Late Jurassic Fossil Research Articles

Vertebral size ratios and the ichthyosaurian vertebral column – a case study based on Late Jurassic fossils from North-East Greenland

Vertebral centra are some of the most common fossils from ichthyosaurs and thus valuable for understanding these marine reptiles. This study sets out to provide further information on the dimensional ratios of centra and how these might be used to obtain more information about an assemblage of Late Jurassic disarticulated centra found at Kingofjeldet on Kuhn Ø in North-East Greenland in 2017. The centra are used to test whether vertebral ratios (H:W and H:L) can be used to assign disarticulated and possibly weathered centra to a region in the vertebral column. In order to evaluate this, the ratios of the centra from Greenland were compared with those of five articulated and well-known ophthalmosaurid specimens, as well as classical traits based on morphology. Assigning the correct position in the vertebral column from ratios is, however, not straightforward. Firstly, comparing different ichthyosaur taxa gives different possible positions for the disarticulated centra. Secondly, centra from different vertebral regions commonly display similar ratios. Thirdly, ratios are sensitive to alteration by taphonomic processes. The ratios of the centra hints towards an ichthyosaur with a more regionalised vertebral column being present in the Late Jurassic sea of North-East Greenland. Further studies are needed to improve our understanding of the significance of the degree of regionalisation of the vertebral column among ichthyosaurs.

The Owadów-Brzezinki geoeducation area at Sławno

The geoeducation area (called also “Owadów-Brzezinki Geopark”) located in the north-western margin of the Holy Cross Mountains (Tomaszów Syncline) at Sławno community (Łódź Voivodeship), was established in June 2019, in close vicinity of the Owadów-Brzezinki quarry. This locality is one of the most important palaeontological sites described recently in Poland. The area consists of the exhibition pavilion, educational routs and panoramic viewing platform, which is located along the edge of the quarry. The palaeontological exhibition shows the unique Late Jurassic fossils of marine and terrestrial organisms, many of them new to science, that have been excavated in the quarry during the last eight years. Among the most important fossils are: ammonites, lobster-like decapod crustaceans, horseshoe crabs, actinopterygian fish, a cryptodiran turtle, ichthyosaurs, as well as a small terrestrial crocodyliform, pterosaurs and insects. In addition to the original fossils, the exhibition presents life-size reconstructions of animals, that inhabited the local seas and islands during the Late Jurassic. The palaeontological sites of Owadów-Brzezinki is referred to as a new “taphonomic window” of the Late Jurassic, providing insights about the evolution of life on Earth in the palaeogeographical and palaeoenvironmental context.

Middle-Late Jurassic fossils from northeastern China reveal morphological stasis in the catkin-yew.

Middle-Late Jurassic fossils from northeastern China reveal morphological stasis in the catkin-yew.

Plant remains from the Middle–Late Jurassic Daohugou site of the Yanliao Biota in Inner Mongolia, China

AbstractA late Middle–early Late Jurassic fossil plant assemblage recently excavated from two Callovian–Oxfordian sites in the vicinity of the Daohugou fossil locality in eastern Inner Mongolia, China, was analysed in detail. The Daohugou fossil assemblage is part of the Callovian–Kimmeridgian Yanliao Biota of north-eastern China. Most major plant groups thriving at that time could be recognized. These include ferns, caytonialeans, bennettites, ginkgophytes, czekanowskialeans and conifers. All fossils were identified and compared with species from adjacent coeval floras. Considering additional material from three collections housed at major palaeontological institutions in Beijing, Nanjing and Pingyi, and a recent account in a comprehensive book on the Daohugou Biota, the diversity of the assemblage is completed by algae, mosses, lycophytes, sphenophytes and putative cycads. The assemblage is dominated by tall-growing gymnosperms such as ginkgophytes, czekanowskialeans and bennettites, while seed ferns, ferns and other water- or moisture-bound groups such as algae, mosses, sphenophytes and lycophytes are represented by only very few fragmentary remains. The floral composition underlines the Callovian–Kimmeridgian age of the Yanliao Biota. The Daohugou/Yanliao flora is a typical member of the Middle to Late JurassicConiopteris-Phoenicopsisassemblage of north-eastern China, differing from the Early Cretaceous Jehol flora. Both floras probably belong to the same cycle of volcanism and sedimentation, although the Daohugou Bed is older than the Yixian Formation. The Yanliao fossil assemblage is placed in a larger palaeo-phytogeographical context and its relationships with Middle–Late Jurassic floras from north-eastern China, north-eastern and eastern Siberia and Japan are evaluated.

New Specimens ofAnchiornis huxleyi(Theropoda: Paraves) from the Late Jurassic of Northeastern China

ABSTRACT Four new specimens of Anchiornis huxleyi (PKUP V1068, BMNHC PH804, BMNHC PH822, and BMNHC PH823) were recently recovered from the Late Jurassic fossil beds of the Tiaojishan Formation in northeastern China. These new specimens are almost completely preserved with cranial and postcranial skeletons. Morphological features of Anchiornis huxleyi have implications for paravian character evolution and provide insights into the relationships of major paravian lineages. Anchiornis huxleyi shares derived features with avialans, such as a straight nasal process of the premaxilla and the absence of an external mandibular fenestra in lateral view. However, Anchiornis huxleyi lacks several derived deinonychosaurian features, including a laterally exposed splenial and a specialized raptorial pedal digit II. Morphological comparisons strongly suggest Anchiornis is more closely related to avialans than to deinonychosaurians or troodontids. Anchiornis huxleyi exhibits many conservative paravian features, and clos...

Modern hydrophilid clades present and widespread in the Late Jurassic and Early Cretaceous (Coleoptera: Hydrophiloidea: Hydrophilidae)

We present a summary of the fossil evidence documenting the worldwide occurrence of the family Hydrophilidae (Insecta: Coleoptera: Polyphaga: Hydrophiloidea) in the Late Jurassic and Early Cretaceous. We present the first known fossils of the family from the Mesozoic, being c. 100 Myr older than the fossil record available until now. Two Late Jurassic fossils are documented: Protochares brevipalpis gen. nov., sp. nov. from the Talbragar Fish Bed (New South Wales, Australia) and ‘Mesosperchus’ schultzi Ponomarenko, 1985 from Solnhofen (Bavaria, Germany). The occurrence of the Hydrophilidae in the Early Cretaceous is documented by six species, all of which may be already assigned to modern subfamilies/tribes: Baissalarva hydrobioides gen. nov., sp. nov. from the Baissa outcrops (Buryat Republic, Russia) and Cretoxenus australis gen. nov., sp. nov. from Koonwarra outcrops (Victoria, Australia) are both assigned to the tribe Hydrobiusini (Hydrophilinae); Alegorius yixianus gen. nov., sp. nov. and Alegorius sp. from the Yixian Formation (Liaoning, China) may represent the Acidocerinae or Enochrinae, Hydroyixia elongata gen. nov., sp. nov. and H. latissima sp. nov. from the same locality are assigned to the Acidocerinae. The phylogenetic position of Baissalarva hydrobioides is also tested by a phylogenetic analysis. The presence of extant clades (Hydrophilinae: Hydrobiusini, Acidocerinae) in the Early Cretaceous and the wide distribution of the Hydrobiusini in both Gondwana and Laurasia at the same time suggests that the principal extant clades of the Hydrophilidae are at least of Early–Middle Jurassic origin. © 2014 The Linnean Society of London

Postcranial axial skeleton of Europasaurus holgeri (Dinosauria, Sauropoda) from the Upper Jurassic of Germany: implications for sauropod ontogeny and phylogenetic relationships of basal Macronaria

Neosauropods are well represented in the Late Jurassic fossil record, both in Laurasia and Gondwana. Among Macronaria, Europasaurus represents one of the most basal forms of this group. In addition to its systematic importance, Europasaurus is also the first unequivocal dwarf sauropod from which adult and juvenile material is available. Despite the abundance of sauropods in the fossil record, early juvenile specimens are rare, limiting knowledge about sauropod ontogeny. Therefore, the great amount of material of Europasaurus provides an excellent opportunity to improve our knowledge on the early evolution of Macronaria, as well as to shed light on some morphological changes through ontogeny. The postcranial axial skeleton of sauropods is extremely modified with respect to the anatomy observed in its ancestors, the ‘prosauropods’, proving to be one of the most informative regions of the body. Here we provide a detailed description of the axial skeleton of Europasaurus, including adult and juvenile elements, discussing its systematic and ontogenetic importance. We also analyse the phylogenetic position of Europasaurus through a cladistic analysis using TNT, which retrieves this taxon in a basal position among Camarasauromorpha. Additionally, the presence/absence of discrete characters and the comparison of juvenile elements with adult specimens allowed us to recognize different morphological ontogenetic stages (MOS). Whereas early stages lack derived characters (e.g. spinodiapophyseal lamina and prespinal lamina on dorsal vertebrae), all derived characters (including autapomorphies) are present in late immature specimens. Therefore, while late immature specimens provide the same phylogenetic signal as adult specimens of Europasaurus, more immature stages are recovered in a basal position among sauropods. Finally, we apply the MOS to other maturity criteria (e.g. neurocentral closure, sexual maturity) in a search for a wider definition of maturity.

The petrosal and inner ear of the Late Jurassic cladotherian mammalDryolestes leiriensisand implications for ear evolution in therian mammals

Dryolestes leiriensis is a Late Jurassic fossil mammal of the dryolestoid superfamily in the cladotherian clade that includes the extant marsupials and placentals. We used high resolution micro-computed tomography (µCT) scanning and digital reconstruction of the virtual endocast of the inner ear to show that its cochlear canal is coiled through 270°, and has a cribriform plate with the spiral cochlear nerve foramina between the internal acoustic meatus and the cochlear bony labyrinth. The cochlear canal has the primary bony lamina for the basilar membrane with a partially formed (or partially preserved) canal for the cochlear spiral ganglion. These structures, in their fully developed condition, form the modiolus (the bony spiral structure) of the fully coiled cochlea in extant marsupial and placental mammals. The CT data show that the secondary bony lamina is present, although less developed than in another dryolestoid Henkelotherium and in the prototribosphenidan Vincelestes. The presence of the primary bony lamina with spiral ganglion canal suggests a dense and finely distributed cochlear nerve innervation of the hair cells for improved resolution of sound frequencies. The primary, and very probably also the secondary, bony laminae are correlated with a more rigid support for the basilar membrane and a narrower width of this membrane, both of which are key soft-tissue characteristics for more sensitive hearing for higher frequency sound. All these cochlear features originated prior to the full coiling of the therian mammal cochlea beyond one full turn, suggesting that the adaptation to hearing a wider range of sound frequencies, especially higher frequencies with refined resolution, has an ancient evolutionary origin no later than the Late Jurassic in therian evolution. The petrosal of Dryolestes has added several features that are not preserved in the petrosal of Henkelotherium. The petrosal characters of dryolestoid mammals are essentially the same as those of Vincelestes, helping to corroborate the synapomorphies of the cladotherian clade in neural, vascular, and other petrosal characteristics. The petrosal characteristics of Dryolestes and Henkelotherium together represent the ancestral morphotype of the cladotherian clade (Dryolestoidea + Vincelestes + extant Theria) from which the extant therian mammals evolved their ear region characteristics. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166, 433–463.

A blast from the past: the lost world of dinosaurs at Tendaguru, East Africa

The superbly preserved dinosaurs and associated organisms from the Late Jurassic fossil Lagerstätte Tendaguru in southern Tanzania mark an exceptional success story in palaeontology. The new permanent exhibits of the Museum für Naturkunde in Berlin, highlighting the spectacular dinosaurs (Fig. 1), are telling evidence. In more than 100 years of research, geoscientists produced a considerable amount of knowledge about the composition and diversity of the ancient fauna and flora at Tendaguru, their unique palaeobiological characteristics, and the continental to marginal marine ecosystems in which they lived. Several questions are still open to debate. These include the detailed genesis of the Lagerstätte, aspects of dinosaur palaeobiology, and their biogeographical affinities to contemporaneous assemblages from the Northern Hemisphere.The discovery of Brachiosaurus was the crowning achievement of the German Tendaguru expedition of 1909–1913. The skeleton is about 13 metres tall and 23 metres long. It is on display in the dinosaur hall of the Museum für Naturkunde (MfN) in Berlin along with Dicraeosaurus, Kentrosaurus, Dysalotosaurus and Elaphrosaurus. They constitute the most significant dinosaur discoveries ever made in Africa. Photo: Antje Dittmann, MfN.image

A high-resolution three-dimensional reconstruction of a fossil forest (Upper Jurassic Shishugou Formation, Junggar Basin, Northwest China)

This study focuses on the three-dimensional (3D) reconstruction of an Late Jurassic fossil forest based on a fossil assemblage located in the Shishugou Formation near Jiangjunmiao, north-eastern Junggar Basin, Xinjiang Uygur Autonomous Region, Northwest China. On the basis of tree stumps found in growth position together with published data on megaplant fossils, seeds and spores, a high-resolution digital computer model, including different forest layers, was developed. In a study area of 31,500 m², 65 tree stumps with diameters between 0.2 and 2.9 m were mapped and subsequently used for the 3D reconstruction. The forest grew under moist conditions, probably close to the banks of an anastomosing river and consisted primarily of conifers, in particular Araucariaceae. Even though the tree density of the forest is only 22 trees/ha, the 3D reconstruction indicates a relatively closed canopy. Megaplant fossils and spores also show evidence for the presence of Angiopteris, Osmunda and Coniopteris, which were then used to reconstruct the understory of the forest. The trees were modelled in three different growth stages, representing young, older and mature trees, respectively. The growth parameters of individual trees and ferns were randomized in order to avoid duplications within the reconstruction. Detailed textures of leaves, fronds and bark were created to give the plants a more realistic appearance than that in previously published 3D reconstructions of fossil forest assemblages. Estimations of net biomass (approximately 9 tons/ha), annual biomass production and a calculation of nearest neighbour index (0.86) suggest an open forest with spatially distributed trees.

A Late Jurassic fossil assemblage in Gondwana: Biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay

The Tacuarembó Formation has yielded a fossil assemblage that includes the best known body fossils, consisting of isolated scales, teeth, spines, and molds of bones, recovered from thin and patchy bonebeds, from the Botucatu Desert, Parana Basin, South America. The remains are preserved in the sandstones widespread around the city of Tacuarembó. We propose a new formalized nomenclature for the Tacuarembó Formation, naming its “Lower” and “Upper” members as the Batoví (new name) and Rivera (new rank) members, respectively. An assemblage zone is defined for the Batoví Member (fluviolacustrine and aeolian deposits). In this unit, the freshwater hybodontid shark Priohybodus arambourgi D’Erasmo is well represented. This species was previously recorded in Late Jurassic–Early Cretaceous units of the Sahara and the southern Arabian Peninsula. Globally considered, the fossil assemblage of this member ( P. arambourgi, dipnoan fishes, Ceratosaurus-like theropods, and conchostracans) is indicative of a Kimmeridgian–Tithonian age, which in combination with the stratigraphic relationships of the Tacuarembó Formation with the overlying basalts of the Arapey Formation (132 My average absolute age) implies that the latter was deposited during the Kimmeridgian–Hauterivian interval.

Discovery of Late Jurassic fossils inside modern sediments at Gorringe Bank (Eastern Atlantic Ocean) and some geological implications.

AbstractDuring a recent expedition at the Gorringe Bank (eastern Atlantic, 150 miles SW off Portugal), one of the rare sites in the ocean where mantle rocks crop out at very shallow depths (− 30 m), the Gettysburg and Ormonde seamounts, the two summits on the Gorringe Bank, were surveyed in detail. At Gettysburg seamount, within the modern bioclastic material, which is continually produced on the summit and exported to deep water, several examples of Mesozoic cephalopods were found. These fossils, reworked ‘in situ’, gave an age spanning from Kimmeridgian–Tithonian to Hauterivian (145–155 Ma) and recall some condensed Jurassic sequences of the Thetyan region compatible with shallow water (< 200 m). The serendipitous discovery of such ancient faunas within modern sediments suggests that Gorringe Bank was a seamount at the early opening of the Atlantic Ocean and requires us to reassess the age of rifting along the Iberian margin and the importance of vertical tectonics for non‐volcanic, mantle‐rooted seamounts.

Derived Jurassic fossils from the Vectis Formation (Lower Cretaceous) of the Isle of Wight, southern England

Derived late Jurassic fossils occur commonly in the uppermost part of the Vectis Formation (Wealden Group, Lower Cretaceous) at Sandown Bay, on the southeast coast of the Isle of Wight. These records corroborate subsurface data which indicate the close proximity of Jurassic sediments on the footwall of the syn-depositional fault (Purbeck-Isle of Wight structure) which marked the northern margin of the Channel Basin during Wealden times. The most abundant derived fossils are bivalves (oysters, scallops), with rarer echinoid spines and serpulid worms, derived from late Oxfordian and early Kimmeridgian sediments. Worn phosphatized fragments of the ammonite Pavlovia sp. occur rarely, and were probably derived from late Kimmeridgian or early Portlandian pebble beds to the north of the Island. A model for formation of the derived fossil concentrations which involves storm action and winnowing is based on comparisons between the environment during formation of the Vectis Formation and the present day Fleet lagoon in Dorset.

志摩半島の秩父帯南帯

The Chichibu Terrain in the Shima Peninsula is, like elsewhere in Southwest Japan, divided into the northern, middle and southern belts by longitudinal faults. The southern belt consists of the Imaura Group and the Chichibu Complex (Tsuiji Group). The Imaura Group is distributed only along the northern margin of the belt, while the Tsuiji Group occupies the major part. Four lithofacies are tentatively distinguished in the Tsuiji Group, i. e., massive sandstone facies, sandstone and mudstone facies, olistostrome facies and chert-clastics facies. The first three may correspond to the elastic interval of the chert-clastics facies. In chert-clastics facies, the lithology changes upwards from chert at the base, through siliceous mudstone, mudstone to coarse grained clastics such as sandstone, sandstone alternating with mudstone, olistostrome. Radiolarian fossils obtained from several horizons of this sequence show that rocks are younger upwards from the Triassic of chert to the late Jurassic of mudstone. The age of the uppermost coarse grained clastics has not been clarified due to lack of fossils therein. However, occasionally observed conformable facies change from mudstone to sandstone justifies the view that coarse grained clastics are the youngest of the sequence. The chert-clastics sequence is reasonably regarded as representing the original stratigraphic unit. A single unit may be a product of successive sedimentation on the Pacific plate gradually approaching to the cotninent. Gradual upward change of the lithology in a unit represents the landward shift of the plate and the increasing availability of receiving the terrigenous material on the plate.The Imaura Group covers the Tsuiji Group either conformably or unconformably. It consists mainly of mudstone containing sporadically limestones rich in the late Jurassic fossils and has been hitherto correlated to the Upper Jurassic based on these fossils. We obtained radiolarian fossils indicating the early Cretaceous in age from mudstone. This leads to the conclusion that the fossil-bearing limestones are resedimented blocks emplaced into the radiolarian-bearing mudstone in the early Cretaceous period.

Late Jurassic fossils from Cuba and their economic significance

The Vinales limestone fauna is correlated with the upper Portlandian on the basis of the ranges of its normally coiled ammonites and their similarity with species in the upper Portlandian of Mexico and Argentina. Genera not known below the upper Portlandian include Corongoceras, Micracanthoceras, Durangites, Lytohoplites, and Parodontoceras. Genera not known above the Portlandian include Metahaploceras, Physodoceras, and Durangites. Genera not known above the lower Tithonian include Corongoceras and Lytohoplites. Previous correlation with the Lower Cretaceous was based mainly on identity of aptychi and similarity of uncoiled ammonites to species in the Lower Cretaceous of southern Europe. Association of these forms with normal ammonites permits no doubt as to their Portlandian age and suggests that aptychi must be used with caution in detailed stratigraphic work. Nothing in the fauna suggests the Kimmeridgian or Tithonian stages. The much younger age of the fauna than that of the Argovian-lower Kimmeridgian ammonites, described by Sanchez Roig and Marjorie O9Connell, shows that the older fossils are from the San Cayetano formation beneath the Vinales limestone, and that these formations are separated by an unconformity involving parts of the Kimmeridgian and Portlandian. Furthermore, the study shows that undoubted Lower Cretaceous rocks have not yet been found in the West Indies, that metamorphic rocks elsewhere in the West Indies may be Jurassic, and that the regions bordering the Gulf of Mexico have a similar Jurassic history. It suggests that the Palisade disturbance is late Jurassic. Application of these conclusions toward forming a clearer picture of events in Jurassic and Lower Cretaceous times should aid in showing the time of origin and possible distribution of mineral deposits and should be particularly useful in explorations for petroleum in the deeply buried rocks of the Gulf region.