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634
ISSN 0031-0301, Paleontological Journal, 2008, Vol. 42, No. 6, pp. 634–642. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.O. Averianov, M.S. Arkhangelsky, E.M. Pervushov, 2008, published in Paleontologicheskii Zhurnal, 2008, No. 6, pp. 61–68.
INTRODUCTION
Several localities of Campanian vertebrates, con-
taining azhdarchid pterosaurs and hesperornithid birds,
have recently been discovered in the Volga Region near
Saratov (Fig. 1; Panteleyev et al., 2004; Averianov
et al., 2005; Averianov, 2007). It is noteworthy that, in
the localities with hesperornithids (Karyakino in the
Saratov Region and Rychkovo in the Volgograd
Region; the last locality was described by Nessov and
Yarkov (1993) and Yarkov and Nessov (2000)), ptero-
saurs are extremely infrequent and represented by inde-
terminable fragments of large tubular bones. On the
contrary, in the localities with identifiable azhdarchid
bones (Malaya Serdoba, Shirokii Karamysh 2, Beloe
Lake, Saratov 2), hesperornithid bones have not yet
been recorded. The difference in occurrence of azh-
darchids and hesperornithids is probably attributable to
different paleoenvironments and competitive relation-
ships between the two groups of specialized ichthyoph-
agous vertebrates. In the present study, pterosaur bones
from the Shirokii Karamysh 2 locality of the Saratov
Region, which were collected in 2004 and 2005 by the
Saratov amateur collectors M.A. Grigor’ev, A.L. Gor-
bunov-Gusev, and A.N. Gurenko and assigned to a new
azhdarchid taxon, are described.
Abbreviations: (SGU) Saratov State University,
Saratov, Russia; (ZIN PH) paleoherpetological collec-
tion of the Zoological Institute of the Russian Academy
of Sciences, St. Petersburg.
GEOLOGICAL AND TAPHONOMIC
CHARACTERISTICS OF THE SHIROKII
KARAMYSH 2 LOCALITY
The Shirokii Karamysh 2 locality is situated in the
upper part of the Lisii gully north of the village of Shi-
rokii Karamysh at the road to the village of Uritskoe
(Lysogorskii District, Saratov Region). This is the sec-
ond gully from the northern boundary of the village, the
upper part of which cuts a slope of erosion terrace.
The gully opens the following section of Upper Cre-
taceous deposits, described downward the section:
K
2
Cmp
2
, Bed 1. Greenish gray, glauconitic quartz,
inequigranular sandstone, spotty because of nonuni-
form siliceous cement, solid, furrowed by surface
weathering. The horizon gradually passes into the
underlying strata, with the transition marked by a pro-
jection of denser sandstones in the slope of the gully.
The lower surface is uneven. Thickness, up to 0.5 m.
K
2
Cmp
1–2
, Bed 2. Phosphorite horizon: the upper
part is composed of bright green, quartz–glauconitic,
strongly bioturbinated sand, with phosphorites up to
0.5–1 cm in size, regularly scattered and slightly accu-
mulated in the roof. In the lower part, phosphorites are
dark brown, black, sabulous, and angular and black,
more rounded. Phosphorites and phosphorite accumu-
lations are abundant. In places, phosphorite inclusions
are widely spaced; in some sites (up to 1.5–2.5 m in
size), they are accumulated, smaller in size, 1–1.5 cm in
diameter. The grayish yellow and grayish brown aleu-
ritic inclusions are more rounded, with signs of bioero-
sion, more widely spaced and mostly smaller in size.
The lower surface is uneven, pitted and nest-shaped.
A New Late Cretaceous Azhdarchid (Pterosauria, Azhdarchidae)
from the Volga Region
A. O. Averianov
a
, M. S. Arkhangelsky
b
, and E. M. Pervushov
b
a
Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg, 199034 Russia
e-mail: lepus@zin.ru
b
Geological Faculty, Saratov State University, Astrakhanskaya ul. 83, Saratov, 410026 Russia
e-mail: paleozoo@gmail.com
Received June 29, 2007
Abstract
—A new azhdarchid genus and species,
Volgadraco bogolubovi
gen. et sp. nov., is described based on
an anterior fragment of the mandibular symphysis (mandibular beak) and some postcranial elements from the
Rybushka Formation (Upper Cretaceous, Lower Campanian) of the Shirokii Karamysh 2 locality, Saratov
Region. The new taxon is intermediate in size and vascularization of the mandibular beak between medium-
sized Turonian–Santonian azhdarchids (
Azhdarcho, Bakonydraco
) and the giant Maastrichtian azhdarchid
Quetzalcoatlus
.
DOI:
10.1134/S0031030108060099
Key words
: Pterosauria, Azhdarchidae, new taxa, Cretaceous, Saratov Region, Russia.
PALEONTOLOGICAL JOURNAL
Vol. 42
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2008
A NEW LATE CRETACEOUS AZHDARCHID (PTEROSAURIA, AZHDARCHIDAE) 635
The accumulations of phosphorite inclusions at the
lower boundary are up to 0.1 m thick. This layer con-
tained isolated, frequently well-preserved specimens of
marine reptiles (Elasmosauridae indet., Polycotylidae
indet.,
Prognathodon
sp., and
?Clidastes
sp.). Ptero-
saur bones come from this layer. Thickness, 0.4–0.5 m.
K
2
Cmp
1
, Bed 3. Dirty green, nonuniformly colored,
quartz–glauconitic sand, strongly bioturbinated; bur-
rows up to 1.5–5 cm in diameter extend to a depth of
0.5–0.6 m from the roof. This layer contains small, iso-
lated subovate aleuritic inclusions, strongly rounded
and, sometimes, positioned vertically (up to 2 cm in
diameter). Near the roof, narrow (1–2 mm in diameter)
and short (up to 1–3 cm) burrows are sporadically dis-
tributed. Below, the sand is uniformly grayish green,
medium-grained; signs of bioturbidites are almost
absent, which explains the abundance of poorly phos-
phatized biogenic remains preserved in these strata.
Fossils are mostly represented by fish scales, which are
accumulated in nests and lower parts of decapod bur-
rows (in the upper part of the horizon); coprolites, bur-
ied subautochthonously (scattered at a distance of 1 m);
fish vertebrae; teeth and dental plates of cartilaginous
fish; and small phosphate mollusk shells, buried in dif-
ferent positions.
At 1.3–1.5 m below the roof of sand, there is a layer
containing infrequent, variously oriented aleuritic pel-
lets and shingles, rare nests (up to 0.1 m in diameter) of
accumulated phosphate pellets. Below this level, faunal
remains are scarce. Visible thickness, 1.9 m.
Vertebrates occur in the phosphorite horizon. The
bones are dirty yellow, strongly phosphatized, very
dense, slightly rounded, exposed to bioerosion,
diversely oriented. Tetrapods were buried within an
active sublittoral zone, under conditions of general
immersion of the territory; this provided rather exten-
sive accumulation of terrigenous material, psammitic
and aleuritic matter. As a result of movements within
the sublittoral and supralittoral zones, a sandy–pebble
beach was formed from time to time, where large ele-
ments of the substrate were phosphorite pellets, verte-
bral centers, and other reptile bones. The subsidence,
short-term of exposure on the surface, and the rapid fos-
silization (phosphatization) provided good primary
preservation of many bones. In some cases, long, nar-
row bones and vertebral centers in natural articulation
with neural spines are preserved, while large vertebral
centers of plesiosaurs are usually most rounded and dam-
aged. The presence within a locality of some bones
undoubtedly belonging to the same individual (vertebral
centers, teeth of fish, etc.) suggests slight scattering of
dead bodies and body fragments, in particular, primary
burial not influenced by active hydrodynamic factors.
In general, the burial of marine and subcontinental
vertebrates in Bed 2 should be classified as synchro-
nous, tabular, nonuniformly scattered.
A distinctive feature of this locality is the fact that,
during the short period of the formation of the phospho-
rite horizon, erosion had a minor effect on underlying
sands rich in invertebrate and vertebrate remains (see
description of Bed 3). The development of diverse dig-
ging organisms, which resulted in almost complete dis-
appearance of biogenic inclusions in the upper part of
the early deposits, resulted in the stratification and pres-
ervation of autochthonous and subautochthonous buri-
als of vertebrates and mollusks. As is usually observed
in the majority of localities with similar stratification,
the upper part of Bed 3 is eroded and elements of this
bed occur in the overlying phosphorite horizon. These
results of comparative analysis of a number of rela-
tively synchronous localities (Campanian units) sug-
gest a relatively low position (hypsometric) of the area
of the Shirokii Karamysh 2 locality in the time of the
formation of terrigenous deposits and, in particular, of
the phosphorite horizon.
The distribution of pterosaurs and birds (hesperorni-
thids) in the Late Cretaceous of the southeastern Euro-
pean paleobiogeographic region was connected with
the history of the formation and arrangement of subflat
islands of archipelagoes and banks in this region.
Within a relatively shallow area between the Voronezh
Region on the west and an extensive marine basin in the
Recent Caspian Region, local positive elements reflect-
ing a block structure of the base and composing com-
plex systems in the shape of swells were formed for a
long time. Changes in both the geodynamic mode and
the level of basins in this area had an effect on the man-
70 km3503570
Ulyanovsk
Syzran
Samara
Khvalynsk
Vol’sk
Ershov
Petrovsk
Atkarsk
Saratov
Penza
Elan’
Kamyshin
Rovnoe
KAZAKHSTAN
Volga R
.
1
2
3
4
5
Kalininsk
Balakovo
Fig. 1.
Localities of pterosaurs and birds in the Campanian
of the Saratov and Penza regions: (
1
) Malaya Serdoba,
(
2
) Karyakino, (
3
) Shirokii Karamysh, (
4
) Beloe Lake, and
(
5
) Saratov.
636
PALEONTOLOGICAL JOURNAL
Vol. 42
No. 6
2008
AVERIANOV et al.
ifestation of these positive structures on the bottom of
the basin, including a series of archipelagoes.
Pterosaur and avian records occur mostly in the area
of the former banks and islands in the southern and cen-
tral parts of the right bank of the Volga Region and have
not yet been recorded to the north of the latitude of the
town of Serdobsk (Penza Region).
The Shirokii Karamysh 2 locality is a series of sites
of this type in the middle zone on the right bank of the
Volga Region, which differs from sites in the adjacent
area in the more abundant vertebrate specimens; this is
accounted for by concurrence of a number of factors:
(1) The presence of many islands in a large part of
the right bank of the Volga Region (from the latitude of
Volgograd to the latitude of Saratov), which allowed
sublatitudinal and submeridional migration of ptero-
saurs and birds.
(2) Long-term existence of many islands, including
elevations (Uritskoe and Shirokii Karamysh), a slope of
which retained the locality under study.
(3) The wide zone of the sublittoral and supralit-
toral, the gently sloping shore, and warmed water pro-
vided abundant food.
(4) Currents in the basin and seasonal movements of
water masses developed within certain periods stable
routes of migration of marine organisms between
islands. This provided habitats and migration patterns
of pterosaurs and birds within the coastal zone near the
migration routes of fish and other marine organisms.
SYSTEMATIC PALEONTOLOGY
Superorder Pterosauria
Order Pterodactylida
Superfamily Azhdarchoidea Nessov, 1984
Family Azhdarchidae Nessov, 1984
Genus
Volgadraco
Averianov,
Arkhangelsky et Pervushov, gen. nov.
Etymology. From the Volga River and the Latin
draco
(dragon).
Type species.
Volgadraco bogolubovi
sp. nov.
Diagnosis. Mandibular beak long, with slightly
convex lateral outline of dorsal margin. Dorsal surface
of mandibular beak concave between sharpened lateral
edges. Vascularization of mandibular beak reduced to
three irregular foramina on each side. Cervical vertebra 3
with anteriorly high neural arch, large central pneu-
matic foramen above spinal canal on anterior side, and
with series of small pneumatic foramina in lateral sur-
face. Cervical vertebra 9 with large hypapophysis and
large slitlike depression on lateral surface of neural arch
just anterior to postzygapophysis. Last vertebra of
notarium with slitlike, dorsoventrally compressed fora-
men of spinal canal. Lesser trochanter of femur weakly
developed.
Species composition. Type species.
Comparison. The new genus differs from
Azhdarcho
Nessov, 1984 from the Turonian of Uzbeki-
stan in the longer mandibular beak, with the less convex
lateral outline of the dorsal margin; in the fewer foram-
ina for blood vessels in the mandibular beak; the higher
neural arch of cervical vertebra 3 on the anterior side,
the large central pneumatic foramen above the spinal
canal and a series of small pneumatic foramina on the
lateral surface of this vertebra; in the larger hypapophy-
sis and the greater volume of the slitlike depression on
the lateral surface of the neural arch just anterior to the
postzygapophysis of cervical vertebra 9; and in the
weaker developed lesser trochanter of the femur.
It differs from
Eoazhdarcho
Lü et Ji, 2005 from the
Aptian of China in the longer mandibular beak.
It differs from
Bennettazhia
Nessov, 1991 from the
Albian of the United States in the slitlike, dorsoven-
trally compressed foramen of the spinal canal of the last
thoracic vertebra of the notarium.
It differs from
Bakonydraco
Ösi, Weishampel et
Jianu, 2005 from the Santonian of Hungary in the
longer and less massive mandibular beak with a convex
lateral outline of the dorsal margin (in
Bakonydraco
,
this margin is posteriorly concave and anteriorly con-
vex) and the fewer slitlike foramina for blood vessels in
the mandibular beak.
It differs from
Aralazhdarcho
Averianov, 2007 from
the Santonian–Campanian of Kazakhstan in the less
developed lesser trochanter of the femur.
It differs from
Zhejiangopterus
Cai et Wei, 1994
from the Campanian of China in the convex rather than
concave lateral structure of the dorsal margin and the
concave rather than flat dorsal surface of the mandibu-
lar beak.
It differs from
Phosphatodraco
Pereda Suberbiola
et al., 2003 from the Maastrichtian of Morocco in the
larger foramen of the spinal canal on cervical vertebra 9.
It differs from
Quetzalcoatlus
Lawson, 1975 from
the Maastrichtian of the United States in the shorter and
more massive mandibular beak; the concave rather than
flat dorsal surface of the mandibular beak; the presence
of slitlike foramina for blood vessels in the mandibular
beak; the better developed hypapophysis of cervical
vertebra 9; and in the presence of a large slitlike depres-
sion on the lateral surface of the neural arch of this ver-
tebra just anterior to the postzygapophysis.
Remarks. It is impossible to compare the new
genus with
Montanazhdarcho
Padian et al., 1995
(Campanian of the United States),
Bogolubovia
Nessov, 1989 (Campanian of Russia),
Arambourgiania
Nessov, 1987 (Maastrichtian of Jordan), and
Hatzegop-
teryx
Buffetaut et al., 2002 (Maastrichtian of Romania)
because of incomparability of available material.
It is not improbable that the genus described is a jun-
ior synonym of
Bogolubovia
Nessov, 1989, which is
represented by a fragment of a middle cervical vertebra
and, probably, by some other bones from the Rybushka
PALEONTOLOGICAL JOURNAL
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A NEW LATE CRETACEOUS AZHDARCHID (PTEROSAURIA, AZHDARCHIDAE) 637
Formation near the village of Malaya Serdoba in the
Penza Region (Bogolyubov, 1914; Averianov, 2007).
Bakhurina and Unwin (1995) and Unwin and Bakhu-
rina (2000) designated this taxon as a nomen dubium;
we tentatively adhere to this point of view and, hence,
describe the new azhdarchid from the Campanian of the
Volga Region based on the better identifiable material.
If more complete skeletal material combining charac-
ters of
Bogolubovia
and
Volgadraco
gen. nov. are
found, the first name should be restored according to
the principle of priority and the second name should be
regarded as a junior subjective synonym. At the same
time, it is possible that several azhdarchid genera
existed in the Campanian of the Volga Region.
The assignment of isolated and noncomparable
skeletal elements from one locality to the same taxon is
always tentative, because it is impossible to exclude the
presence of two or more closely related taxa in the same
assemblage. To overcome this obstacle a new taxon is
sometimes based only on the holotype, while other
skeletal elements are not included in the same taxon.
For example,
Bakonydraco galaczi
Ösi, Weishampel et
Jianu, 2005 from the Santonian of Hungary is only
based on the holotype (lower jaw), whereas accompa-
nying postcranial azhdarchid bones from this locality
are determined as Azhdarchidae indet. (Ösi et al.,
2005). However, from the taxonomic point of view, this
conclusion means the presence of two azhdarchid
taxa in the assemblage,
Bakonydraco galaczi
and
Azhdarchidae indet. We are inclined to assign all spec-
imens of a medium-sized azhdarchid from the Shirokii
Karamysh 2 locality to the same taxon,
Volgadraco
bogolubovi
sp. nov., until the presence of other azh-
darchid taxa in this assemblage is shown with certainty.
Volgadraco bogolubovi
Averianov, Arkhangelsky et Pervushov, sp. nov.
Plates 5 and 6
Azhdarchidae indet.: Averianov, 2007, p. 76.
Etymology. The species is named in honor of
N.N. Bogolyubov, who described the first pterosaur
from Russia, which was the first representative of the
family Azhdarchidae known to science (Bogolyubov,
1914).
Holotype. SGU, no. 46/104a, anterior part of the
lower jaw symphysis (mandibular beak); Russia, Sara-
tov Region, Shirokii Karamysh 2 locality; Upper Creta-
ceous, Lower Campanian, phosphorite conglomerate of
the Rybushka Formation.
Description. The mandibular beak (holotype,
Pl. 5, fig. 1) is triangular in lateral, dorsal, and ventral
views. The dorsal and ventral surfaces are positioned at
an angle of approximately 13c and the lateral surfaces
are at an angle of approximately 4
°
, forming a pointed
end of the beak (the tip of which is broken off). In lat-
eral view, the outline of the dorsal surface is slightly
convex, almost straight. On the dorsal surface, the lat-
eral margins form sharp elevated margins, with a
slightly concave area between them. The lateral sur-
faces of the beak are convex in the dorsal part and
almost straight in the ventral part; converge ventrally at
an angle of approximately 37
°
, forming a sharp ventral
crest along the entire beak. In the anterior part, the beak
is almost rhomboidal in cross section, with lateral keels
near the midheight of the beak. The ventral margin is
straight in lateral view. A few slitlike foramina for
blood vessels (three on each lateral and dorsal sides) are
arranged irregularly.
The third cervical vertebra is almost completely pre-
served (specimen SGU, no. 47/104a; Pl. 5, fig. 2). The
vertebral center is relatively short; its length is only
2.4 times as great as the minimum diameter at the cen-
ter. The lateral sides of the vertebral center are concave,
so that, in ventral view, it is in the shape of a sand-glass.
The ventral side of the vertebral center is strongly con-
vex in the central part. The anterior side has a short
crest of the hypapophysis. The posterior part of the ven-
tral surface of the vertebral center is flat; laterally, it is
limited by weak crests extending from the postexapo-
physes to the center of the ventral surface. The anterior
articular depression of the vertebral center is wide and
relatively low, it is three times as wide as high. The dor-
sal surface of the depression is convex, with a small
concavity at the center. The ventral surface is divided
by the hypapophysis into two concave parts. The ven-
trally curved lateral margins of the anterior articular
depression correspond to rudimentary parapophyses
separated by a wide groove from rudimentary diapo-
physes on the neural arch. The posterior condyle of the
vertebral center is ovate, compressed strongly dors-
oventrally, 3.6 times as wide as high. The ventral mar-
gin of the condyle is at a distance from the ventral mar-
gin of the vertebral center that is greater than the
condyle height. This interval is occupied by a shallow
depression restricted on the sides by the crests extend-
ing from the condyle to the postexapophyses. The pos-
texapophyses are stout, ventrolaterally oriented. The
lateral sides of the vertebra have a series of small irreg-
ular depressions (four on the right and three on the left)
at the boundary between the neural arch and the center.
Some depressions (two on the right and, probably, one
on the left) contain small pneumatic foramina. Dor-
sally, a prominent crest extends along the entire neural
arch, connecting the prezygapophysis and the postzyg-
apophysis (it corresponds to the parasagittal carina of
succeeding cervical vertebrae). This crest is positioned
at an angle of approximately 15
°
to the anteroposterior
axis of the vertebral center. Anteriorly, the neural arch
is relatively high, higher than the anterior articular
depression. The spinal canal is very small, rounded in
cross section. The oval pneumatic foramen, which is
only slightly smaller than the spinal canal, is positioned
somewhat dorsally. On each side of the foramina
described, there is an extensive triangular depression,
which is restricted ventrally by the vertebral center and
dorsolaterally by sharp crests extending from the
prezygapophyses to the base of the neural spine. This
region is either damaged (on the left side) or covered
638
PALEONTOLOGICAL JOURNAL
Vol. 42
No. 6
2008
AVERIANOV et al.
Plate 5
1‡
1b
1d
1c
prz
nsp
pf
nc
di
su
pa
ct
hy
prz
prz
pa
pf
hy
nc
ct
hy
prz
3‡
3b
nsp
2c
cn
pe
nsp
prz
fd
poz
od
nc
di
pa
cn
3d
di
pa
cn
2e
2b
2‡
pf
nsp
pf
poz
nc
pe
hy
poz
cn
pe
cn
nsp
2d
3e
3c
PALEONTOLOGICAL JOURNAL
Vol. 42
No. 6
2008
A NEW LATE CRETACEOUS AZHDARCHID (PTEROSAURIA, AZHDARCHIDAE) 639
with phosphorite (on the right); therefore, it remains
uncertain whether or not the lateral pneumatic canals,
which have foramina on the posterior side of the neural
arch, open here. The prezygapophysis is massive, with
a convex ovate articular surface oriented dorsally and
slightly anteriorly. On the posterior side of the neural
arch, the foramen of the spinal canal is larger than on
the anterior side. This foramen is ovate, except for the
ventral border, which is straight and coincides with the
dorsal border of the posterior condyle. On the sides and
somewhat dorsally, there are large foramina of the lat-
eral pneumatic canals. The dorsal (central) pneumatic
foramen is absent from the posterior side. A massive
horizontal crest passes above the foramina, connecting
the postzygapophyses. The central vertical crest, which
forms the posterior margin of the neural spine, is
located more dorsally. The postzygapophyses are
mostly damaged. The articular surface of the postzyga-
pophysis (partially preserved on the left side) is con-
cave, oriented ventrally and slightly posteriorly. The
neural spine is relatively high; its base occupies the
entire extent of the neural arch. The maximum height of
the neural spine is probably close to the posterior mar-
gin, in line with the base of the postzygapophyseal pro-
cesses. At the same point, the neural spine shows the
maximum width, which is almost three times as wide as
near the anterior margin.
The ninth (last) cervical vertebra (specimen SGU,
no. 48/104a; Pl. 5, fig. 3) is also almost completely pre-
served. The vertebra is high and very short anteroposte-
riorly. On the vertebral center, the anterior articular sur-
face is strongly concave and the posterior condyle is
strongly convex. The hypapophysis is well developed,
approximately to the same extent as in the third cervical
vertebra (in cervical vertebra 9 of
Azhdarcho
and
Quetzalcoatlus
, it is strongly reduced). The surface of
the posterior condyle is damaged; the concave lateral
surfaces of this condyle, if present, were probably
developed to a much lesser extent than in
Azhdarcho
and
Quetzalcoatlus
. The ventral surface of the vertebral
center is slightly convex (in
Azhdarcho
and
Quetzal-
coatlus
, it is flat). The foramen of the spinal canal is rel-
atively large, ovate, its ventral border is straight anteri-
orly and convex posteriorly. The lateral pneumatic
foramina were probably present anteriorly (this area of
the vertebra is covered with phosphorites). The neural
arch is high, with a longitudinal central crest located
anteriorly. A pair of transverse depressions extend
between this crest and prezygapophyses (
Azhdarcho
and
Quetzalcoatlus
lack similar depressions). The artic-
ular surfaces of the prezygapophyses and postzygapo-
physes are not preserved. On the lateral surface of the
vertebra at the boundary between the vertebral center
and neural arch, there is the base of a massive diapo-
physis (most of the process is broken off), which is
divided by a wide groove of a relatively small parapo-
physis. A large slitlike depression is located just ante-
rior to the base of the postzygapophysis (in
Azhdarcho
,
this depression is very small; in
Quetzalcoatlus
, it is
absent). A very large ovate, dorsoventrally extended
depression is located above the postzygapophyses. The
same depression is present in cervical vertebra 9 of
Quetzalcoatlus, Phosphatodraco
, and
Pteranodon
(Bennett, 2001, text-fig. 42B; Pereda Suberbiola et al.,
2003, text-fig. 3e); the structure of this region in
Azh-
darcho
is not known. The neural spine is not preserved;
its base is short and wide, located close to the center of
the neural arch.
The material includes a posterior fragment of the
notarium, consisting of four fused dorsal vertebrae
(specimen SGU, no. 49/104a; Pl. 6, fig. 1). In this frag-
ment, the suture between the first and second vertebral
centers is hardly discernible. The ventral side of the
vertebral center is more concave in two posterior verte-
brae than in two anterior vertebrae. The posterior
condyle of the center of the last vertebra is strongly
convex, ovate (the transverse diameter exceeds the
height). The dorsal border of the condyle is concave,
forming the bottom of the spinal canal. The foramen of
the spinal canal is slitlike, compressed dorsoventrally to
a greater extent than in
Azhdarcho
(in
Bennettazhia
, it
is ovate and higher).
A fragment of a long tubular bone (specimen SGU,
no. 50/104a; Pl. 6, fig. 2) is most likely a part of the dia-
physis of the first phalanx of the wing (fourth) digit.
The diaphysis is ovate in cross section; the anteroposte-
rior diameter is 1.6 times as long as the dorsoventral
diameter (in
Azhdarcho lancicollis
, specimen ZIN PH,
no. 37/44, it is two times as long). The anteroposterior
diameter is uniform throughout the fragment preserved;
this is evidence that the bone was long.
The femur (specimen SGU, no. 50/104a; Pl. 6, fig. 3)
is only represented by the diaphysis. The bone is hol-
low, thin-walled and relatively large; the total length
was probably at least 17 or 18 cm. The diaphysis is
strongly curved in the frontal plane. This curvature is
Explanation of Plate 5
Figs. 1–3.
The pterosaur
Volgadraco bogolubovi
sp. nov. from the Rybushka Formation (Lower Campanian) of the Shirokii
Karamysh 2 locality, Saratov Region, Russia: (1) holotype SGU, no. 46/104a, anterior part of the mandibular beak: (1a) dorsal,
(1b) lateral, (1c) ventral, and (1d) proximal views,
×
1.30; arrows indicate slitlike foramina for blood vessels; (2) SGU, no. 47/104a,
cervical vertebra 3: (2a) anterior, (2b) lateral, (2c) ventral, (2d) posterior, and (2e) dorsal views,
×
0.69; (3) SGU, no. 48/104a, cer-
vical vertebra 9: (3a) anterior, (3b) dorsal, (3c) lateral, (3d), posterior, and (3e) ventral views,
×
1.10. Designations: (
cn
) posterior
condyles of the vertebral center, (
ct
) anterior articular depression of the vertebral center, (
di
) diapophysis, (
fd
) slitlike depression,
(
hy
) hypapophysis, (
nc
) foramen of the spinal canal, (
nsp
) neural spine, (od) oval depression, (pa) parapophysis, (pe) postexapo-
physis, (pf) pneumatic foramen, (poz) postzygapophysis, (prz) prezygapophysis, and (su) sulcus between the parapophysis and
diapophysis.
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PALEONTOLOGICAL JOURNAL Vol. 42 No. 6 2008
AVERIANOV et al.
Plate 6
spnf
nc
cn
lt
1‡
1b
2‡
1c
3‡
3b
2b
Explanation of Plate 6
Figs. 1–3. The pterosaur Volgadraco bogolubovi sp. nov. from the Rybushka Formation (Lower Campanian) of the Shirokii
Karamysh 2 locality, Saratov Region, Russia: (1) SGU, no. 49/104a, posterior part of the notarium, consisting of four thoracic ver-
tebrae: (1a) lateral, (1b) posterior, and (1c) ventral views ×1.50; (2) SGU, no. 51/104a, fragment of the presumably first right pha-
lanx of the wing digit: (2a) proximal (?) view and (2b) dorsal or ventral view, ×1.28; (3) SGU, no. 50/104a, left femur fragment:
(3a) posterior and (3b) anterior views, ×0.95. Designations: (cn) posterior condyles of the vertebral center, (lt) small trochanter,
(nc) foramen of the spinal canal, and (spnf) foramen of the spinal nerve.
much more pronounced than in the femoral diaphysis
of giant Quetzalcoatlus sp. from the Campanian of
Alberta, Canada (Currie and Russell, 1982, text-fig. 1)
and approximately equal to that of the significantly
smaller Azhdarcho lancicollis (specimen ZIN PH,
no. 44). The diaphysis is ovate in cross section. The
proximal end is broken off at the base of the greater tro-
chanter. A very small rough area of the lesser trochanter
PALEONTOLOGICAL JOURNAL Vol. 42 No. 6 2008
A NEW LATE CRETACEOUS AZHDARCHID (PTEROSAURIA, AZHDARCHIDAE) 641
for the iliofemoralis internus muscle is located on the
anterior side, near the proximal margin preserved,
closer to the dorsal margin. The lesser trochanter is
much weaker than in Azhdarcho and Aralazhdarcho
(Averianov, 2007).
Remarks. The symphysis of the dentaries of
azhdarchids, which is up to 60% of the lower jaw
length, consists of two distinctly differentiated parts,
the anterior mandibular beak and the posterior part.
These parts are connected by a sutural articulation
(synosteosis) and probably completely fused only in
old animals. Judging from the presence and abundance
of large foramina for blood vessels in the anterior part
and complete absence of similar foramina in the poste-
rior part of the symphysis, only the mandibular beak
was covered by horny tissue. Isolated mandibular beaks
of Azhdarcho lancicollis relatively frequently occur in
fluvial deposits of the Bissekty Formation (Turonian)
of Uzbekistan (Nessov, 1984, pl. 7, figs. 10, 11; Nessov,
1997, pl. 15, figs. 1–5). The relative length and shape of
the mandibular beak of azhdarchids vary widely
(Fig. 2); this is probably connected with different feed-
ing modes, the study of which lies ahead. The shortest
and most massive mandibular beak is characteristic of
Bakonydraco, the longest and most slender beak is in
Quetzalcoatlus. The lateral outline of the dorsal margin
of the beak is concave in Zhejiangopterus and partially
(posteriorly) in Bakonydraco. In Azhdarcho and
Quetzalcoatlus, it is convex. The shape of the mandib-
ular beak of Volgadraco gen. nov. is most similar to that
of Azhdarcho and differs in the less convex, almost
straight dorsal margin in lateral view.
The number of foramina for blood vessels in the
mandibular beak probably decreased in the evolution of
azhdarchids. Turonian Azhdarcho, Santonian Bakony-
draco, and Azhdarchidae indet. from the Campanian of
Spain have many large foramina arranged in two rows
on the dorsal side and on each lateral side (Nessov,
1984, pl. 7, figs. 10, 11; Nessov, 1997, pl. 15, figs. 1–5;
Buffetaut, 1999, text-fig. 1a; Ösi et al., 2005, text-fig. 2).
In Maastrichtian Quetzalcoatlus, these foramina have
not been described (Kellner and Langston, 1996);
apparently, this taxon lacks these foramina. Volgadraco
gen. nov. has three relatively small foramina in each of
three sides of the beak, i.e., it is intermediate between
the two extreme variants. The reduction of vasculariza-
tion of the azhdarchid beak was probably connected
with increasing ceratinization of the horn cover. Appar-
ently, the foramina considered provided passage not
only for blood vessels but also for sensitive fibers of the
mandibular ramus of cranial nerve VII (facial nerve);
thus, the horn beak of early azhdarchids possessed cer-
tain tactile sensitivity, which was important for feeding.
The reduction of these foramina could have been con-
nected with changes in feeding strategy.
The Cenomanian beds of Morocco has yielded three
fragments of the jaw symphysis of toothless pterosaurs,
which are determined as an anterior end of the premax-
illa (upper jaw beak) of Pteranodontidae (?), anterior
end of the premaxilla of Azhdarchidae (?), and an ante-
rior fragment of the mandibular symphysis of Tape-
jaridae (Wellnhofer and Buffetaut, 1999, text-figs. 2, 4, 5).
In our opinion, the three fragments belong to one azh-
darchid taxon; these are a mandibular beak, an upper
jaw beak, and a more posterior fragment of the premax-
illa, with an anterior fragment of the cranial crest. The
Cenomanian azhdarchid from Morocco has fewer vascu-
lar foramina in the mandibular beak, the lateral foramina
form only one (dorsal) row and dorsal foramina are only
present in the anterior part of the beak. However, the
extent of vascularization of the mandibular beak of this
taxon is higher than in Volgadraco gen. nov.
The incomplete cervical vertebra of a pterosaur
from the Campanian of Delaware, United States, that
was referred to Ornithocheiridae (Baird and Galton,
1981, text-fig. 2), is almost identical to specimen SGU,
no. 47/104a and could have been cervical vertebra 3 of
an azhdarchid. As in Volgadraco gen. nov., this speci-
men has a small lateral pneumatic foramen.
Material. In addition to the holotype, the type
locality has yielded cervical vertebra 3 (SGU,
no. 47/104a), cervical vertebra 9 (SGU, no. 48/104a),
posterior part of the notarium consisting of four verte-
brae (SGU, no. 49/104a), a fragment of the presumable
first right phalanx of the wing digit (SGU, no. 51/104a),
and a fragment of the left femur (SGU, no. 50/104a).
(a)
(b)
(c)
(d)
(e)
Fig. 2. The shape of the mandibular beak of the lower jaw
in representatives of the family Azhdarchidae: (a) Bakony-
draco (after Ösi et al., 2005); (b) Zhejiangopterus (after
Unwin, Lü, 1997); (c) Quetzalcoatlus (after Kellner and
Langston, 1996); (d) Azhdarcho (based on specimen ZIN
PH, no. 85/44); and (e) Volgadraco gen. nov. The specimens
are shown on different scales, such that the mandibular
beaks are approximately equal in length.
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PALEONTOLOGICAL JOURNAL Vol. 42 No. 6 2008
AVERIANOV et al.
ACKNOWLEDGMENTS
The study was supported by the Board of the Presi-
dent of the Russian Federation (MD-255.2003.04) and
the Foundation for Assistance to Domestic Science.
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