Aetodactylus
Encyclopedia
Aetodactylus is a genus
of ornithocheirid
pterodactyloid
pterosaur
. It is known from a lower jaw discovered in Upper Cretaceous rocks of northeastern Texas
, United States
. Aetodactylus is only the second ornithocheirid genus to be discovered in North America.
SMU 76383 (Shuler Museum of Paleontology, Southern Methodist University
), a nearly complete lower jaw lacking the right retroarticular process (the bony prong posterior
to the jaw joint), part of the posterior end of the mandibular symphysis (where the two halves of the lower jaw meet), and all but two teeth. This specimen was found in 2006 by Lance Hall near a construction site in Mansfield
, near Joe Pool Lake
(recorded as SMU Loc. 424). The rock it was found in is a calcareous
marine sandstone
rich in mud–sized particles, from the middle Cenomanian
-age (approximately 97 million years old) Tarrant Formation
. Also found were fish teeth and vertebrae, and indeterminate bones. The Tarrant Formation is the lowest rock unit of the Cenomanian–Turonian
–age Eagle Ford Group.
Aetodactylus was named by Timothy S. Myers of SMU in 2010
. The type species
is A. halli, named in honor of the discoverer. Aetodactylus is differentiated from other ornithocheirids by several anatomical details of the lower jaw, including the slight expansion of the anterior end of the lower jaw, the strong vertical compression of the symphysis, the relatively constant spacing of the teeth, and the slight upward curve of the lower jaw. Myers found that Aetodactylus compared best with the Chinese genus Boreopterus
. Aetodactylus represents one of the youngest definitive records of ornithocheirids.
The jaw SMU 76383 is 38.4 centimetres (15.1 in) long, 15.8 centimetres (6.2 in) (~41%) of which is joined left and right jaws. 27 pairs of teeth were present; the two remaining teeth are pointed, curved slightly backward, flattened from side to side, and slender. The tip of the jaw is slightly expanded (to 1.6 centimetre (0.62992125984252 in) from a minimum of 1.3 centimetre (0.511811023622047 in) just posterior) and contains the first four pairs of teeth, with the first pair projecting forward. Based on the size of the tooth sockets, the teeth of the second and third pairs were largest, with tooth size decreasing posteriorly. There are small pits between the posterior teeth, interpreted as points where the teeth of the upper jaw rested against the lower jaw. These pits disappear partway along the tooth row, suggesting that the anterior teeth of the upper jaws were longer and projected outwards to a degree. Unlike some other ornithocheirids, such as Anhanguera
, Coloborhynchus
, and Ornithocheirus
, there is no bony crest on the lower jaw.
It is possible that Aetodactylus might be a boreopterid
, as Myers identifies it as being closely related to Boreopterus
, and many ornithocheirid remains might belong to boreopterids instead.
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 ornithocheirid
Ornithocheiridae
Ornithocheiridae is a group of pterosaurs within the suborder Pterodactyloidea. They were among the last pterosaurs to possess teeth.-Classification:Listing of genera after Unwin , except where noted.* Family Ornithocheiridae** ?Aetodactylus...
pterodactyloid
Pterodactyloidea
Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...
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...
. It is known from a lower jaw discovered in Upper Cretaceous rocks of northeastern Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Aetodactylus is only the second ornithocheirid genus to be discovered in North America.
Description
Aetodactylus is based onHolotype
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...
SMU 76383 (Shuler Museum of Paleontology, Southern Methodist University
Southern Methodist University
Southern Methodist University is a private university in Dallas, Texas, United States. Founded in 1911 by the Methodist Episcopal Church, South, SMU operates campuses in Dallas, Plano, and Taos, New Mexico. SMU is owned by the South Central Jurisdiction of the United Methodist Church...
), a nearly complete lower jaw lacking the right retroarticular process (the bony prong posterior
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
to the jaw joint), part of the posterior end of the mandibular symphysis (where the two halves of the lower jaw meet), and all but two teeth. This specimen was found in 2006 by Lance Hall near a construction site in Mansfield
Mansfield, Texas
Mansfield is a city in Ellis, Johnson, and Tarrant counties in the U.S. state of Texas. As of the 2010 census, the population was 56,368.In 2009, CNN/Money Magazine rated Mansfield as one of the "Best Places to Live" in the United States, ranking 24th out of the top 100 places.-History:The first...
, near Joe Pool Lake
Joe Pool Lake
Joe Pool Lake is a fresh water impoundment located in the southern part of the Dallas/Fort Worth Metroplex in North Texas . The lake encompasses parts of Tarrant, Dallas and Ellis counties. The lake measures with a conservation storage capacity of...
(recorded as SMU Loc. 424). The rock it was found in is a calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
marine sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
rich in mud–sized particles, from the middle Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
-age (approximately 97 million years old) Tarrant Formation
Tarrant Formation
The Tarrant Formation is a geologic formation that dates to the Middle Cenomanian stage of the Late Cretaceous....
. Also found were fish teeth and vertebrae, and indeterminate bones. The Tarrant Formation is the lowest rock unit of the Cenomanian–Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
–age Eagle Ford Group.
Aetodactylus was named by Timothy S. Myers of SMU in 2010
2010 in paleontology
-Anomalocaridids:-Newly named crustaceans:-Newly named insects:* A new family, Cascopleciidae, is published by Poinar Jr.* A new family of ceraphronoid Hymenopters, Radiophronidae, is published by Ortega-Blanco, Rasnitsyn, and Delclòs....
. The type species
Type 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 A. halli, named in honor of the discoverer. Aetodactylus is differentiated from other ornithocheirids by several anatomical details of the lower jaw, including the slight expansion of the anterior end of the lower jaw, the strong vertical compression of the symphysis, the relatively constant spacing of the teeth, and the slight upward curve of the lower jaw. Myers found that Aetodactylus compared best with the Chinese genus Boreopterus
Boreopterus
Boreopterus is a genus of ornithocheirid pterodactyloid pterosaur from the Barremian-Aptian-age Lower Cretaceous Yixian Formation of Dalian, Liaoning, China....
. Aetodactylus represents one of the youngest definitive records of ornithocheirids.
The jaw SMU 76383 is 38.4 centimetres (15.1 in) long, 15.8 centimetres (6.2 in) (~41%) of which is joined left and right jaws. 27 pairs of teeth were present; the two remaining teeth are pointed, curved slightly backward, flattened from side to side, and slender. The tip of the jaw is slightly expanded (to 1.6 centimetre (0.62992125984252 in) from a minimum of 1.3 centimetre (0.511811023622047 in) just posterior) and contains the first four pairs of teeth, with the first pair projecting forward. Based on the size of the tooth sockets, the teeth of the second and third pairs were largest, with tooth size decreasing posteriorly. There are small pits between the posterior teeth, interpreted as points where the teeth of the upper jaw rested against the lower jaw. These pits disappear partway along the tooth row, suggesting that the anterior teeth of the upper jaws were longer and projected outwards to a degree. Unlike some other ornithocheirids, such as Anhanguera
Anhanguera (pterosaur)
Anhanguera is a genus of pterodactyloid pterosaur known from the Lower-Cretaceous Santana Formation of Brazil, with referred specimens found in the Upper Chalk Formation and Cambridge Greensand of the UK...
, Coloborhynchus
Coloborhynchus
Coloborhynchus is a genus in the pterosaur family Ornithocheiridae, and is known from the Lower Cretaceous of England , and possibly the Aptian age of Brazil and Texas, depending on which species are included.-Description:The type specimen of Coloborhynchus is known only from a partial upper jaw...
, and Ornithocheirus
Ornithocheirus
Ornithocheirus was a pterosaur from the Cretaceous period of Europe and South America...
, there is no bony crest on the lower jaw.
It is possible that Aetodactylus might be a boreopterid
Boreopteridae
Boreopteridae is a group of ornithocheiroid pterosaurs from the Aptian-age Lower Cretaceous Yixian Formation of Liaoning, China.-Palaeoecology:...
, as Myers identifies it as being closely related to Boreopterus
Boreopterus
Boreopterus is a genus of ornithocheirid pterodactyloid pterosaur from the Barremian-Aptian-age Lower Cretaceous Yixian Formation of Dalian, Liaoning, China....
, and many ornithocheirid remains might belong to boreopterids instead.