Aptian Albian Research Articles

Crayfish bio-gastroliths from eastern Australia and the middle Cretaceous distribution of Parastacidae

AbstractFossil crayfish are typically rare, worldwide. In Australia, the strictly Southern Hemisphere clade Parastacidae, while ubiquitous in modern freshwater systems, is known only from sparse fossil occurrences from the Aptian–Albian of Victoria. We expand this record to the Cenomanian of northern New South Wales, where opalized bio-gastroliths (temporary calcium storage bodies found in the foregut of pre-moult crayfish) form a significant proportion of the fauna of the Griman Creek Formation. Crayfish bio-gastroliths are exceedingly rare in the fossil record but here form a remarkable supplementary record for crayfish, whose body and trace fossils are otherwise unknown from the Griman Creek Formation. The new specimens indicate that parastacid crayfish were widespread in eastern Australia by middle Cretaceous time, occupying a variety of freshwater ecosystems from the Australian–Antarctic rift valley in the south, to the near-coastal floodplains surrounding the epeiric Eromanga Sea further to the north.

Cretaceous (Hauterivian–Cenomanian) palaeoceanographic conditions in southeastern Tethys (Matruh Basin, Egypt): Implications for the Cretaceous climate of northeastern Gondwana

Quantitative palynological, sedimentological, and geophysical data analyses of the Cretaceous Abu Tunis 1X well from the Matruh Basin, northwestern Egypt indicate deposition of four major alternating regressive–transgressive successions. Sedimentation was largely affected by the Tethyan 2nd order sea level changes, with minor overprints by regional tectonics. The Lower Cretaceous part of the succession shows regressive sequences of deltafront to delta-top (upper Hauterivian–lowermost upper Barremian), delta channel (upper Aptian–middle Albian), and distal deltaic (upper Albian) settings that were interrupted by transgressive inner–proximal middle shelf deposits (uppermost Barremian–middle Aptian). These sediment packages correspond to Tethyan sea level fall from the late Hauterivian to late Barremian, and to the early–middle Aptian long-term sea level high stand. The Tethyan late Aptian–middle Albian long-term (2nd order) sea level rise was masked by regional late Aptian–Albian uplift, which affected deposition of the later regressive sequence. The Cenomanian shows a change in depositional setting from a proximal inner shelf (lower Cenomanian) to a middle shelf setting (middle–upper Cenomanian), corresponding to the Tethyan long-term latest early–late Cenomanian sea level rise.We demonstrate that northeastern Gondwana (Egypt) experienced different climatic conditions from other parts of the Northern Gondwana Phytogeographic Province. The climate in Egypt shifted from less warm and more humid conditions of the Hauterivian–early Barremian to a warmer and drier climate during the late Barremian–middle Aptian, although never becoming as dry as western Northern Gondwana. Warmer and more humid conditions were reestablished during the late Aptian and became even more accentuated during the Albian–Cenomanian, in contrast to the warm and much drier climate of Northern Gondwana at that time. Turonian climatic conditions may have been less humid as a result of the breakup of the Western Gondwanan supercontinent and the northeasterly drift of the African continent. The climatic conditions experienced in northeastern Gondwana developed through the early-mid Cretaceous as a result of changes in palaeolatitudinal position, variations in sea level, and shifts in the Intertropical Convergence Zone, which drove fluctuations between periods of warm humid and warm dry conditions.

A New Eobaatarid Multituberculate (Mammalia) from the Lower Cretaceous Fuxin Formation, Fuxin-Jinzhou Basin, Liaoning, Northeastern China

Five multituberculate species have been reported to date from the upper Lower Cretaceous (Aptian–Albian) Shahai and Fuxin formations in Liaoning Province, northeastern China. We herein describe an additional species of eobaatarid multituberculate from the Fuxin Formation, Dolichoprion lii, gen. et sp. nov., with a long (relative to height) crown of the fourth lower premolar, which is unique among eobaatarids. We also describe the upper dentition possibly referable to another eobaatarid genus previously known only from lower jaws, Liaobaatar, based on a newly discovered specimen. The new species is the sixth multituberculate (and the fourth eobaatarid) species described from the Shahai and Fuxin formations. These species suggest that multituberculates, especially eobaatarids, were taxonomically quite diverse in the mammalian fauna of East Asia at that time.

Early Cretaceous tectonostratigraphic evolution of the Erlian Basin, NE China: A record of Late Mesozoic intraplate deformation in East Asia

Abstract The Erlian Basin is one of the largest intracontinental Meso-Cenozoic basins in Northeast China. The basin is filled with extra-thick Cretaceous sediments and offers unique opportunities to untangle the Late Mesozoic intraplate deformation in East Asia. However, despite decades of petroleum exploration in the basin, the Early Cretaceous chronostratigraphy and structural evolution of the Erlian Basin have been poorly studied. Based on newly obtained zircon U-Pb geochronological data, well lithological logs, and seismic reflection profiles, the present study carries out a detailed analysis of the tectonostratigraphic evolution of the Erlian Basin during the Early Cretaceous. The depositional ages of the Lower Cretaceous strata in the basin are refined, and the Early Cretaceous evolution of the basin is reestablished. The Lower Aershan, Upper Aershan, Lower Tenggeer, Upper Tenggeer, and Saihan formations are constrained to the middle Valanginian (ca. 138–135 Ma), late Valanginian (ca. 135–133 Ma), Hauterivian–early Aptian (ca. 133–121 Ma), middle Aptian (ca. 119–115 Ma), and latest Aptian–Albian (post ca. 115 Ma), respectively. The Early Cretaceous syn-rift subsidence of the basin was intermittent rather than continuous, and was punctuated by multiphase contractional deformation during the earliest Cretaceous (prior to ca. 138 Ma), middle Valanginian (ca. 135 Ma), latest Valanginian (ca. 133 Ma), middle Aptian (ca. 120 Ma), late Aptian (ca. 115 Ma), and Early/Late Cretaceous boundary. We tentatively attribute the extensional and contractional deformation in the Erlian Basin to a series of continental collisions along Asian margins: Karakoram-Lhasa/Qiangtang collision, Kolyma-Omolon/Siberia collision, Siberia/Amuria collision, Chukotka/Kolyma-Omolon collision, West Philippines/South China collision, and Okhotomorsk/East Asia collision.

A Lower Cretaceous dinosaur track assemblage from the Taoqihe Formation in Central Heilongjiang, China

An Early Cretaceous dinosaur ichnofauna is reported from the Taoqihe Formation (Aptian–Albian) in Heilongjiang Province, China. The assemblage, which comprises >70 tracks in 5 trackways, includes parallel sauropod trackways, a toe-trace dominated tridactyl ornithopod trackway and elongate tridactyl theropod tracks, the latter tentatively be attributed to swimming activity. The combination of possible swim and walking trackways suggest that they were formed at different times and in different environments. This is the first Lower Cretaceous tracksite reported from Heilongjiang Province with the exception of an historic record of a large pentadactyl track of probable thyreophoran (ankylosaurian) affinity. Ankylosaurian tracks are rare in China, and reported tentatively from only one other location. The dinosaur ichnofauna from the Taoqihe Formation is similar in composition to the skeletal assemblages of the Early Cretaceous Jehol Biota in the nearby Liaoning Province. The new track records are important for better understanding the palaeobiogeography and faunal developments of northeastern China and adjacent Russia.

Revisiting the age and palaeoenvironments of the Upper Jurassic–Lower Cretaceous? dinosaur-bearing sedimentary record of eastern Spain: implications for Iberian palaeogeography

An integrated stratigraphic, palaeontological, palaeoenvironmental and palaeogeographical study of the traditionally considered Upper Jurassic–Lower Cretaceous dinosaur-bearing sedimentary record (DSR) of eastern Spain is accomplished for the first time. Several areas where dinosaur fossils are abundant (western Maestrazgo and South-Iberian basins) have been studied in detail. In all the areas, the DSR comprises a carbonate-dominated lower part (CLP), and an essentially siliciclastic upper part (SUP). Deposition occurred in a shallow-very shallow marine carbonate platform, laterally connected towards the N and W to coastal and alluvial environments. The overall upwards evolution is regressive with a transgresive episode at the uppermost part. The DSR includes deposits previously assigned, depending on the studied area, from the Kimmeridgian to the Barremian (locally even to the Aptian–Albian). However, ages obtained in this work from larger benthic foraminifera (LBF), demonstrate a Kimmeridgian–Tithonian age (locally Kimmeridgian-Early Berriasian?) for the DSR. These findings have important implications regarding the age of dinosaur fossils of these deposits, traditionally assigned to the Jurassic-Cretaceous transition, or even to the Early Cretaceous, erroneously, and have necessitated a deep litho- and chronostratigraphic revision of the units previously established in the studied areas: new data indicate that the DSR is correlatable with deposits of the Villar del Arzobispo Fm and that the usage of the Aldea de Cortes and El Collado Fms, traditionally assigned to the Early Cretaceous, should be avoided. New data also reveal that the DSR should be correlated with other Kimmeridgian–Tithonian dinosaur-bearing deposits of Iberia, such as those of the Cameros Basin, Asturias and Portugal, and have encouraged a revision of the Iberian palaeogeography at that time. In fact, ages obtained from LBF agree with data provided by the systematics of dinosaurs, since dinosaur faunas of eastern Spain are similar to those of the other Late Jurassic Iberian areas, especially to those of the Lusitanian Basin.

Biochronology, paleoenvironments, and stratigraphic sequences of the late Albian–middle Eocene fore-arc Vizcaino basin, western Baja California, Mexico

The Vizcaino fore-arc basin accumulated approximately 4 km (∼13,000 ft) of upper Albian–middle Eocene siliciclastic marine sedimentary rocks derived from the Peninsular Ranges in Baja California. Data from eight exploratory wells document the micropaleontological content and lithological characteristics of these rocks. The strata studied represent mostly neritic–upper bathyal marine environments and overlie a basement composed of Cretaceous granitic rocks, or Aptian–Albian volcaniclastic sedimentary rocks correlative with the Alisitos Formation. We recognize four major depositional sequences within the basin that are related to the regional geology. The basal Albian–Turonian sequence 1 represents the initiation of fore-arc basin sedimentation, contains continental conglomerates that change to bathyal shales, and correlates with the lower part of the Valle Group of the Vizcaino Peninsula. Sequence 2 is Coniacian–Paleocene, includes basal conglomeratic sandstones grading into Maastrichtian bathyal shales, and usually overlies a Coniacian–Santonian unconformity. Sequence 2 is represented at the surface by the Rosario Group in northwestern Baja California and the upper part of the Valle Group in the Vizcaino Peninsula. Sequence 3 is Paleocene–middle Eocene, represents continuity of fore-arc sedimentation in neritic–upper bathyal conditions, is capped by a major unconformity, and correlates with the Sepultura and Bateque Formations to the north and south of the basin, respectively. The uppermost Miocene–Pliocene sequence 4 is composed of marine sandstone–siltstone unconformably overlying sequence 3 and is correlative with the Tortugas Formation that represents sedimentation after the end of subduction of the Farallon plate beneath the North America plate.

Comparative Analysis of Aptian–Albian Rocks of the Kema and Kiselevka–Manoma Terranes: Geochemistry, Geochronology, and Paleomagnetism

The results of comprehensive (geological, geochemical, geochronological, and petro- and paleomagnetic) study of the Aptian–Albian rocks of the Kema Terrane and the northeastern Udyl segment of the Kiselevka–Manoma Terrane are presented. The obtained results suggest that the studied volcanogenic–terrigenous complexes of rocks formed in a suprasubduction zone at about the same time (early Albian, 110 Ma ago) at close latitudes but in different island arcs unequally distant from the continent: the complexes of the Kema Terrane at a latitude of 36° ± 6° N in the island arc close to the continent as evidenced by the petro–geochemical characteristics of the volcanites and the presence of ancient zircons in the sediments; and the rocks of the Udyl segment of the Kiselevka–Manoma Terrane at a latitude of 33° ± 5° N in an intraoceanic island arc separated from the volcanic arc of the Kema terrane by an interarc basin, which was wide and deep enough to avoid the influence of the continental source areas in the sediment accumulation zone of the Kiselevka–Manoma Terrane. Based on the conclusions, the geodynamic reconstruction is developed for the formation and history of motions of the studied rock complexes during the oceanic plate movement, their displacement along the transform margin, as well as post-accretionary movements at various distances to the current position with the following coordinates: Udyl 52° N, 140° E; Kema 45°–46° N, 136°–137° E.

Aptian–early Albian sedimentation in the Essaouira-Agadir basin, Western Morocco

Aptian to early Albian times were marked by various geodynamic and paleoenvironmental events such as large igneous province volcanism, perturbations of climate and the carbon cycle, and sea-level changes. The Essaouira-Agadir basin (EAB), located on the Atlantic passive margin of Morocco, offers good and fossiliferous exposures of the Aptian–Albian sedimentary series. A detailed analysis of this succession made it possible to establish a biostratigraphic framework. The identification of discontinuities allowed to define eight depositional sequences. As most of them are correlatable with depositional sequences of other Tethyan areas, they suggest that eustacy was the main parameter controlling sedimentation. The analysis of sedimentary facies and nannofossil assemblages provides information on paleoenvironmental changes.Sedimentation in the EAB evolved from a very low energy, carbonate ramp in the early Aptian to a low energy, slightly deeper, mixed carbonate-clastic ramp in the early Albian. This change occurred along with an increase of clastic input, a change from oligotrophic to mesotrophic faunal assemblages, and a decrease of sea-surface temperatures. The occurrence of current sedimentary features, sporadic dysaerobic deposits and local phosphatic and glauconitic crusts suggests that upwelling currents were significant during this period.Paleogeographic and isopach maps support a transgressive trend in the late Aptian and early Albian, and unravel subsidence anomalies suggesting mild halokinetic movements during Aptian‒early Albian times.

Postcollisional granitoids and aptian-albian extension in tectonic evolution of Chukotka mesozoides, Northeast Russia

New U–Pb SIMS zircon datings from granitoid plutons and dikes of Western Chukotka together with earlier obtained data confirm that postcollisional granitoid magmatism and dike intrusion occurred in Aptian–Albian (117–105 m.y.) and fix change of tectonic regime from collision to extension in tectonic evolution of Chukotka Mesozoides. These events may be related to continuing expansion of Amerasian basin since Jurassic and forma- tion in Aptian—Albian time of both oceanic Makarov, Podvodnikov basins and Anakhurgen, Nutesyn and Kameshkov basins in continental framework of Eastern Arctic. Synchronism of tectonic events of extension and spreading in the Canada Basin and collisional events, deformations and reorganization of structural style and sedimentary environment in the South-Anyui suture is noted. This may be regarded as confirmation of rotation hypothesis of Amerasian Basin formation.

Chronostratigraphic Revision of the Cloverly Formation (Lower Cretaceous, Western Interior, USA)

The Cloverly Formation is an important geologic unit for understanding the development of North American terrestrial landscapes and ecosystems, but the age of this unit is poorly constrained. We report U–Pb radiometric dates determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and chemical abrasion thermal ionization mass spectrometry (CA-TIMS) from euhedral zircons derived from fluvial sandstone and bentonitic claystone. We reanalyzed published biostratigraphic, paleomagnetic, and radiometric datasets, which have generally disregarded younger (late Albian–Cenomanian) ages for the formation. New data reported in this study suggest that deposition of the Cloverly Formation spanned the Valanginian–Cenomanian stages (ca. 140 Ma–98 Ma), a longer time interval than the commonly cited Aptian–Albian depositional timeframe. The lowest member of the Cloverly Formation, the Pryor Conglomerate, was deposited ca. 140–130 Ma in response to the onset of the Sevier Orogeny shedding sediment from the west. The overlying Little Sheep Mudstone Member was deposited ca. 124–109 Ma in a time of low sediment supply. In the mid–late Albian to early Cenomanian (ca. 109–98 Ma), sediment sourced from the east was deposited as the Himes Member and Greybull Sandstone. Following this, the Sykes Mountain Formation began nearshore deposition as the Western Interior Seaway transgressed from the north. Our revised chronostratigraphic framework for the Cloverly Formation is congruent with tectonic subsidence analysis showing a rapid increase in accommodation space in the mid-Albian. We hypothesize that more intensive sampling may yield multiple fossil assemblages within the formation, paralleling its correlates to the south. Furthermore, we hypothesize that some poorly represented taxa will be synonymized with taxa from those same units now that their temporal equivalence has been demonstrated.

Seismic stratigraphy and hydrocarbon prospectivity of the Aptian–Albian succession along the Oued Bahloul Basin, Central Ouest Tunisia

The Aptian–Albian sediments deposited along the Tunisian Atlas and, overlain by the Vraconian seals constitute an attractive hydrocarbon play in the Oued Bahloul Basin of the Central Tunisia. Albian organic-rich shale unconformably underlies the Aptian dolomites and plays as a major source rock proven by oil and gas discovered so far with the Aptian reservoir layers. In central Tunisia, many wells have proven the Aptian–Albian play in structural traps, with an oil discovery in central onshore and offshore Tunisia. In order to document and map the reservoir distribution and stratigraphic-trap fairway, the Aptian–Albian sedimentary package is divided into a number of depositional sequences and systems tracts using key regional seismic lines calibrated with boreholes. Tracing of the key surfaces bounding the Aptian–Albian has been carried out using all the seismic lines provided from Tunisian Company of Petroleum Activities (ETAP). The interpretation of 2D seismic lines can allow for the reconstruction of 3D structural elements to reduce potential risk prior to exploratory drilling. Relative sea-level fluctuations and rejuvenation of major faults significantly influenced the Aptian–Albian depositional system creating regional unconformities and influencing the evolution of accommodation space. Although the development of the seismic sequences is partially influenced by local tectonics, the overall stacking pattern of the Aptian–Albian sedimentary strata displays seven third-order cycles and two second-order cycle, which is in harmony with the eustatic sea level chart. In this work, the facies analysis using sequence stratigraphy and seismic sedimentology offer useful insight to Aptian hydrocarbon exploration in Oued Bahloul Basin and other analogous basins and can contribute in the exploration and reservoir development.

Diversity and homologies of corystosperm seed-bearing structures from the Early Cretaceous of Mongolia

New discoveries of corystosperm seed-bearing structures from the Tevshiin Govi locality, Mongolia, which is of Early Cretaceous (Aptian–Albian) age, show that the individual seed-bearing units of Umkomasia mongolica were borne in a cone, as also documented for the very similar reproductive units of Doylea tetrahedrasperma. New material from the Tevshiin Govi locality also documents two additional species of Umkomasia – U. corniculata sp. nov. and U. trilobata sp. nov. – that most likely grew in a different environment to U. mongolica. The occurrence of three different Umkomasia species in the Early Cretaceous of Mongolia, together with other records from the Early Cretaceous of the Northern Hemisphere, indicate that previous concepts of corystosperms, based mainly on material from the Southern Hemisphere, need to be revised. The consistent reproductive architecture of the seed-bearing structures in all three corystosperm species, with a bract subtending a variously modified axis bearing ovules, is similar to the situation in Ginkgo and conifers. These underappreciated architectural commonalities among the reproductive structures of major groups of seed plants are likely significant for a deeper understanding of seed plant evolution and require further exploration.

Roles of Postcollisional Granitoids and Aptian–Albian Extension in Tectonic Evolution of Mesozoic Structures on Chukchi Peninsula, Northeastern Russia

New U–Pb SIMS zircon datings from granitoid plutons and dikes of Western Chukotka, together with data obtained earlier, confirm that postcollisional granitoid magmatism and dike intrusion occurred in the Aptian–Albian (117–105 Ma ago) and marked a change in the tectonic regime during tectonic evolution of Chukotka Mesozoides from collision to extension. These events might be related to the opening of the Amerasian Basin, which had begun in the Jurassic, and to the formation (in the Aptian–Albian time) of the Makarov and Podvodnikov oceanic basins, as well as the Anakhurgen, Nutesyn, and Kameshkov basins in the continental framework of the Eastern Arctic. The synchronicity of the tectonic extension and spreading events in the Canada Basin, on the one hand, and collisional events, deformations, and reorganization of structural style and sedimentary environment in the South Anyui suture, on the other hand, is noted. This may be regarded as confirmation of the rotation hypothesis of formation of the Amerasian Basin.

Lizards of the Families Eoxantidae, Ardeosauridae, Globauridae, and Paramacellodidae (Scincomorpha) from the Aptian–Albian of Mongolia

Classification of lizards of the infraorder Scincomorpha is discussed in the paper. The history and problems of studying Eoxantidae, Ardeosauridae, Globauridae, and Paramacellodidae fossil families from this infraorder are presented in more detail. New species from the Aptian–Albian deposits of Mongolia have been added to the lizard families listed above.

Seismogeological Criteria for the Gas Potential of Aptian–Cenomanian Sediments in the North of West Siberia (by the Example of the Yubileinoe Field)1

Abstract —Seismogeological criteria for the gas potential of the Aptian–Cenomanian sediments of West Siberia are substantiated. The research was carried out by the method of integrated interpretation of seismic materials, well logs, well test results, and petrophysical studies. As a reference object we used the Yubileinoe oil and gas condensate field located in the Nadym–Pur interfluve, in which a unique gas deposit is concentrated in the Cenomanian reservoir PK1 and the Albian sand bed PK18. Based on the research results, seismogeologic criteria for gas prediction have been formulated. Massive Cenomanian gas pools are displayed in wave seismic fields by: (1) the presence of reflectors formed at the gas–water contacts in time sections and a decrease in the amplitude parameters of the reflector G confined to the roof of Cenomanian sequence; (2) an increase in the time thickness (ΔT), a decrease in the interval velocities (Vint), and a decrease in the amplitude–energy parameters of the seismic record in the Aptian–Cenomanian sequence. Aptian–Albian sheet gas pools are displayed in the wave fields by a sharp increase in the amplitudes of the seismic record, forming “bright spot” anomalies in the time sections.

Historical and Geological Modeling of the Processes of Hydrocarbon Generation in the Hettangian–Aalenian Deposits of the Ust’-Tym Megadepression1

Abstract —Analysis of the geologic structure of the Hettangian–Aalenian deposits of the Ust’-Tym megadepression was carried out. The history of the formation of traps in the Hettangian–Aalenian complex has been reconstructed on the basis of a comprehensive interpretation of seismic materials and deep-drilling data. The oil and gas potential has been estimated. The time of the subsidence of the Togur Formation into the oil window has been determined, and the history of the generation of liquid hydrocarbons (HC) by the organic matter (OM) of the Togur Formation has been reconstructed. The Lower Jurassic and Aalenian deposits overlap the rocks of the pre-Jurassic basement with disagreement and are distributed almost over the entire study area. The complete section of the Hettangian–Aalenian deposits is in the most submerged parts of the territory. The section includes the Urman, Togur, and Salat/Peshkov Formations and the lower Tyumen Subformation. Three oil and gas subcomplexes—Hettangian–Early Toarcian (U16–17), Toarcian–Aalenian (U15), and Aalenian (U11–14) — are distinguished within the Hettangian–Aalenian sediments. Closed positive structures that can serve as hydrocarbon traps have been identified in each of the subcomplexes. Positive structures developed in the Jurassic, Berriasian–Early Aptian, and Aptian–Albian–Turonian time were inherited and finally formed at the post-Turonian stage only. The authors carried out a quantitative assessment of the total oil resources of the D0 category for all promising objects, taking into account the success rate. The heterogeneous organic matter of the Togur Formation is the main source of hydrocarbons in the Hettangian–Aalenian complex. The Togur Formation began to enter the oil window (OW) about 115–110 Ma and fully entered it about 5 Ma. The escape of rocks from the zone of the oil window began about 48 Ma and still continues. The history of the generation of liquid hydrocarbons by the organic matter of the Togur Formation has been reconstructed for types II and III of kerogen. For type II, the generation began about 94 Ma, at the beginning of the Late Cretaceous (Cenomanian), and for type III, it began in Turonian time (89.8 Ma). The most significant volumes of liquid HC were generated in the last 5 Myr. Potential hydrocarbon traps existed throughout the generation process, which allowed accumulation of the generated hydrocarbons in the Hettangian–Aalenian complex. Comparison of the estimated oil resources of the D0 category in the traps of the Hettangian–Aalenian complex with the volumes of generated hydrocarbons leads to the conclusion that the traps might have been filled. The results obtained in the course of the study suggest that the Hettangian–Aalenian complex is oil- and gas-promising and the Togur Formation is the main source of hydrocarbons.

Postcranial morphology of the basal neoceratopsian (Ornithischia: Ceratopsia) Auroraceratops rugosus from the Early Cretaceous (Aptian–Albian) of northwestern Gansu Province, China

The species Auroraceratops rugosus was originally described based upon a single skull. With the recovery of over 80 individuals, a complete description of the postcranial skeleton is presented. Auroraceratops is currently the most complete exemplar we have of ceratopsian postcranial anatomy between Psittacosaurus and Leptoceratops. Adult Auroraceratops had a length of approximately 125 cm and an approximate hip height of 44 cm. Osteological correlates of stance in the fore- and hind limb unequivocally indicate a bipedal gait. The phylogenetically corrected quadrupedal mass-estimation equation modified for mass estimation of bipedal terrestrial vertebrates estimates an average mass of Auroraceratops at 15.5 kg. It has the phylogenetically and temporally earliest documentation of the syncervical in Ceratopsia. The mid-caudal neural spines are elongate and erect, a feature previously only known in Leptoceratopsidae and Protoceratopsidae. Despite being longer than in most ceratopsians, the mid-caudal neural spines are not as tall as in some leptoceratopsids. Most of the phylogenetically relevant characters of the postcranial skeleton in Auroraceratops are a mosaic of features plesiomorphic to Neoceratopsia and features previously considered to be unique to later diverging clades, such as Leptoceratopsidae and Protoceratopsidae.Citation for this article: Morschhauser, E. M., H. You, D. Li, and P. Dodson. 2019. Postcranial morphology of the basal neoceratopsian (Ornithischia: Ceratopsia) Auroraceratops rugosus from the Early Cretaceous (Aptian–Albian) of northwestern Gansu Province, China; pp. 75–116 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1524383.

A new genus and species of Solenoceridae (Crustacea, Decapoda, Dendrobranchiata) from the Cretaceous (Aptian/Albian) of the Araripe Sedimentary Basin, Brazil.

The first fossil Solenoceridae found from the Cretaceous (Aptian-Albian) is described in the Araripe Sedimentary basin, Priorhyncha feitosai n. gen. n. sp. The material was collected in the strata of the Romualdo Formation, municipality of Trindade, Pernambuco. Characters that permit placement of the new species in Solenoceridae are: a short, dorsally serrated rostrum; a marked cervical groove; and the presence of an antennal spine. Those characters are also diagnostic for Priorhyncha feitosai n. gen. n. sp. when compared to the other Dendrobranchiata shrimp described from this basin.

First Record of Stegosaur (Ornithischia, Dinosauria) from the Aptian–Albian of Mongolia

The first Mongolian stegosaur, Mongolostegus exspectabilis gen. et sp. nov., Stegosauridae (Ornithischia), represented by a series of anterior caudal vertebrae and bones of the pelvic girdle is described. The vertebral structure and massiveness and morphological features of pubic bones provide a unique combination of features, allowing recognition of diagnostic characters. The new taxon comes from the Aptian–Albian deposits of the Khamryn-Us locality (Mongolia) and belongs to the latest Stegosauridae (Ornithschia).