| Douzhanopterus | |
|---|---|
 | |
| Photograph of the type specimen ofDouzhanopterus (a) with closeups of the tail (b) and foot (c) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Pterosauria |
| Clade: | †Pterodactyliformes |
| Genus: | †Douzhanopterus Wanget al., 2017 |
| Type species | |
| †Douzhanopterus zhengi Wanget al., 2017 | |
Douzhanopterus is an extinct genus ofmonofenestratanpterosaur from theLate Jurassic ofLiaoning,China. It contains a single species,D. zhengi, named by Wanget al. in 2017. In many respects, it represents atransitional form betweenbasal pterosaurs and the more specializedpterodactyloids; for instance, its tail is intermediate in length, still being about twice the length of thefemur but relatively shorter compared to that of the more basalWukongopteridae. Other intermediate traits include the relative lengths of theneck vertebrae and the retention of two, albeit reduced,phalanx bones in the fifth digit of the foot.Phylogenetically,Douzhanopterus is nested between the wukongopterids andPropterodactylus, which is similar toDouzhanopterus in many respects but approaches pterodactyloids more closely elsewhere.
Theholotype specimen ofDouzhanopterus, a skeleton lacking the skull, is preserved on a plate and counterplate. The plate and counterplate are respectively catalogued as STM 19–35A and STM 19–35B, and they are stored at the Shandong Tianyu Museum of Nature inShandong,China. This specimen was purchased from a local farmer, who claimed that it had been excavated at Toudaoyingzi, Jiangchang inLiaoning province. However, the rock encasing the specimen is characteristic of sediments found at another locality within Liaoning, Linglongta. The latter belongs to the fossil-rich units of theTiaojishan Formation, which have been dated to 160.89 to 160.25 million years ago,[1] or theOxfordian stage of theJurassic period.[2]
In 2017, thetype and only speciesDouzhanopterus zhengi was named and described by Wang Xiaoli, Jiang Shunxing, Zhang Junqiang, Cheng Xin, Yu Xuefeng, Li Yameng, Wei Guangjin and Wang Xiaolin. The generic name combines the nameDòu-zhànshèng-fó (鬥戰勝佛, "Victorious Fighting Buddha"), which was given to the legendarySun Wukong when he attained the status ofBuddha, with the Latinised Greekpteron ("wing"). This is in reference to the animal occupying a more derived position relative to thewukongopterids. Thespecific name honours ProfessorZheng Xiaoting.[2]
Douzhanopterus was a relatively small pterosaur, with a wingspan of only 74 centimetres (29 in). The only known specimen represents an adult, judging by the degree of fusion in the hand bones,scapulocoracoid, and thetibia-fibula, as well as the fusion of the extensor tendon on the wing to the firstphalanx of the wing.[2][3][4]
Out of ninecervical vertebrae,[5] the last seven are definitely preserved, and theatlas andaxis may also be present. These vertebrae are long, generally about 2.5 to 3.5 times as long as they are wide. The vertebrae bear distinctcondyles for articulation with other vertebrae, and theneural spines are directed backwards and upwards; the ones near the middle also have prominentzygapophyses. Further along thevertebral column, there would have been 13dorsal vertebrae in total, followed by sixsacral vertebrae that form asacrum. These two types of vertebrae are similar, although the sideways-projecting transverse processes are more robust in the latter. In the tail were 22 caudal vertebrae, totalling to 83.86 mm (3.302 in) long, which is 173% the length of thehumerus. They increase in length from the first to the sixth but then become smaller after this point. Up until about the sixteenth caudal vertebra, the zygapophyses andchevrons are very long.[2]
Overall, thesternum is about as long as it is wide, with a forward-projecting front margin but a straight back margin. Thescapula is slender and long, being about 40% longer than thecoracoid; the coracoid itself does not bear any sort of expansion on its bottom surface. On the humerus, the deltopectoral crest is short and trapezoidal, and is placed at the top of the bone. A small crest is also present where the humerus articulates with theulna. Thepteroid, a bone unique to pterosaurs, is quite long, being about half as long as the ulna. In front of the pteroid, there is a smallsesamoid bone that is attached to the outer edge of thecarpals. The digits of the non-wing hand are somewhat long, being about 65% of humerus length and 53% of ulna length, and bear large claws. On the wing finger, the second phalanx is the longest, followed by the first and third, and then the fourth, which is still about 80% the length of the second.[2]
Fused entirely to the sacrum is thepelvic girdle. The portion of the pelvic girdle in front of thefemoral joint appears to consist of two unfused prepubes, which are longer than they are wide. Thefemur is slightly curved, and thefemoral head and neck form an angle of about 150° with the shaft. On the lower leg, the relatively straighttibia is about 180% the length of the femur; thefibula, which is about 45% the length of the tibia, is fused to it at both ends. Further below, the fivemetatarsals are rectangular. The second metatarsal is also the longest, followed again by the first and third, and then the fourth, with the third metatarsal being about 31% the length of the tibia. Unusually, the fifth digit of the foot still has two phalanges, the first straight and the second curved; the first is about 20% the length of the third metatarsal.[2]
In 2017, Wanget al. assignedDouzhanopterus to theMonofenestrata.Douzhanopterus exhibits a number of characteristics that are intermediate between morebasal pterosaurs, including theWukongopteridae,[6][7][8][9] and the more derivedPterodactyloidea. In particular, the cervical vertebrae are generally longer; the tail is less than half of body length but still not particularly reduced; themetacarpals are moderately long compared to thehumerus andulna; and the fifth digit of the foot still bears twophalanges, although they are reduced with respect to basal pterosaurs but still larger than pterodactyloids. Its position in thephylogenetic tree recovered by Wanget al., the topology of which is partially reproduced below, is consistent with its intermediate condition.[2]
| Monofenestrata |
| ||||||||||||||||||||||||||||||
More derived thanDouzhanopterus is the "Painten pro-pterodactyloid", known from a juvenile specimen (later formally namedPropterodactylus[10]) from theKimmeridgian ofGermany.[11] They share a long fourth metacarpal, relatively reduced phalanges of the fifth digit on the foot, and a reduced but still relatively long tail with longzygapophyses andchevrons. However, several characteristics indicate thatDouzhanopterus is still more basal: thepteroid is larger relative to the ulna, thetibia is much longer than the femur, the tail is longer both absolutely (22 vertebrate and longer than the femur, as opposed to the 17 in the Painten specimen) and relative to the humerus, and the zygapophyses and chevrons are slightly longer.[11] These differences are probably not related to the young age of the Painten specimen, based on studies of unpublished juvenile monofenestratan specimens.[2]
