''Radiodactylus'' (meaning "radio finger") is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of non-

azhdarchid Azhdarchidae (from the Persian word , , a dragon-like creature in Persian mythology) is a family of pterosaurs known primarily from the Late Cretaceous Period, though an isolated vertebra apparently from an azhdarchid is known from the Early Cre ...

azhdarchoid Azhdarchoidea (or azhdarchoids) is a group of pterosaurs within the suborder Pterodactyloidea, more specifically within the group Ornithocheiroidea. Pterosaurs belonging to this group lived throughout the Early Cretaceous, Early and Late Cretaceo ...

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...

known from the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

period of what is now

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

, southern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

. It contains a single species, ''Radiodactylus langstoni''.

Discovery

''Radiodactylus'' is known solely from its

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

SMU Educational institutions * St. Martin's University, Lacey, Washington, United States * St. Matthew's University, the Cayman Islands * St. Michaels University School, Victoria, British Columbia, Canada * Saint Monica University, Cameroon * Samuel ...

72547, a nearly complete left

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

first described by Phillip Murry ''et al.'' (1991).Murry, P.A., Winkler, D.A. & Jacobs, L.L., 1991, "An azhdarchid pterosaur humerus from the Lower Cretaceous Glen Rose Formation of Texas", ''Journal of Paleontology'' 65(1): 167–170 The specimen is well preserved in three dimensions with no apparent crushing. The humerus lacks only portions of the proximal end and anterior end of the deltopectoral crest, and has a fracture in the mid-shaft area where it is very slightly rotationally distorted. ''Radiodactylus'' was first named by Brian Andres and Timothy S. Myers in

2013 File:2013 Events Collage V2.png, From left, clockwise: Edward Snowden becomes internationally famous for leaking classified NSA wiretapping information; Typhoon Haiyan kills over 6,000 in the Philippines and Southeast Asia; The Dhaka garment ...

and the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

is ''Radiodactylus langstoni''. The generic name is derived from ''radio'', the prefix for radioactivity in reference to the

Comanche Peak Nuclear Power Plant Comanche Peak Nuclear Power Plant is located in Somervell County, Texas. The nuclear power plant is located southwest of Ft. Worth and about southwest of Dallas. It relies on nearby Squaw Creek Reservoir for cooling water. The plant has about ...

, where SMU 72547 was discovered during the construction of an emergency

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure t ...

, and ''dactylos'', meaning "finger" in

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

which is a traditional suffix for

genera in reference to their elongate wing digits. The specific name, ''langstoni'', honors the late Dr.

Wann Langston Jr. Wann Langston Jr. (1921 – April 7, 2013) was an American paleontologist and professor at the University of Texas at Austin. Langston worked on a number of different reptiles and amphibians in his long career, beginning with the 1950 description ...

who has been described by Andres and Myers (2013) as "the father of Texas

ology". The holotype was collected from the

Glen Rose Formation The Glen Rose Formation is a shallow marine to shoreline geological formation from the lower Cretaceous period exposed over a large area from South Central to North Central Texas. The formation is most widely known for the dinosaur footprints ...

at the north side of Squaw Creek in Somervell County, dating to the upper

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

or lower

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± ...

stage of the late

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

, about 119-112

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

Description

Andres and Myers (2013) diagnosed ''Radiodactylus'' on the basis of the unique combination of tall rectangular deltopectoral crest positioned proximally and pneumatic

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

present on distal portion of the humerus. This large-sized pterosaur also has autapomorphic square distal humerus cross section, and a straight vertical groove on distal aspect of the humerus without ulnar tubercle. The holotype of ''Radiodactylus'' was originally referred to

Azhdarchidae Azhdarchidae (from the Persian word , , a dragon-like creature in Persian mythology) is a family of pterosaurs known primarily from the Late Cretaceous Period, though an isolated vertebra apparently from an azhdarchid is known from the Early Cre ...

by Murry ''et al.'' (1991) based on shared characters that were considered to possibly represent

plesiomorphies In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

. According to Andres and Myers (2013), ''Radiodactylus'' shares a tall rectangular deltopectoral crest and a massive, ventrally-oriented ulnar crest with

s, and a pneumatic foramen on the distal end with the

s (also seen in most pteranodontoids). The humerus clearly lacks many traits that are present in other pterosaur clades, like

Pteranodontia Pteranodontia is an extinct group of ornithocheiroid pterodactyloid pterosaurs that lived during the Late Cretaceous period (Coniacian to Maastrichtian stages) of North America and Africa. They were some of the most advanced pterosaurs, and poss ...

and

Tapejaridae Tapejaridae (from a Tupi word meaning "the old being") are a family of pterodactyloid pterosaurs from the Cretaceous period. Members are currently known from Brazil, England, Hungary, Morocco, Spain, the United States, and China. The most prim ...

. The presence of a distal pneumatic foramen, in addition to the lack of a distally positioned deltopectoral crest on the humerus, supports a

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

relation to Azhdarchidae. The absence of a deep

horseshoe-shaped Many shapes have metaphorical names, i.e., their names are metaphors: these shapes are named after a most common object that has it. For example, "U-shape" is a shape that resembles the letter U, a bell-shaped curve has the shape of the vertica ...

cross section of the humeral head and a distinct supracondylar process on the humerus shaft differentiated ''Radiodactylus'' from members of the Azhdarchidae.

Phylogeny

Although described as an

by Murry ''et al.'' (1991) and recovered as the

of the clade containing all other azhdarchids by the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis performed by Andres and Myers (2013), it was classified as a non-azhdarchid

neoazhdarchia Azhdarchoidea (or azhdarchoids) is a group of pterosaurs within the suborder Pterodactyloidea, more specifically within the group Ornithocheiroidea. Pterosaurs belonging to this group lived throughout the Early and Late Cretaceous periods, with ...

n. Though closely related to the Azhdarchidae, ''Radiodactylus'' is relatively small and much older compared to true azhdarchids. Furthermore, the phylogenetic definitions of the Azhdarchidae by

Alexander Kellner Alexander Wilhelm Armin Kellner (born September 26, 1961) is a Brazilian geologist and paleontologist who is a leading expert in the field of studying pterosaurs. His research has focused mainly on fossil reptiles from the Cretaceous Period, i ...

and

David Unwin David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". w ...

, both conducted in 2003, exclude this species from Azhdarchidae. This sister taxon relationship supported by the largest and most inclusive pterosaur phylogenetic analysis to date warranted the erection of a new genus and species for this material. The

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

below shows a phylogenetic analysis conducted by Nicholas Longrich and colleagues in 2018. They recovered ''Radiodactylus'' as a basal member of the clade

Neopterodactyloidea Azhdarchoidea (or azhdarchoids) is a group of pterosaurs within the suborder Pterodactyloidea, more specifically within the group Ornithocheiroidea. Pterosaurs belonging to this group lived throughout the Early and Late Cretaceous periods, with ...

References

{{Portal bar, Paleontology, Cretaceous, United States Azhdarchoids Early Cretaceous pterosaurs of North America Fossil taxa described in 2013 Early Cretaceous reptiles of North America Paleontology in Texas

Discovery

Description

Phylogeny

See also

References