Cretaceous Of Africa Research Articles

New record of aquatic snakes (Squamata, Palaeophiidae) from the Paleocene of South America

ABSTRACT The Paleocene deposits from the Cerrejón Formation (Colombia, South America) have provided abundant snake remains. All this material has been assigned to the giant snake Titanoboa cerrejonensis. Here, we describe six vertebrae from among the referred materials that do not correspond to Titanoboa. All six vertebrae are morphologically identical, of a similar size, and display a distinct morphology that differs from Titanoboa. This new and unnamed taxon is a large snake estimated to be around eight meters in total length. Anatomical comparisons show that these vertebrae possess certain features typical of the Palaeophiidae, a group of extinct snakes of uncertain relationships known almost exclusively from vertebrae. Among the Palaeophiidae, the new taxon resembles the more generalized forms assigned to the genus Palaeophis, but lacks the extreme aquatic adaptations that define forms assigned to the genus Pterosphenus. We regard the new taxon as an undetermined palaeophiine but do not assign it to Palaeophis as a number of features differ from that described genus. This new record expands the known diversity of aquatic snakes from the Paleogene of South America and provides a substantial new record for the paleogeographic distribution of the Palaeophiidae. The oldest records are from the Cretaceous of Africa, while Paleocene records are poorly known and restricted to Africa, North America, and Europe. The majority of vertebral forms assigned to Palaeophiidae are from the Eocene, principally from the Tethys region, with only one previous South American record coming from the Eocene of Ecuador.

A peirosaurid mandible from the Albian–Cenomanian (Lower Cretaceous) of Algeria and the taxonomic content of Hamadasuchus (Crocodylomorpha, Peirosauridae)

AbstractPeirosaurids form an extinct clade of terrestrial crocodylomorphs from the Cretaceous of Africa and South America. Here, we describe a new mandibular ramus attributable to Hamadasuchus cf. rebouli from the Albian–Cenomanian of La Gara Samani (Algeria). We propose an emended diagnosis for this taxon, originally described from a left dentary fragment from the Kem Kem Group of Morocco and discuss the assignment of the specimens currently referred to it. Using ontogenetic series of extant crocodylians, we show that several mandibular characters commonly used to differentiate between close taxa instead record intraspecific or ontogenetic variability. In contrast, reliable mandibular characters enable us to propose that the current taxonomic content of Hamadasuchus rebouli should be reduced to three specimens, pending future description of relatable cranial remains. Finally, we demonstrate the importance of mandibular characters in phylogenies, by recovering the new specimen from La Gara Samani as closely related to North African peirosaurids on the basis of a data matrix designed solely on mandibular characters.

A new pipid from the Cretaceous of Africa (In Becetèn, Niger) and early evolution of the Pipidae

Pipimorpha and its crown-group Pipidae possess one of the most extensive fossil records among anurans, known since the Early Cretaceous in both Laurasia and Gondwana. Pipimorph diversification may have been driven by the breakup of West Gondwana during the Cretaceous. Numerous fossils from South America have been unearthed in the last decade, documenting this event. Unfortunately, Cretaceous pipimorphs from Africa have been limited to a few well-preserved taxa from sub-Saharan Africa and the Arabian Peninsula, which hinders our comprehension of pipimorph diversification during this key period. The site of In Becetèn, in south-east Niger, is one of the few mid-Late Cretaceous (Coniacian–Santonian) sites from which a pipid, Pachycentrata taqueti, is known. Here, we describe and name a second pipid from the same locality. This taxon is known by a relatively complete braincase. Phylogenetic analyses confirm its position as a pipid, with pipinomorph affinities. This makes In Becetèn the oldest site with at least two pipids. Phylogenetic results are congruent with recent pipimorph relationships, with the presence of an endemic extinct clade in South America, Shelaniinae. The phylogenetic results also allow us to review the proposed definition for Pipimorpha and its subclades and propose new systematic definitions for them. Temporal calibration of the phylogenetic tree based on the fossil record suggests that pipimorphs diversified in a western Gondwana block and confirms that South America separated from Africa around the mid-Cretaceous. Between these two events, pipids diverged in Africa, giving rise to major extant clades. This study highlights the importance of Africa for early pipid diversification during the Cretaceous and of the opening of the Southern Atlantic Ocean for anuran dispersion and diversification. http://zoobank.org/urn:lsid:zoobank.org:pub:D40F9A91-D57C-4ED8-B80A-9CA5246599E3

New cranial remains of the broad-nosed crocodile Elosuchus (Pholidosauridae; Mesoeucocodrylia) and its palaeoecological implications

ABSTRACT Sometimes Natural History Museums unknowingly treasure singular specimens in their collections for decades. The re-discovery of such elements allows the description of previously unknown features of well-known taxa. Here, we describe a nearly complete left premaxilla attributed to the pholidosaurid Elosuchus. Specimen IPS3303 shows some remarkable differences with previously known premaxillae of Elosuchus, especially concerning the relative position of the fifth premaxillary tooth and the premaxilla-maxilla sutural surface morphology. Because of the scarcity of current data, it is difficult to evaluate the significance of such differences. The described element is about 40% larger than the largest premaxilla of Elosuchus known so far, suggesting that this taxon could achieve remarkable body size proportions. The preliminary analyses of the dentition and the neurovascular system of the premaxilla provide new insight into the palaeoecology of this riverine crocodylomorph from the Cretaceous of Africa.

A new pipid from the Cretaceous of Africa (In Becetén, Niger) and early evolution of the Pipidae

A new pipid from the Cretaceous of Africa (In Becetén, Niger) and early evolution of the Pipidae

Small, immature pterosaurs from the Cretaceous of Africa: implications for taphonomic bias and palaeocommunity structure in flying reptiles

Pterosaurs reached only modest sizes in the Triassic-Jurassic. By contrast, the Cretaceous saw a trend toward large to giant size (2 m to >6 m wingspans), and while small-medium (<1 m–2 m wingspans) sized forms are known from the Lower Cretaceous they are rare in the Upper Cretaceous. This pattern has been ascribed to the appearance of birds in the mid-Mesozoic, and their displacement of pterosaurs from niches previously occupied by small-medium sized forms. Here we show how new finds of small-very small pterosaurs (<1 m wingspans) from the mid-Cretaceous Kem Kem Group of Morocco point to several sampling biases of the data upon which these patterns are founded. Evidence for the size range of these pterosaurs strongly correlates with sample-size: as the sample increased (from <100 to >400 specimens) both very small and giant forms have been discovered. Histological analysis suggests that very small/small morphs are immature individuals rather than species in which adults were small-bodied. This new data shows that size distribution patterns based on all available specimens differ markedly from those based on a much more restricted sub-set of named taxa. Critically, this analysis reveals that pterosaur size ranges in the Cretaceous do not reflect a switch to large and giant size, but an extension of the size range from very small through to giant forms. Cretaceous niches previously occupied by small pterosaurs in the Triassic and Jurassic were increasingly occupied not by birds but by early ontogenetic stages of large and giant pterosaurs.

Large-sized theropod Spinosaurus: an important component of the carnivorous dinosaur fauna in southern continents during the Cretaceous

The Early Cretaceous of North Africa has Spinosaurinae dinosaur remains such as Spinosaurus recorded in Algeria (Guir Basin, Kem Kem beds), Egypt (Bahariya Formation), Morocco (Kem Kem beds), and Tunisia (Ain El Guettar Formation). Until now, three possible Spinosaurus species were identified: Spinosaurus aegyptiacus, Spinosaurus sp. and Spinosaurus “B”. The occurrence of this genus in the Albian-Cenomanian rocks of Africa suggests that the temporal and geographic distribution of these spinosaurines is the largest one among all genera and species of megapredators from the middle Cretaceous of Africa. The fossil record of Spinosaurus from the Albian to the Cenomanian shows a 20 million year persistence of this genus in Gondwanan ecosystems.

First report on Cretaceous vertebrates from the Algerian Kem Kem beds. A new procoelous salamander from the Cenomanian, with remarks on African Caudata

In northwestern Africa, the Kem Kem plateau is a major source of continental Cenomanian fossils. The plateau extends across the Algerian–Moroccan border but, unlike the intensely worked Moroccan part, the Algerian side of the Kem Kem beds has received less attention. However, recent field work in Algeria resulted in the recovery of a locality that yielded a promising vertebrate assemblage. Among the fossils is a trunk vertebra belonging to a salamander, a group whose remains are extremely rare in Africa. The vertebra is procoelous and it presents combination of characters that suggest it belongs to a new taxon of unknown affinities. Although the putative new taxon is represented by a single specimen that is too poorly preserved to be formally named, the discovery is important for showing that salamanders were more diversified than expected in the Cretaceous of Africa.

Reassessment of a fragmentary maxilla attributed to Carcharodontosauridae from Presidente Prudente Formation, Brazil

Carcharodontosauridae and Abelisauridae are two coexisting clades of theropod dinosaurs from the Cretaceous of Africa, South America and possibly Europe. The oldest and most recent carcharodontosaurid remains are from the Kimmeridgian-Tithonian of Africa and Turonian of South America, respectively. Recently, a fragmented maxilla bearing a single in-situ tooth (UFRJ-DG409-R) from the Maastrichtian of Brazil has been interpreted as belonging to a carcharodontosaurid. We here reassessed the phylogenetic distribution of these material using morphological, morphometric and phylogenetic analyses. If the morphology of the tooth is shared with carcharodontosaurids and abelisaurids, the morphometric analyses found the crown in the same morphospace as abelisaurids, and the phylogenetic analysis performed on a dentition-based datamatrix retrieved it among Abelisauridae. The maxilla also shares features with both groups, yet the horizontal striations on the paradental plates of UFRJ-DG409-R support abelisaurid affinities. Our data strongly suggest that these specimens belong to abelisaurid theropods, supporting the fact that carcharodontosaurids were likely extinct from Coniacian.

The ‘death roll’ of giant fossil crocodyliforms (Crocodylomorpha: Neosuchia): allometric and skull strength analysis

In the evolution of crocodylomorphs, there were at least three giant-dimension genera: Deinosuchus from late Cretaceous of North America, Sarcosuchus from middle Cretaceous of Africa and South America, and Purussaurus from Miocene of South America. It has been suggested that these predators could have fed on very large prey as dinosaurs and megamammals. The ‘death roll’ is a spinning manoeuver executed to subdue and dismember large prey; therefore, it has been previously suggested that giant cocrodylomorphs may have used this manoeuver. However, this manoeuver can generate torsional stresses in the skull. We propose a biomechanical model to estimate the capability of a crocodylomorphs for withstanding this torsional stresses. Our results show a good correlation between a ‘death roll’ capability indicator and the feeding categories related with the actual use of ‘death roll’ in 16 living species. Here, for the first time, we propose a biomechanical approach of the implications of ‘death roll’ in fossil crocodylomorphs. We suggest that Deinosuchus and Purussaurus were able to execute death roll over dinosaurs and large mammals, respectively, but Sarcosuchus probably was not. We also found some allometry effects and, finally, we discuss palaeobiological implications based on our results.

First report of mammal-like tracks from the Cretaceous of North Africa (Tunisia)

This paper describes Cretaceous mammal-like tracks from southern Tunisia. The tracks, referred to the Cenomanian Kerker Member of the Zebbag Formation, are the first mammal-like footprints reported from the Cretaceous of North Africa. The good preservation of the two tracks and their distinctive morphology support their attribution to a mammalian trackmaker, although the limited available data prevents attribution to a specific ichnotaxon. Morphologically, the Tunisian tracks resemble those of modern Mustelidae, however, based on mammalian faunas in the Cretaceous of Africa, they probably have affinity with members of Multituberculate family. Theropod dinosaur and bird tracks occur on the same track-bearing layer. The sediments are interpreted as an arid tidal flat environment, suggesting that African mammals might have shared their environment with a diverse fauna of larger animals.

New rebbachisaurid (Dinosauria: Sauropoda) material from the Wessex Formation (Barremian, Early Cretaceous), Isle of Wight, United Kingdom

Rebbachisauridae is a poorly understood clade of diplodocoid sauropod dinosaurs, currently known only from the Cretaceous of Africa, Europe and South America. European representatives are particularly rare and fragmentary. Here, we report an anterior caudal vertebra from the Barremian (Early Cretaceous) Wessex Formation of the Isle of Wight, off the southern coast of England. This specimen possesses several features known only in rebbachisaurids and shares two synapomorphies with the Afro-European taxa Demandasaurus darwini and Nigersaurus taqueti, both pertaining to the morphology of the neural spine. These features are the development of triangular lateral processes and the presence of an elliptical fossa on the lateral surface, bounded by the lateral lamina and postspinal rugosity. The Isle of Wight specimen also shares several features solely with Demandasaurus, indicating a close relationship with the Spanish taxon. These include the presence of a hyposphenal ridge, as well as an anteriorly excavated caudal rib that is restricted almost entirely to the neural arch. However, it differs from Demandasaurus in a number of ways, including the lack of excavation on the posterior surface of the caudal rib, the orientation of the neural spine, and the composition and morphology of the lateral lamina. In addition, the Isle of Wight vertebra possesses one potential autapomorphy: bifurcation of the elliptical fossa on the neural spine. However, because of the fragmentary nature of the material, a new name is not erected. Along with Demandasaurus and Histriasaurus boscarollii, this caudal vertebra indicates the presence of at least three European rebbachisaurid taxa and provides new anatomical information on this enigmatic clade of sauropod dinosaurs.

Dinosaur remains from the Lower Cretaceous of the Chubut Group, Argentina

Some fragmentary dinosaur remains from the uppermost Hauterivian–Barremian La Paloma Member of the Cerro Barcino Formation of northern Chubut, Argentina are described. Together with the fauna from the La Amarga Formation of Neuquén, Argentina, this material represent the oldest known Cretaceous dinosaur fauna from South America. It includes remains of a probable titanosaurian sauropod and an abelisaurian, probable abelisaurid, theropod. This is the oldest record of titanosaurs from South America and the oldest record of abelisaurids globally. The presence of both small-bodied noasaurids in the La Amarga Formation and medium-sized–large abelisaurids in the Cerro Barcino Formation, in the middle Lower Cretaceous of Argentina, indicates that abelisaurian diversification began well before the final fragmentation of Gondwana. Whereas this explains the wide distribution of abelisaurs in the Late Cretaceous, reasons other than vicariance must be invoked for their apparent absence in the ‘middle’ Cretaceous of Africa.

Mammal teeth from the Cretaceous of Africa.

We report here the discovery of two mammal teeth from the early Cretaceous of Cameroon. These, and some jaw fragments, all from Cameroon, are the only fossil evidence of mammalian evolution from Africa between late Jurassic and Paleocene, a span of at least 85 million years. A triangular upper tooth lacks the principal internal cusp of marsupials and placentals and is therefore of a similar evolutionary grade to most Jurassic and early Cretaceous therian mammals, but more primitive than the metatherian-eutherian grade. Early Cretaceous, or older, therian mammals are now known from all southern continents except Antarctica. The new find from Cameroon is consistent with the hypothesis that marsupials, the dominant living mammals of South America and Australia, were not present on any Gondwana continents until after the early Cretaceous separation of Africa by the opening of the South Atlantic.