Istiodactylid skulls: A) Istiodactylus latidens (NHMUK R3877) (B) Istiodactylus sinensis (NGMC 99-07-11) and (C) Nurhachius ignaciobritoi (IVPP V-13288)
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 period (Barremian to Aptian stage).[2]Arbour and Currie (2011) described Canadian Gwawinapterus beardi as a member of Istiodactylidae living in the late Cretaceous (upper Campanian stage);[3] 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.[2] Additional research suggested that the species was in fact a fish.[4] The earliest known species might be Archaeoistiodactylus linglongtaensis, from the Middle Jurassic of China;[5] however, it also has been suggested that the holotype specimen of this species might actually be a poorly preserved specimen of Darwinopterus.[6]Hongshanopterus, a supposed istiodactylid from China, has been reclassified as a non-istiodactylid member of Ornithocheiroidea of uncertain phylogenetic placement by Witton (2012).[2]
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 Istiodactylus.[7]
Classification
Restoration of an Istiodactylus in flight
Below is a cladogram showing the phylogenetic placement of this group within Pteranodontia from Andres and Myers (2013).[8]
The cladogram below is a topology recovered by Kellner et al. (2019). In the analyses, they recovered Istiodactylidae within the more inclusive group Istiodactyliformes, and assigned both Istiodactylus and Liaoxipterus to a new subfamily called Istiodactylinae, but kept Nurhachius as a basal member.[9]
Unlike most ornithocheiroids, istiodactylids bear physiologies suited to a terrestrial life and many of their fossils have been found in freshwater-deposits. Istiodactylids are considered to be pterosaurian equivalents to vultures: acting as the clean-up crew in their native locations. Whether or not istiodactylids could swim like most water-loving pterosaurs remains a mystery.
^Hone, David W. E., Fitch, Adam J., Ma, Feimin, and Xu, Xing. 2020. An unusual new genus of istiodactylid pterosaur from China based on a near complete specimen. Palaeontologia Electronica 23(1):a09. https://doi.org/10.26879/1015 palaeo-electronica.org/content/2020/2931-a-new-istiodactylid-pterosaur
^Arbour V.M.; Currie P.J. (2011). "An istiodactylid pterosaur from the Upper Cretaceous Nanaimo Group, Hornby Island, British Columbia, Canada". Canadian Journal of Earth Sciences. 48 (1): 63–69. Bibcode:2011CaJES..48...63S. doi:10.1139/E10-083.
^Vullo R.; Buffetaut E.; Everhart M.J. (2012). "Reappraisal of Gwawinapterus beardi from the Late Cretaceous of Canada: a saurodontid fish, not a pterosaur". Journal of Vertebrate Paleontology. 32 (5): 1198–1201. Bibcode:2012JVPal..32.1198V. doi:10.1080/02724634.2012.681078. S2CID129180570.
^Lü J.; Fucha X. (2010). "A new pterosaur (Pterosauria) from Middle Jurassic Tiaojishan Formation of western Liaoning, China". Global Geology. Z1: 113–118.
