Forgotten women of paleontology: Hildegarde Howard

Hildegard Howard with fossil bird from the Rancho La Brea.

The birth of modern science was hostile to women’s participation. The world’s major academies of science were founded in the 17th century: the Royal Society of London (1662), the Paris Académie Royale des Sciences (1666), and the Berlin Akademie der Wissenschaften (1700). Unfortunately, women were not become members of these societies for over 300 years. Yvonne Choquet-Bruhat became the first woman to be elected to the Paris Academy of Science in 1979. Although the Royal Society was less rigid in terms of memberships than the Paris Academy of Science, it was not until 1945 that the first women were admitted as fellows of the Royal Society: the X-ray crystallographer Kathleen Yardley Lonsdale (1903–1971), and biochemist and microbiologist Marjory Stephenson (1885-1948).

Despite the barriers, between 1880 and 1914, some 60 women contributed papers to Royal Society publications. Meanwhile, 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 in the 1890s.

Hildegard Howard measures specimens from the Rancho La Brea Collection. Image from The Natural History Museum of Los Angeles County Archives.

Florence Bascom was one of the pioneers when geological education at universities became available to women. She received her PhD degree from Johns Hopkins University in 1893 by special dispensation, as women were not admitted officially until 1907; while Carlotta Joaquina Maury attended Cornell University, where she became one of the first women to receive her PhD in paleontology in 1902.

When Hildegarde Howard began attending the Southern Branch of the University of California (now known as the University of California at Los Angeles), women were still barred from scientific societies. She was born on April 3, 1901 in Washington D.C., but moved to Los Angeles at the age of 5. Her main interest was journalism, until she met her first biology instructor, Miss Pirie Davidson. In 1921, Hildegarde obtained a part-time job working for Dr. Chester Stock, sorting bones from Rancho La Brea in the basement of the Los Angeles Museum of History, Science and Art (now known as the Natural History Museum of Los Angeles County). One year later, she went to Berkeley to finish her degree.

Dr. Hildegarde Howard, in her office in 1961.Copyright Natural History Museum of Los Angeles County

In 1928, she obtained her Ph.D. degree. Her dissertation, entitled “The Avifauna of Emeryville Shellmound”, became one of her most popular works, and remained as the principal reference of its kind until the appearance of the first edition of Nomina Anatomica Avium in 1979. She obtained a permanent position with the museum in 1929. Although she was a curator, she did not receive that official title until 1938. Through that decade, she wrote twenty-four papers on fossil birds in the American Southwest. She was promoted to the curator of Avian Paleontology in 1944, and she would serve in that role until 1951, when she was promoted to Chief Curator of Science, She became the first woman to receive the Brewster Medal for outstanding research in ornithology in 1953.

Hildegarde Howard officially retired in 1961, although continued research on fossil birds, publishing her last paper in 1992. During her extraordinary career, Dr. Howard described 3 families, 13 genera, 57 species, and 2 subspecies, and remains highly regarded as one of the foremost experts in her field. She died on February 28, 1998.

 

References:

Campbell Jr., Kenneth. 2000c. “In Memoriam, Hildegarde Howard 1901-1998.” The Auk, vol.117, no.3, 775-779.

 

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Introducing Kaijutitan, the strange beast.

The entrance to the town of Rincón de los Sauces.

Since the discovery of dinosaur remains in the Neuquen basin in 1882, Argentina has gained the title of Land of the Giants. The tittle was reinforced by the discoveries of titanosaurs like Argentinosaurus, Dreadnoughtus, Notocolossus, Puertasaurus, and Patagotitan. The study of this diverse group of sauropod dinosaurs embrace an extensive list of important contributions, which started with Richard Lydekker’s pioneering work on Patagonian dinosaurs, and by the classic Friedrich von Huene monograph on Argentinean saurischians and ornithischians.

Titanosaurus were a diverse group of sauropod dinosaurs represented by more than 30 genera, which included all descendants of the more recent common ancestor of Andesaurus and Saltasaurus. The group includes the smallest (e.g. Rinconsaurus, Saltasaurus; with estimated body masses of approximately 6 tonnes) and the largest sauropods known to date. They had their major radiation during the middle Early Cretaceous. The evolution of body mass in this clade is key element to understand sauropod evolution.

 

Cranial elements of MAU-Pv-CM-522/1. From Filippi et al., 2019.

Kaijutitan maui, is the first basal sauropod titanosaur from the Sierra Barrosa Formation (Upper Coniacian, Upper Cretaceous). The holotype (MAU-Pv-CM-522) consists of cranial, axial, and appendicular elements presenting an unique combination of plesiomorphic and apomorphic characters. The generic name Kaijutitan is derived from Kaiju, Japanese word that means “strange beast” or “monster”, and titan, from the Greek “giant”.  The species name refers to the acronym of the Museo Municipal Argentino Urquiza, Rincon de los Sauces, Neuquén, Argentina.

The cranial elements of this specimen include the complete neurocranium (the supraoccipital, exoccipital, left paraoccipital process, left exoccipital-opisthotic-prootic complex, left laterosphenoid and orbitosphoid, and basioccipital-basisphenoid complex). The impossibility of recognizing clear sutures suggest an ontogenetic adult stage of the specimen. One of the most notable autapomorphies exhibited by Kaijutitan is the anterior cervical vertebra with bifid neural spine, a feature usually found in diplodocids and dicraeosaurids. Unfortunately, the femur and humerus of Kaijutitan maui are incomplete, therefore the body mass of this titanosaur can only be estimated by comparison with other titanosauriforms. Kaijutitan would have had a body mass similar or intermediate to that of Giraffatitan (38.000 kg) and Notocolossus (60.398 kg).

 

References:

Filippi, L.S., Salgado, L., Garrido, A.C., A new giant basal titanosaur sauropod in the Upper Cretaceous (Coniacian) of the Neuquén Basin, Argentina, Cretaceous Research, https://doi.org/10.1016/j.cretres.2019.03.008.

Meet Iberodactylus.

Partial rostrum of Iberodactylus andreui. From Holgado et. al, 2019

Pterosaurs were the first flying vertebrates. The group achieved high levels of morphologic and taxonomic diversity during the Mesozoic, with more than 200 species recognized so far. From the Late Triassic to the end of the Cretaceous, the evolution of pterosaurs resulted in a variety of eco-morphological adaptations, as evidenced by differences in skull shape, dentition, neck length, tail length and wing span. Because of the fragile nature of their skeletons the fossil record of pterosaurs is strongly biased towards marine and lacustrine depositional environments.

Pterosaurs have been divided into two major groups: “rhamphorhynchoids” and “pterodactyloids”. Rhamphorhynchoids are characterized by a long tail, and short neck and metacarpus. Pterodactyloids have a much larger body size range, an elongated neck and metacarpus, and a relatively short tail, and ruled the sky from the Late Jurassic to the End Cretaceous.

Comparison of the rostrum of Iberodactylus andreui with a cast of a skull of Hamipterus tianshanensis. From Holgado et al., 2019

The record of Iberian pterosaurs is scarce, but a new taxa from the Lower Cretaceous of Spain reveals an unexpected relationship with Hamipterus tianshanensis from the Lower Cretaceous of China. Iberodactylus andreui gen. et sp. nov., was recovered at Los Quiñones site, close to the village of Obón (Teruel, Spain), at the end of the 1980s by Javier Andreau. The holotype (MPZ-2014/1) consists of the anterior portion of the rostrum (~198 mm in length), and includes a partially preserved premaxillary crest, and a fragment of the maxillary bone with several fragmentary teeth. The specimen preserved its original 3D shape, although exhibits frequent fractured bones, that added to the eroded bone surfaces, reveal an external thing layer of cortical bone of 1.5 mm. The robustness and height of the premaxillary crest, suggest that MPZ-2014/1 may represent a male specimen.

The most striking feature of MPZ-2014/1 is the premaxillary crest. This crest exhibits well-developed elongated, sub-vertical striae and sulci, anteriorly curved, a combination that is quite similar to Hamipterus tianshanensis from the Berriasian-Albian of China. It was suggested that the sulci could be interpreted as a trait related to the attachment of the rhamphotheca, as in the case of some extant birds.

Origin and radiation of the clade Anhangueria during the Early Cretaceous. From Holgado et al., 2019

Phylogenetic analyses indicate that Hamipterus tianshanensis and Iberodactylus andreui gen. et sp. nov. form a monophyletic group, the Hamipteridae fam. nov., that falls within the Anhangueria, sharing with other anhanguerians the presence of a lateral expansion on the rostral tips. Anhanguerians has been recorded elsewhere in the Early Cretaceous of Europe, however Iberodactylus is not closely related to any known European anhanguerian, suggesting that the clade Anhangueria could have ancestral connections to eastern Laurasia.

Other tetrapod lineages are recorded in the Iberian Peninsula with close affinities to Asian faunas. Those lineages include titanosauriforms, crocodyliforms, enanthiornitean birds, and the gobiconodontid mammal Spinolestes xenarthrosus related to Gobiconodon and Repenomamus.

Reference:

Borja Holgado, Rodrigo V. Pêgas, José Ignacio Canudo, Josep Fortuny, Taissa Rodrigues, Julio Company & Alexander W.A. Kellner, 2019, “On a new crested pterodactyloid from the Early Cretaceous of the Iberian Peninsula and the radiation of the clade Anhangueria”, Scientific Reports 9: 4940

The mounting of the cast of Diplodocus carnegii at the Museo de La Plata.

Diplodocus carnegii at the Museo de La Plata, 1912 (From Otero and Gasparini, 2014)

Diplodocus carnegii at the Museo de La Plata, 1912 (From Otero and Gasparini, 2014).

Diplodocus is one of the most popular dinosaurs of all time. The first remains of a Diplodocus were found by Benjamin Mudge and Samuel Wendell Williston, in the Upper Jurassic outcrops of Cañon City, Colorado, United States, in 1877. One year later, Othniel Charles Marsh named the species Diplodocus longus on the basis of remains of the hind limb and tail. The name Diplodocus means ‘double beam’ in reference to the particular two-pronged morphology of the posterior hemal arches. D. carnegii, was discovered in 1899 during an expedition carried out by the Carnegie Museum to the Upper Jurassic Morrison Formation of Wyoming. John Bell Hatcher dedicated the new species of to Andrew Carnegie.

A sketch from the of Diplodocus carnegii, which Carnegie had framed and mounted on a wall at his castle in Scotland.

William Jacob Holland, director of the Carnegie Museum, sent a sketch of the skeleton of Diplodocus to Andrew Carnegie. At the time, the steel tycoon was at his Castle, Skibo, in Sutherland County, Scotland. The King Edward VII of England, saw the sketch and asked Carnegie to give him a specimen for the British Museum of Natural History in London. Holland proposed to Carnegie to make a life-sized replica of D. carnegii to be given to the British Museum of Natural History. On May 12, 1905, the long skeleton was unveiled to a crowd of 300 people, and became an instant star.

Mounting of the cast of Diplodocus carnegii at the Museo de La Plata, Argentina. Arthur Coggeshall and William Holland are second and third from left (Adapted from ‘Caras y Caretas’ magazine, 1912).

Nine replicas of D. carnegii were made and donated to kings and presidents of Europe and Latin America. On November of 1911, Argentinean president Dr. Roque Saenz Peña communicated to Andrew Carnegie his request to have a replica of D. carnegii. His request was accepted, and on July 1, 1912, 34 boxes containing the cast of the animal were sent to Argentina on the S.S. ‘Sallust’. William Holland and Mr. Arthur Coggeshall were in charge of mounting the replica. The site where the replica would be mounted in the Museo de La Plata, would be the Sala III, which was dedicated to invertebrates and plants. Holland insisted that the plans used for the mounting of D. carnegii at Vienna were followed in mounting the skeleton in La Plata. After the skeleton was mounted, the Director of the Museum, Dr. Samuel Lafone-Quevedo, gave a speech expressing his gratitude to Andrew Carnegie and his representatives, in which William Holland was designated an Honorary Member of La Plata University.

Reference:

Alejandro Otero and Zulma Gasparini “The History of the Cast Skeleton of Diplodocus carnegii Hatcher, 1901, at the Museo De La Plata, Argentina,” Annals of Carnegie Museum 82(3), (2014). doi: http://dx.doi.org/10.2992/007.082.0301

BARRETT, P., P. PARRY, AND S. CHAPMAN. 2010. Dippy: The Tale of a Museum Icon. Natural History Museum, London. 48 pp.

 

The hyperthermals of the geological record

During the last 540 million years five mass extinction events shaped the history of the Earth. Those events were related to extreme climatic changes. The geological records show that large and rapid global warming events occurred repeatedly during the course of Earth history.
Our planet’s climate has oscillated between two basic states: the “Icehouse”, and the “Greenhouse”, and superimposed on this icehouse–greenhouse climate cycling, there are a number of geologically abrupt events known as hyperthermals, when atmospheric CO2 concentrations may rise above 16 times (4,800 ppmv). Although each hyperthermal is unique, they are consequence from the release of anomalously large inputs of CO2 into the atmosphere and are relatively short-lived (with the exception of the Permian–Triassic boundary).

A summary of the most significant hyperthermals in the last 300 Myr. From Foster et. al., 2018.

The emplacement of large igneous provinces (LIPs) is commonly associated with hyperthermals, for example, the Siberian Traps at the P–T boundary. The CO2 emissions caused global warming. The SO2 emissions on mixing with water vapour in the atmosphere, caused acid rain, which in turn killed land plants and caused soil erosion. Warmer oceans melted frozen methane located in marine sediments which pushed the global temperatures to higher levels. Additionally, the increased continental weathering induced by acid rain and global warming led to increased marine productivity and eutrophication, and so oceanic anoxia, and marine mass extinctions.

The hyperthermal at the P–T boundary was associated with the most severe terrestrial and oceanic mass extinction of the last 541 Myr, where 96% of species became extinct. It comprises two killing events, one at the end of the Permian (EPME) and a second at the beginning of the Triassic, separated by 60000 years. In terms of carbon isotope excursion, the P–T boundary hyperthermal and the PETM share many similarities, but the warming after the P-T boundary was more extreme and extended for longer than PETM.

Flow chart summarizing proposed cause-and-effect relationships during the end-Permian extinction (From Bond and Wignall, 2014)

The End-Triassic Extinction is probably the least understood of the big five. It has been linked to the eruption of the Central Atlantic Magmatic Province (CAMP), a large igneous province emplaced during the initial rifting of Pangea. 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.

The early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 mya) in the Jurassic Period is considered as one of the most severe of the Mesozoic era. The T-OAE is thought to have been caused by increased atmospheric CO2 triggered by Karoo–Ferrar volcanism. Results from the Paris Bassin indicates that the increasing greenhouse conditions may have caused acidification in the oceans, hampering carbonate bio-mineralisation, and provoking a dramatical loss in the CO2 storage capacity of the oceans.

Tentative changes in mid-latitude vegetation patterns during OAE2. (a) Araucariaceae, (b) other conifers incl. Cheirolepidiaceae, (c) Cupressaceae, (d) angiosperms incl. Normapolles-producing forms, (e) ferns. From Heimhofer et al., 2018.

The early Aptian Oceanic Anoxic Event (OAE1a, 120 Ma) represents a geologically brief time interval characterized by rapid global warming, dramatic changes in ocean circulation including widespread oxygen deficiency, and profound changes in marine biotas. During the event, black shales were deposited in all the main ocean basins. It was also associated with the calcification crisis of the nannoconids, the most ubiquitous planktic calcifiers during the Early Cretaceous. Their near disappearance is one of the most significant events in the nannoplankton fossil record.

The mid-Cretaceous Oceanic Anoxic Event 2 (OAE2, 93 Ma) marks the onset of an extreme phase in ocean temperatures known as the “Cretaceous thermal maximum”. It has been postulated that the OAE2 was triggered by a massive magmatic episode.

Comparison of the effects of anthropogenic emissions (total of 5000 Pg C over 500 years) and PETM carbon release (3000 Pg C over 6 kyr) on the surface ocean saturation state of calcite. From Zeebe, 2013

The Paleocene-Eocene Thermal Maximum (PETM; 55.8 million years ago), was a short-lived (~ 200,000 years) global warming event attributed to a rapid rise in the concentration of greenhouse gases in the atmosphere. It was suggested that this warming was initiated by the melting of methane hydrates on the seafloor and permafrost at high latitudes. During the PETM, around 5 billion tons of CO2 was released into the atmosphere per year, and temperatures increased by 5 – 9°C. This event was accompanied by other large-scale changes in the climate system, for example, the patterns of atmospheric circulation, vapor transport, precipitation, intermediate and deep-sea circulation and a rise in global sea level. But unlike other hyperthermals, the PETM is not associated with significant extinctions.

Anthropogenic climate change and ocean acidification resulting from the emission of vast quantities of CO2 and other greenhouse gases pose a considerable threat to ecosystems and modern society. The combination of global warming and the release of large amounts of carbon to the ocean-atmosphere system during the PETM has encouraged analogies to be drawn with modern anthropogenic climate change. The current rate of the anthropogenic carbon input is probably greater than during the PETM, causing a more severe decline in ocean pH and saturation state. Also the biotic consequences of the PETM were fairly minor, while the current rate of species extinction is already 100–1000 times higher than would be considered natural. This underlines the urgency for immediate action on global carbon emission reductions.

References:

Foster GL, Hull P, Lunt DJ, Zachos JC. (2018) Placing our current‘hyperthermal’ in the context of rapid climate change in our geological past. Phil. Trans. R. Soc. A 376: 20170086 http://dx.doi.org/10.1098/rsta.2017.0086

Benton MJ. (2018) Hyperthermal-driven mass extinctions: killing models during the Permian–Triassic mass extinction. Phil. Trans. R. Soc. A 376: 20170076. http://dx.doi.org/10.1098/rsta.2017.0076

Penn, J. L., Deutsch, C., Payne, J. L., & Sperling, E. A. (2018). Temperature-dependent hypoxia explains biogeography and severity of end-Permian marine mass extinction. Science, 362(6419), eaat1327. doi:10.1126/science.aat1327 

Ernst, R. E., & Youbi, N. (2017). How Large Igneous Provinces affect global climate, sometimes cause mass extinctions, and represent natural markers in the geological record. Palaeogeography, Palaeoclimatology, Palaeoecology, 478, 30–52. doi:10.1016/j.palaeo.2017.03.014

Turgeon, S. C., & Creaser, R. A. (2008). Cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode. Nature, 454(7202), 323–326. doi:10.1038/nature07076

Ulrich Heimhofer, Nina Wucherpfennig, Thierry Adatte, Stefan Schouten, Elke Schneebeli-Hermann, Silvia Gardin, Gerta Keller, Sarah Kentsch & Ariane Kujau (2018) Vegetation response to exceptional global warmth during Oceanic Anoxic Event 2, Nature Communications volume 9, Article number: 3832

Zeebe RE and Zachos JC. 2013 Long-term legacy ofmassive carbon input to the Earth system: Anthropocene versus Eocene. Phil Trans R Soc A 371: 20120006. http://dx.doi.org/10.1098/rsta.2012.0006.

 

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

New tetrapod assemblage from the Chañares Formation

Skeletal anatomy of the erpetosuchid pseudosuchian Tarjadia ruthae. From Ezcurra et al., 2017

In the aftermath of the Permo-Triassic mass extinction (~252 Ma), several typical Palaeozoic synapsids and parareptiles were replaced by stem and crown archosaurs (archosauromorphs) and eucynodonts, and the Late Triassic fossil record of South America has been crucial to shed light on their evolutionary histories.

The Chañares Formation is part of the Ischigualasto-Villa Unión Basin, and represents one of the most continuous continental Triassic succesions in South America. Located in Talampaya National Park (La Rioja Province), the Chañares Formation is characterized at its base by a sandstone–siltstone fluvial facies with distinct lower and upper levels. The lower levels are composed of light olive grey fine-grained sandstones with abundant small brown carbonate concretions. The upper levels include fine-grained sandstones and siltstones that yielded a rich tetrapod assemblage composed of kannemeyeriiform dicynodonts, traversodontid and probainognathian cynodonts, proterochampsid stem-archosaurs, stem-crocodylians, and dinosaur precursors.

Volcanism played an important role in the generation and preservation of the Chañares Formation’s exceptional tetrapod fossil record. Recent radioisotopic datings temporally constrained most of the lower half of this unit to the earliest Carnian (236–231 Ma), showing that this assemblage preceded the oldest members of typical Late Triassic archosaur clades that are found in the Ischigualasto Formation. The new assemblage is called here as the Tarjadia Assemblage Zone, while the upper, historically known assemblage is called the Massetognathus–Chanaresuchus Assemblage Zone. This new assemblage sheds light on the link between the Early–Middle Triassic tetrapod assemblages of Africa (for example, Karoo, Ruhuhu and Otiwarongo basins) and those from the Middle–Late Triassic of South America.

The Chañares Formation (© 2012 Idean)

Tarjadia ruthae is characterized by a dorsoventrally thick skull roof ornamented by deep pits and grooves of random arrangement; Y-shaped tuberosity on the dorsal surface of the anterior end of the parietals; marginal dentition with serrations; spine table of the presacral and anterior caudal vertebrae with a transversely concave dorsal surface; a femur with a poorly developed fourth trochanter and a hook-shaped tibial condyle; and thick dorsal osteoderms with a coarse pitted ornamentation. The abundance of the erpetosuchid Tarjadia in the lowermost levels of the Chañares Formation indicates that this pseudosuchian was an important secondary consumer in its ecosystem

The Tarjadia and Massetognathus–Chanaresuchusassemblage zones currently do not share species or low level taxa, indicating a profound faunal replacement involving both primary and secondary consumers. Therefore, the rise of dinosaurs and other archosauromorph clades that diversified worldwide in the Late Triassic was preceded by a phase of relatively rapid changing ecosystems in southwestern Pangaea, including two (Tarjadia and Massetognathus–Chanaresuchus assemblage zones) profound faunal replacements in a time span shorter than 6 Myr (around 236–231 Ma).

References:

Martín D. Ezcurra, Lucas E. Fiorelli, Agustín G. Martinelli, Sebastián Rocher, M. Belén von Baczko, Miguel Ezpeleta, Jeremías R. A. Taborda, E. Martín Hechenleitner, M. Jimena Trotteyn & Julia B. Desojo; Deep faunistic turnovers preceded the rise of dinosaurs in southwestern Pangaea, Nature Ecology & Evolution (2017) doi:10.1038/s41559-017-0305-5

Benton, M. J., Tverdokhlebov, V. P. & Surkov, M. V. Ecosystem remodelling among vertebrates at the Permian–Triassic boundary in Russia. Nature 432, 97–100 (2004).

The Enigmatic Chilesaurus and the evolution of ornithischian dinosaurs

Chilesaurus diegosuarezi (MACN)

Chilesaurus diegosuarezi is a bizarre dinosaur from the Upper Jurassic of southern Chile. Holotype specimen (SNGM-1935) consists of a nearly complete, articulated skeleton, approximately 1.6 m long. Four other partial skeletons (specimens SNGM-1936, SNGM-1937, SNGM-1938, SNGM-1888) were collected in the lower beds of Toqui Formation. All the preserved specimens of Chilesaurus show ventrally flexed arms with the hands oriented backwards, an arrangement that closely resembles the resting posture similar described in Mei long, Sinornithoides youngi, and Albinykus baatar. 

Chilesaurus possesses a number of surprisingly plesiomorphic traits on the hindlimbs, especially in the ankle and foot, which resemble basal sauropodomorphs; but the pubis closely resembles that of basal ornithischians. The bizarre anatomy of Chilesaurus raises interesting questions about its phylogenetic relationships. The features supporting the basal position of Chilesaurus within Tetanurae are: scapular blade elongate and strap-like; distal carpal semilunate; and manual digit III reduced.

Chilesaurus holotype cast (MACN)

But the position of Chilesaurus within within Tetanurae conflicts with the presence of several highly derived coelurosaurian features (e.g., opisthopubic pelvis, large supratrochanteric process on ilium, reduced supracetabular crest) which are present in combination with a number of surprisingly plesiomorphic traits present in basal sauropodomorphs.

Ornithischian features of Chilesaurus (From Baron and Barret, 2017)

Chilesaurus also shows several characters typical of ornithischians. The features include a premaxilla with an edentulous anterior region;  loss of recurvature in maxillary and dentary teeth; a postacetabular process that is 25–35% of the total anteroposterior length of the ilium; possession of a retroverted pubis; a pubis with a rod-like pubic shaft; a pubic symphysis that is restricted to the distal end of the pubis; and a femur that is straightened in anterior view.

The unique combination of ‘primitive’ and ‘derived’ characters for Chilesaurus has the potential to illuminate the order in which traditional ornithischian synapomorphies were acquired. For instance, Chilesaurus lacks a predentary bone, one of the features previously regarded as a fundamental ornithischian feature, although it possesses a retroverted pubis, suggesting that opisthopuby preceded the evolution of some craniodental modifications. Opisthopuby has also been related to herbivory, as it has been suggested that pubic retroversion might be related to the evolution of a more complex, longer digestive tract (Baron and Barret, 2017).

References:

Baron MG, Barrett PM. 2017, A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs. Biol. Lett. 13: 20170220. http://dx.doi.org/10.1098/rsbl.2017.0220

Nicolás R. Chimento, Federico L. Agnolin, Fernando E. Novas, Martín D. Ezcurra, Leonardo Salgado, Marcelo P. Isasi, Manuel Suárez, Rita De La Cruz, David Rubilar-Rogers & Alexander O. Vargas (2017) Forelimb posture in Chilesaurus diegosuarezi (Dinosauria, Theropoda) and its behavioral and phylogenetic implications. Ameghiniana doi: 10.5710/AMGH.11.06.2017.3088

Novas, F.E., Salgado, L., Suarez, M., Agnolín, F.L., Ezcurra, M.D., Chimento, N.R., de la Cruz, R., Isasi, M.P., Vargas, A.O., and Rubilar-Rogers, D. 2015. An enigmatic plant-eating theropod from the Late Jurassic period of Chile. Nature 522: 331-334. doi:10.1038/nature14307

The Early Aptian Oceanic Anoxic Event.

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The Early Cretaceous (Aptian Age), 120 Ma.

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 Aptian Oceanic Anoxic Event (OAE1a, 120 Ma) represents a geologically brief time interval characterized by rapid global warming, dramatic changes in ocean circulation including widespread oxygen deficiency, and profound changes in marine biotas. During the event, black shales were deposited in all the main ocean basins. It was also associated with the calcification crisis of the nannoconids, the most ubiquitous planktic calcifiers during the Early Cretaceous. Their near disappearance is one of the most significant events in the nannoplankton fossil record.

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Scanning electron microscope photos of different nannofossil assemblages from Early Cretaceous chalks from the North Sea (adapted from Mutterlose & Bottini, 2013)

Calcareous nannoplankton represent a major component of oceanic phytoplankton. Their calcareous skeletons can be found in fine-grained pelagic sediments in high concentrations and the biomineralization of coccoliths is a globally significant rock-forming process. The ‘nannoconid decline’ is related to the emplacement of the Ontong Java Plateau (OJP). The  CO2 released by the flood basalts was the main player in the climatic events. However, records from the Pacific and Tethys realms demonstrate that during OAE 1a the  major shift in global oceanic osmium composition occurs well after the onset of the nannoconid crisis. Previous studies argued that the nannoconid crisis was caused by ocean acidification due to numerous pulses of CO2 and methane. The Ontong Java Plateau is a massive, submerged seafloor.  It covers an area of about 1,900,000 square kilometers. It  was emplaced ca. 120 Ma, with a much smaller magmatic pulse of ca. 90 Ma. The CO2 release was too late, and too gradual, to have caused the calcification crisis in the nannoconids by ocean acidification

References:

Naafs, B. D. A. et al., Gradual and sustained carbon dioxide release during Aptian Oceanic Anoxic Event 1a, Nature Geosci. http://dx.doi.org/10.1038/ngeo2627 (2016)

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

Application of diatoms to tsunami studies.

Lisbon earthquake and tsunami in 1755 (From Wikipedia Commons)

Lisbon earthquake and tsunami in 1755 (From Wikipedia Commons)

Diatoms are unicellular algae with golden-brown photosynthetic pigments with a fossil record that extends back to Early Jurassic. The most distinctive feature of diatoms is their siliceous skeleton known as frustule that comprise two valves. They live in aquatic environments, soils, ice, attached to trees or anywhere with humidity and their remains accumulates forming diatomite, a type of soft sedimentary rock. Diatoms are the dominant marine primary producers in the oceans and play a key role in the carbon cycle and in the removal of biogenic silica from surface waters. But diatoms are also a valuable tool in reconstructing paleoenvironmental changes because of their sensitivity to environmental factors including salinity, tidal exposure, substrate, vegetation, pH, nutrient supply, and temperature found in specific coastal wetland environments. Through years, diatoms become part of the coastal sediments, resulting in buried assemblages that represent an environmental history that can span thousands of years. Diatoms alone cannot differentiate tsunami deposits from other kinds of coastal deposits, but they can provide valuable evidence for the validity of proposed tsunami deposits (Dura et al., 2015).

Electron microscope image of Diatoms from high altitude aquatic environments of Catamarca Province, Argentina (From Maidana and Seeligmann, 2006)

Electron microscope image of Diatoms from high altitude aquatic environments of Catamarca Province, Argentina (From Maidana and Seeligmann, 2006)

Tsunami deposits can be identify by finding anomalous sand deposits in low-energy environments such as coastal ponds, lakes, and marshes. Those anomalous deposits are diagnosed using several criteria such as floral (e.g. diatoms) and faunal fossils within the deposits. The delicate valves of numerous diatom species may be unusually well preserved when removed from surface deposits and rapidly buried by a tsunami.

Diatoms within the tsunami deposits are generally composed of mixed assemblages, because tsunamis inundated coastal and inland areas, eroding, transporting, and depositing brackish and freshwater taxa. Nonetheless, problems differentiating autochthonous (in situ) and allochthonous (transported) diatoms complicates reconstructions. In general, planktonic diatoms are considered allochthonous components in modern and fossil coastal wetland assemblages, while benthic taxa can be considered as autochthonous. Diatoms can also be used to estimate tsunami run-up  by mapping the landward limit of diatom taxa transported by the tsunami.

 

References:

Hemphill-Haley, E., 1996. Diatoms as an aid in identifying late Holocene tsunami deposits. The Holocene 6, 439–448.

Tina Dura, Eileen Hemphill-Haley, Yuki Sawai, Benjamin P. Horton, The application of diatoms to reconstruct the history of subduction zone earthquakes and tsunamis, Earth-Science Reviews 152 (2016) 181–197. DOI: 10.1016/j.earscirev.2015.11.017

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

Barron, J.A. (2003). Appearance and extinction of planktonic diatoms during the past 18 m.y. in the Pacific and Southern oceans. “Diatom Research” 18, 203-224