Ontogenetic variation in the cranium of Mixosaurus cornalianus, with implications for the evolution of ichthyosaurian cranial development

Relatively complete ontogenetic series are comparatively rare in the vertebrate fossil record. This can create biases in our understanding of morphology and evolution, since immaturity can represent a source of unrecognized intraspecific variation in both skeletal anatomy and ecology. In the extinct marine reptile clade Ichthyopterygia, ontogenetic series were widely studied only in some Jurassic genera, while the ontogeny of the oldest and most basal members of the clade is very poorly understood. Here, we investigate cranial ontogeny in Mixosaurus cornalianus, from the Middle Triassic Besano Formation of the Swiss and Italian Alps. This small-bodied taxon is represented by a wealth of material from multiple size classes, including fetal material. This allows us to assess ontogenetic changes in cranial morphology, and identify stages in the ontogenetic trajectory where divergence with more derived ichthyosaurs has occurred. Early ontogenetic stages of Mixosaurus show developmental patterns that are reminiscent of the presumed ancestral (early diverging sauropsid) condition. This is prominently visible in the late fetal stage in both the basioccipital, which shows morphology akin to basal tubera, and in the postorbital, which has a triradiate head. The ontogenetic trajectory of at least some of the cranial elements of Mixosaurus is therefore likely still very akin to the ancestral condition, even though the adult cranium diverges from the standard diapsid morphology

Cranial anatomy of Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996 (Reptilia: Ichthyosauria) from the Middle Triassic Besano Formation of Monte San Giorgio, Italy/Switzerland. Taxonomic and palaeobiological implications

Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996 was described on the basis of a single fossil excavated near Besano (Italy) nearly three decades ago. Here, we re-examine its cranial osteology and assign five additional specimens to B. leptorhynchus, four of which were so far undescribed. All of the referred specimens were collected from the Middle Triassic outcrops of the Monte San Giorgio area (Italy/Switzerland) and are housed in various museum collections in Europe. The revised diagnosis of the taxon includes the following combination of cranial characters: extreme longirostry; an elongate frontal not participating in the supratemporal fenestra; a prominent `triangular process' of the quadrate; a caudoventral exposure of the postorbital on the skull roof; a prominent coronoid (preglenoid) process of the surangular; tiny conical teeth with coarsely-striated crown surfaces and deeply-grooved roots; mesial maxillary teeth set in sockets; distal maxillary teeth set in a short groove. All these characters are shared with the holotype of Mikadocephalus gracilirostris Maisch & Matzke, 1997, which we consider as a junior synonym of B. leptorhynchus. An updated phylogenetic analysis, which includes revised scores for B. leptorhynchus and several other shastasaurids, recovers B. leptorhynchus as a basal merriamosaurian, but it is unclear if Shastasauridae form a clade, or represent a paraphyletic group. The inferred body length of the examined specimens ranges from 1 m to about 8 m. The extreme longirostry suggests that B. leptorhynchus primarily fed on small and elusive prey, feeding lower in the food web than an apex predator: a novel ecological specialisation never reported before the Anisian in a large diapsid. This specialization might have triggered an increase of body size and helped to maintain low competition among the diverse ichthyosaur fauna of the Besano Formation

Semiaquatic adaptations in a giant predatory dinosaur

Mysterious dinosaur a swimmer? Dinosaurs are often appreciated for their size and oddity. In this regard, the North African carnivorous theropod Spinosaurus , with its huge dorsal sail and a body larger than Tyrannosaurus rex , has long stood out. This species also stands out because of its history. The unfortunate loss of the type specimen during World War II left much of what we know about Spinosaurus to be divined through speculation and reconstruction. Ibrahim et al. now describe new fossils of this unusual species. They conclude it was, at least partly, aquatic, a first for dinosaurs. Science , this issue p. 1613 </jats:p

Carta de restauração dos fósseis

A Itália é um país com forte tradição no campo da restauração. Não surpreende, portanto, que a Carta de Restauração dos Fósseis tenha nascido em contexto italiano. O documento, publicado em 1998, organiza e sistematiza informações sobre cada atividade que possa influenciar na longevidade do fóssil, desde a escavação até o momento de guarda em uma instituição. Apesar de muitos dos pontos abordados serem intrínsecos do “fazer paleontologia”, algumas questões nos parecem relevantes para profissionais que queiram tratar de fósseis. Algo importante a enfatizar, por exemplo, é a inclusão de informações de campo, de preparação e conservação na documentação do registro na coleção científica – dados já apontados para uma documentação museológica. Outro ponto importante a destacar é a necessidade das instituições de prover laboratórios de preparação, restauração e conservação para os vários objetos de pesquisa, com profissionais qualificados nas diversas áreas de conhecimento necessárias para estas atividades. Infelizmente, isso ocorre pontualmente em certas instituições. Acreditamos que as normas de restauração e de conservação de fósseis, normalmente dispersas em várias bibliografias, foram habilmente sintetizadas na presente carta, favorecendo o conhecimento dos princípios básicos dos critérios de base e normas a serem seguidas para a coleta, preparação, restauração e conservação de material fóssil. E, ainda que a realidade italiana seja diversa da brasileira em muitos aspectos, as boas práticas indicadas no texto têm o potencial de servir de norte para políticas de gestão de coleções paleontológicas. Por fim, agradecemos ao Dr. Vittorio Borselli, coordenador da presente Carta, por conceder a autorização para tradução do documento, e assim, proporcionar sua difusão abrangente entre os profissionais que trabalham com a curadoria de material paleontológico no Brasil

S2 - 3D model of MSNM V6216

Specimen MSNM V6216 comes from the Sakaraha Formation (Isalo IIIb subunit), which is Bathonian in age (Middle Jurassic). It has been collected in 2003, isolated from other fossils. A peculiar character of this specimen is the twisting of the crown, where it approaches the crown tip. This character has been considered to be a synapomorphy of Brachiosauridae (D’Emic 2012). It is attributed to morphotype J3 and included in taxon B, which represents a basal Brachiosauridae or basal Titanosauriformes. This 3D model has been generated with photogrammetry processing and merging 71 photos together, divided in two groups, to obtain an object with about 795000 faces. Description in the main text

S3 - 3D model of MSNM V6217

Specimen MSNM V6217 comes from the Sakaraha Formation (Isalo IIIb subunit), which is Bathonian in age (Middle Jurassic). It has been collected in 2003, isolated from other fossils. It is distinguished by a unique elongate, spindle–like shape, and by a transverse section that remains subcircular up to one-third of the crown height. This specimen is the only representative of morphotype J8, taxon D, which should belong to Diplodocoidea (Dicraeosauridae?) or Titanosauria. MSNM V6217 might represent a new taxon, maybe a basal member of Diplodocoidea, and the oldest fossil record of the clade in Africa. This 3D model has been generated with photogrammetry processing and merging 50 photos together, divided in two groups, to obtain an object with about 1000000 faces. Description in the main text

FIRST SKELETAL REMAINS OF HELVETICOSAURUS FROM THE MIDDLE TRIASSIC ITALIAN OUTCROPS OF THE SOUTHERN ALPS, WITH REMARKS ON AN ISOLATED TOOTH

The enigmatic marine reptile Helveticosaurus zollingeri, from the Middle Triassic Besano Formation of Monte San Giorgio, is known from three specimens found in Swiss territory. This paper describes the first skeletal remains of this taxon recovered from the corresponding Italian outcrops of Besano (Varese). An isolated tooth assigned to the same taxon and coming from the San Salvatore Dolomite, Rasa di Varese (Varese), is also redescribed herein. The skeletal remains have been CT scanned to inspect the preserved morphology of the bones hidden below the surface; CT data also allowed the identification of an associated ammonoid which has been crucial to determine the stratigraphic position of the studied material. The redescription of the tooth has been helped by a digital model of the specimen obtained through photogrammetry. With the additional new data obtained from the two specimens, the first skeletal reconstruction of Helveticosaurus is provided. This is followed by a phylogenetic test of the taxon, assessing its position among marine Triassic diapsids. Finally, in the light of recent studies we discuss the swimming mode and the possible ecological niche occupied by the animal: we suggest a distinction between the function of forelimbs and hindlimbs, and a distinction between different swimming styles likely performed by Helveticosaurus, depending on the speed of movements