Arthrological reconstructions of the pterosaur neck and their implications for the cervical position at rest.

The lack of any pterosaur living descendants creates gaps in the knowledge of the biology of this group, including its cervical biomechanics, which makes it difficult to understand their posture and life habits. To mitigate part of this issue, we reconstructed the cervical osteology and arthrology of three pterosaurs, allowing us to make inferences about the position of the neck of these animals at rest. We used scans of three-dimensionally preserved cervical series of Anhanguera piscator, Azhdarcho lancicollis and Rhamphorhynchus muensteri for the reconstructions, thus representing different lineages. For the recognition of ligaments, joint cartilages, and levels of overlapping of the zygapophyses, we applied the Extant Phylogenetic Bracket method, based on various extant birds and on Caiman latirostris. We inferred that pterosaur intervertebral joints were probably covered by a thin layer of synovial cartilage whose thickness varied along the neck, being thicker in the posterior region. Ignoring this cartilage can affect reconstructions. According to the vertebral angulation, their neck was slightly sinuous when in rest position. Our analyses also indicate that pterosaurs had segmented and supra-segmented articular cervical ligaments, which could confer stabilization, execute passive forces on the neck and store elastic energy.

Palaeohistology reveals an unusual periodontium and tooth implantation in a filter-feeding pterodactyloid pterosaur, Pterodaustro guinazui, from the Lower Cretaceous of Argentina.

Pterosaurs are an extinct group of Mesozoic flying reptiles, which exhibited high diversity with regard to their dentition. Although morphological features of pterosaur dentition have been described in detail in several contributions, the histology of tooth and tooth attachment tissues (i.e. periodontium) has been scarcely analysed to date for this clade. Here we describe and interpret the microstructure of the tooth and periodontium attachment tissues of Pterodaustro guinazui, a filter-feeding pterodactyloid pterosaur from the Lower Cretaceous of Argentina. The histological analysis of the lower jaw and its filamentous teeth verifies that the geometry of the implantation corresponds to an aulacodont condition (i.e. teeth are set in a groove with no interdental separation). This pattern departs from that recorded in other archosaurs, being possibly also present in other, non-closely related, pterosaurs. Regarding tooth attachment, in contrast to other pterosaurs, there is no direct evidence for gomphosis in Pterodaustro (i.e. the absence of cementum, mineralized periodontal ligamentum and alveolar bone). Nevertheless, the current evidence for ankylosis is still not conclusive. Contrary to that reported for other archosaurs, replacement teeth are absent in Pterodaustro, which is interpreted as evidence for monophyodonty or diphyodonty in this taxon. Most of the microstructural features are possibly related to the complex filter-feeding apparatus of Pterodaustro and does not appear to represent the general pattern of pterosaurs.

The closest evolutionary relatives of pterosaurs: What the morphospace occupation of different skeletal regions tell us about lagerpetids.

Exquisite discoveries and new interpretations regarding an enigmatic group of cursorial avemetatarsalians led to a new phylogenetic hypothesis regarding pterosaur affinities. Previously thought to be dinosaur precursors, lagerpetids are now considered to be the closest relatives to pterosaurs. This new hypothesis sheds light on a new explorable field, especially regarding the character acquisition and evolution within the pterosaur lineage. In the present study, the morphospace occupation of distinct skeletal regions of lagerpetids within the morphological spectrum of avemetatarsalians is investigated. This approach indicates which portions of the skeleton are more similar to the anatomy of pterosaurs and which portions present different homoplastic signals. The analyses demonstrate that the craniomandibular traits of lagerpetids are pterosaur-like, the pectoral girdle and forelimb are dinosauromorph-like and the axial skeleton and the pelvic girdle and hindlimb are unique and highly specialized among the analyzed sample. So, despite the close phylogenetic relationships, the postcranial skeleton of lagerpetids and pterosaurs are very different. The occurrence of two distinct and highly specialized groups of pterosauromorphs coexisting with a wide ecological range of dinosauromorphs during the Triassic suggests pressure for new niches occupation.

Anhanguera taxonomy revisited: is our understanding of Santana Group pterosaur diversity biased by poor biological and stratigraphic control?

BACKGROUND: Anhanguerids comprise an important clade of pterosaurs, mostly known from dozens of three-dimensionally preserved specimens recovered from the Lower Cretaceous Romualdo Formation (northeastern Brazil). They are remarkably diverse in this sedimentary unit, with eight named species, six of them belonging to the genus Anhanguera. However, such diversity is likely overestimated, as these species have been historically diagnosed based on subtle differences, mainly based on the shape and position of the cranial crest. In spite of that, recently discovered pterosaur taxa represented by large numbers of individuals, including juveniles and adults, as well as presumed males and females, have crests of sizes and shapes that are either ontogenetically variable or sexually dimorphic. METHODS: We describe in detail the skull of one of the most complete specimens referred to Anhanguera, AMNH 22555, and use it as a case study to review the diversity of anhanguerids from the Romualdo Formation. In order to accomplish that, a geometric morphometric analysis was performed to assess size-dependent characters with respect to the premaxillary crest in the 12 most complete skulls bearing crests that are referred in, or related to, this clade, almost all of them analyzed first hand. RESULTS: Geometric morphometric regression of shape on centroid size was highly statistically significant (p = 0.0091) and showed that allometry accounts for 25.7% of total shape variation between skulls of different centroid sizes. Premaxillary crests are both taller and anteroposteriorly longer in larger skulls, a feature consistent with ontogenetic growth. A new diagnosis is proposed for Anhanguera, including traits that are nowadays known to be widespread within the genus, as well as ontogenetic changes. AMNH 22555 cannot be referred to "Anhanguera santanae" and, in fact, "Anhanguera santanae", "Anhanguera araripensis", and "Anhanguera robustus" are here considered nomina dubia. DISCUSSION: Historically, minor differences in crest morphology have been used in the definition of new anhanguerid species. Nowadays, this practice resulted in a considerable difficulty in referring well-preserved skulls into known taxa. When several specimens are analyzed, morphologies previously believed to be disparate are, in fact, separated by a continuum, and are thus better explained as individual or temporal variations. Stratigraphically controlled excavations on the Romualdo Formation have showed evidence for faunal turnover regarding fish communities. It is thus possible that some of the pterosaurs from this unit were not coeval, and might even represent anagenetic morphotypes. Unfortunately, amateur collecting of Romualdo Formation fossils, aimed especially at commerce, resulted in the lack of stratigraphic data of virtually all its pterosaurs and precludes testing of these further hypotheses.

Premaxillary crest variation within the Wukongopteridae (Reptilia, Pterosauria) and comments on cranial structures in pterosaurs

ABSTRACT Cranial crests show considerable variation within the Pterosauria, a group of flying reptiles that developed powered flight. This includes the Wukongopteridae, a clade of non-pterodactyloids, where the presence or absence of such head structures, allied with variation in the pelvic canal, have been regarded as evidence for sexual dimorphism. Here we discuss the cranial crest variation within wukongopterids and briefly report on a new specimen (IVPP V 17957). We also show that there is no significant variation in the anatomy of the pelvis of crested and crestless specimens. We further revisit the discussion regarding the function of cranial structures in pterosaurs and argue that they cannot be dismissed a priori as a valuable tool for species recognition.

New azhdarchoid pterosaur (Pterosauria, Pterodactyloidea) with an unusual lower jaw from the Portezuelo Formation (Upper Cretaceous), Neuquén Group, Patagonia, Argentina

ABSTRACT A new azhdarchoid pterosaur from the Upper Cretaceous of Patagonia is described. The material consists of an incomplete edentulous lower jaw that was collected from the upper portion of the Portezuelo Formation (Turonian-Early Coniacian) at the Futalognko site, northwest of Neuquén city, Argentina. The overall morphology of Argentinadraco barrealensis gen. et sp. nov. indicates that it belongs to the Azhdarchoidea and probable represents an azhdarchid species. The occlusal surface of the anterior portion is laterally compressed and shows blunt lateral margins with a medial sulcus that are followed by two well-developed mandibular ridges, which in turn are bordered laterally by a sulcus. The posterior end of the symphysis is deeper than in any other azhdarchoid. This unique construction of the lower jaw suggests the existence of an elaborate interlocking mechanism with the upper jaw. Furthermore, although speculative, it is advocated here that Argentinadraco barrealensis might have used the lower jaw to obtain its prey by cutting or ploughing through unconsolidated sediment in shallow waters, a feeding behavior not previously proposed for pterosaurs.

A Jurassic pterosaur from Patagonia and the origin of the pterodactyloid neurocranium.

Pterosaurs are an extinct group of highly modified flying reptiles that thrived during the Mesozoic. This group has unique and remarkable skeletal adaptations to powered flight, including pneumatic bones and an elongate digit IV supporting a wing-membrane. Two major body plans have traditionally been recognized: the primitive, primarily long-tailed paraphyletic "rhamphorhynchoids" (preferably currently recognized as non-pterodactyloids) and the derived short-tailed pterodactyloids. These two groups differ considerably in their general anatomy and also exhibit a remarkably different neuroanatomy and inferred head posture, which has been linked to different lifestyles and behaviours and improved flying capabilities in these reptiles. Pterosaur neuroanatomy, is known from just a few three-dimensionally preserved braincases of non-pterodactyloids (as Rhamphorhynchidae) and pterodactyloids, between which there is a large morphological gap. Here we report on a new Jurassic pterosaur from Argentina, Allkaruen koi gen. et sp. nov., remains of which include a superbly preserved, uncrushed braincase that sheds light on the origins of the highly derived neuroanatomy of pterodactyloids and their close relatives. A µCT ray-generated virtual endocast shows that the new pterosaur exhibits a mosaic of plesiomorphic and derived traits of the inner ear and neuroanatomy that fills an important gap between those of non-monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids. These results suggest that, while modularity may play an important role at one anatomical level, at a finer level the evolution of structures within a module may follow a mosaic pattern.

Short note on a Pteranodontoid pterosaur (Pterodactyloidea) from western Queensland, Australia

Flying reptiles from Australia are very rare, represented mostly by isolated bones coming from the Early Cretaceous (Albian) Toolebuc Formation, which crops out in western Queensland. Among the first pterosaur specimens discovered from this deposit is a mandibular symphysis that some authors thought to have a particular affinity to species found in the Cambridge Greensand (Cenomanian) of England. It was further referred as a member of or closely related to one of the genera Ornithocheirus, Lonchodectes or Anhanguera. Here we redescribe this specimen, showing that it cannot be referred to the aforementioned genera, but represents a new species of Pteranodontoid (sensu Kellner 2003), here named Aussiedraco molnari gen. et sp. nov. It is the second named pterosaur from Australia and confirms that the Toolebuc deposits are so far the most important for our understanding of the flying reptile fauna of this country.

Répteis voadores da Austrália são muito raros e, na maioria dos casos, representados por ossos isolados procedentes da Formação Toolebuc (Cretáceo, Albiano), da região leste de Queensland. Entre os primeiros espécimes de pterossauros coletados nestes depósitos encontra-se uma sínfise mandibular que alguns autores acreditaram possuir afinidades com formas encontradas no Cambridge Greensand (Cenomaniano) da Inglaterra. O exemplar acabou sendo classificado como representando uma espécie pertencente ou proximamente relacionada aos gêneros Ornithocheirus, Lonchodectes ou Anhanguera. Neste trabalho nós redescrevemos este espécime e demonstramos que o mesmo não pode ser referido aos gêneros mencionados, mas representa uma nova espécie de Pteranodontóide (sensu Kellner 2003), aqui denominada de Aussiedraco molnari gen. et sp. nov. Este exemplar constitui a segunda espécie de pterossauro da Austrália a ser denominada e confirma a que os depósitos de Toolebuc são até o momento os mais importantes para a pesquisa de pterossauros desse país.

A pterodactyloid pterosaur from the Upper Cretaceous Lapurr sandstone, West Turkana, Kenya

An isolated pterosaurian caudal cervical (~ postcervical) vertebra was recovered from the Upper Cretaceous Lapurr sandstone ofWest Turkana, northwestern Kenya. The vertebral centrum is short, wide, and dorsoventrally compressed. Although the specimen is lightly built similar to most pterosaurs, it is here referred to Pterodactyloidea and tentatively to the Azhdarchidae in that it lacks pneumatic features on both the centrum and neural arch. This represents one of the few pterosaurs recovered from the entirety of Afro-Arabia, the first pterosaur recovered from the Cretaceous of East Africa, and, significantly, a specimen that was recovered from fluvial deposits rather than the near-shore marine setting typical of most pterosaur discoveries.

Uma vértebra cervical caudal isolada de pterossauro (~ pós-cervical) foi recuperada do Cretáceo Superior do arenito de Lapurr do Oeste de Turkana, noroeste do Quênia. O centro vertebral é curto, largo e comprimido dorsoventralmente. Embora o espécime seja leve como grande parte dos pterossauros, ele é aqui referido a Pterodactyloidea e tentativamente a Azhdarchidae no que diz respeito à ausência de características pneumáticas tanto no centro quanto no arco neural. Este representa um dos poucos pterossauros recuperados do conjunto Afro-Arábia, o primeiro pterossauro proveniente do Cretáceo do Leste da África e, significativamente, um espécime que foi recuperado de depósitos fluviais e não do cenário marinho próximo da costa típico da maioria das descobertas de pterossauros.

New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China

Two almost complete long-tailed pterosaurs from the Linglongta, Jianchang County, western Liaoning, China, are described and represent new taxa referred to the non-pterodactyloid clade Wukongopteridae. Kunpengopterus sinensis gen. et sp. nov. differs from other members of this clade mainly by the rounded posterior region of the skull, thick lacrimal process of the jugal and lack of a bony premaxillary crest. This species further shows a soft tissue crest above the frontal, a comparatively larger wing finger, and the proximal segment of the second pedal phalanx of the fifth toe shorter than in other wukongopterids. The second new species is referred to the genus Darwinopterus, D. linglongtaensis sp. nov. based on the posterior region of the skull. It further differs from other wukongopterid pterosaurs by the thin lacrimal process of the jugal, foramen on nasal process rounded, and by having the second pedal phalanx of the fifth toe less curved (115°). Several differences among the Wukongopteridae can be found in the dentition and the feet, suggesting that they might have occupied slightly different ecological niches. The long-tailed Changchengopterus pani is tentatively referred to this clade and new diagnosis for the wukongopterids Wukongopterus lii and Darwinopterus modularis is provided.

Dois novos pterossauros de cauda longa procedentes de Linglongta, Jianchang County da região oeste de Liaoning, China, são descritos e referidos ao clado Wukongopteridae. Kunpengopterus sinensis gen. et sp. nov. difere dos demais integrantes desse clado basicamente pela região mais arredondada da parte posterior do crânio, pelo espesso processo lacrimal do jugal e pela ausência de uma crista óssea premaxilar. Esta espécie apresenta uma crista formada por tecido mole acima da região frontal e possui o dedo alar proporcionalmente maior do que nos demais wukongopterídeos. A segunda espécie é referida ao gênero Darwinopterus, D. linglongtaensis sp. nov., com base na região posterior do crânio. Difere dos deais pterossauros wukongopterídeos por possuir o processo lacrimal do jugal delgado, o forâmen no processo nasal arredondado e pela condição menos curvada da segunda falange do quinto dígito do pé. As principais diferenças entre os Wukongopteridae são encontradas na dentição e nos pés, o que sugere que estes ocupavam nichos ecológicos ligeiramente distintos. O pterossauro de cauda longa Changchen-gopterus pani também é tentativamente referido a esse clado. Novas diagnoses para os wukongopterídeos Wukongopterus lii e Darwinopterus modularis são apresentadas.

Comments on the Pteranodontidae (Pterosauria, Pterodactyloidea) with the description of two new species

Considered one of the best known flying reptiles, Pteranodon has been subject to several reviews in the last century. Found exclusively in the Upper Cretaceous Niobrara Formation and Pierre Shale Group 11 species have been attributed to this genus (excluding the ones presently regarded as representing Nyctosaurus). While reviewers agree that this number is inflated, there is disagreement on how many species can be identified. The last review recognized only two species (Pteranodon longiceps and Pteranodon sternbergi) both being sexually dimorphic. Based on several cranial features, some specimens previously referred to the genus Pteranodon are re-evaluated leading to the recognition of the following species, two of which new that are described here: Pteranodon longiceps, Geosternbergia sternbergi, Geosternbergia maiseyi sp. nov., and Dawndraco kanzai gen. et sp. nov. They differ mainly by features such as the direction and extension of the frontal crest, the angle and extension of the posterior process of the premaxillae, the shape and extension of the lower temporal fenestra and the length and proportion of the rostrum. The procedures to recognize a pterosaur species are also discussed here, and must take into account primarily morphology, in conjunction with stratigraphic and geographic data. Although well aware that changes in morphology not always reflect taxonomy, the lack of stratigraphic data and the limited number of specimens that can be confidently assigned to one species hampers our understanding on the morphological variations as a function of ontogeny, individual variation and sexual dimorphism. Although the present study has not eliminated the possibility to recognize such differences, caution is needed before models are generalized for pterosaurs.

Considerado um dos répteis voadores melhor conhecidos, Pteranodon foi objeto de várias revisões no século passado. Encontrado exclusivamente na Formação Niobrara e no Grupo Pierre Shale (ambas do Cretáceo Superior) 11 espécies foram atribuídas a este gênero (além das três presentemente classificadas em Nyctosaurus). Apesar da concordância entre os revisores que este número está inflado, existe discordância de quantas espécies podem ser reconhecidas. A última revisão limitou a existência de apenas duas espécies (Pteranodon longiceps and Pteranodon sternbergi), ambas exibindo dimorfismo sexual. Tomando como base diversas características observadas no crânio, alguns exemplares anteriormente referidos ao gênero Pteranodon foram re-avaliados e levaram à conclusão da existência das seguintes espécies, duas novas e descritas aqui: Pteranodon longiceps, Geosternbergia sternbergi, Geosternbergia maiseyi sp. nov. e Dawndraco kanzai gen. et sp. nov. Estas se diferenciam por feições tais como a extensão e direção da crista formada pelo frontal, da inclinação e extensão do processo posterior das pré-maxilas, da forma e tamanho da fenestra temporal inferior e da proporção do rostro. Também é discutido nesse trabalho o procedimento de como se reconhece uma espécie de pterossauro, que deve levar em conta principalmente dados morfológicos, acompanhados de informações estratigráficas e geográficas. Existe a consciência geral de que a morfologia pode variar sem que necessariamente estas mudanças estejam ligadas a questões taxonômicas. No entanto, a ausência de dados estratigráficos detalhados, aliada ao número limitado de exemplares que possam ser consideradas com um bom nível de segurança como pertencentes a uma determinada espécie, dificulta sobremaneira o nosso entendimento de como a morfologia pode variar em função de ontogenia, variações individuais e dimorfismo sexual. Apesar do presente estudo não eliminar a possibilidade de reconhecer estas variações, cuidado deve ser empregado antes que modelos sejam generalizados para os pterossauros.

An unusual long-tailed pterosaur with elongated neck from western Liaoning of China

A new long-tailed pterosaur, Wukongopterus lii gen. et sp. nov, is described based on an almost complete skeleton (IVPP V15113) representing an individual with an estimated wing span of 730 mm. The specimen was discovered in strata that possibly represent the Daohugou Bed (or Daohugou Formation) at Linglongta, Jianchang, Liaoning Province, China. Wukongopterus lii is a non-pterodactyloid pterosaur diagnosed by the first two pairs of premaxillary teeth protruding beyond the dentary, elongated cervical vertebrae (convergent with Pterodactyloidea), and a strongly curved second pedal phalanx of the fifth toe. The specimen further has a broken tibia that indicates an injury occurred while the individual was still alive. Taphonomic aspects provide indirect evidence of an uropatagium, supporting the general hypothesis that at least all non-pterodactyloid pterosaurs show a membrane between the hind limbs. A phylogenetic analysis including most non-pterodactyloid pterosaurs shows that Wukongopterus lii gen. et sp. nov. lies outside the Novialoidea, being cladistically more primitive than the Rhamphorhynchidae and Capylognathoides. This analysis differs from previous studies and indicates that more work is needed before a stable picture of non-pterodactyloid pterosaur relationships is achieved.

Um novo pterossauro de cauda longa, Wukongopterus lii gen. et sp. nov., é descrito baseado em um esqueleto quase completo (IVPP V15113) de um indivíduo com abertura alar estimada em 730 mm. O exemplar foi encontrado nas camadas Daohugou (ou Formação Daohugou) em Linglongta, Jianchang, Província de Liaoning, China. Wukongopterus lii é um pterossauro não-pterodactilóide diagnosticado pela presença de dois pares de dentes pré-maxilares posicionados antes do início do dentário, vertebras cervicais alongadas (convergente com os Pterodactyloidea) e a segunda falange do quinto dígito do pé fortemente curvada. Este espécime também apresenta uma tíbia quebrada indicando que a quebra ocorreu com o animal em vida. Evidências tafonômicas apresentam dados indiretos da presença de um uropatágio, corroborando com a hipótese de que pelo menos os não-pterodactilóides possuíam uma membrana entre os seus membros posteriores. Uma análise filogenética incluindo vários pterossauros não-pterodactilóides resulta no posicionamento de Wukongopterus lii gen. et sp. nov. fora dos Novialoidea, sendo cladisticamente mais primitivo do que os Rhamphorhynchidae e Campylognathoides. Esta nova análise filogenética difere de resultados anteriores, indicando que mais trabalhos são necessários até que uma estabilidade da relação de parentesco entre os pterossauros não-pterodactilóides seja alcançada.

On two pterosaur humeri from the Tendaguru beds (Upper Jurassic, Tanzania)

Jurassic African pterosaur remains are exceptionally rare and only known from the Tendaguru deposits, Upper Jurassic, Tanzania. Here we describe two right humeri of Tendaguru pterosaurs from the Humboldt University of Berlin: specimens MB.R. 2828 (cast MN 6661-V) and MB.R. 2833 (cast MN 6666-V). MB.R. 2828 consists of a three-dimensionally preserved proximal portion. The combination of the morphological features of the deltopectoral crest not observed in other pterosaurs suggests that this specimen belongs to a new dsungaripteroid taxon. MB.R. 2833 is nearly complete, and because of a long and round proximally placed deltopectoral crest it could be referred to the Archaeopterodactyloidea. It is the smallest pterosaur from Africa and one of the smallest flying reptiles ever recorded. These specimens confirm the importance of the Tendaguru deposits for the Jurassic pterosaur record. This potential, however, has to be fully explored with more field work.

Fragmentos de pterossauros africanos do Jurássico são excepcionalmente raros e conhecidos apenas dos depósitos de Tendaguru, Jurássico Superior, Tanzânia. Este estudo descreve dois úmeros direitos de pterossauros de Tendaguru depositados na Universidade Humboldt de Berlim: espécimes MB.R. 2828 (réplica MN 6661-V) e MB.R. 2833 (réplicaMN 6666-V). MB.R. 2828 consiste em uma porção proximal com preservação tridimensional. Características morfológicas combinadas da crista deltopeitoral não observadas em outros pterossauros sugerem que este espécime pertença a um novo táxon dsungaripteróide. B.R. 2833 é quase completo e, por causa da sua crista deltopeitoral extensa e arredondada, posicionada proximalmente, pode ser associado a Archaeopterodactyloidea. De qualquer forma, este é o menor pterossauro da África e um dos menores já registrados. Estes espécimes corroboram a importância dos depósitos de Tendaguru para registros de pterossauros jurássicos. Este potencial, no entanto, deve ser mais amplamente explorado com um maior número de trabalhos de campo.