Dinosaurs did not have feathers, they had bristles. Dinosaur to bird proponents misclassify dinosaur bristles as (proto)feathers.
There is no connection between the bristles in Coelurosaur dinosaurs and the pennaceous feathers in Pennaraptora/Paraves.
There is no connection between the bristles in Coelurosaur dinosaurs and the pennaceous feathers in Pennaraptora/Paraves.
Xu and Guo
Morphotype 1 is known from the heterodontosaurid Tianyulong and the ceratopsian Psittacosaurus (Mayr et al., 2002; Zheng et al., 2009). Its main characteristic is being monofilament and relatively great length and rigidity. A variant of this morphotype is seen in Beipiaosaurus, which differs from those of Tianyulong and Psittacosaurus in its relatively great width ( Xu et al., 2009b). Morphotype 2 is a compound structure composed of multiple filaments joined basally. It is clearly present in Sinornithosaurus and Anchiornis, and probably also in Sinosauropteryx and Beipiaosaurus. Morphotype 3 is a distally branched filament, which is seen in the holotype of Sinornithosaurus millenii and probably in Beipiaosaurus (Xu et al., 1999). The main characteristic of this morphotype of feather is its barbs breaking off from the tip of a central filament and distally positioned short barbs. Morphotype 4 is a compound structure consisting of multiple filaments branching laterally from most of the length of a central filament. It is known in Sinornithosaurus, Anchiornis, Caudipteryx, Protarchaeopteryx, and probably Dilong as well (Xu et al., 2004). Morphotype 5 is only known in Epidexipteryx. It consists of parallel barbs arising from the edge of a membrane structure (Zhang et al., 2008b). Given its so unusual morphology, possibility of its being part of a more complete integumentary structure could not be completely excluded, particularly in consideration that morphotypes 2 and 4 display distally parallel barbs in some cases.
Among these defining features, tubular nature and filamentous morphology represent the earliest ones appearing in feather evolution and mark the origin of feathers as indicated by both paleontological and neontological data (Harris et al., 2002; Xu et al., 2009b). Feathers are thus here defined as integumentary structures that are tubular and filamentous in morphology. Follicle, hierarchical branches, and planar form are inferred to have evolved later in feather evolution.
Five major morphogenesis events are inferred to have occurred sequentially in feather evolution before the origin of the Aves and they are: 1) appearance of filamentous and tubular morphology, 2) formation of follicle and barb ridges, 3) appearance of rachis, 4) appearance of planar form, and 5) formation of pennaceous barbules.
A notable feature is that the filaments in feather morphotype 2 are somewhat straplike, a feature also characteristic of barbs in modern feathers, yet the filaments in feather morphotype 2 are apparently proportionally wider than barbs in modern feathers. Recent developmental studies demonstrate the impossibility of separate formation of barb and barbule cells and suggest that primitive feathers with only barbs but not barbules are unlikely to exist (Alibardi, 2005). If this holds true, some sort of simple, small barbules might be present in feather morphotype 2 or other primitive feathers.
A sudden appearance of a whole set of unique, complex developmental mechanisms and associated morphologies is also unlikely from the perspective of adaptation.
Morphotype 1 filaments are bristles. Morphotype 2 filaments are clustered bristles.
"Morphotype 2" filaments are NOT formed from a follicle. They are not "joined basally".
Bristles before down: A new perspective on the functional origin of feathers
Walter S. Persons IV, Philip J. Currie
Over the course of the last two decades, the understanding of the early evolution of feathers in nonavian dinosaurs has been revolutionized. It is now recognized that early feathers had a simple form comparable in general structure to the hairs of mammals. Insight into the prevalence of simple feathers throughout the dinosaur family tree has gradually arisen in tandem with the growing evidence for endothermic dinosaur metabolisms. This has led to the generally accepted opinion that the early feather coats of dinosaurs functioned as thermo insulation. However, thermo insulation is often erroneously stated to be a likely functional explanation for the origin of feathers. The problem with this explanation is that, like mammalian hair, simple feathers could serve as insulation only when present in sufficiently high concentrations. The theory therefore necessitates the origination of feathers en masse. We advocate for a novel origin theory of feathers as bristles. Bristles are facial feathers common among modern birds that function like mammalian tactile whiskers, and are frequently simple and hair-like in form. Bristles serve their role in low concentrations, and therefore offer a feasible first stage in feather evolution.http://www.ncbi.nlm.nih.gov/pubmed/12955841
Origin of archosaurian integumentary appendages: the bristles of the wild turkey beard express feather-type beta keratins.
Sawyer RH1, Washington LD, Salvatore BA, Glenn TC, Knapp LW.
The discovery that structurally unique "filamentous integumentary appendages" are associated with several different non-avian dinosaurs continues to stimulate the development of models to explain the evolutionary origin of feathers. Taking the phylogenetic relationships of the non-avian dinosaurs into consideration, some models propose that the "filamentous integumentary appendages" represent intermediate stages in the sequential evolution of feathers. Here we present observations on a unique integumentary structure, the bristle of the wild turkey beard, and suggest that this non-feather appendage provides another explanation for some of the "filamentous integumentary appendages." Unlike feathers, beard bristles grow continuously from finger-like outgrows of the integument lacking follicles. We find that these beard bristles, which show simple branching, are hollow, distally, and express the feather-type beta keratins. The significance of these observations to explanations for the evolution of archosaurian integumentary appendages is discussed.http://www.livescience.com/23655-fanged-dracula-dinosaur-fossils.html
Strangely, bristles somewhat like porcupine quills may have spread across most of the body of Pegomastax. Such bristles first appeared in a relative named Tianyulong recently discovered in China. Buried in lake sediments and covered by volcanic ash, Tianyulong was preserved with hundreds of bristles covering its body from its neck to the tip of its tail.http://www.livescience.com/3410-feathers-tied-origin-dinosaurs.html
The feather-like structures found on the new heterodontosaur fossil [Tianyulong] are rigid, tubular and not that downy, You writes. They somewhat resemble relatively long, stiff, quills or bristles that have been reported on psittacosaurs — only the psittacosaur's are stiffer and more widely separated.
what we see in this heterodontosaur [Tianyulong] might be a separate evolution of some sort of projecting epidermal filament.
Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids
Xing Xu1 *, Mark A. Norell2 , Xuewen Kuang3 , Xiaolin Wang1 , Qi Zhao1 & Chengkai Jia1
The filamentous integumentary structures in Jehol theropods have been interpreted as protofeathers22. The presence of the similar structures in IVPP V11579 [Dilong] provides the first direct evidence showing that tyrannosauroids possessed protofeathers. Furthermore, the filamentous protofeathers are branched as in other coelurosaurians22.See:
"Feathers, however, are hierarchically complex assemblages of numerous
evolutionary novelties—the feather follicle, tubular feather germ, feather branched structure,
interacting differentiated barbules—that have no homolog in any antecedent structures"
Initial Development of a Feather Follicle
(A) Development of the epidermal feather placode and dermal condensation. (B) Development of a short bud or feather papilla. (C) Formation of the feather follicle through the invagination of a cylinder of epidermal tissue around the base of the feather papilla. (D) Cross section of the feather follicle through the horizontal plane indicated by the dotted line in C. The invaginated tubular feather follicle is characterized by a series of tissue layers (from peripheral to central): the dermis of the follicle, the epidermis of the follicle (outer epidermal layer), the follicle cavity or lumen (the space between epidermal layers), the follicle collar (inner epidermal layer or ramogenic zone), and the dermal pulp (tissue at the center of the follicle). The tubular feather germ grows by proliferation and differentiation of keratinocytes in the follicle collar. Summarized from Lucas and Stettenheim (1972) and Prum (1999).
Developmental Model of the Origin and Diversification of Feather Follicles
An hypothesized transition series of evolutionary novelties in feather development, depicted as a series of cross sections of the follicle collar—the innermost layer of epidermal tissue in the feather follicle that generates or develops into the feather (Figure 3D) from Prum (1999). The model is based entirely on the hierarchical details of feather development, and is independent of functional or phylogenetic assumptions. Each diagram is oriented with the anterior surface of the follicle collar upward. The developmental novelties are labeled in the stages at which they originate. Stage I—Origin of the undifferentiated collar through a cylindrical epidermal invagination around the base of the feather papilla. Stage II—Origin of the differentiation of the inner layer of the collar into longitudinal barb ridges and the peripheral layer of the collar into the feather sheath. Stage III—Either of these developmental novelties could have occurred first, but both are required before Stage IV. Stage IIIa—Origin of helical displacement of barb ridges and the new barb locus. Stage IIIb—Origin of paired barbules from peripheral barb plates within the barb ridges. Stages IIIaIIIb—Origin of follicle capable of both helical displacement and barbule plate differentiation. Stage IV—Origin of differentiated distal and proximal barbules within barbule plates of barb ridges. Stage Va—Origin of lateral displacement of the new barb ridge locus. Stage Vb—Origin of the division of posterior new barb locus into a pair of laterally displaced loci, and opposing anterior and posterior helical displacement of barb ridges toward the main feather and afterfeather of the follicle. See Prum (1999) for details of additional stages in the evolution of feather diversity (Stages Vc–f).
Developmental Model of the Origin and Diversification of Feathers
A predicted transition series of feather follicles based on the hypothesized series of evolutionary novelties in feather developmental mechanisms (Figure 4) from Prum (1999). Stage I—Origin of an undifferentiated tubular collar yields the first feather, a hollow cylinder. Stage II—Origin of a collar with differentiated barb ridges results in a mature feather with a tuft of unbranched barbs and a basal calamus emerging from a superficial sheath. Stage IIIa—Origin of helical displacement of barb ridges and the new barb locus results in a pinnate feather with an indeterminate number of unbranched barbs fused to a central rachis. Stage IIIb—Origin of peripheral barbule plates within barb ridges yields a feather with numerous branched barbs attached to a basal calamus. Stages IIIaIIIb—Origin of a feather with both a rachis and barbs with barbules creates a bipinnate, open pennaceous structure. Stage IV—Origin of differentiated proximal and distal barbules creates the first closed pennaceous vane. Distal barbules grew terminally hooked pennulae to attach to the simpler, grooved proximal barbules of the adjacent barb (Figure 1B). Stage Va—Lateral displacement of the new barb locus leads to the growth of a closed pennaceous feather with an asymmetrical vane resembling modern rectrices and remiges. Stage Vb—Division and lateral displacement of the new barb loci yields opposing, anteriorly and posteriorly oriented patterns of helical displacement, producing a main feather and an afterfeather with a single calamus. The afterfeather could have evolved at any time following Stage IIIb, but likely occurred after Stage IV based on modern aftershaft morphology. See Prum (1999) for details of additional stages in the evolution of feather diversity.
By focusing on the evolution of the mechanisms of feather development, Prum (1999) proposed a detailed, testable model of the evolutionary origin of feathers that is independent of functional or phylogenetic assumptions. The model proposed a five stage transition series in the history of feather diversity as a hypothesized sequence of novelties in feather development (Figure 4). The model hypothesizes that the first feather (Stage I) originated with the first feather follicle—the cylindrical epidermal invagination around the initial feather papilla. Subsequent feather diversity evolved through a series of derived developmental novelties within the tubular intermediate epidermal layer of the follicle, called the follicle collar, which generates the tubular feather germ. After the origin of the follicle came the differentiation of the follicle collar into barb ridges that generate the barbs (Stage II). The model proposes two alternative stages next—the origin of helical growth (Stage IIIa), or the origin of barbule plate differentiation (Stage IIIb). The model cannot differentiate between the two alternative orders for these events (i.e., IIIa before IIIb, or IIIb before IIIa), but following the evolution of both of these developmental novelties came the capacity to grow both kinds of branched structure typical of modern feathers (Stage IIIab). The origin of differentiated distal and proximal barbule plates followed next (Stage IV). Finally, additional developmental mechanisms evolved and created further diversity in feather structure (Stage Va–f).Prum and Brush ignore the first two steps and label the C stage (seen above) as Stage I of their feather development stages.
When researchers claim that dinosaurs have Stage I feathers, the evidence is that they had Stage B above and not Stage C. And Stage B is just a bristle.
Note: When Prum and Brush showed that feathers did not evolve from scales, then the dinosaur to bird theorists were stuck. Pennaceous feathers did not evolve from scales nor from any dinosaur filament!
Because birds evolved from reptiles and the integument of present-day reptiles (and most extinct reptiles including most dinosaurs) is characterized by scales, early hypotheses concerning the evolution of feathers began with the assumption that feathers developed from scales, with scales elongating, then growing fringed edges and, ultimately, producing hooked and grooved barbules (Figure 6 below). The problem with that scenario is that scales are basically flat folds of the integument whereas feathers are tubular structures. A pennaceous feather becomes ‘flat’ only after emerging from a cylindrical sheath (Prum and Brush 2002). In addition, the type and distribution of protein (keratin) in feathers and scales differ (Sawyer et al. 2000). The only feature shared by feathers and scales is that they both begin development as a morphologically distinct placode – an epidermal thickening above a condensation, or congregation, of dermal cells (see Figure 8 below). Feathers, then, are not derived from scales, but, rather, are evolutionary novelties with numerous unique features, including the feather follicle, tubular feather germ (an elevated area of epidermal cells), and a complex branching structure (Prum and Brush 2002
The origin of feathers is a specific instance of the much more general question of the origin of evolutionary novelties—structures that have no clear antecedents in ancestral animals and no clear related structures (homologues) in contemporary relatives. Although evolutionary theory provides a robust explanation for the appearance of minor variations in the size and shape of creatures and their component parts, it does not yet give as much guidance for understanding the emergence of entirely new structures, including digits, limbs, eyes and feathers.Includes cladogram showing missing stages.
This suggests that large pennaceous feathers first evolved distally on the hindlimbs, as on the forelimbs and tail. This distal-first development led to a four-winged condition at the base of the Paraves. (Hu et al 2009)http://www.ivpp.ac.cn/qt/papers/201403/P020140314389417822583.pdf
The significant lengthening and thickening of the forelimbs indicates a dramatic shift
in forelimb function at the base of the Paraves, which might be related to the appearance of a degree of aerodynamic capability. This hypothesis is consistent with the presence of flight feathers with asymmetrical vanes in both basal avialans and basal deinonychosaurs6,23.
Many dinosaurian groups, such as most ornithischians, the sauropodomorphs and the basal theropods, are not included in this simplified dinosaurian cladogram. The available specimens suggest that members of these groups had scaly skin, but the possibility that they are partially covered by filamentous integumentary structures cannot be completely excluded. Preservational factors make it difficult to observe the detailed structure of the filamentous feathers in available specimens of compsognathids, tyrannosauroids, and therizinosauroids, so a ‘?’ is used to indicate uncertainty regarding the presence of morphotypes 1, 3, 4 and 5 in these groups. On the basis of the anatomical, ontogenetic, and phylogenetic distribution patterns of known feather morphotypes among non-avian dinosaurs and early birds, morphotypes 1, 2 and 7 are inferred to have been lost in feather evolution, along with their associated developmental mechanisms.
Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.http://science.sciencemag.org/content/327/5971/1369
For as long as dinosaurs have been known to exist, there has been speculation about their appearance. Fossil feathers can preserve the morphology of color-imparting melanosomes, which allow color patterns in feathered dinosaurs to be reconstructed. Here, we have mapped feather color patterns in a Late Jurassic basal paravian [Anchiornis] theropod dinosaur. Quantitative comparisons with melanosome shape and density in extant feathers indicate that the body was gray and dark and the face had rufous speckles. The crown was rufous, and the long limb feathers were white with distal black spangles. The evolution of melanin-based within-feather pigmentation patterns may coincide with that of elongate pennaceous feathers in the common ancestor of Maniraptora, before active powered flight. Feathers may thus have played a role in sexual selection or other communication.Claim of feathered dinosaurs:
Among extinct dinosaurs, feathers or feather-like integument have been discovered on dozens of genera via both direct and indirect fossil evidence. The vast majority of feather discoveries have been for coelurosaurian theropods. However, integument has also been discovered on at least three ornithischians, raising the likelihood that proto-feathers were also present in earlier dinosaurs, and perhaps even a more ancestral animal, in light of the pycnofibers of pterosaurs.https://en.wikipedia.org/wiki/Yutyrannus#Feathers
Note that the filamentous structures in some ornithischian dinosaurs (Psittacosaurus, Tianyulong and Kulindadromeus) and the pycnofibres found in some pterosaurs may or may not be homologous with the feathers of theropods.
While it has been known since 2004, upon the description of Dilong, that at least some tyrannosauroids possessed filamentous "stage 1" feathers, according to the feather typology of Richard Prum, Y. huali is currently the largest known species of dinosaur with direct evidence of feathers, forty times heavier than the previous record holder, Beipiaosaurus. The feathers were long, up to 20 centimetres (7.9 in), and filamentous. Because the quality of the preservation was low, it could not be established whether the filaments were simple or compound, broad or narrow. The feathers covered various parts of the body. With the holotype they were present on the pelvis and the foot. Specimen ZCDM V5000 had feathers on the tail pointing backwards under an angle of 30° with the tail axis. The smallest specimen showed 20 centimetre (7.9 inch)-long filaments on the neck and 16 centimetre (6.3 inch)-long feathers at the upper arm.
Xu and Guo
Feather evolution was broken down into the following stages by Xu and Guo in 2009:
- Single filament
- Multiple filaments joined at their base
- Multiple filaments joined at their base to a central filament
- Multiple filaments along the length of a central filament
- Multiple filaments arising from the edge of a membranous structure
- Pennaceous feather with vane of barbs and barbules and central rachis
- Pennaceous feather with an asymmetrical rachis
- Undifferentiated vane with central rachis
Feduccia, A.; Lingham-Soliar, T.; Hinchliffe, J. R. (2005).
"Do feathered dinosaurs exist? Testing the hypothesis on morphological and paleontological evidence". Journal of Morphology. 266 (2): 125–166
"Do feathered dinosaurs exist? Testing the hypothesis on morphological and paleontological evidence". Journal of Morphology. 266 (2): 125–166
Our findings show no evidence for the existence of protofeathers and consequently no evidence in support of the follicular theory of the morphogenesis of the feather. Rather, based on histological studies of the integument of modern reptiles, which show complex patterns of the collagen fibers of the dermis, we conclude that “protofeathers” are probably the remains of collagenous fiber “meshworks” that reinforced the dinosaur integument. These “meshworks” of the skin frequently formed aberrant patterns resembling feathers as a consequence of decomposition.
See Figure 5. (Ichthyosaur)
Note that Dilong was NOT Morphotype 4. It was NOT a "compound structure consisting of multiple filaments branching laterally from most of the length of a central filament."
Here is a list of claimed "feathered dinosaurs":
Including: Yutyrannus, Sinosauropteryx, Dilong, Kulindadromeus and Sinocalliopteryx
- Avimimus portentosus (inferred 1987: ulnar ridge)
- Sinosauropteryx prima (1996)
- Protarchaeopteryx robusta (1997)
- GMV 2124 (1997)
- Caudipteryx zoui (1998)
- Rahonavis ostromi (inferred 1998: quill knobs; possibly avialan)
- Shuvuuia deserti (1999)
- Beipiaosaurus inexpectus (1999)
- Sinornithosaurus millenii (1999)
- Caudipteryx dongi (2000)
- Caudipteryx sp. (2000)
- Microraptor zhaoianus (2000)
- Nomingia gobiensis (inferred 2000: pygostyle)
- Psittacosaurus sp.? (2002)
- Scansoriopteryx heilmanni (2002; possibly avialan)
- Yixianosaurus longimanus (2003)
- Dilong paradoxus (2004)
- Pedopenna daohugouensis (2005; possibly avialan)
- Jinfengopteryx elegans (2005)
- Juravenator starki (2006)
- Sinocalliopteryx gigas (2007)
- Velociraptor mongoliensis (inferred 2007: quill knobs)
- Epidexipteryx hui (2008; possibly avialan)
- Similicaudipteryx yixianensis (inferred 2008: pygostyle; confirmed 2010)
- Anchiornis huxleyi (2009; possibly avialan)
- Tianyulong confuciusi? (2009)
- Xiaotingia zhengi (2011; possibly avialan)
- Yutyrannus huali (2012)
- Sciurumimus albersdoerferi (2012)
- Ornithomimus edmontonicus (2012)
- Ningyuansaurus wangi (2012)
- Eosinopteryx brevipenna (2013; possibly avialan)
- Jianchangosaurus yixianensis (2013)
- Aurornis xui (2013; possibly avialan)
- Changyuraptor yangi (2014)
- Kulindadromeus zabaikalicus? (2014)
- Citipati osmolskae (inferred 2014: pygostyle)
- Conchoraptor gracilis (inferred 2014: pygostyle)
- Deinocheirus mirificus (inferred 2014: pygostyle)
- Yi qi (2015)
- Zhenyuanlong suni (2015)
- Dakotaraptor steini (inferred 2015: quill knobs)
- Apatoraptor pennatus (inferred 2016: quill knobs)
- Note that the filamentous structures in some ornithischian dinosaurs (Psittacosaurus, Tianyulong and Kulindadromeus) and the pycnofibres found in somepterosaurs may or may not be homologous with the feathers of theropods.
Most of these are paravians with feathers. The others are non-paravian dinosaurs (ie actual dinosaurs). They have bristles or the remains of collagenous fiber “meshworks”.
There are no feathered dinosaurs.
It's possible that a few ornithischians, like those in the two photos above, separately evolved some kind of bristle for their own reasons, and that these bristles have no relation to the protofeathers of early theropods. It's also possible that the bristles on the above dinosaurs are homologous with theropod proto-feathers, and that the first dinosaurs all had some kind of fuzzy/bristly growths that were then later lost in most of the sauropods/ornithischians . . . or that the fuzz was reserved for baby dinosaurs, and only later spread to adults (although that doesn't explain the lack of feathers on the in-egg sauropod embryos.)
The ramifications of the claims may best be understood in Prum and Brush’s (2003, p. 92) own words: "The heterogeneity of the feathers found on these dinosaurs is striking and provides strong direct support for the developmental theory. The most primitive feathers known—those of Sinosauropteryx—are the simplest tubular structures and are remarkably like the predicted stage 1 of the developmental model. Sinosauropteryx, Sinornithosaurus and some other non-avian theropod specimens show open tufted structures that lack a rachis and are strikingly congruent with stage 2 of the model. There are also pennaceous feathers that obviously had differentiated barbules and coherent planar vanes, as in stage 4 of the model."
Feduccia's frill argument was followed up in several other publications, in which researchers interpreted the filamentous impressions around Sinosauropteryx fossils as remains of collagen fibres rather than primitive feathers. Since the structures are clearly external to the body, these researchers have proposed that the fibres formed a frill on the back of the animal and underside of its tail, similar to some modern aquatic lizards. The absence of feathers would refute the proposal that Sinosauropteryx is the most basal known theropod genus with feathers, and also raise questions about the current theory of feather origins itself. It calls into question the idea that the first feathers evolved not for flight but for insulation, and that they made their first appearance in relatively basal dinosaur lineages that later evolved into modern birds.http://rspb.royalsocietypublishing.org/content/274/1620/1823.full
In taxa more distantly related to birds, such as Sinosauropteryx (Figure 3 below), multiple tufts projecting a few millimeters from the skin have been discovered that resemble hypothesized early stages in avian feather development. These filamentous ‘feathers’ (or ‘protofeathers’; there is some disagreement concerning whether or not these integumentary structures were true feathers, e.g., Unwin 1998, Lingham-Soliar et al. 2007) were about 20 (5-40) mm long and appear to be rather homogenous over the body rather than originating in specific tracts. To some investigators, the filaments appear to be like down feathers and were probably used for insulation. They were hollow, and appeared to have a short shaft with barbs, but no barbules. In 2009, a fossil of another feathered dinosaur, Beipiaosaurus (a coelurosaurian theropod), with even simpler feathers was reported (Xu et al. 2009; Figures 4 and 5 below). These feathers consisted of single broad (about 2 mm wide) filament, were 10 to 15 centimeters long, and only present on the head, neck and tail. In taxa more closely related to birds, such as the oviraptorid Caudipteryx and dromaeosaurid Sinornithosaurus, elongate pinnate wing and tail feathers, structurally identical to the feathers of present-day birds and comprised of a central rachis, branching barbs, and barbules, have been found. In addition, fossils of a Dromaeosaurid (Microraptor) have revealed asymmetrically veined pennaceous feathers on both the forelimbs and hindlimbs (Clarke and Middleton 2006).http://rsbl.royalsocietypublishing.org/content/11/6/20150229
Paul M. Barrett, David C. Evans, Nicolás E. Campione
INCLUDES PTEROSAUR assumptions
Spectacularly preserved non-avian dinosaurs with integumentary filaments/feathers have revolutionized dinosaur studies and fostered the suggestion that the dinosaur common ancestor possessed complex integumentary structures homologous to feathers. This hypothesis has major implications for interpreting dinosaur biology, but has not been tested rigorously. Using a comprehensive database of dinosaur skin traces, we apply maximum-likelihood methods to reconstruct the phylogenetic distribution of epidermal structures and interpret their evolutionary history. Most of these analyses find no compelling evidence for the appearance of protofeathers in the dinosaur common ancestor and scales are usually recovered as the plesiomorphic state, but results are sensitive to the outgroup condition in pterosaurs. Rare occurrences of ornithischian filamentous integument might represent independent acquisitions of novel epidermal structures that are not homologous with theropod feathers.
All taxa were scored for the presence/absence of epidermal scales, unbranched filaments (protofeathers)/quills and more complex branched filaments (including feathers).
The “more complex branched filaments” category contains taxa with compound filaments that are not feathers and compound filaments that are feathers.
From the Supplementary information:
The taxa with compound branched filaments that are not feathers are Kulindadromeus, Dilong and Ornithomimus.
The taxa with compound branched filaments that are feathers begin at Pennaraptora.
Most of our analyses provide no support for the appearance of feathers in the majority of non-avian dinosaurs, and although many meat-eating dinosaurs were feathered, the ancestor of all dinosaurs was probably scaly.
A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds
Pascal Godefroit, Andrea Cau, Hu Dong-Yu, François Escuillié, Wu Wenhao & Gareth Dyke
1,500 character study(Used in the study that includes pterosaurs)
We considered attempting to describe the feather morphotypes in Kulindadromeus using the nomenclature of Prum et al. (52, 53) or of Xu et al. (21, 22). However, except for our monofilaments (which correspond well to Type 1 in Xu et al.), we could not assign with confidence the other two feather morphotypes in Kulindadromeus to categories described by Prum et al. or Xu et al. Further, fundamental discrepancies between these two previously published nomenclature systems remain to be resolved. Thus we felt that until new fossil material and a synthesis of existing nomenclature systems are available, interpretations of direct homologies between complex feather-types in Kulindadromeus and in Prum et al. or Xu et al. would be premature.http://reptilis.net/2014/07/31/new-siberian-ornithischian-and-the-over-feathering-of-dinosaurs-again/
So I find it quite strange and disheartening that Godefroit et al.—despite being fairly objective in their supplementary material—go completely gung-ho in calling these structures feathers.
Colored porcupine bristles:
Old World porcupines (Hystricidae) have quills embedded in clusters, whereas in New World porcupines (Erethizontidae), single quills are interspersed with bristles, underfur, and hair.
The discovery in the late 1990s in China of fossils from thousands of bona fide dinosaurs covered in feathers provided the most definitive visual evidence for the dinosaur–bird link [15–17], convincing most of the remaining skeptics (Figure 2A–C). It is now widely accepted, even by ornithologists, that birds evolved from dinosaurs , with the two groups linked by hundreds of shared features of the skeleton, soft tissues, growth, reproduction, and behavior [2,3,19–22]. Most amazingly, it is now known that many non-bird dinosaurs were feathered and would have looked much more like birds than lizards or crocodiles (Figure 3).http://scienceblogs.com/tetrapodzoology/2008/10/23/epidexipteryx-at-last/