Lecture 6: and

Saurischia Term coined by Seeley (an employee of the Cambridge Museum) in 1887 Name is based on the anteriorlly-oriented of most (but not all saurischians). This is not a shared derived trait; it is a primitive trait from deep in Reptilia

Shared derived characters of Saurischia: Twisted ( 1) Reduced pinky (digit 5) New articulation points in dorsal vertebrae (hyposphene-hypantrum articulation) Elongation of forward neck (cervical) vertebrae

Controversy over placement of earliest, carnivorous (, , etc.). 1) 2) Basal Theropod (this is what I told you in ) 3) Basal Saurischian

OUTLINE OF THEROPOD LECTURE 1. Defining characteristics of 2. Distribution in time and place 3. Lifestyle issues

Theropods 1. Defining characteristics of clades Theropoda (‘beast foot’, really -footed) General characters: bipedal, (more or less), less abundant than herbivorous dinosaurs (only ½ to 1/11 as numerous), less diverse than (only 40%), classification nightmares, ranged in size from <2 feet/10 lbs. to 50 feet or more and 5-7 tons.

Shared derived characters: big eyes, extra , broad lachrymal (“tear-duct”) bone, 3 elongate fingers (vestigal 4th and 5th digits) with grasping capability, narrow hind foot with three functional digits, hollow bones, bowed , with at least 5 vertebrae, pubic “boot”, tails stiff distally used as counterbalances, loosely-jointed kinetic

Long bones are hollow - have an outer layer of dense, compact bone that is far thicker than that of other dinosaurs; spongy bone confined to the articulation zones and edge of the marrow cavity.

1 Shared derived characters: Reduction and fusion of skeleton, specifically the upper ankle bones and the sacral ribs with the , ridges around hip socket for support, in most - notch between and premaxilla on upper jaw to accept large lower tooth

Representative genera: (7 m), (2-3 m), Syntarsus, Ceratosaurs existed from the Late through the Late , global distribution

Tetanurae Shared derived characters: Overall, more bird-like than ceratosaurs: Large portions of the tail stiffened by extended bony struts (zygopophyses); tooth row doesn’t extend behind antorbital opening)

Spinosauroidea Shared derived characters: Large snouts, strong shoulders, long arms and clawed hands; probable fish eaters Representative genera: (10 m), (10 m), (~18 m), (7 m) + see below, and including knopfleri (2 m spinosauroid from Madagascar named after Dire Straits guitarist Mark Knopfler) – Early , global distribution

*Note: Spinosaurus was first discovered in Egypt in 1915; specimens in Munich were destroyed during the allied bombing in WW II. More remains from the Bahariya oasis have recently been found by grad students from Penn

Carnosauria Shared derived characters: Big nostrils with elaborate sinuses, big heads, all more than 5 m long Representative genera: , Late Jurassic – , global distribution

Coelurosauria Shared derived characters: Big brains, elongate forelimb, arctometatarsal ankle, very bird-like

Tyrannosauroidea Shared derived characters: Very reduced forelimbs with only 2 functional fingers, 14-15 m long

Ornithomimosauria Shared derived characters: Small, lightly built skulls with very large orbits, no upper teeth, few lower teeth, long arms Very -like 2

Oviraptosauria Shared derived characters: Short skulls with many fenestrae, no teeth, wishbone

Therizinosauroidea “The giant claw” Shared derived characters: very long claws, teeth adapted for plant-eating

Troodontidae Shared derived characters: Huge front-facing eyes, very large brain

Dromaeosauridae Shared derived characters: Enlarged claw on 2nd , rear-facing pubis One spectacular of captures it in a struggle with a

3 2. Distribution in time and place Ceratosauria: through the Late Jurassic, global distribution Spinosauroidea: Late Jurassic – Early Cretaceous, global distribution : Late Jurassic – Early Cretaceous, global distribution : Early - , largely

3. Lifestyle issues a. Habitats Theropods lived in all habitats! b. Preservation and Theropod are relatively rare (delicate bones), however some spectacular nearly complete fossils have been found and there are at least two theropod bone beds: the Coelophysis quarry at (where 5-10,000 skeletons and partial skeletons of the dinosaur Coelophysis bauri have been found) and the Cleveland-Lloyd quarry in Utah where the remains of at least 44 Allosaurus have been found.

It is unusual for large numbers of carnivores to amass, so the sites above must be anomalous. c. Diet i. The "Great" Debate: was T. rex a predator (using a chasing or ‘land shark’ ambush approach) or a scavenger? Evidence for Evidence for scavenging May have had pockets on teeth that Had rounded (crushing) rather than housed bacteria (for poisoning victims; flattened (slicing) teeth Komodo dragons have these too) Analysis of bone with bite Teeth typically found in mass death marks indicates a very strong bite deposits potential (13,000 newtons, like that of an alligator) Arms too small to hold on to struggling prey analysis shows that tyrannosaur Large olfactory lobes in brains (for had vertically oriented orbits, like other detecting rotting meat) carnivores with very strong bites T. rex couldn’t run fast enough to catch prey **The Truth? T. rex probably did both

Tyrannosaurs were clearly alpha carnivores (bone-filled coprolites are direct evidence). ii. – used tough for eating shellfish, seeds, or ? iii. Spinosauroids – fish eaters? (narrow snouts, long claws) 4 iv. Ornithomimids – some are found with and one has a mouth full of baleen – they were almost certainly not carnivores d. Senses Smell: tyrannosaurs had huge olfactory lobes

Vision: based on the positions of their orbits, tyrannosaurs also had excellent stereoscopic vision (over a 50° range) and depth perception; the had an even larger range of stereoscopic view (~130°, the same as modern cats), but many theropods had a much more restricted range for excellent depth perception (e.g. Carcharadontosaurus = 20°)

Hearing: Theropods all had large auditory canals, which probably equated to excellent hearing; had an extra feature: an aural canal that connected the two ears and allowed for outstanding sound location e. Living arrangements Several fossil sites contains groups of one theropod species (e.g. ), suggesting that theropods, like many modern carnivores, lived and hunted in packs or prides f. Nesting Little evidence of theropod parental skills or strategies. However, one exceptional nest in preserves an brooding its eggs and an Albertasaurus site in Canada includes both adults and sub-adults. These suggest significant parental care. g. Moving around All theropods were obligate bipeds (very long legs, trackways always narrow). Estimates based on trackways, leg lengths and leg proportions suggest that large theropods like T. rex might have been able to run as fast as 50 km/h or more Functional analysis of the T. rex skeleton suggest that it couldn’t run faster than about 30 km/h because of the unrealistic amount of muscle mass needed to move faster and because of potential damage to the skull if it fell Tails would have been important counterbalances in large running theropods! Ornithomimids could probably run fast – up to 80 km/hr (based on leg length, leg proportions, trackway evidence) h. Brains and behavior Theropods had the largest EQ’s of any dinosaur , and the EQ of troodontids and dromaeosaurs was well above that of any living , and very much like that of some modern and mammals.

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