Editing Allosaurus (section)

===Life history===
[[File:Fossil displays - Natural History Museum of Utah - DSC07215.JPG|thumb|left|Skeletons at different growth stages on display, the [[Natural History Museum of Utah]]]]
The wealth of ''Allosaurus'' fossils, from nearly all ages of individuals, allows scientists to study how the animal grew and how long its lifespan may have been. Remains may reach as far back in the lifespan as [[egg]]s—crushed eggs from Colorado have been suggested as those of ''Allosaurus''.<ref name=DFG97/> Based on [[Histology|histological]] analysis of limb bones, bone deposition appears to stop at around 22 to 28 years, which is comparable to that of other large theropods like ''[[Tyrannosaurus]]''. From the same analysis, its maximum growth appears to have been at age 15, with an estimated growth rate of about 150 kilograms (330 [[pound (mass)|lb]]) per year.<ref name=PBetal06/>

Medullary bone tissue (endosteally derived, ephemeral, mineralization located inside the [[Bone marrow|medulla]] of the long bones in gravid female birds) has been reported in at least one ''Allosaurus'' specimen, a [[Tibia|shin bone]] from the [[Cleveland-Lloyd Dinosaur Quarry|Cleveland-Lloyd Quarry]]. Today, this bone tissue is only formed in female birds that are laying eggs, as it is used to supply [[calcium]] to shells. Its presence in the ''Allosaurus'' individual has been used to establish sex and show it had reached reproductive age.<ref name=LW08>{{cite journal |last1=Lee |first1=Andrew H. |year=2008 |title=Sexual maturity in growing dinosaurs does not fit reptilian growth models |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=105 |issue=2 |pages=582–587 |doi=10.1073/pnas.0708903105 |pmid=18195356 |last2=Werning |first2=S |pmc=2206579|bibcode = 2008PNAS..105..582L |doi-access=free }}</ref> However, other studies have called into question some cases of medullary bone in dinosaurs, including this ''Allosaurus'' individual. Data from extant birds suggested that the medullary bone in this ''Allosaurus'' individual may have been the result of a bone pathology instead.<ref name=Chin09>{{cite journal | last1 = Chinsamy | first1 = A. | last2 = Tumarkin-Deratzian | first2 = A. | year = 2009 | title = Pathological Bone Tissues in a Turkey Vulture and a Nonavian Dinosaur: Implications for Interpreting Endosteal Bone and Radial Fibrolamellar Bone in Fossil Dinosaurs | journal = Anat. Rec. | volume = 292 | issue = 9| pages = 1478–1484 | doi=10.1002/ar.20991| pmid = 19711479 | s2cid = 41596233 | doi-access = free }}</ref> However, with the confirmation of medullary tissue indicating sex in a specimen of ''Tyrannosaurus'', it may be possible to ascertain whether or not the ''Allosaurus'' in question was indeed female.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2016/03/160315085637.htm |title= Pregnant T. rex could aid in dino sex-typing | date=March 15, 2016 |work=Science Daily |archive-url=https://web.archive.org/web/20160414064736/https://www.sciencedaily.com/releases/2016/03/160315085637.htm |archive-date=April 14, 2016}}</ref>
[[File:Allosaurus Juvenile Reconstruction.jpg|thumb|Restoration of a juvenile ''Allosaurus'']] 
The discovery of a juvenile specimen with a nearly complete hindlimb shows that the legs were relatively longer in juveniles, and the lower segments of the leg (shin and foot) were relatively longer than the thigh. These differences suggest that younger ''Allosaurus'' were faster and had different hunting strategies than adults, perhaps chasing small prey as juveniles, then becoming ambush hunters of large prey upon adulthood.<ref name=FC06/> The [[thigh bone]] became thicker and wider during growth, and the cross-section less circular, as muscle attachments shifted, muscles became shorter, and the growth of the leg slowed. These changes imply that juvenile legs has less predictable stresses compared with adults, which would have moved with more regular forward progression.<ref name=LCS02>{{cite journal |last=Loewen |first=Mark A. |year=2002 |title=Ontogenetic changes in hindlimb musculature and function in the Late Jurassic theropod ''Allosaurus'' |journal=Journal of Vertebrate Paleontology |volume=22 |issue=3, Suppl |page=80A }}</ref> Conversely, the skull bones appear to have generally grown [[allometry|isometrically]], increasing in size without changing in proportion.<ref name=KC2010/>