A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous

The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian theropod with unquestionable affinities to taxa from other Gondwanan landmasses, suggesting faunal interchange between eastern and western Gondwana during the Mid-Cretaceous. This evidence counters claims of Laurasian affinities for Early Cretaceous Australian dinosaur faunas, and for the existence of a geographical or climatic barrier isolating Australia from the other Gondwanan continents during this time. The temporal and geographical distribution of Megaraptor and the Eumeralla ulna is also inconsistent with traditional palaeogeographic models for the fragmentation of Gondwana, but compatible with several alternative models positing connections between South America and Antarctica in the Mid-Cretaceous.     

First titanosaur (Saurischia,Sauropoda) axial remains from the Uberaba Formation,Upper Cretaceous,Bauru Group,Brazil

The Adamantina and Marília formations are considered to be the richest vertebrate-bearing units in the Bauru Group, Upper Cretaceous, Brazil. In contrast, the fossil content from the Uberaba Formation, which only outcrops in Minas Gerais State, is scarce and poorly understood. In this essay the first taxonomically informative titanosaur remains unearthed from this unit are reported. They comprise anterior caudal vertebrae from two different individuals corresponding to a probably basal titanosaur (CPP-360) and a derived titanosaur (CPP-217). Although these remains can be clearly distinguished from other titanosaurs on the basis of their unique association of characteristics like the presence of mildly procoelous centra, lateral pits in the anterior caudal vertebrae, and prezygapophyses with a dorsal protuberance in anterior caudals in CPP-360 and the presence of strongly developed prespinal, spinopostzygapophyseal and centropostzygapophyseal laminae in CPP-217, more complete materials are needed to propose them new names.     

An Additional Baurusuchid from the Cretaceous of Brazil with Evidence of Interspecific Predation among Crocodyliformes

A new Baurusuchidae (Crocodyliformes, Mesoeucrocodylia), Aplestosuchus sordidus, is described based on a nearly complete skeleton collected in deposits of the Adamantina Formation (Bauru Group, Late Cretaceous) of Brazil. The nesting of the new taxon within Baurusuchidae can be ensured based on several exclusive skull features of this clade, such as the quadrate depression, medial approximation of the prefrontals, rostral extension of palatines (not reaching the level of the rostral margin of suborbital fenestrae), cylindrical dorsal portion of palatine bar, ridge on the ectopterygoid-jugal articulation, and supraoccipital with restricted thin transversal exposure in the caudalmost part of the skull roof. A newly proposed phylogeny of Baurusuchidae encompasses A. sordidus and recently described forms, suggesting its sixter-taxon relationship to Baurusuchus albertoi, within Baurusuchinae. Additionally, the remains of a sphagesaurid crocodyliform were preserved in the abdominal cavity of the new baurusuchid. Direct fossil evidence of behavioral interaction among fossil crocodyliforms is rare and mostly restricted to bite marks resulting from predation, as well as possible conspecific male-to-male aggression. This is the first time that a direct and unmistaken evidence of predation between different taxa of this group is recorded as fossils. This discovery confirms that baurusuchids were top predators of their time, with sphagesaurids occupying a lower trophic position, possibly with a more generalist diet.     

Burmese amber: evidence of Gondwanan origin and Cretaceous dispersion

Abstract

Burmese amber is an extremely important source of mid-Cretaceous plant and animal remains with over 870 species of organisms, ranging from protozoa to vertebrates, described from this source. The amber mines are located on the West Burma Block that according to geologists was originally part of Gondwana. The present study introduces some angiosperms and insects in Burmese amber whose closest extant relatives have a Gondwanan distribution and there is no previous evidence of a Laurasian distribution. Based on this evidence, it is proposed that organisms in Burmese amber represent a selection of tropical to subtropical life forms that inhabited the interconnected continents of Gondwana in the Early Cretaceous. Based on the fossil record of angiosperms and their diversity in Burmese amber, the West Burma Block could not have rafted from Gondwana to SE Asia before the Early Cretaceous.     

Increases in sampling support the southern Gondwanan hypothesis for the origin of dinosaurs

Dinosaurs were ubiquitous in terrestrial ecosystems through most of the Mesozoic and are still diversely represented in the modern fauna in the form of birds. Recent efforts to better understand the origins of the group have resulted in the discovery of many new species of early dinosaur and their closest relatives (dinosauromorphs). In addition, recent re‐examinations of early dinosaur phylogeny have highlighted uncertainties regarding the interrelationships of the main dinosaur lineages (Sauropodomorpha, Theropoda and Ornithischia), and questioned the traditional hypothesis that the group originated in South Gondwana and gradually dispersed over Pangaea. Here, we use an historical approach to examine the impact of new fossil discoveries and changing phylogenetic hypotheses on biogeographical scenarios for dinosaur origins over 20 years of research time, and analyse the results in the light of different fossil record sampling regimes. Our results consistently optimize South Gondwana as the ancestral area for Dinosauria, as well as for more inclusive clades including Dinosauromorpha, and show that this hypothesis is robust to increased taxonomic and geographic sampling and divergent phylogenetic results. Our results do not find any support for the recently proposed Laurasian origin of dinosaurs and suggest that a southern Gondwanan origin is by far the most plausible given our current knowledge of the diversity of early dinosaurs and non‐dinosaurian dinosauromorphs.     

The largest Cretaceous podocnemidoid turtle (Pleurodira) revealed by an isolated plate from the Bauru Basin,south-central Brazil

The Bauru Basin (south-central Brazil) fossils have largely contributed to understand the faunal composition of South American Cretaceous. Among those, several turtle specimens were retrieved from those deposits, all belonging to Podocnemidoidae, the single group known from the Basin. On the other hand, only incomplete shell elements indicate large turtles such as ‘Peirópolis A’. Another shell fragment, a large peripheral plate from the Marília Formation, is described here. Its lack of surface ornamentation, and deep sulci are generally typical for podocnemidoids. The plate exhibits a narrow knob slightly projected onto the pleuro-marginal sulcus, absent in any other Bauru Basin turtle. According to extant and fossil podocnemidoids measures, we estimated this individual reached 1 m of carapace length, exceeding in size all other taxa known from the Basin. This new report reveals a broader size variation among podocnemidoids from the Late Cretaceous of Bauru Basin and a morphological diversity previously unknown for the period, comparable to those of the Amazon Basin today, in which inhabits the largest extant podocnemidoid Podocnemis expansa. Furthermore, the occurrence of such large turtles implies the presence of perennial streams on the northeastern portion of the Bauru Basin during the Maastrichtian and a richer environment than previously thought.     

Scampering,trotting, walking tridactyl bipedal dinosaurs in southern Africa: ichnological account of a Lower Jurassic palaeosurface (upper Elliot Formation,Roma Valley) in Lesotho

In Gondwana, Early Jurassic dinosaur track sites are especially concentrated in Lesotho. Despite intensive investigations during the third quarter of the twentieth century, a limited number of vertebrate track sites of this country have been studied with rigorous ichnological and sedimentological methodology. Here, we present a previously mentioned, but undescribed track site in the upper Elliot Formation (Hettangian?) of Lesotho, located near Roma (at Lephoto dam). Two tridactyl ichnite morphologies, made by bipedal vertebrate trackmakers are recognised. The first can be identified as Grallator-like, an ichnotaxon common in the Lower Jurassic of both Laurasia and Gondwana that can be attributed to small and medium-size theropod dinosaurs. In contrast, the second ichnite type is reminiscent of Trisauropodiscus, which is a rare ichnotaxon that resembles tracks of small birds and is known with certainty in Lesotho from only a few places. We suggest that at our upper Elliot Formation study site, Trisauropodiscus was potentially made by a heterodontosaurid ornithischian dinosaur. Our work provides further evidence that the ichnological record of the Stormberg Group of southern Africa is in a unique position to shed light not only on Early Jurassic biostratigraphy and palaeoenvironments but also on the biodiversity and palaeobiology of early dinosaurs.     

On the phylogenetic relationships of Vincelestes neuquenianus

This short review paper compares the lower jaw and lower dentition of the small Mesozoic mammal Vincelestes neuquenianus with some other Laurasian and Gondwanan taxa. On this basis a set of 90 characters recognised by recent authors was assembled and used to construct a cladogram. The topology suggests that the early Cretaceous mammal from Patagonia, Vincelestes, is nested within a clade comprising ‘other Gondwanan mammals’, separated from Laurasian taxa. In general, because there is a lack of Mesozoic mammal skulls from Gondwana, meaning that the skull of Vincelestes can only be compared with cranial material from Laurasia, an incomplete understanding of relationships has resulted in earlier studies. The prototribosphenic condition of Vincelestes is supported by the cladistic analysis presented here and permits a number of interesting speculations because it is of later age than Jurassic tribosphenic mammals from Gondwana. It is proposed that the tribosphenic condition may have developed first amongst taxa on Pangea, before the separation of Laurasia and Gondwana.     

Thelodont Scales from the Lower Devonian Red Bay Group, Spitsbergen

Scales of nine thelodont taxa are described from the Red Bay Group of Spitsbergen, also characterized by its assemblage of other typical Early Devonian vertebrates. The four thelodont–bearing horizons of the lower Fraenkelryggen Formation yield typical Lochkovian thelodont assemblages, containing Boreania minima , Canonia grossi , Nikolivia depressa sp. nov., Nikolivia elongata , Nikolivia gutta and Turinia pagei . One horizon from the younger Ben Nevis Formation has a similar thelodont assemblage, except for two new taxa; Apalolepis angelica sp. nov. and Turinia barentsia sp. nov. The appearance of Turinia polita and the disappearance of Boreania minima is also characteristic for this assemblage. Comparison with similar faunas from the Northern Hemisphere supports this faunal change and allows further elaboration of Early Devonian thelodont biostratigraphy.     

A NEW TITANOSAUR FROM WESTERN SÃO PAULO STATE, UPPER CRETACEOUS BAURU GROUP, SOUTH-EAST BRAZIL

Abstract: Material from a new titanosaur from the Bauru Basin (Bauru Group), Brazil is described and compared with well‐known titanosaurs. Adamantisaurus mezzalirai gen. et sp. nov. is based on six articulated anterior caudal vertebrae and two haemapophyses collected from the Adamantina Formation, which is considered to be Campanian–Maastrichtian? in age. Adamantisaurus mezzalirai is characterized by the following combination of characteristics: anterior caudal vertebrae with straight or slightly backwardly‐projecting neural spines with strongly expanded distal ends, stout prespinal lamina, very wide pre‐ and postzygapophyseal articular facets, and concave postzygapophyseal articular facets on anterior caudal vertebrae. Although our cladistic analysis has produced equivocal results, Adamantisaurus mezzalirai shares with DGM ‘Series B’ (Peirópolis titanosaur) and Aeolosaurus the presence of postzygapophyses with concave articular facets, and shares with DGM ‘Series B’ the presence of laterally expanded neural spines and stout prespinal lamina. Additionally, A. mezzalirai shares with DGM ‘Series’ C (other titanosaur from Peirópolis) the presence of short neural spines.     

On a theropod scapula (Upper Cretaceous) from the Marília Formation, Bauru Group, Brazil

The record of theropod dinosaurs in Brazil is very scarce. One of the most promising lithostratigraphic units for those reptiles is the Bauru Group. The dinosaur remains found in this unit are mainly those of sauropods, while theropods are represented mostly by teeth. Here we describe a right scapula (housed at the Earth Science Museum of the Departamento Nacional de Produção Mineral/Rio de Janeiro) that is the first theropod scapula reported from the Cretaceous of Brazil and only the second osteological evidence of the Tetanurae from the Bauru Group. The specimen was recovered from the outskirts of Peirópolis, in Minas Gerais State. Comparisons with other theropod dinosaurs are limited, but the overall morphology of the new specimen indicates that it is neither a member of the Abelisauridae nor a member of the Avialae. It also differs from more basal members of the Theropoda, but its overall shape is consistent with several derived members of the Tetanurae, likely a non-avialan maniraptoran. Despite the lack of precision in its taxonomic position, the new specimen confirms the presence of non-avialan Maniraptora in the Bauru Group.     

Crocodyliform biogeography during the Cretaceous: evidence of Gondwanan vicariance from biogeographical analysis

Explanations of the distributions of terrestrial vertebrates during the Mesozoic are currently vigorously contested and debated in palaeobiogeography. Recent studies focusing on dinosaurs yield conflicting hypotheses. Dispersal, coupled with regional extinction or vicariance driven by continental break-up, have been cited as the main causal factors behind dinosaur distributions in the Mesozoic. To expand the scope of the debate and test for vicariance within another terrestrial group, I herein apply a cladistic biogeographical method to a large sample of Cretaceous crocodyliform taxa. A time-slicing methodology is employed and a refinement made to account for the divergence times of the analysed clades. The results provide statistically significant evidence that Gondwana fragmentation affected crocodyliform diversification during the Mid-Late Cretaceous. Detection of a vicariant pattern within crocodyliforms is important as it helps corroborate vicariance hypotheses in other fossil and extant groups as well as furthers the move towards more taxonomically diverse approaches to palaeobiogeographical research.     

Cranial biomechanics underpins high sauropod diversity in resource-poor environments

High megaherbivore species richness is documented in both fossil and contemporary ecosystems despite their high individual energy requirements. An extreme example of this is the Late Jurassic Morrison Formation, which was dominated by sauropod dinosaurs, the largest known terrestrial vertebrates. High sauropod diversity within the resource-limited Morrison is paradoxical, but might be explicable through sophisticated resource partitioning. This hypothesis was tested through finite-element analysis of the crania of the Morrison taxa Camarasaurus and Diplodocus. Results demonstrate divergent specialization, with Camarasaurus capable of exerting and accommodating greater bite forces than Diplodocus, permitting consumption of harder food items. Analysis of craniodental biomechanical characters taken from 35 sauropod taxa demonstrates a functional dichotomy in terms of bite force, cranial robustness and occlusal relationships yielding two polyphyletic functional ‘grades’. Morrison taxa are widely distributed within and between these two morphotypes, reflecting distinctive foraging specializations that formed a biomechanical basis for niche partitioning between them. This partitioning, coupled with benefits associated with large body size, would have enabled the high sauropod diversities present in the Morrison Formation. Further, this provides insight into the mechanisms responsible for supporting the high diversities of large megaherbivores observed in other Mesozoic and Cenozoic communities, particularly those occurring in resource-limited environments.     

Fossil vertebrate faunas of the British Rhaetian (latest Triassic)

Rhaetian fossil vertebrate faunas of Britain represent rich but biased samples of taxonomic diversity during uppermost Triassic time. Review of the Westbury Formation, Penarth Group, in particular, reveals a combination of marine, littoral, and terrestrial elements. Minimally, six species of shark are preserved along with a myriacanthid holocephalan, at least four actinopterygian taxa, a characteristic lungfish, ichthyosaurs, plesiosaurs, dinosaurs, and potentially the earliest representative of the Choristodera. Rare mammalian occurrences in the Westbury beds are also possible. Severnichthys gen. nov. is a large osteichthyan, probably a palaeonisciform chondrostean, which historically has been mistaken for a labyrinthodont amphibian. At least two additional actinopterygian species and a holocephalan are known from die Lilstock Formation, and a mammal or mammallike reptile is recorded from the uppermost Blue Anchor Formation. Analysis of element abundance in the disarticulated Westbury Formation assemblage indicates that many parts of some taxa are never preserved while other elements of the same form are common. Such preservational bias suggests that many species may be missing entirely from this long-studied but poorly understood taphocoenosis. Possibly contemporaneous cave faunas from nearby upland areas give a similarly biased picture of the terrestrial fauna during this time of widespread marine transgression.     

Crocodylomorph eggs and eggshells from the Adamantina Formation (Bauru Group), Upper Cretaceous of Brazil

Abstract: Compared with crocodylomorph body fossils, the record of fossil crocodiloid eggs is scarce and poorly understood, a gap partially attributed to their typically thin eggshell, which is not conducive to preservation. A remarkable new association of well‐preserved eggs and eggshells from the Adamantina Formation (Bauru Group, Upper Cretaceous) is described and compared to other known materials, while the significance of their unique oological features is discussed. These eggs constitute a new ootaxon, Bauruoolithus fragilis oogen. et oosp. nov., diagnosed by the following characteristics: elongate and elliptical egg with blunt ends; length‐to‐diameter ratio of 1:0.55; outer surface slightly undulating; shell thickness ranging from 0.15 to 0.25 mm; pore openings elliptical or teardrop‐shaped, ranging from 30 to 80 μm in diameter; and shell units wider than higher, with the interstices forming an obtuse triangle. Specimens of Bauruoolithus also show only slight signs of extrinsic degradation that, coupled with the evidence that some of them constitute hatched eggs, suggests that the egg‐laying taxon had a different pattern of egg incubation, in which the hatchling could break through the rather thin eggshell relatively easily and that the extrinsic degradation of the eggshell was not necessary. This contrasts with the pattern of incubation for all other known crocodylomorphs and crocodiloid eggs, where extrinsic degradation is a key component of the hatching process.     

Angiosperm pollen grains of San Just site (Escucha Formation) from the Albian of the Iberian Range (north-eastern Spain)

The most complete angiospermous palynological assemblage for the middle-earliest late Albian of north-eastern Spain is reported from the Middle Member of the Escucha Formation at the San Just site. Nine palynological samples yielded mainly monosulcates (Clavatipollenites, Dichastopollenites, Hammenia, Jusinghipollis, Liliacidites, Pennipollis including proposed new species P. escuchensis, Retimonocolpites, and Transitoripollis) and a few tricolpates (Phimopollenites, Rousea, Striatopollis, and Tricolpites). These assemblages, mainly composed of angiosperm pollen grains, suggest that significantly diversified flowering plants flourished both in brackish and freshwater swamp plain environments represented by the Escucha Formation in Albian times, although they were less diverse than angiosperms in the Late Cretaceous. The palynological assemblages share greatest similarities with those of other southern Laurasian localities, although there are some taxa more typical of palynofloras of northern Gondwana.     

Biogeographic analysis of Jurassic-Early Cretaceous wood assemblages from Gondwana

The terrestrial biogeography of Gondwana during Jurassic-Early Cretaceous times is poorly resolved, and the flora is usually considered to have been rather uniform. This is surprising given the size of Gondwana, which extended from the equator to the South Pole. Documenting Gondwanan terrestrial floristic provincialism in the Jurassic-Early Cretaceous times is important because it provides a historical biogeographic context in which to understand the tremendous evolutionary radiations that occurred during the mid-Cretaceous. In this paper, the distribution of Jurassic-Early Cretaceous fossil wood is analysed at generic level across the entire supercontinent. Specifically, wood assemblages are analyzed in terms of five climatic zones (summer wet, desert, winter wet, warm temperate, cool temperate) established on the basis of independent data. Results demonstrate that araucarian-like conifer wood was a dominant, cosmopolitan element, whereas other taxa showed a greater degree of provincialism. Indeed, several narrowly endemic morphogenera are recognizable from the data. Finally, comparisons with Laurasian wood assemblages indicate strong parallelism between the vegetation of both hemispheres.