Friday, March 31, 2017

[PaleoOrnithology • 2017] Exceptional Preservation of Soft Tissue in A New Specimen of Eoconfuciusornis and Its Biological Implications


Figure 1. Photograph of Eoconfuciusornis indet. STM7-144, preserved in right lateral view; scale bar equals 20 mm
Figure 5. In vivo reconstruction of a male and female pair of Eoconfuciusornis. Artwork by Michael Rothman.


Abstract
We report on an exceptional specimen of Eoconfuciusornis preserving rare soft-tissue traces of the ovary and wing. Ovarian follicles preserve a greater hierarchy than observed in Jeholornis and enantiornithines, suggesting confuciusornithiforms evolved higher rates of yolk deposition in parallel with the neornithine lineage. The preserved soft tissues of the wing indicate the presence of a propatagium and postpatagium, whereas an alular patagium is absent. Preserved remnants of the internal support network of the propatagium bear remarkable similarity to that of living birds. Soft tissue suggests the confuciusornithiform propatagium could maintain a cambered profile and generate lift. The feathers of the wing preserve remnants of their original patterning; however, this is not strongly reflected by observable differences under scanning electron microscopy (SEM). The tail plumage lacks elongate rectrices, suggesting that the earliest known confuciusornithiforms were sexually dimorphic in their plumage.

Keywords: Huajiying, Jehol Biota, Aves, Confuciusornithiformes, propatagium, feathers


Figure 1. (a) Photograph of Eoconfuciusornis indet. STM7-144, preserved in right lateral view; scale bar equals 20 mm.
Inset SEM images (all scale bars equal 2 μm); (b) left-wing coverts (sample 2_2) preserving black eumelanosomes; (c) coronal feathers (sample 2_1) preserving grey eumelanosomes; (d) dark spot of secondaries (sample A) preserving black eumelanosomes; (e) light part of secondaries (sample C) preserving grey mouldic eumelanosomes; (f) tail feathers (sample 2_3) preserving black eumelanosomes; (g) crural feathers (sample 2_4) preserving grey eumelanosomes; (h) submalar feathers (sample G) preserving phaeomelanosomes. Yellow dots indicate location of each sample. 

 

Figure 2. (a) Interpretative drawing of Eoconfuciusornis indet. STM7-144; (b) ovarian follicles; (c) remnants of the internal structure of the propatagium with underlying feathers; (d) preserved pattern in the greater coverts; (e) secondary remiges. Scale bar equals 10 mm in (a) and 5 mm in all insets. Anatomical abbreviations: al, alular metacarpal; ca, caudal vertebrae; ce, cervical vertebrae; cm, carpometacarpus; co, coracoid; cv, wing coverts; de, dentary; dv, dorsal vertebrae; f, frontal; fe, femur; g, gastralia; gc, greater coverts; hu, humerus; il, ilium; is, ischium; l, left; lc, lesser coverts; ma, major metacarpal; mc, marginal coverts; mi, minor metacarpal; mt, metatarsal; p1-3, manual phalanges; pb, pubis; pm, premaxilla; pp, postpatagium; prp, propatagium; py, pygostyle; ra, radius; ri, ribs; s, synsacrum; sc, scapula; sl, scleral ossicles; sr, secondary remiges; st, sternum; tbt, tibiotarsus; tmt, tarsometatarsus; ul, ulna; u, uncinate process. Yellow indicates preserved remnants of maturing ovarian follicles; dermal and epidermal tissue remnants are indicated in tan; remains of collagen fibres are brown. Dark grey indicates body feathers and the dorsal layer of wing coverts; light grey indicates the greater coverts and secondaries with preserved patterning. White dashed boxes represent areas enlarged in insets. 

Figure 5. In vivo reconstruction of a male and female pair of Eoconfuciusornis.
Artwork by Michael Rothman. 

Xiaoting Zheng, Jingmai K. O’Connor, Xiaoli Wang, Yanhong Pan, Yan Wang, Min Wang and Zhonghe Zhou. 2017. Exceptional Preservation of Soft Tissue in A New Specimen of Eoconfuciusornis and Its Biological Implications. National Science Review. nwx004. DOI: 10.1093/nsr/nwx004

Scientists make new discovery about bird evolution
 Summary: A team of scientists has described the most exceptionally preserved fossil bird discovered to date, in a newly published article. The new specimen from the rich Early Cretaceous Jehol Biota (approximately 131 to 120 million years old) is referred to as Eoconfuciusornis, the oldest and most primitive member of the Confuciusornithiformes, a group of early birds characterized by the first occurrence of an avian beak.


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