Genus of monofenestratan pterosaur from the Late Jurassic
Douzhanopterus
is an extinct genus of
monofenestratan
pterosaur
from the
Late Jurassic
of
Liaoning
,
China
. It contains a single species,
D. zhengi
, named by Wang
et al.
in 2017. In many respects, it represents a
transitional form
between
basal
pterosaurs and the more specialized
pterodactyloids
; for instance, its tail is intermediate in length, still being about twice the length of the
femur
but relatively shorter compared to that of the more basal
Wukongopteridae
. Other intermediate traits include the relative lengths of the
neck vertebrae
and the retention of two, albeit reduced,
phalanx bones
in the fifth digit of the foot.
Phylogenetically
,
Douzhanopterus
is nested between the wukongopterids and a juvenile pterosaur specimen from Germany known as the "Painten pro-pterodactyloid", which is similar to
Douzhanopterus
in many respects but approaches pterodactyloids more closely elsewhere.
Discovery and naming
[
edit
]
The
holotype
specimen of
Douzhanopterus
, 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 in
Shandong
,
China
. This specimen was purchased from a local farmer, who claimed that it had been excavated at Toudaoyingzi, Jiangchang in
Liaoning
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 the
Tiaojishan Formation
, which have been dated to 160.89 to 160.25 million years ago,
[1]
or the
Oxfordian stage
of the
Jurassic
period.
[2]
In 2017, the
type
and only species
Douzhanopterus 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 name
Dou-zhansheng-fo
(?戰勝佛, "Victorious Fighting Buddha"), which was given to the legendary
Sun Wukong
when he attained the status of
Buddha
, with the Latinised Greek
pteron
("wing"). This is in reference to the animal occupying a more derived position relative to the
wukongopterids
. The
specific name
honours Professor
Zheng Xiaoting
.
[2]
Description
[
edit
]
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 the
tibia
-
fibula
, as well as the fusion of the extensor tendon on the wing to the first
phalanx
of the wing.
[2]
[3]
[4]
Out of nine
cervical vertebrae
,
[5]
the last seven are definitely preserved, and the
atlas
and
axis
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 distinct
condyles
for articulation with other vertebrae, and the
neural spines
are directed backwards and upwards; the ones near the middle also have prominent
zygapophyses
. Further along the
vertebral column
, there would have been 13
dorsal vertebrae
in total, followed by six
sacral vertebrae
that form a
sacrum
. 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 the
humerus
. 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 and
chevrons
are very long.
[2]
Overall, the
sternum
is about as long as it is wide, with a forward-projecting front margin but a straight back margin. The
scapula
is slender and long, being about 40% longer than the
coracoid
; 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 the
ulna
. The
pteroid
, a bone unique to pterosaurs, is quite long, being about half as long as the ulna. In front of the pteroid, there is a small
sesamoid bone
that is attached to the outer edge of the
carpals
. 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 the
pelvic girdle
. The portion of the pelvic girdle in front of the
femoral joint
appears to consist of two unfused prepubes, which are longer than they are wide. The
femur
is slightly curved, and the
femoral head
and neck form an angle of about 150° with the shaft. On the lower leg, the relatively straight
tibia
is about 180% the length of the femur; the
fibula
, which is about 45% the length of the tibia, is fused to it at both ends. Further below, the five
metatarsals
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]
Classification
[
edit
]
In 2017, Wang
et al.
assigned
Douzhanopterus
to the
Monofenestrata
.
Douzhanopterus
exhibits a number of characteristics that are intermediate between more
basal
pterosaurs, including the
Wukongopteridae
,
[6]
[7]
[8]
[9]
and the more derived
Pterodactyloidea
. In particular, the cervical vertebrae are generally longer; the tail is less than half of body length but still not particularly reduced; the
metacarpals
are moderately long compared to the
humerus
and
ulna
; and the fifth digit of the foot still bears two
phalanges
, although they are reduced with respect to basal pterosaurs but still larger than pterodactyloids. Its position in the
phylogenetic tree
recovered by Wang
et al.
, the topology of which is partially reproduced below, is consistent with its intermediate condition.
[2]
More derived than
Douzhanopterus
is the "Painten pro-pterodactyloid", an unnamed juvenile specimen from the
Kimmeridgian
of
Germany
.
[10]
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 long
zygapophyses
and
chevrons
. However, several characteristics indicate that
Douzhanopterus
is still more basal: the
pteroid
is larger relative to the ulna, the
tibia
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.
[10]
These differences are probably not related to the young age of the Painten specimen, based on studies of unpublished juvenile monofenestratan specimens.
[2]
References
[
edit
]
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