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

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Solving a Darwinian mystery

Macrauchenia patachonica by Robert Bruce Horsfall.

During the first two years of his voyage aboard HMS Beagle, Charles Darwin collected a considerable number of fossil mammals from various South American localities. Darwin sent all the specimens to the Reverend Professor John Stevens Henslow, his mentor and a close friend. The samples were deposited in the Royal College of Surgeons where Richard Owen began its study. Between 1837 and 1845, Owen described eleven taxa, including: Toxodon platensis, Macrauchenia patachonica, Equus curvidens, Scelidotherium leptocephalum, Mylodon darwinii, and Glossotherium sp.

Macrauchenia, meaning “big neck,” was named by Richard Owen based on limb bones and vertebrae collected by Charles Darwin on January 1834 at Puerto San Julian, in Santa Cruz Province, Argentina. The bizarre animal had a camel-like body, with sturdy legs, a long neck and a relatively small head. Owen described as “A large extinct Mammiferous Animal, referrible to the Order Pachydermata; but with affinities to the Ruminantia, and especially to the Camelidae”Macrauchenia is now considered among the more derived native South American litopterns, an endemic order whose fossil record extends from the Paleocene to the end of the Pleistocene and includes some 50 described genera. Darwin also made inferences about the environment which Macrauchenia lived: “Mr. Owen… considers that they form part of an animal allied to the guanaco or llama, but fully as large as the true camel. As all the existing members of the family of Camelidae are inhabitants of the most sterile countries, so we may suppose was this extinct kind… It is impossible to reflect without the deepest astonishment, on the changed state of this continent. Formerly it must have swarmed with great monsters, like the southern parts of Africa, but now we find only the tapir, guanaco, armadillo, capybara; mere pigmies compared to antecedents races… Since their loss, no very great physical changes can have taken place in the nature of the Country. What then has exterminated so many living creatures?…We are so profoundly ignorant concerning the physiological relations, on which the life, and even health (as shown by epidemics) of any existing species depends, that we argue with still less safety about either the life or death of any extinct kind” (Voyage of the Beagle, Chapter IX, Jan. 1834).

Dated mitogenomic phylogenetic tree. (From Westbury, M. et al)

The unusual morphological traits displayed by extinct South American native ungulates defied both Charles Darwin and Richard Owen, who tried to resolve their relationships. Two recently published molecular studies, using protein (collagen) sequence information, found that litopterns as well as notoungulates formed a monophyletic unit that shared more recent common ancestry with Perissodactyla than with any other extant placental group.

A valuable tool for uncovering phylogenetic relationships of extinct animals is ancient DNA (aDNA), although, attempts to use standard aDNA methodologies to collect genetic material from specimens from low-latitude localities have been largely unsuccessful. However, a new study recovered a nearly complete mitochondrial genome for Macrauchenia from a cave in southern Chile. The small size of the mitochondrial genome simplifies the assembly of fossil sequences using de novo methods.

In theory, reconstructing an ancient genome de novo can be undertaken without relying on a close relative’s DNA for guidance, but due to contaminant DNA and low average fragment lengths, de novo assembly is generally considered not computationally feasible. A promising new approach is using  the genetic codes of numerous living species as reference points, allowing them to reliably predict the fossil’s likeliest genetic sequences. Using the new approach, the phylogenetic analyses place Macrauchenia as a sister taxon to all living Perissodactyla, with the origin of Panperissodactlya at 66 Ma.

 

References:

Westbury, M. et al. A mitogenomic timetree for Darwin’s enigmatic South American mammal Macrauchenia patachonicaNat. Commun. 8, 15951 doi: 10.1038/ncomms15951 (2017).

Welker, F. et al. Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates. Nature 522, 81–84 (2015). doi:10.1038/nature14249

Buckley, M. Ancient collagen reveals evolutionary history of the endemic South American ‘ungulates’. Proc. Biol. Sci. 282, 20142671 (2015). DOI: 10.1098/rspb.2014.2671

From Argentina with Love: Top Fossils of 2016

Geographic provenance and speculative reconstruction of the gigantic titanosaurian sauropod dinosaur Notocolossus gonzalezparejasi gen. et sp. nov. (From González Riga  et al., 2016; Credit: Scientific Reports)

Since the discovery of dinosaur remains in the Neuquen basin in 1882, Argentina has gained the title of Land of the Giants. And 2016 has brought us amazing fossil discoveries. From Notocolossus to Gualicho, my fossil pick for this year are:

  • Notocolossus

Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina is one of the largest known dinosaurs. The name derived from the Greek notos (southern) and the Latin colossus, in reference to the gigantic size and Gondwanan provenance of the new taxon. The species name honours Dr. Jorge González Parejas, who provided legal guidance on the research, protection, and preservation of dinosaur fossils from Mendoza Province. The holotype of Notocolossus (UNCUYO-LD 301) consists of a partial skeleton lacking the skull. It contains an anterior dorsal vertebra, an anterior caudal vertebra, the right humerus (with 1.76 m in length), and the proximal end of the left pubis. The pes of  Notocolossus is comparatively shorter and more mediolaterally symmetrical than those of other titanosaurs, and indeed, most other sauropods. Notocolossus also presents truncated unguals, characteristics otherwise unknown in the Sauropoda.

Cranium of Sarmientosaurus musacchioi in right lateral view. Scale bar = 10 cm. (From Martínez et al., 2016)

Cranium of Sarmientosaurus musacchioi in right lateral view. Scale bar = 10 cm. (From Martínez et al., 2016)

  • Sarmientosaurus

Another remarkable new species of titanosaurian sauropod was Sarmientosaurus musacchioi. The holotypic and only known specimen consists of an articulated, virtually complete skull and part of the cranial and middle cervical series. The new titanosaur comes from the Lower Member of the Upper Cretaceous Bajo Barreal Formation on the Estancia Laguna Palacios near the village of Buen Pasto in south-central Chubut Province, central Patagonia, Argentina. It is the most basal known titanosaur to be represented by a well-preserved skull. Furthermore, the cranial endocast preserves some of the most complete information about the brain and sensory system for any sauropod.

Scapulocoracoid of Viavenator exxoni gen. et sp. nov. MAU-Pv-LI-530. in lateral view. Scale bar: 10 cm

Scapulocoracoid of Viavenator exxoni in lateral view. Scale bar: 10 cm (a, acromion; cf, coracoid foramen; gc, glenoid cavity; pvp, posteroventral process. From Filippi et al., 2016)

  • Viavenator

The holotype of Viavenator exxoni was found in the outcrops of the Bajo de la Carpa Formation (Santonian, Upper Cretaceous), northwestern Patagonia, Argentina. The new taxon belongs to the South American clade of abelisaurid and possesses, among other characteristics, hypertrophied structures in the presacral axial skeleton. The name derives from the latin word ‘Via’ (road) and ‘venator’ (hunter), meaning the hunter of the road; ‘exxoni’ is in recognition of Exxonmobil’s commitment to the preservation of paleontological heritage of the La Invernada area, Rincón de los Sauces, Neuquen, Patagonia Argentina.

Right postorbital (holotype) of Taurovenator violentei gen. et sp. nov. A, lateral view

Right postorbital (holotype) of Taurovenator violentei gen. et sp. nov. A, lateral view. Scale bar: 3 cm (From Motta et al., 2016)

  • Taurovenator.

Taurovenator violantei gen. et sp. nov. was is a medium-sized carcharodontosaurid theropod from the Huincul Formation (Upper Cretaceous) in northwestern Río Negro province, Patagonia, Argentina. The generic name derives from the Latin words “tauro” (Bull) and “venator” (Hunter). The specific name honours Enzo Violante, owner of the farm where the specimen was discovered. Taurovenator is similar in gross morphology to Giganotosaurus, Carcharodontosaurus, and Mapusaurus, but shows two unique features: the presence of a horn-like structure in the orbital brow and the presence of an excavation housed at the posterodorsal surface of the eye socket.

Different appendicular elements of Murusraptor in their original burial positions (From Coria et al., 2016)

Different appendicular elements of Murusraptor in their original burial positions (From Coria et al., 2016)

  • Murusraptor

Murusraptor barrosaensis, from the Upper Cretaceous of Neuquén Province, Argentina, belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor. Murusraptor, meaning “Wall Raptor”, was discovered in a canyon wall in 2001 during an expedition to Sierra Barrosa in northwestern Patagonia. The holotype specimen includes much of the skull, axial skeleton, pelvis and tibia. The braincase is intact and most of the sutures are still visible, indicating that this was not a fully mature animal. Murusraptor barrosaensis is unique in having anterodorsal process of lacrimal longer than height of preorbital process; sacral ribs hollow and tubelike; short ischia distally flattened and slightly expanded dorsoventrally. Murusraptor also exhibits some characters that are interpreted as convergencies of this taxon with non-tyrannosauroid theropods, including lacrimal with a small pneumatic recess; and a highly pneumatic braincase.

Gualicho shinyae, at the Centro Cultural de la Ciencia.

Gualicho shinyae, at the Centro Cultural de la Ciencia.

  • Gualicho

Gualicho was discovered on a paleontological expedition led by Sebastian Apesteguía in 2007. The name derived from the Gennaken (Northern Tehuelche languaje) watsiltsüm, an old goddess now considered a source of misfortune. The name was chosen to reflect the difficult circumstances surrounding the discovery and study of the specimen. The specific name honors Ms. Akiko Shinya, Chief Fossil Preparator at the Field Museum. The specimen exhibits a new and unusual combination of characters observed in various remotely related clades including ceratosaurs, tyrannosaurids, and megaraptorans. The didactyl manus with a semilunate distal carpal are indicative of derived tetanuran affinities, while the expanded posterior margin of the metatarsal III proximal articulation, are shared with ceratosaurs. The reduced forelimbs with didactyl manus are similar to those of the tyrannosaurids. However, in tyrannosaurids, the carpal elements are reduced and proximodistally flattened, whereas in Gualicho the semilunate and scapholunare carpals retain a more complex shape typical of the carpal elements of most non-coelurosaurian tetanurans. In addition, the manus of Gualicho differs from tyrannosaurids in having a proportionately more robust metacarpal I with a rectangular, rather than triangular, proximal articulation in end view.

 

References:

Bernardo J. González Riga et al. A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot, Scientific Reports (2016). DOI: 10.1038/srep19165

Martínez R.D.F. et al. 2016. A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda) with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria. PLoS ONE 11 (4): e0151661; doi: 10.1371/journal.pone.0151661

Leonardo S. Filippi, Ariel H. Méndez, Rubén D. Juárez Valieri and Alberto C. Garrido (2016). «A new brachyrostran with hypertrophied axial structures reveals an unexpected radiation of latest Cretaceous abelisaurids». Cretaceous Research 61: 209-219. doi:10.1016/j.cretres.2015.12.018

Matías J. Motta, Alexis M. Aranciaga Rolando, Sebastián Rozadilla, Federico E. Agnolín, Nicolás R. Chimento, Federico Brissón Egli, and Fernando E. Novas (2016). «New theropod fauna from the Upper Cretaceous (Huincul Formation) of northwestern Patagonia, Argentina». New Mexico Museum of Natural History and Science Bulletin 71: 231-253

Rodolfo A. Coria, Philip J. Currie. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLOS ONE, 2016; 11 (7): e0157973 DOI: 10.1371/journal.pone.0157973

Apesteguía S, Smith ND, Juárez Valieri R, Makovicky PJ (2016) An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina. PLoS ONE 11(7): e0157793. doi: 10.1371/journal.pone.0157793

A Unique Late Triassic Dinosauromorph Assemblage from Brazil

The skull of Buriolestes shultzi. (Image credit: Cabreira et al., 2016)

The skull of Buriolestes shultzi. (Image credit: Cabreira et al., 2016)

The Santa Maria Formation in southern Brazil, comprises a succession of Middle to Late Triassic sedimentary rocks that have been long renowned for their rich tetrapod fossils including one of the oldest (and the best preserved) associations of dinosaur and dinosaur precursor, respectively represented by new species of Lagerpetidae and Sauropodomorph.

The lagerpetids, a family of basal dinosauromorphs, are represented by a semi-articulated skeleton and a pair of fragmentary femora. As for the dinosaurs, a large articulated individual was preserved, together with smaller and non-duplicated bone elements that indicate the presence of another individual The two articulated specimens are named  Ixalerpeton polesinensis and Buriolestes shultzi.

Ixalerpeton polesinensis helps to define traits of anatomical parts previously unknown for lagerpetids. For example, a skull roof broader than that of most early dinosaurs, an anterior tympanic recess in the braincase, as is typical of Dinosauriforme, although retains traits unknown to that group, such as a large post-temporal fenestra, a postfrontal bone, and a frontal not excavated by the supratemporal fossa.

A: Skeletal reconstruction of Ixalerpeton polesinensis. B: Skull roof. C: Braincase. (Adapted from Cabreira et al., 2016)

A: Skeletal reconstruction of Ixalerpeton polesinensis. B: Skull roof. C: Braincase. Abbreviations: f, frontal; fm, foramen magnum; p, parietal; pof, postfrontal; pp, paroccipital process; so, supraoccipital. (Adapted from Cabreira et al., 2016)

 

Buriolestes shultzi is the earliest member of Sauropodomorpha, although lacks usual sauropodomorph traits such as a reduced skull and an enlarged external naris, and as in all early dinosaurs, the frontal is excavated by the supratemporal fossa. As typical of sauropodomorphs, the humerus is longer than 60% the length of the femur, and the deltopectoral crest extends for more than 40% of its length. The dentary traits are compatible with a faunivorous diet suggesting that early members of the Sauropodomorpha were likely predators.

The fossils, found by a team from the Lutheran University of Brazil, confirms that the co-occurrence between non-dinosaurian Dinosauromorpha and dinosaurs was not restricted to later stages of the Triassic and to the northern parts of Pangaea, suggesting that a rapid replacement was a very unlikely scenario for the initial radiation of dinosaurs.

References:

Cabreira et al., A Unique Late Triassic Dinosauromorph Assemblage Reveals Dinosaur Ancestral Anatomy and Diet, Current Biology (2016), http://dx.doi.org/10.1016/j.cub.2016.09.040

Langer, M.C., Nesbitt, S.J., Bittencourt, J.S., and Irmis, R.B. (2013). Non-dinosaurian Dinosauromorpha. Geol. Soc. Spec. Publ. 379, 157–186.

Fossilized dinosaur brain tissue identified

Computer animation of a fossilized dinosaur brain (Credit: University of Manchester)

Computer animation of a fossilized dinosaur brain (Credit: University of Manchester)

Our knowledge of dinosaurian braincases and the structure of their endocranial cavities has a surprisingly long history. The first well-preserved braincase (NHMUK R2501) was found almost 150 years ago in the Isle of Wight and was described as probably belonging to Iguanodon. In 1897, Charles William Andrews – using the same specimen – suggested that dinosaurian brains, and in particular their lobes and surface convolutions, were not closely pressed against the cranial wall. Almost sixty years later, John Ostrom published a study on the anatomy of the hadrosaurian dinosaurs of North America and reinforced the general opinion that they had brains that were not packed tightly within the braincase. Previously, Alfred Romer observed that the interior walls of reptile braincases reflect the shape of the brain at an early state of its development. Now, a team of paleontologists from the University of Cambridge and the University of Western Australia uncovered the first fossilized brain tissue from a dinosaur.

The extraordinary specimen is likely to have belonged to a species related to Iguanodon, which lived around 133 million years ago. It was found in 2004 by fossil hunter Jamie Hiscocks, near Bexhill in Sussex. Fossilized footprints and trackways of Iguanodon-like ornithopods were found at a similar stratigraphic level.

Images of (a) the Bexhill iguanodontian natural endocast specimen and (b) a computed tomography. Scale bar: 10 mm (From Brasier et al., 2016)

Images of (a) the Bexhill iguanodontian natural endocast specimen and (b) a computed tomography. Scale bar: 10 mm (From Brasier et al., 2016)

The natural cranial endocast was unusually well preserved along its dorsolateral flanks, corresponding to the approximate position of the cerebellum. A scanning electron microscopy (SEM) revealed detailed structures, interpreted as meningeal fabrics, blood vessels and potentially superficial cortical tissues, which have been replaced by calcium phosphate or moulded by microcrystalline iron carbonate. The meningeal structures show similarities with those seen in crocodiles and birds. The areas occupied by the forebrain lobes and hypothalamus were well developed, so it’s reasonable to suppose that iguanodontian dinosaurs of this type had moderately complex behaviour similar to modern crocodilians.

To preserve soft tissue as phosphate is necessary a locally anoxic environment to promote bacterially mediated mineralization. Under freshwater conditions, eutrophication adds phosphate to the water column in the form of a phosphoric acid series that reduce the pH of the water, rapidly fixing soft tissues, and dissolving the surrounding mineralized tissues. As result, the soft tissues associated with the brain could have been preserved and cast prior to complete burial by sediment (Brasier et al., 2016).

References:

Martin D. Brasier et al.’ Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur.’ Earth System Evolution and Early Life: a Celebration of the Work of Martin Brasier. Geological Society, London, Special Publications, 448. (2016). DOI: 10.1144/SP448.3
Ostrom, J.H. 1961. Cranial anatomy of the hadrosaurian dinosaurs of North America. Bulletin of the American Museum of Natural History, 122, 35–196

Forgotten women of Paleontology: Erika von Hoyningen-Huene

Erika von Huene in the lates 1920s at the Tuebingen University.

Erika von Huene at Tübingen.

Erika Martha von Hoyningen-Huene was born in Tübingen, Germany, on September 30, 1905.  Descendant of a noble Baltic German family, Erika grew up in a deeply religious home. Her father,  Professor Dr Friedrich Freiherr (Baron) von Hoyningen, better known as Friedrich von Huene (1875–1969), was a world expert palaeontologist, whose life and research were strongly influenced by his beliefs. Von Huene wrote several books, papers and articles, spanning 65 years, but he never gained a full professorial position. Instead, he took the position of  Konservator at the University of Tübingen. As a young girl, Erika helped her father in the Institute and Museum of Geology and Palaeontology and studied under his strong influence.

She was one of only two female vertebrate palaeontologists in the pre-World War II history of Germany.  She completed her doctorate under the supervision of Prof. Dr Edwin Hennig in 1933, the same year that Hitler came to power. She later contributed with George Gaylord Simpson with her pioneering work on early mammals. But  the Nazi regime affected her life and work. During those difficult years, her father used his influence to help persecuted colleagues, such as ‘Tilly’ Edinger. However, after the events that followed the infamous “Kristallnacht” (Night of the Broken Glass), Tilly Edinger’s paleontological career in Germany ended abruptly.

Friedrich on Huene contemplating the placement of a rib on a South African dicynodont specimen (From Turner 2009)

Friedrich von Huene contemplating the placement of a rib on a South African dicynodont specimen (From Turner 2009)

When World War II began, Erika moved to Berlin invited by her former professor Otto H. Schindewolf, and carried out some work for him in the geological survey. After the war ended, Erika lost her job. For a time, she assisted his father and published her last paper in 1949. Her last years were devoted to managing nursing homes in Tübingen and Berlin. She died in Berlin, almost a week after her father’s death, on April 9, 1969.

During her scientific career, Erika wrote only seven papers. She suffered the consequences of the discrimination against women in Germany and finally gave up. In the year that Erika gained her doctorate, promotion for women in Germany was denied and women in higher positions were downgraded, and by the time  the war ended and men returned to their jobs, most women returned to the “safety of their homes”.

References:

Susan Turner, Cynthia V. Burek and Richard T. J. Moody, Forgotten women in an extinct saurian (man’s) world, Geological Society, London, Special Publications 2010, v. 343, p. 111-153

S. Turner, 2009, Reverent and exemplary: ‘Dinosaur man’ Friedrich von Huene (1875-1969), Geological Society London Special Publications 310(1):223-243

Murusraptor barrosaensis, a new species in the megaraptorid clade.

Body reconstruction of Murusraptor barrosaensis (From Coria et al., 2016)

Body reconstruction of Murusraptor barrosaensis (From Coria et al., 2016)

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 Megaraptor, Orkoraptor and Aerosteon, 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 (Novas et al, 2013). The enigmatic nature of this group has been a matter of discussion since the description of the first megaraptoran, Megaraptor namunhaiquii. For years, Megaraptor has been alternatively interpreted as belonging to different theropod lineages: as basal coelurosaurians (Novas,1998), basal tetanurans (Calvo et al.,2004; Smith et al., 2008), and allosauroids closely related with carcharodontosaurids (Smith et al., 2007; Benson et al., 2010; Carrano et al., 2012). The main reason for so many different interpretations is the incomplete nature of most available megaraptorid skeletons and the little information about their cranial anatomy.

Murusraptor barrosaensis, from the Upper Cretaceous of Neuquén Province, Argentina, belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor. Murusraptor, meaning “Wall Raptor”, was discovered in a canyon wall in 2001 during an expedition to Sierra Barrosa in northwestern Patagonia. The holotype specimen includes much of the skull, axial skeleton, pelvis and tibia. The braincase is intact and most of the sutures are still visible, indicating that this was not a fully mature animal.

Different appendicular elements of Murusraptor in their original burial positions (From Coria et al., 2016)

Different appendicular elements of Murusraptor in their original burial positions (From Coria et al., 2016)

Murusraptor barrosaensis is unique in having anterodorsal process of lacrimal longer than height of preorbital process; sacral ribs hollow and tubelike; short ischia distally flattened and slightly expanded dorsoventrally.

Murusraptor shares with all Megaraptoridae two unambiguous synapomorphies: teeth with no enamel wrinkles (interpreted as a reversion to primitive condition in Theropoda); and anterior caudal vertebrae with neural arch bearing prominent centrodiapophysial laminae that define a deep infradiapophysial fossa. Murusraptor also exhibits some characters that are interpreted as convergencies of this taxon with non-tyrannosauroid theropods, including lacrimal with a small pneumatic recess; and a highly pneumatic braincase (Coria et al., 2016)

References:

Rodolfo A. Coria, Philip J. Currie. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLOS ONE, 2016; 11 (7): e0157973 DOI: 10.1371/journal.pone.0157973

Porfiri, J. D., Novas, F. E., Calvo, J. O., Agnolín, F. L., Ezcurra, M. D. & Cerda, I. A. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research 51: 35-55.

 

Introducing Gualicho.

Gualicho shinyae, at the Centro Cultural de la Ciencia.

Gualicho shinyae, at the Centro Cultural de la Ciencia.

The Cretaceous beds of Patagonia have yielded the most comprehensive record of Cretaceous theropods from Gondwana and includes at least five main theropod lineages: Abelisauroidea, Carcharodontosauridae, Megaraptora, Alvarezsauridae, and Unenlagiidae. The best represented theropod clades in the Late Cretaceous terrestrial strata of the Neuquén Basin are the Abelisauroidea and the Carcharodontosauridae. The  Abelisauroidea has been divided in two main branches: the Noasauridae which includes the small-sized abelisauroids, and the Abelisauridae which comprises medium to large-sized animals, like the popular Carnotaurus sastrei. The group exhibits strongly reduced forelimbs and hands, stout hindlimbs, with a proportionally robust and short femur and tibia.  The Carcharodontosauridae includes the largest land predators in the early and middle Cretaceous of Gondwana, like the popular, Giganotosaurus carolinii. The group evolved large skulls surpassing the length of the largest skull of Tyrannosaurus rex.  Another common trait is the fusion of cranial bones. Gualicho shinyae gen. et sp. nov, a partially articulated mid-sized theropod (about 7.6m long and 450kg in weight) represents a new tetanuran theropod taxon from the Huincul Formation.

Articulated right foot of the holotype of Gualicho shinyae during excavation (from Apesteguía et al., 2016)

Articulated right foot of the holotype of Gualicho shinyae during excavation (from Apesteguía et al., 2016)

The new specimen exhibits a new and unusual combination of characters observed in various remotely related clades including ceratosaurs, tyrannosaurids, and megaraptorans. The didactyl manus with a semilunate distal carpal are indicative of derived tetanuran affinities, while the expanded posterior margin of the metatarsal III proximal articulation, are shared with ceratosaurs. The reduced forelimbs with didactyl manus are similar to those of the tyrannosaurids. However, in tyrannosaurids, the carpal elements are reduced and proximodistally flattened, whereas in Gualicho the semilunate and scapholunare carpals retain a more complex shape typical of the carpal elements of most non-coelurosaurian tetanurans. In addition, the manus of Gualicho differs from tyrannosaurids in having a proportionately more robust metacarpal I with a rectangular, rather than triangular, proximal articulation in end view (Apesteguía et al., 2016).

Left humerus of the of the holotype specimen of Gualicho shinyae (MPCN PV 0001) in (A) anterior, (B) posterior, (C) proximal, and (D) distal views. Abbreviations: dpc, deltopectoral crest; ics, intercondylar sulcus; it, internal tuberosity; msh, scar for insertion of m. scapulohumeralis (From Apesteguía et al., 2016).

Left humerus of the of the holotype specimen of Gualicho shinyae (MPCN PV 0001) in (A) anterior, (B) posterior, (C) proximal, and (D) distal views. Abbreviations: dpc, deltopectoral crest; ics, intercondylar sulcus; it, internal tuberosity; msh, scar for insertion of m. scapulohumeralis (From Apesteguía et al., 2016).

Gualicho shares several derived characters with the African theropod Deltadromeus, including reduced distal humeral articulations, and an expanded lobe bearing a medial trough on the proximocaudal aspect of the fibula. The faunal resemblances between strata in the Neuquén and San Jorge Basins of Patagonia and North African Cenomanian beds are intriguing, but difficult to interpret due to a lack of well sampled, age equivalent strata elsewhere.

Gualicho was discovered on a paleontological expedition led by Sebastian Apesteguía in 2007. The name derived from the Gennaken (Northern Tehuelche languaje) watsiltsüm, an old goddess now considered a source of misfortune. The name was chosen to reflect the difficult circumstances surrounding the discovery and study of the specimen. The specific name honors Ms. Akiko Shinya, Chief Fossil Preparator at the Field Museum.

References:

Apesteguía S, Smith ND, Juárez Valieri R, Makovicky PJ (2016) An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina. PLoS ONE 11(7): e0157793. doi: 10.1371/journal.pone.0157793

Once upon a time, there was a Dodo.

Painting of the Dodo by Roelandt Savery executed in ca. 1626 and held at the NHMUK, London.

Painting of the Dodo by Roelandt Savery executed in ca. 1626 and held at the NHMUK, London.

The Dodo (Raphus cucullatus Linnaeus, 1758) a giant, flightless pigeon endemic to the Mascarene island of Mauritius, became extinct just three centuries ago. As one of the earliest species to be identified as extinct, the Dodo gained tremendous celebrity throughout the nineteenth and twentieth centuries. It was first used as the prime example of a species wiped out by recent human activity in the Penny Magazine (Broderip 1833; reprinted in the Penny Cyclopaedia), where the author wrote that: “The agency of man, in limiting the increase of the inferior animals, and in extirpating certain races, was perhaps never more strikingly exemplified than in the case of the Dodo. That a species so remarkable in its character should become extinct, within little more than two centuries, so that the fact of its existence at all has been doubted, is a circumstance which may well excite our surprise, and lead us to a consideration of similar changes which are still going on from the same cause.”

Much greater public awareness of the Dodo’s demise followed publication of the monograph The Dodo and Its Kindred (Strickland and Melville 1848). Shortly after, a life-size reconstruction of a Dodo was displayed in 1851 at the Great Exhibition in London and later exhibited at the Crystal Palace at Sydenham. Even Lewis Carroll featured the Dodo as a character in Alice’s Adventures in Wonderland and firmly established the bird as a popular figure in Victorian culture.

The Oxford dodo head (From Wikimedia Commons)

The Oxford dodo head (From Wikimedia Commons)

In 1828, John Duncan, curator at the Ashmolean Museum, described a desiccated dodo head and foot held at the museum. In 1842, John Theodore Reinhardt, a Danish professor, examined a second dodo skull at the Copenhagen Museum and concluded that it was a giant pigeon. Prior to Reinhardt’s proposal, the Dodo had variously been considered a diminutive ostrich, a rail, or even a kind of vulture.

The publication of ‘Alice’s Adventures in Wonderland’ coincided with a spectacular discovery of subfossil dodo bones from a marsh called the Mare aux Songes in Mauritius in 1865.  George Clark, discoverer of the fossil site, sent consignments of bones initially to Richard Owen  and subsequently to Alfred Newton. A year later, Owen described the bones in Memoir on the Dodo. He reconstructed the bird using the most famous of the contemporary Dodo paintings, one by the Dutch artist Roelandt Savery. Three years later, Owen rectified his mistake by reconstructing the bird in a natural more upright position.

Amateur naturalist and barber Louis Etienne Thirioux (1846–1917),  collected two of the most important dodo skeletons known to science around the turn of the 19th century. Thirioux’s dodos were discovered in the foothills and valleys of Le Pouce and surrounding mountains, but their exact provenance has not been recorded.

Owen’s (1866) original reconstruction of the dodo.

Owen’s (1866) original reconstruction of the dodo.

In 1896, Hilaire Belloc wrote a beautiful poem about the dodo in his Bad Child’s Book of Beasts.

The Dodo used to walk around,
And take the sun and air.
The sun yet warms his native ground –
The Dodo is not there!

The voice which used to squawk and squeak
Is now for ever dumb –
Yet may you see his bones and beak
All in the Mu-se-um.

References:

Kenneth F. Rijsdijk, Julian P. Hume, Perry G. B. De Louw, Hanneke J. M. Meijer, Anwar Janoo, Erik J. De Boer, Lorna Steel, John De Vos, Laura G. Van Der Sluis, Henry Hooghiemstra, F. B. Vincent Florens, Cláudia Baider, Tamara J. J. Vernimmen, Pieter Baas, Anneke H. Van Heteren, Vikash Rupear, Gorah Beebeejaun, Alan Grihault, J. (Hans) Van Der Plicht, Marijke Besselink, Juliën K. Lubeek, Max Jansen, Sjoerd J. Kluiving, Hege Hollund, Beth Shapiro, Matthew Collins, Mike Buckley, Ranjith M. Jayasena, Nicolas Porch, Rene Floore, Frans Bunnik, Andrew Biedlingmaier, Jennifer Leavitt, Gregory Monfette, Anna Kimelblatt, Adrienne Randall, Pieter Floore & Leon P. A. M. Claessens (2015) A review of the dodo and its ecosystem: insights from a vertebrate concentration Lagerstätte in Mauritius, Journal of Vertebrate Paleontology, 35: sup1, 3-20, DOI: 10.1080/02724634.2015.1113803

Turvey, S. T.; Cheke, A. S. (2008). “Dead as a dodo: The fortuitous rise to fame of an extinction icon”. Historical Biology 20 (2): 149–163

The First 100 Million Years of Avian History.

The basal avian Sapeornis chaoyangensis (From Wikimedia Commons)

The basal avian Sapeornis chaoyangensis (From Wikimedia Commons)

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. The Jehol Biota is formed from two formations: the Yixian Formation, and the Jiufotang Formation, and contain the most diversified avifauna known to date. 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 and Ornithuromorpha. The last two groups, form the clade Ornithothoraces, characterized by a keeled sternum, elongate coracoid, narrow furcula, and reduced hand.

Ornithuromorphs, include Gansus, Patagopteryx, Yixianornis, and Apsaravis, which form a grade on the line to Ornithurae, a derived subgroup that includes modern birds and their closest fossil relatives (Brusatte et al., 2015).

The single best record of a Cretaceous neornithine is the partial skeleton of Vegavis from the latest Cretaceous (around 68–66 million years ago) of Antarctica.

Zhenyuanlong suni (photo by Junchang Lu¨ ) from the Jehol Biota.

Zhenyuanlong suni (photo by Junchang Lu) from the Jehol Biota.

Anatomical features like aspects of egg shape, ornamentation, microstructure, and porosity of living birds trace their origin to the maniraptoran theropods, such as oviraptorosaurs and troodontids. In addition, some preserving brooding postures, are known for four oviraptorosaurs, two troodontids, a dromaeosaur, and one basal bird providing clear evidence for parental care of eggs.

In birds, particularly their forebrains, are expanded relative to body size. Birds also exhibit the most advanced vertebrate visual system, with a highly developed ability to distinguish colors over a wide range of wavelengths.

Feathers were once considered to be unique avialan structures. The megalosaurus Sciurumimus, the compsognathus Sinosauropteryx, and a few other dinosaurs, document the appearance of primitive feathers. Zhenyuanlong suni, from the Yixian Formation, provides the first evidence of well-developed pennaceous feathers in a large, non-flying dromaeosaur. Evidence indicates that the earliest feathers evolved in non-flying dinosaurs, likely for display and/or thermoregulation, and later were co-opted into flight structures in the earliest birds (Brusatte et al., 2015).

The basal avian Jeholornis prima.

The basal avian Jeholornis prima.

The evolution of flight involved a series of adaptive changes at the morphological and molecular levels, like the fusion and elimination of some bones and the pneumatization of the remaining ones. Archaeopteryx lacked a bony sternum and a compensatory specialized gastral basket for anchoring large flight muscles (O’Connor et al., 2015), while Jelohornis had several derived flight-related features of modern birds like fused sacral vertebrae, an elongated coracoid with a procoracoid process, a complex sternum, a narrow furcula, and curved scapula. In Enantiornithines, their robust pygostyle appears to have been unable to support the muscles that control the flight feathers on the tail in modern birds. The increased metabolism associated with homeothermy and powered flight requires an efficient gas exchange process during pulmonary ventilation. Recent anatomical and physiological studies show that alligators, and monitor lizards exhibit respiratory systems and unidirectional breathing akin to those of birds, which indicate that unidirectional breathing is a primitive characteristic of archosaurs or an even more inclusive group with the complex air-sac system evolving later within Archosauria.

The earliest diversification of extant birds (Neornithes) occurred during the Cretaceous period and after the mass extinction event at the Cretaceous-Paleogene (K-Pg) boundary, the Neoaves, the most diverse avian clade, suffered a rapid global expansion and radiation. A genome-scale molecular phylogeny indicates that nearly all modern ordinal lineages were formed within 15 million years after the extinction, suggesting a particularly rapid period of both genetic evolution and the formation of new species. Today, with more than 10500 living species, birds are the most species-rich class of tetrapod vertebrates.

 

References:

Brusatte, S. L., O’Connor, J. K., and Jarvis, E. D. 2015. The origin and diversification of birds. Current Biology, 25, R888-R898

Padian, K., and Chiappe, L.M. (1998). The origin and early evolution of birds. Biol. Rev. 73, 1–42.

Puttick, M. N., Thomas, G. H. and Benton, M. J. (2014), HIGH RATES OF EVOLUTION PRECEDED THE ORIGIN OF BIRDS. Evolution, 68: 1497–1510. doi: 10.1111/evo.12363 A.

Xing Xu, Zhonghe Zhou, Robert Dudley, Susan Mackem, Cheng-Ming Chuong, Gregory M. Erickson, David J. Varricchio, An integrative approach to understanding bird origins, Science, Vol. 346 no. 6215, DOI: 10.1126/science.1253293.