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New Data on Shenzhoupterus chaoyangensis, 4
an Unusual Lower Cretaceous Pterosaur 5
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David Peters 12
Independent researcher 13
311 Collinsville Avenue, Collinsville, Illinois, U.S.A. 62234 14
314-323-7776 15
davidpeters@att.net 16
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Abstract 18
A recently described specimen of a new genus of pterosaur from the Lower 19
Cretaceous Jiufotang Formation of northeastern China, Shenzhoupterus 20
chaoyangensis, was assigned to the Chaoyangopteridae within the Azhdarchoidea. 21
Originally the posterior skull was traced as an indistinct sheet with only a drop-shaped 22
orbit piercing it at mid-height. That morphology would be atypical for pterosaurs, but 23
a low orbit is found in azhdarchids. A first-hand observation provided new data. Here 24
a new technique, known as Digital Graphic Segregation (DGS), enabled the 25
identification of every bone in the chaotic jumble of the posterior skull and a new 26
reconstruction of the specimen’s “face” in which the orbit was very high on the skull 27
and otherwise more in accord with other pterosaurs. Other purportedly missing 28
elements including the pelvis, prepubis, pteroid and sternal complex were also 29
identified. A new reconstruction of Shenzhoupterus demonstrates very few 30
synapomorphies with Chaoyangopterus, but several with tapejarids and 31
dsungaripterids. 32
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Keywords Azhdarchoidea. Shenzhoupterus. Pterosaur. Lower Cretaceous. China 35
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Introduction 38
Lü et al. (2008) described and named a new genus of pterosaur from the Lower 39
Cretaceous Jiufotang Formation of northeastern China, Shenzhoupterus 40
chaoyangensis (Figs. 1-4). Presently this genus is represented by the holotype, a 41
complete skull and postcranial skeleton (HGM 41HIII-305A, Henan Geological 42
Museum, Zhengzhou, China). Lü et al. (2008) reported, “The skull lies on its right 43
side and is heavily compressed especially the cranium, some elements of which are 44
indistinct and not well preserved, although the orbit and nasoantorbital opening can be 45
identified.” They also reported the spinal column was poorly preserved and indistinct 46
(Fig. 1a). They identified the orbit as, “relatively small, pear-shaped and situated well 47
below the dorsal margin of the nasoantorbital fenestra.” They reported the scapula 48
was longer and more slender than the coracoid and that the deltopectoral crest of the 49
humerus was “markedly elongate.” In the original tracing of these elements (Fig. 1a), 50
the left and right coracoids, scapulae and humeri did not match their counterparts in 51
length, width or overall shape. Lü et al. (2008) did not identify any caudal or pelvic 52
elements and considered the fifth pedal digit absent. 53
Lü et al. (2008) assigned Shenzhoupterus to the Chaoyangopteridae, which 54
they erected within the Azhdarchoidea. According to Lü et al. (2008), “Members of 55
Chaoyangopteridae are distinguished from all other pterosaurs by an unusually 56
slender premaxillary bar bounding the nasoantorbital opening and extension of the 57
nasoantorbital opening posterior to the jaw joint.” Lü et al. (2008) reported that 58
Shenzhoupterus had distinct limb bone proportions from other chaoyangopterids. The 59
rostral index (length of prenarial rostrum to depth) and the concave upper jaw line 60
were also considered distinct. 61
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An examination of the specimen revealed several overlooked elements and 62
some misidentified bones. Here certain errors and omissions were rectified, shedding 63
new light on this unique pterosaur. 64
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Materials and Methods 66
The holotype of Shenzhoupterus was examined first hand in August 2010 in Beijing 67
during the third Flugsaurier Conference. Several digital photographs of the specimen 68
were taken and later opened in Adobe Photoshop (v. 10.0.1, Knoll et al. 2007), a 69
graphics software program. Using the “layers” palette, colors were applied to identify 70
bones (Fig. 1). This technique is called Digital Graphic Segregation (DGS). These 71
layers of color were later traced with black outlines and the outlines were later moved 72
into typical pterosaur positions to create reconstructions (Figs. 2, 3). Nosotti (2007) 73
also used this method to great advantage. 74
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Redescription 76
Lü et al. (2008) accurately described most of Shenzhoupterus. Wherever they had 77
difficulties the new technique was able to segregate and identify tentative, missing 78
and misidentified elements. 79
The posterior of the skull (Fig. 2a) was not a solid sheet of bone pierced only 80
by an orbit (contra Lü, et al. 2008; Fig. 1a, 2c). As would be expected in a crushed 81
pterosaur, both sides of the skull were smashed together along with the overlying 82
occipital elements which all fell onto the bedding plane atop one another. Creating 83
more chaos in the lower cheek area there was an underlying sternal complex (fused 84
sternum plus clavicles plus interclavicle, Fig. 2), which was considered absent 85
originally (Lü, et al. 2008). The jugal was correctly identified in Lü et al. (2008), but 86
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the purported orbit was misidentified with its upper boundary at the displaced 87
foramen magnum. The actual scleral rings were located high on the skull. The actual 88
orbit was an extremely elongated opening bound by extremely slender processes of 89
the jugal and lacrimal (Fig. 2b, 3). This morphology is similar, but not homologous, 90
to the morphology of the Isle of Wight pterosaur, Istiodactylus (Howse, Milner & 91
Martill, 2001). No doubt such a slender morphology was associated with the 92
development of the atypically tall antorbital fenestra. With regard to phylogenetic 93
scoring, such a high orbit would not be considered similar to that of azhdarchids. 94
Lü et al. (2008) failed to note that Shenzhoupterus had a slender elongated 95
premaxilla/frontal crest extending beyond the posterior of the skull, as in 96
dsungaripterids and especially tapejarids. The squamosal created a strong paroccipital 97
process, as in dsungaripterids. The lacrimal sent new processes to the postorbital, 98
dividing the orbit into upper and lower portions, as in dsungaripterids (Figs. 1-3). 99
Lü et al. (2008) failed to note the three anteriormost cervicals were still in 100
articulation with number four near the jaw joint (Fig. 2). The dorsals were not 101
indistinct, but they were all compressed such that the distance between the scapula 102
and ilium had been reduced to half the length of a scapula. Lü et al. (2008) failed to 103
identify the string of tiny caudal vertebrae (Fig. 1) that curled back toward the torso. 104
Lü et al. (2008) correctly identified the scapula and coracoid closest to the 105
body, but reversed the true identities of the more distant scapulocoracoid elements. 106
Here (Fig. 1), both elements are identical in size and shape to their counterparts. Lü et 107
al. (2008) correctly identified the right humerus, but the left humerus is probably 108
hidden beneath the vertebral column. What Lü et al. (2008) identified as the left 109
humerus is actually the much more slender left prepubis, along with the right prepubis 110
behind it, plus a broken rectangular unidentified bone. Lü et al. (2008) failed to 111
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identify a single pteroid, but both are identified here (Fig. 2). A tiny ungual appears 112
just off the tip of the better-preserved fourth wing phalanx (Fig. 4) which is tipped 113
with a trochlear joint. 114
Lü et al. (2008) did not identify the left pelvis and prepubis crushed in place. 115
The pelvis is slender in general morphology with a diverging pubis and ischium. The 116
posterior ilium includes an anterior process. The prepubis is deeper than the pelvis 117
and provided with a distal perforation. 118
In their tracing, Lü et al. (2008) did not attempt to delineate the phalanges or 119
separate one pes from another (Fig. 1a). They described the fifth metatarsal as “short 120
and spur-like” and without any phalanges. Actually the fifth toe is present on both 121
pedes, but it is a slender elongated vestige. Here (Fig. 1d) all the pedal phalanges are 122
identified. 123
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Discussion 125
A reconstruction of Shenzhoupterus (Fig. 3e-i) indicates it was clearly distinct from 126
Chaoyangopterus (Fig. 3a). The antorbital fenestra did not extend posterior to the jaw 127
joint. The orbit was not lower than the upper rim of the antorbital fenestra. Manual 128
and pedal phalangeal patterns were not similar. The sternal complex had a distinct 129
shape in each. A complete phylogenetic analysis is beyond the scope of this short 130
report, but is part of another study currently in review. Shenzhoupterus does share 131
several synapomorphies with tapejarids including a downturned rostrum, elongated 132
posteriorly-directed crest, a square sternal complex, a short deep torso, distinct 133
manual and pedal phalanx proportions and other traits. 134
The technique of using digital images to gather data and trace specimens has 135
been widely employed (e.g. Nosotti 2007) and it was again successful here. The 136
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technique of Digital Graphic Segregation (DGS) enabled the identification of several 137
previously unidentified and misidentified elements that were nearly matched in sister 138
taxa. Lü et al. (2008) were unable to segregate the elements gathered at the face of 139
Shenzhoupterus using visual inspection alone. The visual inspection problem is 140
multiplied in figure 2a by the loss of color and the reduction in resolution that were 141
necessary for publication. Nevertheless, a careful comparison of the map-like tracing 142
in figure 2c with the photo in figure 2a will reveal certain bone outlines that are more 143
prominent than others. The fact that all the bones could be digitally moved into place 144
on the reconstruction and that they all fit together precisely gives certain assurance 145
that the bones were correctly identified. The identification of pelvic, sternal and 146
occipital elements previously ignored or considered missing adds evidence that this 147
was indeed a complete and largely articulated specimen 148
As in any scientific experiment, the method must be followed using the 149
prescribed instrument(s) in order for results to match. One cannot hope to understand 150
microbes without a microscope and stars without a telescope. The chaotic jumble 151
certain parts of this fossil present can only be understood by picking them apart, piece 152
by piece until no pieces are left. This can only be done using a digital image on a 153
computer screen. The human eye was proven to be incapable, as reported by Lü et al. 154
(2008). 155
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Conclusions 157
The specimen of Shenzhoupterus was reexamined and more data was gleaned from 158
the fossil using the technique of Digital Graphic Segregation (DGS). Several bones 159
were newly identified and a few misidentified bones were correctly identified. The 160
bones of the face were resolved and mapped. A sternal complex was discovered 161
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beneath the right cheek. Rather than demonstrating affinities with Chaoyangopterus, 162
Shenzhoupterus shared more synapomorphies with tapejarids and dsungaripterids. 163
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Acknowledgements I thank D. Hone, D. Unwin, and J.-C. Lü for providing access to 165
the holotype of Shenzhoupterus. I wish to thank the editors and reviewers of this 166
manuscript for their careful editing and helpful suggestions. C.-F. Zhou kindly 167
provided the translation of the abstract (here deleted). All errors and omissions are my 168
own. 169
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References 172
Hone D W E, Elgin R A, Frey E, 2010. The extent of the pterosaur flight membrane. 173
Acta Palaeo Pol (in press). doi: 10.4202/app.2009.0145 174
Howse S C B, Milner A R, Martill D M, 2001. Pterosaurs. In: Martill D M, Naish D, 175
eds. Dinosaurs of the Isle of Wight. London: Palaeo Assoc. 324–335 176
Lü J, Unwin D M, Xu L, Zhang X, 2008. A new azhdarchoid pterosaur from the 177
Lower Cretaceous of China and its implications for pterosaur phylogeny and 178
evolution. Naturwissenschaften 95 (9): online (preprint). doi:10.1007/s00114-179
008-0397-5. PMID 18509616. 180
Nosotti S, 2007. Tanystropheus longobardicus (Reptilia, Protorosauria): Re-181
interpretations of the anatomy based on new specimens from the Middle 182
Triassic of Besano (Lombardy, Northern Italy). Mem Soc It Sci Nat Mus Civ 183
Storia Nat Milano 35(3): 1–88. 184
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Figure 1. The holotype of Shenzhoupterus chaoyangensis. A As originally traced in 187
Lü, et al. (2008); B Tracing of the specimen in the present study, certain bones 188
colored for clarity; C Main slab; D Close up of pes; E Tracing of same with 189
elements of left pes colored for clarity. Abbreviations: co coracoid, cr crest, hu 190
humerus, pl pelvis, pp prepubis, pt pteroid, sc scapula, st sternal complex, 1-5 191
pedal digits. Scale bar equals 10 cm. 192
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Figure 2. The “face” of Shenzhoupterus A Close up of the main plate; B Original 195
tracing of Lü et al. (2008). C Tracing of same indicating left side bones only 196
for clarity (except for squamosal and quadrate duplicates); Abbreviations bp 197
basipterygoid, cv 2-4 cervical vertebrae, ep ectopalatine (fused ectopterygoid 198
+ palatine) or possible hyoid, fr frontal, ju jugal, la lacrimal, na nasal, op 199
occipital plate, pa parietal, prf prefrontal, pmx premaxilla, qj quadratojugal, qu 200
quadrate, st sternal complex (in blue), sq squamosal. See figures 1 and 3 for 201
scale. 202
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Figure 3. Reconstructions of Shenzhoupterus and Chaoyangopterus A 206
Chaoyangopterus including alternate views of scapula/coracoid, sternal 207
complex, pelvis and prepubis and right pes; B Relocated bones of 208
Shenzhoupterus moved from the tracing on figure 2 into approximate natural 209
positions as a second step prior to the reconstruction; C sternal complex of 210
same; D pelvis and prepubis of same; E Cleaned up reconstruction of 211
Shenzhoupterus with imagined soft tissues in gray not present in the original 212
specimen; F occipital plate; G scapula and coracoid not foreshortened; H 213
Sternal complex in ventral view; I right pes in dorsal view. Scale bar equals 10 214
cm. 215
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Figure 4. Wing tip of Shenzhoupterus A Close up photo of main slab B Tracing of 218
same Abbreviations ks keratin sheath, m4.4 manual digit four phalanx four, 219
m4.5 wingtip ungual. See figures 1 and 3 for scale. 220
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