Istiodactyliform

Ornithocheiromorpha (from Ancient Greek, meaning "bird hand form") is a group of pterosaurs within the suborder Pterodactyloidea. Fossil remains of this group date back from the Early to Late Cretaceous periods (Valanginian to Turonian stages), around 140 to 92.5 million years ago. Ornithocheiromorphs have been discovered worldwide except Antarctica, though most genera have been recovered in Europe, Asia and South America. They were the most diverse and successful pterosaurs during the Early Cretaceous, but throughout the Late Cretaceous they were replaced by pteranodontians and azhdarchoids. The Ornithocheiromorpha was defined in 2014 by Andres and colleagues, and they made Ornithocheiromorpha the most inclusive clade containing ''Ornithocheirus'', but not ''Pteranodon''.

Ornithocheiromorphs are considered to be some of the largest animals to have ever flown. Members of this group are also regarded to have some of the largest pterosaur wingspans, such as the one estimated for the huge ''Tropeognathus'', though still not as large as those estimated for the azhdarchids, which may have reached up to . When ornithocheiromorphs first appeared, they were initially scavengers, consisting in a more terrestrial setting, but their success had made them the top predators of the skies, as well as the most common type of fish-eating pterosaur throughout the early Late Cretaceous. Some paleontologists also consider ornithocheiromorphs an earlier step of evolution to the pteranodontians, this is due to the similar flying techniques and flight locomotions, as well as their diet, which mainly consisted of fish, and therefore also hunted very similarly. Ornithocheiromorphs also flew like soaring birds, keeping their wings stretched and rarely flapping.

History of research

Early discoveries

The first specimens of ornithocheiromorphs were unearthed at a chalk pit near Burham in Kent, England. In 1846, British paleontologist James Scott Bowerbank named and described the remains found as ''Pterodactylus giganteus'', as it was common at that time to assign any new described pterosaur species to ''Pterodactylus''. In the same chalk pit as ''P. giganteus'', two other pterosaur species were discovered. The first was named in 1851 by Bowerbank as ''Pterodactylus cuvieri'', in honor of the prominent German naturalist and zoologist Georges Cuvier, while the second was described in the same year by British paleontologist Sir Richard Owen as ''Pterodactylus compressirostris''.Owen, R. (1851). Monograph on the fossil Reptilia of the Cretaceous Formations. ''The Palaeontographical Society'' 5(11):1-118. ''P. compressirostris'' later became the type species of a newly created genus called ''Lonchodectes'' (meaning "lance biter") in a review by English paleontologist Reginald Walter Hooley in 1914. Confusingly, this species was also long regarded, incorrectly, as the type species of ''Ornithocheirus''.

In 1861, further pterosaur specimens were found in the UK, and were given the new species ''Pterodactylus simus'' by Owen. British paleontologist Harry Govier Seeley then created the new genus ''Ornithocheirus'' for the new species in the same year, the generic name translating as "bird hand" is due to the notion of the time that pterosaurs were the ancestors of modern birds. In 1870, Seeley reassigned the species ''Pterodactylus cuvieri'' as ''Ornithocheirus cuvieri''. In 1874, Richard Owen proposed two new genera, ''Coloborhynchus'', meaning "maimed beak", and ''Criorhynchus'', meaning "ram beak". While ''Coloborhynchus'' consisted in a totally new type species, ''C. clavirostris'', as well as two other species reassigned from ''Ornithocheirus'', ''Criorhynchus'' consisted entirely of former ''Ornithocheirus'' species, including ''O. simus'', which was later reassigned by Owen as ''Criorhynchus simus''.

In 2013, Brazilian paleontologists Taissa Rodrigues & Alexander Kellner made a deeper analysis on the species ''Pterodactylus cuvieri''. In the analysis, they stated that it needed a separate genus, and assigning it to ''Ornithocheirus'' was inappropriate, therefore, they created the new genus called ''Cimoliopterus'', with the new resulting combination ''Cimoliopterus cuvieri''. In the same study, Rodrigues & Kellner also reviewed the species ''Pterodactylus giganteus'', and reassigned it to a newly created genus called ''Lonchodraco'', this resulted in a new combination called ''Lonchodraco giganteus''.

In 1887, Seeley had described new fossil remains from the Isle of Wight, an island off the coast of southern England. He thought it belonged to some kind of bird-like creature, which he named it '' Ornithodesmus cluniculus''. Seeley also reported another specimen found on the same site. He then considered it another species of ''Ornithodesmus''. In 1901, Seeley named this new species as ''O. latidens'', meaning "wide tooth". Later, Reginald Hooley discussed ''O. latidens'' in detail, based on specimens he had found, which led ''Ornithodesmus'' to be placed within a new family called Ornithodesmidae. Paleontologist Charles William Andrews however, had expressed doubts as to whether ''O. latidens'' belonged in the genus ''Ornithodesmus'', as the vertebrae of the specimen of that genus was based on differed markedly from those of Hooley's specimen.

In 1993, the British paleontologists Stafford C. Howse and Andrew C. Milner concluded that the holotype sacrum and only specimen of ''O. cluniculus'' didn't belong to a pterosaur, but instead to a maniraptoran theropod dinosaur. They also pointed out that no detailed attempts had been made to compare the sacrum of ''O. cluniculus'' with those of pterosaurs, and that ''O. latidens'' had in effect been treated as the type species of the genus ''Ornithodesmus''. Howse, Milner, and David Martill in 2001, moved "''O.''" ''latidens'' to a new genus called ''Istiodactylus''. They had also named a new family called Istiodactylidae, with ''Istiodactylus'' as the only member.

Discoveries outside Europe

Other important ornithocheiromorph discoveries include the anhanguerids ''Tropeognathus'' and '' Anhanguera'' from the Romualdo Formation in Brazil.Campos, D. de A., and Kellner, A. W. (1985). "Um novo exemplar de ''Anhanguera blittersdorffi'' (Reptilia, Pterosauria) da formação Santana, Cretaceo Inferior do Nordeste do Brasil." In Congresso Brasileiro de Paleontologia, Rio de Janeiro, Resumos, p. 13. ''Tropeognathus'' was described with its type species, ''T. mesembrinus'' in 1987 by German paleontologist Peter Wellnhofer. The generic name is derived from Greek τρόπις, ''tropis'', meaning "keel", and γνάθος, ''gnathos'', meaning "jaw". The specific name is derived from Koine ''mesembrinos'', "of the noontide", simplified as "southern", in reference to the provenance from the Southern hemisphere. The description then led to an enormous taxonomic confusion.Wellnhofer, P. (1987). ''The Illustrated Encyclopedia of Pterosaurs''. New York: Barnes and Noble Books. pp. 124. . In 1989, Brazilian paleontologist Alexander Kellner considered it an ''Anhanguera mesembrinus'', then a ''Coloborhynchus mesembrinus'' by Veldmeijer in 1998, and then a ''Criorhynchus mesembrinus'' in 2001 by German paleontologist Michael Fastnacht. ''T. mesembrinus'' was then considered a junior synonym of ''Ornithocheirus simus'' by British paleontologist David Unwin in 2001, but he then proposed an ''Ornithocheirus mesembrinus'' in 2003.Unwin, D.M., 2001, "An overview of the pterosaur assemblage from the Cambridge Greensand (Cretaceous) of Eastern England", ''Mitteilungen aus dem Museum für Naturkunde in Berlin, Geowissenschaftliche Reihe'' 4: 189–221 In 2013 however, Taissa Rodrigues and Alexander Kellner concluded that ''Tropeognathus'' would be valid again, and containing only ''T. mesembrinus'', the type species.

A discovery in Asia, specifically northwestern China, was reported in 2006. The lake sediments allowed an exceptional preservation of fossils, and therefore paleontologists Qiu Zhanxiang and Wang Banyue started official excavations. Part of the findings consisted of dense concentrations of pterosaur bones, associated with soft tissues and eggs. In 2014, a new species was named and described: '' Hamipterus tianshanensis''. It was named by Wang Xiaolin, Alexander Kellner, Jiang Shunxing, Wang Qiang, Ma Yingxia, Yahefujiang Paidoula, Cheng Xin, Taissa Rodrigues, Meng Xi, Zhang Jialiang, Li Ning, and Zhou Zhonghe. The generic name ''Hamipterus'' combines that of the Hami region, with the word ''pteron'', meaning "wing", and the specific name refers to the provenance from the Tian Shan, a mountain range.

Description

Size

Ornithocheiromorphs were large pterosaurs, with wingspans normally ranging between . ''Istiodactylus'' for example, had a wingspan ranging from , with the most complete known skull estimated to have been about in length, based on a long-lost fragment of its jaw reported in 2012. Though its jaws measured only , which was less than 80 percent of the skull's length. Anhanguerids and were typically larger than others of the group and were more successful within the food chain rather than other ornithocheiromorphs, one reason is because of their large size, for example, ''Tropeognathus mesembrinus'', had a normal wingspan of about , and as the maximum estimate. Another species which was impressively large is ''Coloborhynchus capito'', with a total skull length that could have been up to , leading to an estimated wingspan of .Martill, D.M. and Unwin, D.M. (2011). "The world's largest toothed pterosaur, NHMUK R481, an incomplete rostrum of ''Coloborhynchus capito'' (Seeley 1870) from the Cambridge Greensand of England." ''Cretaceous Research'', (advance online publication). However, this species may belong to a different genus called '' Nicorhynchus''.

Skull and crests

Most anhanguerids bore distinctive convex "keeled" crests on their snout and underside of their mandible, this was well developed in several genera such as ''Tropeognathus''.Veldmeijer, A.J. (2006).
Toothed pterosaurs from the Santana Formation (Cretaceous; Aptian-Albian) of northeastern Brazil. A reappraisal on the basis of newly described material
." Tekst. - Proefschrift Universiteit Utrecht. The similar ''Anhanguera'' possessed jaws that were tapered in width, but expanded into a broad, spoon-shaped rosette at the tip. The jaws are distinguished from its relatives by several differences in the crest and teeth: unlike its close relatives ''Coloborhynchus'' and ''Ornithocheirus'', the crest on the upper jaw of ''Anhanguera'' didn't begin at the tip of the snout, therefore, it was set farther back on the skull.Kellner, A.W.A. and Tomida, Y. (2000). "Description of a new species of ''Anhanguera'' (Pterodactyloidea) with comments on the pterosaur fauna from the Santana Formation (Aptian–Albian), northeastern Brazil." Tokyo, National Science Museum (''National Science Museum Monographs'', 17).

Other anhanguerids like '' Cearadactylus'' had its first preparations with many serious mistakes: the front of the snout and the lower jaws were confused leading to a reconstruction in which the anterior part of the head was upside down.Leonardi, G. & Borgomanero, G. (1985). "''Cearadactylus atrox'' nov. gen., nov. sp.: novo Pterosauria (Pterodactyloidea) da Chapada do Araripe, Ceara, Brasil." ''Resumos dos communicaçoes VIII Congresso bras. de Paleontologia e Stratigrafia'', 27: 75–80. Some of the teeth were extensively restored and enlarged until the wider front of the jaws showed very large and robust teeth projecting outward. With this arrangement, the maxilla was kinked, and its interlocking teeth suggested that ''Cearadactylus'' had a piscivourous diet, allowing the animal to keep hold of slippery fish. Another smaller genus similar to ''Cearadactylus'' is ''Guidraco''. Its holotype skull has a length of , which makes it smaller than other genera. The skull is very elongated however, and a hollow profile is seen, but not very pointed, as the upper edge and the line of the jaw run nearly parallel over most of their length.

Even though most ornithocheiromorphs didn't have a cranial crest like the closely related pteranodontids, there were some exceptions, this included ''Caulkicephalus'' and ''Ludodactylus''.Frey, E., Martill, D., and Buchy, M. (2003). A new crested ornithocheirid from the Lower Cretaceous of northeastern Brazil and the unusual death of an unusual pterosaur. In: Buffetaut, E., and Mazin, J.-M. (eds.). ''Evolution and Palaeobiology of Pterosaurs''. ''Geological Society Special Publication'' 217:56-63. . ''Caulkicephalus'' had a rounded snout, very similar to that of ''Ornithocheirus'' and ''Anhanguera'', and therefore it is placed within either Anhangueridae or Ornithocheiridae, depending on the author. ''Caulkicephalus'' was also a large pterosaur, with wingspan estimates of around .

Postcrania

The vertebral column of ornithocheiromorphs was heavily pneumatized by an extensive system of air sacs, leaving prominent pneumatic foraminae. The neck of ornithocheiromorphs was typically relatively long and robust, being longer than the torso in some derived clades. The neural spines of ornithocheiromorph cervical vertebrae were generally tall and spikelike. In some genera such as ''Tropeognathus'' and ''Istiodactylus'', up to six dorsal vertebrae are fused into a notarium. In some genera such as ''Anhanguera'', four to seven sacral vertebrae are fused into a synsacrum. The tail is not well known in ornithocheiromorphs, however. ''Zhenyuanopterus'', which is known for having 13 caudal vertebrae, formed one of the longest tails of any pterodactyloid. ''Anhanguera'', another well-known genus, had a shorter tail, with broad caudal vertebrae that bore a "duplex" cross-section similar to ''Pteranodon''.

The pelvis of ornithocheiromorphs was of moderate size compared to the body as a whole, similar to other ornithocheiroids. The three pelvic bones were often fused, as seen in many species such as '' Anhanguera santanae'', the ilium was long and low, and its front and rear blades projected horizontally beyond the edges of the lower pelvic bones. Despite the structure length, the processes of these rod-like forms indicate that the hindlimb muscles attached to them were limited in strength. The pubic bone was fused with the broad ischium into an ischiopubic blade, resulting in a narrow build. Sometimes, the blades of both sides were fused, closing the pelvis from below and forming the pelvic canal. The front of the pubic bones was also articulated with a unique structure, resulting in a pair of prepubic bones within. This formed a cusp covering the rear belly, and was located between the pelvis and the belly ribs. The hip joint of ornithocheiromorphs was not perforated and allowed considerable mobility to the leg, and suggests that it was vertical, as therefore had a function in breathing, compensating the relative rigidity of the chest cavity.

Classification

Several studies show that ornithocheiromorphs were less derived than the toothless pteranodontids such as ''Pteranodon'', and based on the different evolutionary changes, they therefore need to be grouped in a different clade than ''Pteranodon'', though still within Pteranodontoidea. In 2003, David Unwin considered the family Istiodactylidae to group with the toothless Pteranodontidae, within the group Ornithocheiroidea, but Alexander Kellner however, grouped it with the toothed Anhangueridae instead, resulting in a more understandable change of evolution between the two toothed families.

Subgroups

Brian Andres and colleagues found the families Istiodactylidae, Ornithocheiridae, and Anhangueridae to form a group in 2014, which he called Lanceodontia. The clade includes most families of ornithocheiromorphs, however they excluded the poorly-known family Lonchodectidae from membership in this clade. In their analysis, they also included the family Boreopteridae within the clade Anhangueria, though placed in a more basal position, while also containing the genus ''Guidraco''. In 2018 however, Nicholas Longrich and colleagues found Boreopteridae outside Anhangueria as the sister taxon of the family Lonchodectidae, both groups placed as basal members of the Ornithocheiromorpha.

Within Lanceodontia, there is a more restrictive clade called Ornithocheirae, which has a more convoluted taxonomic history. It was named by Harry Seeley in 1870 as a family that contains ''Ornithocheirus'' and its relatives. The name was emended to Ornithocheiridae, to match the requirements of the ICZN Code that a family-ranked clade should end with an "-idae" suffix. Brian Andres (2010) in his review of pterosaur phylogeny, defined the name Ornithocheirae phylogenetically, as a node-based taxon consisting of the last common ancestor of '' Anhanguera'' and ''Ornithocheirus'' and all its descendants. Thus Ornithocheirae is defined to include two families, the Anhangueridae and the Ornithocheiridae, following the opinion of Alexander KellnerKellner, A. W. A., (2003): Pterosaur phylogeny and comments on the evolutionary history of the group. pp. 105-137. — ''in'' Buffetaut, E. & Mazin, J.-M., (eds.): ''Evolution and Palaeobiology of Pterosaurs''. Geological Society of London, Special Publications 217, London, 1-347 and Andres that these families should not be synonymized based on their original phylogenetical definitions.A preview that shows the cladogram without clade names
/ref> Subsequent studies in 2019 have found Ornithocheirae to be a more inclusive group containing both Anhangueria (see below) and Targaryendraconia.

Another constituent clade of Ornithocheiromorpha is Anhangueria. Anhangueria was named by paleontologists Taissa Rodrigues and Alexander Kellner in a review of ''Ornithocheirus'' species in 2013, they defined the clade as a branch-based taxon consisting of all pteranodontoids more closely related to '' Anhanguera blittersdorffi'' than to ''Istiodactylus latidens'' and '' Cimoliopterus cuvieri''. Anhangueria originally only contained the genera ''Brasileodactylus'', ''Camposipterus'', '' Cearadactylus'', ''Ludodactylus'' as well as the family Anhangueridae, however, recent analyses had recovered the family Hamipteridae within this clade as well. In 2014, paleontologist Brian Andres and colleagues assigned more groups and genera within this clade, this included ''Guidraco'', the subfamily Boreopterinae, and the clade Ornithocheirae, which was further divided into the families Anhangueridae and Ornithocheiridae. This topology was later followed by a few other studies.Longrich, N.R., Martill, D.M., and Andres, B. (2018)
"Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary."
''PLoS Biology'', 16(3): e2001663.

In 2019, Alexander Kellner and colleagues described the new ornithocheiromorph '' Mimodactylus'', and used their analysis to name a new clade, Istiodactyliformes. They defined this clade as the most inclusive clade containing ''Istiodactylus'' but not '' Anhanguera''. Under their analysis, this new clade included the family Istiodactylidae, Mimodactylidae, and the genus ''Hongshanopterus''. Andres and colleagues later named a clade Ornithocheiriformes and defined it in opposition to Istiodactyliformes. Its given definition was the most inclusive clade containing ''Anhanguera'', but not ''Istiodactylus''.

Some of these clades have been recovered by various authors since their definition. A table summarizing all of these clades is shown below.

Relationships

There are competing theories of ornithocheiromorph phylogeny (evolutionary relationships). Below is a cladogram showing the results of a phylogenetic analysis presented by Longrich ''et al.'' (2018). In the analysis, they placed the genus ''Hongshanopterus'' as a basal member.

In 2019, several new species of ornithocheiromorphs were found, and the former species ''Ornithocheirus wiedenrothi'' was renamed as '' Targaryendraco wiedenrothi''.Rodrigo V. Pêgas, Borja Holgado & Maria Eduarda C. Leal (2019) On ''Targaryendraco wiedenrothi'' gen. nov. (Pterodactyloidea, Pteranodontoidea, Lanceodontia) and recognition of a new cosmopolitan lineage of Cretaceous toothed pterodactyloids, Historical Biology,
The description of '' Iberodactylus'' in Spain also made some paleontologists reclassify the genus ''Hamipterus'' in a newly named family called Hamipteridae. The ornithocheirid ''Cimoliopterus'' was also reclassified as well, and it is currently grouped with '' Aetodactylus'' and ''Camposipterus'' in the clade Targaryendraconia, specifically to its own family, the Cimoliopteridae. However, an analysis by Jacobs ''et al.'' (2019) recovers both ''Camposipterus'' and ''Cimoliopterus'' within the Ornithocheiridae again, using a new data matrix not including ''Targaryendraco.'' The previously recovered basal eupterodactyloid '' Haopterus'' was reclassified due to the description of '' Mimodactylus'', and is placed in a new family called Mimodactylidae.Kellner, Alexander W. A.; Caldwell, Michael W.; Holgado, Borja; Vecchia, Fabio M. Dalla; Nohra, Roy; Sayão, Juliana M.; Currie, Philip J. (2019). "First complete pterosaur from the Afro-Arabian continent: insight into pterodactyloid diversity". ''Scientific Reports''. 9(1). . However, a more recent analysis using the data in the description of ''Mimodactylus'' has found ''Haopterus'' as a basal member of the more inclusive group Istiodactyliformes. Many recent analyses have also recovered several ornithocheirids, including ''Tropeognathus'', ''Coloborhynchus'', and ''Caulkicephalus'' within the family Anhangueridae, meaning that they were more closely related to ''Anhanguera'' than to ''Ornithocheirus''.Borja Holgado, Rodrigo V. Pêgas, José Ignacio Canudo, Josep Fortuny, Taissa Rodrigues, Julio Company & Alexander W.A. Kellner, 2019, "On a new crested pterodactyloid from the Early Cretaceous of the Iberian Peninsula and the radiation of the clade Anhangueria", ''Scientific Reports'' 9: 4940.

Later, in 2019, a different phylogenetic analysis, this time conducted by Borja Holgado and colleagues, focused on derived pterodactyloids with particular emphasis on anhanguerians. In this analysis, Anhangueria consisted of ''Camposipterus'' and the families Anhangueridae and Hamipteridae, the clade Ornithocheirae was recovered as a more inclusive group consisting of ''Ornithocheirus'' and ''Cimoliopterus'' as basal members, as well as the Anhangueria in the most derived position. This classification is supported by the expansion of the premaxillary tip (a spoon-like expansion at the end of the snout) with a high jaw end. Many analyses afterwards have followed this concept, although some had recovered ''Camposipterus'' outside the Anhangueria (within the clade Targaryendraconia), but still within the Ornithocheirae.

Below is cladogram following a topology recovered by Brian Andres, using the most recent iteration of his data set (Andres, 2021).Andres, B. (2021) Phylogenetic systematics of ''Quetzalcoatlus'' Lawson 1975 (Pterodactyloidea: Azhdarchoidea). ''Journal of Vertebrate Paleontology'', 41:sup1, 203-217. DOI: 10.1080/02724634.2020.1801703 https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1801703

In their description of ''Lingyuanopterus'' in 2022, Xu Yizhi and colleagues recovered the following phylogeny based on the earlier work of Borja Holgado and Rodrigo Pêgas.

Paleobiology

Diet and feeding

Ornithocheiromorphs were originally regarded as piscivorous creatures, feeding mainly on small and mid-sized fish. Some paleontologists even suggested details on how these pterosaurs caught fish, some of which included dipping their beaks close to the water for prey. Hooley for example, found that the beak of the well known ''Istiodactylus'' was similar to those of birds such as herons, storks, and skimmers, and suggested that ''Istiodactylus'' probably fed on fish, this was mainly based on his 1913 jaw reconstruction of the animal. In 1991, Peter Wellnhofer compared the jaw endings of ''Istiodactylus'' with those of a duck, but he then noticed that it wasn't a "duck-billed pterosaur" or anything similar, even though it was popularly called that way. An analysis by Witton in 2012 found that the teeth of ''Istiodactylus'' were unlike the recurved and enlarged teeth seen in the more derived ornithocheirids such as ''Ornithocheirus'', he instead pointed out that it was more "razor-edged" and better suited for carrion rather than fish.

Another ornithocheiromorph that possessed similar features to ''Istiodactylus'' is ''Liaoxipterus'', which is known from a skull with several unique traits, including numerous peg-like teeth. The shape of its teeth indicated that ''Liaoxipterus'' was a possible insectivore, though this conclusion isn't considered entirely accurate.

Anhanguerids like ''Tropeognathus'' and ''Coloborhynchus'' are considered to be fish-eaters, and had longer and sharper teeth compared to the more rounded teeth of ''Istiodactylus'', though this is still sometimes disputed. Another difference that can be seen in more primitive ornithocheiromorphs their eyes being proportionally smaller compared to the assumed predatory and more advanced anhanguerids, this again adds to the fact that the more primitive groups were most likely scavengers, and later got more successful within the food chain, leading the later, more advanced groups to be the dominant fish hunters during the early Late Cretaceous.

Locomotion and flight

Ornithocheiromorphs, like other pterosaurs, are considered to have been skilled fliers as well as swift at moving on the ground. Footprints from several species show that most pterosaurs did not sprawl their limbs to a large degree, as in modern reptiles, but rather held the limbs relatively erect when walking, like dinosaurs. While footprints are yet to be known, it is likely that ornithocheiromorphs also walked erect. Compared to other earlier pterosaurs such as rhamphorhynchids, ornithocheiromorphs had unusually uneven limb proportions, with the forelimbs resulting in a much longer scale compared to the hind limbs. Their close relatives, the pteranodontids, were also found with similar features, though they more likely flew like modern-day albatrosses rather than anything else. Paleontologists also suggest that they most likely spend long stretches of time sea fishing, traveling very long distances without flapping while at the same time flying close the surface of the water with exploited wind speed, and without the necessity of thermals. This would likely have required them to use unique modes of locomotion compared to other pterosaurs, this can already be seen in earlier evolutions such as ''Istiodactylus'' and ''Nurhachius'', with powerful musculature attachments and well-developed pectoral and upper arm bones.Zhou X., Pêgas R.V., Leal M.E.C. & Bonde N. 2019. ''Nurhachius luei'', a new istiodactylid pterosaur (Pterosauria, Pterodactyloidea) from the Early Cretaceous Jiufotang Formation of Chaoyang City, Liaoning Province (China) and comments on the Istiodactylidae". ''PeerJ'' 7:e7688. It is also possible that ornithocheiromorphs ran (but not walked) bipedally, or that they used a hopping gait. Many pterosaur researchers like Mike Habib have noted that the limb proportions of some ornithocheiromorphs such as ''Anhanguera'' are consistent with hopping, though the scavenging istiodactylids are probably still the best examples of pterosaurs with a more terrestrial setting.Habib, M. (2011).
Dinosaur Revolution: ''Anhanguera''.
''H2VP: Paleobiomechanics''. Weblog entry, September 20, 2011. Accessed September 28, 2011: http://h2vp.blogspot.com/2011/09/dinosaur-revolution-anhanguera.html

Paleoecology

Even though the ornithocheiromorphs were discovered worldwide, most of them were concentrated in specific places. One of which is the fossil site called Romualdo Formation, which contains an impressive amount of pterosaur fossils. It is a diverse Lagerstätte in the larger geologic group called the Santana Group (sometimes called the Santana Formation), which is located in the Araripe Basin of northeastern Brazil, and dates back around 111 and 108 million years ago, during the Albian stage of the Early Cretaceous. The formation includes many species of ''Anhanguera'', several fossil remains of basal ornithocheiromorphs, including ''Brasileodactylus'', ''Cearadactylus'' and '' Unwindia'', as well as the anhanguerids ''Tropeognathus'', ''Coloborhynchus'', ''Maaradactylus'', and '' Araripesaurus''. These pterosaur genera were just some of the many recovered from the site, which also include the thalassodromines ''Tupuxuara'' and ''Thalassodromeus'', as well as the tapejarid '' Tapejara''.

Some other creatures from the formation include the theropods ''Irritator'', ''Mirischia'' and ''Santanaraptor'', and the crocodylomorph ''Araripesuchus''. The formation also includes several turtle remains, with some specimens referring to ''Santanachelys'', '' Cearachelys'' and ''Araripemys''. A few fish remains were also found within the Romualdo Formation, some of which were referred to '' Brannerion'', ''Rhinobatos'', ''Rhacolepis'', ''Tharrhias'' and '' Tribodus''. The Santana Group also consists of another Lagerstätte called the Crato Formation, which is not as diverse as the Romualdo Formation, but its fossil remains are still considered important.Martill, D.M., Bechly, G. and Loveridge, R.F. (2007). ''The Crato fossil beds of Brazil: window into an ancient world.'' Cambridge University Press. , This fossil site underlies the Romualdo Formation, and dates back around 115 and 113 million years ago during the Aptian stage, meaning that its fossil content is of older age. Similarly, the Crato Formation also contained several species of pterosaurs, including the basal lanceodontians ''Ludodactylus'' and ''Brasileodactylus'', as well as the ornithocheirid '' Arthurdactylus''. Other pterosaur genera include the tapejarids ''Tupandactylus'' and '' Aymberedactylus'', as well as the chaoyangopterid '' Lacusovagus''. The formation also contains other creatures such as the enantiornithine '' Cratoavis'', the neosuchian '' Susisuchus'', and several species of fish, including '' Belonostomus'', '' Calamopleurus'', ''Cladocyclus'',''Cladocyclus''
at Fossilworks.org '' Dastilbe'' and ''Lepidotes''. These fish genera were suggested to be prey for the pterosaurs that lived in the formation, but fossil remains are limited, so the subject is still controversial.

Another important fossil site is the Wessex Formation in the Isle of Wight, near the coast of England, which dates back around 140 and 125 million years ago (Berriasian to Barremian stages). The formation doesn't contain many fossil remains of pterosaurs compared to the Romualdo Formation, but it is still a very important site. Fossil remains of the istiodactylid ''Istiodactylus'', the anhanguerid ''Caulkicephalus'', and the tapejarid '' Wightia'' were found. The formation is also known for several theropods, including the spinosaurid ''Baryonyx'', the tyrannosauroid ''Eotyrannus'', the dromaeosaurid ''Ornithodesmus'', the compsognathid '' Aristosuchus'' as well as the allosauroid ''Neovenator''. Different types of herbivorous dinosaurs like ''Iguanodon'', ''Polacanthus'', ''Ornithopsis'', ''Mantellisaurus'' and ''Hypsilophodon'' were also found within the fossil site. Some other animals from the formation include the neosuchian ''Bernissartia'', sea turtles such as ''Helochelydra'' and ''Brodiechelys'', the cartilaginous fish ''Hybodus'', ray-finned fishes such as ''Belonostomus'', ''Caturus'', ''Lepidotes'' and ''Scheenstia'', as well as the mammals '' Eobaatar'', '' Loxaulax'' and ''Yaverlestes''.

A few fossils reported from the Toolebuc Formation and Winton Formation are believed to be from some of the last ornithocheiromorphs, due to the age of the fossil remains, which dated back to the Albian and Cenomanian stages of the Cretaceous, and some are even believed to belong to the Turonian stage. The Toolebuc Formation includes several remains of ornithocheiromorphs which are now referred to the genera '' Aussiedraco'' and ''Mythunga''. The formation also includes several herbivorous dinosaurs such as the ornithopod ''Muttaburrasaurus'' and the ankylosaur ''Kunbarrasaurus''. Fossil remains of marine animals were also uncovered within the fossil site, and some specimens of which belong to the ichthyosaur ''Platypterygius'', the pliosaurid ''Kronosaurus'' and the elasmosaurid '' Eromangasaurus''. Turtle remains from turtles that were proposed to be prey for pterosaurs were also found within the Toolebuc Formation, this included the genera '' Bouliachelys'', '' Cratochelone'' and '' Notochelone''. The Winton Formation consisted on a more terrestrial environment, containing several sauropod dinosaurs like '' Austrosaurus'', '' Diamantinasaurus'', '' Savannasaurus'' and ''Wintonotitan'' as well as large carnivorous dinosaurs such as ''Australovenator'' and crocodylomorphs like ''Isisfordia''. The formation's only pterosaur is the derived genus ''Ferrodraco'', which is also considered as one of the last ornithocheiromorphs, and a close relative of ''Mythunga''.

See also

* Pterosaur size

References

Further reading

*
*

External links

*

{{Taxonbar, from=Q21008934

Valanginian first appearances
Turonian extinctions
Fossil taxa described in 2014
Pteranodontoidea