RECONSTRUCTING THE FLIGHT APPARATUS OF EUDIMORPHODON
NATALIE N. BAKHURINA & DAVID M. UNWIN
Institut für Paläontologie, Museum für Naturkunde, Zentralinstitut der Humboldt-Universität zu Berlin, D-10115 Berlin, GERMANY.
Eudimorphodon is the commonest and best known pterosaur from the Upper Triassic. A long-tailed form that reached about one metre in wingspan, it has been reported from Italy (Wild 1978, 1994, Dalla Vecchia 1995, 2003), Austria (Wellnhofer 2003), Greenland (Jenkins et al. 2001) and possibly also from Switzerland, Belgium, Luxembourg and the USA (Dalla Vecchia 2003). Older systematic (Wild 1978) and newer phylogenetic analyses (Unwin 2003) both support a close relationship between Eudimorphodon and Campylognathoides which form the Campylognathoididae, a relatively derived clade of basal pterosaurs.
The skeletal anatomy of Eudimorphodon is more completely known than for any other early pterosaur, and it is the only Triassic form in which soft tissues have been reported so far (Wild 1994, Dalla Vecchia 1995). Published restorations of the flight membranes indicate a small propatagium anterior to the fore limb and a cheiropatagium attached to the rear margin of the fore limb and the body as far as the hip (Wild 1978), or extending to just beyond the knee (Wellnhofer 1991). There is no cruropatagium (= uropatagium) shown in the reconstructions by Wild (1978, tafs 10, 16) or Wellnhofer (1991, p. 63), but small, crescentic membranes stretched between the leg and the base of the tail are indicated in a painting in the 'Encyclopedia of Pterosaurs' (Wellnhofer 1991, p. 61). Preservation of parts of the wing membranes in a juvenile example of Eudimorphodon (MCSNB 8950; Figure 1) led Wild (1994) to suggest that the cheiropatagium may have attached to the fifth toe and, by inference, to the hind limb.
Combining published details of the disposition of the skeletons of Eudimorphodon, and the distribution of impressions of the wing membranes in MCSNB 8950 (Wild 1994) with understanding of wing membrane distribution in Sordes pilosus (Sharov 1971, Unwin & Bakhurina 1994) permits a new restoration of the flight apparatus of Eudimorphodon.
Sordes pilosus is represented by eight individuals, several exhibiting exceptionally well preserved soft tissues (Bakhurina & Unwin 1995) from the Upper Jurassic Karabastau Svita (Oxfordian-Kimmeridgian) of the Karatau Ridge in Kazakhstan (Sharov 1971, Bakhurina & Unwin 1995, Unwin & Bakhurina 2000). Evidence of the wing membranes is more completely preserved in Sordes than in any other pterosaur and demonstrates that there was a small propatagium, a cheiropatagium that attached to the fore limb, body and hind limb as far as the distal end of the crus, and a cruropatagium stretched between the hind limbs and supported along its rear edge by the fifth toes (Unwin & Bakhurina 1994; Figure 2).
In MCSNB 8950 the hind limbs, foot and fifth toe show an almost identical disposition to that seen in the holotype of Sordes (PIN 2585/3, Sharov 1971, Unwin & Bakhurina 1994) as do the preserved portions of the wing membrane. In particular, patches of soft tissue located between the ankles (Figure 2b, c), with a lineation that has been interpreted as 'hair-like structures' (Wild 1994, fig. 9) and 'structural fibres' (Wild 1994, fig. 11), form part of the cruropatagium. In our opinion, the lineation represents patagial fibres and has the same orientation and spacing as in the cruropatagium of Sordes (cf. Bakhurina & Unwin 1995, fig. 7). We argue, therefore, that our reconstruction of the wing membranes in Eudimorphodon corresponds to that evident in Sordes and is generally applicable to other basal ('rhamphorhynchoid') pterosaurs especially in regard to the hind limbs, with attachment of the cheiropatagium to the femur and crus and the presence of a cruropatagium stretched between the hind limbs that was supported and manipulated by the fifth toes.
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