Giovanne M. Cidade, AndrÃs SolÃrzano, AscÃnio D. RincÃn, Annie Schmaltz Hsiou & Fernando Henrique de S. Barbosa (2017)
On a cranial bony nodular protuberance on Mourasuchus pattersoni Cidade et al. 2017 (Crocodylia, Alligatoroidea) from the late Miocene of Venezuela.
Historical Biology (advance online publication)
Mourasuchus pattersoni, from the late Miocene Urumaco Formation of Venezuela, is the fourth and most recent species described for the genus. The holotype, and only known specimen, is comprised of an almost complete skull with both mandibular rami and several postcranial remains. In ventral view, the right palatine bone has a spherical, nodular bony protuberance located on the anterior portion, near the suture with the maxilla. Unfortunately, we cannot assign a specific diagnosis based only on macroscopic inspection. Its appearance, form and location are compatible with three conditions: torus palatinus, a common benign intraoral bone overgrowth; osteoma, a benign neoplasical overgrowth of the bone; and hamartoma, an overgrowth of normal bone tissue that can only be differed from an osteoma by histological features. While occurrences of torus palatinus or hamartomas are not yet known in the nonhominid vertebrate fossil record, there are previous records of osteomas in fossil vertebrates, including in crocodylians, such as a specimen assigned to âCrocodylus sp.â from the Eocene, aside from several records for living crocodylians. Future studies are needed to uncover an accurate diagnosis of this unusual structure and help increase our knowledge of paleopathology in fossil crocodylomorphs in general, especially in the Caimaninae clade.
Georgios L. Georgalis (2017)
Necrosaurus or Palaeovaranus? Appropriate nomenclature and taxonomic content of an enigmatic fossil lizard clade (Squamata).
Annales de PalÃontologie (advance online publication)
Necrosaurus cayluxi is an enigmatic lizard from the Paleogene of the Phosphorites of Quercy, France that was first mentioned in the 19th century. Although it is generally believed that Filhol was the author who established this taxon, I am herein demonstrating that authorship should in fact be attributed to Zittel, a fact that also influences not only its generic nomenclature, but also its appropriate type material. As such, the valid name for this taxon should be Palaeovaranus cayluxi and its holotype is a left maxilla. Additionally, Ophisauriscus eucarinatus from the middle Eocene of Geiseltal, Germany, another taxon that was previously assigned to Necrosaurus, is herein shown to be a nomen dubium, whereas Melanosauroides giganteus from the same locality, is considered a valid species and is recombined as Palaeovaranus giganteus comb. nov. The suggested changes in nomenclature also affect âNecrosauridaeâ, a poorly defined clade of lizards from the CretaceousâPaleogene of Europe, North America, and Asia. In order to maintain nomenclatural stability and define a monophyletic lineage, I am here establishing the new family Palaeovaranidae fam. nov., which includes solely the genus Palaeovaranus. The known occurrences of Palaeovaranus across the Paleogene of Western Europe are discussed.
David A. Eberth (2017)
Stratigraphy and paleoenvironmental evolution of the dinosaur-rich Baruungoyot-Nemegt succession (Upper Cretaceous), Nemegt Basin, southern Mongolia.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
Baruungoyot-Nemegt succession > 350 m thick; Nemegt Formation > 235 m thick.
Nemegt Fm. divisible into lower, middle, and upper lithostratigraphic intervals.
Ancient diamicts common; identical to modern Gobi-desert occurrences.
Seven stratigraphically-arranged paleoenvironmental zones present.
Paleoenvironmental zones reflect alluvial fan, fluvial, paludal, eolian settings.
Paleoclimate varied from mesic to seasonally wet-dry to arid.
Portions of the dinosaur-rich Upper Cretaceous Baruungoyot-Nemegt succession are exposed in four geographic areas of the Nemegt Basin, Mongolia: Nemegt, Altan Uul, BÃgiin Tsav, and Hermiin Tsav. Lithostratigraphic correlations of these areas employ marker beds and non-random stratigraphic patterns of lithology, grain-size variation, and inferred paleoenvironments. Correlations suggest a minimum thickness of 350 m for the succession. Exposures at Nemegt, Altan Uul, and BÃgiin Tsav form a 100 km east-west transect along the northern margin of the basin, exposing 265 m of section. From east to west the transect exposes higher portions of the succession, extending from the uppermost Baruungoyot Formation and encompassing an almost complete section of the Nemegt Formation, which has a minimum thickness of 235 m and can be consistently divided into three informal members: lower, middle, and upper. The lower Nemegt is well exposed at Nemegt and Altan Uul and is dominated by fluvial deposits. The middle and upper Nemegt are well exposed at Altan Uul 2 and BÃgiin Tsav and consist of alluvial plain, paludal, lacustrine, and fluvial deposits. As confirmed by earlier studies, the Baruungoyot and Nemegt formations exhibit an interfingering transition at Nemegt. The Hermiin Tsav section is a geographic outlier, tens of kilometers west-southwest of the northern transect. It exposes about 150 m of section that overlaps with, but is mostly lower, stratigraphically, than the northern transect. The uppermost Hermiin Tsav section correlates with the lowermost Nemegt section, and also exhibits an interfingering contact between the Baruungoyot and Nemegt formations. The remaining section at Hermiin Tsav comprises sediments of the Baruungoyot Formation (135 m) that were deposited in alluvial fan, fluvial, paludal, lacustrine, and eolian environments, and can be divided into two informal members designated as lower and upper. The distribution of facies through the composite section records changes in paleoenvironments during the Late Cretaceous that may provide insights into the origins of the dinosaurian biostratigraphy.