A brief introduction to the Carnian Pluvial Episode.

Early-late Carnian (Late Triassic) palaeogeographic reconstruction showing some of the main vertebrate-bearing units (From Bernardi et al. 2018)

Dinosaurs likely originated in the Early to Middle Triassic. The Manda beds of Tanzania yielded the remains of the possible oldest dinosaur, Nyasasaurus parringtoni, and Asilisaurus, a silesaurid (the immediate sister-group to Dinosauria). However the oldest well-dated identified dinosaurs are from the late Carnian of the lower Ischigualasto Formation in northwestern Argentina, dated from 231.4 Ma to 225.9 Ma. The presence of dinosaurs, such as Panphagia, Eoraptor, and Herrerasaurus support the argument that Dinosauria originated during the Ladinian or earlier and that they were already well diversified in the early Carnian. Similarly, the Santa Maria and Caturrita formations in southern Brazil preserve basal dinosauromorphs, basal saurischians, and early sauropodomorphs. In North America, the oldest dated occurrences of vertebrate assemblages with dinosaurs are from the Chinle Formation. Two further early dinosaur-bearing formations, are the lower (and upper) Maleri Formation of India and the Pebbly Arkose Formation of Zimbabwe. These skeletal records of early dinosaurs document a time when they were not numerically abundant, and they were still of modest body size (Eoraptor had a slender body with an estimated weight of about 10 kilograms).

Trace fossil evidence suggests that the first dinosaur dispersal in the eastern Pangaea is synchronous with an important climate-change event named the “Carnian Pluvial Episode” (CPE) or “Wet Intermezzo”, dated to 234–232 Ma.

Skeleton of Eoraptor lunensis (PVSJ 512) in left lateral view. Scale bar equals 10 cm. From Sereno et al., 2013.

The Late Triassic is marked by a return to the hothouse condition of the Early Triassic, with two greenhouse crisis that may also have played a role in mass extinctions. Isotopic  records suggest  a global carbon cycle perturbation during the Carnian that was coincident with complex environmental changes and biotic turnover.

The CPE is often described as a shift from arid to more humid conditions (global warming, ocean acidification, mega-monsoonal conditions, and a generalised increase in rainfall). In the marine sedimentary basins of the Tethys realm, an abrupt change of carbonate factories and the establishment of anoxic conditions mark the beginning of the climate change. The CPE also marks the first massive appearance of calcareous nannoplankton, while groups, like bryozoans and crinoids, show a sharp decline during this event.

Palynological association from the Heiligkreuz Formation provide information on palynostratigraphy and palaeoclimate during the last part of the Carnian Pluvial Event (CPE). From Roghi et al., 2014

On land, palaeobotanical evidence shows a shift of floral associations of towards elements more adapted to humid conditions (the palynological record across the CPE suggest at least 3–4 discrete humid pulses). Several families and orders make their first appearance during the Carnian: bennettitaleans, modern ferns, and conifer families (Pinaceae, Araucariaceae, Cheirolepidaceae). The oldest biological inclusions found preserved in amber also come from the Carnian; and key herbivorous groups such as dicynodonts and rhynchosaurs, which had represented 50% or more of faunas, disappeared, and their places were taken by dinosaurs.

Despite the global significance of the CPE,  the trigger of the environmental change  is still disputed. Volcanic emissions from the Wrangellia igneous province and the dissociation of methane clathrates could be linked to the CPE. It seems that the combination of that events  would be the most likely explanation for the substantial shift of the C isotope excursion observed at the CPE.

 

References:

Massimo Bernardi et al. Dinosaur diversification linked with the Carnian Pluvial Episode, Nature Communications (2018). DOI: 10.1038/s41467-018-03996-1

Miller et al., Astronomical age constraints and extinction mechanisms of the Late Triassic Carnian crisis, Scientific Reports | 7: 2557 | (2017) DOI:10.1038/s41598-017-02817-7

Rogui et al. Field trip to Permo-Triassic Palaeobotanical and Palynological sites of the Southern Alps, Geo.Alp. 11. 29-84. (2014)

Paul C. Sereno, Ricardo N. Martínez & Oscar A. Alcober (2013) Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha),Journal of Vertebrate Paleontology, 32:sup1, 83-179, DOI: 10.1080/02724634.2013.820113

Advertisements

Before Jurassic Park: The study of ancient DNA.

A tick entangled in a dinosaur feather (From Peñalver et al., 2017)

We all know the story. In the early 80’s, John Hammond, a shady entrepreneur, created the ultimate thematic park by cloning dinosaurs from preserved DNA in mosquitoes entombed in amber. The idea, as Michael Crichton acknowledged, was not new.

In 1982, entomologist George Poinar and electron microscopist Roberta Hess at University of California,  found exceptional evidence for the organic preservation of a 40-million-year-old fly in Baltic amber. They saw intact cell organelles, such as nuclei, and mitochondria, and wondered whether these results were replicable. After a letter from Poinar to a colleague, they received, a week later,  a 70–80 million-year-old wasp in Canadian amber. The wasp also revealed evidence of cellular structure. The realization that amber was a special source of cellular preservation caused them to wonder if it could be a source of molecular preservation, too.

Quagga mare at London Zoo, 1870, the only specimen photographed alive

Poinar and Hess joined forces with Allan Wilson, Professor of Biochemistry at Berkeley, and Russell Higuchi, a molecular biologist and postdoctoral researcher in Wilson’s lab. A year later, they embarked on the first experiment to test ideas about the preservation and extraction of DNA from insects in ancient amber. Poinar selected eight specimens that would potentially offer optimal preservation of DNA. In two of the eight insects were signs of DNA, but no hybridization experiments were done to determine whether the results were due to human contamination.

Soon, Wilson and Higuchi turned their attention to the quagga, a subspecies of plains zebra that went extinct in 1883. The study, lead by Russell Higuchi, used two short mitochondrial DNA sequences from the muscle and connective tissue from a 140 year-old quagga from the Natural History Museum in Mainz, Germany, and confirmed that the quagga was more closely related to zebras than to horses.
The survival of DNA in quagga tissue and in an Egyptian mummy created waves among the scientific community, and in the autumn of 1984, Wilson and his lab submitted to the National Science Foundation (NSF), the first official research proposal to search for DNA in ancient and extinct organisms. They wrote: “This is the first proposal to study the possible utility of DNA to paleontology. If clonable DNA is present in many fossil bones and teeth and in insects included in amber, a new field, molecular paleontology, can arise.”

 

Reference:

Jones, E.D., Ancient DNA: a history of the science before Jurassic Park; Studies in History and Philosophy of Biol & Biomed Sci (2018), https://doi.org/10.1016/j.shpsc.2018.02.001

Poinar, G. O., & Hess, R. (1982). Ultrastructure of 40-million-year-old insect tissue.
Science, 215(4537), 1241–1242. DOI: 10.1126/science.215.4537.1241

Higuchi R, Bowman B, Freiberger M, Ryder OA, Wilson AC. DNA sequences from the quagga, an extinct member of the horse family. Nature. 1984;312:282–284. doi: 10.1038/312282a0.

Peñalver, E. et al; Ticks parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages, Nature Communications volume 9, Article number: 472 (2017)
doi:10.1038/s41467-018-02913-w

Introducing Tratayenia rosalesi

A speculative reconstruction 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. The enigmatic nature of this group has been a matter of discussion since the description of the first megaraptoran, Megaraptor namunhaiquii in 1990s . 

The phylogenetic position of Megaraptora is still controversial. But despite the lack of consensus, megaraptorans themselves remain a well-supported, monophyletic clade. Now, a new megaraptoran theropod dinosaur from the Upper Cretaceous of the Neuquén Group, sheds light on on these enigmatic predators.

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

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.
The holotypic specimen (MUCPv 1162) consists of a well-preserved, mostly articulated series of dorsal and sacral vertebrae, two partial dorsal ribs, the right ilium, pubis and ischium fragments. Tratayenia is the first megaraptoran that unequivocally preserves the complete sequence of sacral vertebrae. The dorsal and sacral centra and neural arches of Tratayenia are unfused, suggesting that the specimen was a subadult at the time of death.

The elevated pneumaticity and morphological resemblance of the axial and pelvic elements of Tratayenia with Aerosteon riocoloradensis and Murusraptor barrosaensis suggests a particularly close relationships between these three taxa. 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.

 

References:

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.

Novas, F.E., 1998. Megaraptor namunhuaiquii gen. et. sp. nov., a large-clawed, Late Cretaceous Theropod from Argentina. Journal of Vertebrate Paleontology 18, 4-9.

Forgotten women of Paleontology: Elizabeth Anderson Gray

Elizabeth Anderson Gray (1831 – 1924) Image: The Trustees of the Natural History Museum, London

The nineteen century was the “golden age” of Geology. The Industrial Revolution ushered a period of canal digging and major quarrying operations. These activities exposed sedimentary strata and fossils, and the study of the Earth became central to the economic and cultural life of  Great Britain. The most popular aspect of geology was  the collecting of fossils and minerals and the nineteenth-century geology, often perceived as the sport of gentlemen,was in fact, “reliant on all classes”. Women were free to take part in collecting fossils and mineral specimens, and they were allowed to attend lectures but they were barred from membership in scientific societies. It was common for male scientists to have women assistants, but most of them went unacknowledged and become lost to history.  However, some women found the way to avoid that fate. One of those women was Elizabeth Anderson Gray.

Born in Alloway, Ayrshire, on February 21, 1831, Elizabeth Anderson Gray  is considered as one of the foremost Scottish fossil collectors of the late 19th and early 20th centuries. She had little formal schooling but as a girl joined her father, Thomas Anderson, in his hobby of fossil collecting. In 1856, she married a Glasgow banker, Robert Gray, co-founder of The Natural History Society of Glasgow. She took a geology course for women at Glasgow University and she trained her children to document their findings too. She was also friend of Jane Longstaff, a British malacologist and expert in fossil gastropods of the Palaeozoic. The Gray collections, considered important in studies of Ordovician fauna, were sold to institutions. In 1920 a major part of the collection was acquired by the British Museum for £2250. Charles Lapworth, in his work on the ‘Girvan Succession’ referred extensively to E. Gray’s collection in his stratigraphical correlations.

In 1900, Elizabeth Gray was made an honorary member of the Geological Society of Glasgow for her many contributions, and in 1903, she was awarded the Murchison geological fund in recognition of her skilful services to geological science. She continued gathering fossils until her death on 1924.

 

References:

BUREK, C. V. & HIGGS, B. (eds) The Role of Women in the History of Geology. Geological Society, London, Special Publications, 281, 1–8. DOI: 10.1144/SP281.1.

M. R. S. Creese (2007), Fossil hunters, a cave explorer and a rock analyst: notes on some early women contributors to geology, Geological Society, London, Special Publications, 281, 39-49. https://doi.org/10.1144/SP281.3

 

An early juvenile enantiornithine specimen from the Early Cretaceous of Spain

The slab and counterslab of MPCM-LH-26189

Mesozoic remains of juvenile birds are rare. To date, the only records are from the Early Cretaceous of China and Spain, from the mid-Cretaceous of  Myanmar, and from the Late Cretaceous of Argentina and Mongolia. The most recent finding from the Early Cretaceous of Las Hoyas, Spain, provide an insight into the osteogenesis of the Enantiornithes, the most abundant clade of Mesozoic birds. Previous records of Enantiornithes from the Las Hoyas fossil site include: Eoalulavis hoyasi, Concornis lacustris, and Iberomesornis romerali.

The latest specimen, MPCM-LH-26189, a nearly complete and largely articulated skeleton (only the feet, most of its hands, and the tip of the tail are missing), is very small. The specimen died around the time of birth, a crucial moment to study the osteogenesis in birds. The skull, is partially crushed, and is large compared to the body size. The braincase is fractured. The frontals and the parietals form a uniformly curved cranial vault. The cerebrocast shows a very slight inflation, suggesting that the cerebral anatomy of MPCM-LH-26189 falls in between that of the Archaeopteryx, and the putative basal ornithurine Cerebavis, whose telencephalic expansion is close to most extant birds. The cervical series is composed of 9 vertebrae. There are 10  thoracic vertebrae, and the sacrum appears to be composed of 5–6 vertebrae. The prezygapophyses of the mid-thoracic vertebrae extend beyond the cranial articular surface. The thoracic ribs are joint to the thoracic vertebrae. The two coracoids, the furcula, and three sternal ossifications are preserved. The furcula is Y-shapped. Both humeri, ulnae, and radii are also preserved.

Reconstruction of MPCM-LH-26189 by Raúl Martín

The osteohistological analysis of the left humerus shows a dense pattern of longitudinal grooves. Those grooves correspond to primary cavities, which open onto the surface of the cortex in young and fast-growing bone. The shaft of the tibia and radius show very-thin cortices. In addition,  the primary nature of the vascularisation, the round shape of the osteocytes lacunae and the uneven peripheral margin of the medullary cavity (with no endosteal bone), strongly suggests that the bone was actively growing when the bird died.

Enantiornithines show a mosaic of characters, reflecting their intermediate phylogenetic position between the basal-pygostylians and modern bird. In this clade, the sternum adopts an elaborate morphology, and in adult Enantiornithes, no more than eight free caudal vertebrae precede the pygostyle. The differences observed in the ossification of the sternum and the number of free caudal vertebrae in MPCM-LH-26189, when it compared to other juvenile enantiornithines, reveal a clade-wide asynchrony in the sequence of ossification of the sternum and tail, suggesting that the developmental strategies of these basal birds may have been more diverse than previously thought.

References:

Fabien Knoll, et al., “A diminutive perinate European Enantiornithes reveals an asynchronous ossification pattern in early birds,” Nature Communications, volume 9, Article number: 937 (2018) doi:10.1038/s41467-018-03295-9

Chiappe, L. M., Ji, S. & Ji, Q. Juvenile birds from the Early Cretaceous of China: implications for enantiornithine ontogeny. Am. Mus. Novit. 3594, 1–46 (2007).

 

 

Forgotten women of Paleontology: Carlotta Joaquina Maury

Carlotta Joaquina Maury (January 6, 1874 – January 3, 1938)

In the 18th and 19th centuries women’s access to science was limited. Early female scientists were often born into influential families, like Grace Milne, the eldest child of Louis Falconer and sister of the eminent botanist and palaeontologist, Hugh Falconer. Unfortunately, their contribution has not been widely recognised by the public or academic researchers. Women collected fossils and mineral specimens, and were allowed to attend scientific lectures, but they were barred from membership in scientific societies. By the 1880, in the United States, geology was a marginal subject in the curricula of the early women’s colleges until an intense programme was started at Bryn Mawr College, a decade later.

Carlotta Joaquina Maury was born on January 6, 1874 in Hastings-on-Hudson, New York. She was the youngest  sister of astronomer Antonia Maury, who worked at the Harvard College Observatory as one of the so-called Harvard Computers. She was also the granddaughter of John William Draper and a niece of Henry Draper, both pioneering astronomers. Maury maternal grandmother was Antonia Coetana de Paiva Pereira, member of Portuguese nobility serving at the court of Emperor Dom Pedro I of Brazil, a connection which had and important influence on her career.

Harvard Computers at work, including Henrietta Swan Leavitt (1868–1921), Annie Jump Cannon (1863–1941), Williamina Fleming (1857–1911), and Antonia Maury (1866–1952).

She was educated at Radcliffe College from 1891 to 1894. Influenced by Elizabeth Agassiz, co-founder and first president of Radcliffe College, Maury attended Cornell University, where she obtained a PhD in 1902, making her one of the first women to receive her PhD in paleontology. Her mentor was Gilbert Harris, who founded the scientific journal Bulletins of American Paleontology.

Before completing her PhD, she spent a year at the Sorbonne. After teaching in several universities, she investigated microfossils in drilling samples along the Texas and Louisiana coasts and was given an official title as a paleontologist for the Louisiana Geological Survey. In 1910, Maury was recruited to be the paleontologist for oil geologist A.C. Veatch’s year-long geological expedition to Venezuela, a study funded by the General Asphalt Company of Philadelphia. Her discovery in Trinidad of Old Eocene beds with fossils faunas related to those of Alabama and the Pernambuco region of Brazil was the first finding of Old Eocene in the entire Caribbean and northern South America region.

Carlotta Maury at the Palaeontology Laboratory in Cornell. (From Arnold, 2009)

After a short break for teaching at Huguenot College in Wellington, South Africa, Maury returned to the Caribbean in 1916 as the leader of the “Maury Expedition” to the Dominican Republic, during a period of violent political upheaval on the island. The results  – type sections and descriptions of fossils, including more than 400 new species – are the foundation for the international Dominican Republic Project, a multi-disciplinary research effort that aims s to understand evolutionary change in the Caribbean from the Miocene era to the present day.

Her reputation for being extremely efficient and energetic helped her to defy the prejudice against professional women at the time. She was a consulting palaeontologist and stratigrapher to Royal Dutch Shell’s Venezuela Division for more than 20 year, and one of the official palaeontologists with the Geological and Mineralogical Service of Brazil. In 1925, she published “Fosseis Terciarios do Brazil with Descripção de Nova Cretaceas Forms” where she described numerous species of mollusks from the northeastern coast, performing the stratigraphic correlation of these faunas with similar faunas of the Caribbean and Gulf of Mexico.

C. Maury in 1916, Dominican Republic.

Maury was fellow of the Geological Society of America, and of the American Geographical Society. During the last decade of her life, she dedicated to publishing her consulting reports. Her last report about the Pliocene fossils of Acre, Brazil, appeared in 1937, shortly before her death. The same year she was elected member of the Brazilian Academy of Sciences.
Carlotta Maury died January 3, 1938 in Yonkers, New York.

References:

Lois Arnold (2009), The Education and Career of Carlotta J. Maury: Part 1., Earth Sciences History 28.2 (2009): 219-244 https://doi.org/10.17704/eshi.28.2.343vu112512w8170 

M. R. S. Creese (2007), Fossil hunters, a cave explorer and a rock analyst: notes on some early women contributors to geology, Geological Society, London, Special Publications, 281, 39-49. https://doi.org/10.1144/SP281.3

Burek, C.V. and B. Higgs, eds. (2007) The Role of Women in the History of Geology (London: Geological Society).

 

Volcanism, the Chicxulub impact and the K-Pg event.

The Deccan traps

It was the best of times. It was the worst of times. The end of the Mesozoic era at ca. 66 million years ago (Ma) is marked by one of the most severe biotic crisis in Earth’s history: the Cretaceous-Paleogene (K-Pg) mass extinction. During the event, three-quarters of the plant and animal species on Earth disappeared, including non-avian dinosaurs, other vertebrates, marine reptiles and invertebrates, planktonic foraminifera and ammonites. Marine ecosystems lost about half of their species while freshwater environments shows low extinction rates, about 10% to 22% of genera.

Two events were linked to this mass extinction: the eruption of the Deccan Traps large igneous province, and the Chicxulub meteorite impact. Early work speculated that the Chicxulub impact triggered large-scale mantle melting and initiated the Deccan flood basalt eruption. Precise dating of both, the impact and the flood basalts, show that the earliest eruptions of the Deccan Traps predate the impact. But, the Chicxulub impact, and the enormous Wai Subgroup lava flows of the Deccan Traps continental flood basalts appear to have occurred very close together in time. Recent studies suggest a possible association between the Chicxulub impact and variations in the progression of Deccan Traps eruptions. Seismic modeling indicates that the impact could have generated seismic energy densities of order 0.1–1.0 J/m3 throughout the upper ∼200 km of Earth’s mantle, sufficient to trigger volcanic eruptions worldwide.

Gravity anomaly map of the Chicxulub impact structure (From Wikimedia Commons)

The oceanic crust records the history of temporal variations in seafloor magmatism continuously and at high resolution through geologic time. Around the time of the Chicxulub impact, 23,000 to 230,000 cubic miles of magma erupted out of the mid-ocean ridges, all over the globe. One of the largest eruptive events in Earth’s history. This pulse of global marine volcanism played an important role in the environmental crisis at the end of the Cretaceous, through magmatism by extruding large volumes of basalt and releasing volcanic gases or through enhanced hydrothermal venting driven by magmatic intrusion. Marine volcanism also provides a potential source of oceanic acidification.

The Chicxulub impact released an estimated energy equivalent of 100 teratonnes of TNT and produced high concentrations of dust, soot, and sulfate aerosols in the atmosphere. The decrease of sunlight caused a drastic short-term global reduction in temperature (15 °C on a global average, 11 °C over the ocean, and 28 °C over land). While the surface and lower atmosphere cooled, the tropopause became much warmer, eliminate the tropical cold trap and allow water vapor mixing ratios to increase to well over 1,000 ppmv in the stratosphere. Those events accelerated the destruction of the ozone layer. During this period, UV light was able to reach the surface at highly elevated and harmful levels.

 

References:

Joseph S. Byrnes and Leif Karlstrom, Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism, Sci Adv 4 (2), eaao2994, DOI: 10.1126/sciadv.aao2994

Charles G. Bardeen, Rolando R. Garcia, Owen B. Toon, and Andrew J. Conley, On transient climate change at the Cretaceous−Paleogene boundary due to atmospheric soot injections, PNAS 2017 ; published ahead of print August 21, 2017 DOI: 10.1073/pnas.1708980114

The oldest Archaeopteryx

Overview of the skeleton of the new Archaeopteryx specimen (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. On August 15, 1861, German paleontologist Hermann von Meyer wrote a letter to the editor of the journal Neues Jahrbuch für Mineralogie, Geologie und Palaeontologie, where he made the first description of the fossil. On on September 30, 1861, he wrote a new letter:  “I have inspected the feather from Solenhofen closely from all directions, and that I have come to the conclusion that this is a veritable fossilisation in the lithographic stone that fully corresponds with a birds’ feather. I heard from Mr. Obergerichtsrath Witte, that the almost complete skeleton of a feather-clad animals had been found in the lithographic stone. It is reported to show many differences with living birds. I will publish a report of the feather I inspected, along with a detailed illustration. As a denomination for the animal I consider Archaeopteryx lithographica to be a fitting name”. 

The near complete fossil skeleton found in a Langenaltheim quarry near Solnhofen – with clear impressions of wing and tail feathers –  was examined by Andreas Wagner, director of the Paleontology Collection of the State of Bavaria in Germany. He reached the conclusion that the fossil was a reptile, and gave it the name Griphosaurus. He wrote: “Darwin and his adherents will probably employ the new discovery as an exceedingly welcome occurrence for the justification of their strange views upon the transformations of animals.” In later editions of The Origin of Species, Darwin indeed mention the Archaeopteryx“That strange bird, Archaeopteryx, with a long lizardlike tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws . . . Hardly any recent discovery shows more forcibly than this, how little we as yet know of the former inhabitants of the world.”

Archaeopteryx lithographica, Archaeopterygidae, Replica of the London specimen; Staatliches Museum für Naturkunde Karlsruhe, Germany. From Wikimedia Commons

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 new specimen was discovered by a private collector. Although it was registered as German national cultural heritage, which guarantees its permanent availability, the specimen remains in private hands (Datenbank National Wertvollen Kulturgutes number DNWK 02924).

The new specimen is preserved as a largely articulated skeleton. However, 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.

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

The postcranial skeleton was affected by breakage and loss of elements prior to or at the time of discovery. The sacral region, and the caudal vertebrae are very poorly preserved. Several dorsal ribs are preserved, and gastralia ribs are present in the thoracic region and the abdominal region. The shoulder girdle comprises the scapula, coracoid and furcula. Both humeri are poorly preserved. Parts of the phalanges are, largely poorly, preserved, and they do not show much detail. The pubic shafts are slender and very slightly flexed posteroventrally, an as in all specimens of Archaeopteryx, the distal end of the ischium is bifurcated. The femora are also poorly preserved and largely collapsed. Both tibiae are preserved in articulation with the fibulae and the proximal tarsals. The digits of the feet are complete on both sides, but partially overlapping.

Until recently, the referral of new specimens from the Solnhofen Archipelago to the genus Archaeopteryx, seems unproblematic, but the re-examination of the fourth (Haarlem) specimen of Archaeopteryx, and the discovery in the last years of specimens from the Late Jurassic of China that are similar to Archaeopteryx, raises the question if the specimens referred to Archaeopteryx represent a monophyletic taxon.

 

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

Foth C, Rauhut OWM. 2017. Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs. BMC Evolutionary Biology 17:236 https://doi.org/10.1186/s12862-017-1076-y

MEYER v., H. (1861): Archaeopterix lithographica (Vogel-Feder) und Pterodactylus von Solenhofen. Neues Jahrbuch fur Mineralogie, Geognosie, Geologie und Petrefakten-Kunde. 6: 678-679

Wellnhofer Peter, A short history of research on Archaeopteryx and its relationship with dinosaurs, Geological Society, London, Special Publications, 343:237-250, doi:10.1144/SP343.14, 2010

Our once and future oceans

Earth is the only planet in our Solar System with high concentrations of gaseous diatomic oxygen. Simultaneously, this unique feature of Earth’s atmosphere has allowed the presence of an ozone layer that absorbed UV radiations. The progressive oxygenation of the atmosphere and oceans was sustained by an event of high organic carbon burial, called the Paleoproterozoic Lomagundi Event (ca. 2.3-2.1 billion years ago), which lasted well over 100 million years.

Oxygen is fundamental to life, and influences biogeochemical processes at their most fundamental level. But the oxygen content of Earth has varied greatly through time. In Earth history there have been relatively brief intervals when a very significant expansion of low-oxygen regions occurred throughout the world’s oceans. The discovery of black shales at many drill sites from the Atlantic, Indian, and the Pacific Ocean led to the recognition of widespread anoxic conditions in the global ocean spanning limited stratigraphic horizons. In 1976, S. O. Schlanger and H. C. Jenkyns termed these widespread depositional black shale intervals as “Oceanic Anoxic Events”. This was one of the greatest achievement of the DSDP (Deep Sea Drilling Project).

Corals one of the most vulnerable creatures in the ocean. Photo Credit: Katharina Fabricius/Australian Institute of Marine Science

Human activity is a major driver of the dynamics of Earth system. After the World War II, the impact of human activity on the global environment dramatically increased. Over the past 50 years, open ocean lost an estimated 2%, or 4.8 ±2.1 petamoles (77 billion metric tons), of its oxygen, and ocean oxygen minimum zones (OMZs) have expanded by an area about the size of the European Union. Deoxygenation is linked to other ocean stressors, including warming and acidification.

Ocean warming reduces the solubility of oxygen, and raises metabolic rates accelerating the rate of oxygen consumption. Warming also influence on thermal stratification and indirectly enhances salinity driven stratification through its effects on ice melt and precipitation. The increased stratification alters the mainly wind-driven circulation in the upper few hundred meters of the ocean and slows the deep overturning circulation. Intensified stratification may account for the remaining 85% of global ocean oxygen loss by reducing ventilation nd by affecting the supply of nutrients controlling production of organic matter and its subsequent sinking out of the surface ocean. Warming is predicted to exacerbate oxygen depletion in coastal systems through mechanisms similar to those of the open ocean.

Time scale [Gradstein et al., 2005] illustrating the stratigraphic position and nomenclature of OAEs (From Jenkyns, 2010).

The geological records show that large and rapid global warming events occurred repeatedly during the course of Earth history. The growing concern about modern climate change has accentuated interest in understanding the causes and consequences of these ancient abrupt warming events. The early Toarcian Oceanic Anoxic Event  (T-OAE; ∼183 mya) in the Jurassic Period is associated with a major negative carbon isotope excursion, mass extinction, marine transgression and global warming. Besides, the marked expansion of the oxygen minimum zone over the last decades, is quite similar to the model originally invoked for the genesis of Cretaceous OAEs. The better understanding of the Mesozoic ocean-climate system and the formation of OAEs would help us to predict environmental and biotic changes in a future greenhouse world.

References:

DENISE BREITBURG, LISA A. LEVIN, ANDREAS OSCHLIES, MARILAURE GRÉGOIRE, FRANCISCO P. CHAVEZ, DANIEL J. CONLEY, VÉRONIQUE GARÇON, DENIS GILBERT, DIMITRI GUTIÉRREZ, KIRSTEN ISENSEE, GIL S. JACINTO, KARIN E. LIMBURG, IVONNE MONTES, S. W. A. NAQVI, GRANT C. PITCHER, NANCY N. RABALAIS, MICHAEL R. ROMAN, KENNETH A. ROSE, BRAD A. SEIBEL, MACIEJ TELSZEWSKI, MORIAKI YASUHARA, JING ZHANG (2018), Declining oxygen in the global ocean and coastal waters, Science, Vol. 359, Issue 6371, DOI: 10.1126/science.aam7240

Jenkyns, H. C. (2010), Geochemistry of oceanic anoxic eventsGeochem. Geophys. Geosyst.11, Q03004, doi:10.1029/2009GC002788.

Holz, M., Mesozoic paleogeography and paleoclimates – a discussion of the diverse greenhouse and hothouse conditions of an alien world, Journal of South American Earth Sciences (2015), doi: 10.1016/j.jsames.2015.01.001

Tennant, J. P., Mannion, P. D., Upchurch, P., Sutton, M. D. and Price, G. D. (2016), Biotic and environmental dynamics through the Late Jurassic–Early Cretaceous transition: evidence for protracted faunal and ecological turnover. Biol Rev. doi:10.1111/brv.12255 

 

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).