War! Arms Race In The Time of The Dinosaurs: Allosaurus Madison Blankenship Bio 425 Spring 2009

Allosaurus Natural History Museum DC. February 28, 2009

What is the classification of the Allosaur? The Allosaurus order Saurischia Means “lizard, hip jointed” (Martin, 2006) 1 Allosaurs suborder Theropoda Belong to group called Tetanurae,“stiff tail”. (Martin, 2006) 2 This group most debated similar traits to birds. Before phylogentic classifications Carnosauria grouped the Allosaur.

Equipment for War! Allosaurus Pelvis Natural History Museum, DC. February 28, 2009

What is the classification of the Allosaur? Cont. Now “regarded as a stem based clade” Allosaurs are still grouped here in this regard. (Martin, 2006) 3 According to Martin the Carnosauria clade is also included in Avetheropoda. (Martin, 2006) 4 Allosauroidea the family of Allosaurs Genus Allosaurus Currently three known species of Allosaur.

Related Tetanurans Tetanurans are represented by Allosaurids. (a) Giganotosaurus (b) Yangchuanosaurus (Martin, 2006) 10

Questions Addressed: What adaptations to Allosaurids have that allow them to acquire prey? Does pack behavior influence acquiring prey?

Theropoda Anatomy-Generalized Shows assumed muscular Structure of Tyrannosaurus Shows assumed organ placement of Tyrannosaurus Insiders-Dinosaurs Long, John

Equipment for War! Theropoda Traits: Feet and legs demonstrate bipedal motion. Hands able to grasp. Limb bones are hollow. (Allowed for an increase in mobility but also thought to have helped with flight in other Theropod lineages) (Martin, 2006) 5 Flexable Jaw Manus that has claws reduction or loss thereof of 4 and 5 th digit.

Anatomy of an Allosaur (Martin, 2006) 7

Equipment for War! Theropoda Traits Continued.: Long and well defined processes on cervical and caudal vertebrae Toes with digits 2-4 Digit 1 isolated Digit 5 reduced or absent “More than 20 synapomorphies define Theropoda” (Martin, 2006) 6 Some are shown to have high brain-mass/body ratios roughly suggesting that they are “brainier” than other dinosaurs (Martin, 2006)8

Theropoda Characters Left Theropod hand Middle Theropod Foot Right-Cervical Vertebra (Neck) Caudal Vertebra (Lower) (Martin, 2006) 9

Allosaurus: Weapons of War! Existed Late Jurassic (mya) Fossils found western and central USA Pneumatic bones located skull, vertebrae, and costae Pneumatic-air filled spaces. Main function support. Sacs of air filled from Theropods lungs. Allowed for bigger skulls than body in larger Theropods because “puts less strain on cervical vertebrae.” (Martin, 2006) 5

Allosaurus: Weapons of War! Pneumatic bones lightweight support no weight of extra bones This characteristic in other orders not as pronounced as in Theropoda. More expressed in Theropoda than the other clades. (Martin, 2006) 5 Allosaurus is a good example of the pneumatic characteristic. Upper jaws were used like a “war club, with each small tooth acting as a mega-serration.” (Bakker R.T. 1998)

Allosaurus: Weapons of War! This would allow them to take on prey much larger than them. Such as a large Sauropod. “An Allosaurid would not kill a Sauropod in single bite, but weaken prey repeated attacks.” (Bakker, R.T., 1998) The Allosaur has a binocular field vision 20 degrees front (STEVENS, 2006) It utilized “binocular overlap” in front but this limited because of “narrow set eyes, tall rostrum (snout), and prominent lachrymals”, 2006) (STEVENS, 2006).

The Allosaurus Bite! A Weapon Indeed! R.T. Bakker, 1998, page 147 R.T. Bakker, 1998, page 150

Allosaurus Occipital View of Skull Notice the highlighted area. This is where the pneumatic space is located on the skull. (R.T. Bakker, 1998, page 151)

Long axis inclination- 150 degrees=strong teeth, weak skulls 95 degrees= strong teeth strong skulls. Elliptical orbits + correlated skull strength. Picture demonstrates larger orbital weaker in Compsognathus, stronger in Allosaurus, very strong Tyrannosaurus. Orbitals important - resistance to muscle generated forces-prey capture and dismemberment (Henderson 2002).

To Be Social or Not? Some evidence suggests Allosaurus hunted in social groups rather than alone. Large numbers Allosaurus at Cleveland-Lloyd Quarry, thought to be “predator trap.” (Farlow et. al 1999) Prey trapped in quicksand, tar or mud and calls of distress heard by predators they get trapped.

Cleveland Lloyd Dinosaur Quarry

To Be Social or Not? Cont. Thought explain the sediments found Cleveland-Lloyd Quarry (Farlow et. al 1999) Also thought a trap because Allosaurus accumulating over time-not all at once (Farlow et. al 1999) Head biting for dominance has also been proposed for intraspecies rivalry. (Currie et. al 1998) Head biting for resolve territory disputes or establishing dominance in a pack (Currie et. al 1998)

To be Social or Not Cont. Cranial injuries made by teeth are analyzed to determine cause. Injuries only found on one-Labrosaurus ferox. Labrosaurus ferox named because of a lower jaw oddity. Now thought as an injury to Allosaurus Fragilis. (Currie et. al 1998) Obviously, much speculation of behaviors cofounds positive answers on pack behavior or lone predator that defends itself assumption.

Future Research: Dig deeper into literature to really try to find a good answer to Allosaurus social behavior. Look for more specific behaviors of the Allosaurus.

Works Cited: (1) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 10. Table 1.1 Summary of different major clade groups use to classify dinosaurs, general descriptions of anatomical characteristics for each group and genus examples. (2) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 266. (3) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 267. (4) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page10. (5) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 258. (6) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 257. (7) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 125. (8) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 260. (9) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 259. (10) Martin, Anthony J. Introduction to the Study of Dinosaurs (2006). Page 268. Farlow, James O., Surman, Brett M. K. Walters, Robert F. The Complete Dinosaur (1999). Page 228. Currie, P.J. Tanke, D.H. “Head-Biting Behavior in Theropod Dinosaurs: Paleopathological Evidence” 1998 GAIA N Bakker Robert T. “Brontosaur Killers: Late Jurassic Allosaurids As Saber-tooth Cat Analogues” 1998 GAIA N

Works Cited: STEVENS, KENT A. “BINOCULAR VISION IN THEROPOD DINOSAURS” (2006) Journal of Vertebrate Paleontology 26(2):321–330. (1) Long, John. Insiders-Dinosaurs (2007). Page (Walking With Dinosaurs-BBC footage- clip)(Music-An Epic Age by Immediate) Creator (AustralianFalcon) HENDERSON, DONALD M.THE EYES HAVE IT: THE SIZES, SHAPES, AND ORIENTATIONS OF THEROPOD ORBITS AS INDICATORS OF SKULL STRENGTH AND BITE FORCE. Journal of Vertebrate Paleontology 22(4):766–778, December 2002.