The study of the phylogeny, or family tree, of pterosaurs is in its infancy. Various phylogenies have been presented, but all previous ones have ignored important transitional forms, such as Angustinaripterus (shown above), and the importance of beak shape in pterodactyloids. The following hypothesis was presented, in abbreviated form, as a platform session at the 1997 conference of the Society of Vertebrate Paleontology in Chicago. Otherwise this analysis has not been published or reviewed. 

Dimorphodontidae
Peteinosaurus, Dimorphodon, Sordes and Anurognathidae 

Maxilla does not extend ventral to the orbit; nasal breaks contact between ascending process of maxilla and lacrimal; cranial struts very thin; cervical ribs are tiny; sternal complex transversely wider than parasagittaly deep; subequal metacarpal lengths.

Sordes+Anurognathidae
Jaw articulation is posterior to the mandible and ventral to mid orbit; teeth recurved, reduced in number and homodont; caudal vertebrae gracile and/or greatly reduced; proximal phalanges reduced to disks on both manus and pes; terminal phalanx of pes digit V curved or bent.

Anurognathidae
Anurognathus, Batrachognathus, Nesodactylus, and Dendrorhynchoides

Rostrum and nares anteroposteriorly short; premaxilla essentially transverse; raised coronoid; pterygoid and palatine broad and pebbled with teeth; vomers short and narrow (these characters unknown in Nesodactylus); mandibles wide; first phalanx of wing finger subequal to metacarpal + carpal + antebrachium; fourth phalanx of wing finger reduced or absent.  A trend toward a longer, tighter metatarsus and shorter pedal phalanges is evident. 

Dorygnathoidea (all non-dimorphodontids)
Eudimorphodon, Campylognathoides and Ectadiopoda

Premaxilla-maxilla suture anterior to naris; maxilla extends ventral to orbit; maxilla contact with lacrimal maintained; tip of dentary toothless but surrounded by large teeth (reduced to absent in Dolichomyctera); deltopectoral crest subrectangular or distally displaced, pedal digit V terminal phalanx curved. 

Ectadiopoda
Rhamphorhynchus, Scaphognathinae and Dolichomyctera 

Ventral margin of naris rises relative to ventral margin of AOF; naris placement greater than a naris length from premaxilla tip; jaw articulation posterior; teeth reduced in number, longer and more widely spaced; medial shelves of maxilla are conjoined in Rhamphorhynchus and later taxa (reversed in Scaphognathinae); ventrally directed prepubes are typically perforated or anteriorly embayed (reversed in basal Pterodactyloidea); a distally displaced deltopectoral crest is extended anteriorly and narrow at the base; metatarsals I and II are the longest with IV the shortest and all without distal contact. 

Premaxilla is less than 20 percent of the jaw length; lacrimal approaches and contacts the external naris; quadratojugal spur extends dorsally on quadrate; the tail length is subequal to or shorter than the snout-vent length. 

Dolichomyctera
Parapsicephalus, Angustinaripterus and Pterodactyloidea 

Skull length to height ratio greater than 5:1 due to elongation of the maxilla; AOF larger than orbit (in Angustinaripterus); anterior teeth procumbent and rake-like in basal forms; lacrimal contacts external naris; nasal contacts orbit; maxilla no longer ventral to the orbit; postjugal spur absent. 

Undetermined basal Pterosauria: Rhamphinion, Herbstosaurus, Comodactylus

Pterodactyloidea
Cycnorhampidae and Bipalatia + Pteroactobatia

Naris confluent with antorbital fenestra; an inverted stalk-like medial nasal process descends into the nasoantorbital fenestra (NAOF); premaxilla and cranial crests are present, presumeably on males (reversed in Pteroactobatia); jugal-lacrimal suture weak (reversed in higher pterosaurs); maxilla contact with lacrimal and nasal broken; vomer-pterygoid contact broken; palatine process of pterygoid extends anteriorly and ventral to palatine (reversed in Pteroactobatia); dentary symphysis longer than a quarter of the mandible; fewer than 15 caudal vertebrae, each greatly reduced in size and all zyogpophyses and hemal arches absent; humerus not longer than the femur; metacarpal greater than 0.6 times the length of the antebrachium; pteroid elongate; second wing phalanx smaller than first; prepubes not perforated (reversed in Pteranodontidae); femur mostly curved (reversed in Brevimetacarpalia); metatarsal I (or I and II) the longest; pedal digit V greatly reduced.

Cycnorhamphidae
Cycnorhamphus and Diopecephalus

Dorsal profile of rostrum concave, large orbit larger than NAOF, elongation of the cervicals; retention of cervical ribs; elongation of metacarpals (convergent with Pteranodontidae and Azhdarchidae); deep embayment of the puboishiadic plate and shortening of the pubis; elongation of the tibia; metatarsal I the longest (unknown in Diopecephalus); plantigrade.

Bipalatia+ Pteroactobatia

Basipterygoids fused medially; cervical ribs reduced to nubs or transformed to postexapophyses in adults

Bipalatia
Brevimetacarpalia  and Scalmognatha

Striated grading to smooth premaxilla crest present, the palatine process of the pterygoid contacts the palatine process of the medial maxilla shelf ventral to the palatine which narrows to a strut; cervical centra have postexapophyses (convergent with Azhdarchidae); relatively short metacarpals retained in basal forms; more than five sacral vertebrae present. 

Brevimetacarpalia
"Ornithodsesmus," Ornithocheirus, Araripesaurus, Arthurdactylus, Brasileodactylus, Santanadactylus, Anhanguera, Criorhynchus = Tropeognathus

Parallel rami grading to spatulate jaw tips; palate ridge and dentary sulcus present; anterior teeth emphasized; cervical neural spines large; notarium present; postcranial ribs 9-11 (dorsals 1-3) very robust; sacral elements unfused until maturity attained; tail approximately 80 percent of the length of the femur with terminal element extensions; sternum broad and deep with rounded corners, smooth contours and deep robust keel; scapula shorter than coracoid and oriented essentially perpendicular to the spine; humerus larger than femur and equal to or greater than glenoid-acetabulum length; warped deltopectoral crest present with triangular aspect; radius smaller than half the diameter of the ulna; wing/torso ratio greater than 6.6; pubis separated from ischium by a large oval embayment ; femoral shaft almost straight; tibia long and gracile; pedal elements very small and gracile ó the smallest among pterosaurs; with digits longer than the metatarsals.

Scalmognatha
Germanodactylus rhamphastinus, Germanodactylus cristatus, Dsungaripteridae and Euscalmognatha

Premaxilla sharp with small to no teeth present; premaxillary crest present, often as a base for soft-tissue extensions; parietals and frontals forms a squared-off posterior cranial crest; ventral view of mandible is swordlike; basipterygoid is narrow and without ìYî prongs (unknown in basal axa; anterior teeth tiny to absent; atlas-axis fused; large cervical neural spines; six or more sacral vertebrae present; puboischiadic plate fused in subadults; middle phalanges of pedal digits III and IV are disc-like (convergent? with Pteroactobatia); sternum is shield-like grading to subrectangular as corners develop, metacarpals are elongate grading to hyper-elongate; the pedes are digitigrade with a metatarsus longer than or equal to the digits.

Dsungaripteridae+Euscalmognatha
"Phobetor," Dsungaripterus, Noripterus and Euscalmognatha

Medium to large pterosaurs with premaxilla and cranial crests prominent to huge; premaxilla and anterior dentary are toothless; premaxilla crest is smooth and probably pneumatic; the jugal-lacrimal suture is strong; paroccipital process distally expanded beyond the limits of the quadrate (reversed in Pteranodontidae); cervicals have large neural spines; notarium present; postcranial ribs 9 and 10 are hyper-robust; sternal complex with corners and crenulated lateral edges; keel not deep; gastralia fuse to the posterior edge of the sternal complex; scapula and coracoid subequal; metacarpal/ulna ratio greater than 0.9; radius/ulna ratio smaller than 0.8.

Euscalmognatha
Tapejaridae and Pteranodontidae

Edentulous; premaxilla crest extends nearly to tip of rostrum; descending nasal process reduced to a nub; nasal anterior process of palatine shifts contact from maxilla shelf to maxilla wall (unknown in Dsungaripteridae); no phalanges present on pedal digit V (unknown in Dsungaripteridae); wing/torso ratio greater than 6.6 (except in Tupuxuara); anterior process on posterior ilium.

Tapejaridae
Tupuxuara and Tapejara

The NAOF dominates the skull, extending anteriorly and rising above the level of the orbits (the latter convergent with Azhdarchidae); the premaxilla and parietal crests are large and elaborate, the posterior dentary is often very deep. 

Pteranodontidae
Pteranodon and Nyctosaurus

An extended low, sword-like rostrum and a reduced NAOF are present; skull length to height ratio (exclusive of crests) exceeds 7.0; terminal caudals shaped like needles; metacarpal/ulna ratio greater than 1.4; prepubes embayed and fused to produce conjoined medial belt and gastralia processes. 

Undetermined pterodactyloids Dermodactylus and Mesadactylus probably sister groups to Germanodactylus.

Pteroactobatia
Ctenochasmatodea and Tanydiroptera

Premaxilla crest absent (with two reversals); cranial crest absent; basiocciput strongly reclined; pterygoid is not ventral to palatine but remains posterior; medial pterygoid processes greatly reduced and gracile; teeth reduced (either shorter, thinner or absent); when a full arcade is present the anterior teeth are not emphasized, nevertheless the teeth tend to disappear from back to front in phylogeny; teeth restricted to pre- NAOF area; mid-cervical length to width ratio greater than 2.5; tail shorter than ilium; shield-like sternum grading to transversely narrow.

Ctenochasmatoidea
Pterodactylus kochi and Ctenochasmatidae

Extended rostrum; concave rostral profile (Gnathosaurus, the apparent exception, is a dorso-ventrally crushed specimen); very low skull; occiput horizontally opposed to the jawline; manual unguals reduced to no deeper than penultimate phalanx

Ctenochasmatidae
Ctenochasma, Gnathosaurus, Pterodaustro and Plataleorhynchus

Skull length to height ratio greater than 6.5; a full arcade of teeth inserted obliquely to laterally; dentition grading to more numerous and finer teeth; rostrum flattened; clawed manual digits shortened or reduced to disks.

Tanydiroptera
Pterodactylus antiquus, Huanhepterus and Azhdarchidae 

mall to gigantic pterodactyloids with a relatively tall skull (compared to ctenochasmatids) with a straight rostral profile; frontal extends to anterior orbit; teeth reduced; an elongate dentary keel (unknown in Huanhepterus); cervical/torso ratio more than 1; greatly elongate (= narrow) mid-cervicals (up to five times longer than wide), with greatly reduced to absent cervical spines; only eight pairs of dorsal ribs present; torso reduced; humerus robust with a wide deltopectoral crest; anterior process appears on posterior ilium process (convergent with Scalmognatha); sternum longer than wide with a trend toward further narrowing; a trend to reduced wing length, especially phalanx four; a trend to metatarsals grading to subequal (last three not in P. antiquus).

Azhdarchidae
Quetzalcoatlus, Zhejiangopterus,Azhdarcho, Arambourgiana

Greatly elongate edentulous jaws with parallel rami; frontals extend well anterior to lacrimal-jugal bar and anterior to nasal; very small orbit located below two-thirds the maximum height of the NAOF [unknown in Huanhepterus] (Unwin and Junchan 1996); reduced nasals posterior to NAOF; jugal-lacrimal contact strong; quadrate short and stout; enlarged dentary keel; cervical five is by far the longest; torso reduced; notarium present although the articulation seems to be oblique, rather than perpendicular to the spine; sternum narrow; brachial flange occupies more than half the shaft length of the coracoid (Unwin and Junchang 1996); metacarpus/antebrachium ratio greater than 1.0; longitudinal ridge on the ventral surface of wing phalanges 2 and 3 resulting in T-shaped cross-section (Nessov 1991); fourth phalanx of wing digit reduced to less than half that of the penultimate phalanx; femur longer than humerus; metatarsals I-IV subequal. 

Pronunciation Guide and Etymology