Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2015 Jun 16:3:e1018.
doi: 10.7717/peerj.1018. eCollection 2015.

Were early pterosaurs inept terrestrial locomotors?

Affiliations

Were early pterosaurs inept terrestrial locomotors?

Mark P Witton. PeerJ. .

Abstract

Pterodactyloid pterosaurs are widely interpreted as terrestrially competent, erect-limbed quadrupeds, but the terrestrial capabilities of non-pterodactyloids are largely thought to have been poor. This is commonly justified by the absence of a non-pterodactyloid footprint record, suggestions that the expansive uropatagia common to early pterosaurs would restrict hindlimb motion in walking or running, and the presence of sprawling forelimbs in some species. Here, these arguments are re-visited and mostly found problematic. Restriction of limb mobility is not a problem faced by extant animals with extensive fight membranes, including species which routinely utilise terrestrial locomotion. The absence of non-pterodactyloid footprints is not necessarily tied to functional or biomechanical constraints. As with other fully terrestrial clades with poor ichnological records, biases in behaviour, preservation, sampling and interpretation likely contribute to the deficit of early pterosaur ichnites. Suggestions that non-pterodactyloids have slender, mechanically weak limbs are demonstrably countered by the proportionally long and robust limbs of many Triassic and Jurassic species. Novel assessments of pterosaur forelimb anatomies conflict with notions that all non-pterodactyloids were obligated to sprawling forelimb postures. Sprawling forelimbs seem appropriate for species with ventrally-restricted glenoid articulations (seemingly occurring in rhamphorhynchines and campylognathoidids). However, some early pterosaurs, such as Dimorphodon macronyx and wukongopterids, have glenoid arthrologies which are not ventrally restricted, and their distal humeri resemble those of pterodactyloids. It seems fully erect forelimb stances were possible in these pterosaurs, and may be probable given proposed correlation between pterodactyloid-like distal humeral morphology and forces incurred through erect forelimb postures. Further indications of terrestrial habits include antungual sesamoids, which occur in the manus and pes anatomy of many early pterosaur species, and only occur elsewhere in terrestrial reptiles, possibly developing through frequent interactions of large claws with firm substrates. It is argued that characteristics possibly associated with terrestriality are deeply nested within Pterosauria and not restricted to Pterodactyloidea as previously thought, and that pterodactyloid-like levels of terrestrial competency may have been possible in at least some early pterosaurs.

Keywords: Dimorphodon macronyx; Functional morphology; Locomotion; Palaeoecology; Pterosaurs; Terrestrial locomotion.

PubMed Disclaimer

Conflict of interest statement

The author declares there are no competing interests.

Figures

Figure 1
Figure 1. Select hypotheses for non-pterodactyloid poses made in the last 35 years.
(A) Padian’s (1983a) bipedal Dimorphodon macronyx; (B) redrawn lateral view of the ‘Roborhamphus’ model discussed by Unwin (2005); (C) quadrupedal Dorygnathus banthensis with sprawling forelimbs, reversed from Padian (2008b).
Figure 2
Figure 2. Pterosaur and bat uropatagia compared.
(A) line drawing of hindlimb region of Sordes pilosus specimen PIN 2885/3, showing extensive, toe-supported uropatagium (dark shading) and associated brachiopatagia (light shading); (B) skeletal reconstruction of Rhamphorhynchus muensteri showing distribution of membranes in non-pterodactyloid pterosaurs based on fossil remains (see Elgin, Hone & Frey, 2011); (C) line drawing of hanging common vampire bat Desmodus rotundus, a terrestrially-competent species with an extensive uropatagium analogous to those of non-pterodactyloid pterosaurs. Note Desmodus has a small uropatagium compared to other, terrestrially-adept bat species. Scale bar of (A) represents 10 mm, other images not to scale. Abbreviations: Brachio, brachiopatagium; CV, caudal vertebrae; Ep, epiphysis, Fem, femur; Fib, fibula; Pel, pelvis; Pro, propatagium; Ta, tarsals; Tib, tibia; Uro, uropatagium; WP, wing phalanx (numerals denote phalanx number); i–v denote pedal digit numbers. (A) modified from Unwin & Bakhurina (1994); (B) modified from Witton (2013); (C) redrawn from photograph in Nowak (1994).
Figure 3
Figure 3. Non-pterodactyloid glenoid morphology.
(A–C) line drawings of NHMUK R1034 Dimorphodon macronyx left scapulocoracoid in anterodorsal (A), lateral (B) and ventrolateral (C) aspect; (D–G), NHMUK R5672, indeterminate rhamphorhynchine right scapulocoracoid in dorsal (D), ventral (E), lateral (F) and anterior (G) aspects; (H) photograph of the NHMUK R1034 glenoid (‘symmetric’ morph), in posteroventral aspect; (I) photograph of NHMUK R5672 (‘asymmetric’ morph) in posteroventral aspect; (J) schematic reconstruction of a non-pterodactyloid torso with a symmetric (i) and asymmetric (ii) glenoid conditions, where green shading approximates articulatory range of the humerus in the vertical plane based on extent of articular surface. Scapulocoracoids in (J) reconstructed based on specimens illustrated herein and models of pectoral anatomy presented for other early pterosaurs (Wellnhofer, 1975; Wellnhofer, 1991; Bennett, 2003). Note this is only approximate for Dimorphodon because its sternum remains unknown. ac, acromion process; ar, articular face of glenoid; cor, coracoid, lt, lower tubercle; sc, scapula; sb, supraglenoidal buttress. Scale bars represent 10 mm. (J) modified from Wellnhofer (1991).
Figure 4
Figure 4. Pterosaur humeri in anterior view, showing development of lateral and medial epicondyles adjacent to the capitula and trochleae (shaded grey) in non-pterodactyloids (A–F) and pterodactyloids (G–I).
(A) NHMUK 42016, Dimorphodon macronyx; (B) YPM 350 (F) Di. macronyx; (C) JPM04-0008, Archaeoistiodactylus linglongtaensis; (D) Wellnhofer’s (1975) Rhamphorhynchus muensteri humerus; (E) SMNS 51827, Dorygnathus banthensis; (F) SMNS 50164, Do. banthensis; (G) YPM 1164, Pteranodon sp; (H) MOR 691, Montanazhdarcho minor; (I) IVPP V.2777, Dsungaripterus weii. Note the relatively poorly developed epicondyles in (D–F) and how the distal humeri of (A–C) resemble those of pterodactyloids more than other non-pterodactyloids. Ca, capitulum; LE, lateral epicondyle; ME, medial epicondyle; Tr, trochlea. Scale bars represent 10 mm, except for (G) and (H), which equal 50 mm. (B) after Padian (1983a); (D) after Wellnhofer (1975); (E) after Padian (2008b); (G) modified from Bennett (2001); (H) after McGowen et al. (2002); (I) after Young (1964). (D), (E) and (H) are reversed from their sources to enhance comparability.
Figure 5
Figure 5. Skeletal reconstructions of non-pterodactyloid pterosaurs.
Are non-pterodactyloids ubiquitously equipped with short, slender limbs? Skeletal reconstructions of taxa such as Preondactylus bufarini (A), Dimorphodon macronyx (B) and Anurognathus ammoni (C and D, in erect and crouched poses respectively, acknowledging the poorly known glenoid condition of anurognathids) show they have proportionally long, robust limbs. Only some non-pterodactyloids, including the Early Jurassic campylognathoidid Campylognathoides liasicus (E) and Late Jurassic rhamphorhynchine Rhamphorhynchus muensteri (F) have proportionally short and slender hindlimbs. Preondactylus has been reconstructed with erect forelimbs based on its grossly similar humeral morphology to Dimorphodon, although it remains to be established that this similarity extends to more detailed forelimb anatomy. Scale bars represent 100 mm, except for (C) and (D), which represent 50 mm. Skeletal reconstructions modified from Witton (2013).
Figure 6
Figure 6. Antungual sesamoids in pterosaurs.
(A) manus and pes of NHMUK 41212 Dimorphodon macronyx; (B) partial pes skeleton of GSM 1546 Di. macronyx; (C) manus of BSP 1938 I 49 Dorygnathus banthensis; (D) proposed interactions of pterosaur unguals with hard substrates, and utilisation of antungual sesamoids (extensor tendon shown in grey shading). (Di) terminal phalanges of Dimorphodon manual digit 2 show as resting on a hard substrate without loading; (Dii) passive hyperextension of the ungual, where pulling or depressing the phalanges (force vectors shown with arrows) retract the ungual to contact the sesamoid; (Diii) active hyperextension of the ungual, where the extensor tendon is pulled to clear the ungual tip of the ground using the additional lever arm length afforded by the sesamoid. (A–C) shading and numbers denote identification of clawed digits (Arabic numerals for manual digits, unary for pedal). Some skeletal elements present on the illustrated specimens are omitted for clarity. mc1-3, metacarpals 1-3; mt1-4, metatarsals 1-4; mt5, metatarsal 5; pd v, pedal digit 5; r, dorsal rib; s, sesamoids; wmc, wing metacarpal; wp, wing finger proximal phalanx. Scale bars represent 10 mm.
Figure 7
Figure 7. Distribution of characteristics linked to terrestrial capabilities in non-pterodactyloids in a simplified pterosaur phylogeny (based on Lü et al., 2012).
Other pterosaur phylogenies suggest different topologies of non-pterodactyloid taxa (see text for details), but the distribution of these characteristics would be as complex, if not more so, in competing arrangements.
Figure 8
Figure 8. Potential variation in terrestrial locomotion gait in non-pterodactyloid pterosaurs.
(A) life restoration of the Early Jurassic rhamphorhynchine Dorygnathus banthensis with obligated crouching, somewhat sprawled forelimbs; (B) life restoration of the Early Jurassic species Dimorphodon macronyx with fully adducted humeri and parasagittal gait, shown here facilitating subcursorial, rapid terrestrial locomotion in pursuit of sphenodontian prey. Both animals are restored with retracted claws on digits possessing antungual sesamoids.

References

    1. Abourachid A, Höfling E. The legs: a key to bird evolutionary success. Journal of Ornithology. 2012;153:193–198. doi: 10.1007/s10336-012-0856-9. - DOI
    1. Andres B, Clark JM, Xing X. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs. Journal of Vertebrate Paleontology. 2010;30:163–187. doi: 10.1080/02724630903409220. - DOI
    1. Andres B, Clark J, Xu X. The earliest pterodactyloid and the origin of the group. Current Biology. 2014;24:1011–1016. doi: 10.1016/j.cub.2014.03.030. - DOI - PubMed
    1. Andres B, Myers TS. Lone star pterosaurs. Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 2012;103:383–398. doi: 10.1017/S1755691013000303. - DOI
    1. Autumn K, Hsieh ST, Dudek DM, Chen J, Chitaphan C, Full RJ. Dynamics of geckos running vertically. Journal of Experimental Biology. 2006;209:260–272. doi: 10.1242/jeb.01980. - DOI - PubMed

LinkOut - more resources