Lower Maastrichtian Research Articles

Mosasaur (Reptilia, Mosasauridae) remains from the Upper Cretaceous of Colombia, including the first occurrence of the genus Globidens

Isolated mosasaur teeth and vertebrae recovered from beds of the Guadalupe Group of central Boyacá, Colombia, are reported. A partial tooth crown identified as Globidens sp., found in the Labor-Tierna Formation (Maastrichtian), represents the first report of this genus from northern South America and its most equatorial occurrence. A tooth crown recovered from the Plaeners Formation (upper Campanian–lower Maastrichtian), represents the youngest record of the subfamily Plioplatecarpinae in Colombia. These occurrences collectively constitute the youngest record of the family Mosasauridae in Colombia and expand both the taxonomic diversity and biogeography of mosasaurids in northern South America.

Review of two marine vertebrate assemblages from the Arauco Basin (central Chile) reveals diversity changes throughout the Maastrichtian

Upper Cretaceous vertebrate records from Chile are mostly known by historical mentions with unknown repositories and uncertain stratigraphic provenance. This contribution reviews and complements two marine vertebrate assemblages from the Upper Cretaceous of central Chile, which were part of the ancient Arauco Basin. The oldest assemblage (lower Maastrichtian) comprises abundant condrichthyans referred to Carcharias gracilis, Odontaspis cf. winkleri, Scapanorhynchus sp., Centrophoroides appendiculatus, Squatina sp., Cretorectolobus sp., Orectolobidae indet., Paraorthacodus sp., Ischyrhiza chilensis and Biropristis landbecki, which adds to the previously reported occurrences of Echinorhinus sp. and Myledaphus araucanus. In addition, chimeroids referred to as Edaphodon kawai and remains of a leatherback turtle referable to Mesodermochelys sp. are here described, the latter being its first occurrence outside Japan. The younger assemblage (upper Maastrichtian) includes similar chondrichthyans and a higher diversity of marine reptiles, including plesiosaurians (Aristonectes sp., Aristonectinae indet., and Elasmosauridae indet.), sea turtles (Pancheloniidae indet.) and diverse mosasaurs (Halisaurus sp., Tylosaurinae indet., and the first local occurrence of Plioplatecarpinae indet.). Throughout the Maastrichtian, the local marine vertebrates likely suffered a declination in abundance but a rise in diversity, with evidence of a marked alteration in middle levels of the trophic web during the upper Maastrichtian. This fauna shows a main influence from the northern hemisphere (especially from the Western Interior Sea), acquiring a more marked Weddellian influence during the end of the Maastrichtian. The studied material allows a better understanding of the Upper Cretaceous vertebrate marine fauna in lower latitudes of the southeastern Pacific.

Stratigraphic Reassessment of the Mexican Chasmosaurine Coahuilaceratops magnacuerna as the First Diagnostic Dinosaur Remains from the Cerro Huerta Formation (Lower Maastrichtian) Supporting the Southern Origin of the Triceratopsini

Very few remains of ceratopsid dinosaurs have been recovered so far from the Difunta Group of Coahuila, Mexico. The enigmatic chasmosaurine Coahuilaceratops magnacuerna was previously described on the basis of two partial skulls purportedly derived from the Cerro del Pueblo Formation (~73–72.5 Ma?). On the basis of a new measured section and lithological identification of the host rock, we reassign Coahuilaceratops to the overlying Cerro Huerta Formation (~71.5–70.5 Ma?). Thus, we formally assign the first dinosaur taxon to the Cerro Huerta Formation. This reassignment is more consistent with the relatively derived phylogenetic position of Coahuilaceratops, with implications for the southern Laramidia hypothesis concerning the origin of the Triceratopsini.

A Late Cretaceous lizard assemblage from the Allen Formation, northern Patagonia, Argentina

ABSTRACT Lizards are poorly known from the Mesozoic of South America, including several specimens from the Lower and Upper Cretaceous of Brazil, and only a few from the Upper Cretaceous of Patagonia. Here, we describe a new lizard assemblage from a single bone-bearing level in the Allen Formation (upper Campanian – lower Maastrichtian), cropping out at the Cerro Tortuga locality, Río Negro Province, northern Patagonia, Argentina. We recognise the presence of three different taxa, all of them represented by partially isolated maxillae, belonging to different lizard lineages: pleurodontan Iguania; Teiioidea; and possibly Scincoidea. These specimens support the presence of a quite diverse lizard assemblage during the Late Cretaceous in southern South America, suggesting that their absence in other Cretaceous deposits from Patagonia represents preservational and/or sampling bias. The taxonomic diversity also points to a broad ecological diversity, because the three taxa strongly differ in their dental morphology and inferred dietary habits. The assemblage from Cerro Tortuga indicates that lizards, along with snakes and sphenodontians, were an important component of the Late Cretaceous lepidosaurian fauna of South America and, likely, Gondwana.

First record of the cosmopolitan brachiopod Praelacazella wetherelli from the lower Maastrichtian of Western Australia

We describe the thecideid brachiopod Praelacazella wetherelli (Morris, 1851) from the lower Maastrichtian Korojon Formation in the Carnarvon Basin, Western Australia. This is the first documented record of Praelacazella wetherelli from the Southern Hemisphere, suggesting that the species was cosmopolitan in distribution during the Late Cretaceous. Three possible long-distance migration routes are discussed.

Scaphitid ammonites from the lower Maastrichtian of Nahoryany (western Ukraine) and discussion on the origin of Hoploscaphites constrictus

Abstract The lower Maastrichtian (Upper Cretaceous) section at Nahoryany, south of Lviv (western Ukraine), has been known as a rich source of fossils since 1843. However, the section is not available since a long time ago and fossils collected from it can only be studied in museum collections. In the present paper, ammonites of the scaphitid genus Hoploscaphites are studied based on Nahoryany material, comprising Hoploscaphites pumilus, H. constrictus and H. sp. Specimens from Nahoryany in museum collections lack data on their provenance level within the section so it cannot be determined whether or not they occurred together or formed a succession; data on inoceramid bivalves indicate the presence of two successive zones at Nahoryany. Some specimens from Nahoryany here referred to as H. pumilus are similar to the controversial H. constrictus anterior from the lower Maastrichtian of Poland. This morphology suggests an ancestor–descendant relationship between H. pumilus and H. constrictus, a common species once considered as an informal index for the Boreal Maastrichtian in Europe. The inferred evolutionary transition from H. pumilus to H. constrictus was towards a less robust, recoiled shell, which would have enhanced the horizontal swimming ability and manoeuvrability of these cephalopods. Recoiling trends occurred in several lineages of Late Cretaceous scaphitids.

The brachiopod assemblage from the Maastrichtian white chalk at Chełm, eastern Poland: stratigraphical and palaeoecological implications

Abstract Brachiopods from the lower upper Maastrichtian (Upper Cretaceous) white chalk succession exposed at Chełm (eastern Poland) comprise Lingula cretacea, Isocrania costata, Cryptoporella antiqua, Cretirhynchia sp., Neoliothyrina sp., Carneithyris sp., Terebratulina chrysalis, T. faujasi, T. longicollis, Terebratulina spp., Gisilina sp., Bronnothyris bronni, Magas chitoniformis, Leptothyrellopsis polonicus and ?Aemula sp. This assemblage is relatively poor in terms of taxonomic diversity and specimen abundance and is dominated by stratigraphically long-ranging species. It is best comparable to that from the micromorphic brachiopod Rugia tenuicostata–Meonia semiglobularis Zone as distinguished in the white chalk successions of Denmark and northern Germany, although this zone is usually placed in the upper lower Maastrichtian. The Chełm succession represents a relatively deep-water and ‘benthos-poor’ variety of white chalk deposited in the Boreal Chalk Sea of Europe. The brachiopod assemblage studied is typical of such a habitat, having been controlled largely by the low availability of minute skeletal substrates suitable for brachiopod settlement.

Relationship of Maastrichtian–Thanetian benthic foraminiferal species diversity, palaeooxygenation, and palaeoproductivity in shallow waters of the Western Desert, Egypt

Benthic foraminiferal analysis (315 samples, 16,271 specimens) of the shallow water (< 100 m) Maastrichtian–Thanetian rocks from the Dakhla Oasis (Western Desert, Egypt) was studied to infer the inter–relationships between species diversity, palaeooxygenation, palaeoproductivity, and palaeodepth and changes at the Cretaceous–Paleogene (K/Pg) boundary. Positive and significant correlations are noted between these proxies, suggesting a well-oxygenated oligotrophic environment. However, a brief interval (mid–lower Maastrichtian) of increased palaeoproductivity with reduced diversity and oxygenation (ventilation) is noted (a characteristic of mesotrophic–eutrophic settings) that coincides with very shallow waters during a highstand system tract (HST) and dominated by the dysoxic agglutinated species Ammobaculites khargaensis. The diversity index, Fisher’s α (< 5), and paleodepth proxy (foraminiferal wall structure types) also suggest a shallow neritic (largely littoral) depth for the entire study interval. At the bottom of the study section (Planktic Foraminiferal Zones CF8b-CF7), species diversity, palaeooxygenation, and palaeoproductivity are high. From the K/Pg boundary to the post-K/Pg period, these variables are low and fluctuate with moderate species dominance. Data suggests an overall 40% benthic foraminiferal species (38% of agglutinated and 40% of calcareous extinct species) extinction rate after the K/Pg hiatus. The period immediately following the K/Pg boundary is characterized by increased basinal ventilation and decreased palaeoproductivity, which are attributed to changes in sea level and concurrent regional subsidence. However, as stable as the community structure was at or just after the K/Pg boundary, the changes in species composition (assemblage) were dramatic and marked by a change from a pre–K/Pg agglutinated–dominated fauna (Haplophragmoides–Ammobaculites) to a post–K/Pg calcareous one (Cibicodoides–Cibicides–Anomalinoides).

Late Maastrichtian (latest Cretaceous) Ammonoids from the Naiba Area, Southern Sakhalin, Russian Far East

Six early late Maastrichtian (Late Cretaceous) ammonoid taxa are reported from the Krasnoyarka Formation of the Yezo Group in the Naiba area, southern Sakhalin, Russian Far East. These taxa are grouped into “immigrant species”, i.e., those that migrated from other regions (Pachydiscus subcompressus, Anagaudryceras mikobokense, Gaudryceras seymouriense and Zelandites varuna) and “indigenous species” with a North Pacific distribution (Anagaudryceras matsumotoi). It is unclear to which group Tetragonites sp. belongs. Zelandites varuna and G. seymouriense occur in both the lower upper Maastrichtian as well as the upper lower Maastrichtian in southern Sakhalin, but they have never been found in the middle Maastrichtian. The appearance of these two species in the cold-water regions, i.e., North Pacific and Antarctic, as well as intermediate southern mid-latitudes regions suggests that cooling events occurred during the late early and early late Maastrichtian in the Northwest Pacific region. Their disappearance during the middle Maastrichtian may indicate that the Northwest Pacific region was affected by the greenhouse Middle Maastrichtian Event (MME). This hypothesis suggests that the influx (e.g. P. subcompressus and A. mikobokense) and reappearance (e.g. Z. varuna and G. seymouriense) of many immigrant species into the Northwest Pacific region during late Maastrichtian time may have been associated with the post-MME cooling.

The Valcheta Petrified Forest (Upper Cretaceous), northern Patagonia, Argentina: A geological and paleobotanical survey

The Valcheta Petrified Forest is located in the northeast of the Río Negro Province, Argentina. This work provides a geological characterization of the site and a survey of the fossil logs exposed on the surface and their systematic study. The fossiliferous levels bearing the silicified logs are here referred to the Allen Formation (middle-upper Campanian – lower Maastrichtian, Malargüe Group). These deposits crop out in patches in the study area, and have been deposited on a paleorelief carved in Eopaleozoic rocks of the Nahuel Niyeu Formation being mostly covered by thin layers of Quaternary sediments. The Valcheta Petrified Forest was developed on the margins of a braided fluvial system. Numerous silicified logs have been located at the site. They consist of large axes, not found in life position, with monopodial growth, some of which retain the bases of lateral branches and flared-like base. The estimated height and ages of these trees suggests that it consisted of a mature forest. No other associated vegetative or reproductive structures have been found. Anatomically, a single xylological type has been distinguished and assigned to Podocarpoxylon mazzonii (Petriella) Müller-Stoll et Schultze-Motel, (Podocarpaceae). This taxon has been previously identified from other localities of the Upper Cretaceous to the Danian of Patagonia although never preserved in such complete tree grow architecture. This shows that, along others conifers, cycads and palms, P. mazzonii would have constituted an important element of the arboreal strata in the North Patagonian forest communities during the Campanian–Danian interval producing monotypic patches in some areas.

Anatomy of the neornithischian dinosaur Parksosaurus warreni (Parks, 1926) from the Upper Cretaceous (lower Maastrichtian) Horseshoe Canyon Formation of Alberta, Canada

The fossil record of Late Cretaceous non-hadrosaurid neornithischians from the Western Interior of North America is sparse. Parksosaurus warreni is an early Maastrichtian taxon currently known only from a skull and much of the associated postcranial skeleton and a referred isolated tooth from the Horseshoe Canyon Formation of Alberta, Canada. This article presents a detailed anatomical account of the holotype of this species following extensive additional preparation of the holotype and provides photographs of the postcranial elements for the first time. The premaxilla has a dorsoventrally deep posterolateral process, which overlaps the maxilla. The antorbital fenestra is small and teardrop-shaped. The lingual surfaces of dentary teeth bear nine or 10 vertically extending ridges that terminate in apical denticles. The suprascapula is mineralized or ossified. The dorsal margin of the ischium is posterodorsally concave at mid-length. The greater and lesser trochanters of the femur are not separated by a distinct cleft. The pendent fourth trochanter is placed on the proximal half of the femur. The more distal caudal vertebrae have greatly elongated prezygapophyses, which, together with a basket of ossified tendons ensheathing the caudal vertebrae, indicate that the tail may have functioned as a dynamic stabilizer during locomotion. The substantial new anatomical information from the holotype and only known skeleton of Parksosaurus warreni will allow more detailed comparisons to other closely related taxa and facilitate further discussions of unresolved aspects of the interrelationships of neornithischian dinosaurs.

Calcareous nannofossil biostratigraphy and paleogeographic significance in the lower Maastrichtian of the Miechów Trough (southern Poland)

Biostratigraphic analysis of calcareous nannofossils from the Pełczyska section in the Miechów Trough (southern Poland) has revealed that the entire section covers the lowermost Maastrichtian. The UC16bTP Tethyan subzone is designated based on the presence of Broinsonia parca constricta Hattner, Wind and Wise, 1980, reworked remains of Uniplanarius trifidus (Stradner) Hattner and Wise in Wind and Wise, 1983 and the simultaneous lack of Eiffellithus eximius (Stover) Perch-Nielsen, 1968. The studied section spans also the interval between the LO of Zeugrhabdotus praesigmoides Burnett, 1997 and the FO of Prediscosphaera mgayae Lees, 2007 (UC16 S3 Boreal subzone). Quantitative analysis of nannofossil assemblages has shown the dominance of cold water species (up to 50%), e.g., Micula decussata Vekshina, 1959, Prediscosphaera spp., Arkhangelskiella spp., Calculites obscurus (Deflandre) Prins and Sissingh in Sissingh, 1977 and Lucianorhabdus cayeuxii Deflandre, 1959. In the early Maastrichtian, the studied area was more influenced by cool water masses from the Boreal Province rather than by warm water from the Tethyan Province. The significant predominance of cold water taxa and the elevated presence of Prediscosphaera cretacea (Arkhangelsky) Gartner, 1968 also supports the hypothesis of climate cooling in the early Maastrichtian.

Dinoflagellate cysts from the Upper Cretaceous (Campanian–Maastrichtian) from The Naze Peninsula, James Ross Island, Antarctica

We present the results of the quantitative and qualitative study of dinoflagellate cysts in outcrop samples from a section of the Snow Hill Island Formation (SHF) in James Ross Island, Antarctic. Dinoflagellate cysts assemblages are abundant and dominated by gonyaulacoid taxa. The last occurrence of the dinoflagellate cyst Kallosphaeridium? helbyi and Chatangiella granulifera, together with the first occurrence of Pterodinium cretaceum, indicates a probable late Campanian age (∼76.4–∼72.1 Ma) for the lower strata. Whereas the first occurrence of Manumiella bertodano and the last occurrence of Odontochitina operculata, Xenascus ceratioides, and Stiphrosphaeridium anthophorum indicate an early Maastrichtian (∼72.1–∼70.0 Ma) age for the upper strata. Our results, combined with paleobotanical and palynological published data, indicate medium–high continental and marine productivity with temperate paleoclimate free of glaciers for this interval. Lithological and paleontological data indicate mainly inner neritic marine depositional environments. The predominance of shales in the lower part of the lower Maastrichtian interval indicates a slightly deeper environment. In contrast, in the middle part of the lower Maastrichtian, a shallower, transitional environment is marked by the presence of theropod dinosaurs and decapod crustaceans.

New occurrences of caryophylliid and fungiacyathid scleractinian corals from the Santa Marta and Snow Hill Island formations (Upper Cretaceous, Antarctica)

Scleractinian corals have been reported in the Antarctic Cretaceous since the beginning of the 20th century, but few studies have described the taxonomy of these specimens. Here we describe three new occurrences of coral from the James Ross Basin based on specimens collected in 2016. We identified Dasmosmilia? sp. and Heterocyathus filkorni sp. nov. in the Alpha Member of the Santa Marta Formation on James Ross Island (upper Santonian to lower Campanian) and Fungiacyathus deltoidophorus and a poorly-preserved and unidentifiable scleractinian coral from the Karlsen Cliffs Member of Snow Hill Island Formation (lower Maastrichtian). Heterocyathus filkorni sp. nov. represents the earliest occurrence of this genus in the Southern Hemisphere and is consistent with the hypothesis that a marine exchange between Europe and Antarctica was occurring in the Late Cretaceous. If confirmed, the Dasmosmilia described here represent their earliest record from the Antarctic Cretaceous.

Historical material of cf. Thoracosaurus from the Maastrichtian of Denmark provides new insight into the K/Pg distribution of Crocodylia

Crocodylia are one of the distinctive groups that survived the K/Pg mass extinction event. New material from Upper Cretaceous–lower Palaeogene deposits is therefore important to understanding shifts in crocodylian distribution and ecology. This paper describes a fragmentary mandible of a marine crocodylian, from the lower Maastrichtian (Upper Cretaceous) of Møns Klint (Denmark). The specimen is referred to cf. Thoracosaurus (Gavialoidea). Although the material was collected in 1968, it has not yet been formally described. However, the specimen warrants further attention, given its palaeoecological and palaeobiogeographical significance. For instance, the Møns Klint “Thoracosaurus” is an indication of increased competition between large piscivores, and of added predation pressure on fish and cephalopod communities. This gavialoid therefore provides new insight into predator-prey interactions in the Danish Chalk palaeoenvironment. Regarding crocodylian distribution, the Møns Klint specimen represents the oldest European gavialoid record, with all other material deriving from uppermost Maastrichtian and Danian deposits. This indicates that Gavialoidea were present in the European “Chalk Sea” throughout the Maastrichtian, rather than being latest Maastrichtian arrivals. Furthermore, the Møns Klint “Thoracosaurus” represents one of few lower Maastrichtian gavialoids worldwide, the other two being from Mississippi and New Jersey (USA). The specimen thus extends the palaeogeographical range of lower Maastrichtian gavialoids across the proto-Atlantic. This reveals transatlantic distribution of Gavialoidea dating back to the earliest Maastrichtian, providing further evidence for distributional communication between marine vertebrate faunas of North America and Europe. These factors make the Møns Klint “Thoracosaurus” particularly valuable to understanding the distribution of K/Pg Crocodylia.

Mark of ectoparasitic activity on a bothremydid (Pleurodira) turtle shell from the Lo Hueco site (Upper Cretaceous, Central Spain)

Shell pitting is relatively abundant but with unclear character and etiology in extinct turtles, since reports on extant turtles with similar condition do not usually include morphological descriptions, illustrations, or data concerning etiology or pathogenesis. Therefore, the available interpretations on shell pitting in the fossil record of turtles are generally speculative or poorly justified. We analyze herein a mark identified in a partial carapace of a bothremydid turtle from the Upper Cretaceous (upper Campanian–lower Maastrichtian) fossil site of Lo Hueco (Cuenca, Central Spain). This mark has been analyzed both through physical examination and by the use of computerized axial tomography scan. The discussion has been established following a differential diagnosis procedure, a presumptive diagnosis was made on the basis of analogy and total or partial similarities with other cases previously documented both in extinct and extant turtle specimens. As a result, information regarding the possible etiology, pathogenesis, and stages of healing of the mark studied here are provided. An ectoparasitic origin is suggested as the most parsimonious hypothesis explaining its etiology, this mark being considered as a pathology. This study represents to the first report of a pathology of ectoparasitic origin in the shell of a bothremydid turtle.

“Slime stars” (Echinodermata, Asteroidea, Velatida) from the Upper Cretaceous of northern Europe

The Cretaceous record of the predominantly deep-sea velatidan starfish families Korethrasteridae and Pterasteridae is described on the basis of dissociated, but well-preserved ossicles (adambulacrals, orals) from the Cenomanian to Maastrichtian chalks of the Anglo-Paris Basin, and marginal marine deposits at Ivö Klack, Kristianstad Basin (southern Sweden). A new genus and species of korethrasterid, Furculaster cretae gen. et sp. nov., are erected, and the only known fossil occurrence of the living genus Peribolaster is recorded from Sweden. In addition, Kutscheraster ruegenensis gen. et sp. nov. is described from the lower Maastrichtian of Rügen (northeast Germany). Seven new species of Pteraster are introduced; P. turoniense, P. seafordensis, P. nudus, P. angulatus, P. cretachiton, P. kutscheri, P. paucispinus and P. balticus. Comparative ossicle morphology permits placement of some Cretaceous species in groups of extant Pteraster (i.e., P. myonotus Group, P. temnochiton Group, P. tesselatus Group and P. pulvillus Group). It is argued that these groups had already evolved by the Late Cretaceous, providing evidence for an ancient origin of this deep-sea group.

Ray-finned fishes (Actinopterygii) from the lower Maastrichtian of Algarrobo, central Chile

This research presents new material of ray-finned fishes recovered from Upper Cretaceous strata exposed in the city of Algarrobo, central Chile. The material includes specimens here referred to the genus Enchodus, which are the first local records of early Maastrichtian age. Three coeval, isolated teeth are here referred to the genus Pachyrhizodus, and six distinctive, barracuda-like teeth are here referred to as indeterminate pachycormids. These finds represent the first record of Pachyrhizodus and the second record of a pachycormid in the Upper Cretaceous of southern South America. In addition, it is provided a critical review of the historic ray-finned fishes from the Upper Cretaceous Quiriquina Formation of central Chile and equivalent units within the Arauco Basin. The updated information suggests that latest Cretaceous actinopterygian diversity along the southeastern Pacific was much discrete than previously thought, and unusually scarce in terms of abundance. Locally, this scarcity was already present during the lower Maastrichtian and persisted throughout the end of the Cretaceous.

Paleoenvironmental and paleoclimatic changes during the Late Cretaceous and Cretaceous–Paleogene (K/Pg) boundary transition in Tattofte, External Rif, northwestern Morocco: implications from dinoflagellate cysts and palynofacies

This paper presents a quantitative study of dinoflagellate cysts (dinocysts) and palynofacies of the Campanian–Danian marly succession at the village of Tattofte (western External Rif, northwestern Morocco). The paleoenvironmental and paleoclimatic interpretations, inferred from this palynologic analysis, are compared to coeval sequences of other areas in the Northern Hemisphere. Changes in the relative abundances of dinocyst taxa, which are paleoenvironmental indicators, throughout the section suggest a deposition in a marine inner to outer neritic setting. The upper Campanian dinocyst assemblage is characterized by the presence of outer neritic-oceanic and low productivity indicator taxa (e.g., Spiniferites spp., Odontochitina spp.) and cold-water taxa (e.g., Manumiella spp., Chantangiella spp., Laciniadinium spp.), whereas, the lower Maastrichtian assemblage is characterized by inner neritic, high productivity and warm-water indicator taxa (e.g., Palaeocystodinium spp., Andalusiella spp.). The upper Maastrichtian dinocyst assemblage displays a return to an outer neritic environment under a transgressive regime, but with a cooling pulse and a moderate productivity. However, the Cretaceous–Paleogene (K/Pg) boundary interval records remarkable changes in the relative abundances of dinocyst taxa, indicating an inner neritic (coastal) setting, which is the most proximal in the study section; such changes reflect instable paleoenvironmental conditions which may be related to global cooling periods, likely caused by the Deccan volcanism in India and/or the Chicxulub asteroid impact in Mexico at the K/Pg boundary. In the Danian, the dinocyst relative abundances indicate a gradual return to stable environmental conditions.A quantitative analysis of the kerogen plots (palynomorphs, phytoclasts and amorphous organic matter (AOM)) reveals five types of palynofacies, generally indicating oxic to suboxic marine environments. The upper Campanian and upper Maastrichtian (lowermost part) strata are characterized by a playnofacies (V), indicating a distal shelf, while the lower Maastrichtian and lower Danian (uppermost part) strata record a playnofacies (III), reflecting an intermediate inner-outer neritic environment. However, the K/Pg boundary transition is characterized by playnofacies types (I) and (II), indicating a proximal (coastal) environment.

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.