Istiodactylidae is a small

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

s. This family was named in 2001 after the type genus ''

Istiodactylus ''Istiodactylus'' is a genus of pterosaur that lived during the Early Cretaceous period, about 120 million years ago. The first fossil was discovered on the English Isle of Wight in 1887, and in 1901 became the holotype specimen of a new species ...

'' was discovered not to be a member of the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

'' Ornithodesmus''.

Systematics and distribution

Remains of taxa that can be confidently assigned to Istiodactylidae have been found in the UK and China, in rocks dating from the Early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period (

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

stage).

Arbour Arbor(s) or Arbour(s) may refer to: Arts and entertainment * Arbor (installation), ''Arbor'' (installation), a 2013 public artwork in Indianapolis, Indiana, US * Arbor, a counterweight-carrying device found in theater fly system#Arbors, fly syste ...

and Currie (2011) described Canadian ''

Gwawinapterus ''Gwawinapterus beardi'' is a species of saurodontid ray-finned fish from the Late Cretaceous period of British Columbia, Canada. While initially described as a very late-surviving member of the pterosaur family Istiodactylidae, further examinat ...

beardi'' as a member of Istiodactylidae living in the late Cretaceous (upper

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

stage); however, Witton (2012) suggested the tooth replacement pattern in this animal does not match that of pterosaurs, suggesting that the species might be non-pterosaurian. Additional research suggested that the species was in fact a fish. The earliest known species might be ''

Archaeoistiodactylus linglongtaensis ''Archaeoistiodactylus'' is an extinct genus of wukongopterid pterosaur from the Middle Jurassic of China. Discovery and naming ''Archaeoistiodactylus'' is known from an incomplete skeleton with a partial skull and lower jaws. Catalogued as holo ...

'', from the

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

of China; however, it also has been suggested that the holotype specimen of this species might actually be a poorly preserved specimen of ''

Darwinopterus ''Darwinopterus'' (meaning "Darwin's wing") is a genus of pterosaur, discovered in China and named after biologist Charles Darwin. Between 30 and 40 fossil specimens have been identified, all collected from the Tiaojishan Formation, which dates t ...

''. ''

Hongshanopterus ''Hongshanopterus'' is a genus of pterodactyloid pterosaur from the Lower Cretaceous Jiufotang Formation of Liaoning, China. The type species ''Hongshanopterus lacustris'' was in 2008 named and described by Wang Xiaolin, Diogenes de Almeida C ...

'', a supposed istiodactylid from China, has been reclassified as a non-istiodactylid member of Ornithocheiroidea of uncertain phylogenetic placement by Witton (2012). Istiodactylids were medium-sized pterosaurs with flat, rounded jaws similar to that of a duck. They had small teeth lining their jaws, however, and this can mostly be seen in the more advanced genera such as ''

''.

Classification

Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

showing the phylogenetic placement of this group within Pteranodontia from Andres and Myers (2013). The cladogram below is a topology recovered by Kellner ''et al.'' (2019). In the analyses, they recovered Istiodactylidae within the more inclusive group

Istiodactyliformes 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 Cretaceous, Early to Late Cretaceous Period (geology), period ...

, and assigned both ''Istiodactylus'' and ''Liaoxipterus'' to a new subfamily called Istiodactylinae, but kept ''Nurhachius'' as a basal member.

Paleobiology

Lifestyle

Unlike most ornithocheiroids, istiodactylids bear morphologies suited to a terrestrial life and many of their fossils have been found in freshwater-deposits. Istiodactylids are considered to be pterosaurian equivalents to

vulture A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to Nort ...

s: acting as the clean-up crew in their habitats. The swimming abilities of Istiodactylids have not been analyzed, in contrast to Ornithocheirids.

References

{{Taxonbar, from=Q522434 Pteranodontoidea Early Cretaceous first appearances Early Cretaceous genus extinctions Pterosaur families