Anhangueridae
Anhangueridae is a group of pterosaurs within the suborder Pterodactyloidea. These pterosaurs were among the last to possess teeth. Members that belong to this group lived from the Early to Late Cretaceous periods, around 140 to 90 million years ago.
Anhanguerids are generally infamous for having an enormously controversial and very confusing taxonomy. Although agreements that these animals were related, and therefore similar to istiodactylids and pteranodontians, there is still no virtual consensus over the exact content and interrelationships of this group. Anhanguerids were the most successful pterosaurs during their reign, and were also the largest pterosaurs before the appearance of the azhdarchids such as Quetzalcoatlus. Anhanguerids were excellent fish hunters, using various flight techniques to catch their prey, and were also capable of flying great distances without flapping constantly.
History
Naming
The family Anhangueridae is without a doubt, one of the most well-known pterosaur groups, mostly due to their very controversial and convoluted taxonomic history. Most of the anhanguerid fossil record consists of isolated teeth, as well as fragmentary bones, reaching hundreds or even thousands of remains in some localities. The first uncovered anhangueridsid remains were described in 1861 by British paleontologist Sir Richard Owen, who assigned the fossil remains to a new species of Pterodactylus: P. simus. In 1869, British paleontologist Harry Govier Seeley erected the new generic name Ornithocheirus, and assigned P. simus as its type species, therefore creating Ornithocheirus simus. Later, in 1870, Seeley created the name Ornithocheirae to only contain Ornithocheirus. Today, this was emended to "Ornithocheiridae Seeley 1870" following the article 11.7.1.3 of the ICZN, retaining the authorship and date of the original "Ornithocheirae Seeley 1870".In 1874, Owen had proposed two new genera for the Cretaceous British pterosaurs: Coloborhynchus and Criorhynchus based on highly distinctive jaw fragments. Owen reassigned P. simus as the type species of Criorhynchus, creating Criorhynchus simus. He referred three species to Coloborhynchus, including the addition of a new species called C. clavirostris; no type species was designated, however. In 1876, however, Seeley pointed out that Criorhynchus was a junior synonym of Ornithocheirus, a concept that was followed by paleontologist Richard Lydekker in 1888. In the latter year, Lydekker acknowledged that Ornithocheirus simus was the type species of Ornithocheirus, and also distinguished O. simus by its tall rostrum, while other species referred to Ornithocheirus had lanceolate jaw tips. Therefore, to avoid confusion, Lydekker preferred to use the name Criorhynchus for O. simus, and Ornithocheirus for the species with lanceolate jaw tips, a concept later favored by paleontologist Reginald Walter Hooley in 1914. In his review of Ornithocheirus, he divided the family Ornithocheiridae into two subfamilies: Ornithocheirinae and Criorhynchinae; the former consisted of Ornithocheirus and Lonchodectes, while the latter consisted of Amblydectes and Criorhynchus. In his review, Hooley also considered the species Coloborhynchus clavirostris as a synonym of Criorhynchus simus. In 1967, paleontologist Oskar Kuhn placed Criorhynchus within the family Criorhynchidae, and recognized Ornithocheirus within the family Ornithocheiridae and subfamily Ornithocheirinae. He also designated the species Coloborhynchus clavirostris as the type species of Coloborhynchus, but agreed with Hooley that it was synonymous with Criorhynchus simus. In 1994, however, Yuong-Nam Lee revalidated the genus Coloborhynchus, and regarded it as distinct from Criorhynchus simus. Later, in 2001, paleontologist David Unwin revised the taxonomic history of the Cambridge Greensand pterosaurs, and divided Ornithocheiridae into three genera: Ornithocheirus, Coloborhynchus and Anhanguera. Unwin also designated Ornithocheirus simus as the type and only species of Ornithocheirus.
In 2003, Unwin defined the family Ornithocheiridae as Haopterus gracilis, Ornithocheirus simus, their most recent common ancestor, and all its descendants. He included the genera Anhanguera, Brasileodactylus, Coloborhynchus, Haopterus, Ludodactylus and Ornithocheirus within the family, and also concluded that Araripesaurus, Arthurdactylus and Santanadactylus may belong to this family as well. However, their taxonomic status and precise relationships with other ornithocheirids are uncertain. In 2019, upon the description of the pterosaur Mimodactylus, Haopterus, which was assigned to this family by Unwin, and recovered as a basal eupterodactyloid by Brian Andres and colleagues, was reassigned by Alexander Kellner and colleagues as the sister taxon of the former.
In 2014, Andres and colleagues defined the Ornithocheiridae with a different definition: the most inclusive clade containing Ornithocheirus simus but not Anhanguera blittersdorffi. They placed the genera Coloborhynchus, Ornithocheirus and Tropeognathus within the Ornithocheiridae, while placing Anhanguera within the separate family Anhangueridae. However, back in 2001, Unwin considered the name Anhangueridae a junior synonym of Ornithocheiridae, a concept that was later followed by several paleontologists such as Mark Witton in 2013. Some phylogenetic analyses, however, contradict this name synonymy, with Ornithocheiridae and Anhangueridae classified as different families, therefore following the 2014 analysis by Andres and colleagues instead. Many modern sudies such as the ones by Kellner and colleagues in 2019 have used a different concept, classifying Coloborhynchus, Tropeognathus, as well as several other close relatives such as Ludodactylus and Caulkicephalus within the Anhangueridae, which, along with the family Hamipteridae, forms the larger group Anhangueria. They assigned Ornithocheirus outside the Anhangueria due to being undiagnosable. Most recent studies have since followed this concept.
Description
Among toothed pterodactyloids, anhanguerids were the largest; they were also among the most successful and widely distributed pterosaurs. Anhanguerids were characterized by long jaws with spike-like teeth. Anhanguerid wingspans varied in size, with smaller species having wingspans of approximately, while giant morphs reached wingspans of up to or more. Specimen NHMUK R481, a specimen that belongs to the species Coloborhynchus capito, the largest toothed pterosaur, had a wingspan that may have reached. However, in 2013, a specimen referred to the genus Tropeognathus, was calculated to have had a normal wingspan of, with another calculated maximum wingspan reached, indicating that the wingspans of toothed pterosaurs could exceed.Skull
Anhanguerids had elongated jaws with rounded sagittal crests on both tips, as well as robust fang-like teeth. The sagittal crest of the species Ornithocheirus simus and Tropeognathus mesembrinus extended to the anterior end of the rostrum, a feature that is also seen in the anhanguerid species Siroccopteryx moroccensis; further synapomorphies between these three species were also found, including the premaxilla having a tall and narrow shape in anterior aspect, the anterolateral margins of the premaxilla being convex in both anterior and lateral view, a feature that resulted in a bluntly rounded outline of the tip of the rostrum. The rostrum in S. moroccensis lacks a constriction that is posterior to the anterior rosette, a feature also shared by O. simus and T. mesembrinus, therefore another synapomorphy supported by these three species. Yet another feature shared by these three species is that the teeth are short, straight, and relatively uniform in size, something that is not present in other ornithocheirans such as Coloborhynchus and Anhanguera. In Coloborhynchus, the teeth were found to have been heterodont, elongated, recurved and caniniform, which is similar to those seen in another anhanguerid called Caulkicephalus. The genus Caulkicephalus, though having similarities with other anhanguerids, including the anterior end of the rostrum being transversely expanded, or having a low, bony sagittal crest that includes a smooth dorsal margin on the rostrum, still possesses some unique features. The most distinct characteristic of Caulkicephalus is that it bores a frontoparietal crest, a feature that is only seen in pteranodontians such as Pteranodon, and in Ludodactylus, a pterosaur once assigned to the Ornithocheiridae, but some recent analysis have placed it within the more inclusive group Anhangueria. Other studies, however, have recovered it within the Anhangueridae instead.Postcranial skeleton
The forelimbs of anhanguerids were proportionally enormous, around five times longer than their legs. Substantial anchorage on the body is required given the mighty arms, and accordingly, anhanguerids have robust scapulocoracoids, and stout, deeply keeled sterna, which served the purpose of housing their substantial forelimb muscles. The shoulder or pectoral girdle in anhanguerids is set at a perpendicular angle to the spine, with the coracoids being much longer than the scapulae. The shoulder girdle is also of typical construction for ornithocheiroids. Over 60 percent of the wing length is occupied by the wing fingers, making them among the longest possessed by any pterodactyloids.In adult anhanguerids, the sacrum develops a supraneural plate above its neural spines. The tails of anhanguerids are poorly known, though they appear to be composed of at least eleven short vertebrae, and become relatively circular in cross section toward the end of the series. Like the related istiodactylids, the slender femora of anhanguerids have femoral heads that project almost in line with the femoral shaft, but seem to lack prominent processes that anchor their hindlimb muscles. Anhanguerids shinbones are similarly developed and of equal length to the femora. Although the feet in anhanguerids are poorly known, they seem to be relatively small and gracile, with undeveloped claws and a hook-like fifth metatarsal.