Overview of the Late Triassic (Carnian) actinopterygian fauna from the Argana Basin (Morocco)

The continental outcrops of the Argana Basin (High Atlas of Morocco) have provided the richest tetrapod assemblage and the only known actinopterygian fauna of the Triassic of North Africa. Unlike the tetrapod remains, widely distributed throughout the basin, the actinopterygians are rare and come from a single locality. They are dated as the Late Triassic (Carnian) and have been attributed to six forms. Here, this ichthyofauna is reviewed for the first time since its original description. Two forms, endemic to the basin, are recognized as valid species and their generic attributions confirmed: the redfieldiiform Mauritanichthys rugosus, related to the genus Lasalichthys from the Late Triassic of North America, and the “perleidiform” Dipteronotus gibbosus, congeneric with Middle Triassic species of Europe. The other actinopterygian taxa are known by insufficiently preserved remains and need a complete material to be confidently identified. Two specimens previously referred to the redfieldiiform Ischnolepis are considered as Redfieldiiformes indet. and probably correspond to a new taxon. The three last forms, previously referred to the “perleidiforms” Procheirichthys and Perleidus, and to the redfieldiiform Atopocephala, are considered as Actinopterygii indet

Overview of the Late Triassic (Carnian) actinopterygian fauna from the Argana Basin (Morocco)

International audienceThe continental outcrops of the Argana Basin (High Atlas of Morocco) have provided therichest tetrapod assemblage and the only known actinopterygian fauna of the Triassic of North Africa.Unlike the tetrapod remains, widely distributed throughout the basin, the actinopterygians are rareand come from a single locality. They are dated as the Late Triassic (Carnian) and have been attributedto six forms. Here, this ichthyofauna is reviewed for the first time since its original description. Twoforms, endemic to the basin, are recognized as valid species and their generic attributions confirmed:the redfieldiiformMauritanichthys rugosus, related to the genusLasalichthysfrom the Late Triassicof North America, and the “perleidiform”Dipteronotus gibbosus, congeneric with Middle Triassicspecies of Europe. The other actinopterygian taxa are known by insufficiently preserved remainsand need a complete material to be confidently identified. Two specimens previously referred to theredfieldiiformIschnolepisare considered as Redfieldiiformes indet. and probably correspond to a newtaxon. The three last forms, previously referred to the “perleidiforms”ProcheirichthysandPerleidus,and to the redfieldiiformAtopocephala, are considered as Actinopterygii indet

Stelladens mysteriosus: A Strange New Mosasaurid (Squamata) from the Maastrichtian (Late Cretaceous) of Morocco

Mosasaurids, a clade of specialized marine squamates, saw a major adaptive radiation in the Late Cretaceous, evolving a wide range of body sizes, shapes, and specialized tooth morphologies. The most diverse known mosasaurid faunas come from the late Maastrichtian phosphates of Morocco. Here, we report an unusual new mosasaurid, Stelladens mysteriosus, based on a partial jaw and associated tooth crowns from lower Couche III phosphatic deposits at Sidi Chennane, Oulad Abdoun Basin, Morocco. Stelladens is characterized by short, triangular tooth crowns with a series of strong, elaborate, and serrated ridges on the lingual surface of the tooth, functioning as accessory carinae. Morphology of the teeth and associated jaw fragment suggest affinities with Mosasaurinae. No close analogues to the unique tooth morphology of Stelladens are known, either extant or extinct. It may have had an unusual and highly specialized diet, a specialized prey-capture strategy, or both. The diversity of mosasaurid teeth is much higher than that of plesiosaurs, ichthyosaurs, or extant marine mammals, and likely reflects both the ecological diversity of mosasaurids and complex developmental mechanisms responsible for tooth formation in mosasaurines. Mosasaurid diversity continued to increase up to the Cretaceous–Paleogene boundary.Research of XPS is financed by the Spanish Ministry of Science and Innovation (MCIN) and the European Regional Development Fund (FEDER) (research project PID2021-122612OB-I00), and by the Basque Country Gouvernment (research group IT1485-22). This study is carried out within the framework of the agreement between the universities of Bath and Cadi Ayyad

Xenodens calminechari gen. et sp. nov., a bizarre mosasaurid (Mosasauridae, Squamata) with shark-like cutting teeth from the upper Maastrichtian of Morocco, North Africa

The mosasaurids (Mosasauridae) were a group of lizards that became highly specialized for marine life in the mid-Cretaceous. By the end of the Cretaceous, they had undergone an adaptive radiation, and showed a wide range of body sizes, locomotor styles, and diets. Their ranks included piscivores, apex predators, and durophages. Here, we report a new taxon, Xenodens calminechari gen. et sp. nov., from the upper Maastrichtian phosphates of Morocco, with dental specializations unlike those of any known reptile. Teeth form a unique dental battery in which short, laterally compressed and hooked teeth formed a saw-like blade. Unique features of tooth structure and implantation suggest affinities with the durophagous Carinodens. The tooth arrangement seen in Xenodens not only expands known disparity of mosasaurids, but is unique among Squamata, or even Tetrapoda. The specialized dentition implies a previously unknown feeding strategy, likely involving a cutting motion used to carve pieces out of large prey, or in scavenging. This novel dental specialization adds to the already considerable disparity and functional diversity of the late Maastrichtian mosasaurids and marine reptiles. This provides further evidence for a diverse marine fauna just prior to the K-Pg extinction

The first duckbill dinosaur (Hadrosauridae: Lambeosaurinae) from Africa and the role of oceanic dispersal in dinosaur biogeography

The Late Cretaceous saw distinctly endemic dinosaur faunas evolve in the northern and southern hemispheres. The Laurasian continents of North America and Asia were dominated by hadrosaurid and ceratopsian ornithischians, with tyrannosaurs as apex predators. In Gondwanan communities, including Africa, South America, India and Madagascar, titanosaurian sauropods dominated as herbivores and abelisaurids as predators. These patterns are thought to be driven by the breakup of Pangaea and formation of seaways limiting dispersal. Here, we report a new lambeosaurine hadrosaurid, Ajnabia odysseus gen. et sp. nov., from the upper Maastrichtian of Morocco, North Africa, the first Gondwanan representative of a clade formerly thought to be restricted to Laurasia. The new animal shows features unique to Hadrosauridae and specifically Lambeosaurinae. Phylogenetic analysis recovers it within Arenysaurini, a clade of lambeosaurines previously known only in Europe. Biogeographic modelling shows that lambeosaurines dispersed from Asia to Europe, then to Africa. Given the existence of large, persistent seaways isolating Africa and Europe from other continents, and the absence of the extensive, bidirectional interchange characterizing land bridges, these patterns suggest dispersals across marine barriers, similar to those seen in Cenozoic mammals, reptiles, and amphibians. Dispersal across marine barriers also occurs in other hadrosaurid lineages and titanosaurian sauropods, suggesting oceanic dispersal played a key role in structuring Mesozoic terrestrial dinosaur faunas

Ancient DNA elucidates the lost world of western Indian Ocean giant tortoises and reveals a new extinct species from Madagascar

© 2023 The Authors. Published by the American Association for the Advancement of Science under a Creative Commons License. The published version can be accessed at the following link on the publisher’s website: https://www.science.org/doi/10.1126/sciadv.abq2574Before humans arrived, giant tortoises occurred on many western Indian Ocean islands. We combined ancient DNA, phylogenetic, ancestral range, and molecular clock analyses with radiocarbon and paleogeographic evidence to decipher their diversity and biogeography. Using a mitogenomic time tree, we propose that the ancestor of the extinct Mascarene tortoises spread from Africa in the Eocene to now-sunken islands northeast of Madagascar. From these islands, the Mascarenes were repeatedly colonized. Another out-of-Africa dispersal (latest Eocene/Oligocene) produced on Madagascar giant, large, and small tortoise species. Two giant and one large species disappeared c. 1000 to 600 years ago, the latter described here as new to science using nuclear and mitochondrial DNA. From Madagascar, the Granitic Seychelles were colonized (Early Pliocene) and from there, repeatedly Aldabra (Late Pleistocene). The Granitic Seychelles populations were eradicated and later reintroduced from Aldabra. Our results underline that integrating ancient DNA data into a multi-evidence framework substantially enhances the knowledge of the past diversity of island faunas.The work of C.K. and U.F. was supported by the Senckenberg Society for Nature Research (SGN), Germany. The work of E.G. and U.F. was partially supported by the Spanish Ministry of Science and Innovation through the project PID2019-105682RA-100/AEI/10.13039/501100011033. The work of V.D. was supported by the Alexander von Humboldt Foundation, Germany. F.I. was supported by the German Research Foundation (DFG, grant number IH 133/1-1).Published versio

Supplementary Figure 1

Supplementary FIGURE 1. Composite images of entire diaphyseal cross sections of right humerus MNHN.F ALM435, left femur MNHN.F ALM497 and right tibia MNHN.F ALM369. Abbreviations: A, anterior; D, dorsal; L, lateral; M, medial; P, posterior; V, ventral. Scale bar: 1 m

Data from: Bone histology of Azendohsaurus laaroussii. Implications for the evolution of thermometabolism in Archosauromorpha

This paper is aimed at constraining the phylogenetic frame of the acquisition of endothermy by Archosauromorpha. We analyzed the bone histology of Azendohsaurus laaroussii. Stylopodial and zeugopodial bones show three tissue types: (a) avascular lamellar zonal bone formed at low growth rates; (b) a scaffold of parallel fibered bone containing either small primary osteons or simple vascular canals; and (c) fibrolamellar bone formed at high growth rates. We used quantitative histology to infer the thermometabolic regime (endothermy versus ectothermy) of this taxon. We define endothermy as the presence of any mechanism of non-shivering thermogenesis that increases both body temperature and resting metabolic rate. Thus, estimating the resting metabolic rate of an extinct organism may be a good proxy to infer its thermometabolic regime (endothermy versus ectothermy). High resting metabolic rates have been shown to be primitive for the clade Prolacerta – Archosauriformes. Therefore, we inferred the resting metabolic rates of Azendohsaurus laaroussii, a sister group of this clade, and of 14 extinct related taxa, using Phylogenetic Eigenvector Maps. All the inferences obtained are included in the range of variation of resting metabolic rates measured in mammals and birds, so we can reasonably assume that all these taxa (including Azendohsaurus) were endotherms. A parsimony optimization of the presence of endothermy on a phylogenetic tree of tetrapods shows that this derived character state was acquired by the last common ancestor of the clade Azendohsaurus – Archosauriformes, and that there is a reversion in Crocodylia