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The discovery of a previously undescribed pterosaur, Thalassodromeus sethi, yields information on the function of cranial crests and the feeding strategy developed by these extinct flying reptiles. The material consists of a large skull (length: 1420 millimeters, including the crest) with a huge bony crest that was well irrigated by blood vessels and may have been used for regulation of its body temperature. The rostrum consists of two bladelike laminae, the arrangement of which is analogous to the condition found in the bird Rynchops, which skims over the water to catch food, indicating that T. sethialso may have been a skimmer.
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The Function of the Cranial Crest
and Jaws of a Unique Pterosaur
from the Early Cretaceous of Brazil
Alexander W. A. Kellner
* and Diogenes de Almeida Campos
The discovery of a previously undescribed pterosaur, Thalassodromeus sethi, yields
information on the function of cranial crests and the feeding strategy developed
by these extinct flying reptiles. The material consists of a large skull (length: 1420
millimeters, including the crest) with a huge bony crest that was well irrigated by
blood vessels and may have been used for regulation of its body temperature. The
rostrum consists of two bladelike laminae, the arrangement of which is anal-
ogous to the condition found in the bird Rynchops, which skims over the water
to catch food, indicating that T. sethi also may have been a skimmer.
Despite being studied for over 200 years, the
overall knowledge of pterosaur diversity and
biology is rather slim, mainly due to uneven
sampling and the generally poor preservation
of specimens (1, 2). Moreover, because ptero-
saurs are extinct, their biological habits and
functions of anatomical features are difficult
to establish, and most interpretations have
relied on comparisons with modern analogs
such as birds. Here, we report a previously
undescribed pterosaur that shows a distinct
morphology of the skull, providing informa-
tion on the function of cranial crests and
feeding strategy. The specimen comes from
the Romualdo Member of the Santana For-
mation (3), in the Araripe Basin, in northeast-
ern Brazil, which is one of the few deposits
where pterosaurs are found in large numbers
with good preservation.
The sedimentary rocks of the Santana For-
mation were deposited during the Early Cre-
taceous (Aptian/Albian) and represent two
distinct lagerstatten, formed by the lacustrine
limestone layers of the Crato Member at the
base and the lagoonal limestone concretions
embedded in shales of the Romualdo Mem-
ber at the top (4, 5). Although pterosaurs have
been found in the lower layers (2, 68), the
deposits in the Romualdo Member contain
better-preserved specimens (912). The ma-
terial described here was preserved in a cal-
careous nodule from this deposit and consists
of an almost complete skull (Fig. 1), repre-
senting a new species.
Pterosauria Kaup, 1834
Pterodactyloidea Plieninger, 1901
Tapejaridae Kellner, 1989
Thalassodromeus nov. gen.
T. sethi nov. sp.
Etymology: Thalassodromeus from the
Greek tha´lassa ( sea) dromeu´s (runner)
meaning the “sea runner”; sethi for the an-
cient Egyptian god Seth.
Holotype: skull (total length, 1420 mm;
length from the squamosal to the tip of the
premaxilla, 798 mm) and lower jaw (length:
preserved, 635 mm; estimated, 710 mm) de-
posited at the Museu de Cieˆncias da Terra/
Departamento Nacional de Produc¸a˜o Mineral
(DGM 1476-R) (Figs. 1 to 3); cast at the
Museu Nacional (MN)/Universidade Federal
do Rio de Janeiro (UFRJ) (MN 6678-V).
Horizon and locality: The specimen was
collected in 1983 at the outcrops of the Ro-
mualdo Member [Albian (3, 5)], in the Santana
Formation, near the town of Santana do Cariri,
in the state of Ceara´, northeastern Brazil.
Diagnosis: Tapejarid with developed cranial
crest composed of premaxillae, frontal, parietal,
and supraoccipital, starting at the tip of the skull
and extended posteriorly, well behind the oc-
cipital region; posterior end of the cranial crest
V-shaped; suture between premaxillae and
frontoparietal portion of the crest rectilinear;
anterior portion of the premaxillae and dentary
with sharp dorsal and ventral edges; palatines
before palatal crest strongly concave; posterior
(occipital) region broader than in other tapeja-
rids (width over quadrates, 20% of squamosal
to premaxilla length).
With the exception of two segments from
the ventral part of the skull plus the mandible
and the distal tip of the lower jaw, the mate-
rial is complete and all bones are preserved in
three dimensions. The only signs of compac-
tion are found in the region of the left jugal
and in the right mandibular ramus, which are
slightly pushed inward.
As is typical of derived pterosaurs (mem-
bers of the clade Pterodactyloidea), T. sethi
has an elongated skull (Fig. 1). The orbit is
positioned lower than the dorsal rim of the
antorbital fenestra, a feature only present in
the azhdarchids [e.g., Quetzalcoatlus sp.
Paleovertebrate Sector, Department of Geology and
Paleontology, Museu Nacional/Universidade Federal
do Rio de Janeiro, Quinta da Boa Vista, Sa˜o Cristo´va˜o,
Rio de Janeiro, RJ, 20940 040, Brazil.
Museu de
Cieˆncias da Terra/Departamento Nacional de Produ-
c¸a˜o Mineral, avenida Pasteur 404, Rio de Janeiro, RJ,
22290–240, Brazil.
*The authors are fellows at Conselho Nacional de
Desenvolvimento Cientı´fico e Tecnolo´gico and asso-
ciate researchers at the American Museum of Natural
To whom correspondence should be addressed. E-
(13)] and tapejarids [Tapejara wellnhoferi
(14, 15)]. The nasoantorbital fenestra is very
large (390 mm), comprising about half of the
cranial length between the squamosal and the
tip of the premaxilla. Starting at the anterior
end of the premaxillae, T. sethi exhibits a
large sagittal crest that extends above the
nasoantorbital fenestra and well behind the
occipital region. This cranial structure is
formed by frontals, parietals, and premaxil-
lae, which fuse in the midline, and by the
supraoccipital, which builds the ventral edge
right behind the occipital region. Despite its
size, the crest is lightly built, with the bones
united by a well-developed trabecular sys-
tem. The premaxillae contribute to most of it
and differ from those of other crested ptero-
saurs [e.g., Pteranodon (16, 17) and Dsun-
garipterus (18)], because they extend to the
most posterior portion of the crest, terminat-
ing in a V-shaped structure. The frontals and
parietals form the base of the posterior part of
the crest, and their contact with the premax-
illae is straight. This crest is essentially hol-
low, internally supported by a well-devel-
oped system of trabeculae, and varies in
thickness (from 1.0 to 10.5 mm) along the
region where it connects to the skull. Above
the skull roof, it thickens at the contact be-
tween the premaxilla and frontal and gets
gradually thinner toward the top and back,
except for the ventral part directly behind the
occiput (formed by the supraoccipital), where
it has a thick base (7.5 mm) and shows
several ridges for muscle attachment.
On the basis of the large sagittal crest and
the extended nasoantorbital fenestra, T. sethi
can be allocated to the Tapejaridae (19). Two
other genera, Tapejara (7, 14 ) and Tupuxu-
ara (20, 21), each with two species, have
been grouped in this clade. Thalassodromeus
is easily set apart from Tapejara, which
are comparatively short-faced pterosaurs.
Thalassodromeus shares with Tupuxuara a
palatal crest but has the anterior portion of the
palatal region turned into a bladelike lamina
instead of the flat condition found in Tupuxu-
ara. Furthermore, the palate posterior to the
palatal crest of the new taxon is concave
instead of having the convex condition found
in Tupuxuara (20). Thalassodromeus also has
a proportionally higher premaxillary sagittal
crest, particularly above the nasoantorbital
fenestra. A briefly mentioned skull of Tu-
puxuara (22) shows that the occipital region
of Thalassodromeus is comparatively broad-
er. Some fragmentary pterosaur remains from
Maastrichtian strata of Romania include a
large occiput (23), but the material lacks the
anterior portion of the skull, impeding de-
tailed comparisons with Thalassodromeus.
With the exception of Tapejara imperator
(7), T. sethi has the proportionally largest
crest known in any vertebrate (fossil or re-
cent), which makes up about 75% of the
Fig. 1. (A) T. sethi (DGM 1476-R) skull in left lateral view. (B) Drawing showing the contact of
the cranial bones. Art, articular; f, frontal; d, dentary; j, jugal; l, lacrimal; ltf, lower temporal
fenestra; m, maxilla; naof, nasoantorbital fenestra; n, nasal; np, nasal process; or, orbit; p,
parietal; pm, premaxilla; q, quadrate; san, surangular; soc, supraoccipital; sq, squamosal; utf,
upper temporal fenestra. Scale bar, 200 mm.
Fig. 2. (A) Detail of the crest of T. sethi (DGM
1476-R), showing channels on the bone surface,
interpreted as the imprints of blood vessels. (B)
Drawing showing the preferential orientation
of the interpreted blood vessels (only the larger
ones are illustrated here). The stippled area
indicates sedimentary rock. Naof, nasoantor-
bital fenestra; np, nasal process. Scale bar, 100
19 JULY 2002 VOL 297 SCIENCE www.sciencemag.org390
cranial lateral surface. The crest in T. sethi
differs from the one in T. imperator, because
it is fully ossified, with some darker areas
suggesting that it had a horny covering, par-
ticularly on the top and posterior end. A
system of channels of different sizes and
thicknesses is present on the external bone
surface (Fig. 2A). This feature, observed for
the first time in a pterosaur cranial crest, is
interpreted as the impression of blood ves-
sels. A main central channel rises vertically
from above the orbit and is divided into large
channels directed anteroposteriorly at the
basal portion of the crest. From those, other
channels branch off, curve upward, and tend
to be parallel to each other, giving rise to
smaller ones that form a complex pattern
(Fig. 2, A and B). This network of vascular
supply indicates that this crest was extensive-
ly irrigated by blood vessels and is consistent
with the notion of it having been used in
thermoregulation, as has been argued for
some dinosaurs (24, 25). In Thalasso-
dromeus, this cranial structure might have
been more useful for cooling, with the crest
used as a heat dissipater enabling the animal
to lose excess metabolic heat to the environ-
ment through convection. The large size of
the crest increased the surface area for that
purpose, but the heat transfer effectiveness
must have been controlled by, and been de-
pendent on, the ability of the circulatory sys-
tem to pump blood to the crest, for which a
well-developed network of vascular supply
was necessary. To be able to control the body
temperature might have been particularly
useful when the animal was most active, as,
for example, during hunting, when it would
dump excess metabolic heat into the environ-
ment, with the crest having a wind-aligned
orientation, with effectiveness being eventu-
ally increased by restricted intentional lateral
movement of the head.
It should be noted that a thermoregulatory
function of the crest would not preclude this
structure from having had other functions,
such as species recognition, with the particu-
lar form (including the V-shaped end), in
conjunction with colors, allowing members
of T. sethi to recognize their kin. Sexual
dimorphism is also a possibility and has been
argued for Pteranodon [all having cranial
crests (26, 27 )], but the limited information
on tapejarid postcranials makes this last hy-
pothesis complicated to test. Although the
function of cranial crests in pterosaurs is
difficult to determine (14, 17, 18, 2629), all
evidence suggests that, in T. sethi, this struc-
ture had multiple functions, interfering with
aerodynamics (because of its large size),
helping in thermal regulation, and function-
ing as a display structure.
The palatal and rostral configuration of T.
sethi is also unusual and is related to its feeding
habit. A strong concavity formed by the pala-
tines and bordered laterally by the maxillae is
present under the anterior half of the nasoantor-
bital fenestrae. Anterior to this concavity, the
palate is convex, forming a short ventral keel
that turns into a sharp blade anteriorly. The
fused dentaries form a perfect counterpart to the
palate, with a developed concavity, followed by
a short, deep groove (that during occlusion
encases the palatal keel, forming a strong inter-
locking mechanism) and an anterior sharp bony
blade (Fig. 3A). Between both blades there is a
gap. The whole skull, particularly the rostral
portion, is streamlined.
The only modern analog with such a rostral
end is found in the avian genus Rynchops (Lari-
dae; Rynchopini). Popularly known as skim-
mers, the members of this taxon have laterally
compressed upper and lower jaws with a blade-
like horny covering (rhamphotheca) and a pro-
truding lower jaw, giving it, in lateral view, an
asymmetric scissors-like aspect (Fig. 3B). Ryn-
chops, whose wing span is generally less than 1
meter, skims over the surface and dips its lower
jaw into the water to catch small pelagic fishes
and crustaceans (30). In addition to the rostrum,
these birds have other structural adaptations for
skimming, among which are curved tomia (the
cutting edge of the rhamphotheca) of the upper
jaw, broad quadrate condyles, large palatines,
large neck musculature, large adductor man-
dibula complex musculature, and greater blood
supply and enervation of the tips of the jaws,
particularly the lower one (30).
The palatines of T. sethi are enlarged too,
but unlike those of Rynchops and other ptero-
saurs, they are concave, constituting a possi-
ble adaptation for momentarily storing food.
The occipital region of T. sethi is more de-
veloped (width between opisthotics 113.6
mm) than in other pterosaurs, with strong
muscle scars in several parts and a well-
developed supraoccipital crest, suggesting
the presence of powerful neck muscles. Sev-
eral ridges that reach the base of the basal
portion of the sagittal crest behind the occip-
ital region are observed above the temporal
opening, indicating that the adductor muscu-
lature was well developed. Lastly, there are
several small foramina on the tip of the pre-
maxillae (the tip of the dentary is not pre-
served) indicating that this region was well
irrigated by blood vessels (and likely well
supplied by nerves). The morphology of the
specimen supports the hypothesis that T. sethi
was also a skimmer. As in Rynchops, the
specialized scissors-like bill of Thalasso-
dromeus almost precludes any other method
of capturing prey, such as swooping toward
the water and taking the prey with a single
downward nod of the head, as observed in
several birds [e.g., gull-billed tern (30)]. Be-
cause of the large but thin crest, it is also
unlikely that Thalassodromeus plunged in the
water for fish, as observed, for example, in
the royal tern (30).
Although the fishing technique of T. sethi is
difficult to reconstruct, we have used detailed
reports of the skimming technique of Rynchops
(30) to develop a model, which also takes into
account the differences between the basic avian
and pterosaurian skeletons (figs. S1 and S2).
Whenever striking an object during skimming,
the upper jaw of Rynchops clamps down, while
the head moves down and back, sometimes
becoming completely submerged. The ptero-
saur neck is formed usually by nine cervicals (1,
12, 17 ) [compared to the 15 cervicals of Ryn-
chops (30)], limiting its mobility, as compared
to Rynchops. Therefore, although the general
downward movement of the head of Thalasso-
dromeus was similar to that of Rynchops, the
backward motion was more limited. Further-
more, the size of the crest would impede a
complete submersion of the skull, contrary to
what occasionally happens in Rynchops. Dur-
ing skimming, this bird maintains its body in a
horizontal or only slightly tilted position rela-
tive to the water surface, alternately gliding or
flapping rapidly with regular beats (30). Based
on its large wing surface, Thalassodromeus
probably used more gliding power during skim-
ming, occasionally flapping its wings, particu-
larly after catching prey.
The rostral configuration of T. sethi is
unique among pterosaurs. The most similar
condition is found in some species of Rham-
phorhynchus from the Late Jurassic Soln-
hofen limestone (31), which have a small
anterior projection on the tip of the lower jaw
and have been regarded as casual skimmers
Fig. 3. The skull of T. sethi (A) and Rynchops (B).
Note the extreme lateral-compressed and scis-
sors-like upper and lower jaws of both (not
drawn to scale).
(1). The rostral portion of the Rhamphorhyn-
chus species differs from that of Thalasso-
dromeus because it is toothed, is compara-
tively reduced, and has a less sharp and
smaller anterior rostral projection. Further-
more, the skull in Rhamphorhynchus lacks
the adaptations for skimming activity dis-
cussed above and might have had only crude
and limited skimming behavior. Another dif-
ference between both is size. Although most
Rhamphorhynchus specimens have a wing-
span ranging from 500 to 1200 mm [the
largest one being 1750 mm (31)], the estimat-
ed length represented by the type material of
Thalassodromeus sethi [based on other tape-
jarid specimens (8, 22)] varies between 4200
and 4500 mm, making it a large volant crea-
ture that got its nourishment by skimming the
Araripe lagoon and the nearby ocean 110
million years ago.
References and Notes
1. P. Wellnhofer, The Illustrated Encyclopedia of Ptero-
saurs (Salamander, London, 1991).
2. A. W. A. Kellner, Acta Geol. Leopoldensia 39, 175
3. G. Beurlen, An. Acad. Bras. Cienc. Suppl. 43, 411 (1971).
4. J. G. Maisey, Ed., Santana Fossils, An Illustrated Atlas
( T. F. H. Publishers, Neptune City, NJ, 1991).
5. D. Pons, P. Y. Berthou, D. A. Campos, in Atas 1:
Simpo´sio da Bacia Araripe e Bacias Interiores do Nor-
deste, D. A. Campos, M. S. S. Viana, Eds. (Crato, Ceara´,
Brasil, 1990), pp. 241–252.
6. E. Frey, D. Martill, Neues Jahrb. Geol. Palaeontol.
Abh. 194, 379 (1994).
7. D. A. Campos, A. W. A. Kellner, An. Acad. Bras. Cienc.
69, 83 (1997).
8. J. M. Saya˜o, A. W. A. Kellner, Bol. Museu Nacional
Geologia 54, 1 (2000).
9. L. I. Price, An. Acad. Bras. Cienc. Suppl. 43, 451 (1971).
10. P. Wellnhofer, Palaeontographica 187, 105 (1985).
11. D. A. Campos, A. W. A. Kellner, An. Acad. Bras. Cienc.
57, 453 (1985).
12. A. W. A. Kellner, Y. Tomida, Nat. Sci. Museum Monogr.
17, 1 (2000).
13. A. W. A. Kellner, W. Langston, J. Vertebr. Paleontol.
16, 222 (1996).
14. A. W. A. Kellner, An. Acad. Bras. Cienc. 61, 439 (1989).
15. P. Wellnhofer, A. W. A. Kellner, Mitt. Bayer. Staastsslg.
Palaeontol. Hist. Geol. 31, 89 (1991).
16. G. F. Eaton, Mem. Conn. Acad. Arts Sci. 2, 1 (1910).
17. C. S. Bennett, Palaeontographica 260, 1 (2001).
18. C. C. Young, Spec. Publ. Inst. Vert. Paleontol. Paleo-
anthr. Acad. Sin. 11, 18 (1973) (in Chinese).
19. A. W. A. Kellner, thesis, Columbia University (1996).
㛬㛬㛬㛬 , D. A. Campos, An. Acad. Bras. Cienc. 60, 459
21. 㛬㛬㛬㛬 , An. Acad. Bras. Cienc. 66, 467 (1994).
22. A. W. A. Kellner, Y. Hasegawa, J. Vertebr. Paleontol.
13 (suppl. to 3), 44A (1993).
23. E. Buffetaut, D. Grigorescu, Z. Csiki, Naturwissen-
schaften 89, 180 (2002).
24. J. O. Farlow, C. V. Thompson, D. E. Rosner, Science
192, 1123 (1976).
25. S. Sampson, Dinofest Intern. Proc. 1997, 39 (1997).
26. W. Langston, Sci. Am. 244, 122 (1981).
27. S. C. Bennett, J. Vertebr. Paleontol. 12, 422 (1992).
28. D. Kripp, Nova Acta Leopold. N. F. 12, 16 (1943).
29. C. D. Bramwell, G. R. Whitfield, Philos. Trans. R. Soc.
London Ser. B 267, 503 (1981).
30. R. Zusi, Publ. Nuttall Ornithol. Club 3, 1 (1962).
31. P. Wellnhofer, Palaeontographica 148, 1 (1975).
32. We thank V. Arraes de Alencar Gervaiseau, P. Nuvens,
. Saravaia (Universidade Regional do Cariri), and A.
Andrade (Departamento Nacional de Produc¸a˜o Min-
eral, Crato) for supporting fieldwork at the Araripe
Basin; J. de Alencar (Crato) for assisting D.A.C. during
field activities; J. G. Maisey, G. Leonardi, G. Ligabue,
and P. Taquet for discussions about this specimen; H.
Silva and M. Craik (MN/UFRJ) for helping with the
preparation of the material; and M. Oliveira (MN/
UFRJ) for the drawings used in this paper. Partially
funded by the Fundac¸a˜o Carlos Chagas de Amparo a`
Pesquisa do Rio de Janeiro.
Supporting Online Material
Figs. S1 and S2
23 April 2002; accepted 14 June 2002
19 JULY 2002 VOL 297 SCIENCE www.sciencemag.org392
... Witton (2013) presented a generalized sketch of what the jaw musculature of some pterosaurs would look like [Istiodactylus latidens (Seeley, 1901), Quetzalcoatlus Lawson, 1975, Raeticodactylus filisurensis Stecher, 2008, mostly based on the work of Ösi (2011). Pêgas et al. (2016Pêgas et al. ( , 2018 provided brief comments on osteological correlates in the tapejarids Aymberedactylus cearensis Pêgas et al., 2016 and Thalassodromeus sethi Kellner & Campos, 2002, which were linked to specific jaw muscles based on the general topology in diapsids (Holliday & Witmer, 2007). ...
... E, F, Dsungaripterus weii (based on Young, 1984). G, H, Thalassodromeus sethi (based on Kellner & Campos, 2002;Pêgas et al., 2018). I, J, Tupuxuara leonardii (based on Kellner, 2004;Pinheiro & Schultz, 2012). ...
... They are members of the Thalassodrominae (Tapejaridae) and their genera are sister taxa (Kellner & Campos, 2007;Andres et al., 2014;Pêgas et al., 2018). When originally described, Th. sethi was interpreted as a skim-feeder (and thus an aerial piscivore) due to its laterally compressed jaws, which are reminiscent of those of the skimmer Rynchops Linnaeus, 1758 (see Kellner & Campos, 2002). However, this view was subsequently challenged on both morphological and metabolic grounds (see Humphries et al., 2007). ...
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The reconstruction of jaw muscles is critical in establishing potential cranial functions; however, myological studies of extinct groups that have no descendants are difficult to perform and test. This is particularly true for pterosaurs, a group of extinct flying reptiles that present a plethora of cranial morphologies, suggesting different functions and feeding habits. Here we present a first attempt to reconstruct the adductor musculature of the pterodactyloid skull in detail, using osteological correlates and the extant phylogenetic bracketing method. Using these reconstructions, we estimate bite force for nine selected species and investigate implications for potential dietary habits.
... Thalassodromeus exhibits a highly unusual, specialized jaw morphology. On both jaws, the jaw tip is laterolaterally compressed and the occlusal surface is a single keel, formed by the fusion of the tomia (Kellner and Campos, 2002, fig. 1; Pêgas et al., 2018, fig. ...
... Branch-based definition. The most inclusive clade containing Azhdarcho lancicollis Nessov 1984 but not Thalassodromeus sethi Kellner and Campos 2002 or Tapejara wellnhoferi Kellner 1989. Reference phylogeny: Fig. 10. ...
Aerotitan sudamericanus, from the Upper Cretaceous of the Neuquén Basin (Patagonia, Argentina), is known from a partial jaw fragment which has been interpreted as either an azhdarchid upper jaw, azhdarchid lower jaw, or thalassodromine upper jaw (as the sister-group of Alanqa). Here, we compare it in detail to upper and lower jaws of taxa belonging to all azhdarchoid lineages. It possesses a lateral angle (angle of divergence between occlusal and apex margins in lateral view) that is too low for an upper jaw of any azhdarchoid group. It further differs from thalassodromine upper jaws in exhibiting a convex occlusal margin (in lateral view), a sulcate occlusal surface, and lacking a sagittal crest. Furthermore, Aerotitan differs from Alanqa in 5 aspects: (1) occlusal margin shape in lateral view (convex in Aerotitan, straight in Alanqa), (2) median dentary eminence shape (slender in Aerotitan, posteriorly expanded in Alanqa), (3) median dentary eminence position (anterior in Aerotitan, close to the posterior end of the symphysis in Alanqa), (4) tomial edges shape (thick and blunt in Aerotitan, thin and sharp in Alanqa), and (5) occlusal surface anterior to the median eminence (cross-section concave in Aerotitan, slightly convex in Alanqa). We also conclude that the holotype of A. sudamericanus is a match for an azhdarchid lower jaw, being extremely similar to that of Mistralazhdarcho. When scored as a lower jaw in our phylogenetic analysis, it is recovered as a close relative of Mistralazhdarcho, in a polytomy that also includes Arambourgiania. In contrast, Alanqa is recovered as the sister-group of Keresdrakon, both located at the base of a broader clade of long-snouted azhdarchoids that also includes chaoyangopterids and azhdarchids, to the exclusion of tapejarines and thalassodromines.
... In non-avian dinosaurs, sexual selection likely drove the evolution of fusiform feathers as sexual signals, but at the cost of reduced insulation (Persons & Currie, 2019). Similarly, while the anatomy of pterosaur head crests resembles heat dissipation structures found in extant animals (Kellner & De Almeida Campos, 2002), detailed analyses suggest that sexual selection may have exaggerated these crests far beyond what was suitable for thermoregulation (Tomkins et al., 2010). When the exaggeration of a sexual trait reduces its thermoregulatory function, sexual selection may favour increased thermal tolerances to accommodate this thermal cost. ...
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Thermal ecology and mate competition are both pervasive features of ecological adaptation. A surge of recent work has uncovered the diversity of ways in which temperature affects mating interactions and sexual selection. However, the potential for thermal biology and reproductive ecology to evolve together as organisms adapt to their thermal environment has been underappreciated. Here, we develop a series of hypotheses regarding (1) not only how thermal ecology affects mating system dynamics, but also how mating dynamics can generate selection on thermal traits; and (2) how the thermal consequences of mate competition favour the reciprocal co‐adaptation of thermal biology and sexual traits. We discuss our hypotheses in the context of both pre‐copulatory and post‐copulatory processes. We also call for future work integrating experimental and phylogenetic comparative approaches to understand evolutionary feedbacks between thermal ecology and sexual selection. Overall, studying reciprocal feedbacks between thermal ecology and sexual selection may be necessary to understand how organisms have adapted to the environments of the past and could persist in the environments of the future.
... The Araripe Basin ( Fig. 1) is worldwide known as a Konservat-Lagerst€ atte, with abundant, diversified and well-preserved life forms which have been recovered from the Lower Cretaceous Santana Group strata (Maisey, 1991;Martill, 2007). The fossil record is constituted by both continental and marine macro organisms, such as plant remains, insects, fish, reptiles, invertebrates, as well as abundant microfossils such as palynomorphs, foraminifers and ostracods (e.g., Bate, 1972;Price, 1973;Silva and Arruda, 1976;Maisey, 1991;Coimbra et al., 2002;Kellner and Campos, 2002;Salisbury et al., 2003;Mohr et al., 2007;Brito and Yabumoto, 2011;Lima et al., 2012;Barling et al., 2015;Arai and Assine, 2020;Melo et al., 2020;Silva et al., 2020). A detailed study about the Crato Formation paleoenvironment can be found in Ribeiro et al. (2021) who developed an integrated overview of the fossil community of this worldwide known paleolake. ...
Fossil resins and ostracods are well-known in Brazilian Cretaceous sedimentary Basins, especially in the Araripe Basin. The present work reports several ostracods encapsulated in an amber sample recovered from limestones of the Crato Formation (Araripe Basin, Northeastern Brazil). The amber was analyzed under optical microscopy revealing several ostracod specimens. Considering the general morphology, the recovered specimens were attributed to the freshwater to brackish genera Pattersoncypris Bate, 1972 and Damonella Anderson, 1966 in the superfamily Cypridoidea. Additionally, palynological analyses of the limestone rock around the amber demonstrate the predominance of pollen grains of the Classopolis genus, produced by conifers of Cheirolepidiaceae family, suggesting this family as possible botanical source of the fossil resin. The proposed interpretation for this preservation is as follow: (i) the lake level variations transported the ostracods to the margin; (ii) drops of resin exuded from the trunk fell to the margin on the dead ostracods; (iii) the exposed resin underwent polymerization preserving the ostracods; (iv) and finally, the amber was preserved in the laminated calcareous deposit. The record described here provides a detailed study of organisms fossilized in Brazilian amber as well as it reports the oldest record of ostracods enclosed in fossil resins (Aptian age).
... Depending on the ancestral integumentary suite of pterosaurs, it is possible that simple filament structures homologous to feathers are ancestral to at least Dinosauria (Clarke 2013;Lowe et al., 2014;Benton et al., 2019). Pterosaurs have also been found with filaments called pycnofibers , and it has been suggested that they had a keratinous rhamphotheca along the jaws and potential keratinous coverings on cranial crests (Kellner & Campos, 2008). Integuments such as filaments and early feather forms would likely have been seasonally molted, whereas scales and rhamphotheca are hypothesized to have grown continuously as seen in living turtles and birds (Lucas & Stettenheim, 1972;Xu 2020). ...
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Carotenoids are pigments responsible for most bright yellow, red, and orange hues in birds. Their distribution has been investigated in avian plumage, but the evolution of their expression in skin and other integumentary structures has not been approached in detail. Here, we investigate the expression of carotenoid‐consistent coloration across tissue types in all extant, non‐passerine species (n= 4,022) and archelosaur outgroups in a phylogenetic framework. We collect dietary data for a subset of birds and investigate how dietary carotenoid intake may relate to carotenoid expression in various tissues. We find that carotenoid‐consistent expression in skin or non‐plumage keratin has a 50 percent probability of being present in the most recent common ancestor of Archosauria. Skin expression has a similar probability at the base of the avian crown clade, but plumage expression is unambiguously absent in that ancestor and shows hundreds of independent gains within non‐passerine neognaths, consistent with previous studies. Although our data do not support a strict sequence of tissue expression in non‐passerine birds, we find support that expression of carotenoid‐consistent color in non‐plumage integument structures might evolve in a correlated manner and feathers are rarely the only region of expression. Taxa with diets high in carotenoid content also show expression in more body regions and tissue types. Our results may inform targeted assays for carotenoids in tissues other than feathers, and expectations of these pigments in non‐avian dinosaurs. In extinct groups, bare‐skin regions and the rhamphotheca, especially in species with diets rich in plants, may express these pigments, which are not expected in feathers or feather homologues. This article is protected by copyright. All rights reserved
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The Azhdarchidae have come to be known as the most diverse clade of Late Cretaceous pterosaurs and the largest flying creatures in existence. Since the erection of the taxon nearly four decades ago, many partial specimens have been referred to it from the Early Cretaceous and Late Jurassic, but none of these identifications can be confirmed. The most comprehensive phylogenetic analysis and taxonomy of Pterosauria is presented, and the evolutionary history of the Azhdarchidae is reviewed. As currently known, azhdarchids are restricted to the Late Cretaceous (Turonian–Maastrichtian). Fourteen species are currently included in the Azhdarchidae: Quetzalcoatlus northropi and Q. lawsoni are recovered as sister taxa in a monophyletic Quetzalcoatlus, with Arambourgiania philadelphiae, Hatzegopteryx thambema, a trichotomy with Cryodrakon boreas and Wellnhopterus brevirostris, Zhejiangopterus linhaiensis, Eurazhdarcho langendorfensis, a Phosphatodraco mauritanicus + Aralazhdarcho bostobensis sister group, as well as an Azhdarcho lancicollis + Albadraco tharmisensis + Aerotitan sudamericanus + Mistralazhdarcho maggii clade are recovered as successive outgroups to Quetzalcoatlus in the Azhdarchidae. The previous azhdarchid species Montanazhdarcho minor and Radiodactylus langstoni are recovered as non-azhdarchid azhdarchiforms; Alanqa saharica and Argentinadraco barrealensis are thalassodromines; Cretornis hlavaci and Volgadraco bogolubovi are pteranodontians; and Bakonydraco galaczi is a tapejarine. Up to a dozen pterosaur lineages persist into the latest Cretaceous (Maastrichtian Age) including azhdarchids, pteranodontids, and nyctosauromorphs. In the Late Cretaceous, an ornithocheirid, cimoliopterids, a lonchodrachonid, a lonchodectid, pteranodontians, tapejarines, thalassodromines, a chaoyangopterine, and azhdarchiforms are present. The pterosaurs did not have a terminal decline in diversity and were increasing in species number at the end of the Cretaceous Period.
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Quetzalcoatlus is the largest flying organism ever known and one of the most familiar pterosaurs to the public. Despite a half century of interest, it remains very incompletely described. This shortfall is addressed here through a full morphological description of Quetzalcoatlus and the other pterosaur material of Big Bend National Park, Texas. The first reported material was described and named Quetzalcoatlus northropi by Douglas Lawson in 1975, but in two separate publications. A ruling by the International Commission of Zoological Nomenclature was required for the name to be made available. Review of the pterosaur fauna of the Park recovers three valid species of azhdarchid pterosaurs in the latest Cretaceous Period Javelina and Black Peaks formations. The size and occurrence of these species are correlated with depositional environment. The holotype of the giant Quetzalcoatlus northropi and six other giant specimens referred to it occur in stream-channel deposits, including the youngest reported pterosaur. The vast majority of specimens (200+) are from large pterosaurs found in the abandoned channel-lake deposits at Pterodactyl Ridge; they form a diagnosable natural group erected as the new species Quetzalcoatlus lawsoni. A moderate-sized partial skull and cervical series also found in the abandoned channel-lake deposits at Pterodactyl Ridge, but lower in the section, is distinct from both species and is erected as Wellnhopterus brevirostris, gen. et sp. nov. Overbank flood-plain facies preserve another eleven specimens of extreme size variation, including small azhdarchids. The Big Bend pterosaur fauna provides the greatest known sample of azhdarchid pterosaurs and three-dimensional pterosaur morphology.
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A new and articulated specimen of a pterosaur wing including upper arm, forearm, parts of the carpus and metacarpus, and a wing phalanx from Maastrichtian phosphatic deposits of Morocco are assigned to Tethydraco cf. regalis Longrich et al., 2018. The specimen comes from the village of Ouled Abdoun, close to the Oued Zem basin and its phosphatic mines (Morocco). The fossil is part of the collection of the Université Hassan II of Casablanca (ID Number FSAC CP 251). In the first part, the thesis presents a synthetic introduction about the morphology, anatomy, physiology and evolution of pterosaurs in order to offer a comprehensive framework on this fascinating group of extinct flying tetrapods. The main goal of this work is the taxonomic identification of the specimen, principally by morphological and morphometric/statistic analysis, based on the comparison with the most similar pterosaurs of the same epoch. Aspect of the humerus morphology and dimensional ratios of the wing elements suggest that T. cf. regalis is an azhdarchid rather than pteranodontid, as originally proposed. A high abundance of azhdarchid remains in the open marine setting of the Moroccan phosphates casts doubt on suggestions that Azhdarchidae were largely terrestrial pterosaurs.
A historic specimen described for the first time revealed important autapomorphic characters, permitting the definition of a new species, Javelinadactylus sagebieli gen. n. et sp. n., which represents the second toothless species from the Javelina Formation, Big Bend National Park of West Texas (United States of America). The remains of J. sagebieli (Azhdarchoidea: Tapejaridae) were found in 1986, but were never properly studied, and its taxonomic affinity remains undefined. The description is based on a partially articulated skull and mandible, which offer information on the anatomy of a single azhdarchoid pterosaur. J. sagebieli exhibit a large nasoantorbital fenestra, a rostral index of medium value and is assigned to the clade Thalassodrominae, a group of tapejarid pterosaurs that were reported exclusively from the Romualdo Formation of Brazil, with only two genera known. Thalassodromines are characterized by a typical cranial configuration with toothless jaws and a high and wide premaxilla bar, formed by sub-parallel or parallel borders. The new specimen described here represents the first record of the Tapejaridae group in the Maastrichtian of North America, and the cranial morphology of the new taxon increase the richest of the diversity of the azhdarchoid pterosaurs during the end of the Late Cretaceous, suggesting that the tapejarids were still diversifying in the Maastrichtian.
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The Araripe Basin is a rift basin originated by the rupture of the Gondwana paleocontinent, known as the most complete sedimentary record Interior Basin in the northeastern Brazil. The manuscript presents the state of art of the stratigraphy of the Araripe Basin, focusing on its evolution over time with respect to stratigraphic sequences based on unconformity surfaces, presenting new results and also making a critical review of stratigraphic classifications proposals aiming to elaborate an integrated classification. The first stratigraphic proposals were elaborated in a very comprehensive and simplified form. Over time, more detailed studies have been carried out, corroborating for a better and more refined compartmentalization of the present sedimentary packages. The 1980s were essential for the geoscientific production inherent to the geology of the basin due to the interest in the oil potential of the Brazilian basins. Nevertheless, even today the basin keeps motivating many researches that lead to a better understanding of local and regional geology. The Araripe Basin has five major sequences: Paleozoic, represented by the Cariri formation; Early Rift, consisting of the Brejo Santo formation and the bottom of the Missão Velha formation; Rift, formed by the upper part of the Missão Velha formation and throughout the Abaiara formation; and post- Rift, separated in two sequences: post-rift I constituted by the Barbalha, Crato, Ipubi and Romualdo formations, and post-rift II, characterized by the Araripina and Exu formations. New results are incorporated into the Missão Velha and Abaiara formations, whose distinction is shown here; also, in relation to the Barbalha and Cariri formations new data were gathered. This work focuses on the feasibility of the data, on the interpretations proposed according to the stratigraphic norms and the proposition of a sequential stratigraphic classification.
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A new giant pterosaur, Hatzegopteryx thambema, nov.gen., nov.sp., from the Maastrichtian Densuş-Ciula Formation of Romania is remarkable for its very large size (estimated wing span > or = 12 m) and for the robustness of its large skull, which may have been nearly 3 m long. The stout skull bones contrast with the usually thin and slender skull elements of other pterosaurs, and raise the question of how the weight of the skull was reduced in order to make flight possible. The answer probably lies in the very peculiar internal structure of the bones, which consists of a dense network of very thin trabeculae enclosing small alveoli. This structure is reminiscent of expanded polystyrene and, like it, probably combined strength with lightness.
Numerous remains of the azhdarchid pterosaur Quetzalcoatlus sp., have been recovered over the last twenty years from the Late Cretaceous (Maastrichtian) rocks in Big Bend National Park in Trans-Pecos Texas. Among more than 200 bones found at one locality are four incomplete skulls and mandibles, which provide the most complete information about cranial structures in the Azhdarchidae. What is currently known indicates that the Azhdarchidae is the sister group of the Tapejaridae from Early Cretaceous deposits in northeastern Brazil.
The fossil evidence is re-examined to determine the structure of Pteranodon ingens. New measurements include the cross-sections and thickness of the wing bones, the degree and direction of movement of the joints, and the size and position of major tendon and muscle insertions. From this data a reconstruction is made suitable for engineering and aerodynamic analysis. The reconstruction is based largely on Eaton's type specimen, 1175, and has a wing span of 6.95 m. The mass is estimated as 16.6 kg by calculating the volume of each part, making due allowance for the soft parts and cavities. The engineering design of the wing is considered in some detail. The shape deduced from the angles of the joints agrees well with that required for strength and aerodynamic efficiency. The strength of each part has been compared with the loads on it in gliding flight, showing that the structure is extremely well designed; it is strong enough everywhere, but with little unnecessary weight. Wind-tunnel experiments on model heads show that the sagittal crest was primarily a weight-saving device; by balancing the aerodynamic loads on the beak, it allows the neck muscles to be reduced, saving much more than its own weight. The performance of Pteranodon as a glider has been calculated, and compared with birds and manmade gliders. With a sinking speed of only 0.42 m/s at a flying speed of 8 m/s, Pteranodon is a superb low speed soaring aircraft, able to soar in weak thermals, or hill lift in very light winds. With its low stalling speed, it could also land very gently. Powered flight is considered, and it is shown that Pteranodon is just capable of level flight; but it is clearly primarily a glider. The environment in which Pteranodon lived is determined as far as possible from an analysis of the palaeobotany, palaeozoology and palaeoclimatology of the Cretaceous. The evidence points to a warmer and more uniform climate with lighter winds than today. This agrees well with Pteranodon's performance, which is ideally suited to light wind conditions. The mode of life is considered, showing that Pteranodon probably lived on sea cliffs facing the prevailing wind. After landing on the top, it would scrabble forwards (it could neither stand up nor walk) and hang from its hind feet over the edge. From here it could easily launch itself. When flying near the cliff it would soar in the hill lift; when far out at sea it would use the weak thermals generated by convection over the warm sea. Dynamic soaring and slope-soaring over the waves are not possible for such a slow-speed glider. Some consideration is given to methods of feeding, social organization and defence against predators. Finally it is suggested that extinction could have been due to climatic change, particularly an increase in the average wind speed at the end of the Cretaceous.
Metric data from the large collection of the Late Cretaceous pterosaur Pteranodon are bimodally distributed with a more numerous small size-class and a less numerous large size-class. The size-classes differ in cranial crest and pelvic structure. The small size-class has small cranial crests and deep puboischiadic plates that produce a large pelvic canal, while the large size-class has large cranial crests and shallow puboischiadic plates that produce a small pelvic canal. The difference in pelvic structure suggests that the small size-class is female. The various functions proposed for cranial crests are reviewed, and it is concluded that none can account for the difference in crest size. The conclusion is that the large crests of males are display structures.
It is suggested that the plates along the arched back and tail of Stegosaurus served an important thermoregulatory function as forced convection "fins." Wind tunnel experiments on finned models, internal heat conduction calculations, and direct observations of the morphology and internal structure of stegosaur plates support this hypothesis, demonstrating the comparative effectiveness of the plates as heat dissipaters, controllable through input blood flow rate, temperature, and body orientation (with respect to wind).
  • P Wellnhofer
P. Wellnhofer, Palaeontographica 187, 105 (1985).
  • R Zusi
R. Zusi, Publ. Nuttall Ornithol. Club 3, 1 (1962).
  • A W A Kellner
  • Y Hasegawa
  • J Vertebr
A. W. A. Kellner, Y. Hasegawa, J. Vertebr. Paleontol. 13 (suppl. to 3), 44A (1993).