CLASS 11: ANATOMY & SAUROPODOMORPHS I. BASIC DINOSAUR ANATOMY Anatomical orientation Anterior - front Posterior - back Dorsal - top Ventral - bottom Proximal - near Distal - far Medial - towards the middle Lateral - towards the side Major parts of the skeleton you should know Vertebral column: cervical (neck), thoracic (attach to rib), sacral (attach to pelvis), and caudal (tail) vertebrae. Sacral vertebrae = sacrum Forelimb: Scapula, Coracoid, Humerus, Radius, Ulna, Wrist (carpels), Finger bones (metacarpels and phalanges) Hindlimb: Pelvis = Ilium, Pubis, Ischium, Femur, Tibia, Fibula, Ankle (tarsals = Astragalus, Calcaneum), Toe bones (metatarsals and phalanges) Head bony parts: Lower jaw: dentary (with teeth), articular (lower jaw joint), others bones Upper jaw: premaxilla and maxilla (both with teeth), quadrate (upper jaw joint) Skull: skull roof bones (nasals, frontals, parietals, etc.), cheek and eye bones (jugal, lacramal, post-orbital, etc.), palate bones, braincase, occipital condyle (head-neck joint) Head holes: foramen magnum (hole where spinal cord enters braincase), antorbital fenestra, upper and lower temporal fenestra, mandibular fenestra (on lower jaw) Sauropodomorpha All herbivores Shared derived traits Small head (5% body length), long neck with at least 10 vertebrae, elongate peg- like teeth with coarsely serrated crowns, large thumb with claw, long femur, large obturator foramen in pubis Prosauropoda few easily diagnosed shared features whopping big thumb claw that is further twisted, elongate cervical vertebrae (Also: small 5th digit on hind foot, iguana-like teeth) Some used gastroliths Quadrupeds and facultative bipeds Plateosaurus, Anchisaurus, Mussasaurus (representative genera) Known from Late Triassic through Early Jurassic Global distribution (Pangean) These represent the earliest plant-eating dinosaurs, which presumably evolved from bipedal meat eaters. 1 Sauropoda Includes the largest land animals of all time (7 – 45 m) A number of primitive basal groups, build up key traits Shared derived characters from Sauropoda to Neosauropoda shortened skulls, rounded snout with the lower temporal opening beneath the orbit 12+ cervical vertebrae with pleurocoels uniformly large, massive and solid limb bones long tails five fingers/toes on each appendage Least derived genera: Vulcanodon (21 feet long), Shunanosaurus (33 feet), Mamenchiasaurus (72 feet) Camarasauromorpha (~60 feet long, 20 tons) Shared derived: Large external nares, relatively long forelimbs, relatively short neck Camarasaurus: short skull, deep pleurocoels, bifurcate cervical neural spines Brachiosaurids Representative genus is Brachiosaurus (a supergiant, Ultrasaurus may be a large Brachiosaurus) Shared, derived traits: even longer front legs, 13 elongate cervical vertebrae (with non-bifurcate neural spines), neck joint vertically oriented (their neck were designed to be held vertically), distinctive snouts, vaulted brows Other supergiants: Sauroposeidon (see below) (cervical vertebrae = 4 feet long!) Titanosauria (mostly, but not entirely, southern hemisphere) Shared derived characters: osteoderms, very robust radius and ulna Also: long, broad snouts, nostrils high on head, pencil-like teeth at the very front of the jaws, very long necks Alamosaurus (30 feet, North America) and Saltasaurus (40 feet, South America) are representative genera Magyarosaurus dacus (5-6 m), discovered by Baron Nopcsa, in Transylvania, was unusually small and thought to have been an island dinosaur Also includes the supergiants: Paralititan, Bruhathkayosaurus, Argentinasaurus, Argyrosaurus (see below) 2 Diplodocoidea Shared, derived characters Peg-like teeth, 12+ cervical vert with bifurcate neural spines, neck joint horizontally oriented, at least 80 caudal vertebrae, odd chevron in mid-tail region Elongate sub-rectangular snout, External nares fully retracted Representative genera: Apatosaurus (70 feet, Late Jurassic of N. America) Includes the supergiantsL Barosaurus, Diplodocus, Supersaurus, Seismosaurus (see below) Supersize It Family Genus Length Weight Period Location Brachiosauridae Brachiosaurus 30 m 85-110 tons Late Jur Colorado Ultrasaurus 43 m 85-110 tons Late Jur Algeria, Tanzania Sauroposeidon 20 m tall 60 tons Late Cret Oklahoma Titanosauridae Paralititan 33 m 65-80 tons Late Cret Egypt Bruhathkayaosaur 48 m 175 tons Late Cret India us Argentinasaurus 40 m 80-100 tons Late Jur S. Amer. Argyrosaurus 31 m 45-55 tons Late Cret S. Amer. Diplodocidae Diplodocus 30 m 10-55 tons Late Jur N. Amer. Barosaurus 30 m 10-55 tons Late Jur Wyoming Supersaurus 43 m 85-110 tons Late Jur Utah Seismosaurus 50 m 80-100 tons Late Jur New Mex. B. Where Existed from Early Jurassic to end Cretaceous times; global distribution Late Jurassic was the heyday of abundance and diversity in North America In North America, there was a sauropod hiatus through most of the Late Cretaceous, with sauropods present in the fossil record only at the very end of the period 3 C. Lifestyles 1. Communication Diplodocid tails: are built like bullwhips and may have been ‘snapped’ as a means of communication or warning to potential predators Supersonic diplodocid tails? For: Against: 1. Tail proportions work 1. Tail tips highly vul- (6% rule) nerable to damge on impact 2. Extreme thinness and elongation of distal 2. No poppers found in caudal vertebrae Fossil Record 3. Unusually long, stiffened caudal vertebrae in the 18-25 position “It is pleasant to think that the first residents of Earth to break the sound barrier were not humans.” 2. Taphonomy Many disarticulated sauropod bones in bone beds Few sauropod heads (small heads, weak neck joints) Supergiant saurpods remains = rare and generally extremely fragmentary 3. Habitats Occupied a wide range, but were not habitual lagoon-dwellers as thought in the bad old days (i.e. the high nostrils of diplodocids were not used as snorkels; they may have been relatively lowly placed and/or they may have supported trunks! And/or we don’t understand their true function yet) 4. The challenges of being big a. Structural stability: discussed already b. Nutrition: finding enough food and digesting enough food a challenge for very large animals. Sauropods may have migrated to optimize foraging, and many of them relied on gastroliths for digestive help. 4 Sauropods no doubt produced voluminous quantities of dung (see below); not surprisingly the first fossil evidence of dung beetles is found in the Late Jurassic (as burrows in coprolites) Food and eating: Cows (~1000 lbs.) Elephants (~12,000 lbs.) WASTE MATERIAL ~100lbs. Food/day ~600lbs. Food/day (1/10th wt.) (1/20th wt.) 4 lbs./hr. 25lbs./hr. COW ELEPHANT DIPLODOCID Big diplodocid 1,000 lb 12,000 lb 100,000 lb (~100,000 lbs.) ~1,000lbs. ~5,000 lbs. 10,000 lbs. Food/day Food/day Food/day ~10 tons ~70 tons ~500 tons (1%wt.) (5% wt.) (10% wt.) manure/yr. manure/yr. manure/yr. 42lbs./hr. 208 lbs./hr 416 lbs./hr c. Overheating: did they use evaporative cooling or other forms of thermoregulation to avoid this? d. Pumping blood: would have been a challenge for the brachiosaurids (with vertically oriented necks) – did they very large 4-chambered hearts and muscular blood vessels with one-way valves to overcome this? We don’t know. 5. The advantages of being big a. Defense: easy b. Increase access to food with little energy output (because of long necks) -odd chevrons in mid-diplodocids tails may have acted as stabilizers when they reared up (for defense, mating, eating high browse?) 6. Trackways Indicate that sauropods were gregarious and suggest walking speeds of about 15 miles per hour 7. Eggs and nesting The odd sauropod egg has been found in France and Mongolia, but the best egg and nesting site is in Patagonia (Argentina, in the Upper Cretaceous Rio Negro Fm.); here many eggs, nests and embryos have been found (Argentinasaurus); these remains suggest a K-strategy (and altricial young) 8. Brains Sauropods had the smallest EQ’s of any dinosaur, despite evidence of advanced social behavior. This suggests that EQ is not a meaningful measure of behavioral complexity. 5 .