The taxonomy, geographic distribution, and paleoenvironmental context of azhdarchid pterosaurs are reviewed. All purported pteranodontid, tapejarid, and azhdarchid specimens from the Cenomanian Kem Kem beds of Morocco are referred codings di alcolismo in Volgograd a single azhdarchid taxon, Alanqa saharica.
Azhdarchids likely inhabited a variety of environments, but were abundant near large lakes and rivers and most common in nearshore marine paleoenvironments. Azhdarchid pterosaurs Azhdarchidae are the most derived, successful and stratigraphically youngest group of pterosaurs and flourished during the Late Cretaceous after the decline of most other pterosaur groups Witton ; Witton and Naish The toothed pterodactyloids Ornithocheiridae dominated during the Early Cretaceous and earliest Late Cretaceous Cenomanian and early Turonian.
Starting in the late Turonian all pterodactyloids were toothless: Pteranodontidae and Nyctosauridae in the Western Hemisphere and Azhdarchidae worldwide. This shift in dominance from toothed to toothless pterodactyloids apparently reflects some fundamental changes in Cretaceous ecosystems, which we still poorly understand.
The fossil record of pterosaurs is patchy and confined mostly to Konservat-Lagerstätten where exceptional depositional conditions facilitated preservation of fragile pterosaur bones Butler et al. Unfortunately, such Lagerstätten are very rare for the Late Cretaceous when most of the evolutionary history of Azhdarchidae took place. Azhdarchidae currently represents a real nightmare for pterosaur taxonomists: most taxa are known from few fragmentary bones, which often do not overlap between named taxa, the codings di alcolismo in Volgograd articulated skeletons are poorly preserved Zhejiangopterusand the best available postcranial material Quetzalcoatlus has remained undescribed for forty years.
Nevertheless, the number of azhdarchid localities is impressive and undoubtedly reflect the important role that these pterosaurs played in the Late Cretaceous ecosystems. The imperfect nature of the azhdarchid fossil record poses a problem for the taxonomic attribution of their isolated bones. It is a common practice to confine azhdarchid taxa to few diagnostic bones whereas other bones in the locality are classified as Azhdarchidae indet. This superficially objective approach actually creates two taxa for the locality, a named taxon and a taxon left in open nomenclature Azhdarchidae indet.
In this particular case, the number of codings di alcolismo in Volgograd taxa in a given locality must not be multiplied unless it can be demonstrated by homologous skeletal elements with different structure. Another aspect of this problem is the creation of multiple named, presumably valid, closely related azhdarchid taxa based on materials from the same stratigraphic unit and the same or neighboring localities.
For azhdarchids, this practice was introduced by Langston : who referred the smaller specimens of Texas pterosaur to Quetzalcoatlus sp.
This is wrong and misleading. Ontogenetic, sexual, and individual variation is to be expected in the population whereas the existence of closely related species in the same ecosystem is uncommon.
Variability is the null hypothesis and taxonomic distinction should only be hypothesized if the size and morphological variation cannot be accounted for by ontogeny, sexual dimorphism, or allometric scaling. Ignoring of this principle led to unjustified taxonomic inflation and unfounded hypotheses on taxic diversity, niche partitioning, and other aspects of azhdarchid evolutionary history Butler et al. This paper provides a review of the taxonomy and distribution of Azhdarchidae based on the principles outlined above.
The revised and annotated list of azhdarchid localities is used to assess the preferred paleoenvironments of azhdarchid pterosaurs. Alanqa saharica. I refer to this species all azhdarchid remains from the Cenomanian Kem Kem beds of Morocco, which include edentulous jaw fragments, cervical vertebrae, and a fragmentary humerus Wellnhofer and Buffetaut ; Kellner et al.
The jaw fragments show some variation, which was considered taxonomically significant by previous authors who assigned these specimens to three different families: AzhdarchidaeTapejaridaeand Pteranodontidae. The ontogenetic interpretation of this variation is more parsimonious Fig.
The mandibular fragments could be easily distinguished by their cross-section, where the dorsal convex part is not deeper than half of the dentary depth.
The narrow ventral part actually is a mandibular sagittal crest, which does not project beyond the straight ventral border of the dentary in contrast to the dentary sagittal crest in ornithocheirids.
Furthermore, on the dorsal surface of the mandibular symphysis, there is a variably developed medial crest whereas the ventral surface of the rostrum is gently concave.
Also, the ventral side in lateral profile is less steep compared with the dorsal side of the rostrum Fig. Among the known fragments of the rostrum, BSP Here the rostrum is relatively short and the sagittal crest, poorly differentiated from the rest of premaxilla, begins close to the jaw tip Fig. Codings di alcolismo in Volgograd smallest fragment CMN most codings di alcolismo in Volgograd represents the tip of the rostrum of an adult or subadult individual, which has the sagittal crest far away from the rostral tip Fig.
The more complete specimen BSP At this stage there is no indication of the sagittal crest in the cross-section of the rostrum. The crest was likely confined to the more posterior part of the skull. The mandibular symphysis BSP It can also not be ruled out that sagittal crest codings di alcolismo in Volgograd present only in males. Ontogenetic interpretation of the known jaw fragments of Alanqa saharica all drawn at the same magnification; specimen numbers are shown on the figure; reversed codings di alcolismo in Volgograd are marked by asterisk.
A—D rostrum fragments, in lateral and ventral views E, F fragments of mandibular symphysis, in dorsal and lateral views. The arrow indicates the beginning of the sagittal crest on the cross sections of the rostra. Abbreviations : naof — nasoantorbital fenestra; sc — sagittal crest. The known complete cervical vertebrae of Alanqa saharica Rodrigues et al. The humerus of Alanqa saharica Rodrigues et al.
Azhdarcho lancicollis. The nominal genus of Azhdarchidae is known from fragmentary codings di alcolismo in Volgograd abundant specimens from the Turonian Bissekty Formation at Dzharakuduk, Kyzylkum Desert, Uzbekistan Nesov c ; Averianov Bakonydraco galaczi.
Here I refer to this taxon all pterosaur remains currently known from this locality. In the holotype mandible MTM V In MTM V The specimen MTM V In a recent phylogenetic analysis by Andres and Myers Bakonydraco galaczi clustered in Tapejaridae. Indeed, this taxon is similar to juvenile specimens of Tapejara wellnhoferi SMNK PAL in the lateral profile of the codings di alcolismo in Volgograd symphysis, but the older specimens of the latter taxon have prominent ventral dentary crest AMNHwhich has not been reported for Bakonydraco galaczi.
In Tapejara wellnhoferi the dentary rami are separated posterior to the beak, which is the primitive condition for pterosaurs. The coalesced dentary rami posterior to the beak are present also in Quetzalcoatlus Kellner and Langston : fig. Aralazhdarcho bostobensis.
The taxon is known from several isolated bones, including atlas-axis and anterior fragment of mid-cervical vertebra, from the Santonian — lower Campanian Bostobe Formation at Shak-Shak in Kyzylorda Province of Kazakhstan Nesov c ; Averianovb. Samrukia nessovi is based on a mandible fragment from the Bostobe Formation of the nearby Akkurgan locality, originally misidentified as a bird Naish et al. Samrukia nessovi is referred here to Azhdarchidae and tentatively considered codings di alcolismo in Volgograd subjective junior synonym of Codings di alcolismo in Volgograd bostobensis.
Aralazhdarcho bostobensis is similar to Quetzalcoatlus in the structure of posterior part of the mandible poorly known in other azhdarchid taxa.
It differs from all known azhdarchid taxa in the reduction of pneumatic foramina lateral to the neural canal on the cervical vertebrae and the convex rather than saddle-shaped humeral head. Volgadraco bogolubovi.
The snout fragment Averianov et al. In addition to the previously described specimens, a distal syncarpal was recently found at the type locality. This taxon is likely synonymous with Bogolubovia orientalisbased codings di alcolismo in Volgograd cervical vertebra fragment from the Rybushka Formation at Malaya Serdoba in Penza Province, Russia Bogolyubov ; Nesov and Yarkov Because the holotype of Volgadraco bogolubovi is more diagnostic and that of Bogolubovia orientalis is lost will be better codings di alcolismo in Volgograd treat the latter taxon as a nomen dubium and refer all azhdarchid bones from Rybushka Formation to Volgadraco bogolubovi.
Codings di alcolismo in Volgograd linhaiensis. The geological age of this unit is The skeletons retain some poorly preserved soft-tissue remains, but the preservation of the bones is rather poor.
The holotype ZMNH M is the skull without cranial crest and apparently belongs to an immature individual. Aerotitan sudamericanus. Aerotitan sudamericanus was originally distinguished by the proportions of the rostrum and the pattern of neurovascular foramina Novas et al. Indeed the anterior rostrum fragment is very narrow transversely, suggesting that the entire rostrum was quite long. This character distinguishes Aerotitan sudamericanus from all azhdarchid taxa except Quetzalcoatluswhich has a similarly long and narrow rostrum Kellner and Langston : figs 2, 3.
The anterior part of the rostrum in Quetzalcoatlus has not been illustrated in ventral view, but the mandibular symphysis Kellner and Langston : fig. Aerotitan has a single row of neurovascular foramen along the alveolar margin of the rostrum Novas et al. In Alanqathere is a dorsal row and at least one foramen in ventral row Novas et al. The pattern of neurovascular foramina is highly variable in the known rostral fragments of Azhdarcho lancicollis ZIN PH collection.
They can be altogether absent, irregularly spaced, or arranged in parallel rows on the palate, form an almost interrupted groove near the alveolar margin on the lateral surface, be situated in the middle of the lateral surface or closer to the dorsal margin, or form two rows on codings di alcolismo in Volgograd lateral aspect, one along the alveolar border codings di alcolismo in Volgograd another closer to mid-height. The larger specimens usually have fewer foramina.
This is likely correlated with the slowdown of the growth of the keratinous sheath. According to Novas et al. However, this may be due to the poor preservation of the bony surface in described specimens Kellner and Langston ; these foramina are present in all other azhdarchids. Aerotitan is very similar to Quetzalcoatlus in narrowness of the rostrum and these taxa may be closely related.
Except the neurovascular foramina, which are highly variable in azhdarchids, the only significant difference between the codings di alcolismo in Volgograd taxa is the convex profile of alveolar border in Aerotitan. Phosphatodraco mauritanicus. Kellner : thought that the "elongated element [on the holotype] that in the original description was codings di alcolismo in Volgograd as the codings di alcolismo in Volgograd cervical vertebra is actually formed by two cervical elements, the first being the third and the second the fourth, respectively.
This interpretation is improbable and was previously dismissed by Pereda Suberbiola et al. There are no remnants of zygapophyses composed of dense bone in the breakage within the fifth cervical whereas other zygapophyses are well preserved. Phosphatodraco mauritanicus is distinct in having relatively long cervical VIII with high neural spine restricted to the posterior part of the vertebra.
According to the original description, Phosphatodraco has no pneumatic canals lateral to the neural canal. However, this could only be established for cervical IX Pereda Suberbiola codings di alcolismo in Volgograd al. The lateral pneumatic foramina are present on cervical IX in Azhdarchobut absent in Volgadraco and Quetzalcoatlus Averianov et al. Arambourgiania philadelphiae. A giant pterosaur known from a mid-cervical vertebra and wing phalanx fragments from the Maastrichtian phosphorites of the Balqa Group at Ruseifa near Amman, Jordan Frey and Martill ; Steel et al.
The holotype vertebra UJA VF-1 was originally misinterpreted as a wing metacarpal Arambourgand reinterpreted as a cervical by Lawson b. The original generic name of this largest flying creature, Titanopteryx Arambourg,turned out to be preoccupied ironically by a name for one of the smallest flying animal, a black fly Simulidaeand was replaced by Arambourgiania Nesov and Yarkov The holotype of Arambourgiania philadelphiae is distinct in being oval in cross-section, with the cotylar and condylar articular surfaces of the centrum higher than wide, and having vertically oriented postexapophyses.