Dinosaur coloration is generally one of the unknowns in the field of paleontology, as skin pigmentation is nearly always lost during the fossilization process. However, recent studies of feathered dinosaurs and skin impressions have shown the colour of some species can be inferred through the use of melanosomes, the colour-determining pigments within the feathers.
In 2010, paleontologists studied a well-preserved skeleton of Anchiornis , an averaptoran from the Tiaojishan Formation in China, and found melanosomes within its fossilized feathers. As different shaped melanosomes determine different colours, analysis of the melanosomes allowed the paleontologists to infer that Anchiornis had black, white and grey feathers all over its body and a crest of dark red or ochre feathers on its head. [1]
In 2015, another specimen was reported to possess melanosomes that induced grey and black coloration, but no red or brown coloration. This may have been because of different testing methods or a different age or species of the second tested specimen. [2]
In 2012, Ryan Carney and colleagues produced the first colour study on an Archaeopteryx specimen. Fossilized melanosomes suggested a primarily black coloration in the feathers of the specimen. The feather studied was likely a covert, which would have partly covered the primary feathers on the wings. Carney pointed out that this is consistent with the flight feathers of modern birds, in which black melanosomes have structural properties that strengthen feathers for flight. [3]
In 2013, a study published in the Journal of Analytical Atomic Spectrometry by Manning et al. reported new analyses on the feather revealing that Archaeopteryx may have had light and dark coloured plumage, with only the tips of the feathers being primarily black instead of the entire feather. Whether or not this coloration was primarily for display or flight is currently unknown. [4]
A follow-up study by Carney and colleagues in 2020 suggested that the feather was matte black, not iridescent, with 90% probability, owing to the less elongated shape of the melanosomes. However, they noted that some of the melanosomes preserved three-dimensionally in the specimen were distorted to give the impression of iridescent melanosomes. Unlike Manning and colleagues, they reconstructed the feather as being completely dark at the tip. [5]
Beipiaosaurus had a dense covering of downy-like fibers along with a secondary coat of longer, simpler feathers. In a study of the colour and shape of fossilized melanosomes in numerous extant and fossil specimens, Li et al. (2014) found that the preserved feathers in the neck area of the Beipiaosaurus specimen implied brownish and dark brownish coloration. [6]
The fossilized feathers of Caihong possessed nanostructures which were analyzed and interpreted as melanosomes. They showed similarity to organelles that produce a black iridescent colour in extant birds. Other feathers found on the head, chest, and the base of the tail preserve flattened sheets of platelet-like melanosomes very similar in shape to those which create brightly coloured iridescent hues in the feathers of modern hummingbirds. However, these structures are seemingly solid and lack air bubbles, and thus are internally more akin to the melanosomes in trumpeters than hummingbirds. Caihong represents the oldest known evidence of platelet-like melanosomes. [7]
In the 1998 description of Caudipteryx , Qiang et al. noted the existence of preserved colour bands on the fossilized tail feathers of the holotype specimen. [8] Later studies indicated that the body feathers of Caudipteryx contained eumelanin, a pigment lending dark grey/black shades. [9] [6] [10]
In 2012, Quanguo Li and colleagues analyzed BMNHC PH881, a specimen of Microraptor , and determined that the coloration of typical Microraptor feathers was iridescent black. The melanosomes were narrow and arranged in stacked layers, reminiscent of the blackbird. It was believed that Microraptor was nocturnal due to size of the scleral ring. [11] However, the iridescent nature of its feathers has cast this into doubt, since no modern birds with iridescent plumage are known to be nocturnal. [12]
In 2010, a team of researchers analyzed the holotype remains of Sinornithosaurus (IVPP V12811) and other feathered dinosaurs from the Yixian and discovered melanosomes. The presence of rod-shaped and spherical-shaped melanosomes suggested that Sinornithosaurus had black and rufous feathers. Unfortunately, the exact location of these colours on the body is unknown, so the colour pattern cannot confidently be determined. [9]
Zhang et al. (2010) discovered melanosomes in the remains of Sinosauropteryx and some other feathered dinosaurs. [9] It was determined that Sinosauropteryx had rufous/light brown feathers and that its tail was striped. Given the feathers were brightly coloured and ill-suited for flight, it was hypothesised that this species used its feathers for display. A 2017 study by Smithwick et al. also reported that the body coloration of Sinosauropteryx extended to the face, creating a raccoon-like "mask" around the eyes. They hypothesized that the countershaded pattern of Sinosauropteryx likely acted as camouflage in an open environment. [13]
In 2023, Croudace et al. described the likely plumage coloration of the Wulong holotype, a complete articulated specimen of a one-year-old individual. They proposed that the feathers on the forelimbs and hindlimbs were iridescent, with feathers on the rest of the body being grey. They suggested that, since the Wulong holotype is a juvenile, the iridescence may indicate purposes of intraspecific signalling and communication, rather than solely sexual signalling. [14]
An unnamed bohaiornithid enantiornithine specimen preserved on a slab and counterslab was described in 2016 by Peteya et al. Their analysis of the extensive covering of fossilized feathers suggested that the crown, neck, and body contour feathers were weakly iridescent. [15]
In a 2020 study, Eliason and Clarke determined that the feathers on the head, tail, and wing primaries of the Eocene lithornithid Calciavis were iridescent, likely glossy black. Additionally tested feathers from the fossilized wings were black. [16]
In their 2016 description of the Early Cretaceous ornithuran bird Changzuiornis , Huang et al. noted melanosomes indicative of black coloration in the fossilized feathers of the wings and leg/tail region. [17]
In 2010, Zhang et al. examined fossils of feathered dinosaurs with preserved melanosomes. After studying these with an electron microscope, they found eumelanosomes and pheomelanosomes preserved in a specimen of Confuciusornis , (IVPP V13171). This suggested that Confuciusornis had hues of grey, red/brown and black. This was the first time that an early bird fossil had been shown to contain preserved pheomelanosomes. [9] However, Wogelius et al. (2011) failed to find these reported traces of pheomelanosomes. They found a link between the presence of certain metals like copper, and preserved melanin. Using a combination of preserved melanosomes and metals in the feathers, they reconstructed Confuciusornis sanctus with dark-coloured body and upper wing feathers, but found no trace of either melanosomes or metals in the majority of the wing feathers. They suggested that the wings of Confuciusornis may have been white or coloured with carotenoid pigments. The long tail feathers of male specimens would have also been darker in colour. [18]
In 2018, Li et al. reported extensively preserved melanosomes and plumage patterns in the fossilized feathers of another specimen (CUGB P1401) of a species of Confuciusornis. They noted primarily dark colours with the feathers on the wings, covert feathers, crest, and throat having complex patterns of small dark spots. Comparing the preserved patterns of Confuciusornis with extant birds, they further suggested that this pattern was used as camouflage. [19]
Structures believed to be fossilized melanosomes were found in five feather samples from the only known specimen of the enantiornithean bird Cruralispennia using scanning electron microscopy. Due to their rod-like shape, they were identified as eumelanosomes, which correspond to dark shades. Although specific colours were not stated in the analysis, other studies have shown that coloration in extant birds correlates to the length and aspect ratio (length to width ratio) of their eumelanosomes. A sample taken from the crural feathers had eumelanosomes with the shortest aspect ratio, which may have corresponded to dark brown coloration. The highest aspect ratio eumelanosomes were found in a sample from the head feathers. High aspect ratios have been known to correlate with glossy or iridescent colours, although without knowing the structure of a feather's keratin layer (which does not fossilize well), no hue can be assigned for certain. The wing and tail samples also had high aspect ratios, while the tail's eumelanosomes were the largest sampled. [20] [12]
Zheng et al. determined the likely colours of a specimen of Eoconfuciusornis in 2017. They suggested that the feathers of the wing coverts, nape, and tail were black, the feathers on the leg and top of the head were grey, and the feathers on the throat were brown. The secondary remiges had a dark spotted pattern. [21]
In 2019, Babarović et al. studied a specimen of the Eocene coraciiform Eocoracias . They observed non-iridescent structural coloration on its feathers, the first time such has been found in a bird fossil. They reconstructed parts of the neck, tail and rump of Eocoracias as black, with the rest of the body plumage being blue. The wing feathers were also black and blue. [22]
In 2013, Daniel T. Ksepka et al. described a new species of the Eocene bird Eocypselus , E. rowei from the Green River Formation. The holotype specimen, preserved on a slab and counterslab, contains fossilized feather imprints. Ksepka et al. tested the feathers on the top of the head for preserved melanosomes, and noted densely-packed, rod-like eumelanosomes, which typically create iridescent black colours. [23] [10]
The melanosomes within the feathers of the Eocene penguin Inkayacu are long and narrow, similar to most birds. Their shape suggests that Inkayacu had grey and reddish-brown feathering across its body. Most modern penguins have melanosomes that are of similar length to those of Inkayacu, but are much wider. There are also a greater number of them within living penguins' cells. The shape of these melanosomes gives them a dark brown or black colour, and is the reason why modern penguins are mostly black and white. [24]
Wang et al. (2018) analyzed the elongate, closely-spaced melanosomes preserved in the feathers of a specimen of the Early Cretaceous ornithurine Iteravis to determine that they were likely black in colour. [25]
A single fossilized feather, likely belonging to Messelornis , was described in 2015 by Colleary et al. They suggested that the feather, likely coming from the wing, would probably have been iridescent in life. [26] [10]
In 2019, Musser, Ksepka & Field determined that a long feather from the tail of the Eocene bird Pellornis would have been a black-brown colour. [27]
Grey and iridescent colours were detected in a specimen of cf. Primotrogon sp., an Eocene trogon, by Nordén et al. in 2018. They note that the grey feathers could be down, which is often seen in shades of grey or white, so the colour patterns of Primotrogon cannot be confidently determined. [28]
In a 2020 study by O'Connor et al., they analyzed a wing feather of the Early Cretaceous enantiornithean Protopteryx and found evidence of eumelanosomes, suggesting that it had black, non-iridescent feathers. [29]
Nordén et al. (2018) studied two specimens of the Eocene swift Scaniacypselus szarskii . They primarily observed grey and brown colours, and noted that it likely had no iridescent feathers. [28]
In their 2021 description of the Early Cretaceous pengornithid Yuanchuavis , Wang et al. described the presence of eumelanosomes in the preserved tail feathers. The paired central rectrices are dark, while the smaller feathers are non-iridescent, likely grey. [30]
A 2017 examination of melanosomes preserved in a specimen of Borealopelta indicated that the nodosaurid had a reddish-brown coloration in life, with a counter-shaded pattern that may have been used for camouflage. This discovery may indicate that Borealopelta was under threat of predation, despite its large size, and that the armor on its back was primarily used for defensive rather than display purposes. [31]
A 2020 examination of a sample of 3D preserved fossil skin (YPMPU 016969) from the flank of a hadrosaurid revealed the presence of eumelanin in the specimen. Fabbri et al. hypothesized that this may suggest a grey colour, comparable to the skin of extant rhinoceros and elephants. This coloration may further imply that some hadrosaurs occupied similar ecological niches to large modern mammals. [32]
In 2016, examination of melanosomes preserved in the integument of a specimen of Psittacosaurus sp. indicated that the animal was countershaded, with stripes and spots on the limbs for disruptive coloration. This is similar to that of many modern species of forest-dwelling deer and antelope and may be due to a preference for a densely forested habitat with low light. The specimen also had dense clusters of pigment on its shoulders, face (possibly for display), and cloaca (which may have had an antimicrobial function). [33]
Archaeopteryx, sometimes referred to by its German name, "Urvogel" is a genus of bird-like dinosaurs. The name derives from the ancient Greek ἀρχαῖος (archaīos), meaning "ancient", and πτέρυξ (ptéryx), meaning "feather" or "wing". Between the late 19th century and the early 21st century, Archaeopteryx was generally accepted by palaeontologists and popular reference books as the oldest known bird. Older potential avialans have since been identified, including Anchiornis, Xiaotingia, and Aurornis.
Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and an example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant birds from other living groups.
Sinosauropteryx is a compsognathid dinosaur. Described in 1996, it was the first dinosaur taxon outside of Avialae to be found with evidence of feathers. It was covered with a coat of very simple filament-like feathers. Structures that indicate colouration have also been preserved in some of its feathers, which makes Sinosauropteryx the first non-avialian dinosaurs where colouration has been determined. The colouration includes a reddish and light banded tail. Some contention has arisen with an alternative interpretation of the filamentous impression as remains of collagen fibres, but this has not been widely accepted.
A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection in animal cells and tissues.
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They date from the early Cretaceous Jiufotang Formation, 125 to 120 million years ago. Three species have been named, though further study has suggested that all of them represent variation in a single species, which is properly called M. zhaoianus. Cryptovolans, initially described as another four-winged dinosaur, is usually considered to be a synonym of Microraptor.
Confuciusornis is a genus of basal crow-sized avialan from the Early Cretaceous Period of the Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago. Like modern birds, Confuciusornis had a toothless beak, but closer and later relatives of modern birds such as Hesperornis and Ichthyornis were toothed, indicating that the loss of teeth occurred convergently in Confuciusornis and living birds. It was thought to be the oldest known bird to have a beak, though this title now belongs to an earlier relative Eoconfuciusornis. It was named after the Chinese moral philosopher Confucius. Confuciusornis is one of the most abundant vertebrates found in the Yixian Formation, and several hundred complete specimens have been found.
Beipiaosaurus is a genus of therizinosauroid theropod dinosaurs that lived in China during the Early Cretaceous in the Yixian Formation. The first remains were found in 1996 and formally described in 1999. Before the discovery of Yutyrannus, Beipiaosaurus were among the heaviest dinosaurs known from direct evidence to be feathered. Beipiaosaurus is known from three reported specimens. Numerous impressions of feather structures were preserved that allowed researchers to determine the feathering color which turned out to be brownish.
A feathered dinosaur is any species of dinosaur possessing feathers. That includes all species of birds, and in recent decades evidence has accumulated that many non-avian dinosaur species also possessed feathers in some shape or form. The extent to which feathers or feather-like structures were present in dinosaurs as a whole is a subject of ongoing debate and research.
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999. The original specimen was collected from the Sihetun locality of western Liaoning. It was found in the Jianshangou beds of the Yixian Formation, dated to 124.5 million years ago. Additional specimens have been found in the younger Dawangzhangzi bed, dating to around 122 million years ago.
Anchiornis is a genus of small, four-winged paravian dinosaurs, with only one known species, the type species Anchiornis huxleyi, named for its similarity to modern birds. The Latin name Anchiornis derives from a Greek word meaning "near bird", and huxleyi refers to Thomas Henry Huxley, a contemporary of Charles Darwin.
Inkayacu is a genus of extinct penguins. It lived in what is now Peru during the Late Eocene, around 36 million years ago. A nearly complete skeleton was discovered in 2008 and includes fossilized feathers, the first known in penguins. A study of the melanosomes, pigment-containing organelles within the feathers, indicated that they were gray or reddish brown. This differs from modern penguins, which get their dark black-brown feathers from unique melanosomes that are large and ellipsoidal.
Eosinopteryx is an extinct genus of theropod dinosaurs known to the Late Jurassic epoch of China. It contains a single species, Eosinopteryx brevipenna.
Bohaiornithidae is a group of early predatory enantiornithean dinosaurs from the early Cretaceous Period of China. All known specimens come from the Jiufotang Formation and Yixian Formation, dating to the early Aptian age, 125–120 million years ago. Bohaiornithidae was first coined by Wang and colleagues in 2014. They defined it as the natural group formed by all descendants of the common ancestor of the type species, Bohaiornis guoi, and Shenqiornis mengi.
Borealopelta is a genus of nodosaurid ankylosaur from the Lower Cretaceous of what is today Alberta, Canada. It contains a single species, B. markmitchelli, named in 2017 by Caleb Brown and colleagues from a well-preserved specimen known as the Suncor nodosaur. Discovered at an oil sands mine north of Fort McMurray, Alberta, the specimen is remarkable for being among the best-preserved dinosaur fossils of its size ever found. It preserved not only the armor (osteoderms) in their life positions, but also remains of their keratin sheaths, overlying skin, and stomach contents from the animal's last meal. Melanosomes were also found that indicate the animal had a reddish pinkish skin tone.
Cruralispennia is an extinct genus of enantiornithean bird. The only known specimen of Cruralispennia was discovered in the Early Cretaceous Huajiying Formation of China and formally described in 2017. The type species of Cruralispennia is Cruralispennia multidonta. The generic name is Latin for "shin feather", while the specific name means "many-toothed". The holotype of Cruralispennia is IVPP 21711, a semi-articulated partial skeleton surrounded by the remains of carbonized feathers.
Anchiornithidae is a family of small paravian dinosaurs. Anchiornithids have been classified at varying positions in the paravian tree, with some scientists classifying them as a distinct family, a basal subfamily of Troodontidae, members of Archaeopterygidae, or an assemblage of dinosaurs that are an evolutionary grade within Avialae or Paraves.
Julia Allison Clarke is an American paleontologist and evolutionary biologist who studies the evolution of birds and the dinosaurs most closely related to living birds. She is the John A. Wilson Professor in Vertebrate Paleontology in the Jackson School of Geosciences and a Howard Hughes Medical Institute Professor at the University of Texas at Austin.
Wulong is a genus of microraptorine dromaeosaurid dinosaurs from the Early Cretaceous (Aptian) Jiufotang Formation of China. The genus includes a single species, Wulong bohaiensis. The skeletal remains, which include preserved feathers, represent a juvenile.
Eocoracias is an extinct genus of bird related to modern rollers and other Coraciiformes such as kingfishers, bee-eaters, motmots, and todies. It contains one species, Eocoracias brachyptera, and it lived approximately 47 million years ago based on dating of the fossil site. It is known for a specimen having preserved non-iridescent structural coloration on its feathers, previously unknown in fossil birds. Fossils have been found at the Messel Pit in Germany.
Yuanchuavis is an extinct genus of pengornithid bird in the group Enantiornithes. Its type and only specimen, IVPP V27883, is the holotype for its only species, Y. kompsosoura. It was recovered from the Jiufotang Formation of China, and has a fossilized fan of highly graduated rectrices. The tail has graduation similar to Chiappeavis and a pair of highly elongate central rectrices similar to the pintails of extant male sunbirds. Melanosomes sampled from the holotype suggest the central pair of rectrices to be dark in colour, and the rest of the tail feathers to be either grey or with non-iridescent structural colour.
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