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Schematic illustration of type I collagen fibers. The typical banding of type I collagen fibrils is readily detectable in longitu- dinal view. The five fibers depicted comprise a bundle and many such bundles may form larger fiber bundles
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The early origin of birds is a hotly disputed debate and may be broadly framed as a conflict between paleontologists and ornithologists. The paleontological emphasis has shifted from Archaeopteryx and its origins to recent finds of Cretaceous birds and "feathered" dinosaurs from China. The identification of alleged feathers has, however, relied pri...
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... The early origin of birds is a hotly disputed debate and may be broadly framed as a conflict between paleontologists and ornithologists. The paleontological emphasis has shifted from Archaeopteryx and its origins to recent finds of Cretaceous birds and “feathered” dinosaurs from China. The identification of alleged feathers has, however, relied principally on the visual image. Some workers have interpreted these integumentary structures as collagen fibers. To test the latter hypothesis, using light microscopy, collagen from the hypodermis (blubber) and subdermal connective tissue sheath was examined from a dolphin that had been buried for a year as part of an experiment. Within the blubber, toward the central thicker parts of the material, the collagen fibers had compacted and the three-dimensional latticework of normal blubber had more or less collapsed. Chromatographic analysis of the blubber revealed pronounced oxidation of the unsaturated lipids, probably accounting for the collapse of the latticework. Fibers normally bound together in bundles became separated into individual fibers or smaller bundles by degradation of the glue-like substance binding them together. These degraded collagen fibers show, in many instances, feather-like patterns, strikingly reminiscent of many of those identified as either “protofeathers” or “modern” feathers in dromaeosaurid dinosaurs. The findings throw serious doubt on the virtually complete reliance on visual image by supporters of the feathered dinosaur thesis and emphasize the need for more rigorous methods of identification using modern feathers as a frame of reference. Since collagen is the main fiber type found in most supporting tissues, the results have wide implica- tions regarding the degradation and fossilization of vertebrate integument, such as that of the ichthyosaurs, dinosaurs and birds. Declarations that any remaining doubts that birds evolved from small, feathered dromaeosaurid dinosaurs should be laid to rest are becoming commonplace. However, a pivotal question of when is a feather a feather, based on fossilized material, is moot, and answers are far from unequivocal. A notable, if controversial, view is that collagen is the biological material preserved in the integument of the famous Chinese dromaeosaurid dinosaurs (Feduccia 1999), not feathers as postulated in a number of recent high- profile articles (Prum 1999; Ji et al. 2001; Norell et al. 2002). This is a plausible interpretation given the wealth of data that has accumulated over the past 25 years on the complex architecture of collagenous fibers in the dermal and subdermal layers of the skin in a wide range of vertebrates, e.g., sharks (Motta 1977; Wainwright et al. 1978), bony fish (Hebrank and Hebrank 1986), dolphins (Pabst 1996), snakes (Jayne 1988), loggerhead turtles (personal observation), urodeles (Frolich and Schmid 1991), and anurans (Greven et al. 1995). Integumental structures in mammoths (Kukhareva and Ileragimov 1981) and ichthyosaurs (Lingham-Soliar 1999, 2001) have also been interpreted as being part of a collagenous fabric. Type I collagen fibers, the most common type in vertebrates, are normally organized in bundles of fibrils (about 80–90 nm thick), the structural unit of the fibers (Axer et al. 2001). Each fiber is usually 8–10 m m thick. However, what are usually referred to as fibers are in fact bundles or fascicles of fibers (Fig. 1) frequently several hundred microns thick (unpublished data on collagen fiber bundles in the white shark, Carcharodon carcharias ). There is, thus, considerable potential for postmortem disorganization of the fibers following degradation, which may be made permanent during fossilization. Integumentary structures in fossils are difficult to assess because of complex changes following the death of an animal, ranging from taphonomic changes resulting from microbial and chemical degradation (Allison 1988; Allison and Briggs 1991) to compaction and weathering (Koch et al. 2001). Difficulties include scanty information on postmortem organic changes (humans excluded), in particular on the degradation of integumental collagen. Fossilized soft tissue preservations are both rare and valuable (in information content) and consequently war- rant rigorous tests to enable reliable interpretations. The aim of the present investigation was to test how collagen might be preserved in fossils by burying a dolphin for a year so as to obtain data on the important stages of decomposition that immediately precede potential fossilization following the death of an animal. Light microscopy revealed that the SDS comprised collagen fiber bundles 30–40 m m in diameter in several compressed layers. Fibers were eroded, although occa- sional patches of fairly well preserved fibers, oppositely oriented in two discernible layers (Fig. 2a), were evident. In other areas of the SDS, the fibers had a clearly wavy structure that produced a downy appearance (Fig. 2b). Within the blubber, toward the central thicker parts of the section, the collagen fibers had compacted and the three- dimensional latticework, observable in fresh dolphin blubber, had more or less collapsed. Chromatographic analysis of this layer revealed pronounced oxidation of the unsaturated lipids, which probably accounts for the collapse of the latticework (only saturated fatty acids with 14, 16, and 18 carbon atoms remained) (O. Grahl-Nielsen, personal communication 2003; Fig. 3). Nearer the edges of the blubber sections (Fig. 2c–e) there was wholesale breakdown and disruption of fiber bundles of various size classes (Fig. 2f, g). The process of “peeling” apart of the collagen bundles was evident in many places (Fig. 2h). Lewis and Johnson (2001) noted that during the failure process of cartilage, peeling of collagen fibrils occurs, apparently as a consequence of the breakdown of a “glue” that is considered to hold them together. I interpret the peeling, in this case of the fibers and fiber bundles (Fig. 3h), to be caused by the degradation of a similar “glue”, presumably as a consequence of bacterial activity. The “glue” was less evident along the edges of the sections where more of the fibers had been released from their bundles. A feature widely noted in the preserved decomposing tissue concerns the bead-like structure of the collagen fibers. A similar condition was noted in fossilized integumental fibers in ichthyosaurs. Under polarized light at different azimuths, TP sections of dolphin blubber and shark skin showed peaks and troughs of the fibers, a consequence of regular, short waves (at about 50 m m inter- vals), which coincided with the observed bead-like structure (cover) and confirmed that they were not breaks in the fibers. The feature was an artifact of preparation and dehydration. All sections were air-dried to increase transparency and birefringence during transmission microscopy, which resulted in slight contraction of the fibers. Given that degrading collagen fibers demonstrate a striking resemblance to feathers, it is clearly very difficult to assign objective meaning to interpretations of dinosaur feathers, and more so to “protofeathers”, purely from visual images. This highlights the need for additional studies in which measurements are made and strict comparisons with the structure and proportions of modern feathers are presented. The new “filament-to-feather” model for feather origin (Prum 1999) has served as a challenge to the classic “scale-to-feather” model (Maderson 1972; Regal 1975; Maderson and Alibardi 2000). The new model, allegedly supported by “branched” structures, based on scanty fossil evidence, was recently shown to be highly speculative (Lingham-Soliar 2003). I demonstrate here how difficult it would be to distinguish between collagen fibers of the integument, with an almost limitless potential for pattern permutations, and the alleged external “appendages” in Sinornithosaurus millenii (Xu et al. 2001, their figure 2). In the light of the present findings, the nature of feather- like impressions in dromaeosaurs (Ji et al. 2001) is difficult to resolve, given that integumental fibers in ichthyosaurs are known to simulate similar patterns (Lingham-Soliar 2003). Nevertheless, some reports of “modern” feathers in an alleged dromaeosaur (Norell et al. 2002) are com- pelling, although not beyond dispute. However, it is important to ...
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... As highly conserved structural proteins, collagens are regarded as the essential components to blubber in cetacean skin as well [15]. In bottlenose dolphins, it has been reported that collagen fibers are present in the dermis, hypodermis (blubber), and subdermal connective tissue sheath from a decomposing individual by polarized light microscopy [16]. The collagen fiber was identified by its compacted structure and three-dimensional configuration, which show the collapse of latticework under chromatographic analysis. ...
Simple Summary
The deposition of excessive collagen resulting in scarring is a detrimental outcome of the wound healing process in humans, ultimately impeding the successful restoration of skin function. Surprisingly, in Fraser’s dolphins (Lagenodelphis hosei), collagens undergo a configuration change during wound healing and eventually recover to normal architecture. However, little research has been conducted on dolphins’ collagen composition in the skin and the underlying mechanism during the wound healing process. Here, histochemical staining and immunostaining were performed on normal and wounded skin samples in different healing stages of Fraser’s dolphins. The results demonstrate that collagens changed in composition during the wound-healing process. The mature healed wound implies the great ability to remove excessive collagen depositions in hypertrophic-like scars in Fraser’s dolphins. A better understanding of collagen dynamics in Fraser’s dolphins would provide more information and possibilities for solving aberrant scarring problems in humans.
Abstract
Fraser’s dolphins (Lagenodelphis hosei) possess great healing abilities. Their skin composition can be restored after wounding, including collagen spacing, orientation, and bundle thickness. However, it remains unclear how collagens are involved in the wound-healing process and eventually regain normality in Fraser’s dolphins. Learned from the other two scarless healing animals, changes in type III/I collagen composition are believed to modulate the wound healing process and influence the scarring or scarless fate determination in human fetal skin and spiny mouse skin. In the current study, Herovici’s, trichrome, and immunofluorescence staining were used on normal and wounded skin samples in Fraser’s dolphins. The results suggested that type I collagens were the main type of collagens in the normal skin of Fraser’s dolphins, while type III collagens were barely seen. During the wound healing process, type III collagens showed at early wound healing stages, and type I collagen increased in the mature healed wound. In an early healed wound, collagens were organized in a parallel manner, showing a transient hypertrophic-like scar, and eventually restored to normal collagen configuration and adipocyte distribution in the mature healed wound. The remarkable ability to remove excessive collagens merits further investigation to provide new insights into clinical wound management.
... traces of keratin in dinosaur feathers [3][4][5][6] and was refuted by demonstration of close association of structures and signals with limited tissue types 7,8 , as here. The preservation of melanosomes but not pycnofibres in other pterosaur specimens referred to by Unwin and Martill 2 probably reflects relatively advanced decay in those specimens and thus is not inconsistent with our interpretations. ...
... In some instances, the interpretation of integumentary structures as feathers has been questioned, and the most detailed conflicting analyses interpreted these structures as degraded dermal collagen fibres (e.g. Lingham-Soliar 2003a, b, 2012Lingham-Soliar et al. 2007) or other tissues (e.g. Lingham-Soliar 2010). ...
Research in the late 1900s has established that birds are theropod dinosaurs, with the discovery of feather preservation in non-avian theropods being the last decisive evidence for the dinosaur origin of this group. Partially due to the great interest in the origin of birds, more phylogenetic analyses of non-avian theropod dinosaurs have probably been published than any other group of fossil vertebrates. Despite a lot of uncertainty in the exact placement of many taxa and even some major clades, there is a remarkable consensus about the hierarchical position of birds (here used for the total group, Avialae) within theropod dinosaurs. Thus, birds are part of Paraves, together with such well-known theropod groups as dromaeosaurids and troodontids; Paraves are part of Maniraptora, which furthermore include Oviraptorosauria, Therizinosauria, and Alvarezsauroidea; Maniraptora belong to Maniraptoriformes, which also include Ornithomimosauria; Maniraptoriformes are a subclade of Coelurosauria, to which Tyrannosauroidea and some other basal taxa also belong; Coelurosauria are part of Tetanurae, together with Allosauroidea and Megalosauroidea; finally, Tetanurae are a subclade of Theropoda, which also include Ceratosauria and Coelophysoidea.
... Feathers may have a stem ornithodiran origin depending on the homology of integumentary fibers present in pterosaurs and bristles in ornithischians (Mayr et al., 2002;Zheng et al., 2009). Although those structures remain somewhat enigmatic, previous claims that feathers in theropod dinosaurs were the result of taphonomic processes (e.g., Lingham-Soliar, 2003a;2003b) have been largely contradicted by gross morphology, discovery in other sedimentary regimes (Zelenitsky et al., 2012), and the presence of pigment organelles (Vinther et al., 2008;Zhang et al., 2010). ...
Fossils from the Jehol Group (Early Cretaceous, Liaoning Province, China) are integral to our understanding of Paraves, the clade of dinosaurs grouping dromaeosaurids, troodontids, and avialians, including living birds. However, many taxa are represented by specimens of unclear ontogenetic age. Without a more thorough understanding of ontogeny, evolutionary relationships and significance of character states within paravian dinosaurs may be obscured and our ability to infer their biology restricted. We describe a complete specimen of a new microraptorine dromaeosaur, Wulong bohaiensis gen. et sp. nov., from the geologically young Jiufotang Formation (Aptian) that helps solve this problem. Phylogenetic analysis recovers the specimen within a monophyletic Microraptorinae. Preserved in articulation on a single slab, the type specimen is small and exhibits osteological markers of immaturity identified in other archosaurs, such as bone texture and lack of fusion. To contextualize this signal, we histologically sampled the tibia, fibula, and humerus and compared them with new samples from the closely related and osteologically mature Sinornithosaurus. Histology shows both specimens to be young and still growing at death, indicating an age for the new dinosaur of about 1 year. The holotype possesses several feather types, including filamentous feathers, pennaceous primaries, and long rectrices, establishing that their growth preceded skeletal maturity and full adult size in some dromaeosaurids. Comparison of histology in the new taxon and Sinornithosaurus indicates that macroscopic signs of maturity developed after the first year, but before cessation of growth, demonstrating that nonhistological indicators of adulthood may be misleading when applied to dromaeosaurids. Anat Rec, 2020. © 2020 American Association for Anatomy
... Collagen is of universal occurrence in animals and it has remarkable structural integrity. Decomposing collagen fiber bundles have been shown experimentally in the hypodermis of a dolphin (Tursiops) [4], (Fig. 1), in ichthyosaurs [9], and most recently in a Jurassic plesiosaur [10] and is of course the predominant structural protein in dinosaur skin. Collagen should always be considered the most likely protein when considering the identity of fibers in any vertebrate fossil preservation. ...
... ). Putative but unproven "dinosaur protofeathers" strongly resemble dermal collagen fibers[6], shown here from (a) skin of a decomposing dophin[4]. Protofeathers or collagen fibers? Decomposing collagen fiber bundles in the hypodermis of a dolphin,Tursiops. ...
Birds of Stone contains a portfolio of outstanding photographs of the spectacularly preserved Jehol bird fossils, from the Chinese Lower Cretaceous, and other pertinent vertebrate fossils of varying ages, along with comments on each fossil. The book nicely illustrates a range of species of the radiation of enantiornithines (opposite birds), the dominant Mesozoic landbirds, as well as the ornithuromorphs, the Mesozoic antecedents of the modern neornithine birds. Although the first section of the book is fairly straight forward, the second section, on bird origins and their early evolution is one-sided, presenting only the popular paleontological view and omits discussion of controversial subjects. Examples are the highly speculative presence of dinosaur protofeathers and improbable scenarios of flight origins. There are no citations of the numerous credible opposing views in the literature.
... During the Mesozoic when reptiles formed the dominant paleoecological communities they would have been highly important in terms of biomass turnover (a role filled by mammals in present ecosystems). How these animals died and the circumstances surrounding their deaths and decomposition can be helped by a better understanding of the activities that occur immediately following an animal's death and before the potential processes of fossilization (Lingham-Soliar, 2003, 2012. ...
Fresh ostrich cadavers were exposed in a natural environment (two on land and one in a shallow pool of water) to investigate decomposition and possible opisthotonus. The decomposition followed through to skeletonization of the ostrich cadavers by maggots, the primary agents of decay. During ostrich decomposition, tissue was consumed sequentially from the soft matrix tissue of muscles to fibrous and ligamentous tissue (both comprising collagen). The feathers (comprising β-keratin) were not consumed. The entire decomposition process was completed in 5 days. Towards the latter stages of the experiment, the cadavers on land showed stages of strong upward arching of the neck which fell short of the opisthotonic posture, while the cadaver in the pool showed the classic form of opisthotonus, strongly supporting the post-mortem hypothesis of the phenomena. Comparisons are made with opisthotonus in the theropod dinosaur, Sinosauropteryx.
... These dynamic functions are largely determined by structural characteristics of the dermis, which in turn are dependent on a complex meshwork of collagen and elastin fibers [24] . The mechanical properties of skin and associated fibrous tissues have been examined in an array of extant vertebrate taxa, including bony fish [21], sharks171819, reptiles [17], cetaceans [25,26], and birds [17]; however, given sparse preservation of soft-tissue structures (other than scales, hairs and feathers) our knowledge of the integumental fiber architecture in fossil vertebrates is hitherto limited to ichthyosaurs (e.g., [17,27,28]), pterosaurs (e.g., [29]) and dinosaurs (e.g., [22]). Hence, the discovery of an elaborate system of multiple-layered fiber bundles in FHSM VP-401 constitutes a significant development in so far as it represents the first unambiguous record of deeper soft-tissue structures in the skin of an extinct squamate (but see also [9]). ...
... A similar fiber arrangement has been observed in some extant sharks [35] and the Burmese python [17], in regions of the body that are likely to face considerable stress. In large aquatic vertebrates, such as ichthyo- saurs [27,28,36,37], sharks [18,19,35] and dolphins [25,26,38], straight (i.e., high tensile) fiber bundles are often organized into multiple-layered helical networks. Presumably, this arrangement minimizes creasing of the skin, thereby counteracting fluid drag by retaining a smooth body surface. ...
The physical properties of water and the environment it presents to its inhabitants provide stringent constraints and selection pressures affecting aquatic adaptation and evolution. Mosasaurs (a group of secondarily aquatic reptiles that occupied a broad array of predatory niches in the Cretaceous marine ecosystems about 98-65 million years ago) have traditionally been considered as anguilliform locomotors capable only of generating short bursts of speed during brief ambush pursuits. Here we report on an exceptionally preserved, long-snouted mosasaur (Ectenosaurus clidastoides) from the Santonian (Upper Cretaceous) part of the Smoky Hill Chalk Member of the Niobrara Formation in western Kansas, USA, that contains phosphatized remains of the integument displaying both depth and structure. The small, ovoid neck and/or anterior trunk scales exhibit a longitudinal central keel, and are obliquely arrayed into an alternating pattern where neighboring scales overlap one another. Supportive sculpturing in the form of two parallel, longitudinal ridges on the inner scale surface and a complex system of multiple, superimposed layers of straight, cross-woven helical fiber bundles in the underlying dermis, may have served to minimize surface deformation and frictional drag during locomotion. Additional parallel fiber bundles oriented at acute angles to the long axis of the animal presumably provided stiffness in the lateral plane. These features suggest that the anterior torso of Ectenosaurus was held somewhat rigid during swimming, thereby limiting propulsive movements to the posterior body and tail.
... Detailed examination shows that the filaments themselves are light and that the dark hue appears to be restricted to the material surrounding them, i.e. the matrix or binding ''glue'' (Fig. 2, insets). In the dermal tissue and cartilage (Lewis and Johnson 2001;Lingham-Soliar 2003) and in the feather rachis , the matrix has a different chemistry compared to the fibres, which suggests two possible explanations for the darker colour: (1) colour pigment from the overlying epidermis may have impregnated the matrix (Lingham-Soliar and Plodowski 2010) and (2) the matrix might carbonize differently compared to the fibres (for skin carbonate mineralization, see Manning et al. 2009). ...
Among the spectacular dinosaur fossils reported from the Jehol Group of northeastern China is the most celebrated, Sinosauropteryx, which continues to excite interest in questions concerning feather origins—most recently with alleged identifications of melanosomes and colour in its integumental structures, which proved unfounded. The crucial significance of Sinosauropteryx is undoubtedly the focus on its basal theropod status and potentially pivotal position in informing models of the early evolutionary origin of modern feathers. On the basis of new evidence in Sinosauropteryx NIGP 127587 and GMV 2124, it is shown here that the alleged protofeathers were not free filaments but part of a composite tissue. It is shown that the tail terminates in a unique, smoothly edged, spatula-shaped structure. The dinosaurs died in the vicinity of a lake. For the first time, the taphonomy of Sinosauropteryx is investigated on the basis of aboveground decomposition experiments on living animals so as to get a better understanding of conditions preceding the death of the animal, its death, decomposition and finally preservation of soft tissue as manifested in the fossil. The signs point strongly to invertebrate colonization of the carcass of Sinosauropteryx rather than vertebrate predation or scavenging, with moderate decay associated with the purge fluids while major decay was forestalled by burial, at most a few days after death. Lastly, a theory that the opisthotonic posture of fossils such as Sinosauropteryx NIGP 127587 occurred perimortem as a consequence of neural spasms provides the basis for a forensic reconstruction of the stages leading to the dinosaur’s death and the final preserved position of the external, dorsally preserved soft tissue, which proves to be more consistent with a uniform crest than individual, free protofeathers.
... Testing the hypothesis of fossilised melanosomes in Sinosauropteryx (Material and Methods, see ESM). Zhang et al. (2010Zhang et al. ( , p. 1077) state, ''occurrence of melanosomes embedded inside the filaments of Jehol nonavian dinosaurs thus confirms that these structures are unequivocally epidermal structures, not the degraded remains of dermal collagen fibres, as has been argued recently [Lingham-Soliar 2003;Feduccia et al. 2005;Lingham-Soliar et al. 2007].'' Central to their hypothesis of melanosomes in the non-avian dinosaurs and birds they examined, they state that it is essential to distinguish between melanosomes and bacteria, given that they ''are generally similar in size (one micrometre or less) and shape (spherical, oblate or elongate).'' ...
... Fundamentally, Zhang et al. (2010) fail to consider one of the most important phenomena with respect to the fossilisation of soft tissue-decay and degradation (the byproducts or consequences of, not just the agents i.e., microbes), a failing that is likewise reminiscent of other interpretations of protofeathers (discussed in Lingham-Soliar 2003). Figure 2 clearly shows ongoing degradation, i.e. larger structures being broken down further into smaller and smaller particles (the smallest the diameter of a collagen fibril D-band), besides numerous particles of indefinable random shapes. ...
... Rather than simply speculate, an understanding of some of the stages of collagen decay is considered vital. In decomposing Caretta caretta tissue (ESM Material and Methods) fibril bundles start to break up into globular units of approximately 200-1,000 nm (Fig. 4, arrowheads) and with further decay even the D-bands of fibrils (Lingham-Soliar 2003, 2008 break-up into ''beads,'' as in a broken rosary, of *64 nm diameter (identified by x-ray diffraction; Lingham-Soliar and Glab 2010, figure 4). In addition to the larger particles, numerous globular structures, identified here, of *66 nm in diameter in Zhang et al.'s (2010) Sinosauropteryx (Fig. 2, arrows and elsewhere in the figure) emphasise the state of decay represented by the section. ...
A recent development in the identification of feathers in fossils by means of melanosomes was used to suggest that structures
observed in an SEM of a filament in the basal theropod dinosaur, Sinosauropteryx, were phaeomelanosomes and that they represented conclusive evidence that the filaments were early feathers. At the most
basic level, the claims of phaeomelanosomes are shown here to be founded on an optical illusion created when the SEM is reproduced
at low image size—viewed at larger image size (~2× original) the structures are nondescript in both size and shape and impossible
to equate with phaeomelanosomes. At a higher level of investigation, the study is seriously questioned for ignoring standard
scientific protocol: despite size and shape being critical to the identification of the phaeomelanosomes, no statistically
viable measurements of the structures (particles) were made—the measurements, which are simply conjectured, are shown here
to be incorrect in the speculated sizes, and in shapes; inferences made on vital characters from birds and advanced non-avian
dinosaurs, e.g. with respect to colour banding, are without confirmation in the test animal but conjectured on circular argumentation;
alternative arguments, e.g. that the particles might be bacteria or colour from the overlying skin, are peremptorily dismissed
or not considered; suggestions that the particles are embedded within the filament are without support since there is no evidence
of cross-sections or tangential sections either made or occurring serendipitously—only a single section is reported, apparently
of the filament’s surface. False dichotomies such as, if the structures are not bacteria they must be melanosomes, are questioned
given that one of the most important factors in the taphonomy of ancient (structures in question, ~130 MYR) fossilised filaments
i.e., decomposition—that the structures might reasonably represent the degraded remains of the filaments—is not even considered.
Here, from experiments on the decomposition of native collagen in fish and reptilian dermis, SEMs of their ultrastructure
show that distinctive spherical, elliptical or oblate particles, even more so than those figured in Sinosauropteryx, typically form during degradation. This is confirmed in SEMs of degraded collagen fibres in a 225-MYR ichthyosaur fossil,
virtually point by point. In addition numerous small bead-like structures in the filament of Sinosauropteryx bear a striking resemblance to the unique 67-nm D-bands of collagen, in both shape and size. This paper does not question the value of scientifically meritorious identifications
of melanosomes, as indeed of collagen and keratin, in interpreting the integumental structures of fossil animals. However,
allegations of phaeomelanosomes in Sinosauropteryx are shown to be without scientific merit.
Eine kürzlich entwickelte Methode zur Bestimmung von Federn in Fossilien mit Hilfe von Melanosomen wurde zur Behauptung herangezogen,
dass Strukturen, die in einer REM-Aufnahme eines Filaments von einem basal stehenden, theropoden Dinosauriers, Sinosauropteryx,
Phaeomelanosomen seien und sie den endgültigen Beweis erbrächten, dass diese Filamente frühe Federn darstellten. Auf einfachstem
Niveau zeigen wir hier, dass der angebliche Nachweis von Phaeomelanosomen auf einer optischen Täuschung beruht, die entsteht,
wenn eine REM-Aufnahme bei geringer Auflösung kopiert wird – betrachtet man die Strukturen vergrößert (~2x Originalgröße)
sind die Strukturen sowohl in Größe, als auch in Form undefinierbar und unmöglich mit Phaeomelanosomen in Deckung zu bringen.
Auch auf höherer Ebene betrachtet, stellen wir die Studie ernsthaft in Frage, weil sie wissenschaftliches Standardprotokoll
ignoriert: Obwohl für die Bestimmung der Phaeomelanosomen Größe und Form unbedingt notwendig sind, wurden von den Strukturen
(Partikeln) keine statistisch verwendbaren Messungen durchgeführt, und wir zeigen hier, dass die Messungen, die schlichtweg
gemutmaßt sind, weder in der Größe noch in der Form korrekt sind; Rückschlüsse, die aus Lebendmerkmalen rezenter Vögel und
höher entwickelter, nicht-aviärer Dinosaurier z.B. bezüglich von Farbbänderungen gezogen werden, sind am Testorganismus nicht
bestätigt, sondern spekulativ auf einem Zirkelschluss beruhend; Alternativbehauptungen, dass die Partikel beispielsweise Bakterien
oder Farbe der darüber liegenden Haut sein könnten, sind mutwillig weggelassen oder nicht in Erwägung gezogen; der Vorschlag,
dass die Partikel in das Filament eingebettet sind, bleibt ohne Untermauerung, da es keinerlei Hinweise auf durchgeführte
oder zufällige Quer- oder Tangentialschnitte gibt – lediglich eine einzige Sektion wird vorgestellt, offensichtlich von der
Oberfläche des Filaments. Wir stellen die fälschlicherweise dichotom geführte Argumentationen, wie etwa, wenn die Strukturen
keine Bakterien sind, müssen es Melanosomen sein, deshalb in Frage, weil einer der wichtigsten Faktoren in der Taphonomie
urzeitlicher (besagte Strukturen, ~130 Millionen Jahre), fossilisierter Filamente, d.h. die Degradation – dass die Strukturen
begründbar die degradierten Überreste von Filamenten darstellen könnten – nicht einmal in Erwägung gezogen wird. Aus Degradierungs-Experimenten
von natürlichem Kollagen in Fisch- und Reptilienhaut zeigen hier REM-Aufnahmen von deren Ultrastruktur, dass charakteristische
sphärische, elliptische oder abgeflachte Partikel, sogar noch deutlicher als die bei Sinosauropteryx festgestellten, typischerweise
während der Degradation entstehen. Dies wird noch quasi Punkt für Punkt durch REM-Aufnahmen von degradierten Kollagen-Fasern
eines 225 Millionen Jahre alten Ichthyosaurier Fossils bestätigt. Zusätzlich zeigen zahlreiche perlenartige Strukturen im
Filament von Sinosauropteryx in Form wie in Größe eine hochgradige Ähnlichkeit zu 67nm D-Einzelbändern von Kollagen. Diese
Publikation stellt nicht den Wert wissenschaftlich fundierter Nachweise von Melanosomen, oder die von Kollagen und Keratin
für die Interpretation von Integumentstrukturen fossiler Tiere in Frage. Behauptungen zu Existenz von Phaeomelanosomen bei
Sinosauropteryx erscheinen allerdings wissenschaftlich wertlos.
Keywords
Sinosauropteryx feathers–Phaeomelanosomes–Collagen–Globular biodegradation–
D-band fragmentation
... Apart from the developmental studies, a support of such strong views was looked for in discoveries of 'feathered dinosaurs' in the Early Cretaceous Jehol fauna in China (Zhang et al. 2006). However, some scepticism surrounds these findings, both regarding whether they are keratinous or collagenous structures (e.g. Lingham-Soliar 2003; Lingham-Soliar et al. 2007) and whether the Chinese truly feathered 'dinosaurs' are actually not secondarily flightless birds (Feduccia et al. 2007). To test all those contradictory theories, a fossil material preceding stratigraphically the oldest unquestionable bird Anchiornis from the Late Jurassic (Oxfordian?) of China (Hu et al. 2009) is desirable. ...
Organic tissue of a recently found second specimen of feather-like Praeornis from the Karabastau Formation of the Great Karatau Range in southern Kazakstan, has a stable carbon isotope composition indicative of its animal affinity. Three-dimensional preservation of its robust carbonised shaft indicates original high contents of sclerotic organic matter, which makes the originally proposed interpretation of Praeornis as a keratinous integumental structure likely. The new specimen is similar to the holotype of Praeornis in the presence of three 'vanes' on a massive shaft not decreasing in width up to near its tip. Unlike it, the vanes are not subdivided into barbs and the pennate structure is expressed only in the distribution of organic-matter-rich rays. Similar continuous blades border the 'barbs' in the holotype, but the organic matter was removed from them by weathering. It is proposed that the three-vaned structure is a remnant of the ancestral location of scales along the dorsum and their original function in sexual display, similar to that proposed for the Late Triassic probable megalancosaurid Longisquama. Perhaps subsequent rotation around the shaft, in the course of evolution from an ancestral status similar to Praeornis towards the present aerodynamic and protective function of feathers, resulted in the tubular appearance of their buds.
