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Dinos Midterm 2

second midterm

What are 2 types of dino nests and how do they differ? -mount nests – vegetation piled up, tunnel provided • nest provides both protection & incubation through the decomp of surrounding veg • observed in modern alligators, crocs, and birds -hole nests – excavation dug into the sand
Dino nests & clutch sizes varied from 2-35 (comparable to modern birds) • R strategies – lots of offspring, little parental care, precocial (can walk & feed themselves upon birth) o titanosaurs • K strategies – few offspring, lots of parental care, altricial o oviraptor
Dino nest clutch patterns evidence that mothers repositioned eggs after laying • concentric circles: probably repositioned • spirals • parallel rows: probably not repositioned • poorly defined clusters
Dino brooding behavior and evidence -suspected in Oviraptor -Brood parasitism • nest in late cretaceous of Mongolia with embryonic remains of oviraptor and velociraptor
Dino evidence for parental care circumstantial evidence • skeletons of hatchlings around nests • bones and footprints of adult dinos of the same species • psittacosaurus on nest? • Cannibalistic species probably didn’t provide parental care (by analogy)
Height and overall size: how can they be used to reconstruct diet? -determined by analyzing the skeleton -skeletal anatomy: guide to size, shape, and configuration of muscles -also provides understanding of how dinosaurs moved
Skin impressions: what do they look like? could you recognize them? -covered with scales similar to living reptiles -known from ornithopods, theropods, and ceratopsians -some small theropods had feathers • color pigments – melanosomes • blacks, browns, reds • similar colors to mammals • link to warm bloodedness?
Dino growth and longevity: indeterminate vs. determinate growth, how to estimate dino ages -indeterminate is exponential time vs body size growth, reptiles -mammals and birds reach maturity and plateau -determinate rates 10x faster than determinate
2 ways to estimate dino weight -using skeletal dimensions -using scale models
Watching your Weight Activity Skeldem - have length, get mass from chart using line equ Scalemod - get scale & displacement from chart (convert to L), cube scale & multiply by displacement. mult that by croc density
How did carnivores attack: solitary vs. pack hunting -carnosaurs • large = solitary hunters o trex, spinosaurus, allosaurus • small = pack hunters o trackways show pack hunting -coelurosaurs • solitary hunters (insects/lizards) o very small (like microraptor) o insectasaurs, small lizards
How did carnivores defend themselves -speed • ornithopods are fastest -agility -slashing teeth & claws • theropods -dinos ate other carnivorous dinos • especially in cretaceous • big ol’ toe claw
How did herbivores defend themselves? -huge body size, whip-like tails -defensive armor • club & thagomizer -speed, camouflage, fleeing to water, or group defensive behavior
Group behavior: evidence for group behavior and herds • display structure: recognition of mates or opponents o intraspecific o interspecific mates within your own species • sexual dimorphism: recognition of males vs females, provides males with display/defense structures o larger version is the female
Footprint record: stratigraphic range, geographic distribution, why are they important? -upper Triassic to upper cretaceous -all continents except Antarctica -important info re. biostratigraphy, posture, gait, foot structure, speed, soft anatomy, social behavior -presence of dinos in places, time intervals, & enviros without body fossils.
Terminology: footprint, trackway, pace angle, etc. -footprint – result of interaction between living dino’s foot & substrate -trackway - sequence of consecutive footprints -trackway width - -stride length - -pace length -
IDing and naming footprints: how is it done/ what are the problems associated with it? -ID determined by size, shape, number of toes, and associated body fossils -digitigrade – walked on their toes (theopods, ornithopods, pachycephelasaurs) -plantigrade – put your whole foot down (sauropods, stegosaurus, ceratopsian, ankylosaurs) -therop
Trackways: interpreting social behavior -possible interpretations • herd or pack behavior • migration • predator/prey interactions
Estimating dino speed from footprints: applying the technique, how does it work? -given: footprint length (FL), stride length (SL), hip height = FL*4, relative stride = SL/HH -RS indicates behavior -speed = dimensionless speed * (HH*g)^0.5 • g = 9.81 m/s^2. DS uses graph
Walking with the Dinos activity in detail, what are the problems with this technique? Measure FL. FL*4=HH. Measure SL. SL/HH = RS. • RS<2: walking • 2<RS>2.8 trotting • RS>2.9 running Get DS using graph. Use DS to get speed. Problems: feet vary, mod analogue not gewd
Direct evidence for diet • stomach contents o occasionally preserved • corprolite = feces stone o often difficult to link to species o look at size, grooves, contents (depending on question), and associated fossils o carnivore coprolites: most common bc bone minerals help
Stomach contents: examples • hadrosaur mummies: conifer twigs & needles • sinocalliopteryx: theropods and birds • deinocherius: fish vertebrae & scales • coelophysis: lizard
Coprolites: definition, how to identify species, preservation o carnivore coprolites: most common because phosphatic minerals in bone aid preservation o king size coprolite • 44 cm long, 2L volume • linked with T rex based on size • upper cretaceous of canada
Gastroliths: definition, possible functions, how to differentiate between gastroliths and gastromyths • stomach stones o occur in many living birds & reptiles o stones swallowed and help in gizzard o must be found in chest region of more than 1 specimen to be valid • grind food & aid digestion • relieve hunger pangs • ballast while swimming
Teeth and jaws: carnivores vs. herbivore carn: many sharp serrated blade-line teeth in powerful jaws, designed to stab, tear, and slice flesh herb: flatter, leaf-shaped teeth, sometimes arranged in dental batteries, in massive jaws and skils, designed to tear, slice, pulp, or grind.
tooth morphology (enamel, dentine, root crown, serrations) -outer enamel -inner dentine -root vs crown -serrations: with septic cultures • serration is bump, cella is the indent • maybe bacterial colonies in cella -blade is a carina, then there’s the root & crown
KT extinction: When did it occur? Where did it occur? Extinction numbers: -65 Ma -KT is between meso & ceno -worldwide
KT: How large was the extinction (percentages)? What went extinct? -75% species extinct -50% genera extinct -loss of top predators -herbivores survive relatively unscathed -dead zone – 300,000 years where ocean was just kind of dead
KT: How did the extinction affect terrestrial habitats? Pre • dinosaurs • pterosaurs • angiosperms Post • angiosperms • mammals • birds
KT: Dinosaur-specific causes, problems with these hypotheses disease (no evidence for increase, infections & tumors throughout), mammals eating eggs (not only dinos laid eggs, some egglayers survived), trace element poisoning (some heavy metals, but wouldnt have an impact of that magnitude)
Where did the flood basalts occur? When? How did they form? • flood basalts in india • reunion hotspot (hotspot → laccolith → dikes) • lava pools at ocean floor • as indian plate moves, it creates a line of basalt as the moving plate passes over a constant hotspot • 67-63 Ma
3 ways that flood basalts could cause extinction. poor thermoregulation, ash formed short-term cooling, GHGs caused long term warming, magma contact
evidence against climate change as a cause of KT o not a drastic cooling event followed by a gradual warming shown in record o vegetation changes are gradual o drop in sea level is gradual
describe in detail the evidence for impact (Ir spike, shocked quartz, tektites, spherules) • huge spike in Ir • Ir can form here, but this came from space shocked qtz only from massive force Tektites are formed in the air o rocks were vaporized, and glass spherules were suspended in the air
Bolide: What are they? How did they form? Why are they evidence for impact? Where is the suspected crater? How any other space junk forms • bolide impact evidence o chicxulub • 180 km diameter • supposed bolide was ~15 km • explosion ~100 million H bombs • on the yucatan peninsula, trough shown around center
Traditional vs. modern view of dinosaur thermoregulation Trad is cold blooded, Modern is like possibly some were endotherms
warm vs. cold blooded • ectothermic poikilotherms: lizards • endothermic poikilotherms: hummingbirds, bats • endothermic homeotherms: humans • ectothermic homeotherms: monitor lizard, komodo dragon
ectotherm vs. endotherm -ectotherm – regulate temperature using external sources -endotherm – regulate temperature internally
poikilotherm vs. homeotherm -poikilotherms – experience fluctuating temps -homeotherms – experience stable temps
Pros and cons of endothermy: including graph Graph?? -Pro: O2 consumption & energy output of endo is greater than exto • Endos are capable of higher sustained activity levels -con: endos more costly in terms of energy use (10-30x) • limited source of energy can support fewer endo
Heated debate: upright posture & long legs/bipedalsim -upright posture – only found in dinos, birds, and mammals (en) • when your lungs aren’t involved in walking, youre more energy efficient -long legs & bipedalism – more common in endotherms (some en) • long legs
Know ONE of trex reading in detail, including the research goal or question, data collected, study organism, study time interval, and results. Also need to know the evidence presented in this paper: for and against predation; for and against scavenging Hadrosaur caudal vert CT scans. Toothcrown in healedbonegrowth suggests it survived pursuit predation. Against was too slow, large olf lobes.
Debate: be able to explain (in detail) at least three pieces evidence for pro predation • Bigger skull = bigger mouth/stronger bite, so you don’t need your forelimbs • Predator prey body mass ratio (same as modern analogs) • Large body size (no modern scavengers who are that big) • Failed attacks in fossil record
Debate: be able to explain (in detail) at least three pieces evidence for anti predation • Slow running speed (some prey were faster) • Small forelimbs (can’t grasp prey like modern predators) • Vulnerable skulls at high velocities (if it was running & couldn’t slow down)
Debate: be able to explain (in detail) at least three pieces evidence for pro scavenging • Ecological models suggest that environment could have supported a large scavenger (energy available) • Presence of trex teeth at mass death sites. So suggests that carcasses were already available • Large olfactory lobes
Debate: be able to explain (in detail) at least three pieces evidence for anti-scavenging • You don’t need forelimbs to be a scavenger • Metabolic rate was high for a scavenger • Greater abundance of small theropods – would outcompete them, were faster
Dinosaur phylogeny: Be familiar with the evolutionary tree for the major lineages (see Lecture 3-23,, Slide 2), in particular who is related to whom and how. Theropods & Sauropods. Ank & Steg. Cera & Pachy. Ornithopods.
Stegosaurs: what does the name mean, when did they occur (stratigraphic range), where did they occur (geographic range) -thyreophora (armor-bearing) -stegosauria (roof) • Jurassic – early Cretaceous • occurred in N America, Europe, China, Africa
Stegosaurs: were they quadrupedal or bipedal, diet, what trace fossils are known o obligate quadrupeds o no ossified tendons. herbivores • trackways (western US) o 3 toes on forelimbs, 5 toes on hindlimbs o splayed toe angle • no eggs or nests
Stegosaurs: evolutionary novelties of Thyreophorans • extensive covering of bony plates set in skin • >1 parallel rows of osteroderm (parasagittal) plates o skin bone – not connected to weight-bearing bones of the skeleton. Grow in plates from skin o they go from head to toe
Stegosaurs: possible functions of plates, how to test these functions, could you identify them based on skeleton and life reconstructions • Protection? • Peer recognition o Size & shape varies within a pop o Multiple species rarely found in same basin • Thermoreg o positioning of plates, vascularization, biomechanical experiments o Assumption that they are ectothermic
Ankylosaurs: what does the name mean, when did they occur (stratigraphic range), where did they occur (geographic range) Ankylosauria (“Fused”) -early Jurassic-late cretaceous -all continents except Africa
Ankylosaurs: were they quadrupedal or bipedal, diet, what trace fossils are known quadrupedal herbivores -trackway discovered in Bolivia • only one. • Mostly we have body fossils of skulls, body armor, and a couple of tail clubs -no eggs or nests discovered
Ankylosaurs: evolutionary novelties of Ankylosauria -closure of antorbital and upper temporal fenestrae -fusion of first tail vertebrae to sacral vertebrae -rotation of ilium to form flaring blades -development of dorsal shield of symmetrically placed bony plates and spines • osteoderm armor
Arbour article including her research question, what data she collected, and what conclusions she made about tail club function; could you identify ankylosaurs based on skeleton and life reconstructions Q: max force of club, could it harm (defensive?) D: CT scans of anterior, muscle attachments, bone density C: Not exclusively defensive, maybs competition, no up&down, knob denser on outside than in
weight reconstruction using skeletal dimensions • measure length, circumference, cross-sectional area, etc. of bones & use it to estimate weight • based on positive relationships between skeletal dimensions and weight in living vertebrates
weight reconstruction using scale models • build model of known scale (1/50 length) • calculate vol via displacement of water • scale vol up to size of actual dinosaur • use density of living crocodile (0.9 kg/L) to convert to kg • possible problems? o Dinosaur bones less dense (like birds)
Group behavior: evidence for group behavior and herds 2 • shape change growth: recognition of juveniles o big eyes, hands, feet • Mass death assemblages: not enviro accumulation • Parental care o Flock behavior or herd behavior • Trackways: multiple trackways of same dino, direction, speed, layer
Trackways: possible interpretations • consider footprint size and shape during development • substratum (type, water content, cohesiveness) • speed and gait
Trackways: how are hypotheses tested -hypotheses must be tested by estimating the speeds of the tracks
Indirect evidence for diet • stomach stones (gastroliths) • teeth & jaws • height & overall size
How did the extinction affect marine habitats? Pre • plesiosaurs • ichthyosaurs • mosasaurs • ammonites • rudists • clams • snails • urchins • crustaceans Post • clams • snails • urchins • crustaceans • fish • corals
Heated debate: digestion, feathers -digestion – evidence for complex food processing and secondary palates in some dinos (some en) • secondary palate lets you breathe while you eat -presence of feathers – similar to birds (some en)
Heated debate: heart & circ, brains -heart & circ – evidence for 4-chambered <3? (en) -brains – large brains in some dinos (some en)
Heated debate: nasal adaptations (turbinates) -lack respiratory turbinates (ec) • dinos don’t have these, so they’re not super efficient respirators
Heated debate: Behavioral evidence -parental care – more common in endotherms (en)
Heated debate: Histological & growth evidence -growth rates – more similar to birds than reptiles (en)
Heated debate: Other evidence -predator-prey ratios – similar to endothermic? (en?) • endotherm as top predator means they need a lot of prey • ratios are limited by preservation • modern ratios based on sketchy examples (like spiders)
Stegosaurs: evolutionary novelties of Stegosauria, thagomizer • back vert w/tall neural arches & highly angled transverse processes • loss of ossified tendons down back and tail • broad & plate-like process in shoulder area • large & block-like wrist bones, helped digitigrade posture
How to figure out what steg plates were for • How do you figure this out? o What types of predators were around and how did they hunt o What is the relationship between plate surface area and paleolatitude? o What is the variation in shape and size and would it be enough
Ankylosaurs: possible functions of tail club, how to test these functions -not for display • not vascularized • not in the front of the body where all the other display stuff usually is • but we don’t know if it was making contact with predators or just intimidating them
Ankylosaurs: how to test tail club functions -CT scans of the anterior structure -wanted to see where muscle would attach, how the tail would move -looked at bone density (first person to look at that in tail clubs) -wanted further studies to look at rib damage
Issues with watching ur weight Birds are bipedal, but many dinosaurs (e.g., stegosaurs, ankylosaurs, sauropods) are quadrupedal. Birds have hollow bones, but many dinosaurs (e.g., non-theropods) don’t Many dinosaurs (e.g., stegosaurs, ankylosaurs) have bony armor, but birds don’t
Created by: haleyBUGoxox