Introducing Bajadasaurus pronuspinax.

Bajadasaurus reconstruction (Museo Municipal Ernesto Bachmann, Villa El Chocón, Neuquén).

Dicraeosauridae is a family of mid-sized sauropod dinosaurs characterized by a distinctive vertebral column with paired, long, neural spines. The group was first described in 1914 by Werner Janensch with the discovery of the nearly complete skeletons of Dicraeosaurus in the expeditions to the upper Jurassic beds of Tendaguru, Tanzania. Dicraeosauridae includes  Amargasaurus, Pilmatueia, Suuwassea, and Brachytrachelopan. Now, the description of Bajadasaurus pronuspinax gen. et sp. nov., from the Early Lower Cretaceous of Bajada Colorada Formation in Northern Patagonia, Argentina), shed new light on the function of its spines and the defense behavior in sauropod dinosaurs.

Bajadasaurus was discovered in 2013, by a team of paleontologists from CONICET, Fundación Félix de Azara, Universidad Maimónides, and Museo Paleontológico Ernesto Bachmann. The generic name derived from Bajada (Spanish, in reference to the locality Bajada Colorada) and saurus (Greek, lizard). The specific name derived from pronus (Latin, bent over forward) and spinax (Greek, spine), referring to the anteriorly pointed, curved, neural spines of the cervical vertebrae.

Skeletal elements of Bajadasaurus pronuspinax. From Gallina et al., 2019.

The holotype, MMCh-PV 75, includes a nearly complete skull (left maxilla, left lacrimal, both prefrontals, both frontals, both parietals, both postorbitals, both squamosals, left quadratojugal, both pterygoids, both quadrates, supraoccipital, exoccipital-opisthotic complex, basioccipital, basisphenoid, both prootics, both laterosphenoids, both orbitosphenoids, both dentaries, left surangular, both angulars, both splenials, left prearticular, left articular, isolated upper tooth row), both proatlases, atlantal neurapophyses, axis and the fifth cervical vertebra.

The skull of Bajadasaurus is gracile, with dorsally exposed orbits, dorsoventrally compressed occipital condyle, extremely narrow basipterygoid processes, elongate and slender anterior processes of the squamosals, medially extended post-temporal fenestrae, short lateral temporal fenestrae and a reduced dentition in the maxilla and dentary, that largely differs from other known taxa within Dicraeosauridae. But the most striking feature of Bajadasaurus is the presence of extremely long cervical neural spines that curve anteriorly. Amargasaurus exhibit the same development of cervical neural spine elongation as Bajadasaurus, but the spines of the former point backwards rather than forwards. Dicraeosaurus and Brachytrachelopan show anteriorly inclined neural spines in the cervical vertebrae, but the spines are much shorter than in Bajadasaurus.

A group of Bajadasaurus. Illustration: Jorge A. González.

The discovery of Amargasaurus cazaui in 1991, from the Early Cretaceous beds of La Amarga Formation of Northern Patagonia, renewed the discussion on the peculiar vertebral anatomy of these sauropod dinosaurs, including interpretations as a support structure for a thermoregulatory sail, a padded crest as a display and/or clattering structure, a dorsal hump, or as internal cores of dorsal horn. Those explanation, except the last one, require that these long and extremely gracile bone projections, now recognized in Bajadasaurus as well, can support enough physical stress to avoid fracturing. Bone is stronger and stiffer in passive situations, however, horns and other keratin-based materials are tougher and highly resistant to impact-related fractures. Therefore, the keratinous sheath in Amargasaurus and perhaps Bajadasaurus provides a better mechanical solution against a potential fracture.

 

References:

Gallina, Pablo A., Apesteguía, Sebastián, Canale, Juan I., Haluza, Alejandro (2019), A new long-spined dinosaur from Patagonia sheds light on sauropod defense system, Scientific Reports volume 9, Article number: 1392 DOI: https://doi.org/10.1038/s41598-018-37943-3

Janensch, W. Die Wirbelsäule der Gattung Dicraeosaurus. Palaeontographica Supplement 7, 37–133 (1929).

Salgado, L. & Bonaparte, J. F. Un nuevo saurópodo Dicraeosauridae, Amargasaurus cazaui gen et sp. nov., de la Formación La Amarga, Neocomiano de la provincia del Neuquén, Argentina. Ameghiniana 28, 333–346 (1991).

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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

On Pterosaurs and feathers.

Reconstruction of one of the studied anurognathid pterosaurs. Credit: Yuan Zhang/Nature Ecology & Evolution.

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.

 

Drawing of of (a) NJU–57003 and (b) CAGS–Z070 with skeletal element identification, outline of
preserved integument, and distribution of the four types of pycnofibres. From Yang et al., 2018.

Types 1 and 4 of pycnofibres occur in both specimens, but types 2 and 3 occur only in CAGS–Z070. This may reflect original biological differences or differences in the taphonomy of the two specimens. The pterosaur type 1 filaments resemble monofilaments in the ornithischian dinosaurs Tianyulong and Psittacosaurus and the coelurosaur Beipiaosaurus. The pterosaur type 2 filaments resemble the brush-like bundles of filaments in the coelurosaurs Epidexipteryx and Yi. Type 3 filaments resemble bristles in modern birds, but surprisingly do not correspond to any reported morphotype in non-avian dinosaurs. The pterosaur type 4 filaments are identical to the radially branched, downy feather-like morphotype found widely in coelurosaurs such as Caudipteryx and Dilong. Functions of these structures could include insulation, tactile sensing, streamlining and colouration (primarily for camouflage and signalling), as for bristles, down feathers and mammalian hairs.

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

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:

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

Barrett PM, Evans DC, Campione NE. 2015 Evolution of dinosaur epidermal structures. Biol. Lett. 11: 20150229. http://dx.doi.org/10.1098/rsbl.2015.0229

Kai R.K. Jäger, Helmut Tischlinger, Georg Oleschinski, and P. Martin Sander, Goldfuß was right: Soft part preservation in the Late Jurassic pterosaur Scaphognathus crassirostris revealed by reflectance transformation imaging (RTI) and UV light and the auspicious beginnings of paleo-art, https://doi.org/10.26879/713

Craig B. Lowe, Julia A. Clarke, Allan J. Baker, David Haussler and Scott V. Edwards, Feather Development Genes and Associated Regulatory Innovation Predate the Origin of Dinosauria, Mol Biol Evol (2015) 32 (1): 23-28. doi: 10.1093/molbev/msu309

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

Introducing Macrocollum itaquii.

M. itaquii, the oldest long-necked dino ever found, dating back 225 million years. (Credit: Müller et al 2018)

Sauropodomorphs were the largest land animals ever recorded in the history of life. Additionally to their colossal size, the sauropodomorph bauplan is also characterised by a small head, long neck, barrel-shaped body and columnar limbs. The group was successful and diverse, achieving a worldwide geographical distribution. Nevertheless, the rise of sauropodomorphs is still poorly understood due to the scarcity of well-preserved fossils in early Norian rocks. The Wachholz site (Caturrita Formation), in southern Brazil, is an important window to early Norian land ecosystems. This unit has yielded several sauropodomorphs, including Unaysaurus tolentinoi and the recently described Macrocollum itaquii, the oldest long-necked dinosaur known, that shed light on the rise of the group.

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.

 

Skull of Macrocollum itaquii (From Müller et al 2018)

The generic name combines the Greek word macro (long) and the Latin word collum (neck), referring to the animal’s elongated neck. The specific epithet honours José Jerundino Machado Itaqui, one of the main actors behind the creation of CAPPA/UFSM (Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia/Universidade Federal de Santa Maria).

M. itaquii was only 3.5 meters long and weighed about 101.6 kilograms, and differs from all other known sauropodomorphs in possessing the following characters: antorbital fossa perforated by a promaxillary fenestra; medial margin of the supratemporal fossa with a simple smooth curve at the frontal/parietal suture; proximal articular surface of metacarpal I transversely narrow; acetabulum not fully open; ischiadic longitudinal groove not reaching the caudal half of the ischium; absence of trochanteric shelf on the femur; medial condyle of distal femoral articulation subrectangular in distal view; proximal end of metatarsal II with a straight medial margin.

An artist’s impression of M. itaquii.

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.

 

References:

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

 

 

Introducing Mirarce eatoni, the wonderful winged messenger.

Skeletal reconstruction of Mirarce eatoni showing preserved skeletal elements (white). Illustration: Scott Hartman.

Birds originated from a theropod lineage more than 150 million years ago. By the Early Cretaceous, they diversified, evolving into a number of groups of varying anatomy and ecology. In recent years, several discovered fossils of theropods and early birds have filled the morphological, functional, and temporal gaps along the line to modern birds. Most of these fossils are from the Jehol Biota of northeastern China, dated between approximately 130.7 and 120 million years ago. Among them was the long bony-tailed Jeholornis, only slightly more derived than Archaeopteryx, that lived with Sapeornis, Confuciusornis, and the earliest members of Enantiornithes.

Enantiornithes are the most diverse group of Mesozoic birds. Their remains have been collected on every continent except Antarctica, although their fossil record is particularly poor in North America and limited to the Late Cretaceous. The first probable enantiornithines from North America were collected in the 19th Century, and may be referable to Avisaurus archibaldi. Originally, A. archibaldi was described as a member of a new clade of non-avian theropod dinosaurs, the Avisauridae, the first recognized clade of enantiornithines, defined as “the common ancestor of Neuquenornis volans and Avisaurus archibaldi plus all its descendants”.

Best-preserved cervical and thoracic vertebrae, including the axis of Mirarce (From Atterholt et al., 2018)

The most complete known North American enantiornithine, the so-called “Kaiparowits avisaurid”, was collected in 1992. The specimen was recognized as a new taxon, Mirarce eatoni. Named for its spectacular preservation and level of morphological detail, the holotype (UCMP 139500) of this large, turkey-sized avisaurid enantiornithine is a three-dimensional partial skeleton consisting of several cervical and thoracic vertebrae (including the axis), the pygostyle, almost all phalanges from the left pes and several from the right, a complete humerus, femur, and tarsometatarsus, a partial scapula, coracoid, furcula, and tibiotarsus, as well as fragments of the sternum, radius, ulna, carpometacarpus, and manual phalanges.

The preserved sternal fragment of Mirarce indicates the presence of a well-developed ventral keel, very similar to that observed in Neuquenornis. In modern birds, the narrow furcula and the remige papillae, transfer aerodynamic forces from the feathers to the wing skeleton. These features were also present in Mirarce, and support the hypothesis that at least some lineages of enantiornithines convergently achieved more advanced aerial capabilities by the Late Cretaceous.

Reconstruction of living Mirarce eatoni. Illustration: Brian Engh.

The Enantiornithes have a long evolutionary history, and surviving up to the K–Pg boundary. Several trends have been suggested for the group, including: a general increase in range of body sizes; a greater degree of fusion of compound elements, and the appearance of advanced flight-related features evolved in parallel to the neornithine lineage (like manual reduction, loss of teeth, increase in size of sternal keel). It has been proposed that they were primarily forest dwellers, so they disappeared after the Chicxulub impact triggered widespread destruction of forests.

 

References:

Atterholt J, Hutchison JH, O’Connor JK. (2018) The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae. PeerJ 6:e5910 https://doi.org/10.7717/peerj.5910

Daniel J. Field et al. Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction. Current Biology, published online May 24, 2018; doi: 10.1016/j.cub.2018.04.062

Halloween special VI: Baron Nopcsa and the dinosaurs of Transylvania

The Nopcsa Sacel Castle

Transylvania is mostly known for its myths about vampires. Following the publication of Emily Gerard’s The Land Beyond the Forest (1888), Jules Verne published Le Château des Carpathes (The Castle of the Carpathians) in which Transylvania is described as one of the most superstitious countries of Europe. But of course, the most significant contribution to the development of the Transylvania place myth was Bram Stoker’s Dracula, published in 1897.

Sacel Castle, at the heart of the Hateg region, is the last residence of the Nopcsa family, known as one of the strangest in Transylvania. Among the members of the family, there were governmental counselors and chancellors of the Transylvanian Court, members of the Royal Minister and of the Royal House, and knights of imperial orders. Baron Franz Nopcsa of Felsöszilvás (1877-1933), was one of the most prominent researchers and scholars of his day, and is considered the forgotten father of dinosaur paleobiology.

Baron Nopcsa in Albanian Uniform, 1915

In 1897 Nopcsa became a student of Vienna University and by the age of 22, he presented the first description and paleobiological analysis of one of the Transylvanian dinosaurs before the Vienna Academy of Science: Telmatosaurus transsylvanicus. The holotype, BMNH B.3386, was found in the Haţeg Basin.

The Hateg region, situated at the heart of Transylvania, is the cradle of Romanian civilization, but 70 million years ago it was a tropical island in the Thetys Ocean, noted for the occurrence of aberrant, endemic, and dwarfed fauna. In 1914, Nopcsa theorized that the “limited resources” found on islands have an effect of “reducing the size of animals” over the generations. Nopcsa noted several palaeobiological features in support of his views, including what he perceived as the common presence of pathological individuals, and considered this condition a reasonable result of the ecologically impoverished and stressed environment inhabited by this fauna. The recognition of ameloblastoma in a Telmatosaurus dentary discovered from the same area represents the best documented case of pathological modification identified in Transylvanian dinosaurs.

Doda, left, and Nopcsa, circa 1931. They spent nearly 30 years together. (Hungarian Natural History Museum)

Nopcsa continued to do collecting in the Haţeg Basin, at least until the beginning of the First World War. Among the fossils that Nopcsa studied were the duck-billed Telmatosaurus transylvanicus, the bipedal and beaked Zalmoxes robustus, the armored Struthiosaurus transylvanicus, and the sauropod Magyarosaurus dacus. In addition, he made extensive travels across much of Europe to visit palaeontological museums and to meet fellow scientists. In his field trips Nopcsa was now accompanied by Elmas Doda Bajazid, whom Nopcsa met in Albania and convinced to become his secretary. The men spent nearly 30 years togheter.

On 25 April 1933, Nopcsa’s body and that of his secretary Bajazid were found at their Singerstrasse residence. Nopcsa left a letter to the police: ”The motive for my suicide is a nervous breakdown. The reason that I shot my longtime friend and secretary, Mr Bayazid Elmas Doda, in his sleep without his suspecting at all is that I did not wish to leave him behind sick, in misery and without a penny, because he would have suffered too much. I wish to be cremated.”

 

References:

David B. Weishampel & Oliver Kerscher (2012): Franz Baron Nopcsa, Historical Biology: An International Journal of Paleobiology, DOI:10.1080/08912963.2012.689745

CSIKI, Z. & BENTON, M.J. (2010): An island of dwarfs – Reconstructing the Late Cretaceous Haþeg palaeoecosystem. Palaeogeography, Palaeoclimatology, Palaeoecology 293: 265 – 270 doi:10.1016/j.palaeo.2010.05.032

Dumbravă, M. D. et al. A dinosaurian facial deformity and the first occurrence of ameloblastoma in the fossil record. Sci. Rep. 6, 29271; doi: 10.1038/srep29271 (2016).

 

 

Introducing Dynamoterror dynastes, the powerful terror ruler.

Frontals of Dynamoterror dynastes in rostral view. From McDonald et al., 2018. (Scale bars = 5 cm)

Tyrannosauroidea is a relatively derived group of theropod dinosaurs more closely related to birds than to other large theropods such as allosauroids and spinosaurids. The clade originated in the Middle Jurassic, approximately 165 million years ago, and for most of their evolutionary history, tyrannosauroids were mostly small-bodied animals that only reached gigantic size during the final 20 million years of the Cretaceous. Until recently, all tyrannosaurs fossils were limited to Asia and North America, but the latest discoveries suggest a more cosmopolitan distribution during their early evolution.

All tyrannosaurs were bipedal predators characterized by premaxillary teeth with a D-shaped cross section, fused nasals, extreme pneumaticity in the skull roof and lower jaws, a pronounced muscle attachment ridge on the ilium, and an elevated femoral head. The clade was a dominant component of the dinosaur faunas of the American West shortly after the emplacement of the Western Interior Seaway (about 99.5 Mya).

Paleogeography of North America during the late Campanian Stage of the Late Cretaceous (∼75 Ma). From Sampson et al., 2010

Dynamoterror dynastes, the most recent taxon described from the lower Campanian of northwestern New Mexico, provides additional data on the morphology and diversity of early tyrannosaurines in Laramidia. The new specimen lived during the Late Cretaceous period, approximately 78 million years ago. The name derived from Greek word dynamis (“power”) and the Latin word terror. The specific name is a Latin word meaning “ruler. Dynamoterror was collected in San Juan County, New Mexico, and is the first associated tyrannosaurid skeleton reported from the Menefee Formation.

The holotype (UMNH VP 28348) is an incomplete associated skeleton including the left and right frontals, four fragmentary vertebral centra, fragments of dorsal ribs, right metacarpal II, supraacetabular crest of the right ilium, unidentifiable fragments of long bones, phalanx 2 of left pedal digit IV, and phalanx 4 of left pedal digit IV. The right and left frontals both are incomplete; the dimensions of the right frontal are similar to a subadult specimen of Tyrannosaurus rex, suggesting that UMNH VP 28348 represents a subadult or adult individual. The reconstructed skull roof of Dynamoterror present several tyrannosaurine features, such as large supratemporal fossae and a tall sagittal crest on the frontals, providing an expanded attachment area for enormous jaw-closing muscles.

 

References:

McDonald AT, Wolfe DG, Dooley AC Jr. (2018) A new tyrannosaurid (Dinosauria: Theropoda) from the Upper Cretaceous Menefee Formation of New Mexico. PeerJ 6:e5749 https://doi.org/10.7717/peerj.5749

Brusatte SL, Norell MA, Carr TD, Erickson GM, Hutchinson JR, et al. (2010) Tyrannosaur paleobiology: new research on ancient exemplar organisms. Science 329: 1481–1485. doi: 10.1126/science.1193304

Sampson SD, Loewen MA, Farke AA, Roberts EM, Forster CA, Smith JA, et al. (2010) New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism. PLoS ONE 5(9): e12292. https://doi.org/10.1371/journal.pone.0012292

 

 

 

 

 

 

 

 

 

 

 

 

Forgotten women of paleontology: Irene Crespin

Irene Crespin (1896-1980)

Irene Crespin was born on November 12, 1896, in Kew, Victoria, Australia. In her memories, she wrote that her interest in Palaeontology began early in her life, when she was one of the first students to attend the Mansfield High School in northeastern Victoria. The head master of for a short period was the eminent Australian geologist Charles Fenner.

In 1919, she graduated with a B.A. from the University of Melbourne. In 1927 she joined the Commonwealth Government as Assistant Palaeontologist to Frederick Chapman at the National Museum of Victoria. Chapman was an authority on Foraminifera and was president of the Royal Society of Victoria. About her time at the Museum she wrote: “In the early days, we passed through the depression era. Our salaries were reduced overnight. I was reduced to six pounds a week. They were difficult times for us all. One would walk a long distance to save a threepenny tram fare.”

Dr Irene Crespin with W. Baragwanath, Secretary of Mines for Victoria, probably visiting a Cooksonia plant site, c. 1927 (From Turner 2007)

In 1936, Crespin succeeded Chapman as Commonwealth Palaeontologist. On February 10th, she was transferred from the National Museum, Melbourne to join the Commonwealth Geological Adviser, Dr. W.G. Woolnough, in Canberra. About her new position she wrote: “Of course, being a woman, and despite the tremendous responsibility placed upon me with the transfer to Canberra, I was given a salary of about half of that which Chapman received. Later the Chairman of the Public Service Board told me that I was being put on trial.”

She becoming greatly interested in the Tertiary microfaunas, and for some time she was the only professional micropaleontologist on the Australian mainland. Her research took her all over Australia. In 1939, she received permission from the Minister of the Interior to visit Java and Sumatra to discuss the problems of Tertiary correlation in the Netherlands East Indies with Papua and New Guinea.

Crespin’s photo of her aeroplane and crew on an overseas trip to Java, Indonesia, 1939 (From Turner 2007)

Crespin was well respected internationally and was a regular participant in national and international scientific conferences. In 1953, many of her books and specimens were destroyed as a result of a fire in the Canberra offices. The same year, she received Queen Elizabeth II’s coronation medal. In 1957 she was president of the Royal Society of Canberra, and was awarded with the Clarke medal of the Royal Society of New South Wales.

During her career she published 86 papers as sole author and more 22 in collaboration with other scientists. She was made an honorary fellow of the Royal Microscopical Society, London, in 1960. She became an honorary member of the Australian and New Zealand Association for the Advancement of Science in 1973. She died in Canberra, on January 2, 1980.

References:

Turner, S. (2007). Invincible but mostly invisible: Australian women’s contribution to geology and palaeontology. Geological Society, London, Special Publications, 281(1), 165–202. doi: 10.1144/sp281.11

Crespin, Irene (1975). “Ramblings of a micropalaeontologist”. BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS.