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Piotr Bajdek & Tomasz Sulej (2018)
Hypothesis: Avian flight originated in arboreal archosaurs gliding on membranous wings.
PeerJ Preprints 6:e27213v2
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The oldest feathers known to date have been found in archosaurs capable of flight. However, some of them (scansoriopterygids) flew by the use of a membrane rather than feathers. We therefore propose a new mechanism for the origin of avian flight by the use of membranous wings on both the forelimbs and the hindlimbs. It complements Beebeâs (1915) prediction of the tetrapteryx stage. Paleontological and embryological evidence suggest that feathers are a modification of reptilian scales. Scansoriopterygids were covered mostly by down-like feathers which seemingly acted as thermal isolation rather than being adapted for flight. Certain early birds, including scansoriopterygids, possessed elongate shafted tail feathers, which were probably used principally for display and resembled elongate scales. We suppose that display is the primary function of early feathers, which were preadapted for thermal isolation and also flight. The body of theropods was covered mostly by typical reptilian scales, yet some ornithischian dinosaurs possessed filamentous integumentary structures which might have had a comparable display function. However, it is doubtful that these structures in dinosaurs were homologous with avian feathers. Early birds probably shared with theropod dinosaurs an incipient endothermy, which was inherited from their common ancestor in the Triassic Period.
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John R. Bolt and R. Eric Lombard (2018)Â
Palate and braincase of Whatcheeria deltae Lombard & Bolt, 1995.
Earth and Environmental Science Transactions of The Royal Society of Edinburgh (advance online publication)
The reconstructed palate of Whatcheeria deltae indicates a skull that was unusually narrow: at least 2.2 times longer than wide if the pterygoids are conservatively placed in the horizontal plane. This maximum width is narrower than any other early tetrapod reconstructed so far. Rotating the pterygoids to produce a vaulted palate would produce an even narrower skull. Primitive palatal features include very narrow interpterygoid vacuities and a vomer, palatine, and ectopterygoid with fang-sized replacement pairs. It is derived in that there is no anterior palatal fenestra and the premaxilla has a substantial palatal shelf â a combination of characters shared only with Proterogyrinus among early tetrapods. There is a possible septomaxilla in one specimen. Whatcheeria differs from and is more derived than Pederpes, its likely sister taxon, in that only the pterygoid is covered with denticles, the vomer, palatine, and ectopterygoid containing labyrinthine teeth only. Reconstructed dental occlusion indicates that the large choana apparently accommodated the large dentary fangs; this would be a unique feature among early tetrapods. The palatal ramus of the pterygoid is longer than the quadrate ramus, which does not have a descending flange. Like Meckel's cartilage in the lower jaw, the palatoquadrate is fully ossified in larger specimens, such that in a posterior view of the skull the pterygoid is mostly hidden from sight by the epipterygoid. The ossified neurocranium consists of the basiparasphenoid and basioccipital; no ossified sphenethmoid has been found. Remains of otic capsules are partial, crushed, and smeared, so no useful morphology is available. The stapes appears to be more columnar and less plate-like than in many other primitive, early tetrapods.
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Qiang Fu, Jose Bienvenido Diez, Mike Pole, Manuel GarcÃa Ãvila, Zhong-Jian Liu Is a corresponding author , Hang Chu, Yemao Hou, Pengfei Yin, Guo-Qiang Zhang, Kaihe Du & Xin Wang (2018)
An unexpected noncarpellate epigynous flower from the Jurassic of China
eLife 2018;7:e38827Â
DOI: 10.7554/eLife.38827
The origin of angiosperms has been a long-standing botanical debate. The great diversity of angiosperms in the Early Cretaceous makes the Jurassic a promising period in which to anticipate the origins of the angiosperms. Here, based on observations of 264 specimens of 198 individual flowers preserved on 34 slabs in various states and orientations, from the South Xiangshan Formation (Early Jurassic) of China, we describe a fossil flower, Nanjinganthus dendrostyla gen. et sp. nov.. The large number of specimens and various preservations allow for an evidence-based reconstruction of the flower. From the evidence of the combination of an invaginated receptacle and ovarian roof, we infer that the seeds of Nanjinganthus were completely enclosed. Evidence of an actinomorphic flower with a dendroid style, cup-form receptacle, and angiospermy, is consistent with Nanjinganthus being a bona fide angiosperm from the Jurassic, an inference that we hope will re-invigorate research into angiosperm origins.
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David Winship Taylor & Hongqi Li (2018)ÂÂ
Paleobotany: Did flowering plants exist in the Jurassic period?
eLife 2018;7:e43421Â
DOI: 10.7554/eLife.43421
The discovery of a fossil that might be the oldest flowering plant will continue the debate on the origin and structure of ancestral flowering plants.
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