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Abstract

Pterosaur fossils have been discovered all over the world [1], but so far no flightless pterosaurs have been reported. Here an old and rarely studied pterosaur fossil (Sos 2428) in the collection of the Jura Museum in Eichstätt, Germany, was reexamined and found to have a reduced pectoral girdle, small proximal wing elements (humerus, radius and ulna), three vestigial distal wing elements, the relatively longest pelvis of any pterosaur and the widest gastralia, or belly ribs. This discovery represents a unique morphology for pterosaurs. The Jura specimen lacked the wing size, forelimb muscularity and aerodynamic balance necessary to sustain flapping flight. It was a likely herbivore. The fossil (Sos 2428) came to the Jura Museum from the collection of the Bishop's Seminary in Schamhaupten. Its original location was given as the silicified plattenkalk of Schamhaupten, Germany (Upper Kimmeridgian,155-150 million years ago). In the Late Jurassic this pterosaur lived on or near a warm, semi-arid island [2]. Associated fossils from the same horizon include the small theropod, Juravenator starki [3]. Sos 2428 was preserved in part and several smaller counterparts lifted from the top of the plate and from the bottom, which reveals more skull material. In the original description [4] several bones were considered missing, including the distal mandible, scapula, coracoid, humerus, radius, ulna, carpus, pteroid, the medial manual digits (I and II), the distal phalanges of digit IV and the distal hind limb. Now only the distal mandible and distal hind limb remain unknown (Fig. 1). Tiny distal wing elements were found curled up between the first and second dorsal ribs (the 9th and 10th post-cranial vertebral ribs (Fig. 1a, b)) in close association and nearly articulated. Atypical for pterosaurs (Fig. 1c-g), the largest of these elements (m4.2) was only the size of a dorsal rib, which is how it escaped detection until now. The others (m4.3, m4.4) were much smaller, mere vestiges. Each distal wing phalanx was at least halved in diameter by mid shaft. A strong curve developed in m4.3 that is
First Flightless Pterosaur
David Peters
no affiliation
9 Greenfield Court, Saint Charles, MO 63303 USA
Pterosaur fossils have been discovered all over the world [1], but so far no flightless pterosaurs
have been reported. Here an old and rarely studied pterosaur fossil (Sos 2428) in the collection
of the Jura Museum in Eichstätt, Germany, was re-examined and found to have a reduced
pectoral girdle, small proximal wing elements (humerus, radius and ulna), three vestigial distal
wing elements, the relatively longest pelvis of any pterosaur and the widest gastralia, or belly
ribs. This discovery represents a unique morphology for pterosaurs. The Jura specimen lacked
the wing size, forelimb muscularity and aerodynamic balance necessary to sustain flapping
flight. It was a likely herbivore.
The fossil (Sos 2428) came to the Jura Museum from the collection of the Bishop's Seminary in
Schamhaupten. Its original location was given as the silicified plattenkalk of Schamhaupten,
Germany (Upper Kimmeridgian,155-150 million years ago). In the Late Jurassic this pterosaur
lived on or near a warm, semi-arid island [2]. Associated fossils from the same horizon include the
small theropod, Juravenator starki [3].
Sos 2428 was preserved in part and several smaller counterparts lifted from the top of the plate
and from the bottom, which reveals more skull material. In the original description [4] several bones
were considered missing, including the distal mandible, scapula, coracoid, humerus, radius, ulna,
carpus, pteroid, the medial manual digits (I and II), the distal phalanges of digit IV and the distal
hind limb. Now only the distal mandible and distal hind limb remain unknown (Fig. 1). Tiny distal
wing elements were found curled up between the first and second dorsal ribs (the 9th and 10th post-
cranial vertebral ribs (Fig. 1a, b)) in close association and nearly articulated. Atypical for pterosaurs
(Fig. 1c-g), the largest of these elements (m4.2) was only the size of a dorsal rib, which is how it
escaped detection until now. The others (m4.3, m4.4) were much smaller, mere vestiges. Each distal
wing phalanx was at least halved in diameter by mid shaft. A strong curve developed in m4.3 that is
more typically seen in m4.4.
Sos 2428 was considered [4] a variety of Pterodactylus longicollum with a skull “slightly
smaller” and cervical vertebrae “a little longer.” These distinctions were then considered [4] in the
range of either individual variation or sexual dimorphism. This specimen has never been included
in any prior cladistic analyses. Here the generic distinctions warrant a cladistic analysis and a
revision of the nomenclature, subjects to be dealt with in a separate paper.
A related, more primitive, but contemporary and likewise mislabeled Pterodactylus specimen
is BSt 1911 I 31 (Fig. 1c, g), housed in the Bavarian State Collection for Palaeontology and
Geology. It shared with the Jura specimen (Sos 2428) a flat rostrum, elongated neck, similar
proportions in fingers I-III and a slender build with wide gastralia. Otherwise this much smaller
specimen had proportions more typical of other pterosaurs. It was clearly able to fly with a wingspan
9x longer than the torso. When graphically enlarged to the same glenoid-acetabulum length as Sos
2428 (Fig. 1c, d), the differences between these sister taxa become quite clear. While the skulls were
similar in length, in Sos 2428 the neck was slightly longer, the pectoral girdle and the entire wing
were much smaller, the torso was somewhat larger and the pelvis was considerably longer and more
fully fused. The wing of the Jura specimen (Sos 2428) was half as long with a chord only half as
deep on a heavier body compared to the scaled-up version of BSt 1911 I 31. Most other wing and
pectoral elements of Sos 2428 were similarly halved in all dimensions. The reconstructed wingspan
of Sos 2428 was only 5x the torso length.
Certain other pterosaurs also experienced distal wing phalanx reduction and loss. The
University of Nebraska in Lincoln specimen of Nyctosaurus (UNSM 93000) had only three wing
phalanges with the curved terminal phalanx (m4.3) less than half as long as m4.2 [5]. In this case the
hyperelongation of the metacarpus added to a wingspan 18x longer than the torso. The pectoral
girdle was robust and the torso was unexpanded. In the azhdarchid, Quetzalcoatlus [6], m4.4 was a
vestige and the folded wing extended only a short distance beyond the elbow. As in Nyctosaurus, the
hyperelongation of the metacarpus added to a wingspan 12x longer than the torso and the pectoral
girdle was robust. In contrast, the Institute of Vertebrate Paleontology and Paleoanthropology,
Academia Sinica in Beijing specimen of another azhdarchid, Zhejiangopterus linhaiensis (IVPP V
13397), had similar wing phalanx proportions to Quetzalcoatlus, but a wingspan only 8x the torso
length [7]. The humerus and other wing elements were relatively slender and short. In this case the
pectoral girdle was not robust, but much smaller than the pelvis + prepubis. The pelvis was enlarged
to half the torso length. These reductions and modifications would have made Zhejiangopterus the
weakest flyer among known pterosaurs after the Jura specimen (Sos 2428).
In the Jura specimen (Sos 2428) the more drastic reductions in the wingspan would have
further reduced the ability to fly without affecting the ability to travel quadrupedally. In comparison
to BSt 1911 I 31, the further lengthening of the pelvis and increased fusion in the sacrum in Sos 2428
indicate that larger stresses were encountered there. While typically quadrupedal while feeding or
fleeing, if cornered by a predator or rival into a defensive bluff, this pterosaur with a reinforced
pelvis and sacrum could have stood upright, spreading and weakly flapping its clipped wings.
The increase in gastralia width indicates an increase in torso volume. Similar increases in other
extinct amniote taxa, such as therizinosaurids, are widely considered to indicate herbivory [8],
another behaviour considered atypical for pterosaurs.
1. Wellnhofer, P. The Illustrated Encyclopedia of Pterosaurs 1–192 (Salamander, London, 1991).
2. Viohl, G. & Zapp. M. Schamhaupten, an outstanding Fossil-Lagerstätte in a silicified
Plattenkalk around the Kimmeridgian-Tithonian boundary (Southern Franconian Alb, Bavaria)
Neues Jahr. Min., Geo. Palaeo. Abh. 245, 127142 (2007).
3. Göhlich, U. B. & Chiappe, L. M. A new carnivorous dinosaur from the Late Jurassic Solnhofen
archipelago. Nature 440, 329332 (2006).
4. Wellnhofer, P. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands.
Abh Bayer Akad Wiss, N.F., Munich 141, 1–133 (1970).
5. Brown, G.W. Reassessment of Nyctosaurus: new wings for an old pterosaur. Proc. Nebraska
Acad. Sci. 96, 47 (1986).
6. Lawson, D. A. Pterosaur from the Latest Cretaceous of West Texas. Discovery of the Largest
Flying Creature. Science, 187, 947948 (1975).
7. Cai Z. & Wei F. On a new pterosaur (Zheijangopterus linhaiensis gen. et sp. nov.) from Upper
Cretaceous in Linhai, Zhejiang, China. Vert. Palas. 32, 181194 (1994).
8. Zanno, L. E., Gilette, D.D., Albright, L. B. & Titus, A. L. A new North American
therizinosaurid and the role of herbivory in ‘predatory’ dinosaur evolution. Proc. R. Soc. B 276,
3505-3511 (2009).
I thank D. Hone, M. Kölbl-Ebert and the staffs of the Jura Museum, Eichsätt,and the Bayerische Staatssammlung für
Paläontologie und historische Geologie in Munich for providing access to specimens in their care. Discussions with
A. Kellner and M. Habib provided assistance.
Correspondence and requests for materials should be addressed to D.P. (e-mail: davidpeters@att.net.)
Figure 1. A flightless pterosaur and a smaller flight-worthy relative compared. a. Close-up
photograph of the Jura specimen (Sos 2428) in situ. b. Labeled tracing of same. The
vertebrae and ribs are light blue and numbered postcranially. The coracoid (co) is in darker
blue. The elements of the wing finger are in light red (m4.1), green (m4.2), violet (m4.3),
and amber (m4.4). Possible wing membrane material in gray. c. Reconstruction in dorsal
view of the left half of the Bavarian specimen, BSt 1911 I 31. Scale bar = 2 cm. d.
Reconstruction in dorsal view of the right half of the Jura specimen, Sos 2428. Scale bar =
10 cm. e. Reconstruction of Sos 2428 standing in lateral view, plus the gastralia in dorsal
view, the mandibles in ventral view, the sternal complex in dorsal view and the sacrum in
dorsal view. f. Close-up of the reconstructed distal wing elements of Sos 2428. g.
Reconstruction of BSt 1911 I 31 standing in lateral view, plus another lateral view of the
femur, a dorsal view of the gastralia and a dorsal view of the pes enlarged. Scale bar = 10
cm.
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Article
Full-text available
Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the tail, the new fossil is the best-preserved predatory, non-avian dinosaur in Europe. It possesses a suite of characters that support its identification as a basal coelurosaur. A cladistic analysis indicates that the new taxon is closer to maniraptorans than to tyrannosauroids, grouping it with taxa often considered to be compsognathids. Large portions of integument are preserved along its tail. The absence of feathers or feather-like structures in a fossil phylogenetically nested within feathered theropods indicates that the evolution of these integumentary structures might be more complex than previously thought.
The silicified plattenkalk of Schamhaupten, which was deposited in a basin surrounded by massive facies (now dolomite) and placed around the Kimmeridgian-Tithonian boundary, has proved to be a Fossil-Lagerstätte of great diversity. About 200 taxa can be distinguished so far, and probably there are much more. The most spectacular find is the small theropod Juravenator starki. The abundant pelagic forms (coccolithophorids, radiolarians, cephalopods, the planktonic crinoid Saccocoma, most fishes, and marine reptiles) can be regarded as autochthonous and indicate good connections to the Tethys. All benthic and demersal organisms (foraminifers, sponges, brachiopods, bryozoans, bivalves, gastropods, crustaceans, echinoids, sessile crinoids, and some fishes) as well as terrestrial organisms were allochthonous and washed into the basin. The lithology is characterized by two main rock types: bindstones containing articulated fossils and detrital beds with only shells and other skeletal elements. During diagenesis the limestones underwent a strong silification which took place in at least two phases. If it occurred before the compaction of the sediment, it could lead to excellent three-dimensional preservation of fossils.Due to the warm, semi-arid climate a salinity-density stratification had developed in the basin leading to a hypersaline, dysaerobic bottom zone which was hostile to benthic life. Only microbial mats could thrive there forming bindstones by trapping sedimentary particles. They played an important role in the conservation of articulated fossils. The rims of the basin which now appear as massive dolomite consisted of an arenitic substrate, probably bound by microbial mats and partly settled by sponges. Storm events reworked it and triggered turbulent density currents which deposited the detrital carbonates in the basin. Nearby, probably to the south, an island must have emerged where land plants and terrestrial animals have come from.
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Three partial skeletons of a large pterosaur have been found in the latest Cretaceous nonmarine rock of West Texas. This flying reptile had thin, elongate, perhaps toothless jaws and a long neck similar to Pterodaustro and Pterodactylus. With an estimated wingspan of 15.5 meters, it is undoutbtedly the largest flying creature presently known.
The Illustrated Encyclopedia of Pterosaurs 1-192 (Salamander
  • P Wellnhofer
Wellnhofer, P. The Illustrated Encyclopedia of Pterosaurs 1-192 (Salamander, London, 1991).
Reassessment of Nyctosaurus: new wings for an old pterosaur
  • G W Brown
Brown, G.W. Reassessment of Nyctosaurus: new wings for an old pterosaur. Proc. Nebraska Acad. Sci. 96, 47 (1986).
A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution
  • L E Zanno
  • D D Gilette
  • L B Albright
  • A L Titus
Zanno, L. E., Gilette, D.D., Albright, L. B. & Titus, A. L. A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution. Proc. R. Soc. B 276, 3505-3511 (2009).
Kölbl-Ebert and the staffs of the Jura Museum, Eichsätt,and the Bayerische Staatssammlung für Paläontologie und historische Geologie in Munich for providing access to specimens in their care
  • D I Thank
  • M Hone
I thank D. Hone, M. Kölbl-Ebert and the staffs of the Jura Museum, Eichsätt,and the Bayerische Staatssammlung für Paläontologie und historische Geologie in Munich for providing access to specimens in their care. Discussions with A. Kellner and M. Habib provided assistance.