Age of Dinosaurs Exam 2

indeterminate growth

growth slows down over time (reptiles), usually ectothermic

determinate growth

reach adulthood and stop growing (birds and mammals), usually endothermic

estimating dino ages

using growth series, bone growth lines

skin impressions (dinos?)

• usually look somewhat scaly or uniform in pattern with circular indentations

• known from ornithopods, theropods, and ceratopsians

  • some have scales other have feathers/feather-like

dino eggs (oldest known, material, shape, size, dinos)

oldest known eggs: late triassic

early dinos: soft-shelled

later: organic matter, crystalline calcite (CaCO3)

could be spherical, oblate spheroid, semiconical, prolate spheroid

ranges from 3cm to 30 cm

eggs well known from theropods, prosauropods, sauropods, ceratopsians, ornithopods

egg microstructure

inner organic: eisospherite layer

external crystalline: exospherite layer

• mammillary layer (most inner), column layer, cuticle layer (most outer)

pore conductance in dino eggs

8-16x faster than birds

eggs laid in a low O2 environment, high CO2, and high H2O environment (burying eggs or covering them with vegetation)

rotting vegetation provides extra incubation for eggs (need for ventilation in order to get air underneath vegetation)

ID dino eggs

eggs contain embryos

are closely associated with hatchlings or adults

mound nests

nest provides both protection and incubation through the decomposition of surrounding vegetation

decreases oxygen supply so increased pores of eggs to take in more oxygen

observed in modern alligators, crocs, birds

hole nests

excavation into sand

clutch size

2-35 (comparable to birds)

R selected nests

many eggs

no parental care

hole nests

ex: sauropods

K selected nests

fewer eggs

parental care

mound nests

ex: ornithopods

parental care evidence:

skeletons of hatchlings around nests

bones/footprints of adult dinos of same species

brooding behavior (oviraptor, psittacosaurus) sit the same way modern birds do

direct evidence for diet

stomach contents

dung

indirect evidence for diet

stomach stones

teeth and jaws

height and overall size

stomach contents

hardosaur mummies: conifer twigs and needles (have tooth battery to break down)

sinocalliopteryx: theropods and birds

dienocheirus: fish vertebrae and scales

coelophysis: lizard

coprolites

feces stone

difficult to link to species: look at size grooves, contents, and associated fossils

carnivore coprolites most common because phosphatic minerals in bone aid preservation

gastroliths

stomach stones that are swallowed and held in gizzard

function

• grind food and aid in digestion

• relieve hunger pangs

• serve as ballast while swimming (to make them sink): modern crocs and alligators

must be found in chest region for more than one specimen to be considered valid

carnivore teeth

numerous sharp serrated blade-like teeth in powerful jaws, designed to stab, tear, and slice flesh

velociraptor: recurved and oval cross-section for slicing

t-rex: less/not recurved and circular cross-section for crushing

herbivore teeth

flatter, leaf-shaped teeth, sometimes arranged in dental barriers, massive jaws and skulls

designed to tear, slice, pulp, or grind

footprint record (when, where, important)

• upper triassic to upper cretaceous

• all continents except antarctica

• important: provide information about posture, gait, foot structure, speed, soft anatomy, and social behavior

footprint

results from interaction between living dino’s foot and substrate upon which it walked

trackway

sequence of consecutive footprints

pace angle

measurement to determine gait or posture (angle between left and right footprints)

trackways (interpretation, hypotheses)

interpretations:

• migration

• predator/prey interactions

• herd or pack behavior: multiple trackways of the same dinosaur, in the same direction, at the same speed, in the same layer

hypotheses: must be tested by estimating the speeds and spacing of tracks

group behavior evidence

trackways: multiple trackways of the same dinosaur, in the same direction, at the same speed, in the same layer

mass death assemblages: must be differentiated from environmental accumulation

parental care

display structures: recognition of mates or opponents

gender dimorphism: recognition of males vs. females, provides males with display/defense structures

change in shape during growth: recognition of juveniles vs. adults

ectotherm

regulate temperature using external sources

endotherm

regulate temperature internally

poikilotherm

fluctuating temperatures

homeotherms

stable temperatures

pros and cons of endothermy

pros: oxygen consumption and energy output of endotherms is greater than ectotherms (higher levels of activity of activity sustained)

cons: endothermy much more costly in terms of energy use than ectothermy (depends on life habits/environment if its worth it)

solid line: endotherms

ectotherms: dotted line

evolutionary tree for major lineages

stegosaurs (name, pedal, diet, fossils)

• roof lizard

• quadrupedal

• herbivore

• trace fossils: trackways of adults and babies, no eggs or nests (leathery eggs?)

Ankylosaur (name, pedal, diet, fossils)

• fused lizard

• quadrupedal

• herbivore

• trace fossils

  • trackways from N and S america, europe, asia

  • hatchlings, but no nest or eggs

arbour (research question, organism, data, conclusion)

research questions: the goal of this study was to reconstruct tail club function in ankylosaurs through the use of bone descriptions, CT scans of clubs, muscle reconstructions and math modeling

organism: dyplosaurus, eupophealus

data she collected: muscle mass and bone mass using CT imaging, calculated inertia, cross-sectional area, vertical flexibility and angle of tail swing

conclusions:

• move 100 degrees laterally

• larger tail clubs could break bone

• tail swinging behavior is feasible, but unclear whether it was used for defense against predators, combat within the same species, or both

pachycephalosaurus (name, pedal, diet, fossils)

thick head

bipedal

herbivore and omnivore

trace fossils: none known! majority of specimens are cranial only

ceratopsians (name, pedal, diet, fossils)

horned face

bipedal/quadrupedal

herbivore

trace fossils: nests, eggs, and embryos, and trackways

griffin (origin, region/people, evidence, protoceratops vs. griffin)

• explanation of origin: ancient people mistook fossils for mythical beasts

• region and people: saka-scythian nomads told the greeks (800 BC)

• supporting evidence:

  • historical: including writing by Greek authors that describe griffin as an actual animal, as opposed to being associated with a god or with supernatural powers

  • archaeological: including Scythian mummies that show tattoos of griffins that predate greek writings; also ceramics that provide illustration of griffins that can be compared to protoceratops

  • geological: including fact that protoceratops skeletons and nests occur in the same geographic area as gold and the scythian peoples

• similarities and differences between protoceratops and griffin

  • similarities curved beak, nests, shoulder blade (mistaken for wing), broken frill (mistaken for ears)

  • difference: talons (no sharp, curved claws in protoceratops)

dinosaur color

melanosome: pigments that determine color

important: certain colors more likely to be preserved, confirm different colors or feathers of certain dinos (countershading and camouflage)

found in: microraptor, psittacosaurus (a ceratopsian)

predation evidence for T-rex

o   Speed: t-rex were slower, but larger metatarsals than prey and fast enough to catch them (use tail to propel) – why have an adaptation for speed if they’re only scavenging

o   Catching dinner: evidence of failed predation attempts on duck-billed dinosaurs (healed bite marks on fossils suggesting they were attacked by a t-rex and survived)

o   Strong arms: stress fractures present on the arms so t-rex could have grappled with prey with its arms

scavenging evidence of t-rex

olfactory lobes of t-rex are really enlarged in tyrannosaurs

testing hypotheses of feeding behavior in t-rex:

compare most similar current environment to the cretaceous and how much prey on average the t-rex would be able to scavenge and do mathematical analysis for whether that would be able to sustain them

use physics and mathematical models to estimate the speed t-rex can reach and compare it with its prey

ID footprints

determined by size, shape, number of toes, substrate, and associated body fossils (footprints get their own names)

problems: many footprints cannot be matched to dinos

ectothermy evidence

o Nasal adaptations: lack respiratory turbinates (thin bones in nasal cavity designed for reducing moisture/heat loss) absent in current ectotherms

o Growth rings in teeth: similar to crocodiles (crocodiles are ectothermic and hints at the inability to regulate their temperature on their own)

endothermy evidence

o Upright posture: only found in dinos, birds and mammals (linked to modern endotherms)

o Presence of feathers: similar to birds (linked with modern endotherms)

o Locomotion: running activity in bipedal dinosaurs (endotherms can sustain longer/harder levels of activity)

o Parental care: more common in endotherms (parental care requires lots of energy, that ecotherms don’t have)

o Metabolic chemistry: oxygen byproducts (oxygen consumption higher in endotherms)

endothermic dinos

theropods followed by ornithopods

long legs, bipedalism, feathers (in theropods), running, locomotion, parental care, and large EQ both of these groups have which are all endothermic evidence

how to test endothermic v. ectothermic

o   En: look at trackways and bone structure to see if upright posture

o   Ec: look at growth rings in teeth

o   En: testing for presence oxygen byproducts in bone

walking with dinos (estimating dino speed based on trackway)

Problems: guy who did the study gave a random group of animals (humans have completely different hip structure), did not calculate the equation of the line and calculated with eyeball line (stride length to DS)

ceratopsian special (function, how to test)

function of frills:

• defense

• display for sexual selection

how to test:

• compare skeletons and see if frills only develop in adults (display)

• 3D digitization or CAT scans to reconstruct muscle

identify: large horns on face (brows, nostrils, top of frills), frills on top of head

pachycephalosaurs special (function, evidence)

function of thickened skull:

• head butting, intraspecific competition, interspecific defense, sexual dimorphism

evidence for it:

• head butting/defense: 22% of domes have lesions consistent with bone infection

• some argued it was for species recognition, disproven later

identify: big dome and horns surrounding it, bipedal

ankylosaur special (function, how to test)

• functions of tail club: defense against predators, combat within species

• how to test functions: muscle reconstruction, mathematical modeling to see what force it would withstand/exert

• identify: dermal armor, wide and flat bodied, shaped like a flattened soda can

stegosaur special (function, how to test)

• thagomizer: tail spikes (used for defense against predators or offense when being territorial or protecting eggs)

• function of plates

  • protection: armor

  • peer recognition: mating displays, sexual dimorphism

  • thermoregulation: maintain thermoregulation of stegosaurs (heavily vascularized)

• how to test functions:

  • thermoregulation: experimental model for how fast a surface heats or cools downs

  • display: compare plate size and shape of adult and juvenile fossils

• how to identify: thagomizer and plates on spine

stegosaur novelties

• large and block-like wrist bones

• no bony tendons down back and tail (flexible)

• ridge of bone that sticks out near the scapula

ankylosaur novelties

• tail vertebrae fused to hip vertebrae and hip bone

• development of shield along their back of symmetrically placed bony plates and spines

• closure of antorbital and upper temporal fenestrae

ceratopsian novelties

• larger premaxilla

• widely flared cheekbones

• rostral bone in skull

pachycephalosaur novelties

• thickened skull roof

• longer hip ribs

• bony tendon in the tail

ectothermic dinos

sauropods, ankylosaurs

quadrupedal, no feathers, slow-moving

testing hypotheses (general)

-       Using modern analogs to compare

-       CT scanning (looking at internal structures)

-       3D for external structures

-       Mathematical models

-       Look for damage on dinosaur or their competitors/predators

stegosaur: where and when

• mid jurassic → early cretaceous

• northern and southern americas, europe, asia, africa, australia

ankylosaur: where and when

• mid jurassic to late cretaceous

• all continents

ceratopsian: where and when

late jurassic to cretaceous

north america, europe, asia

pachycephalosaur: where and when

early to late cretacoues

north america and asia