Top fossils discoveries of 2018.

Ingentia prima outcropping from the soil.

Paraphrasing Dickens, 2018 was the best of years, and it was the worst of years. Marked by extreme weather, earthquakes, and an intense volcanic activity, 2018 is also noted by amazing fossil discoveries. My top list include:

  • The oldest Archaeopteryx

Articulated dorsal vertebral column of the new Archaeopteryx, including dorsal ribs and gastralia. Scale bar is 10 mm. (From Rauhut et al., 2018)

The Archaeopteryx story began in  the summer of 1861, two years after the publication of the first edition of Darwin’s Origin of Species, when workers in a limestone quarry in Germany discovered the impression of a single 145-million-year-old feather. Over the years, eleven Archaeopteryx specimens has being recovered. The new specimen from the village of Schamhaupten, east-central Bavaria is the oldest representative of the genus (earliest Tithonian). The shoulder girdles and arms, as well as the skull have been slightly dislocated from their original positions, but the forelimbs remain in articulation. The skull is triangular in lateral outline and has approximately 56 mm long. The orbit is the largest cranial opening (approximately 16 mm long), and the lateral temporal fenestra is collapsed. There are probably four tooth positions in the premaxilla, nine in the maxilla and 13 in the dentary. The postcranial skeleton was affected by breakage and loss of elements prior to or at the time of discovery.

  • Tratayenia rosalesi

Fossilized vertebrae and right hip bone of Tratayenia rosalesi. From Porfiri et al., 2018

Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, including Megaraptora, a clade of medium-sized and highly pneumatized theropods represented by Fukuiraptor, Aerosteon, Australovenator, Megaraptor, Murusraptor, and Orkoraptor, and characterized by the formidable development of their manual claws on digits I and II and the transversely compressed and ventrally sharp ungual of the first manual digit. Tratayenia rosalesi is the first megaraptoran theropod described from the Santonian Bajo de la Carpa Formation of the Neuquén Group. The genus name is for Tratayén, the locality where the holotype was collected. The specific name honors Diego Rosales, who discovered the specimen in 2006. Tratayenia is also the largest carnivorous taxon known from Bajo de la Carpa Formation, reinforcing the hypothesis that megaraptorids were apex predators in South America from the Turonian through the Santonian or early Campanian, following the extinction of carcharodontosaurids.

  • Lingwulong shenqi

Skeletal reconstruction and exemplar skeletal remains of Lingwulong shenqi. Scale bars = 100 cm for a and 5 cm for b–o. From Xi et al., 2018

Sauropods were the largest terrestrial vertebrates. Their morphology is easy recognizable: a long, slender neck and a tail at the end of a large body supported by four columnar limbs. Sauropods dominated many Jurassic and Cretaceous terrestrial faunas. Although they were globally distributed, the absence of Diplodocoidea from East Asia has been interpreted as a biogeographic pattern caused by the Mesozoic fragmentation of Pangea. Lingwulong shenqi — literally the “amazing dragon from Lingwu” — is the first well-preserved confirmed diplodocoid from East Asia (23 synapomorphies support the placement of Lingwulong within Diplodocoidea with 10 of these being unequivocal). The holotype, (LM) V001a, is a partial skull comprising the braincase, skull roof, and occiput, and an associated set of dentary teeth. The paratype, (LGP) V001b, comprises a semi-articulated partial skeleton including a series of posterior dorsal vertebrae, complete sacrum, the first caudal vertebra, partial pelvis, and incomplete right hind limb. The Lingwulong specimens were found in the Yanan Formation at Ciyaopu, in northwest China. The presence of a conchostracans assemblage (including Palaeoleptoestheria, Triglypta, and Euestheria) is indicative of a Middle Jurassic age. The discovery of Lingwulong undermines the EAIH (East Asian Isolation Hypothesis), forcing a significant revision of hypotheses concerning the origins and early radiation of Neosauropoda.

  • Ingentia prima

Skeletal anatomy of Ingentia prima (From Apaldetti et al., 2018)

Ingentia prima — literally the “first giant” in Latin — from the Late Triassic of Argentina shed new lights on the origin of gigantism in this group. The holotype, PVSJ 1086, composed of six articulated posterior cervical vertebrae, glenoid region of right scapula and right forelimb lacking all phalanges, has been recovered from the southern outcrops of the Quebrada del Barro Formation, northwestern Argentina. Discovered in 2015 by Diego Abelín and a team led by Cecilia Apaldetti of CONICET-Universidad Nacional de San Juan, Argentina, this new fossil weighed up to 11 tons and measured up to 32 feet (10 meters) long. Ingentia was unearthed with three new specimens of Lessemsaurus sauropoides. The four dinosaurs belongs to the clade Lessemsauridae, that differs from all other Sauropodomorpha dinosaurs in possessing robust scapulae with dorsal and ventral ends equally expanded; slit-shaped neural canal of posterior dorsal vertebrae; anterior dorsal neural spines transversely expanded towards the dorsal end; a minimum transverse shaft width of the first metacarpal greater than twice the minimum transverse shaft of the second metacarpal; and bone growth characterized by the presence of thick zones of highly vascularized fibrolamellar bone, within a cyclical growth pattern.

  • Caelestiventus hanseni

A 3D printed model of the C. hanseni skull discovered in Utah

Caelestiventus hanseni, from the Upper Triassic of North America, is the oldest pterosaur ever discovered, and it predates all known desert pterosaurs by more than65 million years. The holotype, BYU 20707, includes the left maxilla fused with the jugal, the right maxilla, the right nasal, the fused frontoparietals, the right and left mandibular rami, the right terminal wing phalanx and three fragments of indeterminate bones. The maxilla, jugal, frontoparietal, and mandibular rami of the specimen are pneumatic. The unfused skull and mandibular elements suggest that BYU 20707 was skeletally immature or had indeterminate growth. Based on the relationship between the length of the terminal wing phalanges and wing span in other non-pterodactyloid pterosaurs the new taxon would have a wing span greater than 1.5 m. The significance of C. hanseni lies in its exceptional state of preservation, and its close phylogenetic relationship with Dimorphodon macronyx, indicating that dimorphodontids originated by the Late Triassic and survived the end-Triassic extinction event.

  • Macrocollum itaquii

Skull of Macrocollum itaquii (From Müller et al 2018)

Macrocollum itaquii is the oldest long-necked dinosaur known. Discovered in 2012, from rocks belonging to the upper part of the Candelaria Sequence constrained as about 225 Ma, the three individuals described as M. itaquii are relatively well preserved. The holotype specimen (CAPPA/UFSM 0001a) consists of an almost complete and articulated skeleton. The two paratype specimens (CAPPA/UFSM 0001b and CAPPA/UFSM 0001c) are both articulated skeletons with one missing a skull and its cervical series. The clustered preservation of the three skeletons also represents the oldest evidence of gregarious behaviour in sauropodomorphs, a pattern seen in other Triassic associations, such as the ‘Plateosaurus bonebed’ from Central Europe, and the Mussaurus remains from the Laguna Colorada Formation, Argentina. M. itaquii was only 3.5 meters long and weighed about 101.6 kilograms. In contrast to most Carnian members of the group, the teeth of M. itaquii and other Norian taxa are fully adapted to an omnivore/herbivore diet. The neck elongation may also have provided a competitive advantage for gathering food resources, allowing members of the group to reach higher vegetation. The modifications of the hindlimb of M. itaquii could be related to the progressive loss of cursorial habits.

  • Soft-tissue evidence in a Jurassic ichthyosaur.

Stenopterygius specimen from the Holzmaden quarry. Credit: Johan Lindgren

During the Norian, the evolution of ichthyosaurs took a major turn, with the appearance of the clade Parvipelvia (ichthyosaurs with a small pelvic girdle). They were notably similar in appearance to extant pelagic cruisers such as odontocete whales. An exquisitely fossilized parvipelvian Stenopterygius from the Early Jurassic (Toarcian) of the Holzmaden quarry in southern Germany, indicates that their resemblance with dolphin and whales is more than skin deep. The specimen (MH 432; Urweltmuseum Hauff, Holzmaden, Germany) reveals endogenous cellular, sub-cellular and biomolecular constituents within relict skin and subcutaneous tissue. The external surface of the body is smooth, and was presumably comparable in life to the skin of extant cetaceans. The histological and microscopic examination of the fossil, evinced a multi-layered subsurface architecture. The approximately 100-μm-thick epidermis retains cell-like structures that are likely to represent preserved melanophores. The subcutaneous layer is over 500 μm thick, and comprises a glossy black material superimposed over a fibrous mat. The anatomical localization, chemical composition and fabric of the subcutaneous material is interpreted as fossilized blubber, a hallmark of warm-blooded marine amniotes.

  • Pterosaurs and feathers

 

Type 3 filaments (arrows) and similar structures (triangles). Scale bars: 10 mm in a, c and d; 1 mm in b. From Yang et al., 2018

Feathers were once considered to be unique avialan structures. Recent studies indicated that non avian dinosaurs, as part of Archosauria, possessed the entirety of the known non keratin protein-coding toolkit for making feathers. Primitive theropods, such as Sinosauropteryx and the tyrannosaurs Dilong and Yutyrannus, and some plant-eating ornithischian dinosaurs, such as Tianyulong and Kulindadromeus, are known from their spectacularly preserved fossils covered in simple, hair-like filaments called ‘protofeathers’. Other integumentary filaments, termed pycnofibres, has been reported in several pterosaur specimens, but there is still a substantial disagreement regarding their interpretation. J. Yang and colleagues described two specimens of short-tailed pterosaurs (NJU–57003 and CAGS–Z070) from the Middle-Late Jurassic Yanliao Biota, in northeast China (around 165-160 million years ago) with preserved structural fibres (actinofibrils) and four different types of pycnofibres. The specimens resemble Jeholopterus and Dendrorhynchoides, but they are relatively small. Pterosaurs were winged cousins of the dinosaurs and lived from around 200 million years ago to 66 million years ago. In the early 1800’s, a fuzzy integument was first reported from the holotype of Scaphognathus crassirostris. A recent study on this specimen shows a subset of pycnofibers and actinofibrils. The discovery of integumentary structures in other pterosaurs, such as Pterorhynchus wellnhoferi(another rhamphorhynchoid pterosaur), and these exquisitely preserved pterosaurs from China, suggest that all Avemetatarsalia (the wide clade that includes dinosaurs, pterosaurs and close relatives) were ancestrally feathered.

References:

Rauhut OWM, Foth C, Tischlinger H. (2018The oldest Archaeopteryx (Theropoda: Avialiae): a new specimen from the Kimmeridgian/Tithonian boundary of Schamhaupten, BavariaPeerJ 6:e4191 https://doi.org/10.7717/peerj.4191

Porfiri, J.D., Juárez Valieri, Rubé.D., Santos, D.D.D., Lamanna, M.C., A new megaraptoran theropod dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia, Cretaceous Research (2018), doi: 10.1016/j.cretres.2018.03.014.

Xing Xu, Paul Upchurch, Philip D. Mannion, Paul M. Barrett, Omar R. Regalado-Fernandez, Jinyou Mo, Jinfu Ma and Hongan Liu. 2018. A New Middle Jurassic Diplodocoid Suggests An Earlier Dispersal and Diversification of Sauropod Dinosaurs. Nature Communications.9, 2700.  DOI:  10.1038/s41467-018-05128-1 

Cecilia Apaldetti, Ricardo N. Martínez, Ignacio A. Cerda, Diego Pol and Oscar Alcober (2018). An early trend towards gigantism in Triassic sauropodomorph dinosaurs. Nature Ecology & Evolution. https://doi.org/10.1038/s41559-018-0599-y

Brooks B. Britt et al. Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years, Nature Ecology & Evolution (2018). DOI: 10.1038/s41559-018-0627-y

Müller RT, Langer MC, Dias-da-Silva S. 2018, An exceptionally preserved association of complete dinosaur skeletons reveals the oldest long-necked sauropodomorphs. Biol. Lett. 14: 20180633. http://dx.doi.org/10.1098/rsbl.2018.0633

Lindgren, J., Sjövall, P., Thiel, V., Zheng, W., Ito, S., Wakamatsu, K., … Schweitzer, M. H. (2018). Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur. Nature. doi:10.1038/s41586-018-0775-x

Yang Z. et al., 2018. Pterosaur integumentary structure with complex feather-like branching. Nature Ecology and Evolution https://doi.org/10.1038/s41559-018-0728-7

Soft-tissue evidence in a Jurassic ichthyosaur.

Plesiosaurus battling Temnodontosaurus (Oligostinus), front piece the Book of the Great Sea-Dragons by Thomas Hawkins.

In 1811, in Lyme Regis, one of the richest fossil locations in England and part of a geological formation known as the Blue Lias, Mary Anning and her brother Joseph unearthed the skull of an enigmatic ‘sea monster’. A year later, Mary uncovered the torso of the same specimen. The Annings sold the fossil to the Lord of the Manor of Colway, Mr. Henry Henley, for £23. The specimen was described by Sir Everard Home in 1814. Although no name was proposed for the fossil, Home concluded that it represented a transitional form between fish and crocodiles. Later, in 1819, the skeleton was purchased by Karl Dietrich Eberhard Koenig of the British Museum of London who suggested the name Ichthyosaur (“fish lizard”) in 1817.
Ichthyosaurs are extinct marine reptiles that first diversified near the end of the Early Triassic and remained one of the main predators in the Mesozoic ocean until their disappearance near the Cenomanian-Turonian boundary, 30 million years before the end-Cretaceous mass extinction. They had the largest eyes of all vertebrates, sometimes exceeding 25 cm in maximum diameter. They also have one of the earliest records of live-birth in amniotes.
 

Stenopterygius specimen from the Holzmaden quarry. Credit: Johan Lindgren

Stephen Jay Gould said that the ichthyosaur was his favourite example of convergent evolution: “Consider my candidate for the most astounding convergence of all: the ichthyosaur. This sea-going reptile with terrestrial ancestors converged so strongly on fishes that it actually evolved a dorsal fin and tail in just the right place and with just the right hydrological design. These structures are all the more remarkable because they evolved from nothing— the ancestral terrestrial reptile had no hump on its back or blade on its tail to serve as a precursor.”

During the Norian, the evolution of ichthyosaurs took a major turn, with the appearance of the clade Parvipelvia (ichthyosaurs with a small pelvic girdle). They were notably similar in appearance to extant pelagic cruisers such as odontocete whales. An exquisitely fossilized parvipelvian Stenopterygius from the Early Jurassic (Toarcian) of the Holzmaden quarry in southern Germany, indicates that their resemblance with dolphin and whales is more than skin deep.

Structure and chemistry of MH 432 blubber. From Lindgren et. al. 2018.

The specimen (MH 432; Urweltmuseum Hauff, Holzmaden, Germany) reveals endogenous cellular, sub-cellular and biomolecular constituents within relict skin and subcutaneous tissue. The external surface of the body is smooth, and was presumably comparable in life to the skin of extant cetaceans. The histological and microscopic examination of the fossil, evinced a multi-layered subsurface architecture. The approximately 100-μm-thick epidermis retains cell-like structures that are likely to represent preserved melanophores. The subcutaneous layer is over 500 μm thick, and comprises a glossy black material superimposed over a fibrous mat. The anatomical localization, chemical composition and fabric of the subcutaneous material is interpreted as fossilized blubber, a hallmark of warm-blooded marine amniotes.

 

References:

Lindgren, J., Sjövall, P., Thiel, V., Zheng, W., Ito, S., Wakamatsu, K., … Schweitzer, M. H. (2018). Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur. Nature. doi:10.1038/s41586-018-0775-x

Motani, R. (2005). EVOLUTION OF FISH-SHAPED REPTILES (REPTILIA: ICHTHYOPTERYGIA) IN THEIR PHYSICAL ENVIRONMENTS AND CONSTRAINTS. Annual Review of Earth and Planetary Sciences, 33(1), 395–420. doi:10.1146/annurev.earth.33.092203.1227

Lingwulong shenqi, the “Amazing Dragon”, and the dispersal of Sauropods.

Skeletal reconstruction and exemplar skeletal remains of Lingwulong shenqi. Scale bars = 100 cm for a and 5 cm for b–o. From Xu et al., 2018

Sauropods were the largest terrestrial vertebrates. Their morphology is easy recognizable: a long, slender neck and a tail at the end of a large body supported by four columnar limbs. Sauropods dominated many Jurassic and Cretaceous terrestrial faunas. Although they were globally distributed, the absence of Diplodocoidea from East Asia has been interpreted as a biogeographic pattern caused by the Mesozoic fragmentation of Pangea. However, a newly discovered dinosaur from the Middle Jurassic of northern China suggests that Sauropods dispersed and diversified earlier than previously thought.

Lingwulong shenqi — literally the “amazing dragon from Lingwu” — is the first well-preserved confirmed diplodocoid from East Asia (23 synapomorphies support the placement of Lingwulong within Diplodocoidea with 10 of these being unequivocal). The holotype, (LM) V001a, is a partial skull comprising the braincase, skull roof, and occiput, and an associated set of dentary teeth. The paratype, (LGP) V001b, comprises a semi-articulated partial skeleton including a series of posterior dorsal vertebrae, complete sacrum, the first caudal vertebra, partial pelvis, and incomplete right hind limb.

An artist’s interpretation of what Lingwulong shenqi (Image: Zhang Zongda)

The Lingwulong specimens were found in the Yanan Formation at Ciyaopu, in northwest China. This formation has been divided in four or five members. Although, no radiometric constraints have been obtained for the Yanan Formation, its age has been estimated on the basis of biostratigraphy. The presence of a conchostracans assemblage (including Palaeoleptoestheria, Triglypta, and Euestheria) is indicative of a Middle Jurassic age.

The East Asian Isolation Hypothesis (EAIH) has become a well-established explanation of profound differences between Jurassic (and sometimes Early Cretaceous) Asian terrestrial faunas, that resulted in the evolution of endemic groups such as mamenchisaurid sauropods, and the early diverging lineage of tetanurans, oviraptorosaurs, therizinosaurs. In this model, the isolation ended in the Early Cretaceous when marine regressions allowed the invasion of groups from elsewhere in Pangaea, and the dispersal of Asian endemics (e.g., oviraptorosaurs, marginocephalians) into Europe and North America. However, it was claimed that diplodocoids never took part in these dispersals because the end-Jurassic extinction that greatly reduced their diversity and geographic range in the Early Cretaceous. The discovery of Lingwulong undermines the EAIH, forcing a significant revision of hypotheses concerning the origins and early radiation of Neosauropoda.

 

References:

Xing Xu, Paul Upchurch, Philip D. Mannion, Paul M. Barrett, Omar R. Regalado-Fernandez, Jinyou Mo, Jinfu Ma and Hongan Liu. 2018. A New Middle Jurassic Diplodocoid Suggests An Earlier Dispersal and Diversification of Sauropod Dinosaurs. Nature Communications.9, 2700.  DOI:  10.1038/s41467-018-05128-1 

 

 

 

Introducing Caihong juji

Caihong juji holotype specimen (Hu, et al., 2018)

Over the last 10 years, theropod dinosaurs from the Middle-Late Jurassic Yanliao Biota have offered rare glimpses of the early paravian evolution and particularly the origin of birds. The first discovered Yanliao non-scansoriopterygid theropod was Anchiornis huxleyi, and since then several other extremely similar species have also been reported. Caihong juji, a newly discovered Yanliao specimen, exhibits an array of osteological features, plumage characteristics, and putative melanosome morphologies not previously seen in other Paraves. The name Caihong is from the Mandarin ‘Caihong’ (rainbow). The specific name, juji is from the Mandarin ‘ju’ (big) and ‘ji’ (crest), referring to the animal’s prominent lacrimal crests.

The holotype (PMoL-B00175) is a small, articulated skeleton with fossilized soft tissues, preserved in slab and counter slab, collected by a local farmer from Qinglong County, Hebei Province, China, and acquired by the Paleontological Museum of Liaoning in February, 2014. The specimen (estimated to be ~400 mm in total skeletal body length with a body mass of ~475 g) exhibits the following autapomorphies within Paraves: accessory fenestra posteroventral to promaxillary fenestra, lacrimal with prominent dorsolaterally oriented crests, robust dentary with anterior tip dorsoventrally deeper than its midsection and short ilium.

Caihong juji differs from Anchiornis huxleyi in having a shallow skull with a long snout, forelimb proportionally short, and forearm proportionally long. Caihong also resembles basal troodontids and to a lesser degree basal dromaeosaurids in dental features (anterior teeth are slender and closely packed, but middle and posterior teeth are more stout and sparsely spaced; and serrations are absent in the premaxilla and anterior maxilla).

Platelet-like nanostructures in Caihong juji and melanosomes in iridescent extant feathers (Hu, et al., 2018)

Feathers are well preserved over the body, but in some cases, they are too densely preserved to display both gross and fine morphological features. The contour feathers are proportionally longer than those of other known non-avialan theropods. The tail feathers resemble those of Archaeopteryx, and the troodontid Jinfengopteryx in having large rectrices attaching to either side of the caudal series forming a frond-shaped tail, a feature that has been suggested to represent a synapomorphy for the Avialae.

But, the most remarkable feature observed in Caihong, is the presence of some nanostructures preserved in the head, chest, and parts of its tail, that have been identified as melanosomes. They are long, flat, and organized into sheets, with a pattern similar of those of the iridescent throat feathers of hummingbirds.

Recovered as a basal deinonychosaur, Caihong shows the earliest asymmetrical feathers and proportionally long forearms in the theropod fossil record wich indicates locomotor differences among closely related Jurassic paravians and has implications for understanding the evolution of flight-related features.

References:

Hu, et al. A bony-crested Jurassic dinosaur with evidence of iridescent plumage highlights complexity in early paravian evolution. Nature (2018) doi:10.1038/s41467-017-02515-y

Godefroit, P. et al. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498, 359–362 (2013).

Terrestrial floras at the Triassic-Jurassic Boundary in Europe.

Proportions of range-through diversities of higher taxonomic categories of microfloral elements over the Middle Triassic–Early Jurassic interval (From Barbacka et al., 2017)

Over the last 3 decades, mass extinction events  have become the subject of increasingly detailed and multidisciplinary investigations. Most of those events are associated with global warming and proximal killers such as marine anoxia. Volcanogenic-atmospheric kill mechanisms include ocean acidification, toxic metal poisoning, acid rain, increased UV-B radiation, volcanic darkness, cooling and photosynthetic shutdown. The mass extinction at the Triassic-Jurassic Boundary (TJB) has been linked to the eruption of the Central Atlantic Magmatic Province (CAMP), a large igneous province emplaced during the initial rifting of Pangea. Another theory is that a huge impact was the trigger of the extinction event. At least two craters impact were reported by the end of the Triassic. The Manicouagan Impact crater in the Côte-Nord region of Québec, Canada was caused by the impact of a 5km diameter asteroid, and it was suggested that could be part of a multiple impact event which also formed the Rochechouart crater in France, Saint Martin crater in Canada, Obolon crater in Ukraine, and the Red Wing crater in USA (Spray et al., 1998).

Photographs of some Rhaetian–Hettangian spores and pollen from the Danish Basin (From Lindström, 2015)

Most mammal-like reptiles and large amphibians disappeared, as well as early dinosaur groups. In the oceans, this event eliminated conodonts and nearly annihilated corals, ammonites, brachiopods and bivalves. In the Southern Hemisphere, the vegetation turnover consisted in the replacement to Alisporites (corystosperm)-dominated assemblage to a Classopollis (cheirolepidiacean)-dominated one. But there was no mass extinction of European terrestrial plants during the TJB. The majority of genera and a high percentage of species still existed in its later stages, and replacement seems to have been local, explainable as a typical reaction to an environmental disturbance. In Greenland, for example, the replacement of Triassic wide-leaved forms with Jurassic narrow-leaved forms was linked to the reaction of plants to increased wildfire. In Sweden, wildfire in the late Rhaetian and early Hettangian caused large-scale burning of conifer forests and ferns, and the appearance of new swampy vegetation. In Austria and the United Kingdom, conifers and seed ferns were replaced by ferns, club mosses and liverworts. In Hungary, there was a high spike of ferns and conifers at the TJB, followed by a sudden decrease in the number of ferns along with an increasing share of swamp-inhabiting conifers.

Although certain taxa/families indeed became extinct by the end of the Triassic (e.g. Peltaspermales), the floral changes across Europe were rather a consequence of local changes in topography.

References:

Maria Barbacka, Grzegorz Pacyna, Ádam T. Kocsis, Agata Jarzynka, Jadwiga Ziaja, Emese Bodor , Changes in terrestrial floras at the TriassicJurassic Boundary in Europe, Palaeogeography, Palaeoclimatology, Palaeoecology (2017), doi: 10.1016/j.palaeo.2017.05.024

S. Lindström, Palynofloral patterns of terrestrial ecosystem change during the end-Triassic event — a review, Geol. Mag., 1–23 (2015) https://doi.org/10.1017/S0016756815000552

Van de Schootbrugge, B., Quan, T.M., Lindström, S., Püttmann, W., Heunisch, C., Pross, J., Fiebig, J., Petschick, R., Röhling, H.-G., Richoz, S., Rosenthal, Y., Falkowski, P. G., 2009. Floral changes across the Triassic/Jurassic boundary linked to flood basalt volcanism. Nat. Geosci. 2, 589–594. doi: 10.1038/NGEO577.

N.R. Bonis, W.M. Kürschner, Vegetation history, diversity patterns, and climate change across the Triassic/Jurassic boundary, Paleobiology, 8 (2) (2012), pp. 240–264 https://doi.org/10.1666/09071.1

Introducing Isaberrysaura

Isaberrysaura skull in lateral view and maxillary teeth (Adapted from Salgado et al., 2017)

Isaberrysaura mollensis gen. et sp. nov. is the first dinosaur recovered in the marine-deltaic deposits of the Los Molles Formation (Neuquén Province, Argentina), and the first neornithischian dinosaur known from the Jurassic of South America. So far, the South American record of Jurassic ornithischian dinosaurs was limited to a few specimens belonging to Heterodontosauriformes, a clade of small-sized forms that survived in Europe up to the Early Cretaceous. The name Isaberrysaura is derived from “Isa Berry” (Isabel Valdivia Berry, who reported the initial finding) and the Greek word “saura” (lizard).

The holotype of Isaberrysaura is an incomplete articulated skeleton with an almost complete skull, and a partial postcranium consisting of 6 cervical vertebrae, 15 dorsal vertebrae, a sacrum with a partial ilium and an apparently complete pubis, 9 caudal vertebrae, part of a scapula, ribs, and unidentifiable fragments. One of the most notable features of the discovery is the presence of permineralized seeds in the middle-posterior part of the thoracic cavity. The seeds were assigned to the Cycadales (Zamiineae) on the basis of a well-defined coronula in the micropylar region. The findings suggest the hypothesis of interactions (endozoochory) between cycads and dinosaurs, especially in the dispersion of seeds.

Gut content of Isaberrysaura mollensis gen. et sp. nov. (a–c), seeds of cycads (c), and other seeds (s); rib (r). From Salgado et al., 2017

The cranium of Isaberrysaura is reminiscent of that of the thyreophorans. The skull is estimated to be 52 cm long and 20 cm wide across the orbits. The jugal is triradiate and the nasals are ~20 cm long. There are two supraorbital bones; one is elongated (~10 cm), as in stegosaurs, and the other element interpreted as a posterior supraorbital is located on the posterior margin of the orbit. It has at least six premaxillary teeth, and there is no diastema between the premaxillary and the maxillary tooth row. Despite the many similarities between Isaberrysaura and the thyreophorans, the phylogenetic analysis indicates that Isaberrysaura is a basal ornithopod, suggesting that both Thyreophora and neornithischians could have achieved significant convergent features.

References:

Salgado, L. et al. A new primitive Neornithischian dinosaur from the Jurassic of Patagonia with gut contents. Sci. Rep. 7, 42778; doi: 10.1038/srep42778 (2017)

Wenupteryx uzi, a Jurassic pterosaur from Patagonia.

Wenupteryx uzi, photograph of the slab. From Codorniu-Gasparini 2013.

Wenupteryx uzi, photograph of the slab. From Codorniu-Gasparini 2013.

By the Mid-Jurassic, Gondwana, the southern margen of supercontinent Pangea started to break up in different blocks: Antarctica, Madagascar, India, and Australia in the east, and Africa and South America in the west. During this period pterosaurs had a worldwide distribution, but their known record is markedly biased toward the northern hemisphere. For example, the ‘Solnhofen Limestone’ beds in Germany yielded important pterosaur specimens, mostly members of the genera Pterodactylusand Rhamphorhynchus. Other famous fossil-bearing deposits are from North America, and from the Tiaojishan Formation in China.

In contrast, the fossil remains of pterosaurs from Jurassic sediments are very scarce in the southern hemisphere. The oldest record comes from the Middle Jurassic of Patagonia, in the Cañadon Asfalto Formation, which is mainly composed of lacustrine deposits.

Wenupteryx uzi, reconstruction from Codorniú 2013.

Wenupteryx uzi, reconstruction from Codorniú 2013.

The most complete pterosaur known so far is Wenupteryx uzi described by Laura Codorniu and Zulma Gasparini. In the Mapuche Languaje, Wenu means “sky” and uzi means “fast”.

Wenupteryx uzi, is a small pterosaur . The bones recovered so far are a nearly complete post-cranial skeleton,which includes: some cervical and dorsal vertebrae; a few thoracic ribs, a proximal right-wing (humerus, ulna and radius, right metacarpal IV, pteroid), a more complete left-wing and hindlimb bones. This pterosaurs has a wingspan approaching 1-10 m.
Based on the presence of some characters, like the depressed neural arch of the mid-series cervicals, with a low neural spine and elongate mid-series cervicals. Wenupteryx uzi is closely related to the Euctenochasmatia, which matches with Unwin’s phylogeny (Unwin, 2003).


References:

Laura Codorniú and Zulma Gasparini (2013). «The Late Jurassic pterosaurs from northern Patagonia, Argentina». Earth and Environmental Science Transactions of the Royal Society of Edinburgh 103 (3–4):  pp. 399–408. doi:10.1017/S1755691013000388.

Brief paleontological history of planktonic foraminifera.

neoglobo

Neogloboquadrina dutertrei. (Credit: Dr Kate Darling).

Planktonic foraminifera made their first appearance in the Late Triassic. Although, identifying the first occurrence of planktonic foraminifera is complex, with many suggested planktonic forms later being reinterpreted as benthic. They are present in different types of marine sediments, such as carbonates or limestones, and are excellent biostratigraphic markers.

Their test are made of  globular chambers composed of secrete calcite or aragonite, with no internal structures and  different patterns of chamber disposition: trochospiral, involute trochospiral and planispiral growth. During the Cenozoic, some forms exhibited supplementary apertures or areal apertures. The tests also show perforations and a variety of surface ornamentations like cones, short ridges or spines.

The phylogenetic evolution of planktonic foraminifera are closely associated with global and regional changes in climate and oceanography.

planktonic foraminifera evolution

The evolution of early planktonic foraminifera (From Boudagher-Fadel, 2013)

All species of Late Triassic and Jurassic planktonic foraminifera are members of the superfamily Favuselloidea. They present a test composed by aragonite, with microperforations, and sub-globular adult chambers. After the major End Triassic event, the Jurassic period saw warm tropical greenhouse conditions worldwide. The surviving planktonic foraminifera were usually dominated by small globular forms.

It was suggested  that a second transition from a benthic to a planktonic mode of life took place at the Jurassic, which occurred under conditions similar to those that triggered planktonic speciation in the Late Triassic (hot and dry global climate, and low sea levels).

During the Cretaceous,  the favusellids must have made the transition from being aragonitic to calcitic.  Also, in the Late Aptian there was a significant number of planktonic foraminiferal extinctions, but these were compensated by the establishment of a large number of new genera at the Aptian–Albian boundary.

Planktonic foraminifera from the Sargasso Sea in the North Atlantic Ocean. (Photograph courtesy Colomban de Vargas, EPPO/SBRoscoff.)

Planktonic foraminifera from the Sargasso Sea in the North Atlantic Ocean. (Photograph courtesy Colomban de Vargas, EPPO/SBRoscoff.)

The Paleogene assemblage of planktonic foraminifera was derived from the few species that survive the mass extinction event at the end of the Cretaceous.

In the Early Miocene, the planktonic foraminifera were most abundant and diverse in the tropics and subtropics, and after the Mid-Miocene Climatic Optimum, many species were adapted to populate temperate and sub-polar oceans.

During the Middle and Late Pliocene, the final closure of the Central American seaway, changed oceanic circulation and drove a significant number of species extinctions. Most modern, living species originated in the Pliocene and Pleistocene.

References:

Armstrong, H. A., Brasier, M. D., 2005. Microfossils (2nd Ed). Blackwell, Oxford.

Boudagher-Fadel, MK; (2013) Biostratigraphic and Geological Significance of Planktonic Foraminifera. (2nd ed.)