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A new azhdarchoid pterosaur from the Cenomanian
(Late Cretaceous) of Lebanon
Ross A. Elgin •Eberhard Frey
Received: 16 September 2010 / Accepted: 7 October 2011
ÓSwiss Geological Society 2011
Abstract A new pterosaur, Microtuban altivolans gen. et
sp. nov., is described from the Sannine Formation of
northern Lebanon. The specimen is the first pterosaur from
the Early Cenomanian (Late Cretaceous) locality of Hjou
ˆla
and is regarded as the most complete pterosaur fossil dis-
covered from Africa. While postcranial characters indicate
a possible relationship with members of the Thalassodr-
omidae or Chaoyangopteridae, the specimen possesses an
exceptionally short wing-finger phalanx 4, forming only
1.1% of the total length of the wing-finger. Its appearance
along with an unnamed ornithocheiroid from the slightly
younger locality of Ha
ˆqel suggests that a number of
pterosaur taxa existed within the local area, perhaps living
on exposed carbonate platforms.
Keywords Pterosaur Azhdarchoidea Microtuban
Cretaceous Lebanon
Abbreviations
GMN Geological Museum of Nanjing (China)
HGM Henan Geological Museum, Zhenzhou (China)
IMCF Iwaki Coal and Fossil Museum (Japan)
MN Museu Nacional, Rio de Janerio (Brazil)
SMNK Staatliches Museum fu
¨r Naturkunde Karlsruhe
(Germany)
TMM Texas Memorial Museum (USA)
ZHNM Zhejiang Museum of Natural History, Hanzhou
(China)
Introduction
While the Late Cretaceous Lagersta
¨tten deposits of north-
ern Lebanon are famous for the exceptional preservation of
their invertebrate and fish faunas, the remains of higher
vertebrates are rare. Although pterosaurs, a group of aerial
archosauromorphs, had effectively achieved a world wide
distribution during the latter part of the Mesozoic, the first
pterosaur specimen from the Lebanese carbonates was only
recently described by Dalla Vecchia et al. (2001), con-
sisting of a single isolated forearm of a Late Cretaceous
ornithocheiroid. The deposits of northern Lebanon there-
fore follow a more general pattern observed across the
whole of the African plate, where pterosaur material is both
rare and consists of a rather sparse collection of fragmented
bones or teeth. To date, fossil discoveries have included:
‘‘rhamphorhynchoids’’ (Unwin and Heinrich 1999); orni-
thocheiroids, anhanguerids and pteranodontids (Swinton
1948; Mader and Kellner 1999; Wellnhofer and Buffetaut
1999); the dsungaripteroid Tendaguripterus recki (Unwin
and Heinrich 1999) from the Upper Jurassic of Tendaguru,
Tanzania; and several members of the Azhdarchoidea
(Wellnhofer and Buffetaut 1999), including the azhdar-
chids Arambourgiania philadelphiae (Arambourg 1954)
and Phosphatodraco mauritanicus (Suberbiola et al. 2003).
Recent additions to these also include two humeri
belonging to pterosaurs of the Dsungaripteroidea and the
Archaeopterodactyloidea from the Upper Jurassic of Ten-
daguru (Costa and Kellner 2009), and the aforementioned
specimen from northern Lebanon (Dalla Vecchia et al.
Editorial handling: Jean-Paul Billon-Bruyat.
R. A. Elgin (&)E. Frey
Staatliches Museum fu
¨r Naturkunde Karlsruhe,
Abteilung Geologie, 13 Erbprinzenstraße,
76133 Karlsruhe, Germany
e-mail: rosselgin@hotmail.com
Swiss J Geosci
DOI 10.1007/s00015-011-0081-1
2001). Therefore, in spite of their condition and relative
rarity, this collection of elements illustrates that Gondwana-
land supported a diverse number ofpterosaur taxa throughout
its geological history.
This paper describes a second pterosaur from the Late
Cretaceous (Cenomanian) limestone of northern Lebanon,
originating from the locality of Hjou
ˆla (Fig. 1). The spec-
imen is preserved on a single oval slab of limestone and is
partially complete, consisting of: the most posterior cerv-
icals and anterior dorsal vertebrae, the pectoral girdle, a
complete left wing, and the fragmented remains of the
hindlimbs (Fig. 2). It is relatively more complete than that
described by Dalla Vecchia et al. (2001) and is therefore
regarded as the most complete pterosaur yet discovered
from the African plate. The described specimen is housed
at the State Museum of Natural History Karlsruhe in
Germany under the collection number SMNK PAL 6595.
Geological setting
The regional tectonic history of Lebanon has been the
focus of several studies (e.g., Butler and Spencer 1999;
Brew et al. 2001) where the prominent Yammouneh Fault,
along with several smaller structures, represents the
northern extension of the Dead Sea fault system (Fig. 1a;
Abdel-Rahman and Nader 2002). During the Cretaceous
Period the majority of the sediments were deposited within
the Palmyride Basin, a large NNE–SSW trending intraplate
trough, which persisted until the end of the Cretaceous
when it was destroyed by regional compression. Within
this basin the sediments slope westwards to form a single
large monoclinal structure and the depositional environ-
ments are split between a western, open marine facies and
an eastern, coastal facies (Nader et al. 2006).
Of significant palaeontological interest are the Konser-
vat Lagersta
¨tten that consist of four major fossiliferous
localities: Sa
ˆhel Aalma, Nammou
ˆra, Ha
ˆqel, and Hjou
ˆla,
each of which are famous for their exceptional preservation
of Late Cretaceous invertebrates and fishes (e.g., Forey
et al. 2003; Hay 1903; Woodward 1942). The youngest of
these localities is Sa
ˆhel Aalma, which is Santonian in age
(Garassino 1994) while the others are Cenomanian and
deposited as part of the Sannine Formation (Fig. 1b), which
itself appears to have been created during a period of rel-
ative stability and low sea levels (Nader et al. 2006). The
Nammou
ˆra is regarded as late to mid Cenomanian in age
(Dalla Vecchia and Venturini 1999) while the localities of
Ha
ˆqel and Hjou
ˆla are both Early Cenomanian (Saint-Marc
1974); with the locality of Ha
ˆqel occupying a position
approximately 20 m stratigraphically higher than that of
Hjou
ˆla (Hu
¨ckel 1970). Other than fish, fossil vertebrates at
all of these localities are rare, however, birds (Dalla Vec-
chia and Chiappe 2002), turtles, dolichosaurs and marine
varanoids (Dalla Vecchia and Venturini 1999; Dal Sasso
and Renesto 1999) have nonetheless been described from
Fig. 1 a Geological map of northern Lebanon showing the localities of Ha
ˆqel and Hjou
ˆla. bRelative position of the Sannine Formation within
the Cretaceous strata of Lebanon. Figures adapted after Abdel-Rahman and Nader (2002)
R. A. Elgin, E. Frey
the limestone of Nammou
ˆra. In contrast to the older
localities of Ha
ˆqel and Hjou
ˆla, terrestrial plant remains are
also common at Nammou
ˆra (Dalla Vecchia and Venturini
1999), including a diverse selection of ferns, gymnosperms
and angiosperms. Some of these share an affinity with
similar aged flora in North America, central Europe and the
Crimea, suggesting a palaeoclimate similar to the present
day Mediterranean (Krassilov and Bacchia 2000). The
occurrence of these well preserved plant materials within
marine sediments indicates the proximity of the region to a
palaeoshoreline. In comparison to Nammou
ˆra, indetermi-
nate plant material (Krassilov and Bacchia 2000) and algae
(Basson 1972) are also known from Ha
ˆqel, where fossil
reptiles are represented by a single ornithocheiroid ptero-
saur (Dalla Vecchia et al. 2001). Prior to this study, fossil
reptiles were unknown from the locality of Hjou
ˆla. Saint-
Marc (1974) described the palaeoenvironments of both
Ha
ˆqel and Hjou
ˆla during the Cenomanian as a small,
oxygen depleted, marine basin, with the major land mass
being located in the present WSW portion of the Arabian
Peninsula. Nader et al. (2006) later described the deposi-
tional environment in the frame of a carbonate ramp model
with shallower waters prevailing to the far east of Lebanon.
Lithology and provenance
The specimen was purchased by the SMNK from a fossil
dealer with local contacts and thus the exact provenance of
the specimen is uncertain and worthy of discussion. The
SMNK was initially told that the pterosaur originated from
a quarry at Ha
ˆqel, although doubts were raised during
discussions with another local dealer. We were later
informed that this fossil had probably not been removed
from the quarry of Ha
ˆqel but was likely from the nearby
locality of Hjou
ˆla (Roy Nohra, personal communication).
As Hjou
ˆla is only *4 km south of Ha
ˆqel it is conceivable
that the fossil dealers and middle men were uncertain as to
the specimen’s exact provenance. The sediments of Ha
ˆqel,
however, contain a moderate amount of bioclasts and are
noticeably whiter in colouration than those of Hjou
ˆla,
which are more micritic. A comparison of the grey lime-
stone slab with other specimens housed at the SMNK leads
us to propose the Early Cenomanian locality of Hjou
ˆla as
the true provenance of this specimen. This conclusion
could be further confirmed by a thin section or petrographic
analysis, but these were beyond the scope of this
investigation.
Systematic palaeontology
Order Pterosauria KAUP 1834
Suborder Pterodactyloidea PLIENINGER 1901
Superfamily Azhdarchoidea NESSOV 1984; sensu UNWIN
2003
Genus Microtuban gen. nov.
Etymology Greek lijqo
´1=micros, for small; Arabic
=tu’ba¯n, for basilisk, dragon, a star in the in the
constellation Draco.
Diagnosis As for type species.
Type species. Microtuban altivolans gen. et sp. nov.
(Figs. 2,3)
Etymology altivolans: Latin altivolans =soaring/high
flyer.
Diagnosis An azhdarchoid pterosaur distinguishable by an
unusually high ratio of the first and second wing-finger
phalanges (wph 2/wph 1 =0.85) and a hyper-reduced
fourth wing-finger phalanx, accounting for 1.1% of the
total wing-finger length.
Fig. 2 Microtuban altivolans (SMNK PAL 6595) gen. et sp. nov.
aPhotograph, bline tracing corresponding to photograph in a.Scale
bars 50 mm. ccoracoid, carp carpus, cv cervical vertebrae, ddorsal
vertebrae, digits digits 1–3, ffemur, hl fragments of the hindlimb, hu
humerus, mc metacarpal, pa preaxial carpal, pt pteroid, rradius,
sscapula, uulna, wph wing-finger phalanges (digit 4)
A Cenomanian azhdarchoid from Lebanon
Holotype The holotype specimen is housed in the Staatli-
ches Museum fu
¨r Naturkunde Karlsruhe (Germany) under
the collection number SMNK PAL 6595.
Locality ?Hjou
ˆla (= Hadjoula), town and region 35 km
NNE of Beirut (Lebanon).
Horizon Sannine Formation, Late Cretaceous (Early
Cenomanian).
Description
Cervical vertebrae and associated ribs At least three cru-
shed cervicals are preserved in dorsolateral view while
incomplete fragments of bone, cranial to the seventh cer-
vical, may represent the remains of the sixth cervical
vertebra. The seventh and eighth cervicals are in natural
articulation, where the postzygapophyses of the former
overlie the latter vertebra. The ninth cervical is in natural
articulation with the first thoracic vertebra (d1). The neural
spines of all the vertebrae except that of the ninth cervical
are broken and missing. The seventh cervical is longer than
that of the eighth (Table 1) and the prezygapophyses of
both are widely splayed, lying lateral to the postzygap-
ophyses. The prezygapophyses of the seventh cervical are
orientated craniolaterally at an angle of *45°to the
Fig. 3 Selected elements of Microtuban altivolans gen. et sp. nov.
with specific points of interest. aOverview of the forearm, bthe
cranial aspect of the pectoral girdle and cervical/dorsal series in dorsal
view, cthe right femur in dorsal view, dfracture across the shaft of
mc IV in cranial view (arrow indicates the termination of metacarpal
?1), eclose up of the left manus and first wing-finger phalanx in
dorsal view, fthe fourth wing-finger phalanx in ventral view (arrow
indicating the articulation between wph 3 and 4). Scale bars a50 mm,
b50 mm, c10 mm, d10 mm, e10 mm, f5 mm. ccoracoid, cX
cervical vertebra X, carp carpus, dX dorsal vertebra X, gt greater
trochanter, hhumerus, mc metacarpal, pac preaxial carpal, pf
pneumatic foramen, pt pteroid, rradius, uulna, wph wing-finger
phalanx
R. A. Elgin, E. Frey
midline. The left prezygapophysis of the ninth cervical face
dorsomedially although at what angle remains uncertain.
Double-headed ribs are visible in close association with the
last two cervical vertebrae. In cervical 8 these are long
([19 mm in length) but thin, and while one lies adjacent,
though un-fused, to the left prezygapophysis, another can
be tentatively traced to the opposite side. More ribs also lie
adjacent but un-fused to the transverse processes of the
ninth cervical; however, they are significantly larger and
more robust than those of the preceding vertebra.
Thoracic vertebrae and associated ribs A single tho-
racic vertebra is preserved in natural articulation with the
ninth cervical, flanked by two large and robust double-
headed ribs. A loose pair caudal to these suggests that they
were present up to and including the second thoracic ver-
tebrae. The neural spine is broken but must have run for a
length of 8 mm along the dorsal portion of the centrum.
The absence of any axial elements caudal to the first tho-
racic vertebrae indicates that no notarium was originally
present. The caudally positioned thoracic ribs are thin,
strongly curved and loosely positioned along with the
imagined midline of the axial skeleton.
Pectoral girdle Both left and right scapulae and corac-
oids are unfused but the similarity in their resting positions
indicates little post mortem displacement (Fig. 3b). The
scapula consists of a caudomedially directed blade, which
ventrally diverges into a scapular body bearing the glenoid
fossa. The angle between body and blade is approximately
145°. The scapular blade is straight, most likely long ovoid
in cross-section as can be concluded from the right scapula,
and is approximately five times longer than it is wide. The
cranial edge appears to have been a little more massive
than the caudal one. Towards its median terminus it tapers
to a sharp median margin with a rounded outline. The two
contralateral scapular blades are angled in a craniolateral
direction at an angle of *45°against the median plane.
The scapular body curves medially at an angle of about
145°measured against the long axis of the blade and while
crushed, was likely sub-triangular in cross-section. From
their articulation with the scapulae both coracoids point
medially, forming an angle of about 50°with the body of
their respective scapulae. The glenoid head of the coracoid
is angled against the shaft at about 80°and has three times
the diameter of the medially most preserved part of the
shaft. Cranioventrally the glenoid head is marked by a
blunt crest that medially merges with the cranioventral face
of the shaft. Nothing can be said about the morphology of
the glenoid fossa because it is either covered by sediment
and overlying bone, or is damaged. The coracoid shaft is
almost circular in cross-section at its midpoint and pre-
serves no trace of a medial divergence towards the furca.
On the right coracoid the ventral process of the furca is
visible at the left hand margin of the vertebral complex;
giving a ratio of 1:0.78 between scapula and coracoid.
Humerus Both humeri have been broken into two large
proximal and distal fragments with only the left humerus
preserving any osteological details. The proximal fragment
of this is preserved in its cranial aspect and consists of the
humeral head, which lies slightly disarticulated from the
lateral margin of the left scapular body. The collum of
the humeral head is dorsocaudally concave and bears the
deltopectoral crest; the proximal margin is regularly con-
cave and would have been confluent with the cranial corner
of the articular surface of the humeral head if not for a small
break in the bone. The cranial margin of the deltopectoral
crest is convex, whereby the convexity is a little stronger at
the cranioproximal corner than at the craniodistal one. At
the mid part of the deltopectoral crest the proximal and
caudal margins run almost parallel to each other. Close to
the collum, the distal margin of the deltopectoral crest
curves distally and merges with the humeral shaft. The
deltopectoral crest is almost flat, about 1.5 times as long as it
is wide, and the collum itself is inclined caudally at an angle
of about 43°. Near the break on the distal humeral fragment
there is an elongate, oval scar that probably acted as the
insertion point for a muscle; possibly m. triceps or m.
brachialis (Bennett 2003a). The distal fragment is observed
Table 1 Selected bone measurements in Microtuban altivolans gen.
et sp. nov.
Selected elements Length (mm)
Cervical 7 23.6
Cervical 8 21.1
Cervical 9 *9.0
Dorsal 1 *10.0
Humerus 61.6–73.3
a
Radius 92.0
a
Carpus 13.0
pteroid [38.0
mc IV 122.0
a
mcIII? 50.0
dI p1 12.5
dIu 11.0
dIIu 11.0
dIIIp1 17.0
dIIIp2 3.0
dIIIp3 10.5
dIIIu 11.0
wph 1 135.0
wph 2 114.5
wph 3 63.5
wph 4 3.5
ddigit, etp extensor tendon process, mc metacarpal, ph phalanx,
postzy postzygapophyses, prezy prezygapophysis
a
Estimated values
A Cenomanian azhdarchoid from Lebanon
in cranial view, the length of which suggests that a degree of
overlap likely existed between thetwo fragments and a middle
estimate of 67.5 mm is adopted for this study (Table 1).
Radius/ulna The bones of the antebrachium have been
badly crushed and the compacta fragmented. The left
antebrachium has fractured into at least one proximal and
one distal portion, each of which preserves their respective
articular surfaces. The proximal radial fragments, identified
by their proximodorsal tubercle, lie almost perpendicular to
the distal articular face of the left humerus. The proximal
fragments are overlain by their distal fragments, the latter
of which are orientated almost perpendicular to the former.
An exception occurs where a further fragment of bone,
attributed to the middle portion of the ulna, overlies and
converges with the proximal end of the distal ulnar frag-
ment (Fig. 3a). The distal fragments of the ulna and radius
run parallel to each other, the diameter of bones
approaching a ratio of 1:0.7 towards the midpoint of the
shaft. The preserved diameter is fairly reliable because of
the late diagenetic compaction, which preserved the actual
diameter of the bones in the bedding plane.
Carpus Both proximal and distal elements are present
and preserved in craniodorsal view, although abrasion of
the compacta limits the observed articulation between the
proximal and distal blocks to the cranial third of the carpus.
It is thus not possible to identify the presence of a syn-
carpal, although given the general completeness of the
carpus this appears to be likely and the term is adopted
here. The left carpus remains in situ and forms an angle of
116.5°between the radius/ulna and the fourth metacarpal
(Fig. 3a). The cranial aspect of the proximal syncarpal is
cuboid in appearance while that of the distal syncarpal
cannot be determined. A large, longitudinally ovoid exca-
vation, preserving slightly broken margins, is located in a
patch of predominantly intact compacta on the dorsal sur-
face of the distal syncarpal, close to the cranial margin.
Within this depression three smaller, presumably pneu-
matic, foramina pierce the distal syncarpal. The left pteroid
and the preaxial carpal are preserved close to their natural
positions (Fig. 3a). The pteroid is long and slender, about
0.75 mm wide at its distal terminus, but has been displaced
medially so that the proximal portion is hidden by the
overlying radius; the exact length of the element is thus
unknown. The distal end does not taper but shows a
rounded knob-like termination that is slightly kinked in the
direction of the antebrachium. In the proximal third of the
pteroid, a piece of the compacta is missing, revealing the
hollow interior of the bone. The preaxial carpal has rotated
over the distal margin of its articular face on the distal
carpal block and now lies parallel to the fourth metacarpal.
An oval sesamoid with an evenly convex surface (‘‘Sesa-
moid A’’ =pisiform after Bennett 2008) sits within the
fovea of the preaxial carpal.
Metacarpals The wing metacarpal is broken about
halfway along its length (Fig. 3a), the proximal and distal
fragments of which are displaced slightly. The shaft of the
metacarpal narrows distally but then expands caudally at its
most distal margin, forming a pair of condyles for the
articulation of the first wing-finger phalanx. The distal
dorsal condyle shows only a slight compaction and is thus
well preserved in three dimensions; the dorsal surface of
which is slightly concave with a shallow elevation in the
centre. In cranial view the condyle is directed slightly
dorsolaterally at an angle of *20°. Caudoproximally the
rim of the dorsal condyle terminates abruptly, forming a
short concavity that borders the condylar neck caudally. All
three remaining metacarpals can be observed in situ along
the craniodistal face of the wing metacarpal and form a
natural contact with the digits. These can be traced proxi-
mally only as far as the large break across the fourth
metacarpal, with the exception of a single metacarpal (mc
?I), which is preserved on the proximal fragment of the
wing metacarpal and tapers to a natural termination some
48 mm distal to the carpometacarpal articulation (Fig. 3d).
Damage to the metacarpals indicates that even these slen-
der bones were hollow.
Digits The left manus is preserved in a slightly hyper-
extended position. Digit I overlies digit II, however, digit
III has been displaced slightly caudally with the palmer
part of the proximal articulation condyle of its first phalanx
now overlying the dorsal margin of the first phalanx of
digit I (Fig. 3e). All of the elements belonging to the digits
are in full articulation. The dorsally facing compacta of the
phalanges of digit 1 are mostly eroded and the first phalanx
shows signs of compaction along the mid-part of its shaft;
the palmer face of which is concave between the articu-
lation heads. A narrow trace, most likely the remnants of a
claw sheath, is present, adjacent to the tip, along the caudal
margin of the ungual phalanx. Of digit II only the ungual
phalanx is visible. Distal to the tip of the ungual the
keratinous claw sheath is visible as a yellowish buff trace
that extends the tip of the ungual by at least 2 mm. Com-
pared with the first phalanx of digit I the concavity of the
shaft of the first phalanx of digit III is shallow. Phalanx 2 of
digit III has barely one-fourth of the length of the first
phalanx and is marked by a deep palmer notch and a dorsal
styloid process that has one-third of the length of that
phalanx. This process forms a bone lock that hinders a
hyper-extension of the third phalanx of digit III. The third
phalanx is almost conical with a very shallow circumfer-
ential concavity in its distal two-thirds. According to its
external mould, the distal articular condyle with the ungual
phalanx was almost confluent with the shaft. The ungual
phalanx of digit III is preserved predominantly as an
impression, lined with some remnants of the compacta
along the lateral sulcus and the very tip. This tip is
R. A. Elgin, E. Frey
prolonged by a black pyrolusite or goethite stain, 3 mm
in length, which represents the remains of a keratinous
sheath. All ungual phalanges are—or in the case of digit III
were—11 mm long.
Wing-finger Only those elements belonging to the left
wing-finger can be identified and preserve the fourth digit
in its entirety. With the exception of the third and fourth
phalanges these have been displaced and lie slightly out of
natural articulation with their neighbouring elements. The
first wing-finger phalanx is preserved in partial articulation
with the fourth metacarpal and lies flexed back to such an
extent that the caudal process now overlies the dorsocaudal
surface of metacarpal IV, forming an angle of 3.5°between
the two bones. This flexion has separated the metacarpal IV
and the first wing-finger phalanx so that only the extensor
tendon process still lies between the condyles of the
metacarpal. The lack of contact between the two elements
suggests that the metacarpophalangeal articulation is likely
hyper-flexed. The distal terminus of the phalanx shows
some surface erosion as does the dorsal margin of the
proximal cotyle, but the margin of the gently convex
articulation with phalanx 2 is still visible. The extensor
tendon process is not fused to the first wing phalanx and is
sub-triangular outline with a deeply concave cranial mar-
gin. Caudally this rises into a blunt ridge and becomes
confluent with the proximal ridge above the articular face.
This latter ridge tapers caudally and is perforated by a
pneumatic foramen that is partly obscured by the dorsal
condyle. The remaining three phalanges of the wing-finger
lie adjacent to each other and display a shallow caudally
directed curvature. In contrast to the other elements of the
wing these are exposed in ventral view. The second wing-
finger phalanx is 85% of the length of the first wing-finger
phalanx and preserves a gentle, caudally directed curva-
ture. The bone formed a long oval in cross-sectional view.
The third wing-finger phalanx is missing most of the
compacta and is around half the size of the second (i.e.,
55%). The distal articulation face is only one-fourth the
size of the proximal one. The fourth wing-finger phalanx is
a tiny element about 3.5 mm in length and shows three
shallow, distally converging striae on its dorsal face
(Fig. 3f). The caudal margin of the bone is concave and
terminates in a blunt, slightly re-curved tip with a flat distal
surface.
Hindlimbs The hindlimbs have been crushed and broken
into several mostly indeterminable elements. The right
femur is preserved in its caudal aspect where the femoral
neck is offset from the shaft at an angle of 41°(Fig. 3c).
The greater trochanter is observed as a prominent, cranially
directed triangular process, the caudal margin of which is
slightly convex and marked by a blunt ridge that merges
distally with the femoral shaft. Between the trochanteric
ridge and the femoral neck a large, pneumatic, trabeculae-
lined opening pierces the shaft. Immediately distal to the
trochanteric area, portions of the femur were broken and
re-attached with a loss of some bone material.
Discussion
Ontogenetic age
The identification of unfused sutures in the skeleton, and
the sequence in which they occur, has proven useful to
determine the morphological age of a variety of arch-
osauromorphs (Brochu 1995,1996; Irmis 2007), included
pterosaurs (e.g., Bennett 1993; Kellner and Tomida 2000).
While Bennett (1993) further noted an immature bone
grain, and pitting about the articular extremities as being
indicative of osteological immaturity in pterosaurs, the
bone grain of M. altivolans appears to be well developed.
Immaturity is however indicated by the lack of skeletal
fusion where the cervical and thoracic ribs are separate
from their respective vertebrae, the scapula and coracoid
have no formed a scapulocoracoid, and the presence of a
large suture between the extensor tendon process and the
first wing-finger phalanx. As such the animal did not live to
a late ontogenetic state and is inferred as being juvenile or
sub-adult.
Taphonomy
The skeleton of M. altivolans shows some unusual features
in that while almost all the long bones have been badly
fractured (Fig. 3a), many of these elements have remained
in close association or lie just beyond bone lock. Fragile
elements that are easily displaced by post mortem move-
ment, including the pteroid, preaxial carpal, metacarpalia,
and digits I–III, are also preserved in situ or with only
minor displacement. The humerus, radius, ulna and meta-
carpal IV were broken transversely by a single event and
although one fragment of the bone often overlies the other,
there has been little actual displacement. It is difficult to
explain these fracture patterns as a result of a natural decay
process. The sediment indicates that stagnant, and possibly
hostile, seafloor conditions persisted in the local environ-
ment while disruption by sediment activities or high-
energy currents is unlikely based on the lithology. The lack
of any trace of bioturbation excludes any benthic or en-
dobenthic scavengers as the cause of the given breakage
pattern, thus the carcass of the pterosaur encountered a
violent traumatic encounter of an unknown origin. The fact
that most of the broken bones are still aligned can only be
explained by the presence of soft tissues that held the
fractured elements together to a large degree. The breakage
of the bones must have occurred when the pterosaur was
A Cenomanian azhdarchoid from Lebanon
either still alive or freshly dead and in a very early stage of
decay.
Systematic palaeontology
The presence of an elongate wing metacarpal identifies
M. altivolans as a pterodactyloid, but it is more specifically
diagnosed as an azhdarchoid by a relatively short wing-
finger with a rapid decline of phalanx length distally
(Lu
¨et al. 2008), an elongated wing-finger phalanx 1 being
[40% of the entire wing finger (Kellner 2003), and a well
developed tubercle on the caudoventral margin of the
coracoid (Kellner 2004). The pneumatisation of the hind-
limb and the presence of a well developed greater
trochanter further support this conclusion, where the for-
mer has been demonstrated to be widespread throughout
the Azhdarchoidea by means of a large excavation on the
craniodorsal face of the femur (e.g., Claessens et al. 2009;
Eck et al. 2011).
The Azhdarchoidea itself is comprised of four families,
the Tapejaridae, the Thalassodromidae, the Chaoyangop-
teridae, and the Azhdarchidae (see Lu
¨et al. 2008), along
with the Protoazhdarchidae as a potential fifth (Frey et al.
2011). The assignment of M. altivolans to one of these
families is complicated as the majority of diagnostic
characters are restricted to the cranium and the middle
cervicals (e.g., Kellner and Langston 1996; Kellner 2003;
Unwin 2003; Suberbiola et al. 2003; Witton 2008); none of
which can be observed in the described specimen. Of the
few remaining elements of the axial column, only the
posterior cervicals 7–9 and the first dorsal vertebrae are
identified. The lack of the mid cervical vertebrae and the
poor preservation of any diagnostic features on the
remaining elements prevent an extensive comparison with
other azhdarchoids. The posterior cervicals of the Moroc-
can azhdarchid Phosphatodraco mauritanicus (Suberbiola
et al. 2003), which has an unusually elongated seventh
vertebrae, are distinct from those of M. altivolans, whose
own cervicals more closely resemble those of other
pterodactyloid pterosaurs. Fortuitously additional postcra-
nial characters can be used for a more refined diagnosis.
The configuration of the metacarpals for example, whereby
the preaxial metacarpals appear to terminate distal to the
carpus is used to distinguish the described specimen from
the Tapejaridae, where a single preaxial metacarpal is
known to contact the wrist. While the hyper-reduction,
without loss, of the fourth phalanx to \5% that of the total
length of the wing-finger is known only for Quetzalcoatlus
(Kellner and Langston 1996; Fig. 4), an azhdarchid affinity
is rejected by a further comparison of postcranial elements.
Here the scapula and coracoid preserve a ratio of 1.30,
more comparable to that of non-azhdarchid azhdarchoids,
e.g., MN 6588-V (1.27); SMNK PAL 3843 (1.39), and an
unnumbered specimen at the SMNK (1.42, RAE, personal
observation), than that of Quetzalcoatlus (1.01) or even the
chaoyangopterid Shenzhoupterus chaoyangensis (1.00, Lu
¨
et al. 2008), while M. altivolans further lacks the well
developed ventral flange to the coracoid (Fig. 5). Unwin
and Martill (2007) described a number of postcranial
azhdarchid apomorphies that include: a highly elongated
wing metacarpal (i.e., mc IV [wph 1); and a wing-finger
forming \50% the total forelimb length. Lu
¨et al. (2008)
later included a mc IV/humerus ratio of [2.2. In M. al-
tivolans the wing metacarpal is slightly less than that of the
first wing-finger phalanx (i.e., mc IV/wph 1 =0.9), the
wing-finger forms 51–52% of the total forelimb length and
the mc IV/humerus ratio is between 1.7 and 2.0. Under
these qualifiers, M. altivolans is excluded from the
Azhdarchidae.
Despite the lack of a skull and the general state of
preservation, postcranial features can be used to exclude
M. altivolans from a placement within the Tapejaridae and
Azhdarchidae, however, its assignment to either the Thal-
assodromidae or the Chaoyangopteridae is complicated by
the fact that both of these families are defined by their
cranial characteristics alone (e.g., Kellner 2004;Lu
¨et al.
2008; Witton 2008). While a tentative similarity with
Shenzhoupterus chaoyangensis (Lu
¨et al. 2008) is noted
from ratios of the mc IV/hu and mc IV/wph 1, the majority
of body proportions do not differ substantially from those
of other derived azhdarchoids (Table 2). Furthermore those
elements that do, i.e., phalanx proportion in the wing-fin-
ger, differ considerably and isolate M. altivolans from
other azhdarchoids. The high ratio of the second wing-
finger phalanx to that of the first is greater than the range of
values observed for other azhdarchoids; contra to the
synapomorphy stated by Kellner (2003) for the Azhdar-
choidea where by the second wing-finger phalanx is always
more than 1/3rd smaller than the first wing-finger phalanx
(i.e., wph 2/wph 1 \0.7). While similar ratios are observed in
other pterodactyloid pterosaurs, e.g., Pteranodon,Nyctosaurus,
Germanodactylus and several selected ornithocheiroids,
all of which are readily distinguished from the described
specimen.
The phylogenetic placement of M. altivolans within the
Azhdarchoidea therefore remains uncertain and while
postcranial characteristics support the erection of a new
genus within either the Thalassodromidae (Witton 2009)or
Chaoyangopteridae (Lu
¨et al. 2008), no more specific a
diagnosis can, or should, be reliably made at this time.
General discussion
The placement of M. altivolans within the Thalasso-
dromidae/Chaoyangopteridae highlights the degree of to
which variations in wing phalange length can occur, along
R. A. Elgin, E. Frey
with the problems involved with identifying taxa from their
biometric proportions alone. Although the ratio of the first
and second wing-finger phalanges of the described speci-
men exceeds the range of values regarded as a
synapomorphy of the Azhdarchoidea (Kellner 2003), this is
not problematic as a suite of additional characters readily
support its position within the group. Defining pterosaurs in
absolute values is problematic as taxa or individuals (as a
result of natural intraspecific variations) will occasionally
fall outside the range covered by previously known
specimens. Indeed Sinopterus dongi (Wang and Zhou
2003) and a ?tapejarid specimen (SMNK PAL 6900,
Unwin and Martill 2007) also exceed the absolute value
given by Kellner (2003), although to a much smaller
degree, and indicate that such practices can often fail to
encompass the full range of values of the desired group.
The second unusual feature of the described specimen
also relates to the wing phalanges and the size of the ter-
minal wing-finger phalanx. While a reduction in the length
of the fourth wing-finger phalanx is observed in a number
Fig. 4 Bar chart illustrating the percentage of the total length of the
fourth digit formed by each phalanx. Hyper-reduction of the terminal
wing-finger phalanx is typically restricted to the Azhdarchidae and
distinguishes them from other members of the Azhdarchidae. List of
taxa from top to bottom:Arthurdactylus conandoylei (SMNK PAL
1132); Santanadactylus pricei (AMNH 22552); Eoazhdarcho
liaoxiensis (GMN-03-11-002); Sinopterus dongi (IVPP V 13363);
Shenzhoupterus chaoyangensis (HGM 41HIII-305A); Huaxiapterus
jii (GMN-03-11-001); tapejarid indet. (SMNK PAL 6409); tapejarid
indet. (SMNK PAL 3900); Quetzalcoatlus northropi (TMM 41450);
Quetzalcoatlus sp. (TMM 41961); Microtuban altivolans (SMNK
PAL 6595)
Fig. 5 Comparison of the scapula and coracoid elements from aan
un-named tapejarid (SMNK PAL 3843). bMicrotuban altivolans
(SMNK PAL 6595). cQuetzalcoatlus sp. (TMM 42138-1). All line
tracings have been scaled to the same size, based on the coracoid
length. The coracoid: scapula ratio of 1.30 in M. altivolans is similar
to that of other azhdarchoid pterosaurs e.g., SMNK PAL 3843, 1:1.39;
unlabelled azhdarchoid indet. (SMNK), 1.27; MN 6588-V, 1:1.27 and
is clearly distinct from that of other more derived pterosaurs, e.g.,
Shenzhoupterus chaoyangensis (1:1) and Quetzalcoatlus sp. (1:1).
ccoracoid, cf coracoid flange, gf glenoid fossa, approximate location,
sscapula, sta sternal articulation
A Cenomanian azhdarchoid from Lebanon
of taxa, specifically those within the Azhdarchoidea, the
actual loss of the phalanx is rare; having only been docu-
mented in specimens of Anurognathus,Beipiaopterus and
Nyctosaurus (Bennett 2003b,2007;Lu
¨2003). Even within
the Azhdarchoidea the reduction of the fourth phalanx to a
length \5% that of the total wing finger is known only for
Quetzalcoatlus. Its presence here is therefore unusual and
extends the range of this feature to encompass non-azh-
darchid azhdarchoids. The biomechanical reasoning behind
the extreme reduction or loss of the fourth phalanx remains
uncertain but must have been linked to either the aerody-
namic forces acting on the distal section of the wing, and
the subsequent deformation of the leading edge spar/
membrane, or acted as one possible means of lowering the
overall aspect ratio.
The presence of M. altivolans within the Cenomanian
aged deposits of Lebanon represents one of the few non-
azhdarchid azhdarchoids known from the Late Cretaceous.
Members of the Chaoyangopteridae such as Shenzhoupte-
rus chaoyangensis and Chaoyangopterus zhangi from the
Jiufotang Formation of Liaoning Province, are dated as
Early Aptian, while Eopteranodon was uncovered from
Barremian–Early Aptian deposits (Swisher et al. 1999).
Members of the Thalassodromidae are known chiefly from
the NE of Brazil, the two major fossiliferous deposits are
both regarded as Early Cretaceous in age (Kellner and
Campos 2002; Unwin and Martill 2007; Witton 2009). An
isolated rostrum and mandible from the Javelina Formation
of North America (Wellnhofer 1991; Kellner 2004) there-
fore appears to represent the sole member of the
Thalassodromidae known from the Late Cretaceous (Mar-
till and Naish 2006). The confirmation of M. altivolans as a
thalassodromid or chaoyangopterid pterosaur within the
Early Cenomanian Lagersta
¨tten of Lebanon therefore
reveals only a minor portion of the ghost lineage available
to these taxa, but it is significant as the dating of these
deposits appears to be uncontroversial. Azhdarchoid
remains are also known from the Cenomanian Kem Kem
locality of Morocco, but are regarded as either tapejarid or
azhdarchid pterosaurs (Kellner and Mader 1997; Well-
nhofer and Buffetaut 1999) and as such are not directly
comparable to M. altivolans. A similar situation is found in
the Cenomanian chalk of England that yields specimens of
Anhanguera and Lonchodectes (Unwin 2000), while sub-
stantial material recovered from the Cenomanian aged
Cambridge Greensand of England is likewise incomparable
and thought to have been reworked from the older Albian
deposits (Wellnhofer 1991;DallaVecchiaetal.2001).
Microtuban altivolans therefore represents one of the youn-
gest confirmed thalassodromid/chaoyangopterid pterosaurs,
perhaps the only one of a known Cenomanian age, and indi-
cates a greater geographical distribution existed than
the immediate localities encompassed by the Lagersta
¨tten
deposits of Brazil and China.
Pterosaurs from the eastern edge of the African Plate
remain exceedingly rare and those belonging to the portion
that now forms the Middle East are restricted to the Early
Cenomanian M. altivolans, an indeterminate ornithochei-
roid (Dalla Vecchia et al. 2001), and a ‘‘pterodactyloid’’
hindlimb (Tchernov et al. 1996). As azhdarchid pterosaurs
are known from the upper Campanian of Israel and the
upper Maastrichtian of Jordan (Arambourgiania philadel-
phiae, Arambourg 1954; Frey and Martill 1996), the region
was undoubtedly inhabited by a variety of pterosaurs more
or less continuously throughout the Late Cretaceous. If
pterosaurs formed a major portion of the local ecosystem
Table 2 Ratios of selected long
bone elements in various
pterosaur taxa
a
Estimated values
Taxa Specimen number wph 2/wph 1 mc IV/hu mc IV/wph 1
Azhdarchidae
Zhejiangopterus linhaiensis ZHNM M1323 0.66 2.45 1.04
Quetzalcoatlus sp. TMM 41961 0.51 90.81
Quetzalcoatlus sp. TMM 42422 0.51 2.48 1.03
Q. northropi TMM 41450 91.79
a
9
Chaoyangopteridae
Shenzhoupterus chaoyangensis HGM41HIII-305A 0.68 2.12 0.95
Eoazhdarcho liaoxiensis GMN-03-11-002 0.78 1.50 0.76
Thalassodromidae
Tupuxuara longicristatus IMCF 1052 0.60 1.53 0.71
Tapejaridae
Huaxiapterus jii GMN-03-11-001 0.79 1.67 0.81
tapejarid sp. indet. SMNK PAL 6409 0.71 99
tapejarid sp. indet. SMNK PAL 3900 0.62 1.39 0.62
Sinopterus dongi IVPP V 13363 0.73 1.63 0.79
Microtuban altivolans SMNK PAL 6595 0.85 1.81
a
0.90
R. A. Elgin, E. Frey
during the Cenomanian then it is surprising that so few of
their remains have been uncovered as, unlike many local-
ities, the Lagersta
¨tten of Ha
ˆqel and Hjou
ˆla are quarried
exclusively for their fossils contents. The palaeogeo-
graphical reconstructions of northern Lebanon during the
Cenomanian indicate that an open marine setting prevailed
in the west of the country and the appearance of pterosaurs
here, several hundred km from the nearest inferred palae-
ocoastline, inevitably raises questions as to how they came
to rest in this setting. The animal perhaps died migrating
between landmasses, drifted into the region on the ocean
currents, or have inhabited any palaeoislands that existed
within the immediate region. Dalla Vecchia et al. (2001)
suggested that the pterosaurs of the Cenomanian inhab-
ited small islands composed of carbonate exposures, a
hypothesis supported by the presence of sub-aerially
exposed carbonate reefs, with palaeochannels, within the
Early Cenomanian lithologies (Nader et al. 2006). Terres-
trial plant deposits are also known from these localities
indicating that material from colonised islands in the local
area, or the nearest landmass, were occasionally swept into
the region. As this input of material is of a poorer quality
than that found at younger localities the source is regarded
as being more distant than that of the upper Cenomanian
locality of Nammou
ˆra. The presence of these small ptero-
saurs so far from the nearest major landmass, along with
the generally good preservation observed within the spec-
imen, suggests that Early Cenomanian pterosaurs probably
did inhabit exposed carbonate islands within the local
region. Any such platforms however were located more
distant in the Early Cenomanian localities when compared
to these of the Late Cenomanian. The relative lack of any
teeth or bone fragments attributed to pterosaurs, despite the
extensive quarrying of these localities for commercial
fossils suggests that pterosaurs either did not reside close
by in great numbers, or unknown conditions prevented
their preservation in a locality famous for its spectacular
preservation of fossil fish.
Conclusions
Microtuban altivolans represents a small, ontogenetically
immature azhdarchoid pterosaur tentatively associated with
the Thalassodromidae or Chaoyangopteridae. Differentiat-
ing between taxa of either group based on postcranial
remains or biometric data and ratios is currently not pos-
sible and no more a specific diagnosis can be made. The
unusual ratios formed by the second and fourth wing finger
phalanges highlight some of the problems with using
biometry to identify pterosaur taxa, indicating that the
lengths of the individual wing elements are often highly
variable. Additionally some ratios that are generally useful,
e.g., wph 2/wph 1 \0.7 (Kellner 2003)ormcIV[wph 1
(Unwin and Martill 2007), can ultimately fail to encompass
the diversity of a desired group. The hyper-reduction
without loss of the fourth wing-finger phalanx within
M. altivolans indicates that this feature was present
throughout the Azhdarchoidea and was not solely restricted
to the largest azhdarchids.
While African pterosaurs remain exceedingly rare the
discovery of M. altivolans from the Cenomanian deposits of
Lebanon, and the first from Hjou
ˆla, fills in the earliest part
of the Thalassodromidae/Choayangopteridae ghost lineage
in the Late Cretaceous, indicating that these pterosaurs were
more geographically widespread than the immediate
localities covered by the Crato/Santana and Jehol Forma-
tions of Brazil and China. Although the exact provenance of
the described specimen is uncertain, the only alternative site
(i.e., Ha
ˆqel) is also Cenomanian and would indicate an even
younger age than we have suggested here. As such, no
conclusions presented in this manuscript will become void
if the specimen is later proved to have originated from a
neighbouring locality. The presence of this small pterosaur
in an open marine setting, many hundreds of kilometres
from the nearest palaeoshoreline, supports the idea that
pterosaurs of the Cenomanian of Lebanon inhabited
exposed carbonate islands (Dalla Vecchia et al. 2001).
Given the rarity of these specimens it is unlikely that Hjou
ˆla
will ever be as important to pterosaur workers as other
European, Asian and South American Lagersta
¨tten locali-
ties, however, it does promises the prospect of future finds
from a little known Cretaceous age of pterosaur evolution.
Acknowledgments The authors extend their thanks to Roy Nohra
for several discussions on the possible provenance of the specimen,
Volker Griener (SMNK) for assisting with the photography, and Chris
Bennett, David Unwin, David Martill, and Alex Kellner for their
valuable and helpful comments on an earlier version of the manuscript.
Also we thank two anonymous reviewers. This research was supported
by the DFG, Deutsche Forschungsgemeinschaft (FR1314/15-1).
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