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Journal of Vertebrate Paleontology
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/ujvp20
The ontogenetic growth of Anhangueridae
(Pterosauria, Pterodactyloidea) premaxillary crests
as revealed by a crestless Anhanguera specimen
Rudah Ruano C. Duque, Felipe L. Pinheiro & Alcina Magnólia Franca Barreto
To cite this article: Rudah Ruano C. Duque, Felipe L. Pinheiro & Alcina Magnólia Franca Barreto
(2022): The ontogenetic growth of Anhangueridae (Pterosauria, Pterodactyloidea) premaxillary
crests as revealed by a crestless Anhanguera specimen, Journal of Vertebrate Paleontology, DOI:
10.1080/02724634.2022.2116984
To link to this article: https://doi.org/10.1080/02724634.2022.2116984
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Published online: 11 Oct 2022.
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ARTICLE
THE ONTOGENETIC GROWTH OF ANHANGUERIDAE (PTEROSAURIA,
PTERODACTYLOIDEA) PREMAXILLARY CRESTS AS REVEALED BY A CRESTLESS
ANHANGUERA SPECIMEN
RUDAH RUANO C. DUQUE,
1
*FELIPE L. PINHEIRO,
2
and ALCINA MAGNÓLIA FRANCA BARRETO
1
1
Laboratório de Paleontologia, Universidade Federal de Pernambuco (UFPE), Centro de Tecnologia e Geociências, Departamento
de Geologia, Av. Acadêmico Hélio Ramos s/n, Cidade Universitária, Recife, Pernambuco, 50740-530, Brazil, rudah.ruano@ufpe.br;
alcinabarreto@gmail.com;
2
Laboratório de Paleobiologia, Universidade Federal do Pampa, Rua Aluízio Barros Macedo, s/n. BR 290 - km 423, São Gabriel, Rio
Grande do Sul, 97307-020, Brazil, felipepinheiro@unipampa.edu.br
ABSTRACT—The Anhangueridae are a clade of toothed pterodactyloid pterosaurs, known from their characteristic
anteriorly expanded premaxillae and conspicuous rostral sagittal premaxillary and dentary crests. Most known
anhanguerids come from the Lower Cretaceous Romualdo Formation within the Araripe Basin of northeast Brazil. With
four currently valid genera and several specimens referred to the clade, anhanguerids are the most abundant and diverse
tetrapod group in the Romualdo Formation. However, some studies suggest this diversity may be overestimated, as many
taxa have been diagnosed based on subtle differences in their premaxillary crests, a structure argued to be either
ontogenetically variable or sexually dimorphic. Here we describe an anterior fragment of a gracile pterosaur rostrum that
possesses the single diagnostic feature of Anhanguera (fifth and sixth pairs of dental alveoli smaller than the fourth and
seventh), but lacks a sagittal crest. The affinities of the new fossil among other toothed pterosaurs were tested through
both cladistic and geometric morphometric approaches, which allow referral of the new specimen to Anhanguera.The
absence of a crest in the new specimen of Anhanguera suggests that this structure varies in terms of ontogeny and/or sex,
and that perhaps it was influenced by sexual selection.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP.
Citation for this article: Duque, R. R. C., F. L. Pinheiro, and A. M. F. Barreto. 2022. The ontogenetic growth of Anhangueridae
(Pterosauria , Pterodactyloidea) premaxillary crests as revealed by a crestless Anhanguera specimen. Journal of Vertebrate
Paleontology. DOI: 10.1080/10.1080/02724634.2022.2116984
INTRODUCTION
The clade Anhangueridae was proposed by Campos and
Kellner (1985) and, since then, its taxonomy has prompted contro-
versy, with several revaluations and propositions of synonymia,
nomina dubia and introduction of new genera (Kellner, 1990;
Kellner and Tomida, 2000; Fastnacht, 2001; Unwin, 2001;Rodri-
gues and Kellner, 2013;Andresetal.,2014; Pinheiro and Rodri-
gues, 2017; Longrich et al., 2018; Pêgas et al, 2019; Holgado and
Pêgas, 2020). Although published taxonomic works may disagree
in several aspects of anhanguerid definition and nomenclature,
they demonstrate that the group reached a considerable diversity
and geographic distribution during the Cretaceous. According to
the most recent propositions, the Anhangueridae consist of 18
species, divided into the taxa Tropeognathinae, Coloborhynchi-
nae, and Anhanguerinae, with specimens found in the U.S.A.,
Brazil, Morocco, England, China, and Australia (Holgado et al.,
2019; Holgado and Pêgas, 2020).
The Anhanguerinae is the Anhangueridae subclade in which
most of the Brazilian representatives are classified, all of them
coming from the Araripe Basin: Ludodactylus,Cearadactylus,
Maaradactylus, and Anhanguera. Among those, Ludodactylus
is the only genus thus far described for the Crato Formation,
and all the remaining were recovered from the Romualdo For-
mation. After the description of Anhanguera blittersdorffi
(Campos and Kellner, 1985), tens of anhanguerid skulls have
been collected and reported, being kept in scientific collections
around the world. As a rule, individual anhanguerid species
were described mostly based in subtle morphological discrepan-
cies in their premaxillary crests and overall skull proportions (see
Pinheiro and Rodrigues, 2017). However, albeit still not being a
consensus, it has been suggested by many authors (Bennett, 1992,
1994; Carpenter et al., 2003; Frey et al., 2003; Unwin, 2005;Lu
et al., 2011; Wang et al., 2014; Pinheiro and Rodrigues, 2017)
that the premaxillary crest in pterosaurs is a sexually selected,
dimorphic feature, being subject to ontogenetic variation and
not suitable as a diagnostic feature.
In a review of the genus Anhanguera, Pinheiro and Rodrigues
(2017) reanalyzed supposedly diagnostic features of
A. blittersdorffi,“A. araripensis,”“A. santanae,”“A. robustus,”
A. piscator, and A. spielbergi, revealing that most features pre-
viously used to define these species were problematic, as they
mainly referred to crest morphology and position, characters
proved to fall within the range of intraspecific variation. Accord-
ing to these authors, after the exclusion of sagittal crest charac-
ters from Anhanguera definition, the single feature kept for
diagnosing the genus was the fifth and sixth pairs of teeth
being smaller than the fourth and seventh ones. Pinheiro
and Rodrigues’(2017) reappraisal considered only three
species as potentially valid: A. blittersdorffi,A. piscator, and
A. spielbergi.
* Corresponding author
Color versions of one or more of the figures in the article can be found
online at www.tandfonline.com/ujvp.
Journal of Vertebrate Paleontology e2116984 (10 pages)
© by the Society of Vertebrate Paleontology
DOI: 10.1080/02724634.2022.2116984
Published online 11 Oct 2022
Here we present a new pterosaur specimen from the
Romualdo Formation, which comprises the anterior portion of
a long rostrum that, albeit lacking a sagittal premaxillary crest,
is consistent with its identification as Anhanguera. Phylogenetic
and geometric morphometric analyses were run in order to
recover the affinities of the new material, as well as to test the
validity of rostral dental alveoli size and distribution in the taxon-
omy of anhanguerids and similar taxa.
GEOLOGICAL SETTING
The Araripe Basin is arguably the most complex interior sedi-
mentary basin of northeastern Brazil, having its origins and evol-
ution related to the splitting of the African and South American
continents (Assine, 1992). It is limited to the north by the Patos
Lineament and to the south by the Farias Brito Fault, being
inserted over the Precambrian Borborema Province. Its area
covers the southern of Ceará, eastern of Piauí, and western of
Pernambuco states (Fig. 1A), with a 38°30′–40°55′W longitude
and 7°05′–7°50′S latitude (Viana and Neumann, 2002).
The Santana Group is composed by three sedimentary units,
from bottom to top: the Crato, Ipubi, and Romualdo formations
(Assine, 1992; Neumann and Cabrera, 1999). Among those, the
Crato and Romualdo Formations are the best known, as much
for their faciological complexity, as for their abundant and excep-
tionally preserved fossils. The Romualdo Formation, which had
its deposition between the Neoaptian and the Eoalbian, is
characterized by a sequence of claystone and dark gray/black
marine shales, with presence of several levels where limestone
concretions are abundant, most of them preserving fossils
within. The Romualdo Formation has produced the largest diver-
sity of pterosaurs of the Santana Group. Above the concretion-
bearing levels, the Romualdo Formation displays slim layers of
coquinas and cochinoid limestone (Assine et al., 2014).
The studied specimen comes from the southern region of the
Araripe Basin, in a locality known as “Sítio Zé Gomes,”
located in the homonymous district, Exu County (Fig. 1A),
western Pernambuco state. It was exposed on the surface,
within a shale layer over the cochinoid limestone beds
(Fig. 1B), uppermost portion of the Romualdo Formation. The
Sítio Zé Gomes has yielded a great fossil diversity, mainly
composed by fishes, identified as Vinctifer,Tharrhias,Rhacolepis,
Neoproscinetes,Notelops,Brannerion,Cladocyclus, and Axelro-
dichthys. A specimen of the testudine Araripemys barretoi was
FIGURE 1. A, map of the Araripe Basin, northeastern Brazil, highlighting the Exu County, Pernambuco, and the location of Sítio Zé Gomes (7°31′16′
′S, 39°34′18′′W); B, stratigraphic chart of Sítio Zé Gomes, displaying the level from where DGEO-CTG-UFPE 8283 was collected. Modified from
Duque and Barreto (2018:figs. 1–2).
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-2)
also recovered, as well as a previously described anhanguerid
pterosaur (Duque and Barreto, 2018).
MATERIAL AND METHODS
Institutional Abbreviations—AMNH, American Museum of
Natural History, New York, NY, U.S.A.; BSP, Bayerischen Staats-
sammlung für Paläontologie und Historische Geologie, Munich,
Germany; CAMSM, Sedgwick Museum, Cambridge University,
Cambridge, U.K.; CSRL, Centro Studi e Ricerche Ligabue,
Venice, Italy; DGEO-CTG-UFPE, Departamento de Geologia,
Centro de Tecnologia and Geociências, Universidade Federal de
Pernambuco, Recife, Brazil; IVPP, Institute of Vertebrate Paleon-
tology and Paleoanthropology, Chinese Academy of Sciences,
Beijing, China; IWCMS, Isle of Wight County Museum Service
at Dinosaur Isle, Sandown, Isle of Wight, U.K.; LINHM,Long
Island Natural History Museum, New York, NY, U.S.A.; MN,
Museu Nacional, Rio de Janeiro, Brazil; MPSC, Museu de Paleon-
tologia em Santana do Cariri, Santana do Cariri, Brazil; NHM,
The Natural History Museum, London, U.K.; NSM, National
Museum of Nature and Science, Tokyo, Japan; RGM,Nationaal
Ntuurhistorisch Museum, Leiden, Holland, the Netherlands;
SAO, Sammlung Oberli, St. Gallen, Switzerland; SMNK,Staa-
tliches Museum für Naturkunde, Karlsruhe, Germany; SMU,
Southern Methodist University, Dallas, TX, U.S.A.
Materials, Preparation, and Measurements
The specimen DGEO-CTG-UFPE 8283 consists of the
anterior portion of a slim and long pterosaur rostrum, deposited
in the scientific collection of the Geology Department, Center of
Technology and Geosciences of the Federal University of Per-
nambuco, Recife, Brazil.
The specimen was isolated from a typical Romualdo For-
mation limestone concretion using standard mechanical prep-
aration protocols (Santos, 1985; May et al., 1994). Measures
were taken with a digital universal stainless steel caliper 150
mm/6". Photographs were taken with a Canon EOS Rebel
Camera and edited with the software Adobe Photoshop® CC
and CorelDRAW® 2019.
Geometric Morphometrics
Two-dimensional geometric morphometrics was applied to test
the relevance of size and position of rostral dental alveoli in the
characterization and diagnosis of anhanguerids and closely
related taxa. In this framework, the analysis was also employed
to test morphological congruence between DGEO-CTG-UFPE
8283 and other specimens that compose the morphometric
dataset we assembled.
A total of 21 specimens were used in the analysis, these being:
the cimoliopterids Camposipterus nasutus (CAMSM B 54556),
Cimoliopterus dunni (SMU 76892), and Cimoliopterus cuvieri
(MHN 39409); two specimens of the hamipterid Hamipterus tian-
shanensis (IVPP V 18935 1 and MN 7536); the tropeognathines
Siroccopteryx moroccensis (LINHM 016) and Tropeognathus
mesembrinus (BSP 1987 I 46); the coloborhynchines Colobor-
hynchus clavirostris (NHM R 1822) and Uktenadactylus wadleighi
(SMU 73058); and the anhanguerines Caulkicephalus trimicrodon
(IWCMS 2002.189.1), Cearadactylus atrox (MN 7019-V), “Ceara-
dactylus”ligabuei (CSRL 12692/12713), Maaradactylus kellneri
(MPSC R 2357), Anhanguera sp. (AMNH 22555), Anhanguera
sp. (SMNK PAL 3895), Anhanguera sp. (NHM R 11978), Anhan-
guera sp. (SAO 16494), Anhanguera sp. (SMNK PAL 2302),
Anhanguera blittersdorffi(MN 4805-V), Anhanguera spielbergi
(RGM 401 880), and DGEO-CTG-UFPE 8283.
We used photographs of specimens in ventral view, based on
which 14 landmarks were plotted for each specimen. Landmarks
were taken from the anteriormost and posteriormost limits of
each of the seven first tooth alveoli. As such, landmarks reflect
the size, position, and orientation of alveoli, as well as their rela-
tive distribution throughout the alveolar margin. When alveoli
are anteriorly directed and cannot be seen in ventral view, their
correspondent landmarks were superimposed. The landmarks
were digitalized using the software TPSDig (Rohlf, 2010),
while all analyses were carried out using the MorphoJ software
package, version 1.06a (Klingenberg, 2011). After the Procrustes
superimposition, a Principal Component Analysis (PCA) was
used to investigate morphometric variation within the chosen
sample. As Coloborhynchus clavirostris (NHM R 1822) only pre-
serves its six anteriormost alveoli, missing landmarks were esti-
mated for this specimen by the use of the TPS method
(function estimate.missing) of the Geomorph package (R
environment) (Adams and Otárola-Castillo, 2013).
Phylogenetic Analysis
We assessed the relationships of DGEO-CTG-UFPE 8283
within the phylogenetic framework of Holgado et al. (2019), as
modified by Cerqueira et al. (2021). Scoring of DGEO-CTG-
UFPE 8283 in Cerqueira et al. (2021) data matrix (see the Sup-
plemental Data) resulted in a dataset composed by 61 oper-
ational taxonomic units (OTUs) and 146 characters. All
characters are non-additive and have the same weight. The
analysis was conducted by a heuristic search, using the tree bisec-
tion reconnection algorithm of TNT version 1.5 (Goloboff and
Catalano, 2016), with random seed and 100 replications (100
trees held by replicate). Bremer support values were later calcu-
lated, also using TNT 1.5.
SYSTEMATIC PALEONTOLOGY
PTEROSAURIA Kaup, 1834
PTERODACTYLOIDEA Plieninger, 1901
ANHANGUERIA Rodrigues and Kellner, 2013
ANHANGUERIDAE Campos and Kellner, 1985
ANHANGUERINAE Holgado, Pêgas, Canudo, Fortuny,
Rodrigues, Company, and Kellner, 2019
ANHANGUERA Campos and Kellner, 1985
ANHANGUERA sp.
(Fig. 2)
Material—Anterior fragment of a pterosaur rostrum, DGEO-
CTG-UFPE 8283.
Locality and Horizon—Romualdo Formation, Lower Cretac-
eous (Aptian/Albian), Santana Group, Araripe Basin, Exu muni-
cipality, Zé Gomes district (7°31′16′′S, 39°34′18′′W),
Pernambuco state, Brazil.
Preservation—At the time of the field prospection, DGEO-
CTG-UFPE 8283 had its largest portion still covered by lime-
stone matrix, forming a long carbonate concretion. At the
exposed portion, a large cavity filled with calcite crystals could
be observed, and a fragmented tooth was also evident at the
surface. After mechanical preparation, the specimen revealed
to be preserved in three dimensions, with no evidence of distor-
tion or flattening. Almost the whole left surface of the rostrum
was, however, eroded off prior to collection.
Description—As preserved, the specimen measures 143 mm in
its largest (longitudinal) extension, being 28.6 mm deep in its pos-
terior region. The outer bone wall was, as reported, largely
eroded off prior to collection, being extremely thin (about 0.3
mm thick) in its preserved portions. The specimen is triangular
in transverse section (Fig. 2) and, in lateral view, the rostrum
widens posteriorly, while tapering anteriorly. As a premaxillary
crest is absent, the tip of the rostrum is dorsoventrally flat,
being larger than deep in an anterior view.
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-3)
The dorsal surface of the fused premaxillae is anteriorly round,
sharpening posteriorly to form a keel. The suture between the
right premaxilla and the maxilla is visible as a faint line close
to the posterior limit of the specimen, fading at a region near
the seventh tooth position.
As mentioned above, the right side of the specimen is
better preserved, and 12 tooth alveoli are clearly visible com-
posing the right alveolar margin. The specimen bears a con-
spicuous palatal keel, deeper in its posterior end but fading
anteriorly, where the palatal surface becomes convex. The
first alveolus is anteriorly faced, and the rostrum shows an
anterior expansion that extends until the fifth alveolus. Pos-
terior to that, there is a subtly narrower area, where the
sixth and seventh alveoli are located. The right side of the
specimen is completely eroded, but there remains a fragmen-
ted tooth, still articulated to its socket, probably correspond-
ing to the second left element. The erosion made the tooth
root visible, its preserved part being straight, 22 mm long
and 5.4 mm wide, with a circular transverse section. Portions
of the posterior two teeth are also visible, anteroventrally
oriented but broken at their bases.
The fifth, sixth, and seventh alveoli are smaller than the
second, third, fourth, and eighth ones. From the first to the
eighth, the alveoli are mainly circular, the following four being
small and elliptical. The alveoli are increasingly spaced poster-
iorly (Table 1). The sagittal palatal crest begins right after the
seventh alveolus. The crest is well defined posteriorly, rivalling
the alveolar margin in deepness. Anteriorly, it fades to form
the convex anterior palatal surface.
Comparison—Specimen DGEO-CTG-UFPE 8283 can be
readily assigned to the Anhangueria (Rodrigues and Kellner,
2013) due to the presence of an anterior expansion of the pre-
maxillae and for having its larger teeth placed in the tip of the
rostrum (a feature that can be inferred by measuring alveolar
sizes). The Anhangueria includes Hamipterus,Iberodactylus
and the clade Anhangueridae.
FIGURE 2. DGEO-CTG-UFPE 8283 (Anhanguera sp.) in A, right lateral view; B, left lateral view; C, palatal view; D, dorsal view; E, posterior view; F,
rostral view. Scale bar equals 50 mm.
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-4)
Kellner (1996,2003) considered as synapomorphies of the
Anhangueridae: (1) Premaxillary sagittal crest confined to
anterior portion of skull; (2) Tip of premaxilla slightly expanded;
(3) Short, blade-like dentary sagittal crest. Specimen DGEO-
CTG-UFPE 8283, albeit displaying expanded premaxillae,
lacks a premaxillary crest, supposedly characteristic of the
Anhangueridae. In spite of that, DGEO-CTG-UFPE 8283
shows some diagnostic features of the Anhanguerinae, such as
an enlarged fourth premaxillary tooth, which is larger than the
fifth and sixth teeth and as large as (or larger) than the third
tooth (Holgado et al., 2019). In addition, the new specimen dis-
plays a feature considered to be synapomorphic to the genus
Anhanguera: the fifth and sixth alveolar pairs are smaller than
the fourth and seventh ones (Kellner, 2003; Pinheiro and Rodri-
gues, 2017). The taxonomic revision of Pinheiro and Rodrigues
(2017), also backgrounded by an extensive morphometric analy-
sis, considered only three Anhanguera species as valid, those
being: Anhanguera blittersdorffi,Anhanguera spielbergi, and
Anhanguera piscator.
Anhanguera blittersdorffiCampos and Kellner 1985, the type
species of Anhanguera genus, has its holotype (MN 4805-V) con-
sisting of an isolated skull (lacking the lower jaw) with a large
number of alveoli in the upper jaws (26 pairs) and a well-devel-
oped sagittal crest. Based on the fusion degree of cranial bones,
this specimen was referred as a mature individual (Kellner and
Tomida, 2000). As it seems, MN 4805-V and DGEO-CTG-
UFPE 8283 belong in the same genus, as both share the single
Anhanguera synapomorphy (see above). Actually, the most strik-
ing differences between the two specimens are related to the
presence of a premaxillary crest in MN 4805-V and the extension
of the palatal crest, which extends from the fifth to the ninth
alveoli in A. blittersdorffi.
A second Anhanguera species, Anhanguera spielbergi, is only
known by its holotype (RGM 401 880), which consists of a
large skull displaying an exceptionally deep, blade-like premaxil-
lary crest that begins in the rostral end of the skull and is better
developed than the one of Anhanguera blittersdorffiholotype
(MN 4805-V). The palatal keel of RGM 401 880 is as subtle as
the one of DGEO-CTG-UFPE 8283, extending from the fifth
to the ninth tooth pairs. Is also noteworthy that the skull of
AMNH 22555 (formerly assigned to “Anhanguera santanae”by
Wellnhofer, 1991) apparently lacks a prominent sagittal crest,
even though the dorsal margin of the premaxillae was eroded
off in this particular specimen (Pinheiro and Rodrigues, 2017).
The nine rostral-most tooth alveoli are preserved in AMNH
22555, their distribution throughout the upper jaws being very
similar to what is seen in DGEO-CTG-UFPE 8283. Also, its
palatal crest gently rises starting from the fifth pair of
alveoli, in a similar condition to what is displayed by
A. blittersdorffi.
In the holotype of Anhanguera piscator (NSM-PV 19892), the
extension of the sutures between the premaxillae and maxillae
cannot be discerned, in a similar condition to what is displayed
by DGEO-CTG-UFPE 8283. In spite of that, the A. piscator
holotype was most likely a juvenile at the time of death, as
demonstrated by the lack of fusion between several bones con-
sidered as ontogenetic proxies. According to Pinheiro and Rodri-
gues (2017), this would explain the low premaxillary crest in this
particular specimen. The fusion between maxillae and premaxil-
lae occurred early in pterosaur ontogeny, thus being a poor
choice as a proxy for ontogenetic development. The size of the
A. piscator premaxillary crest was proposed as diagnostic of
this species by Kellner and Tomida (2000), later disregarded by
Pinheiro and Rodrigues (2017). The holotype of A. piscator
still has its lower jaws in occlusion, preventing from viewing its
palatal morphology.
The specimen SAO 16494, formerly referred to Colobor-
hynchus araripensis by Veldmeijer et al. (2006) was later assigned
to Anhanguera sp. (Pinheiro and Rodrigues, 2017), and has a
well-developed premaxillary crest. SAO 16494 is similar to
DGEO-CTG-UFPE 8283 in having a palatal ridge starting pos-
terior to the seventh tooth pair. This condition differs from
several known Anhanguera skulls. As an example, specimen
NHM R 11978, which also has a well-developed premaxillary
crest, has a palatal crest that rises posterior to the eighth tooth
pair.
The Anhanguerinae Cearadactylus atrox (MN 7019-V) differs
from DGEO-CTG-UFPE 8283 for having its four most rostral
tooth pairs larger than the following ones. In addition, its
palatal ridge rises level with the fifth tooth pair, and the specimen
probably had a small sagittal premaxillary crest (Vila Nova et al.,
2014). An allegedly second Cearadactylus species, “Cearadacty-
lus”ligabuei, was probably based on a composite, and was inva-
lidated by Vila Nova et al. (2014).
Among the largest anhanguerid skulls known thus far stands
the holotype of Maaradactylus kellneri (MPSC R 2357). In this
species, alveolar pairs fifth, sixth and seventh are smaller than
the fourth and eighth, differing, thus, from Anhanguera.The
palate displays a low longitudinal ridge starting close to the
fifth tooth pair, and fading level with the 13th. Maaradactylus
kellneri bears a long and deep premaxillary crest (Bantim
et al., 2014). Tropeognathus mesembrinus, also known by large
skull material, has an exceptionally large premaxillary crest,
which extends until the anteriormost limit of the rostrum (Well-
nhofer, 1987). Similar to A. blittersdorffi, AMNH 22555, and
Maaradactylus kellneri, the palatal ridge of T. mesembrinus holo-
type (BSP 1987 I 46) begins level with the fifth tooth pair (Well-
nhofer, 1987).
Another specimen worth noting is BSP 1991 I 27, described by
Veldmeijer et al. (2009). BSP 1991 I 27 is a fragmentary skull
lacking the tip of the rostrum, as well as several postcranial
elements. BSP 1991 I 27 also comes from the Romualdo For-
mation, and is similar to DGEO-CTG-UFPE 8283 in several
aspects: both are slim, crestless, with a transversal triangular
section and a dorsally expanded and flattened anterior portion.
Also, the distance between consecutive alveoli increases in pos-
terior direction (Fig. S2). Differences between both specimens
include the fact that (1) BSP 1991 I 27 would have, if complete,
an about 22% larger rostrum; (2) its last three alveoli are more
rounded than ellipsoid; and (3) the alveoli demonstrate to be
overall larger than the condition observed in DGEO-CTG-
UFPE 8283. In addition, the palatal crest of BSP 1991 I 27
begins more posteriorly when compared with the specimen we
describe.
BSP 1991 I 27 was attributed by Veldmeijer et al. (2009)to
Brasileodactylus sp., mainly because of the absence of a
TABLE 1. DGEO–CTG–UFPE 8283 (Anhanguera sp.), measures of
the dentition in mm.
Alveolus Diastema
Quantity Diameter Quantity Diameter
1 5.14 1–2 1.97
2 6.3 2–3 3.38
3 6.37 3–4 3.17
46 4–5 3.59
55 5–6 5.68
6 4.5 6–77
7 5.34 7–8 8.8
8 5.8 8–9 9.4
9 5.85 9–10 12
10 5.3 10–11 12.78
11 5.3 11–12 14.8
12 5.2
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-5)
premaxillary crest, which we believe to be a weak diagnostic
feature. Comparisons between BSP 1991 I 27 and Brasileodacty-
lus holotype (MN-4804-V) are limited because the latter only
preserves a mandibular symphysis, which is absent in BSP 1991
I 27. However, BSP 1991 I 27 also appears to present the single
Anhanguera synapomorphy, the fourth and seventh alveoli
being larger than the fifth and the sixth ones. As such, BSP
1991 I 27 may also represent a crestless Anhanguera. Unfortu-
nately, the fact that this specimen lacks its anterior rostral end
prevented its inclusion in our morphometric dataset.
Geometric Morphometrics
The Principal Component Analysis results (Fig. 3) are consist-
ent with current phylogenetic and taxonomic propositions for the
relationships of the Anhangueridae and closely related taxa (e.g.,
Holgado and Pêgas, 2020). All the specimens that are
unambiguously assignable to Anhanguera (A.blittersdorffi(MN
4805-V), A.spielbergi (RGM 401 880), Anhanguera sp.
(AMNH 22555; SMNK PAL 3895; NHM R 11978 and SAO
16494)) are clustered together in the two-dimensional PCA
morphospace.
Cimoliopterids (Cimoliopterus dunni,C. cuvieri, and Campo-
sipterus) are also clustered together, but the occupied morpho-
space that defines the taxon in our analysis also includes
Siroccopteryx. Interestingly, Maaradactylus stands close to
Caulkicephalus in the horizontal axis (first principal component),
while Tropeognathus remains alone in the opposite extremity of
this same principal component.
Relevant to our study, specimen DGEO-CTG-UFPE 8283
falls inside the morphospace occupied by unambiguous Anhan-
guera specimens. As such, at least concerning the morphology
of the alveolar margin, the new specimen is indistinguishable
from Anhanguera.
FIGURE 3. Principal Component Analysis of morphometric data collected from 21 analyzed specimens. Landmarks 1 and 14 are depicted in a line
drawing of DGEO-CTG-UFPE 8283. Remaining landmarks (not numbered) should be considered sequentially, in an anterior-posterior direction.
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-6)
Phylogenetic Analysis
Our phylogenetic assessment of DGEO-CTG-UFPE 8283
resulted in 15 equally parsimonious trees of 350 steps each (CI
= 0.65, RI = 0.86). The strict (= Nielsen) consensus (Figs. 4, S1)
recovers DGEO-CTG-UFPE 8283 within a clade together with
Anhanguera piscator, AMNH 22555, and Anhanguera blitters-
dorffi. As demonstrated by the consensus topology, all recovered
trees depict DGEO-CTG-UFPE 8283 in a sister-OTU relation-
ship with A. blittersdorffi, whereas the relationships of the
clade composed by these two and the remaining Anhanguera
remain unresolved. The clade (DGEO-CTG-UFPE 8283 +
AMNH 22555 + A. piscator +A. blittersdorffi) lies in a polytomy
together with Liaoningopterus gui and (Maaradactylus kellneri +
Cearadactylus atrox). As such, our phylogenetic results are in
perfect agreement with the identification of DGEO-CTG-
UFPE 8283 as an additional Anhanguera specimen. Calculated
Bremer support values (Fig. 4) are mainly low, as is usual for pter-
osaur phylogenetic assessments.
DISCUSSION
As mentioned above, our morphometric analysis of premaxil-
lary and maxillary dental alveoli is consistent with the most
recent taxonomic proposals (Holgado et al., 2019), and demon-
strated to be a useful tool in identifying fragmentary specimens.
Results of our analysis may also shed light on other issues besides
the attribution of DGEO-CTG-UFPE 8283, such as the validity
of the recently erected taxon Cimoliopteridae (Camposipterus
and Cimoliopterus).
When described, the first Santana Group anhanguerids were
diagnosed by characters that, after further discoveries, were
demonstrated to be either well distributed within the clade
or ontogenetically variable. As such, several Anhanguera
species were recently invalidated, such as “A. cuvieri”,
“A. fittoni,”“A. araripensis,”“A. santanae,”and “A. robustus”
(Pinheiro and Rodrigues, 2017). The geometric morpho-
metric-based allometric regressions of Pinheiro and Rodrigues
(2017) demonstrated a strong positive allometric growth in the
sampled anhanguerid skulls, especially with respect to their
sagittal crests. It was, then, concluded that crest size and pos-
ition are strongly ontogenetically controlled in Anhanguera
(Fig. 5), being poor choices for the diagnosis of nominal
taxa. We should note that, in our PCA results, the specimens
recovered in the closest position to DGEO-CTG-UFPE 8283
were AMNH 22555 and SMNK PAL 3895. Curiously, both rep-
resent the Anhanguera specimens with the smallest sagittal
crests. The first (AMNH 22555) features a short rostrum and
an apparently better-developed crest, while the latter (SMNK
PAL 3895) presents a comparatively long rostrum and a very
subtle crest.
It has already been discussed (e.g., Bennett, 1992,1994,2006;
Carpenter et al., 2003; Frey et al., 2003; Unwin, 2005) that ptero-
saur premaxillary crests are potentially sexually dimorphic and
subject to ontogenetic variation, being of limited use as diagnos-
tic features. In 2014, two unexpected discoveries added to this
discussion, shedding light over interesting aspects of pterosaur
biology. One assemblage with at least 47 individuals of different
growth stages showed that the ontogenetic variation in Caiuajara
dobruskii is reflected mainly by the size and inclination of its pre-
maxillary crest, with this structure becoming bigger and steeper
in the course of the development, in a characteristic positive allo-
metric growth (Manzig et al., 2014). The second study reports the
discovery of a 40-individual bonebed containing males and
females of Hamipterus tianshanensis, as well as several eggs.
Wang et al. (2014) demonstrated that the rostral anterior expan-
sion is an ontogenetic feature in Hamipterus and that the pre-
maxillary crest’s size and shape are sexually dimorphic within
the species.Three years before, sexual dimorphism in pterosaurs
was already reported for Chinese specimens, when Lü et al.
FIGURE 4. Simplified strict consensus of the most parsimonious trees recovered in the preferred cladistic analysis. Values correspond to Bremer
support. Silhouettes by the author, not to scale.
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-7)
(2011) described a Darwinopterus specimen associated with two
eggs, which was later attributed to Kunpengopterus (Wang et al.,
2015; Zhou et al., 2021). That finding, together with the assess-
ment of several other similar specimens, showed that the darwi-
nopteran males had relatively small pelvises and large cranial
crests, while females had larger pelvises and lacked cranial
crests. Variations on pelvis morphology and crest shape were
also observed in Pteranodon, while, in this genus, both males
and females present crests, those of the males being larger than
the ones of the assumed females (Bennett, 1992,1994). This
mutual sexual selection (where both males and females are orna-
mented and both select mates) is also a reality in extant animals,
and thus cannot be ignored as a possibility for some pterosaurs
(Hone et al., 2012).
The holotype of Brasileodactylus araripensis (MN 4804-V)
consists of a crestless fragmented mandibular symphysis
(Kellner, 1984). While analyzing the ontogeny of the four speci-
mens attributed to Brasileodactylus at that time, Bennett (2018)
highlighted several similarities between Brasileodactylus and
Anhanguera. Both AMNH 24444 and BSP 1991 I 27 show signs
of size-independent skeletal immaturity (Bennett, 2018). When
first described by Veldmeijer (2003), AMNH 24444 was still
embedded within its original carbonaceous concretion, with the
exposed portions of its right premaxilla and dentary considerably
eroded, which prevents the recognition of the diagnostic charac-
ters of Anhanguera and Brasileodactylus. The attribution of
AMNH 24444 to Brasileodactylus is, thus, debatable and, as far
as the Brasileodactylus record goes, the relationship between
this genus and Anhanguera is still elusive, and more complete
specimens of the former are needed in order to enlighten this
issue.
All the proposed Anhanguera species were traditionally
diagnosed by the presence of a premaxillary sagittal crest con-
fined to the rostral end of the skull, subtle variations of this
structure being the main distinguishing features between
nominal taxa (Campos and Kellner, 1985; Kellner and
Tomida, 2000). Comprehensive assessments of Anhanguera
ontogeny (e.g., Pinheiro and Rodrigues, 2017) are recent, and
demonstrate that the strong allometric growth of premaxillary
crests makes those structures ill-suited for taxonomic purposes
(Fig. 5). We presented, here, strong anatomical, morphometric,
and phylogenetic support for the attribution of DGEO-CTG-
UFPE 8283 to Anhanguera sp., this being the first crestless
Anhanguera recognized as such. The existence of crestless
Anhanguera individuals is in perfect agreement with the onto-
genetic growth of pterosaur headcrests, as well as with the pro-
posed use of the crests as display ornaments. While the
ontogenetic growth of Anhanguera premaxillary crests was
FIGURE 5. Artistic reconstruction based on specimen DGEO-CTG-UFPE 8283. A, skull of a young individual; B, reconstructed skull of an onto-
genetically advanced individual. Scale bar equals 100 mm. Digital painting by Matheus Fernandes Gadelha.
Duque et al. –Ontogenetic growth of Anhanguera premaxillary crest (e2116984-8)
already well-established, we should also consider the possibility
that this structure was sexually dimorphic within the genus, an
issue that will probably be solved by future discoveries and
comprehensive analyses of recovered samples.
CONCLUSIONS
Geometric morphometrics applied to dental alveoli has
proved to be a useful tool in investigating the relationships of
toothed pterosaurs taxa, especially with regard to fragmentary
specimens. Morphometrics, thus, appears to be a more efficient
tool than the use of sagittal crests as diagnostic features, a prac-
tice that resulted in an overestimated diversity of Romualdo For-
mation pterosaurs (Pinheiro and Rodrigues, 2017).
All the methodological approaches we used (anatomy, mor-
phometrics, and phylogenetics) are in agreement with the identi-
fication of DGEO-CTG-UFPE 8283 as a further Anhanguera
specimen. The lack of a premaxillary crest in the new specimen
is consistent with intrageneric variation, probably reflecting the
fact that Anhanguera premaxillary crests were strongly con-
trolled by ontogeny, sexual dimorphism also not being discarded.
ACKNOWLEDGMENTS
RRCD and AMFB: We thank the city hall of Exu and FUN-
DARPE for supporting this research; G. Cordeiro and
C. Marcelino for their valuable field assistance. FLP: M. Norell
and C. Mehling (AMNH); R. Bantim (MPSC); O. Rauhut and
M. Moser (SNSB-BSPG); A. Kellner and H. Silva (MN);
E. Frey (SMNK); R. Schoch (SMNS); S. Chapman and L. Steel
(NHMUK); D. Pemberton and M. Riley (CAMSM). We thank
J. Bubadué (UENF) for insights on the morphometrics method-
ology. The manuscript was greatly improved by insightful com-
ments from referees C. Bennett and R. Pêgas. This study was
financed by grants from the Conselho Nacional de Desenvolvi-
mento Científico e Tecnológico (CNPq 303071/2014-1 to
RRCD; CNPq 407969/2016-0; 305758/2017-9 to FLP) and Fun-
cultura Independente Project (0756/2014 to RRCD).
ORCID
Rudah Ruano C. Duque http://orcid.org/0000-0002-9489-9672
Felipe L. Pinheiro http://orcid.org/0000-0003-3354-914X
Alcina Magnólia Franca Barreto http://orcid.org/0000-0003-0864-
7995
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