Albertadromeus

Albertadromeus is an extinct genus of orodromine parksosaurid dinosaur known from the upper part of the Late Cretaceous Oldman Formation (middle Campanian stage) of Alberta, Canada. It contains a single species, Albertadromeus syntarsus.[1]

Albertadromeus
Temporal range: Late Cretaceous
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Parksosauridae
Subfamily: Orodrominae
Genus: Albertadromeus
Brown et al., 2013
Type species
Albertadromeus syntarsus
Brown et al., 2013

Etymology

The composite term Albertadromeus is derived from the name of the Canadian province "Alberta", and the Greek word dromeus (δρομεύς) meaning "runner", a reference to its inferred cursorial nature; thus "runner from Alberta". The specific name, syntarsus is derived from Greek words "syn" (συν) meaning "together" and "tarsus" (ταρσός) meaning "ankle", hence "together-ankle" a reference to the condition where its distal fibula is fused to its distal tibia. This dinosaur was described and named by Caleb Marshall Brown, David C. Evans, Michael J. Ryan & Anthony P. Russell in 2013 and the type species is Albertadromeus syntarsus.

Description

The holotype specimen of Albertadromeus TMP 2009.037.0044 consists of two dorsal vertebrae, a caudal vertebra, cervical ribs, ossified tendons, the left tibia and fibula, an incomplete right fibula, and a fragmentary metatarsal and ungual. The skull is unknown in this genus. The authors note that despite the few bones recovered, their moderate quality of preservation nonetheless provides enough morphological detail to allow for diagnosis on the species level.[1] Its elongate tibia has been strongly correlated with cursorial habits.[2] The tibia of Albertadromeus is slightly more elongate than that of Orodromeus, and significantly more elongate than that of Parksosaurus (ROM 804), Thescelosaurus (USNM 7757 and RSM P 1225.1), Hypsilophodon (NMHUK R5830), Dryosaurus (YPM 1876), and Stegoceras (UALVP 002).[1] Albertadromeus was a small-bodied, bipedal, cursorially adapted (built to run) ornithopod.

Diagnosis

According to Brown et al. (2013) Albertadromeus can be distinguished based on the following characteristics:[1]

  • The distal fibula is reduced to a thin sheet of bone that is fused to the anterior surface of tibia for the distal one-third of its length (shared with heterodontosaurids)
  • The lateral condyle of proximal tibia is strongly bilobed (shared with Changchunsaurus, Eocursor, Hypsilophodon, Jeholosaurus, Lesothosaurus, Orodromeus, Oryctodromeus, Stormbergia)
  • A prominent cnemial crest that projects dorsally (and anterolaterally), resulting in a posterior sloped dorsal extremity of the tibia (also present in Gasparinisaura and Micropachycephalosaurus).

Classification

Brown et al. (2013) erected a new taxon Orodrominae to differentiate those species that are more closely related to Orodromeus from those more closely related to Thescelosaurus. The validity of this new taxon is supported by the following: (a) the foramen magnum is between 20% and 30% of the width of the occipital condyle; (b) the pubis is articulated with a sacral rib; (c) there is a sharp and pronounced scapular spine; and (d) the fibular shaft is 'D'-shaped in cross-section. The new taxon Orodrominae includes the newly discovered dinosaur Albertadromeus, Zephyrosaurus, Orodromeus and Oryctodromeus. Phylogenetic analyses suggest that Albertadromeus forms a clade with Zephyrosaurus and Orodromeus, with Oryctodromeus being less closely related. The following is a cladogram based on the phylogenetic analysis conducted by Brown et al. in 2013, showing the relationships of Albertadromeus:[1]

Thescelosauridae
Orodrominae

TMP 2008.045.0002

Oryctodromeus

Albertadromeus

Orodromeus

Zephyrosaurus

Thescelosaurinae

Parksosaurus

Changchunsaurus

Haya

Jeholosaurus

Thescelosaurus assiniboiensis

Thescelosaurus neglectus

Paleoecology

The remains of the type specimen of Albertadromeus was recovered in the Canal Creek locality in the Upper Oldman Formation, which is part of the Belly River Group in Alberta, Canada. The specimen was collected in a two-meter-thick fine to very fine sandstone unit that was deposited during the Campanian stage of the Cretaceous period, approximately 77 to 76 million years ago. This specimen is housed in the collection of the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta.

Studies suggest that the paleoenvironment of the Oldman Formation was an ancient coastal plain.[3] This formation has produced the remains of the theropods Saurornitholestes, Daspletosaurus, Troodon, and Dromaeosaurus, the ceratopsids Albertaceratops, Chasmosaurus, Anchiceratops, and Coronosaurus, the hadrosaurids Brachylophosaurus, Gryposaurus, Parasaurolophus, and Corythosaurus, as well as other dinosaurs that shared that their paleoenvironment with Albertadromeus.

References

  1. ^ a b c d e Brown, C. M.; Evans, D. C.; Ryan, M. J.; Russell, A. P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology. 33 (3): 495. doi:10.1080/02724634.2013.746229.
  2. ^ Coombs, W. P., Jr. 1978. Theoretical aspects of cursorial adaptations in dinosaurs. The Quarterly Review of Biology 53:393–418.
  3. ^ Eberth, D.A., and Hamblin, A.P., 1993 , Tectonic, stratigraphic, and sedimentologic significance of a regional discontinuity in the upper Judith River Group (Belly River wedge) of southern Alberta, Saskatchewan, and northern Montana: Canadian Journal of Earth Sciences, 30, 174‒200.
Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

Melanorosauridae

The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Orodrominae

Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.

Parksosauridae

Parksosauridae is a clade or family of small ornithischians which have previously been generally allied to hypsilophodontids. Parksosauridae is often considered a synonym of Thescelosauridae, but the two groups cannot be synonyms because Parksosauridae is defined as a stem, while Thescelosauridae is defined as a node.

Raeticodactylidae

Raeticodactylidae is a family of eudimorphodontoid eopterosaurian pterosaurs that lived in Switzerland during the Late Triassic. The family includes Caviramus, and the type genus Raeticodactylus, which are both known from the Kössen Formation, around 205 mya. Raeticodactylidae was first used in 2014 by Andres et al., as a group of all pterosaurs closer to Raeticodactylus than Eudimorphodon. The following phylogenetic analysis follows the topology of Andres et al. (2014).

Riojasauridae

Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).

Thescelosaurinae

Thescelosaurinae is a subfamily of ornithischian dinosaurs from the Early Cretaceous of Asia and the Late Cretaceous of North America.

Unaysauridae

Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.

Xixiposaurus

Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.

Yueosaurus

Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.

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