Evidence of a Hopping, Bipedal Mammaliform From Cretaceous Korea

Korean trackway of a hopping, mammaliform trackmaker is global first from the Cretaceous

Authors:

Kim et al

Abstract:

A trackway of a small hopping mammaliform trackmaker from the Jinju Formation (Lower Cretaceous) of the Jinju City area, Korea, is the first of this type reported from the Mesozoic of Asia, and globally. The animal left a narrow trackway (∼20 mm wide) with small tetradactyl footprints averaging less than 10 mm in diameter. Only two footprints registered with each hop (mean length 41 mm) thus indicating a bipedal gait. All trackway evidence suggests a small “mouse-like” trackmaker. Previous reports of trackways made by hopping tetrapods from the Mesozoic are rare and presently restricted to ichnogenus Ameghinichnus isp. indet., from the Jurassic of Argentina. Ichnogenus Musaltipes from the Cenozoic of North America, is the only other ichnogenus representing a hopping mammal. The Korean specimen here named Koreasaltipes jinjuensis, is different from these aforementioned ichnogenera in digit count, digit proportion and trackway configuration, as well as lack of tail trace. Koreasaltipes jinjuensis is from a lake shore paleoenvironment associated with nematode tracks (Cochlichnus isp.), other small tetrapod tracks attributed to avian theropods (birds), pterosaurs and crocodylomorphs, as well as larger saurischian dinosaurs.

Anebodon luoi: a new Trechnotherian Symmetrodont From Lower Cretaceous China

A new symmetrodont mammal (Trechnotheria: Zhangheotheriidae) from the Early Cretaceous of China and trechnotherian character evolution

Authors:

Bi et al

Abstract:

We report the discovery of Anebodon luoi, a new genus and species of zhangheotheriid symmetrodont mammal from the Lujiatun site of the Lower Cretaceous Yixian Formation, China. The fossil is represented by an associated partial skull and dentaries with a nearly complete dentition, and with a dental formula of I4/3 C1/1 P5/4 M3/4. This new taxon lacks the high molar count typical of derived symmetrodonts, differing from the well-represented zhangheotheriids Zhangheotherium and Maotherium in having a postcanine dental formula that resembles more primitive tinodontid symmetrodonts on the one hand, and sister taxa to therians such as Peramus on the other. Upper and lower distal premolars are strongly molariform and are captured undergoing replacement, clarifying positional homology among related taxa. We also describe the rostrum and, for the first time in a symmetrodont, much of the orbital mosaic. Importantly, our new taxon occupies a basal position within the Zhangheotheriidae and permits discussion of trechnotherian character evolution, ultimately shedding additional light on the evolution of therians.

Very Diverse Dinosaur Trackway has Ornithopod and Pterosaur Traces Amongst Lots of Theropod and Sauropods Tracks

A diverse saurischian (theropod–sauropod) dominated footprint assemblage from the Lower Cretaceous Jiaguan Formation in the Sichuan Basin, southwestern China: A new ornithischian ichnotaxon, pterosaur tracks and an unusual sauropod walking pattern

Authors:

Xing et al

Abstract:

A sample of fallen blocks of fluvial sandstone from the Lower Cretaceous Jiaguan Formation of Sichuan Province yielded an assemblage of dinosaur and pterosaur tracks preserved as natural impressions and casts. Collectively the assemblage reveals 132 tracks representing at least 30 trackways of tridactyl and didactyl theropods, sauropods, ornithopods and pterosaurs. Ichnotaxonomically, the trackways of small tridactyl theropods (pes lengths 7–18 cm) are indeterminable, whereas the trackway of a small didactyl dromaeosaur (pes length up to 7.5 cm) is tentatively assigned to cf. Velociraptorichnus. The sauropod trackways are assigned to cf. Brontopodus based on the medium to nearly wide-gauge pattern. Other characteristics are the U-shaped manus and strong heteropody. One sauropod trackway shows a peculiar pattern with a lack of left manus imprints, and an unusual position and rotation of right manus imprints. Different scenarios and explanations for this phenomenon are discussed. Ornithopod trackways are the most abundant in the sample and characterized by pes imprints of a small biped that are assigned here to the new ichnospecies Caririchnium liucixini. It is characterized by an unusual broad shape and weak mesaxony. Bivariate analysis of different Caririchnium ichnospecies reveals increasing mesaxony toward the larger forms, a trend that is the reverse of typical theropod ichnotaxa, where large imprints have weak mesaxony. Three isolated, small pterosaur tracks (two manus, one pes) are visible on a single surface. They show strong similarities to the widespread ichnogenus Pteraichnus. This is the ninth report of tetrapod tracks from the Jiaguan Formation in recent years and represents one of the most diverse assemblages recorded to date. It is also rare evidence of typical didactyl dromaeosaur tracks and the co-occurrence of sauropod and ornithopod tracks in a fluvial depositional environment representing arid climate conditions.
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Did a Magma Injection Into Organic Sediments at the Barremian/Aptian Boundary Release Carbon Gases, Trigger Oceanic Anoxic Event 1a?

The Early Cretaceous Barents Sea Sill Complex: Distribution, 40Ar/39Ar geochronology, and implications for carbon gas formation

Authors:

Ploteau et al

Abstract:

Mafic igneous rocks of Cretaceous age (80–130 Ma) scattered around the Arctic Ocean are commonly referred to as the High Arctic Large Igneous Province (HALIP). We have mapped out the distribution of HALIP igneous rocks in the Barents Sea region over the past decade based on integrated seismic–gravity–magnetic interpretation, field work, review of publications, and analyses of new and vintage borehole and field samples. The mapping reveals abundant igneous rocks in the northern and eastern Barents Sea covering an area of ~ 900,000 km2 with a conservative volume estimate of 100,000 to 200,000 km3 of intrusions. The igneous province is dominated by sheet intrusions injected into Triassic and Permian sedimentary rocks. Hydrothermal vent complexes are rare, and only two potential vent complexes have been identified on seismic data in the eastern Barents Sea. We have further done extensive radiometric dating of the igneous samples in the Barents Sea region. New 40Ar/39Ar dating of thirteen samples from Svalbard reveal ages of crystallization and alteration. The large age span (60–140 Ma for the raw ages) is likely due to partial or complete overprint of the K/Ar system in plagioclase, and the age of the magma emplacement is better represented by U/Pb TIMS ages. Only one of our 40Ar/39Ar analyses of plagioclase yielded a statistically valid age that is in line with the recently published U/Pb TIMS ages of 122–125 Ma. The new data clearly document that relying on published data from the K/Ar system can lead to erroneous conclusions on the age of crystallization in this province without a careful use of additional 40Ar/39Ar degassing data (i.e., K/Ca). We propose that the magmatism on Svalbard and Franz Josef Land represents a distinct magmatic event near the Barremian/Aptian boundary (125 Ma) in the Barents Sea. This Early Cretaceous Barents Sea magmatism resulted in the formation of the BSSC (Barents Sea Sill Complex). BSSC age rocks are also present in Arctic Canada (Sverdrup Basin) and on Bennett Island (New Siberia Islands). The massive injection of hot magma into potentially organic-rich sediments in the eastern and northern Barents Basin caused rapid organic matter maturation and formation of thermogenic gas and oil in contact aureoles. We estimate that up to 20,000 Gt of carbon were potentially mobilized, corresponding to 175 trillion barrels of oil equivalent. The production rates and fate of the carbon gases are uncertain. However, we speculate that rapid release of aureole greenhouse gases (methane) may have triggered the Oceanic Anoxic Event 1a (OAE1a) and the associated negative δ13C excursion in the Early Aptian. Some of the methane may also be trapped in the vast hydrocarbon gas accumulations found in the east Barents Basin.

Triconodont and Multituberculate Mammals Found in Lower Cretaceous Japan

New mammalian specimens from the Lower Cretaceous Kitadani Formation, Tetori Group, Fukui, Japan

Authors:

Miyata et al

Abstract:

New specimens of two non-therian (non-tribosphenidan) mammals are described from the Lower Cretaceous Kitadani Formation in the upper part of the Tetori Group, Katsuyama, Fukui Prefecture, Japan. Despite their poor preservation, these specimens represent undescribed species from Japan, suggesting additional mammalian diversity in the Tetori Group. Previously, four mammal taxa had been formally described from this rock unit: a spalacotheriid ‘symmetrodont’, two eobaatarid multituberculates and a eutriconodont mammal. One of the new specimens is a damaged left p4 of a ‘plagiaulacidan’ grade multituberculate assignable to the family Eobaataridae. The Kitadani eobaatarid is a large species distinguished from the two previously described eobaatarids, Tedoribaatar and Hakusanobaatar, which are known from the stratigraphically lower Kuwajima Formation of the Tetori Group, Hakusan, Ishikawa Prefecture, Japan. It also differs from Sinobaatar, Heishanobaatar and Liaobaatar described from the Early Cretaceous of China. Another specimen, a partial right dentary with a faint Meckelian groove, is assigned to a eutriconodontan that is larger than and morphologically distinguishable from the eutriconodont Hakusanodon from the Kuwajima Formation. The Kitadani eutriconodontan is potentially related to the family Triconodontidae. The additional specimens from the Kitadani Formation shed new light on Early Cretaceous mammalian faunal change and dispersal in East Asia.

Two new Mammal Localities From Lower Cretaceous Siberia

Two new mammal localities within the Lower Cretaceous Ilek Formation of West Siberia, Russia

Authors:

Averianov et al

Abstract:

Two new mammal localities have been discovered in the Lower Cretaceous Ilek Formation of West Siberia, Russia, during a field work in 2014. The Smolenskii Yar locality in the Chebula District of Kemerovo Province produced an upper molariform tooth (M2) of a Gobiconodontidae indet. The Ust’-Kolba locality in the Tisul’ District of Kemerovo Province yielded a lower molar (m2) of the zhangheotherian Kiyatherium sp. These are the ninth and tenth Mesozoic mammal localities for Russia. The Kiyatherium-bearing vertebrate assemblage from the Shestakovo 3 and Ust’-Kolba localities is likely to be the youngest within the Ilek Formation, reflecting the time after the extinction of the Tritylodontidae.

An Unique Mammalian Assemblage From Early Cretaceous Siberia

Mammal remains from the Lower Cretaceous Bol'shoi Terekhtyul' locality in West Siberia, Russia

Authors:

Averianov et al

Abstract:

Four mammalian taxa have been identified based on upper molariform tooth and edentulous dentary fragments from the Bol'shoi Terekhtyul' locality of the Lower Cretaceous Ilek Formation (Krasnoyarsk Territory, Russia): Docodonta indet., Amphidontidae indet., Zhangheotheria indet. sp. A and sp. B. The docodontan from Bol'shoi Terekhtyul is smaller than Sibirotherium rossicum from the Ilek Formation at Shestakovo 1 locality (Kemerovo Province, Russia) and may belong to a distinct taxon. It is one of the younger docodontans in the fossil record. The mammal assemblage from the Bol'shoi Terekhtyul' locality is drastically different from the mammal assemblage of nearby localities of the Ilek Formation along Bol'shoi Kemchug River, which consists of Gobiconodontidae and Amphilestidae. The reason for this faunal discrepancy is unclear for the moment.

How the Early Cretaceous Jehol Lagerstatte Fossilized

A MODEL FOR ORGANIC FOSSILIZATION OF THE EARLY CRETACEOUS JEHOL LAGERSTÄTTE BASED ON THE TAPHONOMY OF “EPHEMEROPSIS TRISETALIS”

Authors:

Pan et al

Abstract:

The taphonomic pathways of “Ephemeropsis trisetalis” nymphs (mayfly larvae) were systematically investigated based on fossils of different preservational types, collected during three high–stratigraphic-resolution (mm to cm) excavations in the Lower Cretaceous Yixian Formation in the Sihetun area of western Liaoning, China. All fossils studied are fully articulated either in three or two dimensions, which indicates that decay was terminated at a stage before the exoskeleton became disarticulated. We conclude that the Jehol organic skeletons represent at least two general types of preservation produced by pyritization and collapse/compression, respectively. The two-dimensional compressions show no evidence for authigenic minerals, but the three-dimensionally preserved fossils are wholly or partially pyritized. Our study also indicates that aluminosilicate clay and pyrite mineralization are closely associated with fossil “Ephemeropsis trisetalis” nymphs, suggesting that both clay and pyrite played important roles in lacustrine fossil preservations, as in some marine fossil Lagerstätten. We propose a general model for organic tissue fossilization in the Jehol Lagerstätte based on study of taphonomy of “Ephemeropsis trisetalis” nymphs.

Jeholornis curvipes: a new Cursorial, Nonperching, and Seed-eating Bird From Lower Cretaceous Jehol Biota

A new long-tailed basal bird from the Lower Cretaceous of north-eastern China

Authors:

Lefèvre et al

Abstract:

A new basal Avialae, Jeholornis curvipes sp. nov., from the Yixian Formation (Lower Cretaceous) of Liaoning Province (north-eastern China) is described. A revision of long-tailed birds from China and a phylogenetic analysis of basal Avialae suggest that Jeholornithiformes were paraphyletic, with Jixiangornis orientalis being the sister-taxon of pygostylia. The phylogenetic analysis also recovered that the tail reduction is a unique event in the evolution of birds. Jeholornis species were cursorial, nonperching, and seed-eating birds.

The PaleoEcology of the Lower Cretaceous Jehol Biota

The Early Cretaceous terrestrial ecosystems of the Jehol Biota based on food-web and energy-flow models

Authors:

Matsukawa et al

Abstract:

The ancient terrestrial ecosystems of the Lower Cretaceous Yixian Formation and the Jiufotang Formation, consecutive components of the Jehol Group in Northeast China were reconstructed using an energy-flow and food-web model. This model can be used to quantitatively estimate population densities for ancient terrestrial vertebrates based on food webs, net primary productivity, and three categories of energy-transfer efficiency. The results indicate that densities reached 866 individuals km−2 and 4122 individuals km−2 in two ecosystems, respectively. The main component of the vertebrate fauna of the Yixian Formation consisted of large herbivorous dinosaurs, while much smaller avians dominated the Jiufotang fauna. The model also indicates a temporal transition in the dinosaur fauna from the Yixian fauna to the Jiufotang fauna in which theropods decreased and ceratopsids became more abundant. We then compared these estimates of biodiversity with the Early Cretaceous Choyr fauna of Mongolia, and Tetori fauna of Japan using Simpson's diversity indices. Those indices, based on biomass, indicate that the biodiversities of the Jehol fauna lay between those of the Choyr and Tetori faunas. This range in biodiversity seems attributable to fundamental differences in vegetation and the environment.

Grabauornis lingyuanensis: a new Early Cretaceous Enantiornithe From China

A New Enantiornithes (Aves) from the Early Cretaceous of China

Authors

Dalsatt et al

Abstract:

A new bird from the early Cretaceous Yixian Formation of Liaoning, China is described. This new species, Grabauornis lingyuanensis, shares several synapomorphies with the Enantiornithes. The specimen is relatively well preserved. The skeletal morphology of Grabauornis bears close resemblance to that of other Chinese members of this clade. The brachial index (the ratio between the lengths of humerus and ulna) is 0.95, which is close to the average for enantiornithine birds. It indicates that Grabauornis was a rather good flyer, and the presence of an alula in the wing further testifies to this.

Datanglong guangxiensis: a new Carcharodontosaur Theropod From Lower Cretaceous China

A New Carcharodontosauria (Theropoda) from the Early Cretaceous of Guangxi, Southern China

Authors:

Mo et al

Abstract:

A new large-bodied theropod dinosaur, Datanglong guangxiensis gen. et sp. nov., was recovered from the Lower Cretaceous Xinlong Formation of the Datang Basin, Guangxi. It is unique in several features including: posteriormost dorsal vertebra with teardrop-shaped pneumatic foramen confined by enlarged pcdl, acpl and the centrum; posteriormost dorsal with well-developed, horizontal prpl; posteriormost dorsal with a parapophysis projecting more laterally than the diapophysis; brevis fossa shallow with short, ridge-like medial blade; and iliac pubic peduncle with posteroventrally expanded margin. Cladistic analysis supports the idea that this new taxon Datanglong guangxiensis is a primitive member of the Carcharodontosauria in possessing two unambiguous synapomorphies: large external pneumatic foramina and internal spaces present in the lateral surface of ilium, and a peg-and-socket ischiac articulation with the ilium. The presence of the new taxon from Guangxi further confirms that Carcharodontosauria were cosmopolitan large-bodied predators during the Early-mid Cretaceous.

Tianyunornis cheni: a new Hongshanornithid Ornithuromorph Bird From Lower Cretaceous China

New Information on Hongshanornithidae (Aves: Ornithuromorpha) from a new subadult specimen

Authors:

Zheng et al

Abstract:

We report a new species of basal ornithuromorph bird, Tianyunornis cheni gen et sp nov, based on a nearly complete and articulatd subadult individual from Lower Cretaceous Yixian Formation in the eastern region Nei Mongol, China. The new specimen shws Characeristic of the Hongshanornithidae (Hongshanornis longicreta, Longicrusavis houi, and Parahongshanornis chaoyanensis_, such as a small body size and elongate hindlimbs relative to their forelimbs, but it also possess some unique features that support the erection of a new genus and species, including a stright dentary (a simoidal dentary was previously considered an autapomorphy of hongshanornithids), teeth preserved on both the upper and lower jaws, sternal caudolateral trabecula has a distinct fan-shaped expended distal end. With the addition of this new taxon, Hongshanornithidae represents the most diverse recoginuzed clade of Early Cretaceous orinthuromorphs. The new specimen reveals new important morphological information regarding the Hongshanornithidae and confirms the controversial presence of teeth in this clade.

Zhouornis hani: a new Lower Cretaceous Enantiornithine Bird

New information on the anatomy of the Chinese Early Cretaceous Bohaiornithidae (Aves: Enantiornithes) from a subadult specimen of Zhouornis hani

Authors:

Zhang et al

Abstract:

Enantiornithines are the most diverse avian clade in the Cretaceous. However, morphological specializations indicative of specific ecological roles are not well known for this clade. Here we report on an exquisitely well-preserved specimen from the Lower Cretaceous Jehol Group of northeastern China, which pedal morphology is suggestive of a unique ecological specialization within Enantiornithes. The morphology of the new specimen is largely indistinguishable from that of the holotype of the bohaiornithid enantiornithine Zhouornis hani, albeit the latter is somewhat larger. The new specimen provides important and previously unknown details of the skull of Zhouornis hani, which add to the limited knowledge about the cranial anatomy and evolution of enantiornithines. The information offered by the new specimen also augments our understanding of the postcranial morphology of bohaiornithid enantiornithines, a clade that has been only recently recognized. With the description of this specimen, Zhouornis hani becomes one of the most anatomically complete known enantiornithine species, which will facilitate future morphological studies.

Leikupal laticauda: a First and Relic Diplodocid Sauropod From Early Cretaceous Argentina

A Diplodocid Sauropod Survivor from the Early Cretaceous of South America

Authors:

Gallina et al

Abstract:

Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation) of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere.

Pterosaur and Bird Trackway From Cretaceous China

New Early Cretaceous Pterosaur-Bird Track Assemblage from Xinjiang, China: Palaeoethology and Palaeoenvironment
Authors:

He Qing et al

Abstract:

A pterosaur-bird track assemblage from a sandstone-siltstone-mudstone sequence of the Lower Cretaceous Tugulu Group of Xinjiang comprises the first pterosaur track record from this province and the largest specimen thus far known from China. The pterosaur tracks are assigned to the ichnogenus Pteraichnus based on the triangular overall-shape, the four elongate digit traces and the robust manual digit trace III. Supposed trackmakers were dsungaripterid pterodactyloids whose skeletal remains are well known from the Tugulu Group. The bird tracks that occur on the same surface, are those of typical shorebirds, known from different other localities in southeast Asia. The congruence with Koreanaornis dodsoni described from the same stratigraphic level justifies an assignment to this ichnospecies. This is a further evidence of the co-occurrence of pterosaurs and birds in a typical lakeshore environment with possible seasonal alteration of water supply and aerial exposure indicated by wave ripples, mudcracks and repeated cycles of coarse to fine sediment. Pterosaurs and birds frequented the shoreline and may have fed also on the numerous invertebrates such as the Scoyenia tracemaker that left abundant burrows.