Caihong juji: A new species of Deinonychosaur from the Middle-to-Late Jurassic Yanliao Biota of Hebei Province, China.

The Yanliao Biota of northeastern China outcrops across much of  western Liaoning, northern Hebei, and southeastern Inner Mongolia provinces, providing a series of deposits with exceptional preservation laid down over a period of about 10 million years in terrestrial settings. These deposits include the Daohugou phase (about 168–164 million years ago) and the Oxfordian Linglongta phase (164–159 million years ago). These fossils provide a valuable insight into a variety of emerging taxa in across the boundary between the Middle and Late Jurassic, including Insects, Mammals and Paravian Dinosaurs, the group which includes Dromaeosaurs, Troodontids and Birds.

In a paper published in the journal Nature Communications on 15 January 2018, Dongyu Hu of the Paleontological Museum of Liaoning at Shenyang Normal University, Julia Clarke of the Department of Geological Sciences and Integrated Bioscience at the University of Texas at Austin, Chad Eliason, also of the Department of Geological Sciences and Integrated Bioscience at the University of Texas at Austin, and of the Integrative Research Center at the Field Museum of Natural History, Rui Qiu, also of the Paleontological Museum of Liaoning at Shenyang Normal University, Quanguo Li of the State Key Laboratory of Biogeology and Environmental Geology at the China University of Geosciences, Matthew Shawkey of the Evolution and Optics of Nanostructures Group at the University of Ghent, Cuilin Zhao, again of the Paleontological Museum of Liaoning at Shenyang Normal University, Liliana D’Alba also of the Evolution and Optics of Nanostructures Group at the University of Ghent, Jinkai Jiang, once again of the Paleontological Museum of Liaoning at Shenyang Normal University, and Xing Xu of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, describe a new species of Paravian Dinosaur from the Late Jurassic Tiaojishan Formation of northern Hebei.

The new species is named Caihong juji, where 'Caihong' means 'rainbow' and 'juji' means 'big crest'. It is described from a single, almost complete skeleton and associated plumage preserved as part and counterpart on a split slab. The specimen is estimated to have been about 400 mm in length, and to have weighed about 475 g when it was alive, and is thought to have been an adult. It had a pair of prominent crests on its lacrimal bones (the bone that joins the nose to the eye-socket in Humans, and the hind-part of the snout in Theropod Dinosaurs), something very unusual in Paravians. Caihong juji is assessed to have been a Deinonychosaur on the basis of its anatomy (i.e. the sub-group of Paravians that includes Dromaeosaurs ans Troodontids, but not Birds.

Caihong juji. Photographs of the slab (a) and counter slab (b) and line drawing (c) of the specimen based on both slabs. Photograph (d) and line drawing (e) of a composite of the rostrum of the skull and mandible exposed on the counter slab and the post-rostrum cranium exposed on the slab. Arrows indicate lacrimal crests. Question mark indicates uncertain identification. Scale bars: 10 cm in (a)–(c), 1 cm in (d) and (e). Abreviations aof, antorbital fenestra; cav, caudal vertebra; cev, cervical vertebra; dr, dorsal rib; dv, dorsal vertebra; ect, ectopterygoid; emf, external mandibular fenestra; en, external naris; f, feather; fu, furcula; ga, gastralia; hy, hyoid; il, ilium; is, ischium; la, left angular; lar, left articular; lc, left coracoid; lcr, lacrimal crest; ld, left dentary; lf, left frontal; lfe, left femur; lh, left humerus; lj, left jugal; ll, left lacrimal; lma, left maxilla; lm, left manus; ln, left nasal; lp, left pes; lpa, left palatine; lpo, left postorbital; lq, left quadrate; lqj, left quadratojugal; lr, left radius; ls, left scapula; lsp, left splenial; lsa, left surangular; lsq, left squamosal; lt, left tibiotarsus; lu, left ulna; ma, mandible; mf, maxillary fenestra; o, orbit; p, parietal; pm, premaxilla; pt, pterygoid; pu, pubis; rar, right articular; rc, right coracoid; rd, right dentary; rfe, right femur; rh, right humerus; rm, right manus; rp, right pes; rpra, right prearticular; rq, right quadrate; rr, right radius; rs, right scapula; rt, right tibiotarsus; ru, right ulna; scl, sclerotic bones; sk, skull; sy, synsacrum. Hu et al. (2018).

Much of the plumage of Caihong juji is exceptionally well preserved, retaining the microstructure of the melanosomes (pigment cells). Comparison of these cells to those of modern Birds leads Hu et al. to conclude that this Jurassic Dinosaur had brightly coloured iridescent plumage.

Platelet-like nanostructures in Caihong juji and melanosomes in iridescent extant feathers. (a)–(d) Fossilized nanostructures from Caihong feathers preserved as molds in a neck feather (a) and three-dimensional preservation in a neck feather, with SEM stage rotated 45° to show 3D platelet morphology; (b) a back feather with SEM stage at 0° (c) and a neck feather showing nanostructure packing; (d), (e) Anna’s Hummingbird, Calypte anna, showing overlapping melanosomes within a feather barbule; (f) White-tailed Starfrontlet, Coeligena phalerata, showing stacking and interior morphology (air bubbles) of melanosomes in a feather barbule; (g) Black-tailed Trainbearer, Lesbia victoriae, showing exterior surface and morphology of isolated melanosomes in a feather barb; (h) Moustached Treeswift, Hemiprocne mystacea, showing densely packed melanosomes in the barbule of a crown feather. Inset in (d) illustrates 3D stacking of platelet-shaped nanostructures. All scale bars are 1000 nm. Hu et al. (2018).

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An Enantiornithine Bird Hatchling preserved in Cretaceous Burmese Amber.

Most Dinosaurs, including Mesozoic Birds, are known only from replacement fossils of bones, teeth, and other hard tissues, with a few rare sites such as the lithographic deposits of the Jehol or Crato biotas, or even rarer examples of Dinosaurs mummified before lithification, preserving additional details such as plumage and soft tissues. One type of deposit with potential for excellent preservation of plumage and soft tissues is amber, the preserved resin of ancient trees, which frequently preserves whole body fossils of Insects and other small animals. However Amber fragments, by their nature, tend to be very small, whereas Dinosaurs, for the most part, were extremely large, limiting the potential for the preservation of even Avian Dinosaurs in amber. To date, the known catalogue of Dinosaur specimens preserved in amber runs to a few feathers, a pair of Enantiornithine Bird wings and the tip of the tail of a small non-Avian Coelurosaurian Theropod.

In a paper published in the journal Gondwana Research on 6 June 2017, Lida Xing of the State Key Laboratory of Biogeology and Environmental Geology and School of the Earth Sciences and Resources at the China University of Geosciences, Jingmai O'Connor of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Ryan McKellar of the Royal Saskatchewan Museum, the Biology Department at the University of Regina, and the Department of Ecology & Evolutionary Biology at the University of Kansas, Luis Chiappe of the Dinosaur Institute at the Natural History Museum of Los Angeles County, Kuowei Tseng of the Department of Exercise and Health Science at the University of Taipei, Gang Li of the Institute of High Energy Physics of the Chinese Academy of Science, and Ming Bai of the Key Laboratory of Zoological Systematics and Evolution of the Institute of Zoology of the Chinese Academy of Sciences, describe a preserved Hatchling Enantiornithine Bird from a piece of amber from the Angbamo site at Tanai Township in Myitkyina District of Kachin Province in northern Myanmar.

Middle Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber. 

The preserved Hatchling is not intact, having apparently only partly covered by resin initially, with part of the body therefore left exposed to the actions of the elements, and scavengers, and hence lost; the whole subsequently covered by additional layers of resin, and eventually preserved as amber. The remains are preserved in a block of amber approximately 86 mm x 30 mm x 57 mm and weighing 78.16 g. This block has been split into two sections during preservation; this split having unfortunately passed through part of the jaw, causing some loss of material. The remains comprise the head and most of the neck of the Bird, as well as a partial wing and the feet, and some additional plumage and soft tissue.

Overview of specimen in right lateral view. (A) Amber specimen; (B) x-ray μCT reconstruction; (C) illustration of observable plumage and skin sections. Two halves of amber piece have been positioned side by side (A) or separated by dashed line (C), and body regions scanned separately have been arranged in preservational position (B). For clarity in (C), only rachises of apical remiges indicated; and only rachises and rami of basal remiges, coverts, contours, and neoptile plumage indicated. Scale bars represent 10 mm. Xing et al. (2017).

The Bird appears to have two basic types of plumage, soft down feathers similar to those seen in modern Bird chicks, combined with longer fibrous feathers similar to those seen in many Dinosaurs, as well as some developed flight feathers on the wing. The skeleton is consistent with that of other preserved early-development Enantiornithine chicks, lending confidence to the diagnosis of this bird as an Enantiornithine. The developmental strategy in this Bird appears to have been different to that in modern Birds, in that it was apparently both arboreal (tree-dwelling) and precocial (able to move about immediately upon hatching). Modern Birds almost invariably follow one of two strategies; with tree-nesting species tending to need a period of care before leaving the nest (though many species do leave the nest before they can fly) and ground-nesting Birds producing precocial offspring that become active almost immediately.

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Understanding the integument of Tyrannosaurid Dinosaurs.

Many recent discoveries of Theropod Dinosaurs have revealed traces of feather coverings, leading to speculation that all members of this group may have been feathered. The discovery of the feathered Tyrannosaurids, Dilong paradoxus and Yutyrannus huali, from the Early Cretaceous of China, has extended this speculation to the very largest Tyrannosaurid Dinosaurs, particularly as Yutyrannus itself was a large Tyrannosaurid (about nine meters) with an extensive feather coat, raising the possibility that the largest known Therapod Dinosaur, Tyrannosaurus rex, might have had feathers.

In a paper published in the journal Biology Letters on 7 June 2017, Phill Bell of the University of New England, Nicolás Campione of the Palaeobiology Programme at Uppsala University, Scott Persons and Philip Currie of the University of Alberta, Peter Larson of the Black Hills Institute of Geological Research, Darren Tanke of the Royal Tyrrell Museum of Palaeontology and Robert Bakker of the Houston Museum of Natural Science, describe the results of a study of skin traces from Tyrannosaurus rex and several other large Tyrannosaurids, and draw conclusions about the evolution of skin covering of Tyrannosaurid Dinosaurs from this study.

Bell et al. examined a number of skin traces associated with a Tyrannosaurus specimen collected from the Hell Creek Formation near Baker in Montana (specimen HMNS 2006.1743.01, sometimes known as ‘Wyrex’). This specimen has numerous skin patches from different parts of its body, none of which show any trace of feathers, leading Bell et al. to conclude it was featherless. The scales of HMNS 2006.1743.01 are small in size and highly variable in shape, with no larger feature scales (known from other Dinosaur species) and no scales showing polarity (i.e. having a distinct anterior-posterior axis, presumably the first step in developing towards a feather-like form). Interestingly, in several places where large patches of skin are preserved, these scales show signs of being arranged into a leaf-like pattern, with scales arranged into trapezoidal or triangular clusters, separated by bands of incised interstitial skin, which follow a branching arrangement similar to the midrib and lateral veins on a plant leaf. 

 

Integument of Tyrannosaurus rex (HMNS 2006.1743.01). (a) Proximal caudal vertebrae 6–8 in right lateral view. Integument from the neck (b,c), the ilium (d,e) and caudal vertebrae (f–h). Green lines indicate ‘vein and midrib’ patterns. Scale in (a) is 10 cm; (b)–(e) are 5 mm and (f)–(h) are 10 mm. Bell et al. (2017).

Next Bell et al. examined preserved skin specimens from four other large, Late Cretaceous Tyrannosaurs, Daspletosaurus, Tarbosaurus, Albertosaurus, and Gorgosaurus. Unlike the Early Cretaceous Chinese specimens, none of these Late Cretaceous North American and Mongolian Tyrannosaurs show any signs of feathers. 

The distribution of feathers among Theropod Dinosaurs suggests that at least primitive feathers (i.e. hollow tubes) were present in the earliest Coelurosaurs, the group to which the Tyrannosaurs belong, with more advanced features such as rachis, barbs and barbules and eventually fully formed flight feathers appearing sequentially within Maniraptoran Theropods and eventually Birds. Some Ornithischian Dinosaurs also had primitive feathers, suggesting that either simple feathers appeared before the two groups diverged, or that they evolved separately in the two groups. No trace of feathers or feather-like structures has ever been found in any Sauropod Dinosaur. 

Like other Coelurosaurs, the earliest Tyrannosaurs appear to have had a full coat of simple, fibrous feathers, and as in other non-avian Theropods, no Tyrannosaur has been found with evidence of a partial-feather covering. Indeed, the earliest Birds, such as Archaeopteryx, appear to have been completely covered in feathers, with the scaly feet and legs of modern Birds apparently secondarily derived. This strongly suggests that the scaly skin of later Tyrannosaurs is also secondarily derived from a feathery covering. 

The earliest Tyrannosaurs were relatively small animals, with gigantism achieved twice within the group, once rapidly, in the Early Cretaceous lineage that led to Yutyrannus, and once more gradually over the course of the Cretaceous in the lineage that culminated in Daspletosaurus, Tarbosaurus, Albertosaurus, Gorgosaurus and Tyrannosaurus. This is important, as it shows that Yutyrannus is not the ancestor of the Late Cretaceous giant Tyrannosaurs, and that it therefore presumably evolved under different ecological and evolutionary pressures to these animals, and that understanding these pressures may be the key to understanding the distribution of feathers among Tyrannosaurids. 

Some earlier studies have suggested that temperatures in Early Cretaceous western Liaoning (where Dilong paradoxus and Yutyrannus huali lived) may have been significantly cooler than the North American and Mongolian environments that produced the Late Cretaceous giant Tyrannosaurs, leading these Early Cretaceous forms to need an insulating feather coat that the Late Cretaceous forms lacked. However recent palaeoenvironmental studies have not supported this, implying a similar temperature range. One difference that may be important is tree-cover, with the Liaoning deposits thought to have been laid down in a dense forest environment, while the later Cretaceous Tyrannosaurids are believed to have inhabited more open environments. This reflects the case in modern Asian Elephants and Javan Rhinoceroses, which are live in dense forest environments and are hairier than their African relatives that live on open Savanah. While all of these animals live in hot climates, and are more concerned with losing excess heat that keeping warm (always more of a problem for large animals anyway), the Asian forms, which live beneath the shade of large trees, are apparently subject to less heat-stress than the African forms. 

However the Late Cretaceous Tyrannosaurids are known to have lived alongside feathered Dinosaurs, with Albertosaurus in particular having been found alongside feathered Ornithomimids. Bell et al. suggest that the feather-loss in Tyrannosaurids compared to Maniraptorans (such as the Ornithomimids) may be related to a more active lifestyle, i.e. expending more energy and therefore generating more body-heat. Tyrannosaurs had relatively longer legs than other large Theropods, and arctometatarsalian feet (expand), which has been interpreted as being indicative of a more active lifestyle, possibly even engaging in bouts of rapid or lengthy pursuit (generally the only ways for a large predator in an open environment to catch prey, since opportunities for ambush are relatively limited). 

Finally, the Late Cretaceous Tyrannosaurs grew considerably larger than the Early Cretaceous forms, with only the smallest, Albertosaurus, at an estimated 1325–2210 kg is thought to be comparable in size to Yutyrannus, at about 1414 kg, while the other species were much larger; Tarbosaurus at 1744–2945 kg, Gorgosaurus at 2145–3577 kg, and Tyrannosaurus at 5014–8361 kg, suggesting that these species would have been subject to more heat-stress. 

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Zhenyuanlong suni: A large feathered Dromaeosaur from the Jehol Biota.

Dromaeosaurid Dinosaurs are among the closest non-Avian relatives of the Birds and show many similarities to the earliest members of that group, making understanding Dromaeosaurs important for understanding the origin of Birds. In particular many Dromaeosaur specimens from the Early Cretaceous of Liaoning Province, China, have been shown to possess extremely Bird-like feather coats, and in several cases feathered wings which may have allowed them to fly. This is particularly interesting as the Liaoning specimens are not thought to represent a tight monophyletic group (i.e. a group of species more closely related to one-another than anything else), but rather a diverse group of Dromaeosaurs with exceptional preservation, part of the Jehol Biota of exceptionally well preserved Early Cretaceous fossils, suggesting that feathers were also present in Dromaeosaurs from other locations even if they have not been preserved. The smallest and most numerous Liaoning Dromaeosaurs are placed in the genus Microraptor and may (or may not) represent several species of small (cat-sized) Dinosaurs fully capable of flight, while the largest, Tianyuraptor, is a much larger animal with reduced fore-limbs highly unlikely to have been capable of supporting it in flight. Unfortunately Tianyuraptor is known only from a single specimen lacking feathers; it is impossible to determine whether this species was truly featherless from a single specimen, nor to speculate about what sort of feathers it may have possessed.

In a paper published in the journal Nature Scientific Reports on 16 July 2015, Junchang Lü of the Institute of Geology of the Chinese Academy of Geological Sciences and the Key Laboratory of Stratigraphy and Paleontology of the Ministry of Land and Resources of China and Stephen Brusatte of the School of GeoSciences at the University of Edinburgh, describe a new species of Dromaeosaur from the Yixian Formation of Jianchang County in Liaoning Province.

The new species is named Zhenyuanlong suni, honouring Zhenyuan Sun who discovered the specimen; the suffix ‘-long’ means ‘Dragon’ in Chinese, making ‘Zhenyuanlong suni’ ‘Zhenyuan Sun’s Dragon’. The specimen comprises an almost complete specimen preserved on in two dimensions on three separate blocks, with only the end part of the tail missing. The specimen is 126.6 cm in length, but it is thought to have been about 165 cm long in life. Not all of the vertebrae fused in adult Dinosaurs are fully fused in this specimen, leading Lü and Brusatte to conclude it was a subadult at the time when it died.

The holotype of the large-bodied Liaoning Dromaeosaurid Zhenyuanlong suni. Lü & Brusatte (2015).

Like Tianyuraptor, Zhenyuanlong suni has relatively small forelimbs for the size of its body, however unlike Tianyuraptor an extensive feather coating is preserved on all of Zhenyuanlong suni except its hindlimbs (these are preserved on a separate block which does not contain any feathers, making it hard to assess whether feathers were originally present on the hindlimbs; feathered hindlimbs are common in both smaller Dromaeosaurs and early Birds). Notably these show layered feathers similar to those seen in modern Birds and Microraptor.

The integument of the large-bodied, short-armed Liaoning Dromaeosaurid Zhenyuanlong suni. (A) Overview of the skeleton with regions of integument indicated with grey highlight; (B) proximal tail; (C) left forearm; (D) right forearm; (E) closeup of coverts on right forearm. Lü & Brusatte (2015).

Without a full biomechanical analysis (which has not been carried out for Zhenyuanlong suni at the time of writing) it is impossible to say whether or not it was capable of flying or gliding, but the combination of a large body size and small forelimbs makes this seem somewhat unlikely, leading to support for the alternative theory that feathered wings were first developed for some other purpose in Bird-like Dinosaurs and later co-opted for flight in Birds and possibly some small Dromaeosaurs. This is not uncommon as evolution does not plan ahead, and major biological revolutions often come about when organs or metabolic pathways adapted to one purpose are then used for another.

See also…

Saurornitholestes sullivani: A new species of Dromaeosaurid from the Late Cretaceous of New Mexico.

The Dromaeosaurid (a type of small Theropod Dinosaur closely related to Birds and Troodontids) Saurornitholestes langstoni was first...

A new specimen of Microraptor from western Liaoning Province, China.

In December 2000 Xing Xu, Zonghe Zhou and Xioalin Wang of the Institute of Vertebrate Paleontologyand Paleoanthropology of the Chinese Academy of...

New species of Dromaeosaur from the Early Cretaceous of Utah.

Dromaeosaurs were small Therapod Dinosaurs, thought to have been the group most closely related to...

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A giant feathered dinosaur from the Early Cretaceous of Liaoning Province, China.

Recent years have seen the discovery of large numbers of feathered non-avian Theropod Dinosaurs, though most of these have been small in size. The 5 April edition of the journal Nature contains a paper by a team of scientists led by Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Key Laboratory of Evolutionary Systematics of Vertebrates at the Chinese Academy of Sciences, describing for the first time the discovery of feathers on a much larger Dinosaur.

The new Dinosaur, which has been named Yutyrannus huali ('beautiful feathered tyrant') is a Tyranosaurid from the Lower Cretaceous Yixian Formation of Liaoning Province, roughly 125 million years old, and is thought to have weighed up to 1.4 tonnes and to have reached 9 m in length; not the largest of Tyranosaurids, but much bigger than any feathered dinosaur discovered to date.

Reconstruction of Yutyrannus huali in life. The smaller dinosaurs to the left are Beipiaosaurus. Brian Choo/Chinese Academy of Sciences.

Yutyrannus huali is described from three specimens, an adult and two juveniles. Each of the specimens had feathers preserved on a different part of the body; the tail on the adult, a foot on one of the juveniles, the neck and upper fore-limb of the other. From this the researchers conclude that the living animals had feathers over much of their bodies.

The feathers were simple filaments, closer to the down of chicks than the feathers of an adult bird.

To date feathers have been found in only quite small dinosaurs and have been explained in three different ways; they could be used for flight (or at least gliding to some extent, a possibility for many small dinosaurs), they could be used as insulation, or they could be used for communication. Yutyrannus is clearly to large to have got airborne in even the most rudimentary attempt at flying. On the current data it is impossible to say if the feathers of Yutyrannus could have been used for communication. Recently there have been a number of breakthroughs in determining the colour of preserved feathers, so this is a possible avenue for future research. Larger Dinosaurs have generally been considered to have achieved thermal inertia by their size; able to maintain heat through their shear bulk (small animals have a large surface area compared to their mass, and consequently have difficulty maintaining their body temperature, for bigger animals the ratio decreases, and loosing heat can become a problem).

The temperature at Yixian is thought to have averaged 10°C over the course of the year. This is equivalent to a cool-temperate climate today, such as that of northern China, but would have been exceptionally cool for the Mesozoic, particularly as the temperature can be presumed to have fallen beneath this average for part of the year. This make the possibility that insulation was needed on Yutyrannus more than on other large Theropods. There is also the possibility that other large Theropods were also feathered, but that we have yet to discover evidence of this.

The skull (top) and part of the tail of Yutyrannus huali (bottom). Filaments are visible on the tail. Zang Hailong/Chinese Academy of Sciences.

See also The bite of T. rex, A review of Jurassic Tyrannosauriods leads to the description of a new genus, Was Archaeopteryx black? How did raptors use their claws? (and did it help them learn to fly?) and Dinosaurs on Sciency Thoughts YouTube.

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Was Archaeopteryx black?

Archaeopteryx lithographica was an early bird living in Northern Europe in the Late Jurassic, about 150 million years ago. In the mid-to-late-nineteenth century several complete and partial specimens were discovered in the Solnhofen Limestone in Bavaria, when it was hailed as both the first bird and the missing link between birds and dinosaurs. Modern scientists now regard all birds to be dinosaurs, and rivals have emerged for the title of earliest bird (though Archaeopteryx is still in the running), but Archaeopteryx still remains one of the most iconic fossils of all time, as well as shedding light on a particularly interesting area in the evolution of modern life, and as such, is still studied intently.

On 24 January 2012 a paper appeared in the journal Nature Communications detailing a new study on pigmentation in Archaeopteryx, by a team lead by Ryan Carney of the Department of Ecology and Evolutionary Biology at Brown University. Carney et al. were able to isolate melanosomes (pigment cells) from a single feather discovered in Solnhofen in 1861, the first ever fossil feather found, and the first specimen to be named Archaeopteryx. They went on to compare this to four modern melanosome types from living birds; black, grey, brown and penguin (penguin melanosomes are different from those of other birds), and came to the conclusion that they were 95% certain the feather was black.

Fit for Flight. Ryan Carney discusses the pigmentation of Archaeopteryx, by The Office of Public Affairs and University Relations at Brown University.

This has lead to widespread assertions in the press and on the internet that Archaeopteryx was black, something that Carney et al. have not actually said. The study only identifies a single feather as being (probably) black, a feather that was not actually found associated with a skeletal fossil. Since this was the original fossil assigned to the species Archaeopteryx lithographica, it could be argued on the strength of this that Archaeopteryx was black, but only by excluding all other Archaeopteryx fossils from the group. In fact there have been arguments about the classification of Archaeopteryx over the years, with some scientists having assigned all the specimens to different genera (though this was overruled by the International Commission on Zoological Nomenclature) and many scientists still assigning the different specimens to different species, so in a sense the single feather is the entire species, but this is not what is being implied.

As Carney et al. have been keen to point out, melanosomes have a structural as well as a colouring role in birds, so black feathers ten to be stronger than lighter coloured feathers. Thus flight feathers (such as the one studied) are often black on birds that are not black all over, whereas down feathers, which form an insulating layer beneath the bird's outer feathers, are usually white or light in colour.

Exactly how strong a flier Archaeopteryx was is still in dispute, but even a feather evolved for a different purpose that happened to be black would hold a slight advantage over one of another colour when getting airborne, so it is interesting, but not that surprising, to discover that the flight feathers of Archaeopteryx were black (OK finding out the colour of the feather was an amazing piece of work, but finding out that colour was black is less astounding).

Comparison with modern birds suggests the colour of the flight feathers is often independent of the colour of the rest of the bird, so even if we assume that the feather does come from the animal we think of as Archaeopteryx, we cannot assume from that that the bird was in fact black.

See also A new fossil bird from the Palaeocene of Brazil, How did raptors use their claws? (and did it help them learn to fly?), Dinosaur feathers preserved in amber, Giant bird from the Cretaceous of Kazakhstan, New 'oldest bird' found in China and Birds on Sciency Thoughts YouTube.

How did raptors use their claws? (and did it help them learn to fly?)

The Dromaeosaurs were a group of small, feathered dinosaurs closely related to the birds. They are commonly referred to as 'raptors' on account of an enlarged claw on each foot which was held clear of the ground when walking and is generally assumed to have been a weapon; this claw resembles that of a bird of prey, which are also referred to as 'raptors'. This claw was also present in the other group closely related to birds, the Troodontids, though in these it was not as prominent. The Troodontids were apparently adapted for pursuit of prey, placing additional demands upon their limbs that the Dromaeosaurs, thought to have been ambush predators, lacked. Thus the foot of a Troodontid is a compromise, that of a Dromaeosaur a more specialized tool.

A graphite drawing of Velociraptor, a typical Dromaeosaur, by artist Matt Martyniuk. (Note: this is probably a more realistic interpretation of this pheasant-sized dinosaur than the things in Jurassic Park).

The Dromaeosaurs, Troodontids and Birds together are referred to as the Paraves; all three groups show certain similarities, that were presumably present in the common ancestor, including advanced plumage, wings with flight feathers and prominent hooked claws on their feet. The presence of wings with flight feathers in Dromaeosaurs and Troodontids is interesting, as neither of these groups appears to have been able to fly, implying that these strictures predated that ability in birds. Unraveling what these structures were used for in Dromaeosaurs and Troodontids would therefore provide useful insight into the evolution of the first birds.

The use of the enlarged claw by Dromaeosaurs and Troodontids has been a subject of discussion for decades. It has been widely speculated that this was used as a slashing weapon, enabling the dinosaurs to dispatch prey with one or more lethal kicks. Another theory was that the claws were used to leap onto and even climb up much larger prey in pack attacks by the small dinosaurs.

A paper by a team lead by Denver Fowler of the Musuem of the Rockies and the Department of Earth Sciences at Montana State University, published in the journal PLoS ONE on 14 December 2011, examines the use of the raptorial claw in the small Dromeosaur Dienonychus, using modern Raptors as an ecological model.

Modern Raptors do not use their claws to slash at their prey (some do kick, but they hold their claws clear when they do so), nor do they use their claws to overcome prey larger than themselves; they do not generally attack animals larger than themselves at all. The preferred method of attack by birds of prey is to hit it very hard with either their feet (not their claws) or their beak, killing it straight away, then use the claws to carry it off. Where this is not possible they hold prey down with their claws, while they dispatch it with their beaks. This is the strategy that Fowler et al. believe was adopted by Dienonychus. When holding down struggling prey, modern Raptors use their wings to stabilize themselves, flapping vigorously to maintain their balance. Many also 'mantle' their prey, using their wings to cover it while they eat it, so that it is hidden from rivals or larger predators; some do this with still living prey, which is believed to deprive the prey of sight, making it harder to escape.

Both of these tactics would have worked perfectly well with wings that were not capable of flying, which provides a plausible explanation for the evolution of wings, flight feathers and flapping muscles in early Paravians, prior to the evolution of flight. Thus Fowler et al. believe that birds were pre-adapted to flight before they took to the air.

Illustration from Fowler et al. (2011) showing feeding in Dienonychus as they interpret it. (A) Grasping foot holds onto prey. (B) Large claws used to maintain grip on prey. (C) Predators bodyweight pins down victim. (D) Elongated tail acts as balance. (E) Rear of foot held low to help restrain victim. (F) Wings flapped to maintain stable posture. (G) Arms encircle ('mantle') prey to prevent prey seeking escape route. (H) Head reaches between feet, tearing of strips of flesh.

See also A new Troodontid Dinosaur with an injured toe, Dinosaur feathers preserved in amber, Giant Bird from the Cretaceous of Kazakhstan and Dinosaurs on Sciency Thoughts YouTube.

Dinosaur feathers preserved in amber found in eastern Alberta, Canada.

Scientists have known that some dinosaurs had feathers for a long while. Archaeopteryx, generally described as the 'first bird' was discovered in 1861, and was quickly recognized as being very similar to a small, feathery dinosaur. Since nobody (sane) thought that evolution would produce a feathery bird from a featherless dinosaur in a single generation, scientists have known that at least some dinosaurs had feathers.

In the 1990s well preserved fossils of feathered, non-avian dinosaurs in fine grained lakebed sediments began to emerge from Liaoning in China. These sediments were rich in volcanic ash, allowing for both very fine preservation and excellent dating potential. These specimens detailed a variety of small therapod dinosaurs with a variety of plumage.

Reconstruction of Dilong paradoxus, an early tyranosaurid dinosaur with primitive, hairlike feathers from the Liaoning Formation of northwest China. Illustration by artist Portia Sloan.

However these fossils, while of excellent quality, only preserve impressions of the feathers, they give no indication of their colour or three-dimensional structure. The 16 September edition of the journal Science contains a paper by a team lead by Ryan C. McKellar of the Department of Earth and Atmospheric Sciences at the University of Alberta in which they describe the discovery of a number of Cretaceous era feathers from amber (the preserved resin of coniferous trees) found in mine tailings at Grassy Lake in eastern Alberta, Canada.

A Cretaceous feather in amber from Grassy Lake, Alberta.

These specimens show a range of feathers including types known only from non-avian dinosaur fossils, preserved in three dimensions, showing their structure in spectacular detail. Unfortunately for fans of Jurassic Park, previous studies on specimens preserved in amber have ruled out the possibility of recovering DNA from specimens preserved in amber.

Forked feathers, a form unknown in true birds.

These feathers have been widely described as showing the colour of dinosaurs. They show a range of browns and yellows, colours often seen in reconstructions of feathered dinosaurs. Artists have tended to use these colours because they are common in modern feathers, and are common colours for savannah animals, and the fossils apparently confirm the theories of the artists. However amber is a yellowish-brown rock, and almost anything preserved in it will appear this colour, so little can be inferred from this.

Illustration of Limusaurus inextricabilis, a small Jurassic ceratosaur from Liaoning. Illustration again by Portia Sloan, who has coloured much of the reconstruction brown, as with D. paradoxus, above.

However another paper in the same edition of Science attempts to throw some light upon this. This details how a team lead by Roy Wongelius of the School of Earth, Atmospheric and Environmental Sciences at the University of Manchester have developed an X-ray technique to search for traces of specific metals in pigment residues, enabling them to make inferences about the original colour of the pigment (for example the presence of copper would imply a green colour). This has been used to reconstruct the coloration and patterning of (amongst other things) two Jurassic birds, the crow-like Confuciusornis sanctus and the grebe-like Gansus yumenensis.

The process of mapping a fossil (Confuciusornis sanctus) using Rapid Scanning X-ray Fluorescence.

See also Giant bird from the Cretaceous of Khazakhstan, Head-butting in a Pachycephalosaur and Dinosaurs on Sciency Thoughts YouTube.