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Principal characters of American Jurassic dinosaurs. Part I
... As for Madzia et al. (2021). The smallest clade containing Camptosaurus dispar (Marsh, 1879), Dryosaurus altus (Marsh, 1878), and Gasparinisaura cincosaltensis Coria & Salgado, 1996, provided that it does not include Tenontosaurus tilletti Ostrom, 1970. This is a minimum-clade definition. ...
... This is a minimum-clade definition. Abbreviated definition: min r (Camptosaurus dispar (Marsh, 1879) & Dryosaurus altus (Marsh, 1878) & Gasparinisaura cincosaltensis Coria & Salgado, 1996j $ Tenontosaurus tilletti Ostrom, 1970. ...
... Dinosauria Owen [39] Sauropoda Marsh [40] Turiasauria Royo-Torres et al. [3] Turiasauria indet. ...
... The strict consensus analysis recovered the Danish OTU in a polytomy within Turiasauria (Narindasaurus, Moabosaurus+Tendaguria+Turiasaurus, Zby and Losillasaurus). The character 402 of Royo-Torres et al. [3] (which is based on Mannion et al. [40] (Teeth, D-shaped crown morphology in labial/lingual view narrows mesiodistally along its apical half, giving it a 'heart'-shaped outline)) [1,7,41] is synapomorphic of Turiasauria, and present is the Danish tooth. The analysis Majority Rule with the 50% cutout resulted clade that includes the European turiasaurs (Zby atlanticus, Turiasaurus riodevensis, and Losillasaurus giganteus). ...
Turiasauria is a clade of basal sauropod dinosaurs hitherto only known from the Middle Jurassic (Bathonian) to the Lower Cretaceous (Valanginian). A new find of a shed tooth crown from the Lower Jurassic (Pliensbachian), Halse Formation of Bornholm, Denmark, is spoon-like, asymmetrical, and heart-shaped, which identifies the tooth as turiasaurian, pushing the origin of the Turiasauria some 17 My back into the Lower Jurassic. This suggests a North Pangean/Laurasian origin of the turiasaurian clade, which then, during the Middle to Late Jurassic, dispersed through Europe, India, and Africa, with their latest representatives found in the Early Cretaceous of England and North America. Furthermore, this is the first record of a sauropod from the Pliensbachian in Europe.
... As in other sauropods, the fourth trochanter in ZPAL MgD-III/22 is reduced and forms a crest or ridge (a sauropod synapomorphy), in contrast to the condition in basally branching sauropodomorphs (e.g., Plateosaurus von Meyer 1837), in which the fourth trochanter is prominent (Gauthier, 1986;Marsh, 1878;McIntosh, 1990;Raath, 1972;Riggs, 1904;Wilson, 2002;Wilson & Sereno, 1998). The femur has two synapomorphies of Titanosauriformes: the presence of a femoral shaft with a lateral bulge (= abductor crest) and a medial deflection of the proximal one-third of the femur (McIntosh, 1990;Salgado & Coria, 1993;Salgado et al., 1997;Wilson, 2002). ...
... Theropoda Marsh, 1881 [77]. ...
Unenlagiine paravians are among the most relevant Gondwanan theropod dinosaur clades for understanding the origin of birds, yet their fossil record remains incomplete, with most taxa being represented by fragmentary material and/or separated by lengthy temporal gaps, frustrating attempts to characterize unenlagiine evolution. Here we describe Diuqin lechiguanae gen. et sp. nov., a new unenlagiine taxon from the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Basin of Neuquén Province in northern Patagonia, Argentina that fills a substantial stratigraphic gap in the fossil record of these theropods. Although known only from a very incomplete postcranial skeleton, the preserved bones of Diuqin differ from corresponding elements in other unenlagiines, justifying the erection of the new taxon. Moreover, in several morphological aspects, the humerus of Diuqin appears intermediate between those of geologically older unenlagiines from the Neuquén Basin (e.g., Unenlagia spp. from the Turonian–Coniacian Portezuelo Formation) and that of the stratigraphically younger, larger-bodied Austroraptor cabazai from the Campanian–Maastrichtian Allen Formation. Consequently, the morphology of the new taxon appears to indicate a transitional stage in unenlagiine evolution. Phylogenetic analysis recovers Diuqin as a paravian with multiple plausible systematic positions, but the strongest affinity is with Unenlagiinae. The humerus of the new form exhibits subcircular punctures near its distal end that are interpreted as feeding traces most likely left by a conical-toothed crocodyliform, mammal, or theropod, the latter potentially corresponding to a megaraptorid or another unenlagiine individual. Thus, in addition to filling important morphological and temporal gaps in unenlagiine evolutionary history, the new taxon also offers information relating to the paleoecology of these theropods.
... Sauropoda Marsh, 1878Titanosauriformes Salgado et al., 1997Titanosauria Bonaparte and Coria, 1993Lithostrotia Upchurch et al., 2004 Tiamat gen. nov. ...
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.
... Allosauroidea (Marsh, 1878) sensu Sereno 1998 Allosauroidea indet. Previous identifications: MG 15 and another tooth crown fragment (currently lost) from Cabo Espichel were described by Sauvage (1897Sauvage ( -1898 and assigned to Megalosaurus aff. ...
Malafaia, E., Mocho, P., Escaso, F., Narvaéz, I., and Ortega, F. 2024. Taxonomic and stratigraphic update of the material
historically attributed to Megalosaurus from Portugal. Acta Palaeontologica Polonica 69 (2): 127–171. https://doi.org/10.4202/app.01113.2023
... These early endocasts were initially cast using plaster first, and later took advantage of latex and silicone as casting materials. It was Othniel C. Marsh, a pioneer worker in dinosaur paleoneurology, who studied around a dozen of dinosaur cranial endocasts, including sauropods, theropods, and ornithischians from North America (e.g., Marsh, 1881Marsh, , 1884aMarsh, ,b, 1890Marsh, ,1894Marsh, , 1896. Nowadays, digital techniques, such as computed tomography, allow paleontologists to construct digital 3D models that, in turn, can be made into physical objects using 3D printing--regardless of whether or not the endocranial cavity is filled with sediment. ...
We present here a natural cranial endocast assigned to an abelisaurid theropod found in Cretaceous rocks of the outcropping Bajo de la Carpa Formation (Santonian) in Neuquén Province, Northern Patagonia, Argentina. The specimen was found in association with fragmentary braincase remains, which include an otic capsule and part of the skull roof. These fragments bear abelisaurid features that support the taxonomic assignment. The general shape of the endocast is similar to that in other abelisaurids, being anteroposteriorly elongated with long and robust olfactory tract and olfactory bulbs, rounded cerebral hemispheres, and pronounced and triangular dural peak. It is the second natural endocast described for a dinosaur in Argentina and the first for a theropod. The comparison with other Patagonian abelisaurids indicates the endocast belonged to a small to mid-sized specimen that highly resembles that of Viavenator and Llukalkan. However, the skull roof ornamentation is markedly different, and comments are made on certain features of the ornamentation of the frontal in the new specimen and other close relatives.
... DINOSAURIA (Owen, 1842) SAURISCHIA (Seeley, 1888) SAUROPODOMORPHA (Huene, 1932) SAUROPODA (Marsh, 1878) TITANOSAURIA (Bonaparte and Coria, 1993) Saltasauridae (Bonaparte and Powell, 1980) Materials NVP016; complete left humerus (Figure 2) ...
... DINOSAURIA (Owen, 1842) SAURISCHIA (Seeley, 1888) SAUROPODOMORPHA (Huene, 1932) SAUROPODA (Marsh, 1878) TITANOSAURIA (Bonaparte and Coria, 1993) Saltasauridae (Bonaparte and Powell, 1980) Materials NVP016; complete left humerus (Figure 2) ...
The Late Cretaceous deposits in the south of the Western Desert in the Dakhla Basin are well exposed, comprising variegated shales which contain a variety of vertebrates. In this contribution, we describe a new sauropod specimen from the Quseir Formation, represented by an almost complete humerus. The humerus shows a set of morphological features that allow us to refer it to the Saltasauridae, such as divided and well-developed distal condyles. Saltasaurids are ones of the smallest sauropod dinosaurs. The saltasaurids are newly recorded in Africa, although it was previously discovered on almost all the other continents in the Late Cretaceous. This study mentions the first record of saltasaurid humerus in Africa. ARTICLE HISTORY
... By 1879, he had concluded that Stegosaurus was indeed a dinosaur, but no figures had yet been published (Marsh, 1879). The first illustrations of Stegosaurus specimens, still including the erroneously identified sauropod teeth, were published in 1881, showing an endocranial cast, vertebrae, girdle and limb bones and bony plates (Marsh, 1881). Stegosaurs were interpreted as herbivorous, more or less aquatic in habits, but probably bipedal when on land, because of the great difference in length between the fore-and hindlimbs. ...
Because of its strange appearance, the Jurassic dinosaur Stegosaurus has been depicted in many life reconstructions by various palaeoartists ever since the first skeletal reconstruction was published by O.C. Marsh in 1891. However, even before that, the French illustrator Auguste Jobin produced a life reconstruction of Stegosaurus in a Jurassic landscape, showing it as a bipedal animal with the back and tail covered with bony spikes and plates. This reconstruction was first published in
the French popular science magazine Science et Nature in 1884 and then republished the same year in Scientific American. It was then reprinted in French books in 1885 and 1886. Jobin’s Jurassic landscape also included a reconstruction of Camptosaurus (then known as Comptonotus) as a bipedal, long-necked animal. Although Jobin worked under the supervision of the French dinosaur expert Henri Emile Sauvage, his reconstructions necessarily reflected the incomplete information available at the
time about these dinosaurs, as well as O.C. Marsh’s erroneous early interpretations of Stegosaurus. Even after the publication of Marsh’s 1891 skeletal reconstruction of Stegosaurus as a quadrupedaldinosaur, an 1892 American life reconstruction of a stegosaur still showed it in a bipedal stance.
... Ornithischia Seeley, 1888 [53] Ornithopoda Marsh, 1881 [54] Iguanodontia Baur, 1891 [55] Rhabdodontomorpha [37] Heterodefinitional junior synonym. Rhabdodontoidea [32] Remarks Madzia et al., [28] provided a stem-based definition of Rhabdodontomorpha, converting the node-based definition provided by Dieudonné et al., [37]. ...
Intensifying macrovertebrate reconnaissance together with refined age-dating of mid-Cretaceous assemblages in recent decades is producing a more nuanced understanding of the impact of the Cretaceous Thermal Maximum on terrestrial ecosystems. Here we report discovery of a new early-diverging ornithopod, Iani smithi gen. et sp. nov., from the Cenomanian-age lower Mussentuchit Member, Cedar Mountain Formation of Utah, USA. The single known specimen of this species (NCSM 29373) includes a well-preserved, disarticulated skull, partial axial column, and portions of the appendicular skeleton. Apomorphic traits are concentrated on the frontal, squamosal, braincase, and premaxilla, including the presence of three premaxillary teeth. Phylogenetic analyses using parsimony and Bayesian inference posit Iani as a North American rhabdodontomorph based on the presence of enlarged, spatulate teeth bearing up to 12 secondary ridges, maxillary teeth lacking a primary ridge, a laterally depressed maxillary process of the jugal, and a posttemporal foramen restricted to the squamosal, among other features. Prior to this discovery, neornithischian paleobiodiversity in the Mussentuchit Member was based primarily on isolated teeth, with only the hadrosauroid Eolambia caroljonesa named from macrovertebrate remains. Documentation of a possible rhabdodontomorph in this assemblage, along with published reports of an as-of-yet undescribed thescelosaurid, and fragmentary remains of ankylosaurians and ceratopsians confirms a minimum of five, cohabiting neornithischian clades in earliest Late Cretaceous terrestrial ecosystems of North America. Due to poor preservation and exploration of Turonian–Santonian assemblages, the timing of rhabdodontomorph extirpation in the Western Interior Basin is, as of yet, unclear. However, Iani documents survival of all three major clades of Early Cretaceous neornithischians (Thescelosauridae, Rhabdodontomorpha, and Ankylopollexia) into the dawn of the Late Cretaceous of North America.
... Sauropoda [94] Macronaria [95] Titanosauriformes [96,97] Somphospondyli [95] Diamantinasauria [41] Diamantinasaurus matildae [9] 4.1. Holotype specimen AODF 0603 ('Matilda'; AODL 0085): dentary fragment, tooth, three partial cervical ribs, three incomplete dorsal vertebrae, dorsal ribs, fragmentary gastralia, five coalesced sacral vertebrae, isolated sacral processes, right and left scapulae, right coracoid, partial right sternal plate, right and left humeri, right and left ulnae, right radius, right and left metacarpals I-V, eight manual phalanges (including right manual ungual I-2), right and left ilia, right and left pubes, right and left ischia, right femur, right tibia, right fibula, right astragalus, associated fragments [37,43]. ...
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.
The Ojinaga Basin is crucial for understanding the southern province of Laramidia because it contains a unique dinosaur fauna on the North American continent. The Upper Cretaceous Aguja and Javelina formations contain fossil remains of the dinosaur families Hadrosauridae, Ceratopsidae, Nodosauridae, Tyrannosauridae, and Saltasauridae. The latter is the first evidence for a saltasaurid taxon from Mexico identified as Alamosaurus sanjuanensis.
Fieldwork in the late 1980s in the Otlaltepec Formation Middle Jurassic (Bathonian-Callovian) of southern Puebla resulted in the recovery of the first osteological record of a Flagellicaudata dinosaur from Mexico and the southern-most for North America. The material is represented by metatarsal fragments of the right pes, showing autapomorphies in metatarsal II for Flagellicaudata. The available material is incomplete and the sample remains small, but it suggests the possible presence of a new taxon. This specimen provides data on the distribution and diversity of sauropod dinosaurs of southern North America during the Middle Jurassic.
The Barremian-aged Wessex Formation of the Isle of Wight, UK, offers a globally significant glimpse into the sauropod dinosaur faunas of the early Cretaceous. These deposits have yielded specimens of several neosauropod lineages, such as rebbachisaurids, titanosauriforms (including some of the earliest titanosaur remains), and possible flagellicaudatans. Here, we report an undescribed sauropod partial hindlimb from the Wessex Formation (NHMUK PV R16500) and analyse its phylogenetic affinities. This hindlimb preserves the left tibia, astragalus and pes, lacking only a few phalanges. NHMUK PV R16500 can be diagnosed based on two autapomorphies: an unusually high distal end to midshaft transverse width ratio in metatarsals III and IV, and the presence of small bump-like projections located in the centre of the proximal articular surfaces of the unguals of pedal digits I and II. The phylogenetic affinities of NHMUK PV R16500 are uncertain: although our analyses recover it as an early-branching somphospondylan, a single character change moves it to close to Flagellicaudata when extended implied weighting is applied. The possibility of flagellicaudatan affinities for NHMUK PV R16500 implies a potential ghost lineage that survived the Jurassic/Cretaceous boundary; however, we present evidence that the somphospondylan position is more probable and should be preferred.
The Kem Kem Group is a lowermost lithostratigraphic unit from the Upper Cretaceous that extends along the border between Algeria and Morocco, in the northern region of Africa. This geological unit has yielded several tetrapod fossils, including a well-represented assemblage of theropod dinosaurs, after more than eight decades of research. Here, we report new occurrences of spinosaurid theropods from the spinosaurine clade in the Kem Kem Group by providing anatomical descriptions and taxonomic identifications of 11 new specimens derived from the Tafilalt region of Morocco. Among the findings, we describe a cervical vertebra of Sigilmassasaurus, in addition to several cranial, axial, and appendicular elements that can safely be attributed to Spinosaurinae. Moreover, based on a unique combination of characteristics, we also describe an isolated and partial ischium belonging to an indeterminate carcharodontosaurid. We also deliver a detailed redescription of one of the most complete snouts of a spinosaurine known to date. Therefore, the theropod dinosaurs of the Kem Kem Group show considerable diversity, but many questions, especially related to the diversity of spinosaurids and the general abundance of carnivorous dinosaurs in this region, remain unclear until new materials are discovered and complete descriptions are made.
Isolated theropod teeth are one of the most common vertebrate fossils that have been found in the Khorat Group of Thailand. Furthermore, several isolated teeth have been discovered from the Upper Jurassic Phu Kradung Formation, located in Phu Noi locality of Kalasin Province, Northeastern Thailand. Three of those theropod teeth from the Phu Noi locality show unique dental features that can be distinguished from previous discovered metriacanthosaurid theropod, including the lateral teeth with mesiolingual twisted mesial carinae extending above the cervix line and braided enamel surface texture. Morphological examination with cladistics and morphometric analyses show that these isolated teeth exhibit the synapomorphies of basal tyrannosauroids, closely related to Guanlong wucaii and Proceratosaurus bradleyi from the Jurassic Period. This paper notes the first report of a basal tyrannosauroid in Southeast Asia as well as significantly contributes to our understanding of paleoecology of the Upper Jurassic Phu Kradung Formation and paleobiogeography of Tyrannosauroidea during the Jurassic Period.
The Upper Cretaceous sauropod fossil record from Romania is abundant, mostly originated from the Maastrichtian deposits of the western-southwestern margin of the Transylvanian Basin, and in the Hațeg and Rusca Montana basins. Most specimens were found in isolation or in low degree of association and only few partial skeletons have been reported. The presence of at least four taxa was recently considered, including three defined forms: Magyarosaurus dacus, Paludititan nalatzensis and “Magyarosaurus” hungaricus. However, the phylogenetic affinities of these taxa within Lithostrotia are still under debate. A large sample of appendicular remains, predominantly composed by unpublished specimens, is described here in detail to provide new data about the diversity of the sauropods of the Hațeg Island during the Maastrichtian. All specimens show affinities or are compatible with lithostrotian sauropods, even if the availability of characters of some of them does not allow its attribution to this clade. Five morphotypes for the femora, three to four for the humeri, three for the fibulae, and two for the radii, ulnae, manus, pubes, ischia, tibiae, and pedes are established, supporting the presence of four or five taxa in this domain. A unique partial manus morphology characterized by its extreme gracile metacarpals is reported, only surpassed by an unpublished manus found in the Spanish Lo Hueco fossil-site (late Campanian-early Maastrichtian), suggesting that a titanosaurian lineage with extremely elongated manus inhabited the European realm, in both Hațeg and Ibero-Armorican islands, at the end of the Mesozoic.
Being one of the first dinosaurs discovered in Romania, Elopteryx nopcsai is a Paravian dinosaur species whose described material is mainly based on proximal femur fragments. All the known remains assigned to this taxon have been collected from the latest Cretaceous (Maastrichtian) deposits of the Hațeg Basin. A similar fragment was collected from the Nălaț-Vad locality and is herein described. It shares multiple similarities with specimens previously related to Elopteryx and fossils related to other taxa, such as Pengornithidae and Oviraptorosauria clades, mentioned herein. The tumultuous history of the systematic classification, its possible synonymy with other taxa, and some aspects regarding the paleoecology of this species are also included in this paper.
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.
Supposed dinosaur remains were collected between 1859 and 1906 in the Lower Cretaceous Recôncavo Basin (Northeast Brazil). Since these materials remained undescribed, and most were considered lost. Recently, some of these historical specimens were rediscovered in the Natural History Museum of London, providing an opportunity to revisit them after 160 years. The specimens come from five different sites, corresponding to the Massacará (Berriasian-Barremian) and Ilhas (Valanginian-Barremian) groups. Identified bones comprise mainly isolated vertebral centra from ornithopods, sauropods, and theropods. Appendicular remains include a theropod pedal phalanx, humerus, and distal half of a left femur with elasmarian affinities. Despite their fragmentary nature, these specimens represent the earliest dinosaur bones discovered in South America, enhancing our understanding of the Cretaceous dinosaur faunas in Northeast Brazil. The dinosaur assemblage in the Recôncavo Basin resembles coeval units in Northeast Brazil, such as the Rio do Peixe Basin, where ornithopods coexist with sauropods and theropods. This study confirms the presence of ornithischian dinosaurs in Brazil based on osteological evidence, expanding their biogeographic and temporal range before the continental rifting between South America and Africa. Additionally, these findings reinforce the fossiliferous potential of Cretaceous deposits in Bahia State, which have been underexplored since their initial discoveries.
Skeletal remains of sauropod dinosaurs have been known from Australia for over 100 years. Unfortunately, the classification of the majority of these specimens to species level has historically been impeded by their incompleteness. This has begun to change in the last 15 years, primarily through the discovery and description of several partial skeletons from the Cenomanian-lower Turonian (lower Upper Cretaceous) Winton Formation in central Queensland, with four species erected to date: Australotitan cooperensis, Diamantinasaurus matildae, Savannasaurus elliottorum, and Wintonotitan wattsi. The first three of these appear to form a clade (Diamantinasauria) of early diverging titanosaurs (or close relatives of titanosaurs), whereas Wintonotitan wattsi is typically recovered as a distantly related non-titanosaurian somphospondylan. Through the use of 3D scanning, we digitised numerous specimens of Winton Formation sauropods, facilitating enhanced comparison between type and referred specimens, and heretofore undescribed specimens. We present new anatomical information on the holotype specimen of Diamantinasaurus matildae, and describe new remains pertaining to twelve sauropod individuals. Firsthand observations and digital analysis enabled previously proposed autapomorphic features of all four named Winton Formation sauropod species to be identified in the newly described specimens, with some specimens exhibiting putative autapomorphies of more than one species, prompting a reassessment of their taxonomic validity. Supported by a specimen-level phylogenetic analysis, we suggest that Australotitan cooperensis is probably a junior synonym of Diamantinasaurus matildae, but conservatively regard it herein as an indeterminate diamantinasaurian, meaning that the Winton Formation sauropod fauna now comprises three (rather than four) valid diamantinasaurian species: Diamantinasaurus matildae, Savannasaurus elliottorum, and Wintonotitan wattsi, with the latter robustly supported as a member of the clade for the first time. We refer some of the newly described specimens to these three species and provide revised diagnoses, with some previously proposed autapomorphies now regarded as diamantinasaurian synapomorphies. Our newly presented anatomical data and critical reappraisal of the Winton Formation sauropods facilitates a more comprehensive understanding of the mid-Cretaceous sauropod palaeobiota of central Queensland.
The Upper Cretaceous fossil vertebrate fauna of the Bajo de la Carpa Formation (Santonian), derived from several different locations in the Neuquén Basin, is relatively abundant and diverse, comprising mainly small to medium-sized reptiles, birds and fishes. The Cerro Overo – La Invernada locality (CO – LI), in the north of the basin, records a similar faunal component for that age, but stands out for its relatively greater abundance and diversity of titanosaur sauropods. The study of the materials presented here allows us to establish the presence of specimens of sauropods other than Overosaurus, the only titanosaur recorded so far in the area, the coexistence of small–medium sized forms with larger forms, which in turn represent some forms with more basal characteristics and others with more derived features. The abundance of the record of sauropods in CO – LI shows both morphological and evolutionary variations, so the discovery of more complete specimens will allow paleofaunistic, paleobiological, and paleoecological studies to be carried out. This will provide a better understanding of the role of titanosaurian sauropods in Late Cretaceous ecosystems.
The up to 200 m thick Upper Cretaceous deposits of Uruguay includes from base to top the Guichón, Mercedes, and Asencio formations, plus the lateral correlate of the latter, the Queguay Formation. In 2006, the most complete sauropod from the country
was excavated from the Guichón Formation near Araújo, Paysandú Department. Augmented by new specimens reported here, the material includes sixty caudal vertebrae (all strongly procoelous, except for the biconvex first one), a partial coracoid, long bone fragments (proximal and distal portions of tibia, proximal portion of fibula), two astragali, and six metatarsals, as well as associated eggshell fragments. The Uruguayan titanosaur shows a unique combination of characters (biconvex first caudal centrum, pneumatic foramina in the anteriormost caudal centra, dorsal tuberosities on the transverse processes of the anterior caudal vertebrae, well developed fibular knob, pyramidal astragalus), as well as a potential autapomorphy – middle caudal centra condyles with hexagonal contour – allowing the proposition of new genus and species, Udelartitan celeste. Phylogenetic analyses were for the first time performed to assess the relations of that taxon, which was recovered either as a saltasaurine saltasaurid or a non-saltasaurid saltasauroid. Further, one of the analyses show Udelartitan celeste nested within a clade including Late Cretaceous titanosaurs with a biconvex first caudal vertebra, such as Alamosaurus sanjuanensis, Baurutitan britoi, and Pellegrinisaurus powelli. This contribution demonstrates that at least two titanosaur lineages were present in the Late Cretaceous of Uruguay: Saltasauroidea and Aeolosaurini, the latter recently recognized in the stratigraphically younger Asencio Formation.
The Kem Kem Group of Southeastern Morocco, North Africa, is well known for theropod remains, especially
isolated teeth. Here, a collection of isolated theropod teeth is assessed for diversity using a combination of linear discriminant,
phylogenetic, and machine learning analyses for the first time. The results confirm earlier studies on Kem Kem theropod
diversity, with teeth referred to Abelisauridae, Spinosaurinae, and Carcharodontosauridae. A single tooth is ascribed to a
non-abelisauroid ceratosaur or a megaraptoran and may represent the enigmatic averostran Deltadromeus. Spinosaurine
teeth are clearly differentiated by all three methodologies, whereas abelisaurid and carcharodontosaurid teeth could only
be distinguished by the machine learning and phylogenetic analyses. This study shows that a combination of independent
methods is most effective at providing strong evidence on theropod dental diversity in a particular assemblage, and that
cladistic and machine learning analyses are the most reliable approaches to identify isolated dinosaur teeth. The
methodology used here is likely to yield results in other dinosaur assemblages where isolated teeth are more abundant
than body fossils.
The Portezuelo Formation preserves an outstanding record of the upper Turonian - lower Coniacian of Gondwana. Despite the discovery of a significant amount of sauropod fossil material from the Formation, only two species have been formally described to date: Malarguesaurus florenciae and Futalognkosaurus dukei . Here we present new sauropod material mostly composed of non-articulated caudal vertebrae that belong to at least two different titanosauriforms on the basis of following features: anterior caudal vertebrae with procoelous-opistoplatyan articulations, transverse processes that reach the posterior articular face of the centrum and neural spines with a lateromedial width of ~ 50% of its anteroposterior length; anterior and middle caudal vertebra with the neural arch restricted to the anterior half of the centrum; middle caudal centrum with circular cross-section. Phylogenetic analysis recovers the new material in close relation to Malarguesaurus within a monophyletic clade sister to Somphospondily. This clade shares large pedicel height with a vertical anterior border on the middle caudal vertebrae, a vertical orientation of the neural spines on the distalmost middle caudal vertebrae and proximalmost posterior caudal vertebrae, and subequal relative lengths of the proximal ulnar condylar processes. The specimens presented here are distinct not only from Malarguesaurus and Futalognkosaurus , but also from other indeterminate titanosaur remains from the same formation. Whilst we err on the side of caution in not naming new taxa here, the two specimens significantly expand what we know about sauropods in the Turonian-Coniacian ecosystems of Patagonia, which will continue to do so as more material is discovered.
Unsere allgemeine Vorstellung urzeitlicher Tiere unterliegt einem fortwährenden Wandel. Daher unterscheidet sich unser gegenwärtiges Bild der Urzeit von jenem, welches wir noch vor wenigen Jahrzehnten hatten. Die Sonderausstellung der POLLICHIA-Museen „Saurier – Die Erfindung der Urzeit“ beleuchtet diese wiederholten Neuerfindungen des geläufigen Urzeitbildes in Wissenschaft, Kunst und Popkultur innerhalb der letzten 200 Jahre exemplarisch an fünf ausgewählten Beispielen fossiler Saurier - den Rückensegelechsen Dimetrodon und Edaphosaurus, dem Handtier Chirotherium, dem Leguanzahn Iguanodon, den großen Raubsauriern Megalosaurus, Tyrannosaurus und Co. und den riesenhaften Sauropoden wie Brontosaurus, Diplodocus und Brachiosaurus. Die Ausstellung war 2022–2023 im Urweltmuseum GEOSKOP auf Burg Lichtenberg (Pfalz) und 2023–2024 im Pfalzmuseum für Naturkunde in Bad Dürkheim zu sehen. Die vorliegende, siebenteilige Serie beleuchtet in Einzelbeiträgen die darin vorgestellten Beispiele genauer.
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Our general perception of prehistoric animals is subject to constant change. This is why our current image of prehistoric times differs from the one we had just a few decades ago. The POLLICHIA Museums bilingual special exhibition "Saurians – The Invention of Prehistory" sheds light on these repeated reinventions of the common image of prehistory in science, art and pop culture over the last 200 years using five selected examples of fossil dinosaurs - the sail-back lizards Dimetrodon and Edaphosaurus, the hand-beast Chirotherium, the iguana tooth Iguanodon, the large predatory dinosaurs Megalosaurus, Tyrannosaurus and Co. and the giant sauropods such as Brontosaurus, Diplodocus and Brachiosaurus. The exhibition was on display at the Urweltmuseum GEOSKOP at Lichtenberg Castle (Palatinate) from 2022–2023 and at the Pfalzmuseum für Naturkunde in Bad Dürkheim from 2023–2024. This seven-part German-language series takes a closer look at the examples presented in individual articles.
fragmentary centrum of a dorsal vertebra and a manual ungual phalanx of eusauropod
dinosaurs from the Upper Barremian – Lower Aptian of Balve in western Germany
are described. The dorsal centrum shares potential synapomorphies with the enigmatic
genus Ornithopsis and can probably be referred to a titanosauriform. The Balve record
is of significance as it represents the only known direct evidence of this clade from an
upland environment in Europe, which is assumed to have reached palaeoelevations of
several hundred meters above sea level. Taphonomic signatures at some of the material
from this site indicate prolonged surface exposure plus various stages of wear caused by
water transport. The remains were finally deposited in sediment traps within a karst cave
or fissure system.
The fossil record suggests a retreat or shift of sauropod habitat range from coastal
plains and lowlands to hinter- and uplands during the Early Cretaceous in northwest
Europe. It is hypothesized that this was linked to the faunal replacement of low- and
mid-level browsing sauropods (e.g. diplodocoideans) by iguanodontian ornithopods
near the Jurassic-Cretaceous boundary in this region. High-browsing titanosauriform
sauropods had small overlap in the trophic niche with the ornithopods, facilitating a
sympatric coexistence of both groups. However, their range was dependent on highcanopy
vegetation that was probably more abundant in uplands. The previously observed
“mid-Cretaceous bottleneck” in sauropod diversity may therefore be a result of partial
extinction and/or a sampling bias, as the preservation of upland faunas are very exceptional.
However, it is be cautioned to interpolate these regional observations to global
sauropod diversity patterns.
Caenagnathidae is a clade of derived, Late Cretaceous oviraptorosaurian theropods from Asia and North America. Because their remains are rare and often fragmentary, caenagnathid diversity is poorly understood. Anzu wyliei is the only caenagnathid species currently described from the late Maastrichtian Hell Creek Formation of the USA and is also among the largest and most completely preserved North American caenagnathids. Smaller, less complete caenagnathid material has long been known from the Hell Creek Formation, but it is unclear whether these are juvenile representatives of Anzu or if they represent distinct, unnamed taxa. Here, we describe a relatively small caenagnathid hindlimb from the Hell Creek Formation, and conduct osteohistological analysis to assess its maturity. Histological data and morphological differences from Anzu wyliei and other caenagnathids allow us to conclude that this specimen represents a new species of caenagnathid from the Hell Creek Formation, with a smaller adult body size than Anzu. This new taxon is also distinct from other small caenagnathid material previously described from the area, potentially indicating the coexistence of three distinct caenagnathid species in the Hell Creek Formation. These results show that caenagnathid diversity in the Hell Creek ecosystem has been underestimated.
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.
Cretaceous (non-avian) theropod dinosaurs from Australia are poorly understood, primarily because almost all specimens described thus far comprise isolated postcranial elements. In Australia, only three non-dental cranial elements pertaining to Theropoda have been reported: the left and right dentaries of Australovenator wintonensis from the Winton Formation (Cenomanian–lowermost Turonian) of Queensland, and an isolated surangular from the Eumeralla Formation (lower Albian) of Victoria. Herein, we report the first evidence of non-mandibular cranial material of a non-avian theropod from Australia: a left frontal and fused parietal fragment from the Lower Cretaceous (lower Aptian) upper Strzelecki Group of Victoria. The specimen shares several synapomorphies with the frontals assigned to Megaraptoridae, including an anteroposteriorly elongate postorbital articulation and a truncated nasal articular surface. Accordingly, we regard this frontal as Megaraptoridae gen. et sp. indet. We performed both parsimony-based and Bayesian-based phylogenetic analyses to support our assignment, and both analyses support a placement within Megaraptoridae. However, this specimen appears to possess plesiomorphic characters relative to other megaraptorid frontals, lacking dorsoventrally high walls of bone that emarginate the nasal and prefrontal articular surfaces. The plesiomorphies of this specimen have implications for the evolution of the megaraptoran skull roof, suggesting the acquisition of specialised adaptations for longirostry over time. This specimen improves the limited record of Cretaceous Australian theropod cranial remains, and provides limited support for the hypothesis that Megaraptoridae might have originated in Australia.
Several paleontological field expeditions of Danish-US team took place in the Jameson Land Basin, in East Greenland. Their objective was to recover vertebrate fossils for understanding the evolution of the vertebrate fauna of the region and its dynamics with the surrounding through geological times. In the Triassic, the basin was located at 41° N in the northern rim of Pangea and bordered in the North by the Boreal Sea. During Late Triassic, the region was an ephemeral to perennial lake systems in dry steppe-like climate, crossed by rivers. This work focus on the microvertebrate remains recovered by expeditions from 1991 to 2016. The specimens have been photographed and listed in a catalogue. 867 specimens out of 993 could be identified. The main groups of Vertebrate are all present (Chondrichthyes, Actinopterygii, Amphibia, Reptilia, Mammalia) with new taxa never described nor reported in Greenland, such as Lissodus, Parvodus, Rhomphaiodon, Gyrolepis, Nothosauridae and the first batrachian ilium found in the region. The revision of two sphenodontians jaws fragment as Clevosauridae, with in association of the previously mentioned taxa that are highly documented in Europe and Asia, confirms a relationship between faunas of Greenland and Eurasia during the Late Triassic.
Many sauropod dinosaurs exhibit extensive postcranial skeletal pneumaticity that may have facilitated the
evolution of extreme body sizes. Among titanosauriforms, complex, irregularly branching camellate chambers are found
throughout the presacral vertebral column, often invading the ribs and ilium as well. To explore the function of these
camellae, including reduction in bone volume, pneumaticity was examined in a titanosaur sauropod from the Upper
Cretaceous Black Peaks Formation of Big Bend National Park, Texas, that includes pneumatic dorsal ribs and ilia. Using
natural breaks to non-destructively observe the internal structure, patterns of camellate pneumaticity are described for the
dorsal vertebrae, ribs, and ilium. The space occupied by camellae is quantified as the airspace proportion, which is
reported here in a sauropod ilium for the first time. Airspace proportions exceed 70% in parts of the dorsal vertebrae and
ilium, with lower values near the cotyles of the vertebral centra and the acetabulum. Values in the ribs decrease distally.
These values are not appreciably different from those of sauropods with simpler camerate pneumaticity. If camellae did
not offer greater weight reduction than camerae, they may have enhanced structural strength, as the chambers appear to
align with stress in the vertebral centra and ilium. Apneumatic trabecular bone around the acetabulum, preacetabular
process, and postzygapophyses, however, may indicate stresses too great for camellate bone to bear, although an
ontogenetic influence cannot be ruled out.
In 2020, the Australasian palaeontological association Australasian Palaeontologists (AAP) joined the Australian government-supported Australian National Species List (auNSL) initiative to compile the first Australian Fossil National Species List (auFNSL) for the region. The goal is to assemble comprehensive systematic data on all vertebrate, invertebrate and plant fossil taxa described to date, and to present the information both within a continuously updated open-access online framework, and as a series of primary reference articles in AAP’s flagship journal Alcheringa. This paper spearheads these auFNSL Alcheringa publications with an annotated checklist of Australian Mesozoic tetrapods. Complete synonymy, type material, source locality, geological age and bibliographical information are provided for 111 species formally named as of 2022. In addition, chronostratigraphically arranged inventories of all documented Australian Mesozoic tetrapod fossil occurrences are presented with illustrations of significant, exceptionally preserved and/or diagnostic specimens. The most diverse order-level clades include temnospondyl amphibians (34 species), saurischian (13 species) and ornithischian (12 species) dinosaurs (excluding ichnotaxa), and plesiosaurian marine reptiles (11 species). However, numerous other groups collectively span the earliest Triassic (earliest Induan) to Late Cretaceous (late Maastrichtian) and incorporate antecedents of modern Australian lineages, such as chelonioid and chelid turtles and monotreme mammals. Although scarce in comparison to records from other continents, Australia’s Mesozoic tetrapod assemblages are globally important because they constitute higher-palaeolatitude faunas that evince terrestrial and marine ecosystem evolution near the ancient South Pole. The pace of research on these assemblages has also accelerated substantially over the last 20 years, and serves to promote fossil geoheritage as an asset for scientific, cultural and economic development. The auFNSL augments the accessibility and utility of these palaeontological resources and provides a foundation for ongoing exploration into Australia’s unique natural history.
Linkages between hatchling and adult sauropods concerning morphological and ontogenetic growth remain enigmatic, which is even more tenuous in early sauropods. However, discoveries from Southeast Asia could provide significant insights into these questions of developmental history with the recent discovery of a partial juvenile vertebral series from an early sauropod from the early Middle Jurassic Nam Phong Formation, Chaiyaphum province, northeastern Thailand. Here we present the anatomical description of preserved portions of the axial skeleton, including cervical and dorsal vertebrae. Our study demonstrates the presence of 1) incipient laminae and fossae on the centrum; 2) unfused neural arch (cervical and dorsal); and 3) well-marked vertebral lamination system, all of which are osteological hallmarks of an immature growth phase. Particularly, we note that in this hatchling-juvenile specimen, the vertebral lamination complex resembles an adult early sauropod's form, along with no true pleurocoel in the vertebral arches. The co-occurrence of these two characters would strongly indicate a non-eusauropod sauropod affinity. With the presence of the lamination pattern, and the temporal placement of the specimen in the early Middle Jurassic, our material mostly resembles the Tazoudasaurus, so we assign the material to the Vulcanodontidae. Further analysis of this hatchling-juvenile specimen will provide crucial insights into the ontogenetic developmental history and musculoskeletal function, successfully filling a current knowledge gap within early sauropods evolutionary studies.
The Indian Mesozoic dinosaur record is famous for documenting significant aspects of dinosaur evolution during the Triassic, Jurassic and Cretaceous periods. The Cenomanian–Turonian Nimar Sandstone, Lower Narmada valley, has produced fragmentary skeletal remains of Sauropoda indet. The Maastrichtian Lameta
Formation has yielded at least 5 valid sauropod taxa and indeterminate titanosaurid remains, and at least 11 named (but likely oversplit) theropod taxa, i.e., 3 smaller-bodied species and 8 medium-to-large sized theropods. Apart from skeletal remains, Infra- and Intertrappean beds of peninsular India have yielded more
than 10,000 dinosaur eggs belonging to 5 oofamilies and 15 oospecies. Most of the Indian ootaxa show distinct affinities with the Late Cretaceous ootaxa of four other continental areas – Spain, France, Argentina and Morocco. The presence of the two dominant oofamilies, Fusioolithidae and Megaloolithidae, in the Infra- and
Intertrappean localities of peninsular India and three different continents (South America, Europe and Africa) further shows an ancient Gondwanan affinity and basic terrestrial association among these three landmasses.
Based on the phylogenetic analysis of skeletal material, the most plausible pathway of dinosaur dispersal between India and Madagascar took place during the Late Cretaceous. The other conceivable dispersal pathway for the small animals was between India and Asia by means of the Kohistan Dras Volcanic Arc or a northeast
pathway through Somalia, while the very large vertebrates, like theropod dinosaurs, may have emerged as a component of a ‘Pan Gondwanan’ model.
Key words: Cenomanian–Turonian; Cretaceous; Dinosaurs; India; Paleobiogeography.
Previous and new fossils of sauropods are reported from the Papo-Seco Formation (lower Barremian, Lower Cretaceous) at Cabo Espichel, south of Lisbon, Portugal. The fossils were collected from the Boca do Chapim and Praia do Areia do Mastro sites. The sauropods and other vertebrate fossil remains from the Papo-Seco Formation occur in marls, sandstones and some conglomerates in a sedimentary succession interpreted as deposited in lagoonal and estuarine environments, under a tropical climate. The study of the available specimens, including teeth and postcranial remains, suggests the occurrence of Titanosauriform sauropods.
Dinosaur fossils from the latest Cretaceous (Campanian–Maastrichtian) of Africa and the Arabian Peninsula are rare. Most discoveries to date have consisted of limited fossils that have precluded detailed phylogenetic and paleobiogeographic interpretations. Fortunately, recent discoveries such as the informative Egyptian titanosaurian sauropod dinosaur Mansourasaurus shahinae are beginning to address these long-standing issues. Here we describe an associated partial postcranial skeleton of a new titanosaurian taxon from the Upper Cretaceous (Campanian) Quseir Formation of the Kharga Oasis, Western Desert of Egypt. Consisting of five dorsal vertebrae and 12 appendicular elements, Igai semkhu gen. et sp. nov. constitutes one of the most informative dinosaurs yet recovered from the latest Cretaceous of Afro-Arabia. The relatively gracile limb bones and differences in the coracoid and metatarsal I preclude referral of the new specimen to Mansourasaurus. Both model-based Bayesian tip-dating and parsimony-based phylogenetic analyses support the affinities of Igai semkhu with other Late Cretaceous Afro-Eurasian titanosaurs (e.g., Mansourasaurus, Lirainosaurus astibiae, Opisthocoelicaudia skarzynskii), a conclusion supported by posterior dorsal vertebrae that lack a postzygodiapophyseal lamina, for example. Igai semkhu strengthens the hypothesis that northern Africa and Eurasia shared closely related terrestrial tetrapod faunas at the end of the Cretaceous and further differentiates this fauna from penecontemporaneous assemblages elsewhere in Africa, such as the Galula Formation in Tanzania, that exhibit more traditional Gondwanan assemblages. At present, the specific paleobiogeographic signal appears to vary between different dinosaur groups, suggesting that Afro-Arabian Cretaceous biotas may have experienced evolutionary and paleobiogeographic histories that were more complex than previously appreciated.
An exceptional articulated skeleton of a new basal neornithischian dinosaur, Minimocursor phunoiensis gen. et sp. nov., was discovered in the Late Jurassic Phu Kradung Formation at the Phu Noi locality, Kalasin Province, Thailand, a highly productive non-marine fossil vertebrate locality of the Khorat Plateau. It is one of the best-preserved dinosaurs ever found in Southeast Asia. Minimocursor phunoiensis gen. et sp. nov. shows a combination of both plesiomorphic and apomorphic characters resembling those of Late Jurassic to Early Cretaceous small-bodied ornithischians from China: a low subtriangular boss is projected laterally on the surface of the jugal, the brevis shelf of the ilium is visible in lateral view along its entire length, a distinct supraacetabular flange is present on the pubic peduncle of the ilium, the prepubis tip extends beyond the distal end of the preacetabular process of the ilium, and the manus digit formula is ?-3-4-3-2. The phylogenetic analysis shows that this
dinosaur is among the most basal neornithischians. This study provides a better understanding of the early evolution and taxonomic diversity of ornithischians in Southeast Asia.
Phu Kao-Phu Phan Kham Mountain ranges, situated on the border of Nong Bua Lamphu, Udon Thani, and Khon Kaen provinces,
northeastern Thailand, bear several localities that yield dinosaurs and other vertebrate faunas in the Lower Cretaceous. However, this area has received relatively little attention from the scientific community and the public. Here we review and report new dinosaur materials recovered from this region, some found decades ago, others discovered recently. We identify and discuss their taxonomy and paleobiodiversity. In the Barremian Sao Khua Formation, theropod dinosaurs were represented by spinosaurids, an early branching megaraptoran, a large indeterminate theropod, and small indeterminate theropods. Sauropods were represented by an indeterminate sauropod, a neosauropod, and titanosauriforms, including probable brachiosaurid and non-titanosaur somphospondylans. Other vertebrate groups, including crocodilians, turtles, fishes, and sharks, indicate a similar composition to other Sao Khua Formation communities in northeastern Thailand. The Sao Khua vertebrate assemblage exhibits the taxonomic diversity of dinosaur fauna and is currently
the best-documented assemblage in the Early Cretaceous of Southeast Asia. The Aptian–Albian Khok Kruat Formation, however, yields less diverse vertebrates. They are represented by freshwater sharks, crocodilians, and spinosaurid theropods. This may be due to sampling bias, environmental, or taphonomic conditions. This study provides the basis for future paleontological exploration and research of Mesozoic vertebrates in northeastern Thailand.
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.
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