A FLIGHTLESS PTEROSAUR, JME-Sos2428David Petersdavidpeters@att.netdavidpetersstudio.comSt Charles, MO 63303

JME-Sos2428 is a largely complete, crushed, Solnhofen pterosaur. It was previously considered another specimen of Ardeadactylus (formerly Pterodactylus) longicollum (neotype: SMNS 56603). However, a closer look reveals important di�erences.

The skull is longer than the cervical series in JME-SosSos2428, but not in Ardeadactylus. The slender cervical ribs are each a centrum length in JME-Sos2428, but they are much shorter in Ardeadactylus. The parasagittally compressed dorsal vertebrae comprise only 40% of the torso length in JME-Sos2428, but 66% in the more typical pterosaur, Ardeadactylus. Conversely, in JME-Sos2428 the robust sacral series extends for 60% of the torso, 34% in Ardeadactylus. In JME-Sos2428 the dorsal ribs, sternal ribs and gastralia are relatively twice the lengths of those found in Ardeadactylus. The pectoral girdle is gracile in JME-Sos2428, with a scapula and a coracoid half the width of those same elements in Ardeadactylus. The forelimb (wing) elements are likewise less than half the length and width of those in Ardeadactylus. The wing �nger (manual digit 4) is further reduced relative to the rest of the wing. When folded the unreduced �rst wing phalanx extends back to the carpus. However, the second wing phalanx is half that length. The third phalanx is half the second and the fourth is less than half the third. Thus, when folded, the distal tip of the reduced wing �nger extends just to the elbow. By comparison, in Ardeadactylus the elbow meets the middle of the second wing phalanx and the two distal phalanges nearly double that length. In JME-Sos2428 the free �ngers, digits 1-3, are not reduced. Matching the elongated sacrum in JME-Sos2428, the hyperelongated ilium extends for 60% of the torso length. However, the much smaller pubis, prepubis, ichium and femur are similar in size to those same elements in Ardeadactylus. In JME-Sos2428 the distal tibia and pes are not preserved.

When reconstructed, JME-Sos2428 has a relatively longer and wider torso than any other known pterosaur. It also has a reduced wing, half the length and half the chord of the wing of Ardeadactylus when scaled to the same torso length.

Such a reduced wing and such an enlarged torso make the prospect of �ight rather doubtful by comparison. Moreover, with such morphological di�erences, JME-Sos2428 is clearly a distinct genus. JME-Sos = Jura Museum Solnhofen-Sammlung; Eichstatt, Germany

HomoeosaurusHuehuecuetzpalliMacrocnemus BES SC111Macrocnemus T4822Macrocnemus T2472DinocephalosaurusJesairosaurusHypuronectorVallesaurusDrepanosaurusMegalancosaurusAmotosaurusLangobardisaurusTanytrachelosTanystropheus aTanystropheus k and qCosesaurusSharovipteryxLongisquamaMPUM 6009RaeticodactylusAustriadactylus holotypeAustriadactylus-SC332466Dimorphodon macronyxPreondactylusPeteinosaurus Ex3359CarniadactylusMCSNB 8950IVPP V13758 embryoMesadactylus Jenson and PadianDimorphodon? weintraubiDendrorhynchoidesGLGMV0002Flathead anurognathidAnurognathusCAG IG 02-81JeholopterusBatrachognathusEudimorphodon ranziiEudimorphodon cromptonellusEudimorphodon BSp 1994ChangchengopterusCampylognathoides Paris C4Campylognathoides zitteli CzCampylognathoides zitteli C5NesodactylusCampylognathoides liasicus C3Rhamphorhynchus intermedius n28Rhamphorhynchus BSPG1960 I 470ABellubrunnusQinglongopterusRhamphorhynchus longicaudus n10Rhamphorhynchus ViennaRhamphorhynchus n11Rhamphorhynchus ROM 55352Rhamphorhynchus longicepsRhamphorhynchus ThermopolisRhamphorhynchus n62Rhamphorhynchus darkwingRhamphorhynchus MTM V2008.33.1Rhamphorhynchus n33Rhamphorhynchus n43Rhamphorhynchus n74Rhamphorhynchus n38Rhamphorhynchus n75Rhamphorhynchus n52SordesDorygnathus DonauDorygnathus SMNS 58127CacibuteryxDorygnathus SMNS 50164TM 10341BeipiaopterusHuanhepterusMesadactylus SmithCM 11 426 n44Dublin castB St 1911 I 31 n42SOS2428SOS 2179JidapterusChaoyangopterus LPM-R00076MicrotubanChaoyangopterus holotypeZhejiangopterusQuetzalcoatlusFenghuangopterusDorygnathus SMNS 55886Dorygnathus Up R 156SericipterusDorygnathus purdoniAngustinaripterusSt/E1IMBR 3530.1 n40Ctenochasma elegans privateAMNH 5147GnathosaurusCtenochasma elegans n45GegepterusGladocephaloideusCtenochasma n65 BPropterodaustroPterodaustroPterodaustro embryoJianchangnathus and descendants

JianchangnathusPterorhynchusKunpengopterusWukongopterusDarwinopterusScaphognathus crassirostrisScaphognathus SMNS 59395Scaphognathus MaxbergTM 13104Gmu10157BSp 1986 XV 132Pterodactylus? micronyx-PesterB St 1936 I 50 n30CycnorhamphusMoganopterusFeilongusYixianopterusMSNM V 3881Lebanon Ornithocheirid CompleteJZMP embryoHaopterusBoreopterusZhenyuanopterusArthurdactylusColoborhynchus spielbergiCriorhynchusOrnithocheirid SMNK PAL 3854.NurhachiusSMNS 1136 PALIstiodactylusBrasileodactylusLudodactylusGuidracoCearadactylus ligabueiCearadactylus atroxLiaoningopterusAnhanguera piscatorOrnithocephalusn9 SOS4593n31 SOS4006SMNS 81775NingchengopterusPterodactylus AMNH 1942 n20Pterodactylus NHMW 1975 viennaPterodactylus n21Pterodactylus n37Pterodactylus FreyTischPterodactylus antiquus n4Pterodactylus BM0007Diopecephalus n58No6BMNH 42736No12No23Germanodactylus rhamphastinusEosipterusJME GermanodactylusGermanodactylus BMM PrivateMOZ 3625PCuspiscephalusGermanodactylus cristatus n61azhdarchide? PAL 3830PhobetorDsungaripterusNoripterusNemicolopterusShenzhoupterusSinopterusTapejaraHuaxipterusTupandactylusTupuxura longicristatusThalassodromeusTupuxura GoshuraGermanodactylus KarlsuhePrejanopterusElanodactylusNo13EopteranodonAurorazhdarchoEoazhdarchoMuzquizopteryxNyctosaurus FHSMVP21Nyctosaurus FMNH25026Nyctosaurus UNSM93000Nyctosaurus KJ1Nyctosaurus KJ2Pteranodon YPM 1179Pteranodon FHSM 2183Pteranodon UUPI R197Pteranodon YPM 1177Pteranodon KUVP 2212 skullPteranodon YPM 2594Pteranodon Jenkins skullPteranodon CMC VP7203Pteranodon FHSM 2851Pteranodon NMC41 358Pteranodon KUVP 27821Pteranodon FHSM VP339

BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog)

CM 11426 (no. 44 in the Wellnhofer 1970 catalog)

Another possible �ightless pterosaur?

dorsal ribs dorsal and sacral vertebrae

prepubes

gastralia

m4.1m4.2

m4.3

m4.4

humerus

carpals

scapula

coracoid

sternal complex

JME-Sos 2428 vestigial wing

mc4

pteroid

preaxial carpal

Examples of Digital Graphic Segregation in which a complex “roadkill” fossil parts are color and layer segregated to aid in identi�cation and reconstruction.

BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog)

CM 11426 (no. 44 in the Wellnhofer 1970 catalog)

JME-Sos 2479, known from a skull, phylogenetically nests with Sos2428.

JME-Sos2428

Pterodactylus

(no. 57 in the Wellnhofer 1970 catalog)

JME-Sos 2428 in situ —and where are the wing bones??

Tooth number

Ardeadactylus(SMNS-56603, no. 58 in the Wellnhofer 1970 catalog)

(Lateral view below, in situ below far right.)

This tiny specimen phylogenetically nests close to Sos 2428. It shows no sign of wing reduction,

but does have wide gastralia and ribs.

A normal pterosaur wing compared tothe vestigial wing of Sos 2428.

Here the vestigial wing boneshave been segregated from the other very similar rib andpectoral elements after they all have been identi�ed.

Note how small the humerus is.Radius/ulna length estimated.

radius/ulna partly exposed