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===Relationship of ''Gorgosaurus'' and ''Albertosaurus''===
===Relationship of ''Gorgosaurus'' and ''Albertosaurus''===
The close similarities between ''Gorgosaurus libratus'' and ''Albertosaurus sarcophagus'' have led many experts to combine them into one genus over the years. ''Albertosaurus'' was named first, so by convention it is given [[Principle of Priority|priority]] over the name ''Gorgosaurus'', which is sometimes considered its [[junior synonym]]. [[William Diller Matthew]] and [[Barnum Brown]] doubted the distinction of the two genera as early as 1922.{{sfn|Matthew & Brown|1922}} ''Gorgosaurus libratus'' was formally reassigned to ''Albertosaurus'' (as ''Albertosaurus libratus'') by [[Dale Russell]] in 1970,{{sfn|Russell|1970}} and many subsequent authors followed his lead.{{sfn|Carr ''et al.''|2005}}{{sfn|Paul|1988}} Combining the two greatly expands the geographical and chronological range of the genus ''Albertosaurus''. Other experts maintain the two genera as separate.{{sfn|Holtz|2004}} Canadian paleontologist [[Phil Currie]] claims there are as many anatomical differences between ''Albertosaurus'' and ''Gorgosaurus'' as there are between ''Daspletosaurus'' and ''Tyrannosaurus'', which are almost always kept separate. He also notes that undescribed tyrannosaurids discovered in [[Alaska]], [[New Mexico]] and elsewhere in North America may help clarify the situation.{{sfn|Currie|2003}} [[Gregory S. Paul]] has suggested that ''Gorgosaurus libratus'' is ancestral to ''Albertosaurus sarcophagus''.{{sfn|Paul|2010}}
The close similarities between ''Gorgosaurus libratus'' and ''Albertosaurus sarcophagus'' have led many experts to combine them into one genus over the years. ''Albertosaurus'' was named first, so by convention it is given [[Principle of Priority|priority]] over the name ''Gorgosaurus'', which is sometimes considered its [[junior synonym]]. [[William Diller Matthew]] and [[Barnum Brown]] doubted the distinction of the two genera as early as 1922.{{sfn|Matthew & Brown|1922}} ''Gorgosaurus libratus'' was formally reassigned to ''Albertosaurus'' (as ''Albertosaurus libratus'') by [[Dale Russell]] in 1970,{{sfn|Russell|1970}} and many subsequent authors followed his lead.{{sfn|Carr ''et al.''|2005}}{{sfn|Paul|1988}} Combining the two greatly expands the geographical and chronological range of the genus ''Albertosaurus''. Other experts maintain the two genera as separate.{{sfn|Holtz|2004}} Canadian paleontologist [[Phil Currie]] claims there are as many anatomical differences between ''Albertosaurus'' and ''Gorgosaurus'' as there are between ''Daspletosaurus'' and ''Tyrannosaurus'', which are almost always kept separate. He also notes that undescribed tyrannosaurids discovered in [[Alaska]], [[New Mexico]] and elsewhere in North America may help clarify the situation.{{sfn|Currie|2003}} [[Gregory S. Paul]] has suggested that ''Gorgosaurus libratus'' is ancestral to ''Albertosaurus sarcophagus''.{{sfn|Paul|2010}}

===Phylogeny===
Albertosaurinae is a [[basal (phylogenetics)|basal]] [[subfamily]] of tyrannosaurid. They were recognized in the 2014 analysis of the new genus ''[[Nanuqsaurus]]'', a [[derived]] tyrannosaurine, the sister group to Albertosaurinae.<ref name="nanuq">{{cite doi|10.1371/journal.pone.0091287}}</ref> ''Albertosaurus'' and ''Gorgosaurus'' are kept separate by most classifications, as should be, stated by Currie.{{sfn|Currie|2003}} The cladogram below was found during the analysis of ''Nanuqsaurus'' by [[Mark A. Loewen]] ''et al.''.<ref name="nanuq"/>

{{clade| style=font-size:90%; line-height:90%
|label1=[[Tyrannosauridae]]
|1={{clade
|label1='''Albertosaurinae'''
|1={{clade
|1=''[[Albertosaurus]]''
|2=''[[Gorgosaurus]]'' }}
|label2=[[Tyrannosaurinae]]
|2={{clade
|1={{clade
|1=''[[Daspletosaurus]]''
|2=Two Medicine taxon }}
|2={{clade
|1=''[[Teratophoneus]]''
|2={{clade
|1=''[[Bistahieversor]]''
|2={{clade
|1=''[[Lythronax]]''
|2={{clade
|1=''[[Nanuqsaurus]]''
|2={{clade
|1={{clade
|1=''[[Tarbosaurus]]''
|2=''[[Zhuchengtyrannus]]'' }}
|2=''[[Tyrannosaurus]]'' }} }} }} }} }} }} }} }}


==References==
==References==

Revision as of 00:30, 18 April 2014

Albertosaurines
Temporal range: Late Cretaceous, 76.6–68 Ma
Skull replica of Albertosaurus, on display in the Geological Museum in Copenhagen
Albertosaurus skull cast
Top-right view of a Gorgosaurus skull in the American Museum of Natural History
Gorgosaurus skull
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Superfamily: †Tyrannosauroidea
Clade: †Pantyrannosauria
Clade: †Eutyrannosauria
Family: †Tyrannosauridae
Subfamily: †Albertosaurinae
Currie et al., 2003
Type species
Albertosaurus sarcophagus
Genera[2]

†Albertosaurus (type genus)
†Gorgosaurus
†Alioramus?[1]

Albertosaurines, or dinosaurs of the subfamily Albertosaurinae, lived in the Late Cretaceous of USA and Canada. The subfamily was first used by Philip J. Currie, Jørn H. Hurum and Karol Sabath as a group of tyrannosaurid dinosaurs. It was originally defined as "(Albertosaurus + Gorgosaurus)", including only the two genera. The group is sister clade to Tyrannosaurinae. In 2007, it was found that the group also contained Maleevosaurus, often synonymized with Tarbosaurus. However, this classification has not been accepted, and Maleevosaurus is still considered a juvenile Tarbosaurus or Tyrannosaurus. Clevenger T. M. McLain found in an abstract, that Alioramus, commonly used as a derived tyrannosauroid, was an albertosaurine, or the sister taxon to the group.

Description

Albertosaurines are large, lightly built tyrannosaurids. Compared to tyrannosaurines, they are lightly built, have shorter, flatter skulls, had shorter ilia, and had proportionally longer tibiae. Albertosaurines and tyrannosaurines share arms or about equal length, with the exception of Tarbosaurus, who's arms a shorter for its size.[3]

Albertosaurus was smaller than some other tyrannosaurids, such as Tarbosaurus and Tyrannosaurus. Typical adults of Albertosaurus and Gorgosaurus measured up to 8 to 9 metres (26 to 30 feet) long,[4][5] while rare individuals of Albertosaurus could grow to over 10 metres (33 feet) in length.[6] Several independent mass estimates, obtained by different methods, suggest that an adult Albertosaurus weighed between 1.3 tonnes (1.4 short tons; 1.3 long tons)[7] and 1.7 tonnes (1.9 short tons; 1.7 long tons).[8] Gorgosaurus estimates are higher, at around 2.5 tonnes (2.8 short tons; 2.5 long tons),[9] although greater estimates exist of about 2.8 tonnes (3.1 short tons; 2.8 long tons).[10]

All tyrannosaurids, including Albertosaurus, shared a similar body appearance. Typically for a theropod, Albertosaurus was bipedal and balanced the heavy head and torso with a long tail. However, tyrannosaurid forelimbs were extremely small for their body size and retained only two digits. The hind limbs were long and ended in a four-toed foot. The first digit, called the hallux, was short and only the other three contacted the ground, with the third (middle) digit longer than the rest.[5] Albertosaurus may have been able to reach walking speeds of 14−21 kilometres per hour (8−13 miles per hour).[11] At least for the younger individuals, a high running speed is plausible.[12]

Classification and systematics

The subfamily was first used by Philip J. Currie, Jørn H. Hurum and Karol Sabath as a group of tyrannosaurid dinosaurs. It was originally defined as "(Albertosaurus + Gorgosaurus)", including only the two genera. The group is sister clade to Tyrannosaurinae.[2] In 2007, it was found that the group also contained Maleevosaurus, often synonymized with Tarbosaurus.[13] However, this classification has not been accepted, and Maleevosaurus is still considered a juvenile Tarbosaurus or Tyrannosaurus.[3] Clevenger T. M. McLain found in an abstract, that Alioramus, commonly used as a derived tyrannosauroid, was an albertosaurine, or the sister taxon to the group.[1]

Albertosaurus is a member of the theropod family Tyrannosauridae, in the subfamily Albertosaurinae. Its closest relative is the slightly older Gorgosaurus libratus (sometimes called Albertosaurus libratus; see below).[2] These two species are the only described albertosaurines; other undescribed species may exist.[14] Thomas Holtz found Appalachiosaurus to be an albertosaurine in 2004,[5] but his more recent unpublished work locates it just outside Tyrannosauridae,[15] in agreement with other authors.[16] The other major subfamily of tyrannosaurids is the Tyrannosaurinae, including genera such as Daspletosaurus, Tarbosaurus and Tyrannosaurus.[14][2]

Relationship of Gorgosaurus and Albertosaurus

The close similarities between Gorgosaurus libratus and Albertosaurus sarcophagus have led many experts to combine them into one genus over the years. Albertosaurus was named first, so by convention it is given priority over the name Gorgosaurus, which is sometimes considered its junior synonym. William Diller Matthew and Barnum Brown doubted the distinction of the two genera as early as 1922.[17] Gorgosaurus libratus was formally reassigned to Albertosaurus (as Albertosaurus libratus) by Dale Russell in 1970,[4] and many subsequent authors followed his lead.[16][18] Combining the two greatly expands the geographical and chronological range of the genus Albertosaurus. Other experts maintain the two genera as separate.[5] Canadian paleontologist Phil Currie claims there are as many anatomical differences between Albertosaurus and Gorgosaurus as there are between Daspletosaurus and Tyrannosaurus, which are almost always kept separate. He also notes that undescribed tyrannosaurids discovered in Alaska, New Mexico and elsewhere in North America may help clarify the situation.[14] Gregory S. Paul has suggested that Gorgosaurus libratus is ancestral to Albertosaurus sarcophagus.[19]

Phylogeny

Albertosaurinae is a basal subfamily of tyrannosaurid. They were recognized in the 2014 analysis of the new genus Nanuqsaurus, a derived tyrannosaurine, the sister group to Albertosaurinae.[20] Albertosaurus and Gorgosaurus are kept separate by most classifications, as should be, stated by Currie.[14] The cladogram below was found during the analysis of Nanuqsaurus by Mark A. Loewen et al..[20]

Tyrannosauridae

References

Footnotes

  1. ^ a b McLain 2012.
  2. ^ a b c d Currie et al. 2003.
  3. ^ a b Currie 2002.
  4. ^ a b Russell 1970.
  5. ^ a b c d Holtz 2004.
  6. ^ Erickson et al. 2006.
  7. ^ Erickson et al. 2004.
  8. ^ Christiansen & Fariña 2004.
  9. ^ Seebacher 2001.
  10. ^ Henderson 2007.
  11. ^ Thulborn 1982.
  12. ^ Currie 2000.
  13. ^ Saveliev & Alifanov 2007.
  14. ^ a b c d Currie 2003.
  15. ^ Holtz 2005.
  16. ^ a b Carr et al. 2005.
  17. ^ Matthew & Brown 1922.
  18. ^ Paul 1988.
  19. ^ Paul 2010.
  20. ^ a b Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1371/journal.pone.0091287, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1371/journal.pone.0091287 instead.

Citations

External links

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