Evolution of dinosaur epidermal structures

Barrett, Paul M.; Evans, David C.; Campione, Nicolás E.

doi:10.1098/rsbl.2015.0229

Cited by 44 publications

(59 citation statements)

References 27 publications

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“…The discovery of a complex integumentary covering in the ornithischian Kulindadromeus (Godefroit et al 2014), as well as the presence of other branched integumentary structures in the heterodontosaurid Tianyulong (Zheng et al 2009), has opened a debate on whether or not all dinosaurs may have been covered, at least in part, by these kinds of structures, including members of Sauropodomorpha. In this new hypothesis, should the feather-like integument seen in some members of Ornithischia and Theropoda actually be homologous, the origin of these features may then coincide with the origin of Ornithoscelida; there would be no evidence for, or reason to assume, the presence of such features in sauropodomorphs, saurischians, or any groups more basal to them, as has been discussed in previous hypotheses, nor would they be primitive for Dinosauria as a whole (see Barrett et al 2015). …”

Section: Origins Of Feathers?mentioning

confidence: 99%

A new hypothesis of dinosaur relationships and early dinosaur evolution

Baron

Norman

Barrett

2017

Nature

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245

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Further discussion of the main phylogenetic analysesTrees were produced and analysed in TNT 1.5-beta (Goloboff et al. 2008). In total 74 taxa were scored for 457 characters. Using the new technology search function, with ratchet and drift set to their defaults (10 iterations and 10 cycles respectively) and with 100 random additional sequences, our data produced 93 MPTs of length 1734. Bremer supports were also calculated using TNT 1.5-beta.The following characters were treated as ordered: 24, 35, 39, 60, 68, 71, 117, 145, 167, 169, 174, 180, 197, 199, 206, 214, 215, 222, 251, 269, 272, 286, 289, 303, 305, 307, 313, 322, 333, 334, 338, 353, 360, 376, 378, 387, 393, 442, 446 Our characters were drawn and modified from a number of previous studies and supplemented with an additional 63 novel characters. The main sources of our characters were Gauthier (1986), Sereno (1991), Langer and Benton (2006), Yates (2007), Butler et al. (2008), , Nesbitt (2011) and Pol et al. (2011).Our investigations and analyses showed that a number of characters previously thought only to appear in theropods or sauropodomorphs (or both) can also found in a several ornithischian taxa and, conversely, a number of features traditionally associated with basal ornithischian taxa are also present in basal theropods and, in some instances, sauropodomorphs. Furthermore, many other characters that are more traditionally associated with only one or two dinosauriform groups were found to have a wider and/or more complex distribution than other studies have previously proposed, e.g. a mediolaterally oriented scar on the anterior face of the distal femur -present in Dromomeron (Nesbitt et al. 2009a), is also found in some herrerasaurids (PVSJ 373). We tried, as objectively as possible, to capture all these similarities, as well as notable differences, between the basal members of each of the major dinosaurian lineages using our newly composed set of characters.Critically, a large number of character states were found to be present in ornithischians and theropods only (see below). Additionally, a number of other character states were found that are present only in sauropodomorphs and herrerasaurids. Some previously proposed dinosaur synapomorphies were also found to be absent from a few important early dinosaur taxa. In most of these cases, our finds changed the optimisations of important characters within the tree, often leading to changes in the structure of the tree itself, as well as our interpretation of the basal dinosaur interrelationships that the distributions of these character states imply.A number of novel clades were recovered by our analysis. Of these, Ornithoscelida is the most strikingly different from previous systems of grouping and classification. A full list of synapomorphies for each of the major clades that we have recovered is given later in this Supplement (Section 3.4). A discussion of a few of the other important finds of our analysis follows here.A constraint tree was also produced in TNT 1.5-beta in order to test how man...

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Section: Origins Of Feathers?mentioning

confidence: 99%

A new hypothesis of dinosaur relationships and early dinosaur evolution

Baron

Norman

Barrett

2017

Nature

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245

313

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“…In fact, within Coelurosauria, where feathers are present, they cover virtually the entire body [13,14]. On the other hand, the co-occurrence of epidermal scales and filamentous structures has only been reported in some neornithischians [15], although the homology of these filamentous structures with theropod feathers has been questioned [7]. Finally, the presence of epidermal scales in a large adult individual does not rule out the possibility that younger individuals possessed feathers-a developmental switchover that, to our knowledge, would be unprecedented at any rate.…”

Section: Discussionmentioning

confidence: 99%

“…Within the context of integumentary evolution in dinosaurs ( [7]; figure 2), the secondary appearance of expansive rsbl.royalsocietypublishing.org Biol. Lett.…”

Section: Discussionmentioning

confidence: 99%

“…The earliest feathers were simple hollow shafts and gradual innovations, including the development of the rachis, barbs and barbules, towards the fully formed flight feather were added in maniraptoran theropods and eventually birds [3,5]. Although filamentous feathers likely represent the plesiomorphic condition for coelurosaurians [7], the majority of dinosaurian integumentary fossils-including the giant sauropodomorphs and most ornithischians-indicate scaly, reptilian-like skin [7]. Filamentous feathers have been described in two tyrannosauroids, both from the Early Cretaceous of China: Dilong paradoxus [8] and Yutyrannus huali, which, at around 9 m in length, approached the size of some Late Cretaceous tyrannosaurids.…”

Section: Introductionmentioning

confidence: 99%

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Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution

et al. 2017

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Recent evidence for feathers in theropods has led to speculations that the largest tyrannosaurids, including Tyrannosaurus rex, were extensively feathered. We describe fossil integument from Tyrannosaurus and other tyrannosaurids (Albertosaurus, Daspletosaurus, Gorgosaurus and Tarbosaurus), confirming that these large-bodied forms possessed scaly, reptilian-like skin. Body size evolution in tyrannosauroids reveals two independent occurrences of gigantism; specifically, the large sizes in Yutyrannus and tyrannosaurids were independently derived. These new findings demonstrate that extensive feather coverings observed in some early tyrannosauroids were lost by the Albian, basal to Tyrannosauridae. This loss is unrelated to palaeoclimate but possibly tied to the evolution of gigantism, although other mechanisms exist.

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“…In brief, this field has attempted to advance far beyond the scientific evidence and, despite special pleas by Norell and Xu [112], Clarke [116] and others, there is yet to be any convincing evidence for the existence of protofeathers in any known dinosaur, ornithischian [117] or saurischian [118]. Too, the evidence for the famous colored dinosaur Sinosauropteryx is deficient by any scientific yardstick [114], and reports of feather color [113, 119 -122], and even identification of protofeathers based on melanosomes has now been seriously questioned [123 -125].…”

Section: Feathers Feathers Everywherementioning

confidence: 99%

FANTASY VS REALITY: A Critique of Smith et al.'s Bird Origins

Feduccia¹

2016

TOOENIJ

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Adherents of the current orthodoxy of a derivation of birds from theropod dinosaurs, criticize the commentary by Feduccia (2013, Auk, 130) [1 -12] entitled "Bird Origins Anew" as well as numerous papers by Lingham-Soliar on theropod dermal fibers, using numerous mischaracterizations and misstatements of content, and illustrate their own misconceptions of the nature of the debate, which are here clarified. While there is general agreement with the affinity of birds and maniraptorans, the widely accepted phylogeny, advocating derived earth-bound maniraptorans giving rise to more primitive avians (i.e. Archaeopteryx), may be "topsyturvy." The current primary debate concerns whether maniraptorans are ancestral or derived within the phylogeny, and whether many maniraptorans and birds form a clade distinct from true theropods. Corollaries of the current scheme show largely terrestrial maniraptoran theropods similar to the Late Cretaceous Velociraptor giving rise to avians, and flight originating via a terrestrial (cursorial) "gravity-resisted," as opposed to an arboreal "gravity-assisted" model. The current dogma posits pennaceous flight remiges in earth-bound theropods having evolved in terrestrial theropods that never flew. As part of the orthodoxy, fully feathered maniraptorans such as the tetrapteryx gliders Microraptor and allies, are incorrectly reconstructed as terrestrial cursors, when in reality their anatomy and elongate hindlimb feathers would be a hindrance to terrestrial locomotion.The same is true of many early birds, exemplified by reconstruction of the arboreally adapted Confuciusornis as a terrestrial predator, part of the overall theropodan scheme of birds evolving from terrestrial dinosaurs, and flight from the ground up. Both sides of this contentious debate must be constantly aware that new fossil or even molecular discoveries on birds may change current conclusions.

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Evolution of dinosaur epidermal structures

Cited by 44 publications

References 27 publications

A new hypothesis of dinosaur relationships and early dinosaur evolution

A new hypothesis of dinosaur relationships and early dinosaur evolution

Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution

FANTASY VS REALITY: A Critique of Smith et al.'s Bird Origins

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