A new toothless pterosaur (Pterodactyloidea) from Southern Brazil with insights into the paleoecology of a Cretaceous desert

Abstract

The first pterosaur bone bed from Brazil was reported in 2014 at the outskirts of the town Cruzeiro do Oeste, Paraná State, in the Southern region of the country. Here named 'cemitério dos pterossauros' site, these outcrops were referred to the Goio-Erê Formation (Turonian-Campanian) of the Caiuá Group (Bauru Basin) and revealed the presence of hundreds of isolated or partially articulated elements of the tapejarine pterosaur Caiuajara and fewer amounts of a theropod dinosaur. Here we present a new tapejaromorph flying reptile from this site, Keresdrakon vilsoni gen. et sp. nov., which shows a unique blunt ridge on the dorsal surface of the posterior end of the dentary. Morphological and osteohistological features indicate that all recovered individuals represent late juveniles or sub-adults. This site shows the first direct evidence of sympatry in Pterosauria. The two distinct flying reptiles coexisted with a theropod dinosaur, providing a rare glimpse of a paleobiological community from a Cretaceous desert.

Full text

Anais da Academia Brasileira de Ciências (2019) 91(Suppl. 2): e20190768
(Annals of the Brazilian Academy of Sciences)
Printed version ISSN 0001-3765 / Online version ISSN 1678-2690
http://dx.doi.org/10.1590/0001-3765201920190768
www.scielo.br/aabc | www.fb.com/aabcjournal
An Acad Bras Cienc (2019) 91(Suppl. 2)
EARTH SCIENCES
A new toothless pterosaur (Pterodactyloidea) from Southern Brazil
with insights into the paleoecology of a Cretaceous desert
ALEXANDER W.A. KELLNER1, LUIZ C. WEINSCHÜTZ2,
BORJA HOLGADO1,3, RENAN A.M. BANTIM4 and JULIANA M. SAYÃO1,5
1Laboratory of Systematics and Taphonomy of Fossil Vertebrates, Departamento de Geologia e Paleontologia,
Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, s/n,
São Cristóvão, 20940-040 Rio de Janeiro, RJ, Brazil
2CENPALEO – Centro Paleontológico da Universidade do Contestado,
Universidade do Contestado, Jardim do Moinho, 89306-076 Mafra, SC, Brazil
3Institut Català de Paleontologia ‘Miquel Crusafont’ (ICP), C/ de les Columnes,
Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Barcelona, Catalonia, Spain
4Laboratório de Paleontologia, Universidade Regional do Cariri (URCA),
Rua Coronel Antônio Luiz, 1161, 63195-000 Crato, CE, Brazil
5Laboratório de Paleobiologia e Microestruturas, Centro Acadêmico de Vitória, Universidade Federal de Pernambuco,
Rua do Alto Reservatório, s/n, Bela Vista, 55608-680 Vitória do Santo Antão, PE, Brazil
Manuscript received on July 5, 2019; accepted for publication on August 6, 2019
How to cite: KELLNER AWA, WEINSCHÜTZ LC, HOLGADO B, BANTIM RAM AND SAYÃO JM. 2019. A new
toothless pterosaur (Pterodactyloidea) from Southern Brazil with insights into the paleoecology of a Cretaceous desert.
An Acad Bras Cienc 91: e20190768. DOI 10.1590/0001-3765201920190768.
Abstract: The rst pterosaur bone bed from Brazil was reported in 2014 at the outskirts of the town Cruzeiro
do Oeste, Paraná State, in the Southern region of the country. Here named `cemitério dos pterossauros´ site,
these outcrops were referred to the Goio-Erê Formation (Turonian-Campanian) of the Caiuá Group (Bauru
Basin) and revealed the presence of hundreds of isolated or partially articulated elements of the tapejarine
pterosaur Caiuajara and fewer amounts of a theropod dinosaur. Here we present a new tapejaromorph
ying reptile from this site, Keresdrakon vilsoni gen. et sp. nov., which shows a unique blunt ridge on the
dorsal surface of the posterior end of the dentary. Morphological and osteohistological features indicate
that all recovered individuals represent late juveniles or sub-adults. This site shows the rst direct evidence
of sympatry in Pterosauria. The two distinct ying reptiles coexisted with a theropod dinosaur, providing
a rare glimpse of a paleobiological community from a Cretaceous desert.
Key words: Paleoecology, Pterosauria, Pterodactyloidea, Keresdrakon vilsoni, Paraná, Cretaceous.
Correspondence to: Alexander W.A. Kellner
E-mail: kellner@mn.ufrj.br
ORCid: https://orcid.org/0000-0001-7174-9447
* Contribution to the centenary of the Brazilian Academy of
Sciences.
INTRODUCTION
Pterosaurs are the rst vertebrates to conquer the air
by developing powered ight (e.g., Kellner 2006).
Despite having been recovered in all continents
(Hammer and Hickerson 1994, Barrett et al. 2008),
their fossil record can be considered as patchy,
with only few deposits having presented complete
or nearly complete skeletons (e.g., Eaton 1910,
Tischlinger and Frey 2002, Barrett et al. 2008,
Bantim et al. 2014, Kellner 2017). Even in the
stratigraphic units that have yielded large quantities

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 2 | 32
of these volant archosaurs, there is a general lack of
pterosaur bone beds (e.g., Wellnhofer 1975, Wild
1978, Saraiva et al. 2008, Dalla Vecchia 2014,
Cheng et al. 2017, Pinheiro and Rodrigues 2017),
so far restricted to only three occurrences: the
Lagarcito Formation (Lower Cretaceous, Albian) in
San Luis, Argentina (Yrigoyen 1975, Chiappe et al.
1998), the Lower Cretaceous deposits of the Tugulu
Group in Hami, Xinjiang, China (Eberth et al.
2001, Wang et al. 2014), and the strata of the Upper
Cretaceous Goio-Erê Formation (Bauru Group)
that outcrop at Cruzeiro do Oeste, Paraná State,
Brazil (Basilici et al. 2012, Manzig et al. 2014).
The latter is the rst occurrence of pterosaurs in
the Bauru Group that has yielded a comparatively
large number of other fossil vertebrates such as
dinosaurs (e.g., Brusatte et al. 2017, Bandeira et al.
2018) and crocodylomorphs (e.g., Ri et al. 2012).
The outcrops at the region of Cruzeiro do
Oeste have a peculiar history (Fig. 1). The site,
here named `cemitério dos pterossauros´ (pterosaur
graveyard), was discovered some 40 years ago by
the Dobruski family. No fieldwork was carried
out in the area over these years until it was
rediscovered in 2011, when some specimens that
had been eroding on the surface were collected
without fine stratigraphic control (see Manzig
and Weinschütz 2012). Later (October/ 2012)
one of the authors (AWAK) was invited by LCW
and Paulo C. Manzig (at that time associated
with CENPALEO - Centro Paleontológico of
the Universidade do Contestado) to examine this
material and recognized the presence of at least two
pterosaur taxa and one theropod dinosaur. He has
encouraged CENPALEO to organize eldwork in
the region, which was carried out in cooperation
with the Museu Nacional/UFRJ during July/2012,
January-February/2013, July/2013, and July/2014.
This activity resulted in thousands of fossil bones,
mostly found isolated that were split between
CENPALEO and the Municipality of Cruzeiro do
Oeste by a written agreement signed some years
later. Some blocks (still unprepared) are housed
in the Museu Nacional and were not affected
by the recent fire that has consumed the main
building of the institution (e.g., Zamudio et al.
2018). Training for the preparation of the material
was performed by the Museu Nacional, first at
CENPALEO (July/2012) and then at Cruzeiro do
Oeste (August/2016).
The more numerous bones recovered so far
belong to a small tapejarine pterosaur that was
named Caiuajara dobruskii Manzig et al. 2014.
The previously identied dinosaur was recently
named Vespersaurus paranaensis Langer et al.
2019, also known by hundreds of isolated elements.
An acrodont lizard, Gueragama sulamericana
Simões et al. 2015, which was described based
on fragmentary material (Simões et al. 2015),
complete the known reptilian fauna from this
site. Lizard remains tend to be quite incomplete
(e.g., Chavarría-Arellano et al. 2018), for all those
representing ancient desertic environments.
In this study we present the description of the
second toothless pterosaur taxon from this deposit,
Keresdrakon vilsoni gen. et sp. nov., which is
known by far less specimens than Caiuajara and
Vespersaurus. We also explore the paleoecological
relationships of the known taxa of this Cretaceous
desert environment, which has the potential for
unveiling many new ndings (Kellner 2012).
GEOLOGICAL SETTING
The stratigraphic assignment of the deposits in
the outskirts of Cruzeiro do Oeste has been put
under dispute recently (Figs. 1-2). The `cemitério
dos pterossauros´ site was originally regarded
by Manzig et al. (2014) as belonging to the
Caiuá Group, more specically to the Goio-Erê
Formation. Langer et al. (2019) agreed with the
assignment to the Caiuá Group but argued that the
site is located in an area already mapped as the Rio
Paraná Formation (Fernandes 2004).

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 3 | 32
Figure 1 - Map showing the location of the `cemitério dos pterossauros´ site in Cruzeiro do Oeste (red arrow), Paraná State,
southern Brazil. (a) The outcrops of the Bauru Basin (light grey) in Brazil, (b) detail of the Bauru basin with the Rio Paraná (light
green), Goio-Erê (light blue), Santo Anastácio (grey) formations, and the Bauru Group (dark grey), and (c) stratigraphic chart
showing the relations of the former, including the underlying Serra Geral Formation (green).
The Bauru Basin is formed by the Bauru and
the Caiuá groups (Fernandes and Coimbra 2000)
and has its development linked to the isostatic
compensation related to the large basaltic lava
accumulation of the Eocretaceous Serra Geral
magmatic event (Fernandes 2004). Batezelli
(2010) showed that the Caiuá Group was formed
by a depocenter located in the southernmost part of
the basin (in relation to the Bauru Group) directed
towards the Paraná State and whose northern limit
extended to the southeastern part of the Minas
Gerais State. Based on the eolian sedimentary
rocks, the paleoclimate at that time of deposition is
regarded as arid (Fernandes 2004).
The Caiuá Group is characterized by
predominantly desert-type red beds and divided
into the Rio Paraná, Goio-Erê and Santo Anastácio
formations (Fernandes and Coimbra 2000). All
three units are interpreted as chronocorrelated
and interdigitated, whose limits are transitional
(Fernandes 2004). Their contact with the basalts of
the underlying Serra Geral Formation is marked by
an unconformity (Fig. 1).
The Rio Paraná Formation is composed of ne
to very ne to medium grained sandstones, forming
large eolian structures with medium to large cross
stratication that, according to Fernandes (2004),
correspond to the central region of the “sand sea”.
The Goio-Erê Formation consists of ne and very
ne (sometimes medium) grained sandstones, rich
in quartz and whose color ranges from reddish brown
to purplish gray. These rocks are mineralogically
and textually supermature. They form tabular
layers with cross-stratication, sometimes with at-
parallel lamination, and deposits that correspond
to wet interdunes (Fernandes and Coimbra 2000).
Lastly, the Santo Anastácio Formation lls shallow
troughs of the valleys formed by the Paraná river
tributaries. The deposits constitute massive tabular
sandstones and correspond to sand sheets present
on the extensive desertic marginal plains of the
former “sand sea” (Fernandes 2004).
Although the `cemitério dos pterossauros´ site
is showed to correspond to the Rio Paraná Formation
in the current geologic map encompassing the
region of Cruzeiro do Oeste, the lithological
characteristics of the outcrop with the bonebeds are
more consistent with the description of the deposits
of the Goio-Erê Formation. The fossils themselves
indicate the presence of humid inter-dunes
where life could thrive. Therefore, we interpret
the `cemitério dos pterossauros´ site as a non-
mappable occurrence of the Goio-Erê Formation.
Otherwise, it would indicate the presence of inter-
dune deposits within the Rio do Paraná Formation,
which contradicts its original interpretation.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 4 | 32
The age of those layers is also controversial.
Basilici et al. (2012) favor a Turonian - Campanian
age, with the lower limits even being considered as
Coniacian by Milani et al. (2007), while Batezelli
(2015) argues for a lower Cretaceous age (Aptian-
Albian). No denitive conclusion can be reached
at the present stage of knowledge, particularly
concerning the `cemitério dos pterossauros´ site.
Regarding the bonebeds, they occur on a
secondary road oor leading from the center of the
town Cruzeiro do Oeste to the rural areas nearby,
as well as on the right ravine (direction city - rural
areas). As pointed out before (Manzig et al. 2014),
there are three distinct lithological units formed
by massive, ne to very ne sandstones (Fig. 2).
The surface of the grains is opaque and covered
with iron oxide. On the top of the sequence there
are very fine sandstones. Four bonebeds have
been observed, with the lower one bearing many
disarticulated remains of pterosaurs (Caiuajara
and Keresdrakon) and one theropod dinosaur
(Vespersaurus). The same fossil assembly was
recovered in the subsequent two other bonebeds,
although elements tend to be sparser. The last
bonebed consists mainly of hundreds of very small
bones attributed to Caiuajara.
MATERIALS AND METHODS
PHYLOGENETIC ANALYSIS
In order to determine the phylogenetic position of
Keresdrakon vilsoni gen. et sp. nov., we performed
a phylogenetic analysis using the software TNT
1.5 (Golobo and Catalano 2016). This analysis
is based on Holgado et al. (2019 - see data matrix
there). We have used all taxa of that study (144)
adding only the new species. All characters are
discrete and the original coding was maintained.
Search for the most parsimonious trees (MPTs) was
conducted via Traditional Search (TBR swapping
algorithm), 10,000 replicates, random seed, and
collapsing trees after search. We also conducted the
analysis via New Technology using Sect. Search,
Ratchet (parameters: 20 substitutions made, or
99% swapping completed, 6 up-weighting prob.,
6 down-weighting prob., and a total number of
iterations of 10), Tree fusing, Driven search (15
initial addseqs., 15 times of min. length), random
seed, and without collapsing trees after search.
Subsequently, the results of the New Technology
were analyzed via Traditional Search (TBR
swapping algorithm), starting trees for RAM, and
without collapsing trees after search.
The coding of Keresdrakon vilsoni in the data
matrix published by Holgado et al. (2019) is as
follows:
101????????????????00?120000-00?0--00--
??0-???????????2????????????000???13200
101?30-00010000--0000?111?00?????
00020011?0?01520??1???????????????.
SLIDE PREPARATION
Two bones of Keresdrakon vilsoni gen. et sp.
nov. were sectioned for a preliminary histological
analysis (CP.V 2077 and CP.V 2374). All elements
were measured, photographed and described for
bone microstructure investigation before they
were sectioned, according to the methodology
proposed by Lamm (2013). Bones were sectioned
in the diaphysis portion, and a sample of about 1
cm thick from each was obtained for histological
slide preparation. These specimens were immersed
in clear epoxy resin Resapol T-208 catalyzed with
Butanox M50, cut with the aid of a micro rectify
(Dremel 4000 with extender cable 225) coupled
to a diamond disk. The section assembly side was
ground and polished in a metal polishing machine
(AROPOL-E, AROTEC LTDA) using AROTEC
abrasive grit (grit size 60 / P60, 120 / P120, 320
/ P400, 1200 / P2500). Finally, the sections were
examined and photographed in a light microscope
(Zeiss Inc. Barcelona, Spain) equipped with an
AxioCam camera with Axio Imager, after the

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 5 | 32
Figure 2 - Stratigraphic sequence of the `cemitério dos
pterossauros´ site, showing the recorded taxa (Caiuajara
dobruskii, Vespersaurus paranaensis and Keresdrakon vilsoni)
in the four (A-D) bonebeds, the correspondent depositional
environments, and the sedimentary structures. Note that in
bonebed D only small individuals of Caiuajara were collected.
histological slides were prepared. The M2 imaging
software was used in the examination procedure.
NOMENCLATURAL ACTS
This published work and the nomenclatural acts
it contains have been registered in ZooBank,
the proposed online registration system for the
International Code of Zoological Nomenclature.
The Zoobank Life Science Identiers (LSIDs) to
the prex http://zoobank.org/. The LSID for this
publication is urn:lsid:zoobank.org:pub:C4E8E040-
D158-42C3-A91F-E432CDEAB424, and the
LSIDs for the new erected groups and taxa
are: urn:lsid:zoobank.org:act:E26A65E0-2859-
4CD3-B773-B99D568D366C (Keresdrakon) and
urn:lsid:zoobank.org:act:8358C917-6C12-4390-
AAB8-37D82723BBCD (Keresdrakon vilsoni).
The following pterosaur genera and species are
mentioned in this study: Argentinadraco Kellner
and Calvo 2017, Caiuajara dobruskii Manzig et al.
2014, Caupedactylus Kellner 2013, Eurazhdarcho
Vremir et al. 2013, Hamipterus Wang et al. 2014,
Pteranodon Marsh 1876, Quetzalcoatlus Lawson
1975, Tapejara Kellner 1989, Thalassodromeus
Kellner and Campos 2002, Tupuxuara leonardii
Kellner 1994, and Zhejiangopterus linhaiensis Cai
and Wei 1994.
SYSTEMATIC PALEONTOLOGY
PTEROSAURIA Kaup 1834
PTERODACTYLOIDEA Plieninger 1901
AZHDARCHOIDEA Nesov 1984
TAPEJAROMORHA Andres et al. 2014
Keresdrakon gen. nov.
Etymology: A combination of Keres, death-
spirits who personified violent death in Greek
mythology and are associated to doom and/or
plunder; and drakon, which is the Ancient Greek
word for dragon or huge serpent.
Type species: Keresdrakon vilsoni, type by
monotypy.
Diagnosis: The same as for the type species.
Keresdrakon vilsoni gen. et sp. nov.
Etymology. In honor to Mr. Vilson Greinert,
a volunteer who dedicated hundreds of hours
preparing most of the specimens from `cemitério
dos pterossauros´ site housed in CENPALEO and
in the town of Cruzeiro do Oeste.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 6 | 32
Holotype. Partial skeleton including the
anterior portion of the skull, quadrate, almost
complete lower jaw, two cervical vertebrae, four
dorsal vertebrae, sternum, elements of the gastralia,
right scapula, incomplete humeri, proximal portion
of a radius, incomplete femora, incomplete tibia,
left ilium, right pubis, left ischium and other
fragmentary elements (CP.V 2069) housed at
the Centro Paleontológico (CENPALEO) of
the Universidade do Contestado, Mafra, Santa
Catarina, Brazil (Fig. 3, Table I). It was recovered
from bonebed C (Fig. 2).
Paratypes. Rostral end of a skull, including
the anterior part of the nasoantorbital fenestra
(CP.V 2068, Fig. 4) and the rostral end of lower
jaw (CP.V 2070, Fig. 4); incomplete mid-cervical
vertebra (CP.V 2445); mid-cervical vertebra, tibia
(shaft) and rib (CP.V 2317); scapulae (CP.V 2004
- right, 2075 - left, 2339 - right); coracoid (CP.V
2083 - left); humerus (CP.V 1011 - right); ulnae
(CP.V 2073 right, 2074 left, 2077 right, the latter
used for osteohistological analysis), radii (CP.V
2251 and 2247); and rst phalanges of the fourth
wing nger (CP.V 2242 right, 2248 left, 2373 right)
(Table II).
Referred specimens. Fragment of two
jaws (CP.V 2254; CP.V 2343); two incomplete
mandibular rami (CP.V 2071); one mid-cervical
vertebra (CP.V 2398), incomplete dorsal vertebrae
(CP.V 4181, CP.V 2234, 2316); elements of a large
wing (CP.V 5797); femora (CP.V 2081, 2245);
tibia (CP.V 2246); one large incomplete long
bone interpreted as the rst wing phalanx (CP.V.
2374) used for osteohistological purposes (see
osteohistology section) (Table III).
Type locality, horizon and age. `Cemitério
dos pterossauros´ site (53° 03′ 53,4″W; 23° 45′
34,5″S - contra Langer et al. 2019), Cruzeiro do
Oeste, Paraná State, Brazil; Bauru Basin, Caiuá
Group, Goio-Erê Formation Cretaceous (Milani et
al. 2007, Basilici et al. 2012, Batezelli 2015).
Diagnosis. Azhdarchoid pterodactyloid with
the following autapomorphies: short blunt ridge
on the dorsal surface of the posterior end of the
dentary; foramen on the ventral surface at the
anterior half of the proximal articulation of the rst
phalanx of digit IV; and foramen on lateral surface
of the ischium.
The new species can be further distinguished
from other azhdarchoid pterosaurs by the following
combination of characters: dorsal margin of the
premaxillae above the nasoantorbital fenestra
rounded; sagittal groove on the dorsal surface of
the premaxillae above the nasoantorbital fenestra;
ridge on the medial surface of the splenial; ventral
bar of the nasoantorbital fenestra thick; lateral
pneumatic foramen on mid-cervical vertebra large;
and strongly asymmetrical sternal articulation of
the coracoid.
DESCRIPTION AND COMPARISON
The material of Keresdrakon vilsoni is preserved
in a red coarse and friable sandstone (Figs. 3-9,
Tables I-III). The bones show dierent degrees of
compression, but most maintain at least some three-
dimensionality, an uncommon condition regarding
pterosaurs. Although some specimens were damaged
due to weathering, there are several elements with
breakages that have occurred prior or during the
TABLE I
Measurements (in mm) of the holotype (CP.V 2069) of
Keresdrakon vilsoni nov. gen., nov. sp.
skull 278*mm
mandible 361* mm
cervical vertebra, centrum 52 mm
sternum, sternal plate 82 mm
sternum, cristospine 36** mm, 17*** mm
scapula (right) 146* mm
femur (left) 189* mm
*preserved;
**anteroposterior;
***dorsoventral.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 7 | 32
Figure 3 - Holotype of Keresdrakon vilsoni gen. et sp. nov. (CP.V 2069). Skull and lower jaw are presented in right
lateral view. Abbreviations: cra - skull, cv - cervical vertebra, fe - femur, gas - gastralia, hu - humerus, man - mandible,
q - quadrate, ra - radius, ri - ribs, sca - scapula, st - sternum, ti - tíbia; l - left, r - right. Scale bar = 100mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 8 | 32
fossilization process. Based on the skulls and the
rst wing phalanges, at least three individuals are
recognized so far but the actual number must be
higher, particularly due to the fact that elements
of the new pterosaur were found in three dierent
levels throughout the section (Fig. 2).
The holotype (CP.V 2069) is the most
complete specimen (Fig. 3). The bones were found
associated but not articulated except for the upper
and lower jaw. Most elements are not fused such
as the scapula (found isolated and not fused to the
coracoid), the distal epiphysis of the right humerus,
and the pelvic elements. The following bones are
fused: premaxillae with each other and with the
maxillae, the splenial with the dentary, the opposing
dentaries, and the centrum with the neural arch of
the preserved mid-cervical vertebrae. As far as we
know from pterosaur ontogeny, CP.V 2069 likely
represents an animal that was between ontogenetic
stage (OS) 2 and 3 sensu Kellner (2015).
The holotype (CP.V 2069) also shows the best
preserved skull of the new species, formed by the
rostral end until part of the nasoantorbital fenestra
and a lower jaw that lacks the most distal portion
of the mandibular rami (Figs. 3-4a, c). Additional
cranial material consists of the anterior portion of
an upper jaw (CP.V 2068, Fig. 4a) and part of a
mandibular symphysis (CP.V 2070, Figs. 4d, e).
Two additional jaw fragments (CP.V 2254; CP.V
2343) and incomplete mandibular rami (CP.V
2071) are also tentatively referred to this species.
Based on these specimens, Keresdrakon
vilsoni is toothless and bears a low skull. The
rostrum is elongated, longer than that of any
tapejarid (Wang and Zhou 2003a, Lü et al. 2006,
Kellner and Campos 2007, Pinheiro et al. 2011,
Kellner 2013), chaoyangopterid (Wang and
TABLE II
Measurements (in mm) of the paratypes of Keresdrakon vilsoni nov. gen., nov. sp.
skull, rostral end CP.V 2068 197* (length)
lower jaw, mandibular symphsis CP.V 2070 183* (length)
mid-cervical vertebra, centrum CP.V 2445 56 (length)
scapula (right) CP.V 2004 163 (length)
coracoid (left) CP.V 2083 109** (length)
humerus (right) CP.V 1011 173 (length)
ulna (right) CP.V 2073 224 (length)
ulna (left) CP.V 2074 223 (length)
ulna (right) CP.V 2077 227 (length)
Radius CP.V 2251 196 (length)
Radius CP.V 2247 213 (length)
1st wing phalanx (right) CP.V 2242 228* (length), 36*** (width)
1st wing phalanx (left) CP.V 2248 367 (length), 37*** (width)
1st wing phalanx (right) CP.V 2373 242* (length), 39*** (width)
*preserved;
**from tubercle to sternal articulation;
***width medial articulation proximal.
Obs. scapulae (2075 and 2079) and ulnae (2073 & 2074) might belong to the same individual.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 9 | 32
Zhou 2003b, Lü et al. 2008) and the azhdarchid
Zhejiangopterus linhaiensis Cai and Wei 1994, but
shorter than that of the azhdarchid Quetzalcoatlus
sp. (Kellner and Langston 1996). The rostrum ends
in a pointed tip. The dorsal margin of the rostrum
until the anterior half of the nasoantorbital fenestra
is slightly sigmoid, diering in this respect from
all other pterodactyloids. The ventral margin is
slightly curved downwards but not as in tapejarines
(Kellner and Campos 2007). It lacks the large
quantities of foramina that are commonly observed
in tapejarids, including Caiuajara (Manzig et al.
2014). Occlusion of jaws form no gap, a dierent
condition from tapejarines (Kellner and Campos
2007).
The anterior angle of the nasoantorbital
fenestra (CP.V 2068 ~19.3°; CP.V 2069 ~22.5°)
is more acute than in other azhdarchoids except
for Quetzalcoatlus sp. (~15.8°, see Kellner and
Langston 1996). In lateral view, the ventral bar of
this opening formed by the premaxillae/maxillae
is thicker than in other azhdarchoids, except in
Thalassodromeus (Kellner and Campos 2002, Pêgas
et al. 2018). Although not complete, it is unlikely
that this cranial opening is as large as observed in
the tapejarids (Kellner and Campos 2007) or high
as in chaoyangopterids (Lü et al. 2008).
There is no evidence of a premaxillary
sagittal crest until the anterior margin of the
nasoantorbital fenestra, and it is unknown if such
a structure, which is a common feature among
azhdarchoids (Kellner and Langston 1996, Wang
and Zhou 2003a, Kellner and Campos 2007, Lü
et al. 2008), was present more posteriorly. Above
the anterior portion of the nasoantobital fenestra,
the premaxillae have a rounded dorsal margin and
display a sagittal groove (Figs. 3-4a). Inside this
cranial opening, the premaxillae are fused, have
laterally raised borders and form medially a at
surface, lacking the ridge present in Caiuajara
(Manzig et al. 2014). No suture with the maxillae
is visible. The palate is slightly concave and gets
more attened posteriorly, lacking any ventral ridge
as in thalassodromines (Kellner and Campos 2007)
or an expansion close to the anterior opening of the
nasoantorbital, which is diagnostic for tapejarines
(Kellner and Campos 2007). On the lateral side, a
longitudinal groove is observed.
An incomplete right quadrate (CP.V 2069) is
preserved, showing that it is a long rod-like bone
that has a thin medial flange (incomplete) and
laterally shows an elongated groove probable the
articulation for the quadratojugal.
The lower jaw is long and ends in a pointed
tip (Figs. 3, 4). As common in pterodactyloids,
the main element is the dentary, which fuses into
a symphysis. The occlusal (=dorsal) surface is
pierced by several foramina, which are more than
those of the upper jaw, but much fewer than those
in tapejarines (Kellner and Campos 2007, Andres
et al. 2014, Manzig et al. 2014) and similar to the
low number present in basal tapejarines (Kellner
2013, Pêgas et al. 2016). The ventral surface of
the symphysis is blunt and bears a small and thick
TABLE III
Measurements (in mm) of the referred specimens of Keresdrakon vilsoni nov. gen., nov. sp.
femur CP.V 2245 83* (length), 93** (length)
tibia CP.V 2246 154* (length)
1st wing phalanx CP.V 5797 322* (length) , 55*** (width)
mid-cervical vertebra, centrum CP.V 2398 38 (length)
*preserved;
** estimated;
***width medial articulation proximal.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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dentary crest. It diers from the deeper lower jaw
at the posterior end of the mandibular symphysis
of Argentinadraco (Kellner and Calvo 2017). The
occlusal surface is anteriorly attened and becomes
slightly concave posteriorly. A medial ridge starts
at the region corresponding to the end of the
dentary crest and runs at least for 40 mm (up to
65 mm) until almost reaching the posterior dorsal
end of the symphysis. Such a dentary dorsal ridge
has never been reported before in pterosaurs so
far. Argentinadraco bears two mandibular ridges
separated by a depression and laterally boarded by a
sulcus, diering from the condition of Keresdrakon.
Although the mandible is not complete, the
symphysis in the holotype (CP.V 2069) has reached
about 220 mm and corresponded up to 46% of the
estimated mandible length (~470mm). Despite the
fact that the exact posterior limit of the dorsal portion
of the mandibular symphysis cannot be established,
it seems not to extend further posteriorly relative
to the ventral end, neither to develop a symphyseal
shelf, diering from several azhdarchoids (Kellner
and Langston 1996, Vullo et al. 2012, Kellner 2013,
Pêgas et al. 2016). The typical tapejarine step-like
dorsal margin of the mandibular symphysis (Kellner
and Campos 2007) is absent. At the most posterior
Figure 4 - Skull and lower jaws of Keresdrakon vilsoni gen. et sp. nov. (a) Incomplete skull showing the rostral part, in left lateral
view (CP.V 2068), (b) incomplete lower jaw (CP.V 2069 part of the holotype) in left lateral and (c) dorsal views, (d) anterior
portion of a dentary (CP.V 2070) in left lateral and (e) dorsal views. Abbreviations: d - dentary, dcr - dentary crest, fo - foramina, gr
- groove, m - maxilla, naof - nasoantorbital fenestra, pm - premaxilla, rid - ridge, spl - splenial; l - left, r - right. Scale bar = 50mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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preserved end of the right mandibular ramus (CP.V
2069), the medial portion of the lower jaw can be
observed showing the splenial. This bone is very
thin and shows a blunt longitudinal ridge that does
not extend anteriorly.
Few cervical vertebrae are preserved and
might belong to distinct individuals (Fig. 5). The
elements from the middle series are sub-equal in
length, with the centrum longer than wide but not
to the same degree as in archaeopterodactyloids,
chaoyangopterids and azhdarchids (Nesov 1984,
Howse 1986, Kellner 2003, Andres and Ji 2008,
Lü et al. 2008, Leal et al. 2018). They bear
developed postexapophyses and hypapophysis. On
each side of the hypapophysis, small projections
- the preexapophysis - are present but not as
developed as in the azhdarchid Eurazhdarcho
(Vremir et al. 2013). This structure corresponds to
a ridge identied in an azhdarchid middle cervical
vertebra from Morroco (Rodrigues et al. 2011)
and the preexapophyseal articulations reported in
the pteranodontoid Pteranodon (Bennett 2001).
Although not reported, they are present in at least
some tapejarines, including Tapejara (Wellnhofer
and Kellner 1991) and Caiuajara (Manzig et al.
2014) (AWAK pers. obs.). They have not been
reported in thalassodromines (Aires et al. 2013)
and anhanguerids (Wellnhofer 1985, 1991).
The neural spine is tall and blade-like (Fig. 5).
The centrum is laterally pierced by a pneumatic
foramen, which is absent in chaoyangopterids (Lü
et al. 2008) and azhdarchids (Howse 1986). The
size of this pneumatic foramen is comparable to
the one found in anhanguerids (Wellnhofer 1985,
1991, Buchmann and Rodrigues 2019), and is much
larger than that in the pteranodontoid Pteranodon
(Bennett 2001) and tapejarids (e.g., Aires et al.
2013). There are also three pneumatic openings
on the anterior and posterior articulation surfaces
in some vertebrae – one above and one on each
side of the neural canal (CP.V. 2445, CP.V 2317;
Fig. 5g). In one mid-cervical element, the lateral
pneumatic openings at the anterior articulation
are reduced or absent (Fig. 5d). In CP.V 2445, the
neural arch on the left side is broken, revealing that
the inner part of the vertebra is hollow and has the
neural canal encased by a bony tube supported by
trabeculae (Fig. 5f). Such a construction has been
previously observed in one undescribed tapejarid
(Kellner 2006) and might be a general feature of
at least derived pterosaurs. This vertebra (CP.V
2445) also displays one foramen on each side of
the hypapophysis. No cervical rib was found in the
mid-cervical elements.
The sternum (CP.V 2069) is a large plate-like
and thin quadrangular bone (Figs. 3, 6). During
the collecting process the sternal plate (Fig. 6a)
was separated from the anterior portion of the
sternum (Figs. 6b, c). The cristospine is shallow and
elongated, with a blunt anterior and ventral margin.
At the base of the cristospine on the dorsal surface
is a large foramen (Figs. 6b, c). Several elements
of the thin “V” shaped gastralia are preserved. The
scapula is an elongated bone with a straight shaft
and a attened and elongated proximal articulation
(Fig. 7j). It shows a well-developed tuberculum
at the lateroposterior margin, similar to that of
Caupedactylus (Kellner 2013). On the lateral
surface above the glenoid this bone shows a marked
depression. The sole coracoid (CP.V 2083) attributed
to this species is incomplete, lacking the glenoid
portion (Figs. 7h-i). The developed coracoidal ange
as the one reported in some azhdarchids (Kellner
and Langston 1996) is absent. However, there is a
broad tubercle on the ventroposterior margin (Fig.
7h), a feature commonly observed in tapejarids
(Kellner 2013). The articulation with the sternum is
dorsoventrally attened, lacks a posterior expansion
and is strongly concave. It further has the posterior
portion more developed than the anterior one, giving
it an asymmetric outline that, to our knowledge,
has not been reported in any other pterosaur before
(Figs. 7h-i).

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Figure 5 - Cervical vertebrae of Keresdrakon vilsoni gen. et sp. nov., CP.V 6495 in (a) ventral, (b) right lateral, (c)
dorsal and (d) anterior views; CP.V 2445 in (e) ventral, (f) dorsolateral, (g) posterior views. Note the ossied tube
that encloses the neural cannal in (F) marked by an arrow. Abbreviations: con - condyle, fo - foramen, fopn - foramen
pneumaticum, hyp - hypapophysis, nc - neural canal, ns - neural spine, poex - postexapophysis, poz - postzygapophysis,
prex - preexapophysis, prz - prezygapophysis, tra - trabeculae. Scale bar = 20mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Overall, the humerus (Figs. 7d-g) shows a
similar shape to the one of Caupedactylus (Kellner
2013). The deltopectoral crest (CP.V 1011) is long
and quadrangular in lateral view, with parallel
margins. It is proximally placed and directed
ventrally, curving gently inwards. While there is
no pneumatic foramen on the dorsal surface of
the proximal portion, a large one can be found
piercing the ventral surface, placed at the base of
the deltopectoral crest (Fig. 7f), which is more
developed than in Caupedactylus (Kellner 2013).
The ulna is a long bone with the proximal
and distal articulations slightly twisted relative
each other. In all of these elements attributed to
Figure 6 - Sternum of Keresdrakon vilsoni gen. et sp. nov. (CP.V 2069, part of the holotype). (a) ventral, cristospine in dorsal (b)
and (c) right lateral views. Abbreviations: afc - articular facet for coracoid, cs - cristospine, fo - foramen, stp - sternal plate Scale
bars = (a) and (b) 50mm, (c) 20mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Figure 7 - Keresdrakon vilsoni gen. et sp. nov. (a) complete left rst phalanx of manual digit IV (CP.V 2248), (b)
proximal articulation of left rst phalanx of manual digit IV (CP.V 2248), (c) proximal articulation of right rst phalanx
of manual digit IV (CP.V 2373); right humerus (CP.V 1011) in (d) medial, (e) dorsal, (f) ventral and (g) lateral views;
left incomplete coracoid in (h) ventral and (i) dorsal views, (j) scapula in dorsal view. Abbreviations: dpc - deltopectoral
crest, fopn - foramen pneumaticum, tucor - coracoidal tuberculum. Scale bars = (b) and (c) 10mm, all others 50mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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this species, there is a marked depression on the
posterior surface at the proximal articulation (CP.V
2073, CP.V 2077) showing that the ulnar epiphysis
was unfused in these specimens (Fig. 9c). A
developed foramen pierces the anterior surface of
the proximal articulation. The distal articulation is
attened anteroposteriorly and shows a small ridge
along the dorsal margin of the anterior surface.
Although no radius and ulna can be condently
attributed to the same individual, in those specimens
where both bones have about the same length, the
diameter of the radius is about half that of the ulna,
a common feature within azhdarchoids (Kellner
2003). The distal articulation of the radius has a
attened posterior surface, which is pierced by a
pneumatic foramen, and a more irregular anterior
surface that shows a long blunt ridge (anterior
tubercle) at the lower ventral portion.
The rst phalanges of the fourth wing nger
that are attributed to Keresdrakon lack the extensor
tendon process, which shows that it was unfused
in all specimens (CP.V 2242, 2248, 2373; Figs.
7a-c). The shaft of the phalanges is slightly bowed
anteriorly, with a concave anterior margin and a
convex posterior one (Fig. 7a), a feature that has
been observed in dsungaripterids (Wellnhofer
1978) and some tapejarines (Eck et al. 2011). These
elements show a pneumatic foramen on the ventral
side of the proximal articulation situated close to
the posterior margin. All three also show a second
pneumatic foramen closer to the anterior margin
(Figs. 7b, c), which has never been reported in any
pterosaur before. In some specimens this foramen
is quite clear, while in others it is more dicult to
observe due to compression.
The holotype (CP.V 2069) also shows the
remains of a pelvic girdle (Fig. 8). The ilium is an
elongated bone with a developed postacetabular
process that has the anterior projection particularly
expanded, as observed in some tapejarids (AWAK
pers. obs.). This bone forms most of the acetabulum,
a common feature in derived pterosaurs (Fig. 8a).
The pubis is a dorsoventrally elongated bone
with a stout dorsal portion that contacts the ilium,
followed by a thin bonny plate that gently curves
medially (Figs. 8b, c). The anterior portion of
this bony plate further bends laterally to form the
anterior opening of the pelvic canal. The ventral
margin of the pubis is concave, while the posterior
margin that forms the contact surface with the
ischium is gently convex. This bone is perforated
by a well-developed oval obturator foramen whose
distal margin is formed by the ischium. Dorsal to
this foramen the pubis forms a comparatively thick
bony bar that has a convex posterior articulation
where it joins the ischium. The obturator foramen
in this species is similar in size at least to some
tapejarines (Eck et al. 2011), but larger compared
to most other groups of pterosaurs as, for example,
anhanguerids and pteranodontids (Wellnhofer
1978, 1991, Bennett 2001, Naish et al. 2013). The
ischium is a subtriangular plate that gently curves
medially (Figs. 8d, e). The anterior and posterior
margins are almost straight, while the ventral border
is slightly concave. The anterodorsal corner has a
Figure 8 - Keresdrakon vilsoni gen. et sp. nov., pelvis (CP.V
2869, part of the holotype), (a) left ischium in lateral view; right
pubis in (b) medial and (c) lateral views; right ischium in (d)
lateral and (e) medial views. Abbreviations: ac - acetabulum,
fo - foramen, gas - gastralia, obfo - obturator foramen. Scale
bar = 50mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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concave articulation surface that receives the dorsal
part of the pubis, while the posterodorsal corner is
displaced medially. On the lateral surface there is
a small foramen, which has not been reported in
other pterosaurs (Wellnhofer 1978, 1991, Bennett
2001, Naish et al. 2013).
The femur is bowed anteriorly (Fig. 3). Its
proximal articulation is made by a well-developed
femur head with a constricted neck that is set from
the shaft at ~135°. The femur head forms a convex
rounded surface with a suboval outline and lacks
a medial notch observed in some pterodactyloids.
A pneumatic foramen is present on the posterior
surface between the femur head and the triangular
greater trochanter. The tibia is a long and much
thinner element than the femur. No fibula was
found suggesting that this bone was not fused in
the material recovered from the new species.
OSTEOHISTOLOGY
In order to assess a preliminary histological analysis
of Keresdrakon vilsoni, two bones were sectioned:
one ulna (CP.V 2077) and one incomplete portion
of a large element lacking articulations (CP.V
2374), interpreted as the rst wing phalanx (Fig.
9). Overall, the osteohistological pattern is very
similar in both samples, showing fibrolamellar
primary tissue, a feature observed in most
pterosaurs (de Ricqlès et al. 2000, Prondvai et al.
2012, Eleutério et al. 2016). The cortex thickness
varies from 410 μm in the rst wing phalanx (CP.V
2374) to 850 μm in the ulna (CP.V 2077). Bone
microstructure shows dispersed osteocytes lacunae
in the cortex with some plexiform and anastomosed
canals randomly deposited.
The ulna (CP.V 2077) shows some vascular
canals accessing the periosteal surface (Fig. 9d),
a specific condition for juvenile to sub-adult
individuals (Steel 2008). There are no structures
throughout the entire bone circumference that point
to an advanced maturity of this individual, such as
growth marks, bone remodeling structures or an
external fundamental system (Steel 2008, Kellner
et al. 2013, Andrade et al. 2015). Furthermore,
the absence of the endosteal lamella suggests that
this bone belongs to a juvenile. In Hamipterus and
some anhanguerid pterosaurs the size variation is
reected in the osteohistological pattern of each
bone (Sayão 2003, Eleutério et al. 2015, Wang et al.
2014), which establishes a correlation between size
dierence and ontogenetic development (Wang et
al. 2014, 2017). The osteohistological features of
this specimen are consistent with a juvenile but not
Figure 9 - Osteohistological sections of Keresdrakon
vilsoni gen. et sp. nov. appendicular elements. Incomplete
first wing phalanx of digit four (CP.V 2374) (a) and
osteohistological cross section of the diaphysis; left ulna (CP.
V 2077) (c) and respective osteohistological cross section of
the diaphysis. Abbreviations: lag - line of arrested growth, vc
- vascular canal. The yellow arrows point where the samples
were taken. Scale bar = (a) and (c) 50mm, (b) and (d) 200µm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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a neonate (see Wang et al. 2017 for histological
structures of neonates and embryos). Several
grains of silica and quartz ll the inner medullary
cavity. These grains have possibly been deposited
during the bone transport process, pointing to bone
fragmentation prior to fossilization.
The most different pattern among samples
belongs to the first wing phalanx (CP.V 2374),
which has a unique growth mark located in the
deep portion of the cortex (Fig. 9b). The presence
of cyclical growth marks is continuous and partly
caused by endogenous physiological processes
(Eleutério et al. 2015), with lines of arrested growth
being common in vertebrates as general. However,
these marks are hardly found in pterosaurs, but
have been recorded in Cretaceous anhanguerids
(Sayão 2003, Eleutério et al. 2015) and Jurassic
pterosaurs (Padian et al. 2004). The presence of
these growth marks suggests that this bone belongs
to an ontogenetically less developed individual
compared to others.
PHYLOGENETIC RESULTS
Phylogenetic analysis resulted in 6 most-
parsimonious trees (MPTs), with 341 steps, a
consistency index of 0.66 and retention index
of 0.87. Azhdarchoidea is supported by the
following synapomorphies: character state 7(2)
- a dorsoventrally elongated orbit (piriform);
12(3) - slit-like lower temporal fenestra; 56(2) - a
cranio-mandibular articulation under the anterior
margin of the orbit; and 75(3) - a long extension
of the contact surface of opposing dentaries,
up to 55% the mandible length. Furthermore,
Keresdrakon vilsoni gen. et sp. nov. was recovered
as a sister taxon of the Tapejaridae (Fig. 10),
which would enable to recognize a non-tapejarid
lineage within the Tapejaromorpha (Andres et al.
2014). Tapejaromorphs are characterized by two
synapomorphies: character state 79(1) - a dentary
ossied sagittal crest; and 118(1) - coracoid with
developed tuberculum on the posteroventral
margin. The Tapejaridae (sensu Kellner 2003) is
supported by character state 27(1) - anterior portion
of the rostrum forming a high ossied plate, which
is absent in Keresdrakon.
DISCUSSION
Two species are considered sympatric when
they show the same or overlapping geographical
distribution, irrespective of their macrohabitat
(Rivas 1964), and there are several examples in
modern environments (e.g., Leal and Fleishman
2002, Luiselli 2006, Pigot and Tobias 2015). Even
though sympatry is normally used for closely related
species and associated with speciation (e.g. Mayr
1942, Diamond 1975, Van Valen 1976, Pigot and
Tobias 2015), there are cases in which this concept
is applied to phylogenetically more distant taxa (e.g.,
Magnusson 1985, Rao and Choudhury 1990, Soler
and Møller 1990, Choudhary et al. 2018).
Sympatry in the fossil record, particularly
considering extinct vertebrates, is dicult to be
established since dierent individuals that have
never shared the same habitat might be preserved
together in the same deposit as a result of time
averaging (e.g., Behrensmeyer et al. 2000). Bone
beds or the occurrence of specimens in close
associations are occasionally used as indication of
coexistence (e.g., Cabreira et al. 2016), although
caution is always needed (e.g., Rogers and Kidwell
2000). This situation is even more complicated in
pterosaurs due to the lack of bonebeds (e.g., Kellner
2017). So far, some authors assume sympatry for
these ying reptiles if species or genera occur in
the same stratigraphic unit (e.g., Upchurch et al.
2015, Longrich et al. 2018), but direct and more
conclusive evidences are dicult to obtain.
The bonebeds of Cruzeiro do Oeste, however,
represent a particular case that provides, to our
knowledge, the rst direct evidence for sympatry
in Pterosauria. Young (1973) has reported the

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Archaeopterodactyloidea
Pterodactyloidea
Ornithocheiroidea
Pteranodontoidea
Pteranodontidae
Nyctosauridae
Pteranodon longiceps
Tethydraco regalis
Nyctosaurus gracilis
Muzquizopteryx cohauilensis
Lanceodontia
Hongshanopterus lacustris
Istiodactylidae
Nurhachius ignaciobritoi
Istiodactylinae Istiodactylus sinensis
Istiodactylus latidens
Ikrandraco avatar
Ornithocheirae
Ornithocheirus simus
Hamipterus tianshanensis
Iberodactylus andreui
Hamipteridae
Anhangueria
Anhangueridae
Tropeognathus mesembrinus
Coloborhynchinae
Coloborhynchus clavirostrisUktenadactylus wadleighi
Caulkicephalus trimicrodon
Guidraco venator
Ludodactylus sibbicki
Anhanguerinae Lianoningopterus gui
Cearadactylus atrox
Maaradactylus kellneri
AMNH 22555
Anhanguera blittersdorffi
Anhanguera piscator
Pteranodontia
Haopterus gracilis
Lonchodraco giganteus
Camposipterus nasutus
Tapejaroidea
Dsungaripterus weii
Noripterus parvus
Dsungaripteridae
Azhdarcho lancicollis Quetzalcoatlus sp.
Zhejiangopterus linhaiensis
Jidapterus edentus
Shenzhoupterus chaoyangensis
Chaoyangopterus zhangi
Chaoyangopteridae
Azhdarchidae
Azhdarchoidea
Tapejaromorpha
Tapejaridae
Thalassodromeus sethi
Tupuxuara leonardii
Thalassodrominae
Tapejarinae
Caupedactylus ybaka
Aymberedactylus cearensis
Eopteranodon lii
Sinopterus dongi
'Huaxiapterus' benxiensis
'Huaxiapterus' corollatus
Europejara olcadesorum
Tupandactylus imperator
Caiuajara dobruskii
Tapejara wellnhoferi
Keresdrakon vilsoni gen. et sp. nov.
Tapejarini
a
ab
b
Cimoliopterus cuvieri
Figure 10 - Time-calibrated phylogenetic tree showing the relationships of Keresdrakon vilsoni gen. et sp. nov. within the
Pterodactyloidea. Intermittent bars show uncertain temporal range. Letters in intermittent bars indicate controversial age hypotheses
of the Goio-Erê Formation: (a) Albian-Aptian; (b) Turonian-Campanian. Outgroup relationships are not shown (see Holgado et al.
2019 - Supplementary Information for further details). Stratigraphic chart modied from Cohen et al. (2013).

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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occurrence of two taxa in the same deposits in
two localities in Wuerhe, but it is not clear if they
actually came from the same horizon, as is the case
of the material studied here. The `cemitério dos
pterossauros´ site also shows the co-occurrence of
a theropod dinosaur and two ying reptile species
that can condently be regarded as part of the same
paleobiological community (e.g., Figs. 11-16).
The majority of bones collected at the `cemitério
dos pterossauros´ site was found isolated, and only
very few can be assigned to the same individual.
This is also the case of Caiuajara dobruskii, with
only one articulated specimen and few others
presenting skeletal elements in close association.
The same condition is observed for the dinosaur
Vespersaurus, for which at least 12 individuals have
been discovered. Except for some feet, two arms
and few pelvic elements, all specimens known to us
were found disarticulated, albeit in close association
(AWAK and LCW pers. obs., specimens housed in
CENPALEO and in Cruzeiro do Oeste). The holotype
of Vespersaurus paranaensis is no exception, for
which the assignment to the same individual of a
few vertebrae from dierent parts of the body, pelvic
elements and pes seems to be unlikely.
The material of Keresdrakon vilsoni also shows
this taphonomic pattern: most elements were found
isolated and only a few were associated. The great
exception is the holotype (CP.V 2069). In terms of
paleoecological interpretations, the disarticulated
state of the material suggests that pterosaurs and
dinosaurs died around an oasis, with their skeleton
exposed for some time that leaded to disarticulation,
and then accumulated due to episodic events of
high energy such as desert storms.
At least four of such events could be identied
and resulted in bone beds. In three of them (from
base to top, A, B, and C, Fig. 2), the pterosaurs
Caiuajara dobruskii and Keresdrakon vilsoni, as
well as the dinosaur Vespersaurus paranaensis,
were found in close association (Figs. 11-16). The
repeating pattern of this close association argues
that Keresdrakon, Caiuajara and the dinosaur were
coeval. As was pointed out before (e.g., Kellner
2010, 2017), several pterosaurs were found in the
same deposit such as the Solnhofen Limestone
(Wellnhofer 1975, Bennett 1996), Yixian and
Jiufotang Formations (e.g., Wang and Zhou 2006),
Crato and Romualdo formations (e.g., Maisey
1991, Kellner 2006, Unwin and Martill 2007,
Vila Nova et al. 2011), Cambridge Greensand
(e.g., Unwin 2001, Rodrigues and Kellner 2013),
and Niobrara Chalk (Bennett 2001, 2003, Kellner
2010). However, the lack of stratigraphic control
and the absence of specimens showing more than
one individual preserved in close association,
conclusively demonstrating that dierent pterosaurs
were recovered from the exact same level within
these deposits, is a problem that has hampered
several biological questions regarding these ying
reptiles (e.g., Kellner 2010, Wang et al. 2014).
Still considering taphonomy, the number of
elements referable to Caiuajara by far outnumber
all others. There are well over 100 individuals
identied from this small pterosaur and although
some specimens clearly show the orientation of
elements indicating the action of water currents,
there is no specic predominance of one bone over
another. Only pelvic elements are scarcer, to which
there is no particular explanation.
The second more common fossil is
Vespersaurus, known by at least 12 individuals
(based on stratigraphy and number of elements of the
hind limb). Contrary to Caiuajara, most specimens
of this dinosaur recovered so far belong to the
hind limb (including feet) and the pelvis, with rare
remains of the skull and arms. Metatarsals II and
IV, which in the original description were described
based on pictures (Langer et al. 2019) indicating
that the specimen is lost or was destroyed, are very
compressed lateromedially (Fig. 13). There are also
many caudal vertebrae, several articulated (Figs.
11, 12). The amount of elements of Vespersaurus

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Figure 11 - Sample (CP.V 6559) from bonebed A of Figure 2, showing on the left
(a) side a partial skeleton of the pterosaur Caiuajara dobruskii and on the right
(b) the remains of the dinosaur Vespersaurus paranaensis. White line shows the
limits between the two specimens. Scale bar = 100mm.
paranaensis that occurs in three bonebeds, suggests
that this species might have been gregarious.
Bones of Keresdrakon vilsoni are the rarest
of the three species. Referring isolated bones
to a specific taxon can be difficult, as well as
distinguishing diagnostic from ontogenetic features,
which is a problem not restricted to pterosaurs (e.g.,
Müller 2017). Due to the morphological similarity
of postcranial elements of pterosaur groups in
general (e.g., Kellner 2003, Unwin 2003, Vila Nova
et al. 2015), it is possible that diculties might
arise in separating larger individuals (sub-adults) of
Caiuajara dobruskii from smaller ones (juveniles)
of Keresdrakon vilsoni. The anatomical dierences
in the cranial anatomy between both pterosaurs of
the `cemitério dos pterossauros´ site are striking,
but the main differences in the postcranial
skeleton are primarily restricted to the presence of
pneumatic foramina. While Keresdrakon vilsoni
possesses an additional pneumatic foramen on the
ventral surface at the anterior half of the proximal
articulation of the first wing phalanx (absent in
Caiuajara dobruskii), it lacks a pneumatic foramen
at the dorsal surface of the proximal articulation
of the humerus (present in tapejarine pterosaurs,
including Caiuajara). Both species show the lateral
surface of the mid-cervical vertebrae pierced by a
pneumatic foramen (sometimes two in Caiuajara),

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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which in Keresdrakon is much larger. Another
difference is the strongly asymmetrical sternal
articulation of the coracoid in Keresdrakon vilsoni,
not observed in several coracoids recovered from
Caiuajara dobruskii. Nonetheless, the minimum
number of Keresdrakon individuals recorded
so far is three. Based on the distribution of the
bones throughout the section the actual number
must be higher. Despite the small sample, no
preservation bias of any particular portion of the
skeleton is detectable, with cranial and postcranial
elements being recovered. There is also no specic
taphonomic reason for the comparatively low
number of preserved elements of this pterosaur,
which might have been the least represented of
the three species that occurred in this environment
(not including the lizard Gueragama). Based on
the present number of specimens, Keresdrakon
vilsoni might have had a solitary behavior and
Figure 12 - Sample (CP.V 7228) from bonebed A of Figure 2 showing the close association of a
femur of Caiuajara dobruskii (a) and the incomplete tail and forelimb (including partial manus) of
Vespersaurus paranaensis (b), separated by the white line. Scale bar = 100mm.
was not gregarious as inferred for the dinosaur and
Caiuajara.
Lastly, the lizard Gueragama sulamericana,
known from two fragmentary specimens
only (Simões et al. 2015), is the sole other
taxon recognized so far from the `cemitério
dos pterossauros´ site. Even though the exact
stratigraphic level from where this material came
from is unknown, this lizard was most likely part
of the same paleobiological community of the
dinosaur and the pterosaurs.
Sedimentological data supports the
interpretation that the Goio-Erê Formation was
formed in a desert environment with interdunal
wetland (Milani et al. 2007, Fernandes et al.
2009). Whilst Caiuajara dobruskii most likely
was a frugivore, a feeding behavior suggested for
tapejarines in general (Kellner 1989, Wellnhofer
and Kellner 1991, Wang and Zhou 2003a, Vullo

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Figure 13 - Paratype of Caiuajara dobruskii (CP.V 1003) (a) and a partial articulated hind limb of Vespersaurus paranaensis with
tibia, bula, tarsals (including astragalus) and metatarsals on the upper right corner (b). This specimen was collected from bonebed
C of Figure 2. White line shows the limits of the two specimens. Scale bar = 100mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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et al. 2012), this does not seem to have been the
case of Keresdrakon vilsoni. Taken into account
that deserts tend to have limited resources, niche
partitioning concerning these pterosaurs would
be feasible, particularly if they were sympatric,
which is considered here. Therefore, we can infer
that Keresdrakon vilsoni might have behaved as
an opportunistic predator or a scavenger (Fig. 17).
According to previous studies, a long and laterally
attened rostrum like the one of Keresdrakon is
appropriate to support low bite pressures restricted
to the jaw tips and the straight jaw margins, as has
been proposed for azhdarchids (Witton and Naish
2008). Therefore, subjugation of larger prey, such
as the dinosaur Vespersaurus, might have been
more dicult for this pterosaur despite its larger
Figure 14 - Sample (CP.V 1007) from bonebed level C of Figure 2, showing the close association of Caiuajara
dobruskii (a) and Vespersaurus paranaensis (b) separated by the white line. Scale bar = 100mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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Figure 15 - Sample (CP.V 5697) from bonebed C of Figure 2, showing on the right (a) a partial skeleton of the Caiuajara dobruskii
the left (b) elements of Keresdrakon vilsoni gen. et sp. nov. separated by the white line. Scale bar = 100mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 25 | 32
size, which could better handle smaller or immobile
food items such as carcasses. This feeding behavior
is observed in the extant marabou stork (Kahl 1966)
Leptoptilos crumenifer (Lesson, 1831). The feeding
preference of this bird comprises mainly carrion and
scraps, but it will opportunistically eat almost any
animal matter that it can swallow, including small
mammals and reptiles such as crocodile hatchlings
and eggs (Hancock et al. 1992). Considering the
little diverse fossiliferous record of the Caiuá
Group at the `cemitério dos pterossauros´ site,
Keresdrakon could probably prey on small lizards
such as Gueragama sulamericana. According to
Simões et al. (2015) the latter is assigned to have
presented the same habit as that of modern agamid
lizards in arid regions, which is to live in burrows to
avoid the arid weather. Additionally, Keresdrakon
might have also feed on eggs, younglings or even
juveniles of Caiuajara dobruskii, which was the
predominant species in this region during part of
the Cretaceous.
Regarding carrion feeding hypothesis, so far
there have been only Caiuajara and Vespersaurus
coming from these layers. Although admittedly
speculative, it is most likely that Keresdrakon
might have fed on their carcasses, particularly
on that of the dinosaur. As for Vespersaurus, its
primary food resource might have been Caiuajara,
which is found in large numbers in this deposit.
The lateral surface of the rostral end of the
skull of CP.V 2068 is quite rough (unlike the mild
condition observed in CP.V 2069), suggesting
that this specimen could have been exposed
before burial. The roughness aspect of the bone
surface is considered as an indicator of ontogeny
in pterosaurs (Bennett 1993, Steel 2008). In the
Pteranodon specimens, this roughness (grain
pattern for Bennett 1993) is only present in some
specimens with non-ossied epiphyses, reinforcing
the hypothesis that this characteristic is present in
juveniles. Both samples analyzed for histological
studies in Keresdrakon had open vascular canals in
the periosteal region (CP.V 2077 and CP.V 2374),
which is also an osteohistological characteristic
pointing to juveniles (de Ricqlès et al. 2000, Steel
2008). Therefore, features such as open canals in
the periosteum and the roughness or granulation
patterns endorse the interpretation of these
specimens between ontogenetic stages OS2 and
OS3 of Kellner (2015).
The few elements of Keresdrakon vilsoni
analyzed show a distinct osteohistological pattern
Figure 16 - Sample (CP.V 2374) from bonebed C of Figure 2,
showing two caudal vertebrae from Vespersaurus paranaensis
(a), the diaphysis of a large rst phalanx of manual digit IV of
Keresdrakon vilsoni gen. et sp. nov. (b), and bones of Caiuajara
dobruskii (c), separated by the white line. Abbreviations: cdr
- caudal vertebrae, ph1d4 - rst phalanx of manual digit IV.
Scale bar = 100mm.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 26 | 32
Figure 17 - Reconstruction of the paleoenvironment showing the possible interaction of the vertebrate fauna recovered from the `cemitério dos pterossauros´ site. See text
for details. Artwork by Maurilio Oliveira.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
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from that of Caiuajara dobruskii. The latter present
a highly vascularized plexiform tissue (Sayão et al.
2018), absent in the bones of Keresdrakon studied
here, which have a low vascularized cortex, with
few vascular canals connected (anastomosed).
Although both taxa present brolamellar complexes,
the plexiform tissue of Caiuajara has additional
radial connections between vascular canals. Both
types of histological features are indicative of fast
growth rates (Chinsamy-Turan 2005), although
the plexiform tissue is considered to have slightly
denser vascular canals than those of the laminar
tissue (Francillon-Vieillot et al. 1990). Thus, it is
not possible to establish dierences in growth rates
between the specimens analyzed of both pterosaur
species based only on their vascular arrangement.
In any case, the bones studied here indicate high
growth rates for both species.
Regarding bone maturity, Caiuajara shows
some signs of remodeling (Sayão et al. 2018)
represented by secondary osteons in the fourth
metacarpal (CP.V 2061), which are absent in both
Keresdrakon samples. Although this difference
may be related to a sampling problem, it suggests
that the population of Caiuajara may present
individuals slightly more ontogenetically developed
than Keresdrakon. Fused scapulocoracoids and
several rst wing phalanx with the extensor tendon
process fused agrees with this supposition. Further
osteohistological analyzes are needed to support
this observation.
Comparisons with Tupuxuara leonardii
(Iwaki specimen) and Caupedactylus (Kellner
2013), particularly regarding the humerus length,
suggest that Keresdrakon vilsoni had a wingspan
of approximately 3 m, quite larger than that of
Caiuajara dobruskii (Manzig et al. 2014: 0.65 to
2.35 m). Taking into account that they are young
individuals this proportion could be even higher.
CONCLUSIONS
The coexistence of fossil vertebrates, including
pterosaurs, are hard to be proven in the fossil record,
specially cases of sympatry. Regarding pterosaurs,
there must have been several places along deep time
where closely related species might have overlapped
and shared similar geographic distribution. The
challenge is to nd direct evidences of this. The
`cemitério dos pterossauros´ site represents the
co-occurrence of distinct pterosaur species in the
same bone beds, showing that Keresdrakon and
Caiuajara were coeval. This site also shows that
the dinosaur Vespersaurus paranaensis shared this
ancient desert environment with these two ying
reptiles. While Caiuajara, despite being small and
therefore potentially having a more fragile skeleton,
by far outnumber the other taxa and is one of the
few examples in the fossil record that might argue
for gregarious behavior in pterosaurs, Keresdrakon
vilsoni was scarcer and apparently represents a
species with solitary behavior. We advocate that
both specialized in dierent feeding items of this
most likely depauperate environment. Caiuajara
is regarded as being frugivorous and Keresdrakon
might have been an opportunistic predator or a
scavenger feeding at small animals or carcasses
such as that of Vespersaurus. The latter might have
made a living by hunting individuals of Caiuajara
dobruskii that were abundant. All three were part
of a paleobiological community that existed in this
region during part of the Cretaceous.
As has been pointed out before (Kellner
2012), the outcrops in the region of Cruzeiro do
Oeste, more specically deposits from the Caiuá
Group as the Goio-Erê formation, might turn out
to become the `Brazilian Mongolia´ in terms of
fossil vertebrates. The hundreds of fossils from two
pterosaur species and one theropod dinosaur, as well
as the occurrence of a lizard, endorse this potential.
It is also likely that the future might show additional
taxonomic groups like mammals and other reptiles.

ALEXANDER W.A. KELLNER et al. PTEROSAUR AND PALEOECOLOGY OF CRETACEOUS DESERT
An Acad Bras Cienc (2019) 91(Suppl. 2) e20190768 28 | 32
More eldwork and careful collection of specimens
might contribute to a better understanding of the
ecosystem of ancient Cretaceous deserts that,
despite its general depauperate conditions, had
areas where life could prosper.
ACKNOWLEDGMENTS
We would like to thank Valter Pereira da Rocha
(former Mayor of Municipality of Cruzeiro do
Oeste), João Gustavo Dobruski and his family,
Maristela Sanches Morcelli and Neurides de Oliveira
Martins, all residents of Cruzeiro do Oeste, for their
help during eldwork. Solange Salete Sprandel da
Silva, Luciano Bendlin, and Gabriel Bonetto Bampi
from the Universidade do Contestado are thanked
for supporting the research at CENPALEO. Vilson
Greinert is acknowledged for the preparation of
several specimens housed in CENPALEO and in
the Municipality of Cruzeiro do Oeste that greatly
contributed to several studies of fossil vertebrates
from this region. Kamila Bandeira (Museu
Nacional/UFRJ) has helped in the discussion of
Greek mythology. Maurilio Oliveira is thanked for
the reconstruction of the paleoenvironment of the
`cemitério dos pterossauros´ site. AWAK would
like to acknowledge Neurides de Oliveira Martins
for inviting him to teach the fossil vertebrate course
in August 2016 at Cruzeiro do Oeste. This course
trained several employees of the municipality as well
as teachers and students from local universities such
as the Universidade Estadual do Maringá (Paraná
State) and was the basis of a fossil preparation lab
in the city. Lastly, we would like to acknowledge
three anonymous reviewers for their comments and
suggestions that greatly improved the nal version
of this paper. This study was partially nanced by
the Fundação de Desenvolvimento Carlos Chagas
Filho de Amparo à Pesquisa do Estado do Rio de
Janeiro (FAPERJ #E-26/202.893/2015 to AWAK),
the Conselho Nacional de Desenvolvimento
Cientíco e Tecnológico (CNPq #420687/2016-5
and #313461/2018-0 to AWAK; #140789/2016-
2 to BH, #311715/2017-6 to JMS), the Fundação
Cearense de Apoio ao Desenvolvimento
Cientíco e Tecnológico (FUNCAP #BMD-0124-
00302.01.01/19 to RAMB) and the Coordenação
de Aperfeiçoamento de Pessoal de Nível Superior
- Brasil (CAPES) - Finance Code 001 (CAPES
#88887.162865/2018-00 to RAMB).
AUTHOR CONTRIBUTIONS
AWAK and LCW conceived and designed the
study and performed eldwork that resulted in the
collection of the material housed in CENPALEO
and in Cruzeiro do Oeste; AWAK, BH and JMS
wrote the main manuscript; LCW conducted the
geological study; BH and AWAK preformed the
phylogenetic analysis; RAMB and JMS did the
osteohistological analysis. All authors contributed
and reviewed the manuscript.
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