[Mammalogy • 2020] The Evolution of Flight in Bats: A Novel Hypothesis

Summary of the interdigital webbing hypothesis, showing the proposed evolutionary trajectories of the Yangochiroptera, Rhinolophoidea and Megachiroptera. 

in Anderson & Ruxton, 2020.

 DOI: 10.1111/mam.12211

Abstract

Bats (order Chiroptera) are the only mammals capable of powered flight, and this may be an important factor behind their rapid diversification into the over 1400 species that exist today – around a quarter of all mammalian species. Though flight in bats has been extensively studied, the evolutionary history of the ability to fly in the chiropterans remains unclear.

We provide an updated synthesis of current understanding of the mechanics of flight in bats (from skeleton to metabolism), its relation to echolocation, and where previously articulated evolutionary hypotheses for the development of flight in bats stand following recent empirical advances. We consider the gliding model, and the echolocation‐first, flight‐first, tandem development, and diurnal frugivore hypotheses. In the light of the recently published description of the web‐winged dinosaur Ambopteryx longibrachium, we draw together all the current evidence into a novel hypothesis.

We present the interdigital webbing hypothesis: the ancestral bat exhibited interdigital webbing prior to powered flight ability, and the Yangochiroptera, Pteropodidae, and Rhinolophoidea evolved into their current forms along parallel trajectories from this common ancestor. Thus, we suggest that powered flight may have evolved multiple times within the Chiroptera and that similarity in wing morphology in different lineages is driven by convergence from a common ancestor with interdigital webbing.

Keywords: bats, Chiroptera, echolocation, evolution of flight, interdigital webbing, pterosaurs, Scansoriopterygidae

Fig. 1:  Phylogenetic groupings of chiropterans, showing the relevant subdivisions of the Chiroptera into the Megachiroptera/Microchiroptera and the Yinpterochiroptera/Yangochiroptera.

Fig. 2: Summary of the interdigital webbing hypothesis, showing the proposed evolutionary trajectories of the Yangochiroptera, Rhinolophoidea and Megachiroptera.

CONCLUSION: 

The ability of some vertebrates to take flight has been studied in a range of scientific disciplines, and yet the evolutionary journey of chiropterans from small arboreal mammals to the adept flyers we know today has never been laid out definitively. The story is inherently more complex than that of other vertebrate flyers such as birds, thanks to the close coupling of flight and echolocation in many bat species, and the evolution of flight in bats cannot be uncovered without taking this into account. With advances in molecular analyses, the phylogenetic tree of chiropterans is becoming clearer; the Rhinolophoidea is emerging as unique, not only in morphology and behaviour, but also in phylogeny.

Many hypotheses for the evolution of flight in bats remain viable, but we present a novel hypothesis which synthesises current understanding of chiropteran flight, phylogeny and evolution: that the ancestral bat exhibited interdigital webbing, and that the Yangochiroptera, Pteropodidae, and Rhinolophoidea evolved into their current forms along parallel trajectories from this common ancestor. Drawing on comparisons from the vertebrates, and in the light of the recently published description of the membrane‐winged dinosaur Ambopteryx longibrachium, this interdigital webbing hypothesis provides a biologically satisfying narrative for the evolution of flight in bats, from arboreal mammals to the fastest‐flying vertebrates that we know of. In comparison with some previous hypotheses, this novel hypothesis may be less parsimonious, but we feel it offers the best fit to currently available empirical evidence. Further evidence could strengthen support for this hypothesis, or falsify it.

 

Sophia C. Anderson and Graeme D. Ruxton. 2020. The Evolution of Flight in Bats: A Novel Hypothesis. Mammal Review. DOI: 10.1111/mam.12211

[Paleontology • 2019] Ambopteryx longibrachium • A New Jurassic Scansoriopterygid and the Loss of Membranous Wings in Theropod Dinosaurs

 Ambopteryx longibrachium 

Wang, O’Connor, Xu & Zhou, 2019

DOI: 10.1038/s41586-019-1137-z 

Illustration: Chung-Tat Cheung 

Abstract

Powered flight evolved independently in vertebrates in the pterosaurs, birds and bats, each of which has a different configuration of the bony elements and epidermal structures that form the wings. Whereas the early fossil records of pterosaurs and bats are sparse, mounting evidence (primarily from China) of feathered non-avian dinosaurs and stemward avians that derive primarily from the Middle–Upper Jurassic and Lower Cretaceous periods has enabled the slow piecing together of the origins of avian flight. These fossils demonstrate that, close to the origin of flight, dinosaurs closely related to birds were experimenting with a diversity of wing structures. One of the most surprising of these is that of the scansoriopterygid (Theropoda, Maniraptora) Yi qi, which has membranous wings—a flight apparatus that was previously unknown among theropods but that is used by both the pterosaur and bat lineages. This observation was not universally accepted. Here we describe a newly identified scansoriopterygid—which we name Ambopteryx longibrachium, gen. et sp. nov.—from the Upper Jurassic period. This specimen provides support for the widespread existence of membranous wings and the styliform element in the Scansoriopterygidae, as well as evidence for the diet of this enigmatic theropod clade. Our analyses show that marked changes in wing architecture evolved near the split between the Scansoriopterygidae and the avian lineage, as the two clades travelled along very different paths to becoming volant. The membranous wings supported by elongate forelimbs that are present in scansoriopterygids probably represent a short-lived experimentation with volant behaviour, and feathered wings were ultimately favoured during the later evolution of Paraves.

Holotype of Ambopteryx longibrachium, IVPP V24192.

Theropoda Marsh, 1881 

Maniraptora Gauthier, 1986 

Scansoriopterygidae Czerkas and Yuan, 2002 

Ambopteryx longibrachium gen. et sp. nov.

Etymology. ‘Ambo’, both (Latin); ‘pteryx’, wing (Latin), referring to the pterosaur-like wing that is present in this non-avian dinosaur; ‘longibrachium’ refers to the elongate forelimb (brachium, upper arm (Latin)).

Fig. 3: Phylogeny and phylomorphospace of Mesozoic coelurosaurians.

Min Wang, Jingmai K. O’Connor, Xing Xu and Zhonghe Zhou. 2019. A New Jurassic Scansoriopterygid and the Loss of Membranous Wings in Theropod Dinosaurs.  Nature. 569; 256–259. DOI: 10.1038/s41586-019-1137-z

Newly Discovered Bat-Like Dinosaur Reveals the Intricacies of Prehistoric Flight  po.st/FwnL8Q via @SmithsonianMag

New species of bat-wing dinosaur discovered  on.natgeo.com/2VQ07Dq via @NatGeoScience

  

  

A clash of wings  ||  Nature. 569(7755) [9 May 2019]
The cover image shows an artist’s impression of the newly identified dinosaur Ambopteryx longibrachium. Described in this issue by Min Wang and his colleagues, the fossilized remains of Ambopteryx date to the Upper Jurassic period some 163 million years ago. Ambopteryx is a scansoriopterygid, a group of dinosaurs that are generally reconstructed as small, feathered arboreal climbers, with very long hands and fingers. But Ambopteryx is different — it is the second scansoriopterygid to be found with evidence for both feathers and bat-like membranous wings supported by an accessory bone called the styliform element. The first such specimen, Yi qi, was identified in 2015 and sparked a degree of controversy for its membranous wings. The discovery of Ambopteryx shows that Yi was not alone and raises the possibility that scansoriopterygids in general may have had bat-like wings in addition to feathers. show less

Cover image: Chung-Tat Cheung.
nature.com/nature/volumes/569/issues/7755

[Paleontology • 2015] Yi qi • A Bizarre Jurassic Maniraptoran Theropod with preserved Evidence of Membranous Wings

Yi qi | ‘ee chee’
Xu, Zheng, Sullivan, Wang, Xing, Wang, Zhang, O’Connor, Zhang & Pan, 2015

doi: 10.1038/nature14423

A farmer first spotted the dinosaur fossil in the Tiaojishan Formation of Hebei Province, China, dating to the Middle–Upper Jurassic period, or about 160 million years ago. The dinosaur is a member of a group of theropods (mostly carnivorous dinosaurs) called Scansoriopterygidae.

photo: Zang Hailong

The wings of birds and their closest theropod relatives share a uniform fundamental architecture, with pinnate flight feathers as the key component. Here we report a new scansoriopterygid theropod, Yi qi gen. et sp. nov., based on a new specimen from the Middle–Upper Jurassic period Tiaojishan Formation of Hebei Province, China. Yi is nested phylogenetically among winged theropods but has large stiff filamentous feathers of an unusual type on both the forelimb and hindlimb. However, the filamentous feathers of Yi resemble pinnate feathers in bearing morphologically diverse melanosomes. Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods, suggesting the intriguing possibility that Yi had membranous aerodynamic surfaces totally different from the archetypal feathered wings of birds and their closest relatives. Documentation of the unique forelimbs of Yi greatly increases the morphological disparity known to exist among dinosaurs, and highlights the extraordinary breadth and richness of the evolutionary experimentation that took place close to the origin of birds.

The dinosaur would have sported a robust skull with a short snout

photo: Zang Hailong

Figure 1: Yi qi holotype (STM 31-2).
a, b, Photograph (a) and line drawing (b) of specimen; c, skull and mandible in lateral view; d, premaxillary tooth in lateral view; e, left manus; f, styliform elements (the distally unexposed left styliform element articulates with the wrist, and the orientation of the right styliform element implies a similar relationship to the carpus even though its proximal part is missing). Light and dark grey shading indicates feathers and membranous tissues, respectively. an, angular; cv, cervical vertebrae; d, dentary; dr, dorsal ribs; emf, external mandibular fenestra; en, external naris; f, frontal; lf, left femur; lh, left humerus; lmd2–4, left manual digits 2–„4; lmt, left metatarsals; lr, left radius; ls, left scapula; lse, left styliform element; lu, left ulna; mb, mandible; mcII–IV, metacarpals II–IV; n, nasal; or, orbit; p, parietal; phII1 to IV4, phalanges II‐1 to IV‐4; pma, premaxilla; rmd2–4, right manual digits 2–„4; rf, right femur; rfi, right fibula; rh, right humerus; rmc, right metacarpals; rmt, right metatarsals; rr, right radius; rse, right styliform element; rt, right tibiotarsus; ru, right ulna; sk, skull. Scale bar, 2 cm.

doi: 10.1038/nature14423

Figure 3: Simplified coelurosaurian phylogeny showing the recovered position of Yi.
The skeletal silhouette and two possible alternative planform reconstructions of Yi highlight the proportionally long and robust forelimbs and large leg feathers that Yi shares with other basal paravian theropods, indicating the presence of aerial capability, and the inferred membranous wings, a feature unique among known paravians but seen in most other gliding or flying tetrapods. Various uncertainties, such as how the styliform element is oriented and whether membranous tissue is present lateral to the trunk as in most volant tetrapods, imply that a variety of reconstructions of the aerodynamic apparatus of Yi are currently plausible (see Supplementary Information for additional possible reconstructions).

doi: 10.1038/nature14423

Theropoda Marsh, 1881

Maniraptora Gauthier, 1986

Scansoriopterygidae Czerkas et Yuan, 2002

Yi qi gen. et sp. nov.

Etymology. The generic and specific names are derived from Mandarin Yi (wing) and qi (strange), respectively, referring to the bizarre wings of this animal. The intended pronunciation of the name is roughly “ee chee”.

Holotype. STM 31-2 (housed at the Shandong Tianyu Museum of Nature), an articulated partial skeleton with associated soft tissue preserved on a slab and counter slab. The specimen was collected by a local farmer, but its provenance and authenticity have been confirmed by multiple lines of evidence including sedimentology, taphonomy and computed tomography (CT) data.

Locality and horizon. Mutoudeng, Qinglong County, Hebei Province, China. Tiaojishan Formation, Callovian–Oxfordian stage. On the basis of the provenance of the specimen, Yi qi is a member of the Daohugou (or Yanliao) Biota.

Preserved features of the "winged" dinosaur fossil reveal feathers over the neck (not shown), along the humerus (b) and along the humerus and ulna (c). The fossil also showed soft tissue and feathers along the right forelimb and hindlimb.

photo: Zang Hailong | doi: 10.1038/nature14423

Xing Xu, Xiaoting Zheng, Corwin Sullivan, Xiaoli Wang, Lida Xing, Yan Wang, Xiaomei Zhang, Jingmai K. O’Connor, Fucheng Zhang and Yanhong Pan. 2015. A Bizarre Jurassic Maniraptoran Theropod with preserved Evidence of Membranous Wings.

Nature. doi: 10.1038/nature14423

In Photos: Bizarre 'Bat Dinosaur' Discovered in China https://shar.es/1pAfJo  @LiveScience

Chinese Dinosaur Had Bat-Like Wings and Feathers http://on.natgeo.com/1JC8rKd via @ngphenomena

Is it a bird? Is it a bat? Meet Yi qi, the dinosaur that is sort of both http://gu.com/p/48x46/stw
Yi qi by Sheather888 http://sheather888.deviantart.com/art/Yi-qi-529971619

[Paleontology • 2014] Reinterpretation of the Early Cretaceous maniraptoran Zhongornis haoae (Dinosauria: Theropoda) as a scansoriopterygid-like non-avian, and morphological resemblances between scansoriopterygids and basal oviraptorosaurs

Fig. 1 Photograph of the holotype of Zhongornis haoae DNHM D2456

Scale bar equals 2 cm

Abstract 

The recently described maniraptoran theropod Zhongornis haoae, known from a single juvenile specimen, was originally identified as a bird. However, morphological re-evaluation reveals striking resemblances to both Oviraptorosauria and Scansoriopterygidae. The reduced, but still long, boney tail is reinterpreted as having approximately twenty vertebrae and is reminiscent of the tails of Caudipteryx and Epidexipteryx in its proportions and morphology. Other morphological similarities with basal oviraptorosaurs include a short and deep skull, and a reduced minor digit. Zhongornis also differs strikingly from other Mesozoic birds, and resembles scansoriopterygids, in the size of the alular metacarpal, the proportions of the manual digits, and the lack of processes on the ischium. These similarities, together with resemblances between basal oviraptorosaurs and previously described scansoriopterygids, may point to a close relationship between these two clades. Cladistic analysis confirms a close relationship between Zhongornis and Scansoriopterygidae, which share forelimbs and pedal unguals that are elongate compared to those of oviraptorosaurs, but does not support oviraptorosaur affinities for this clade. Additional specimens will be required in order to determine both the taxonomic placement of this species and the affinities of Scansoriopterygidae, highlighting the drawbacks of basing new species on juvenile material. 

Key words: Cretaceous, Theropoda, Scansoriopterygidae, Oviraptorosauria, Aves, Zhongornis, tail

Holotype of Zhongornis haoae (D2455 . 6).
Photographs of the slab (left; D2456) and counterslab (right; D2455) under normal light. Interpretive drawing of slab (some portions added from information contained in counterslab) with close-ups of the manus, foot and caudal vertebrae. Abbreviations: co, coracoid; cv, caudal vertebrae (c1–c13); cve, cervical vertebrae; dc, distal carpal; dpc, deltopectoral crest; dv, dorsal vertebrae; gas, gastralia; f, frontal; fei, feather impressions; fem, femur; fib, fibula; fur, furcula; hum, humerus; isc, ischium; j, jugal; mcI–III, metacarpals I–III; mtI–IV, metatarsals I–IV; pmx, premaxilla; q, quadrate; rad, radius; rib, thoracic ribs; sc, scapula; syn, synsacrum; tib, tibia; uln, ulna; I–IV, digits (manual or pedal) I–IV.

illustration: whenpigsfly-returns.blogspot.com

  Zhongornis haoae illustration: Kahless28 on @deviantART 

Jingmai K. O’CONNOR and Corwin SULLIVAN. 2014. Reinterpretation of the Early Cretaceous maniraptoran (Dinosauria: Theropoda) Zhongornis haoae as a scansoriopterygid-like non-avian, and morphological resemblances between scansoriopterygids and basal oviraptorosaurs. VERTEBRATA PALASIATICA. 52; 3-30. 

http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201401/P020140121386966325113.pdf

Gao, Cunling, Chiappe, L.M., Meng, Q., O'connor, J.K., Wang, X., Cheng, X., Liu, J. 2008.A New Basal Lineage Of Early Cretaceous Birds From China And Its Implications On The Evolution Of The Avian Tail. Palaeontology. 51(4); 775-791. doi: dx.doi.org/10.1111/j.1475-4983.2008.00793.x

http://dinosauria.ucoz.com/news/2008-07-17-30

http://www.wired.com/wiredscience/2012/04/paleo-birding/