Pterodactyloidea (/ˌtɛrəˈdæktl̩ɔɪdɪːə/; derived from the Greek words πτερόν (pterón, for usual ptéryx) "wing", and δάκτυλος (dáktylos) "finger") is one of the two traditional suborders of pterosaurs ("wing lizards"), and contains the most derived members of this group of flying reptiles. They appeared during the middle Jurassic Period, and differ from the basal (though paraphyletic) rhamphorhynchoids by their short tails and long wing metacarpals (hand bones). The most advanced forms also lack teeth, and by the late Cretaceous, all known pterodactyloids were toothless. Many species had well-developed crests on the skull, a form of display taken to extremes in giant-crested forms like Nyctosaurus and Tupandactylus. Pterodactyloids were the last surviving pterosaurs when the order became extinct at the end of the Cretaceous Period, together with the non-avian dinosaurs and most marine reptiles. "Pterodactyl" is also a common term for pterodactyloid pterosaurs, though it can also be used to refer to Pterodactylus specifically. Well-known examples of pterodactyloids include Pterodactylus, Pteranodon, and Quetzalcoatlus. In 2014, fossils from the Shishugou Formation of China were classified as the most basal pterodactyloid yet found, Kryptodrakon. At a minimum age of about 161 my, it is about 5 million years older than the oldest previously known confirmed specimens. Some later studies have found Kryptodrakon to be a non-pterodactyloid. Previously, a fossil jaw recovered from the Middle Jurassic (Bathonian) Stonesfield Slate formation was considered the oldest known, but further examination suggested it belonged to a teleosaurid instead of a pterosaur. In 2018 Michael O'Sullivan and David Martill described a partial synsacrum from the Stonesfield Slate identified as possibly pterodactyloid, though they noted it could also be a wukongopterid. If correctly identified, it would be the oldest pterodactyloid fossil known. In 2022 Martill and colleagues described a likely ctenochasmatid tooth, also from Stonesfield.
Classification Pterodactyloidea is traditionally considered to be the group of short-tailed pterosaurs with long wrists (metacarpus), compared with the relatively long tails and short wrist bones of basal pterosaurs ("rhamphorhynchoids"). In 2004, Kevin Padian formally defined Pterodactyloidea as an apomorphy-based clade containing those species possessing a metacarpal at least 80% of the length of the humerus, homologous with that of Pterodactylus. This definition was adopted by the PhyloCode in 2020.
Subgroups
A subgroup of pterodactyloids, called the Lophocratia, was named by David Unwin in 2003. Unwin defined the group as the most recent common ancestor of Pterodaustro guinazui and Quetzalcoatlus northropi, and all its descendants. This group was named for the presence of a head crest in most known species, though this feature has since been found in more primitive pterosaurs and was probably an ancestral feature for all pterodactyloids. Another subgroup within Lophocratia is Eupterodactyloidea (meaning "true Pterodactyloidea"). Eupterodactyloidea was named by S. Christopher Bennett in 1994 as an infraorder of the suborder Pterodactyloidea. Bennett defined it as an apomorphy-based clade. However, in 2010, Brian Andres re-defined the group as a stem-based taxon in his dissertation, and then formalized the definition in 2014 as all pterosaurs more closely related to Pteranodon longiceps than to Pterodactylus antiquus. The slightly more exclusive group Ornithocheiroidea was re-defined in 2003 by Alexander Kellner. He defined it as the least inclusive clade containing Anhanguera blittersdorffi, Pteranodon longiceps, Dsungaripterus weii, and Quetzalcoatlus northropi. Ornithocheiroidea has often been used for a much more exclusive group including only the branch of traditional ornithocheirid pterosaurs, though this use has since fallen out of favor by many researchers after years of competing definitions for the various pterodactyloid clades. The compromise definitions by Andres and others have since become more widely adopted. Within Eupterodactyloidea, there is a large clade - Ornithocheiroidea. The name Ornithocheiroidea was originally defined as an apomorphy-based taxon by Christopher Bennett in 1994. It was given a relationship-based definition in 2003 by Alexander Kellner, who defined it as the least inclusive clade containing Anhanguera blittersdorffi, Pteranodon longiceps, Dsungaripterus weii, and Quetzalcoatlus northropi. Later that year, David Unwin suggested a more restrictive definition, in which the clade only contains Pteranodon longiceps, Istiodactylus latidens, and their descentants. Brian Andres (2008, 2010, 2014) in his analyses, defined Ornithocheiroidea using the definition of Kellner (2003) to avoid confusion with similarly defined groups, like Pteranodontoidea. In 2019, a phylogenetic analysis conducted by Kellner and colleagues had recovered Ornithocheiroidea as the sister taxon of the Archaeopterodactyloidea, and consisting of the clades Tapejaroidea and Pteranodontoidea. Several recent studies have followed this or a similar concept.
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