A new ankylosaurid from the Upper Cretaceous Nemegt Formation of Mongolia and implications for paleoecology of armoured dinosaurs

A new ankylosaurid dinosaur, Tarchia tumanovae sp. nov., has been recovered from the Upper Cretaceous Nemegt Formation of Mongolia. It includes a well-preserved skull, dorsal, sacral, caudal vertebrae, sixteen dorsal ribs, ilia, a partial ischium, free osteoderms, and a tail club. The squamosal horns of T. tumanovae are divided into two layers, the external dermal layer and the underlying squamosal horn proper. The irregular ventral margin of the base of the upper dermal layer may represent a resorption surface, suggesting that the squamosal horns of some ankylosaurids underwent extreme ontogenetic remodeling. Localized pathologies on the dorsosacral ribs and the tail provide evidence of agonistic behaviour. The tail club knob asymmetry of T. tumanovae resulted from restricted bone growth due to tail club strikes. Furthermore, T. tumanovae had an anteriorly protruded shovel-shaped beak, which is a morphological character of selective feeders. Ankylosaurid diets shifted from low-level bulk feeding to selective feeding during the Baruungoyot and the Nemegt “age” (middle Campanian-lower Maastrichtian). This ankylosaurid niche shifting might have been a response to habitat change and competition with other bulk-feeding herbivores.

Review of the ammonite genus Pseudokossmaticeras Spath, 1922 from the uppermost Campanian–lower Maastrichtian in Bulgaria

New data on the ammonite genus Pseudokossmaticeras Spath, 1922 have been obtained from several uppermost Campanian–lower Maastrichtian strata of the Fore-Balkan Mountains (Bulgaria). A review of the earlier Bulgarian records of the genus is also presented. The following species are here described and illustrated: Pseudokossmaticeras brandti (Redtenbacher, 1873), P. galicianum (Favre, 1869), P. muratovi Michailov, 1951 and P. tercense (Seunes, 1892). Our newly obtained ammonite records were constrained by the inoceramid zonation that has recently been proposed for successions of the Fore-Balkan area. Hence, the Bulgarian data are of importance for correlation with other occurrences of Pseudokossmaticeras across Europe.

Review of the ammonite genus Pseudokossmaticeras Spath, 1922 from the uppermost Campanian–lower Maastrichtian in Bulgaria

New data on the ammonite genus Pseudokossmaticeras Spath, 1922 have been obtained from several uppermost Campanian–lower Maastrichtian strata of the Fore-Balkan Mountains (Bulgaria). A review of the earlier Bulgarian records of the genus is also presented. The following species are here described and illustrated: Pseudokossmaticeras brandti (Redtenbacher, 1873), P. galicianum (Favre, 1869), P. muratovi Michailov, 1951 and P. tercense (Seunes, 1892). Our newly obtained ammonite records were constrained by the inoceramid zonation that has recently been proposed for successions of the Fore-Balkan area. Hence, the Bulgarian data are of importance for correlation with other occurrences of Pseudokossmaticeras across Europe.

Stratigraphic And Microfacies Study Of Upper Campanian - Lower Maastrichtian Succession (Shiranish Formation) In Bade Village, Bekhere Anticline, Kurdistan Region, Northern Iraq

The Upper Cretaceous Shiranish Formation outcropped close to Bade village and Bekhere anticline, Kurdistan region at northern Iraq and consists of alternating mixed tough grey limestone, marly limestone, marl beds interpreted as a middle - outer shelf – upper bathyal environments (basinal) depositional environment. Fifteen thin sections were studied under a polarized microscope to find out the petrographic component, fauna content, and for microfacies analysis. The major petrographic constituents are fossils, bioclastic grains, micrite matrix, and extraclast (quartz grains). Planktic foraminifera and nannofossils are the major particles within wackestone and packstone microfacies types. The planktonic foraminifera biozones from previous study (such as Globotruncana aegyptiaca, Gansserina gansseri, Racemiguembelina fructicosa, Plummerita hantkeninoides) and the recorded calcareous nannofossils biozones of Broinsonia parca, Reinhardtites levis, Arkhangelskiella cymbiformis, suggest a late Campanian to late Maastrichtian age.

The Tetrapod Fossil Record from the Uppermost Maastrichtian of the Ibero-Armorican Island: An Integrative Review Based on the Outcrops of the Western Tremp Syncline (Aragón, Huesca Province, NE Spain)

The South-Pyrenean Basin (northeastern Spain) has yielded a rich and diverse record of Upper Cretaceous (uppermost Campanian−uppermost Maastrichtian) vertebrate fossils, including the remains of some of the last European dinosaurs prior to the Cretaceous-Paleogene (K-Pg) extinction event. In this work, we update and characterize the vertebrate fossil record of the Arén Sandstone and Tremp formations in the Western Tremp Syncline, which is located in the Aragonese area of the Southern Pyrenees. The transitional and continental successions of these sedimentary units are dated to the late Maastrichtian, and exploration of their outcrops has led to the discovery of numerous fossil remains (bones, eggshells, and tracks) of dinosaurs, including hadrosauroids, sauropods, and theropods, along with other tetrapods such as crocodylomorphs, testudines, pterosaurs, squamates, and amphibians. In particular, this fossil record contains some of the youngest lambeosaurine hadrosaurids (Arenysaurus and Blasisaurus) and Mesozoic crocodylomorphs (Arenysuchus and Agaresuchus subjuniperus) in Europe, complementing the lower Maastrichtian fossil sites of the Eastern Tremp Syncline. In addition, faunal comparison with the fossil record of Hațeg island reveals the great change in the dinosaur assemblages resulting from the arrival of lambeosaurine hadrosaurids on the Ibero-Armorican island, whereas those on Haţeg remained stable. In the light of its paleontological richness, its stratigraphic continuity, and its calibration within the last few hundred thousand years of the Cretaceous, the Western Tremp Syncline is one of the best places in Europe to study the latest vertebrate assemblages of the European Archipelago before the end-Cretaceous mass extinction.

A new lithophylacid crab (Crustacea, Decapoda, Portunoidea) from the Late Cretaceous (early Maastrichtian) of Cuba

Icriobranchiocarcinus rodas Vega n. sp., is recorded from lower Maastrichtian (Upper Cretaceous) Arroyo Grande Formation near the town of Rodas (Central Cuba). I. rodas Vega n. sp. represents additional evidence of paleobiogeographic affinities between Chiapas (SE Mexico) and Cuba, during the Late Cretaceous. The genus Icriobranchiocarcinus Vega, 2018 in Vega et al., 2018 was erected from the type species Icriobranchiocarcinus tzutzu Vega, 2018 from the lower Maastrichtian Ocozocoautla Forma-tion (Chiapas). I. rodas Vega, n. sp. preserves details of ventral morphology as well as more details of chelipeds not reported in I. tzutzu, adding to the morphology of the genus. Icriobranchiocarcinus belong to a family (Lythophylacidae Van Straelen, 1936) that became extinct worldwide during the K/Pg event.

Shallow-marine serpentinization-derived fluid seepage in the Upper Cretaceous Qahlah Formation, United Arab Emirates

Serpentinization of ultramafic rocks in the sea and on land leads to the generation of alkaline fluids rich in molecular hydrogen (H2) and methane (CH4) that favour the formation of carbonate mineralization, such as veins in the sub-seafloor, seafloor carbonate chimneys and terrestrial hyperalkaline spring deposits. Examples of this type of seawater–rock interaction and the formation of serpentinization-derived carbonates in a shallow-marine environment are scarce, and almost entirely lacking in the geological record. Here we present evidence for serpentinization-induced fluid seepage in shallow-marine sedimentary rocks from the Upper Cretaceous (upper Campanian to lower Maastrichtian) Qahlah Formation at Jebel Huwayyah, United Arab Emirates. The research object is a metre-scale structure (the Jebel Huwayyah Mound) formed of calcite-cemented sand grains, which formed a positive seafloor feature. The Jebel Huwayyah Mound contains numerous vertically orientated fluid conduits containing two main phases of calcite cement. We use C and O stable isotopes and elemental composition to reconstruct the fluids from which these cements precipitated and infer that the fluids consisted of variable mixtures of seawater and fluids derived from serpentinization of the underlying Semail Ophiolite. Based on their negative δ13C values, hardgrounds in the same section as the Jebel Huwayyah Mound may also have had a similar origin. The Jebel Huwayyah Mound shows that serpentinization of the Semail Ophiolite by seawater occurred very soon after obduction and marine transgression, a process that continued through to the Miocene, and, with interaction of meteoric water, up to the present day.

Inoceramid bivalve and dinoflagellate cyst integrated biostratigraphy of the topmost Campanian–Maastrichtian in a part of the Western Fore-Balkan Mountains, northwest Bulgaria

We present the inoceramid and dinoflagellate cyst record from the topmost Campanian–Maastrichtian strata of three key sections of the Western Fore-Balkan Mountains, northwest Bulgaria. The following inoceramid zones were recognized: “Inoceramus” redbirdensis Zone, Endocostea typica Zone, Trochoceramus radiosus Zone and “Inoceramus” ianjonaensis Zone. The Campanian/Maastrichtian boundary was tentatively drawn slightly below the first occurrence of Endocostea typica. The uppermost inoceramid assemblage was confined to the lower part of the upper Maastrichtian. Dinoflagellate cyst ranges, as well as the first and the last occurrence events of dinocysts, provided valuable markers for the stratigraphic subdivision of the Maastrichtian. The first occurrence of Microdinium carpentierae was documented in proximity to the Campanian/Maastrichtian boundary. The Cerodinium diebelii Zone was recognized with a stratigraphical range from the lower Maastrichtian to the lower upper Maastrichtian. The last occurrence of Alterbidinium acutulum was recorded in the lower Maastrichtian and used as aid for tracing the lower/upper Maastrichtian substage boundary. The marked domination of delicate chorate dinocysts in all sections and the encountered low P/G ratio values are indicative of stable low-energy depositional environment and oligotrophic conditions, with normal marine productivity and nutrient availability in the basin during the Maastrichtian.