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, 277 (1679), 321-9

The Soft Tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the Structure of the Pterosaur Wing Membrane

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The Soft Tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the Structure of the Pterosaur Wing Membrane

Alexander W A Kellner et al. Proc Biol Sci.

Abstract

The soft tissue preserved in the holotype (IVPP V12705) of Jeholopterus ningchengensis from the Daohugou Bed (Late Jurassic or Early Cretaceous) of China is described in detail. The plagiopatagium can be divided into the distal, comparatively more rigid actinopagatium and a proximal, more tensile tenopatagium. The actinopatagium extends from the wing finger to the articulation between the humerus and the forearm, and shows the presence of at least three layers containing actinofibrils. In each layer, the actinofibrils are parallel to subparallel, but this direction diverges from layer to layer. When distinct layers of actinofibrils are superimposed (owing to taphonomic compression), a reticular pattern is generated. The presence of layers with differently oriented actinofibrils is widespread in this pterosaur. A well-developed integumental covering formed by fibres (here named pycnofibres) that are thicker than the actinofibrils is present. Ungual sheaths that extend the length of the pedal and manual claws of this taxon are also observed. Although the understanding of the mechanical properties of the wing membrane is hampered by the lack of knowledge regarding the composition of the actinofibrils, the configuration observed in Jeholopterus might have allowed subtle changes in the membrane tension during flight, resulting in more control of flight movements and the organization of the wing membrane when the animal was at rest.

Figures

Figure 1.
Figure 1.
Jeholopterus ningchengensis (IVPP V12705), top slab under natural light. Sketch indicates the bones and the different soft tissue preserved. Scale bar, 50 mm.
Figure 2.
Figure 2.
Jeholopterus ningchengensis (IVPP V12705), top slab, under ultraviolet light. The yellowish substance is resin that was employed to glue parts of the specimen. Note the whitish matter, interpreted as the epidermis (and part of the dermis; see text). Scale bar, 50 mm. acpt, actinopatagium; conc, conchostracans; inc, integumental covering; inc-t, integumental covering of the tail; tenp, tenopatagium; upt, uropatagium.
Figure 3.
Figure 3.
Details of the soft tissue of J. ningchengensis (IVPP V12705). (a) Region close to the right tibia (bottom slab). Scale bar, 10 mm. (b) Actinopatagium close to the second and third wing finger phalanxes of the right wing. Scale bar, 1 mm. acpt, actinopatagium; ep/de, epidermis/dermis; inc, integumental covering; ph2d4, second phalanx of the wing finger; ti, tibia.
Figure 4.
Figure 4.
Soft tissue of J. ningchengensis (IVPP V12705). (a) Details of the actinopatagium with different layers indicated by white arrows (top slab). (b) Actinopatagium under ultraviolet light showing the difference between the actinofibrils and the integumental covering (dark colour). (c) Tip of the wing membrane associated with the fourth phalanx of the right wing finger. (d) Ungual sheaths of the right manual digits indicated by black arrows. Scale bars: (ac) 1 mm; (d) 10 mm. acpt, actinopatagium; f-B, fibres type B; inc, integumental covering; laf, different layers of actinofibrils; maf, merging actinofibrils; ph2d4, second phalanx of the wing finger; ra/ul, radius and ulna; us, ungual sheaths.

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