Editing Albertosaurus (section)

==Description==
[[File:Albertoscale.svg|thumb|Size comparison]]
''Albertosaurus'' was a fairly large bipedal predator, but smaller than ''[[Tarbosaurus]]'' and ''Tyrannosaurus rex''. Typical ''Albertosaurus'' adults measured up to {{convert|8|-|9|m|ft|abbr=on}} long<ref name=russell1970>{{cite journal|last=Russell |first=Dale A. |author-link=Dale Russell |year=1970 |title=Tyrannosaurs from the Late Cretaceous of western Canada |journal=National Museum of Natural Sciences Publications in Paleontology |volume=1 |pages=1–34}}</ref><ref name=holtz2004>{{cite book |last=Holtz |first=Thomas R. |author-link=Thomas R. Holtz Jr. |year=2004 |chapter=Tyrannosauroidea |editor= Weishampel, David B. |editor-link= David B. Weishampel |editor2=Dodson, Peter |editor2-link=Peter Dodson |editor3=Osmólska, Halszka |title=The Dinosauria |edition=Second |publisher=University of California Press |location=Berkeley |pages=111–136 |isbn=978-0-520-24209-8}}</ref><ref name="paul2016"/> and weighed between {{convert|1.7|and|3.0|MT|ST}} in body mass.<ref name=christiansenfarina2004>{{cite journal |last=Christiansen |first=Per |author2=Fariña, Richard A. |year=2004 |title=Mass prediction in theropod dinosaurs |journal=Historical Biology |volume=16 |issue=2–4 |pages=85–92 |doi=10.1080/08912960412331284313|bibcode=2004HBio...16...85C |s2cid=84322349 }}</ref><ref name="paul2016">{{cite book|last=Paul|first=G.S.|year=2016|title=The Princeton Field Guide to Dinosaurs|edition=Second|publisher=Princeton University Press|pages=112|isbn=978-0-691-16766-4}}</ref><ref>{{cite journal|last1=Campione|first1=N. E.|last2=Evans|first2=D. C.|last3=Brown|first3=C. M.|last4=Carrano|first4=M. T.|date=2014|title=Body mass estimation in non-avian bipeds using a theoretical conversion to quadruped stylopodial proportions|journal=Methods in Ecology and Evolution|volume=5|issue=9|pages=913−923|doi=10.1111/2041-210X.12226|doi-access=free|bibcode=2014MEcEv...5..913C |hdl=10088/25281}}</ref><ref name=Larson08>{{cite book|editor1=Larson, P.|editor2=Carpenter, K.|year=2008|title=''Tyrannosaurus rex'', the Tyrant King (Life of the Past)|pages=310|isbn=9780253350879|publisher=Indiana University Press}}</ref>

''Albertosaurus'' shared a similar body appearance with all other tyrannosaurids, ''Gorgosaurus'' in particular. Typical for a theropod, ''Albertosaurus'' was bipedal and balanced its large, heavy head and [[torso]] with a long, muscular tail. However, tyrannosaurid forelimbs were extremely small for their body size and retained only two functional fingers, the second being longer than the first. The legs were long and ended in a four-toed foot on which the first toe, the [[hallux]], was very short and did not reach the ground. The third <!--'(middle)' - with four digits, here is no middle one; instead, there are two middle ones: the 2nd & 3rd.--> toe was longer than the rest.<ref name=holtz2004/> ''Albertosaurus'' may have been able to reach walking speeds of 14–21&nbsp;km/hour (8–13&nbsp;mi/hour).<ref>{{cite journal |last1= Thulborn |first1= Richard A. |year=1982 |title= Speeds and gaits of dinosaurs |journal= Palaeogeography, Palaeoclimatology, Palaeoecology | volume=38 |issue= 3–4 |pages=227–256 |doi=10.1016/0031-0182(82)90005-0 |bibcode= 1982PPP....38..227T }}</ref> At least for the younger individuals, a high running speed is plausible.<ref name=currie1998/>

Two skin impressions from ''Albertosaurus'' are known, and both show [[Scale (anatomy)|scales]]. One patch was found associated with some gastralic ribs and the impression of a long, unknown bone, indicating that the patch is from the belly. The scales are pebbly and gradually become larger and somewhat hexagonal in shape. Also preserved are two larger feature scales, placed 4.5&nbsp;cm apart from each other,<ref name=":0">{{Cite journal |last1=Bell |first1=Phil |last2=E. Campione |first2=Nicolás |last3=Scott Persons |first3=W |last4=J. Currie |first4=Philip |last5=Larson |first5=Peter |last6=Tanke |first6=Darren |last7=T. Bakker |first7=Robert |date=June 1, 2017 |title=Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution |journal=Biology Letters |volume=13 |issue=6 |pages=20170092 |doi=10.1098/rsbl.2017.0092 |pmc=5493735 |pmid=28592520}}</ref> making ''Albertosaurus'', along with ''[[Carnotaurus]]'', the only known theropods with preserved feature scales.<ref>{{Cite journal |last1=Hendrickx |first1=Christophe |last2=Bell |first2=Phil R. |last3=Pittman |first3=Michael |last4=Milner |first4=Andrew R. C. |last5=Cuesta |first5=Elena |last6=O'Connor |first6=Jingmai |last7=Loewen |first7=Mark |last8=Currie |first8=Philip J. |last9=Mateus |first9=Octávio |last10=Kaye |first10=Thomas G. |last11=Delcourt |first11=Rafael |date=June 2022 |title=Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs |url=https://onlinelibrary.wiley.com/doi/10.1111/brv.12829 |journal=Biological Reviews |language=en |volume=97 |issue=3 |pages=960–1004 |doi=10.1111/brv.12829 |pmid=34991180 |s2cid=245820672 |issn=1464-7931 |archive-date=September 28, 2022 |access-date=September 27, 2022 |archive-url=https://web.archive.org/web/20220928224916/https://onlinelibrary.wiley.com/doi/10.1111/brv.12829 |url-status=live }}</ref> Another skin impression is from an unknown part of the body. These scales are small, diamond-shaped, and arranged in rows.<ref name=":0" />

===Skull and teeth===
[[File:Albertosaurus skull cast.jpg|thumb|left|Skull cast at the [[Geological Museum in Copenhagen]]]]
The massive [[skull]] of ''Albertosaurus'', which was perched on a muscular, short, S-shaped neck, was about {{convert|1|m|ft|abbr=off}} long in the largest adults.<ref name=currie2003a>{{cite journal |last=Currie |first=Philip J. |author-link=Philip J. Currie |year=2003 |title=Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia |journal=Canadian Journal of Earth Sciences |volume=40 |issue=4 |pages=651–665 |doi=10.1139/e02-083 |bibcode=2003CaJES..40..651C |url=http://doc.rero.ch/record/14325/files/PAL_E1505.pdf |archive-date=December 23, 2023 |access-date=January 3, 2023 |archive-url=https://web.archive.org/web/20231223034524/https://doc.rero.ch/record/14325/files/PAL_E1505.pdf |url-status=live }}</ref> Wide openings in the skull, called [[fenestra]]e, provided space for [[muscle]] attachment sites and [[sensory organ]]s that reduced its overall weight. Its long jaws contained, both sides combined, 58 or more banana-shaped teeth. Larger tyrannosaurids possessed fewer teeth, but ''[[Gorgosaurus]]'' had 62. Unlike most theropods, ''Albertosaurus'' and other tyrannosaurids were [[heterodont]], with teeth of different forms depending on their position in the mouth. The [[premaxilla]]ry teeth at the tip of the upper jaw, four per side, were much smaller than the rest, more closely packed, and D-shaped in [[cross section (geometry)|cross section]].<ref name=holtz2004/> Like with ''Tyrannosaurus rex'', the maxillary (cheek) teeth of ''Albertosaurus'' were adapted in general form to resist lateral forces exerted by a struggling prey animal. The bite force of ''Albertosaurus'' was less formidable, however, with the maximum force, by the back teeth, reaching 3,413 Newtons.<ref>{{cite journal | last1 = Reichel | first1 = Miriam | year = 2010 | title = The heterodonty of ''Albertosaurus sarcophagus'' and ''Tyrannosaurus rex'': biomechanical implications inferred through 3-D models | journal = Canadian Journal of Earth Sciences | volume = 47 | issue = 9| pages = 1253–1261 | doi = 10.1139/e10-063 | bibcode = 2010CaJES..47.1253R }}</ref> Above the eyes were short bony crests that may have been brightly coloured in life and possibly used, by males in particular, in courtship to attract a mate.<ref name="ageofdinosaursalbertosaurus">"Albertosaurus." In: Dodson, Peter; Britt, Brooks; Carpenter, Kenneth; Forster, Catherine A.; Gillette, David D.; Norell, Mark A.; Olshevsky, George; Parrish, J. Michael; & Weishampel, David B. ''The Age of Dinosaurs''. Lincolnwood, Illinois: Publications International, Ltd., 1993. pp.&nbsp;106–107. {{ISBN|0-7853-0443-6}}.</ref>

[[File:Albertosaurus NT small.jpg|thumb|[[Life restoration]]]]
In 2001, [[William Abler]] observed that ''Albertosaurus'' [[tooth serrations]] resemble a [[Fracture|crack]] in the tooth ending in a round void called an ampulla.<ref name="abler-2001">Abler, W.L. 2001. A kerf-and-drill model of tyrannosaur tooth serrations. p.&nbsp;84–89. In: ''Mesozoic Vertebrate Life''. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.</ref> Tyrannosaurid teeth were used as holdfasts for pulling flesh off a body, so when a tyrannosaur pulled back on a piece of meat, the tension could cause a purely crack-like serration to spread through the tooth.<ref name="abler-2001" /> However, the presence of the ampulla distributed these forces over a larger [[surface area]] and lessened the risk of damage to the tooth under strain.<ref name="abler-2001" /> The presence of incisions ending in voids has parallels in human engineering. Guitar makers use incisions ending in voids to, as Abler describes, "impart alternating regions of flexibility and rigidity" to wood that they work on.<ref name="abler-2001" /> The use of a [[drill]] to create an "ampulla" of sorts and prevent the propagation of cracks through material is also used to protect aircraft surfaces.<ref name="abler-2001" /> Abler demonstrated that a plexiglass bar with incisions called "kerfs" and drilled holes was more than 25% stronger than one with only regularly placed incisions.<ref name="abler-2001" /> Unlike tyrannosaurs, more ancient predators, like [[phytosaur]]s and ''[[Dimetrodon]]'', had no adaptations to prevent the crack-like serrations of their teeth from spreading when subjected to the forces of feeding.<ref name="abler-2001" />