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Disassociated rhamphotheca of fossil bird Confuciusornis (1 Viewer)

Fred Ruhe

Well-known member
Netherlands
Case Vincent Miller, Michael Pittman, Thomas G. Kaye, Xiaoli Wang, Jen A. Bright & Xiaoting Zheng, 2020

Disassociated rhamphotheca of fossil bird Confuciusornis informs early beak reconstruction, stress regime, and developmental patterns

Communications Biology. 3: Article number 519.
doi:10.1038/s42003-020-01252-1

Free pdf and abstract: https://www.nature.com/articles/s42003-020-01252-1.pdf

Soft tissue preservation in fossil birds provides a rare window into their anatomy, function, and development. Here, we present an exceptionally-preserved specimen of Confuciusornis which, through Laser-Stimulated Fluorescence imaging, is identified as preserving a disassociated rhamphotheca. Reconstruction of the in vivo position of the rhamphotheca validates the association of the rhamphotheca with two previous confuciusornithid specimens while calling that of a third specimen into question. The ease of dissociation is discussed and proposed with a fourth specimen alongside finite element analysis as evidence for preferential soft-food feeding. However, this proposition remains tentative until there is a better understanding of the functional role of beak attachment in living birds. Differences in postrostral extent and possibly rhamphotheca curvature between confuciusornithids and modern birds hint at developmental differences between the two. Together, this information provides a wealth of new information regarding the nature of the beak outside crown Aves.

Enjoy,

Fred
 

Fred Ruhe

Well-known member
Netherlands
Fig. 1 Comparison of confuciusornithid rhamphothecae. The skull of STM 13-162 (a) under white light and (b) under laser-stimulated fluorescence and photostacked with two images to improve clarity. The rhamphotheca is preserved as a brown stain near the premaxilla. The dorsal margins of the premaxilla and upper rhamphotheca are separated and subparallel. The upper rhamphotheca is more complete than the lower rhamphotheca and the rounding of both their tips appears to be genuine. The caudal extent of the upper rhamphotheca is obscured (see c). (c) Reconstruction of STM 13-162, with absent skeletal information (dotted lines and lower saturation) filled in from a previous reconstruction3. The pink shape is the in situ position of the rhamphotheca. The red shape is our reconstruction of the in vivo positioning of the rhamphotheca based on aligning the dorsal edge of the upper rhamphotheca with that of the premaxilla and then aligning the tips of the upper and lower rhamphothecae. We interpret the in situ upper rhamphotheca as extending just caudal to the prominent crack, to the poin of color transition in the fluorescing area (mid-naris in vivo; anterior naris in situ). (d–g) Line drawings of the rostra and rhamphothecae of (d) BMNHC-PH986 (scale approximate based on STM 13-162, reconstructed by same methods), (e) IVPP V12352 (vertically reflected), (f) IVPP V11977 (vertically reflected), and (g) IVPP V11553 (vertically reflected). All are in lateral view except for the dentary of (f) which is in in ventral view. (d) Is redrawn from6 p. 156, (e–g) are redrawn from4. d Dentary, lr lower rhamphotheca, n naris, p premaxilla, pf premaxillary foramina(vascularization), ur upper rhamphotheca.

Fred
 

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