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Ammonoids are an extinct group of cephalopods that lived from the Devonian until the end of the Cretaceous periods. In the Jurassic and Cretaceous periods, there were four suborders, Ancyloceratina, Perisphinctina, Lytoceratina, and Phylloceratina. Ancyloceratina formed a conch with detached whorls (open coiling) or non-planispiral coiling. The origin of Ancyloceratina remains unclear. In this study, we analyzed conch morphology in detail using specimens collected from southern India, Madagascar, and Japan. As a result, we found a common trend in conch morphology in early ontogeny of Ancyloceratina and Perisphinctina. We think that the similarity of conch morphology suggests a closer relationship between them, relative to Lytoceratina or Phylloceratina. Our findings are meaningful to consider the phylogenetic relationship and evolution of Jurassic–Cretaceous ammonoids. We analyzed the ontogenetic trajectories of conch morphology and septal spacing between successive chambers in Cretaceous ammonoids (suborders Perisphinctina and Ancyloceratina) collected from southern India, Madagascar, and Japan. All examined species, except for the family Collignoniceratidae, exhibited similar characteristics during early ontogeny. The common ontogenetic trajectories of septal spacing show a cycle comprising an increase and a subsequent decrease in septal spacing during early ontogeny. The conch diameters at the end of the cycle were estimated to be 1–4 mm. The conch shape (aperture height and whorl expansion rate) covariably changed at this conch diameter. Such covariable changes are commonly recognized in the suborders Perisphinctina and Ancyloceratina. The similarity in the ontogenetic trajectories of conch morphology implies a closer phylogenetic relationship between these suborders compared to Lytoceratina or Phylloceratina.

We report here the first neoselachian fossil fauna from Eocene nearshore marine deposits of the Mahajanga Basin, northwestern Madagascar. The fauna includes seven species of shark: Nebrius blankenhorni, Brachycarcharias koerti, Galeocerdo eaglesomei, two species of Carcharhinus (one of which is described as a new species), Physogaleus, Rhizoprionodon and Sphyrna. Three species of rays were also recovered: Pristis, Myliobatis and an undetermined dasyatid ray. This fauna represents the first Cenozoic neoselachian fossil record from the Eocene of Madagascar and broadens our understanding of their evolutionary and biogeographic history in the southern hemisphere during this time. Although the diversity of the genera and species of the fauna is very low, the age and similarity of genera to those in Congo, west Africa, Arabia, Asia, Europe, and North, Central, and South America suggests that these genera were broadly distributed and diverse within the shallow marine settings of the Tethyan and southern provinces during middle and late Eocene.

The extant anuran fauna of Madagascar is exceptionally rich and almost completely endemic. In recent years, many new species have been described and understanding of the history and relationships of this fauna has been greatly advanced by molecular studies, but very little is known of the fossil history of frogs on the island. Beelzebufo ampinga, the first named pre-Holocene frog from Madagascar, was described in 2008 on the basis of numerous disarticulated cranial and postcranial elements from the Upper Cretaceous (Maastrichtian) Maevarano Formation of Madagascar. These specimens documented the presence of a hyperossified taxon that differed strikingly from extant Malagasy frogs in its large size and heavy coarse cranial exostosis. Here we describe and analyse new, articulated, and more complete material of the skull, vertebral column, and hind limb, as well as additional isolated elements discovered since 2008. μCT scans allow a detailed understanding of both internal and external morphology and permit a more accurate reconstruction. The new material shows Beelzebufo to have been even more bizarre than originally interpreted, with large posterolateral skull flanges and sculptured vertebral spine tables. The apparent absence of a tympanic membrane, the strong cranial exostosis, and vertebral morphology suggest it may have burrowed during seasonally arid conditions, which have been interpreted for the Maevarano Formation from independent sedimentological and taphonomic evidence. New phylogenetic analyses, incorporating both morphological and molecular data, continue to place Beelzebufo with hyloid rather than ranoid frogs. Within Hyloidea, Beelzebufo still groups with the South American Ceratophryidae thus continuing to pose difficulties with both biogeographic interpretations and prior molecular divergence dates.

Madagascar is well known for producing exceptional fossils. However, the record for selachians remains relatively poorly known. Paleontological reconnaissance on the island of Nosy Makamby, off northwest Madagascar, has produced a previously undescribed assemblage of Miocene fossils. Based on isolated teeth, ten taxonomic groups are identified: Otodus, Carcharhinus, Galeocerdo, Rhizoprionodon, Sphyrna, Hemipristis, Squatina, Rostroraja, Himantura and Myliobatidae. Six are newly described from Madagascar for the Cenozoic (Galeocerdo, Rhizoprionodon, Sphyrna, Squatina, Rostroraja and Himantura). In association with these specimens, remains of both invertebrates (e.g., corals, gastropods, bivalves) and vertebrates (e.g., bony fish, turtles, crocodylians, and sirenian mammals) were also recovered. The sedimentary facies are highly suggestive of a near-shore/coastal plain depositional environment. This faunal association shares similarities to contemporaneous sites reported from North America and Europe and gives a glimpse into the paleoenvironment of Madagascar's Miocene, suggesting that this region was warm, tropical shallow-water marine.

Recent fieldwork in the Upper Cretaceous (Maastrichtian) Maevarano Formation, northwest Madagascar, has yielded important new skull material of the abelisaurid theropod, Majungasaurus crenatissimus. One of these specimens in particular-a virtually complete, disarticulated, and well preserved skull-greatly elucidates the craniofacial osteology of abelisaurids. Herein we describe the skull and lower jaws of this mid-sized theropod dinosaur. A number of features of the facial skeleton and cranium (as well as the postcranium) appear to result from increased levels of mineralization and ossification, which, at least in some instances, can be related directly to specific soft-tissue structures; examples include lacrimal-postorbital contact dorsal to the orbit, suborbital processes of the lacrimal and postorbital, presence of a mineralized interorbital septum, fused interdental plates, and mineralization of the overlying integument. Autapomorphic features include a highly derived nasal-greatly thickened and fused to its counterpart, with a large interior pneumatic chamber-and a median, 'dome'-like thickening of the frontals, which appear to have been variably pneumatized by a paranasal air sac. Majungasaurus also possesses a derived suite of skull morphologies, including: a rostrocaudally abbreviated, dorsoventrally deep, and transversely broad skull; an expanded occiput, likely associated with expanded cervical musculature; short-crowned dentition; and an enlarged external mandibular fenestra consistent with a moderate degree of intramandibular movement or accommodation. A number of characters, present on both the skull and postcranial skeleton, suggest a divergent mode of predation relative to other, non-abelisaurid theropods.

Titanosauria is a clade of sauropod dinosaurs that includes species ranging from the largest known terrestrial vertebrates to insular dwarfs no bigger than elephants. Although most sauropod dinosaurs exhibit highly vascularized fibrolamellar bone signaling rapid growth rates comparable to those of extant mammals, diminutive titanosaurs apparently exhibit histological traits consistent with reduced primary growth rates and/or truncated active growth to reach small adult body sizes. A better understanding of the evolution of titanosaur body size requires additional sampling of the 40 + known titanosaur species. The best-preserved and most complete titanosaur yet discovered is Rapetosaurus krausei from the Maastrichtian Maevarano Formation in Madagascar. Skeletal material from many individuals spanning a wide range of ontogeny, from neonates to very large body sizes, makes Rapetosaurus an ideal candidate for an analysis of growth. We analyzed Rapetosaurus histology using a growth series of 25 forelimb, hind limb, and girdle elements representing different ontogenetic stages, including samples from the largest Rapetosaurus known (femur length = 143 cm). Primary bone histology in Rapetosaurus is highly vascularized fibrolamellar tissue, such as is found in other sauropods and most sampled titanosaurs. Secondary remodeling begins early, as noted in other titanosaur taxa, and by mid-ontogeny is pervasive in most sampled elements. The largest known Rapetosaurus was still growing, whereas some small juveniles exhibit an unusual pattern of bone erosion and replacement in the context of peripheral lines of arrested growth that signal a temporary pause in bone apposition. We hypothesize that these signals may relate to the drought-stressed ecosystem inhabited by Rapetosaurus.

Simosuchus clarki is a small, pug-nosed notosuchian crocodyliform from the Late Cretaceous of Madagascar. Originally described on the basis of a single specimen including a remarkably complete and well-preserved skull and lower jaw, S. clarki is now known from five additional specimens that preserve portions of the craniofacial skeleton. Collectively, these six specimens represent all elements of the head skeleton except the stapedes, thus making the craniofacial skeleton of S. clarki one of the best and most completely preserved among all known basal mesoeucrocodylians. In this report, we provide a detailed description of the entire head skeleton of S. clarki, including a portion of the hyobranchial apparatus. The two most complete and well-preserved specimens differ substantially in several size and shape variables (e.g., projections, angulations, and areas of ornamentation), suggestive of sexual dimorphism. Assessment of both external and internal morphological features indicates a habitual head posture in which the preorbital portion of the dermal skull roof was tilted downward at an angle of ∼45°. Functional and comparative assessment of the feeding apparatus strongly indicates a predominantly if not exclusively herbivorous diet. Other features of the craniofacial skeleton of S. clarki are consistent with the interpretation developed from analysis of the postcranial skeleton of a terrestrial habitus, but the current working hypothesis of a burrowing lifestyle is not supported. The atypical appearance of the skull and lower jaw of S. clarki is underscored by the identification of at least 45 autapomorphic features, many of them related to the greatly foreshortened snout.

The bizarre crocodyliform Simosuchus clarki shares several derived cranial characteristics with basal notosuchian taxa. In the original phylogenetic analysis assessing placement of Simosuchus among other crocodyliforms, it was recovered as a basal notosuchian. Additional preparation of the holotype skull and postcranium, and discovery of additional specimens, provides new information on the suite of morphologies in this notosuchian. Morphological analysis of all available material of S. clarki yields 60 autapomorphies distributed across the skeleton. To provide an updated test of the phylogeny of Notosuchia and placement of Simosuchus within the clade, we added seven new characters and expanded taxon sampling to include recently described notosuchians. A phylogenetic analysis of 301 characters and 84 crocodyliforms supports the position of Simosuchus as sister to Libycosuchus, more derived than Araripesuchus and Uruguaysuchus, and basal to other ziphosuchian notosuchians. We did not recover an Anatosuchus + Simosuchus clade, nor a monophyletic Araripesuchus, but did recover a peirosaurid clade including Peirosaurus, Lomasuchus, Uberabasuchus, and Hamadasuchus (but not Stolokrosaurus). We also found weak support for inclusion of Anatosuchus, Araripesuchus, Peirosauridae, and Mahajangasuchidae within Notosuchia and therefore for the conclusion that all basal mesoeucrocodylians from Gondwana, with the exception of Stolokrosuchus, are notosuchians. The results of this analysis demonstrate that basal mesoeucrocodylian relationships are currently in a state of flux and the need for caution in naming higher-level taxa until a more stable consensus topology is achieved. Similarly, large gaps in the notosuchian record render inconclusive the biogeographic origins of Simosuchus and the clade it represents on Madagascar.

We describe three new fossil snakes on the basis of recently discovered vertebrae collected from the Upper Cretaceous (Maastrichtian) Maevarano Formation of Madagascar. One represents a new genus and species of madtsoiid, Adinophis fisaka, the third member of this family recognized from the Maevarano Formation. It exhibits dorsoventrally compressed centra and dorsally placed synapophyses. The second taxon is a new species of the nigerophiid genus Indophis, I. fanambinana, representing the second nigerophiid taxon known from the Maevarano Formation. It shares numerous features with the Indian nigerophiid I. sahnii, including small synapophyses positioned ventrolaterally on distinct synapophyseal processes and a unique cotylar shape in posterior trunk vertebrae. The discovery of I. fanambinana demonstrates a strong biogeographic link with penecontemporaneous snake faunas from India. A third new taxon is represented by a partial centrum that cannot be assessed thoroughly due to its incompleteness; this specimen is conservatively assigned to Serpentes incertae sedis, gen. et sp. indeterminate. It is distinct from other snakes known from the Late Cretaceous of Madagascar in possessing a strongly depressed condyle and relatively large lateral foramina. These new discoveries, together with previous descriptions of snakes from the Maevarano Formation, make the Maevarano snake fauna one of the most taxonomically diverse snake assemblages known from the Mesozoic and the most diverse in terms of body size range.

New material of the fossil crocodyliform taxon Mahajangasuchus insignis from the Upper Cretaceous Maevarano Formation is described. The holotype lacked cranial remains but the new material includes an almost complete skull as well as at least two additional partial skulls. These new specimens add important information and allow us to diagnose Mahajangasuchus insignis as a derived mesoeucrocodylian crocodyliform distinguished by the following combination of characters (autapomorphies indicated with an asterisk): broad platyrostral snout; laterally compressed and serrated teeth; dorsally arched mandible; prominent caudofemoralis flange on femur; surangular with prominent lateral expansion anterior to glenoid fossa; supraocciptial excludes the parietal from occipital margin; massive choanal septum*; anterior margins of choanal septum contact ventral lamina of pterygoid, enclosing internal choanae*; strongly arched jugal with depression below orbit*; three prominent ridges running longitudinally on dorsal surface of snout*; fused nasals.* The new specimen offers new information to explore the phylogenetic relationships of Mahajangasuchus insignis and bears important information for understanding the evolutionary history of the crocodyliform palate and the adaptive significance of the modern eusuchian-style palate. The phylogenetic analysis conducted results in the discovery of monophyly of the traditional Peirosauridae and a derived position for Mahajangasuchus and Stolokrosuchus as successive sister taxa to Neosuchia. Inclusion or exclusion of Trematochampsa taqueti, a fragmentary taxon from Africa, greatly affects the phylogenetic relations of Mahajangasuchus.