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A Feathered Dinosaur Tail with Primitive Plumage Trapped in Mid-Cretaceous Amber Xing et al., 2016

*This image is copyright of its original author

Figure 1

Photomicrographs and SR X-Ray μCT Reconstructions of DIP-V-15103

(A) Dorsolateral overview.

(B) Ventrolateral overview with decay products (bubbles in foreground, staining to lower right).

© Caudal exposure of tail showing darker dorsal plumage (top), milky amber, and exposed carbon film around vertebrae (center).

(D–H) Reconstructions focusing on dorsolateral, detailed dorsal, ventrolateral, detailed ventral, and detailed lateral aspects of tail, respectively.

Arrowheads in (A) and (D) mark rachis of feather featured in Figure 4A. Asterisks in (A) and © indicate carbonized film (soft tissue) exposure. Arrows in (B) and (E)–(G) indicate shared landmark, plus bubbles exaggerating rachis dimensions; brackets in (G) and (H) delineate two vertebrae with clear transverse expansion and curvature of tail at articulation. Abbreviations for feather rachises: d, dorsal; dl, dorsalmost lateral; vl, ventralmost lateral; v, ventral. Scale bars, 5 mm in (A), (B), (D), and (F) and 2 mm in ©, (E), (G), and (H).

Highlights:

•  The first non-avialan theropod fragments preserved in amber are described
•  Vertebral outlines, curvature, and plumage suggest a source within Coelurosauria
•  Branching structure in the feathers supports a barbule-first evolutionary pattern
•  Iron within carbonized soft tissue suggests traces of original material are present

Summary:
"In the two decades since the discovery of feathered dinosaurs [1, 2, 3], the range of plumage known from non-avialan theropods has expanded significantly, confirming several features predicted by developmentally informed models of feather evolution [4, 5, 6, 7, 8, 9, 10]. However, three-dimensional feather morphology and evolutionary patterns remain difficult to interpret, due to compression in sedimentary rocks [9, 11]. Recent discoveries in Cretaceous amber from Canada, France, Japan, Lebanon, Myanmar, and the United States [12, 13, 14, 15, 16, 17, 18] reveal much finer levels of structural detail, but taxonomic placement is uncertain because plumage is rarely associated with identifiable skeletal material [14]. Here we describe the feathered tail of a non-avialan theropod preserved in mid-Cretaceous (∼99 Ma) amber from Kachin State, Myanmar [17], with plumage structure that directly informs the evolutionary developmental pathway of feathers. This specimen provides an opportunity to document pristine feathers in direct association with a putative juvenile coelurosaur, preserving fine morphological details, including the spatial arrangement of follicles and feathers on the body, and micrometer-scale features of the plumage. Many feathers exhibit a short, slender rachis with alternating barbs and a uniform series of contiguous barbules, supporting the developmental hypothesis that barbs already possessed barbules when they fused to form the rachis [19]. Beneath the feathers, carbonized soft tissues offer a glimpse of preservational potential and history for the inclusion; abundant Fe2+ suggests that vestiges of primary hemoglobin and ferritin remain trapped within the tail. The new finding highlights the unique preservation potential of amber for understanding the morphology and evolution of coelurosaurian integumentary structures."

Other articles related:
First Dinosaur Tail Found Preserved in Amber
Amber specimen offers rare glimpse of feathered dinosaur tail Reply