the largest phylogenetic analysis for sauropods (117 taxa scored for 542 characters) to explore their placement in Eusauropoda. Janenschia robusta has played a prominent role in discussions of titanosaur origins, with various authors referring at least some remains to Titanosauria, a clade otherwise known only from the Cretaceous. Redescription of the holotype of Janenschia, and all referable remains, supports its validity and placement as a nonneosauropod eusauropod. It forms a clade with Haestasaurus from the earliest Cretaceous of the UK, and the Middle/Late Jurassic Chinese sauropod Bellusaurus. Phylogenetic analysis and CT scans of the internal pneumatic tissue structure of Australodocus bohetii tentatively support a non-titanosaurian somphospondylan identification, making it the only known pre-Cretaceous representative of that clade. New information on the internal pneumatic tissue structure of the dorsal vertebrae of the enigmatic Tendaguria tanzaniensis, coupled with a full redescription, results in its novel placement as a turiasaur. Tendaguria is the sister taxon of Moabosaurus, from the Early Cretaceous of North America, and is the first turiasaur recognized from Gondwana. A previously referred caudal sequence cannot be assigned to Janenschia and displays several features that indicate a close relationship with Middle–Late Jurassic East Asian mamenchisaurids. It can be diagnosed by six autapomorphies, so we erect the new taxon Wamweracaudia keranjei gen. et sp. nov. The presence of a mamenchisaurid in the Late Jurassic of southern Gondwana indicates an earlier and more widespread diversification of this clade than previously realized, prior to the geographic isolation of East Asia. Our revised phylogenetic dataset sheds light on the evolutionary history of Eusauropoda, including supporting a basal diplodocoid placement for Haplocanthosaurus, and elucidating the interrelationships of rebbachisaurids. The Tendaguru Formation shares representatives of nearly all sauropod lineages with Middle Jurassic–earliest Cretaceous global faunas, but displays a greater range of diversity than any of those faunas considered individually. Biogeographic analysis indicates that the Tendaguru sauropod fauna was assembled as a result of three main phenomena during the late Early and/or Middle Jurassic: (1) invasions from Euramerica (brachiosaurids, turiasaurs); (2) endemism in west Gondwana (dicraeosaurids, diplodocids); and (3) regional extinctions that restricted the ranges of once widespread groups (mamenchisaurids, the Janenschia lineage). Multiple dispersals across the Central Gondwanan Desert are required to explain the distributions of Jurassic sauropods, suggesting that this geographic feature was at most a filter barrier that became easier to cross during the late Middle Jurassic.

Rebbachisaurus tessonei sp nov A new Sauropoda from Albian-Cenomanian of Argentina; New evidence on the origin of the Diplodocidae

Article

Full-text available

Jan 1995
GAIA

The global sauropod fossil record

Article

Full-text available

Jan 1995

A sauropod foot from the Early Cretaceous of Western Siberia, Russia

Article

Full-text available

Feb 2002

We describe a reasonably complete sauropod foot from the Early Cretaceous (Aptian-Albian) Ilek Formation at the Shestakovo locality in Western Siberia, Russia. It shows some primitive characters, such as slender metatarsals, a relatively long second pedal ungual, and three claws. In the likely presence of the laterodistal process on the first metatarsal the Shestakovo sauropod is similar with diplodocoids, but its more elongated and gracile first metatarsal resembles brachiosaurids (Brachiosaurus, Pleurocoelus, and Cedarosaurus), titanosaurids (Laplatasaurus), and Euhelopus. Pleurocoelus-like isolated teeth from the Shestakovo assemblage may support the brachiosaurid affinities of the Shestakovo sauropod, but a strongly procoelous mid-caudal vertebra from another locality in the same formation establishes the presence of a titanosaurid in the fauna. The foot described is referred here to as Titanosauriformes gen. et sp. indet.

A new camarasaurid sauropod Opisthocoelicaudia skarzynskii gen. N. Sp. N. from the Upper Creataceous of Mongolia

Article

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Borsuk-Białynicka Magdalena.

A new sauropod tracksite from the Middle Jurassic of Portugal

Article

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Jan 1994
GAIA

Evolution of titanosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence

Article

Full-text available

Jan 1997

The phylogenetic relationships of titanosaurid sauropods are examined by means of a clodistic parsimony analysis based on postcranel features. Eusauropoda (Barapasaurus tagorei + Neosauropoda) have, at least, two synapomorphies. The Camarasauromorpha (Camarasauridae + Titanosauriformes) have five synapomorphies. The Titanosauriformes [Brachiosaurus brancai + (Chubutisaurus insignis + Titanosauria)] share six derived characters (e.g., presence of medial prespinal lamina in posterior trunk vertebrae, neural arches positioned anteriorly in mid and posterior caudal centra, claw on manual digit I reduced or absent). Chubutisaurus insignis Del Corro shares with Titanosauria one apomorphy. Titanosauria is rediagnosed based on five synapomorphies (e.g., eye-shape pleurocoels in trunk vertebrae, anterior caudals procoelous, pubis considerably longer than ischium). Titanosauridae comprises titanosaurids with: absence of hyposphene-hypantrum articulation in posterior trunk vertebrae, six sacral vertebrae, anterior caudals strongly procoelous having "ball and socket" articular faces, mid and posterior caudals strongly procoelous, semilunar sternal plates, claw on manual digit I absent, manual phalanges absent and preacetabular lobe of ilium nearly horizontal, outwardly projected. Titanosaurids more derived than Epachthosaurus sciuttoi Powell and Malawisaurus dixeyi Haughton have medial prespinal lamina formed down to the base of neural spine in posterior trunk vertebrae and quadrangular coracoids. Argentinosaurus huinculensis Bonaparte and Coria, Opisthocoelicaudia skarzynskii Borsuk-Bialynicka and Titanosauridae indet.* (DGM "Serie B") form a monophyletic group characterized by presence of accesory spino-diapophyseal laminae in trunk vertebrae. Aeolnsaurus Powell shares with Alamosaurus sanjuanensis Gilmore and the Saltasaurinae biconvex first caudal and presence of dorsal prominence on inner face of scapula. Alamosaurus sanjuanensis is the sister-taxon of the Saltasaurinae.

KT events in India: Impact, rifting, volcanism and dinosaur extinction

Article

Full-text available

Dec 1996

For more than a decade, a number of impact sites have been linked to the mass extinction at the KT (Cretaceous/Tertiary) boundary. The prime candidate today is the Chicxulub Crater in Yucatán Peninsula, Mexico. Recently another potential KT impact scar - the Shiva Crater - has been identified from subsurface data at the India-Seychelles rift margin. The crucial evidence in support of this impact structure comes from the Bombay High field, a giant offshore oil basin in India, and associated alkaline intrusives within the Deccan Traps. The KT boundary age of the crater is inferred from its Deccan lava floor, Palaeocene age of the overlying sediments, isotope dating (∼65Ma) of presumed melt rocks, and the Carlsberg rifting event (chron 29R) within the basin. Seismic reflection data and India-Seychelles plate reconstruction at 65Ma reveal a buried oblong crater, 600km long, 450km wide and 12km deep, carved through Deccan Traps and into underlying Precambrian granite. It represents the largest impact structure of Phanerozoic age. The crater shows the morphology of a complex impact structure and basin, with a distinct central uplift in the form of a series of peaks, an annular trough and a slumped rim. The oblong shape of the crater and the asymmetric distribution of fluid ejecta indicate oblique impact in a SW-NE trajectory. We speculate that a 40km diameter meteorite crashed on the western continental shelf of India around 65Ma, excavating the Shiva Crater, shattering the lithosphere and inducing the India-Seychelles rifting. The crater appears to narrow in the form of a teardrop to the NE or downrange where the ejecta melt rocks were emplaced radially outward by the impact shock. The shape of the Shiva Crater and the asymmetric ejecta distribution mimic those of artificial craters produced by oblique impacts in laboratory experiments. The synchrony and near-antipodal positions of the Shiva and Chicxulub Craters may indicate two alternative modes of their origin. Either, both craters originated from splitting of a larger diameter meteorite, or, large impact on one side of the Earth produced a similar signature on the far side by axial focusing of seismic waves. Since India was ground zero for both an impact and Deccan volcanism, their causal relationships and biotic effects were assessed. It appears that Deccan volcanism began 1Ma before the KT event and was not triggered by the impact. Its origin is attributed to the Deccan-Reunion hotspot. The extensive areal distribution of Deccan Traps is owing to intercanyon flows along the drainage of the Narmada, Godavari and the Cambay basins. During the early stage of Deccan eruption, sauropods, theropods and ankylosaurs flourished in India, but they died out suddenly at the KT impact boundary. Although both impact and Deccan volcanism are hypothesized as contributing to the deleterious environmental consequences leading to biotic crisis at the KT boundary, the impact is suggested as having played the major role as the killing mechanism.

A new sauropod from the Upper Cretaceous of Mongolia

Article

Full-text available

Jan 1983
Paleontol J

A description is given of Quaesitosaurus orientalis gen. et sp. nov., assigned to the subfamily Dicraeosaurinae. Brief data about its living habits are presented.

Cranial anatomy of Shunosaurus, a basal sauropod dinosaur from the Middle Jurassic of China

Article

Full-text available

Sep 2002

Shunosaurus, from the Middle Jurassic of China, is probably the best-known basal sauropod and is represented by several complete skeletons. It is unique among sauropods in having a small, bony club at the end of its tail. New skull material provides critical information about its anatomy, brain morphology, tooth replacement pattern, feeding habits and phylogenetic relationships. The skull is akinetic and monimostylic. The brain is relatively small, narrow and primitively designed. The tooth replacement pattern exhibits back to front replacement waves in alternating tooth position. The teeth are spatulate, stout and show well-developed wear facets indicative of coarser plant food. Upper and lower tooth rows interdigitate and shear past each other. Tooth morphology, skull architecture, and neck posture indicate that Shunosaurus was adapted to ground feeding or low browsing. Shunosaurus exhibits the following cranial autapomorphies: emargination of the ventral margin of the jugal/quadratojugal bar behind the tooth row; postorbital contains a lateral pit; vomers do not participate in the formation of the choanae; pterygoid is extremely slender and small with a dorsal fossa; quadrate ramus of the pterygoid is forked; quadratojugal participates in the jaw articulation; tooth morphology is a combination of cylindrical and spatulate form; basipterygoid process is not wrapped by the caudal process of the pterygoid; trochlear nerve has two exits; occlusal level of the maxillary tooth row is convex downward, whereas that of the dentary is concave upward, acting like a pair of garden shears; dentary tooth count is 25 or more; and the replacing teeth invade the labial side of the functional teeth. Cranial characters among the basal sauropods are reviewed. As Shunosaurus is the earliest sauropod for which cranial remains are known, it occupies an important position phylogenetically, showing the modification of skull morphology from the prosauropod condition. Although the skull synapomorphies of Sauropoda are unknown at present, 27 cranial synapomorphies are known for the clade Eusauropoda. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136, 145−169.

Palaeobiology: A refugium for relicts

Article

Full-text available

Jul 1999

Zhe-Xi Luo

The transition between the Late Jurassic and Early Cretaceous, 157-100 million years (Myr) ago, is a defining time in the history of terrestrial biodiversity. It witnessed the descent of birds from two-legged, meat-eating dinosaurs1,2, and their early diversification3, 4, 5; the rapid evolution of non-bird dinosaurs; diversification of the major mammalian groups6,7; the origins of flowering plants (angiosperms)8; and diversification of the nectar-feeding flies — the finest early examples of plant-insect coevolution9,10. These emerging lineages came to dominate the world's terrestrial biotas, and some are still thriving today.

Stratigraphic sequence and vertebrate-bearing beds of the lower Yixian Formation in Shetun and the neighboring area, western Liaoning, China

Article

Full-text available

Jan 1998

Jaw mechanics in sauropod dinosaurs

Article

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Jan 1994
GAIA

Jorge Orlando Calvo

A study of the movement of jaw mechanics in sauropod dinosaurs.

Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages

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Full-text available

Feb 2004

The Cretaceous terrestrial strata of the Neuquén Basin (northern Patagonia, Argentina) are described together with their tetrapod records. Six local tetrapod assemblages are identified: Amargan (Barremian–Early Aptian), Lohancuran (Late Aptian–Albian), Limayan (Cenomanian–Early Turonian), Neuquenian (Late Turonian–Coniacian), Coloradoan (Santonian–Early Campanian) and Allenian [Late Campanian–Early Maastrichtian (= Alamitense = Alamitian SALMA)]. The last of these includes records from north-eastern Patagonia.

Remains of Sauropoda (Reptilia, Saurischia) in the Lower Cretaceous Upper Hauterivian/Lower Barremian) limestones of SW Istria (Croatia).

Article

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Jan 1998

Fabio Marco Dalla Vecchia

A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. An Empirical Search for Interconnected Patterns of Natural History

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Apr 1998
COPEIA

The comparative osteology, phylogenetic relationships, and historical biogeography of all known taxa of fossil and living amiid fishes (Halecomorphi: Amiidae) are investigated in detail. Previously, the detailed osteology of nearly all fossil amiids was unknown. We present the first well-supported comprehensive phylogeny for fossil and living amiid fishes. We synthesize clearly documented phylogenetic data on amiids and other halecomorph fishes with other historical phenomena such as ontogeny, historical biogeography, stratigraphic paleontology, and paleoecology (both “stationary” and “historical”). We also use our study of halecomorph fishes as a platform to explore several fundamental methodological and theoretical concepts important to phylogenetic/evolutionary investigations. These concepts pertain mainly to (1) the use of comparative empirical data to interpret various historical patterns and (2) the practice of integrating fossil and living species together in original (i.e., non-literature-based) phylogenetic studies.As proposed by Patterson (1973), Amia calva is the sole surviving member of a formerly diverse clade, Halecomorphi. Even Amiidae (the halecomorph subgroup that is the focus of this study) was taxonomically diverse and widespread during Mesozoic and Paleogene times. Amiidae here includes only those amiiform fishes that have solid perichordally ossified diplospondylous centra of both the “normal” (a term used here for non-alternating) and the alternating type in the caudal region. Consequently, †Sinamiidae and †Caturoidea (†Caturidae plus †Liodesmidae) are excluded from the family Amiidae. To set the style and terminology for description of the fossil taxa, and to present a fresh look at the osteology and development of the only living amiiform, we redescribe Amia calva in detail using modern methods of preparation and illustration. Detailed study of Amia calva is critical for interpreting probable intraspecific variation and ontogeny in fossil skeletons. We examined individual variation of both bone morphology and developmental timing in Amia calva.We classify the family Amiidae into four subfamilies here: †Amiinae (including †Amia, †Cyclurus, †Pseudamiatus, and † “Amia” hesperia), †Vidalamiinae subfam. nov. (including † Vidalamia, †Pachyamia, †Melvius, †Calamopleurus, and †Maliamia), †Solnhofenamiinae subfam. nov. (including †Solnhofenamia gen. nov.), and †Amiopsinae subfam. nov. (including †Amiopsis). The genus †Nipponamia remains Amiidae subfamily indeterminate until additional material can be found and studied, although it does not appear to belong to Amiinae or †Amiopsinae subfam. nov. as defined here. Other nominal genera of Amiidae are discussed as nomina nuda or nomina dubia.We found Amiinae to be a clearly monophyletic group diagnosed by numerous synapomorphic characters. This is the only amiid (and halecomorph) subfamily known to have survived beyond the early Eoccne. It was a diverse group with a known stratigraphic range of Late Cretaceous through the present. The earliest diagnosable species in the subfamily is †Cyclurus fragosus from the upper Maastrichtian of Alberta, Canada, and the earliest Amiinae indeterminate is a collection of fragments from the upper Cenomanian of Uzbekhistan (“?Amia semimarina” Nessov 1985, a nomen dubium). Earlier forms reported by Boreske (1974) could not be verified as Amiinae. Amiinae was widespread and particularly speciose during the Eocene, and appears to have been confined almost exclusively to fresh water. The extremely rare amiine fossil fragments from brackish water deposits probably represent accidental or, at most, occasional migration into brackish environments or possibly entrapment in a drying water system. Amiinae includes three valid species of Amia (including †A. pattersoni sp. nov.), eight valid species of †Cyclurus (all of which are described here), and † “Amia” hesperia (a valid species of uncertain generic affinity). It also includes the genus †Pseudamiatus which remains †Amiinae indeterminate, until the type and only known specimen can be further prepared or until additional material can be found. It probably belongs in Amia or †Cyclurus as those genera are defined here. We also review more than 30 other nominal species of amiines, all of which we believe are invalid names (either nomina dubia, nominanuda, or subjective junior synonyms) but some of which nevertheless extend the stratigraphic and geographic range of the subfamily Amiinae. Although we clarify the known diversity and monophyly of Amiinae, and add new morphological information about numerous amiine species, further materials and work are needed to resolve phylogenetic interrelationships within this subfamily.†Vidalamiinae subfam. nov. is a previously unrecognized, diverse group of amiid taxa, several of which reach very large sizes (to about two meters total length). This well-supported monophyletic subfamily is known only from the Early Cretaceous to the early Eocene, and contains two well-supported monophyletic subgroups: †Vidalamiini tribe nov. and †Calamopleurini tribe nov. These tribes have interesting biogeographic distributions that seem incongruent with today's geography, but these distributions make intuitive sense given current interpretations of the paleogeography of the Early Cretaceous (illustrated here). †Vidalamiini tribe nov. includes †Vidalamia (one species from coastal estuarine/lagoonal deposits of Spain), †Pachyamia (two species: one from marine deposits of the Middle East and a new species from marine deposits in Mexico) and †Melvius (two species from deposits along the margin of the Upper Cretaceous North American Seaway). During the Early Cretaceous, this seemingly far-flung distribution was connected by a continuous shallow marine continental margin and seaway. All five species of †Vidalamiini tribe nov. are described in detail here. †Calamopleurini tribe nov. includes †Calamopleurus (three species: one from an inconclusively determined paleoenvironment of eastern Brazil, one species from a probable freshwater paleoenvironment of eastern Brazil, and a new species from a yet unknown paleoenvironment of Morocco) and †Maliamia (one species from west-central Africa in deposits of unknown water chemistry). Most of these species (particularly †C. cylindricus) are described in detail here. †Vidalamiinae subfam. nov. is the sister group to Amiinae, and the two subfamilies together form the supersubfamily Amiista nuper interposita. The term “nuper interposita” is introduced here to indicate the first published use of new names inserted between existing family group names.†Solnhofenamiinae subfam. nov. is a Late Jurassic marine group from Europe (Germany and France) currently containing a single species, †Solnhofenamia elongata gen. nov. This species was formerly placed in the genus † Urocles as † “Urocles” elongatus. However, the genus † Urocles is invalid in our scheme because the type species of †Urocles is congeneric with †Amiopsis, and the name †Amiopsis has priority. We find that † “Urocles” elongatus is more closely related to a group containing Amiinae plus †Vidalamiinae subfam. nov., than it is to the type species of the genus †Urocles (= †Amiopsis lepidota here). Therefore, we place †“Urocles” elongatus in the new genus †Solnhofenamia. Because †S. elongata gen. nov. is the sister group to a group containing Amiinae plus †Vidalamiinae subfam. nov., we put it into †Solnhofenamiinae subfam. nov. We describe this species in detail for the first time.†Amiopsinae subfam. nov. is a poorly supported stem group of amiids from Late Jurassic to late Cretaceous (Turonian) marine and freshwater deposits of Europe (Yugoslavia, Germany, Spain, England, Belgium, and possibly France). This group, with five valid species, may be non-monophyletic. †Amiopsinae subfam. nov. contains most of the amiids excluded from the hypersubfamily Amiida nuper interposita, a monophyletic group containing ((Amiinae + †Vidalamiinae subfam. nov.) + †Solnhofenamiinae subfam. nov.). All five species of †Amiopsis are described here with much new detail.The phylogenetic position and biogeographic significance of the single known, poorly preserved specimen of †Nipponamia, from Early Cretaceous freshwater deposits of Japan, is largely unknown. Additional material is needed to better understand its morphology.In addition to our cladogram of Amiidae, we produced a cladogram of Halecomorphi. Our sample of non-amiid halecomorph taxa was far less complete than our sample of amiid taxa; nevertheless we found several well-supported nodes within non-amiid halecomorphs which can serve as general guides for future research.We discuss numerous general methodological, philosophical, and theoretical concepts in this paper, including the construction of taxonomic diagnoses, the treatment of undiagnosable taxa, and the treatment of ontogenetically variable characters. We review the effects on phylogenetic analysis of problematic (e.g., “missing”) data entries resulting from either problematic taxa (e.g., highly incomplete fossil taxa) or problematic characters (characters whose states are unknown for most taxa). Various types of problematic data are also reviewed. We discuss the exclusion of certain problematic taxa (here termed “inserted” taxa) and problematic characters (here termed “mapped” characters) from phylogenetic analyses. We also examine the effects of phylogenetically “redundant” taxa and consider the comparative value of wellresolved nodes versus completely resolved trees in cladistic studies. These concepts and terms can all be located in this volume by using the table of contents or the subject index.Our study exemplifies the large amount of natural historical information that can be interpreted from multidisciplinary pattern studies of fossil and living actinopterygian fishes. We term our general approach to the study of natural history as “an empirical synthetic pattern approach”, an exploratory method whose fundamentals go back to the 19 century naturalist Louis Agassiz (1807–1873). Many other actinopterygian groups of equal potential remain virtually unstudied with regard to their broad historical significance (e.g., phylogenetic pattern congruence between comparative morphology, ontogeny, biogeography, and stratigraphy). Exceptional preservation and abundant poorly known material make fossil actinopterygians one of the greatest remaining frontiers in vertebrate paleontology.

Titanosaurs and the origin of "wide-gauge" trackways: A biomechanical and systematic perspective on sauropod locomotion

Article

Jan 1999

Two major ichnotypes of sauropod trackways have been described: "narrow-gauge," in which both manus and pes prints approach or intersect the trackway midline, and "wide-gauge," in which these prints are well apart from the midline. This gauge disparity could be the result of differences in behavior, body size, or morphology between the respective trackmakers. However, the biomechanics of locomotion in large terrestrial vertebrates suggest that sauropods were probably restricted in locomotor behavior, and the lack of systematic size differences between footprint gauges argues against body-size-related influences. We argue that skeletal morphology is responsible for gauge differences and integrate data from locomotor biomechanics and systematics with the track record to predict the hindlimb morphology of wide-gauge trackmakers. Broader foot stances in large, graviportal animals entail predictable mechanical consequences and hindlimb modifications. These could include outwardly angled femora, offset knee condyles, and a more eccentric femoral midshaft cross-section. A survey of sauropod hindlimb morphology reveals that these features are synapomorphies of titanosaurs, suggesting that they were the makers of wide-gauge trackways. The temporal and geographic distribution of titanosaurs is consistent with this hypothesis because wide-gauge trackways predominate during the Cretaceous and are found worldwide. Additional appendicular synapomorphies of titanosaurs are interpreted in light of identifying these animals as wide-gauge trackmakers. We suggest that titanosaurs may have used a bipedal stance more frequently than did other sauropods. These correlations between ichnology, biomechanics, and systematics imply that titanosaurs were unique among sauropods in having a more varied repertoire of locomotor habits.

Dinosaur teeth from Lameta Group (Upper Cretaceous) of Kheda District, Gujarat ( India).

Article

Jun 1987
J GEOL SOC INDIA

Theropod and sauropod dinosaur teeth are being described for the first time from Lameta Group (Upper Cretaceous) of Kheda District, Gujarat. Carnosaurian teeth show megalosaurid characters and are placed in Majungasaurus (Megalosaurus) crenatissimus and (?) Megalosaurus. Five morphological types of (?) Megalosaurus teeth have been distinguished which vary from laterally compressed flattened cones to recurved ones having serrations on anterior/posterior margins and directed either at right angles or obliquely to the margins. The sauropod dinosaur teeth are tentatively place in Titanosaurus and described as a new species viz., (?) Titanosaurus rahioliensis. -Authors

Sauropoda (Reptilia, Saurischia) from the Cretaceous of Queensland

Article

Osteológia de Saltasaurus loricatus (Sauropoda Titanosauridae)

Article

Jan 1992

J.E. Powell

Principal characters of American Jurassic dinosaurs. Part I

Article

Nov 1878

O.C. Marsh

Osteology of the Reptiles

Article

Jan 1956

A.S. Romer

[Some results of the studies of the Upper Cretaceous dinosaurian fauna from the vicinity of the Station Sary-Agach, south Kazakhstan]

Article

A.N. Riabinin

The Russian-Mongolian expeditions and research in vertebrate paleontology

Article

Jan 2000

Sauropodomorph Diversity through Time: Paleoecological and Macro Evolutionary Implications

Chapter

Dec 2005

This chapter investigates a number of potential macroevolutionary mechanisms that may account for sauropodomorph diversity, including various potential clade-clade interactions (coevolution and competition). It also examines the possibility that the observed changes may be at least partially accounted for by fluctuations in the frequencies of different sauropodomorph feeding mechanisms through time. There was considerable temporal overlap between prosauropods and sauropods, extending from the late Carnian to the end of the Pliensbachian. Moreover, the possible roles of several biological processes that may have influenced sauropod diversity through time are assessed. Comparisons of sauropodomorph diversity with information on Mesozoic floras reveal one possible incidence of coevolution, between titanosaurs and angiosperms, in the Late Cretaceous. The strong correlation between diversity and feeding ecology shows that herbivory and the various adaptive complexes that arose to deal with a diet of plants were central to the radiation of sauropodomorphs in the Middle and Late Jurassic.

Cranial osteology of Amargasaurus cazaui Salgado & Bonaparte (Sauropoda, Dicraeosauridae) from the Neocomian of Patagonia

Article

Jan 1992

Amargasaurus cazaui Salgado and Bonaparte, from the Hauterivian of Neuquen Province, Argentina, is a recently found representative of the family Dicraeosauridae originally erected to include Dicraeosaurus hansemanni and Dicraeosaurus sattleri both from the upper Jurassic of Tendaguru, Tanzania and probably Kazdi, Zimbabwe. Most of the skeleton of A. cazaui was discovered, including a well-preserved braincase which closely resembles that of Dicraeosaurus hansemanni, the only African species in which the skull is partly known. The study of adequately preserved skulls of Dicraeosaurus and Amargasaurus is important for the recognition of derived cranial features that partly diagnose the group. A preliminary analysis of those characters is presented in this paper. -from Authors

The skull of Diplodocus

Article

W.J. Holland

A new sauropod dinosaur of Cretaceous from Jiangshan, Zhejiang Province

Article

Jan 2001

Les dinosauriens jurassiques de Damparis (Jura)

Article

A.F. de Lapparent

Las capas con dinosaurios en la costa sur del R??o Negro, frente a General Roca

Article

R. Wichmann

New archosaurs from the Jurassic of Siberia and Mongolia

Article

Jan 2003

New finds of crocodiles and dinosaurs from the Late Jurassic deposits of southwestern Mongolia (Shar-Teg locality) and Eastern Siberia (basin of the Vilyui River, Teete locality) are described. A new species of small-sized running crocodiles, Nominosuchus arcanus, characterized by a small number of teeth is described from the Shar-Teg locality on the basis of the anterior parts of the skull. A Jurassic assemblage of dinosaurs, including Stegosaurus sp., sauropods resembling Camarasaurus, and predatory theropods, including Allosaurus sp., is established for the first time on the basis of the material from the Teete locality in Siberia. This corroborates the presence of the Zoogeographic relationship between the North American and Siberian faunas at that time.

Skull and atlas-axis complex of the Upper Jurassic sauropod Camarasaurus Cope (Reptilia: Saurischia)

Article