Utahdactylus
Encyclopedia
Utahdactylus was a genus
of extinct reptile from the Kimmeridgian
-Tithonian
-age Upper Jurassic Morrison Formation
of Utah
, USA. Based on
DM 002/CEUM 32588 (an incomplete skeleton described as including a fragment of the skull, a cervical
vertebra, three back vertebrae, and a caudal
vertebra, ribs, a scapula
coracoid, and limb bones), Czerkas and Mickelson (2002) identified it as a "rhamphorhynchoid" pterosaur
. Bennett (2007) however, concluded that it has no diagnostic features of the Pterosauria, and cannot be positively identified beyond being an indeterminate diapsid
.
is Utahdactylus kateae. The genus name is derived from Utah
and Greek daktylos, "finger". The specific name means "for Kate", referring to Kate Mickelson.
The holotype
consists of some disarticulated bone fragments preserved on several chalkstone blocks. It is housed in the Dinosaur Museum, run by Czerkas himself.
The specimen was first described as a pterosaur, with a long tail
and an estimated wingspan
of 1.20 meters (3.94 feet). The authors considered it to be a "rhamphorhynchoid", i.e. a basal pterosaur, due to its long tail and large but not elongate cervical vertebrae, but without the typical groove in its forelimb bones. It was regarded as a "rhamphorhynchoid" based on an unprepared specimen in the most recent review of Morrison pterosaurs.
In 2007, pterosaur specialist Chris Bennett published a redescription wherein he disagreed with Czerkas' and Mickelson's conclusions. He found several of the bone identifications and interpretations to be mistaken, such as the skull bone (interpreted here as just a bone fragment of unknown origin), elongate tail vertebra (the presumed elongated extensions were ribs), humerus (unknown), and the orientation of the bone described as a scapulacoracoid (the scapula and coracoid parts had been confused). He could not locate other bones seen as impressions, and found no evidence to suggest that the identifiable bones came from a pterosaur. In fact, he found the general quality of the bone texture to differ from that of pterosaur bones. He concluded by classifying it as Diapsida incertae sedis
, and a dubious name
, adding an exhortation not to name pterosaurs from material lacking unequivocal pterosaur characters.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of extinct reptile from the Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....
-Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
-age Upper Jurassic Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
of Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, USA. Based on
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
DM 002/CEUM 32588 (an incomplete skeleton described as including a fragment of the skull, a cervical
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
vertebra, three back vertebrae, and a caudal
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
vertebra, ribs, a scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
coracoid, and limb bones), Czerkas and Mickelson (2002) identified it as a "rhamphorhynchoid" pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
. Bennett (2007) however, concluded that it has no diagnostic features of the Pterosauria, and cannot be positively identified beyond being an indeterminate diapsid
Diapsid
Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...
.
History
The genus was named and described in 2002 by Stephen Czerkas and Debra Mickelson. The type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is Utahdactylus kateae. The genus name is derived from Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
and Greek daktylos, "finger". The specific name means "for Kate", referring to Kate Mickelson.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
consists of some disarticulated bone fragments preserved on several chalkstone blocks. It is housed in the Dinosaur Museum, run by Czerkas himself.
The specimen was first described as a pterosaur, with a long tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
and an estimated wingspan
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
of 1.20 meters (3.94 feet). The authors considered it to be a "rhamphorhynchoid", i.e. a basal pterosaur, due to its long tail and large but not elongate cervical vertebrae, but without the typical groove in its forelimb bones. It was regarded as a "rhamphorhynchoid" based on an unprepared specimen in the most recent review of Morrison pterosaurs.
In 2007, pterosaur specialist Chris Bennett published a redescription wherein he disagreed with Czerkas' and Mickelson's conclusions. He found several of the bone identifications and interpretations to be mistaken, such as the skull bone (interpreted here as just a bone fragment of unknown origin), elongate tail vertebra (the presumed elongated extensions were ribs), humerus (unknown), and the orientation of the bone described as a scapulacoracoid (the scapula and coracoid parts had been confused). He could not locate other bones seen as impressions, and found no evidence to suggest that the identifiable bones came from a pterosaur. In fact, he found the general quality of the bone texture to differ from that of pterosaur bones. He concluded by classifying it as Diapsida incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
, and a dubious name
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
, adding an exhortation not to name pterosaurs from material lacking unequivocal pterosaur characters.
External links
- Utahdactylus in The Pterosauria