dinosaurs final

what are the two types of fossils?

body and trace

example of a body fossil

bone

example of a trace fossil

footprints

why is the dinosaur record so bad?

dinosaurs were terrestrial, therefore their fossils were not preserved as well as subigneous organisms

absolute dating

actual numerical age

relative dating

comparison between two aged things

what types of rocks are used for absolute dating?

igneous

law of superposition

relative ages; oldest rock is at the bottom, youngest is at the top

parts of the mesozoic from oldest to youngest

triassic, jurassic, cretaceous

point of evidence for plate tectonics

the continents fit together almost perfectly, especially south america and africa

paleomagnetism

magnetic fields cause reverse polarity, making pattern of rock across ocean ridges

what defines the chordates as a clade?

they possess a notochord, a dorsal nerve cord

what defines the tetrapoda as a clade?

1. adaptation to live on land and facilitate locomotion (legs, four digits on feet, etc)
2. amniotic egg

what is the defining character of amniotes?

amniotic egg, allowing for the laying of eggs on land and independently of water

why are amniotic eggs important in an evolutionary sense?

they allowed the early amniotes to become more independent of the water and eventually led to full independence from water.

fenestrae

holes in the skull

why are fenestrae important?

increase the area and improve alignments for attachment of muscles, leading to stronger muscle attachments and a lighter skull

anapsid

no holes in the head

example of an anapsid

turtle

synapsid

one hole in the skull

example of synapsid

humans and all mammals

diapsid

two holes in the skull

example of diapsid

dinosauria

what clade is the ancestor to crocodiles, dinosaurs, and pterosaurs?

archosauria

are pterosaurs part of dinosauria?

no

are pterosaurs part of archosauria?

yes

carrier’s constraint

inability to run and breath at the same time in a sprawling stance

how did dinosaurs get around carrier’s constraint?

development of an erect stance

open acetabulum

hole in the hip

what caused the open acetabulum?

erect stance

what is the defining character of dinosaurs?

open acetabulum

what are the two groups of dinosaurs?

ornithischian and saurischian

which group of dinosaurs has a rear-facing pubis?

ornithischian

which group of dinosaurs has a front-facing pubis?

saurischian

when did dinosaurs first appear?

around 228 mya

pelvis of…

ornithischian pelvis

pelvis of…

saurischian pelvis

how did the end triassic mass extinction benefit the dinosaurs?

opened ecological niches, allowing dinosaurs to become dominant over synapsids and archosaurs and more well adapted

what is the main feature that defines the saurischians as a group?

front-facing pubis

another defining feature of saurischians

hinge of jaw is on one plane, scissor-like

what is sexual dimorphism?

male and female of a species have distinguishing and different features including size and appearance

what are pneumatic bones?

light bones, connected to the respiratory system

what were pneumatic bones used for?

moving faster and reducing energy spent when moving

were theropods bipedal or quadripedal?

obligate bipeds

what is unique about theropod hands?

large and grasping, made of low-density bones

what do theropod teeth and jaw structure suggest?

that they were meat-eaters; for slicing NOT chewing

theropod teeth were…

curved, pointed, and serrated

theropod jaw was…

scissor-like

what do orinthomimsaurs and oviraptors have in common?

no teeth

what is the encephalization quotient?

brain-mass to body-mass ratio

what do we know about the senses of theropods?

they had strong vision, large eyes, and enlarged ear cavity

did dinosaurs lay eggs or live birth?

layed eggs

what would be convincing evidence for pack hunting in theropods?

small dinosaur skeletons found near large ones, seeing as they couldn’t have taken down a large dinosaur alone

what do fossils found in hunting/fighting positions suggest?

pack hunting

what helped us determine what theropods ate?

gut contents, jaw structure, teeth structure, tooth marks on prey

what are gastroliths?

trace fossils of stomach stones

were feathers common or uncommon in theropods?

common

evidence of t-rex predation

* healed bite wounds
* pointy teeth
* strong teeth
* bite force very strong
* not that slow
* large olfactory

evidence of t-rex scavenging

* large olfactory
* small arms
* small optic nerve
* poor eyesight
* femur/tibia similar - slow
* teeth in bone beds

what is science?

a reliable method for learning about the natural world.

* must be testable and repeatable
* never prove anything
* used all the time

What as the climate like during the jurassic?

* no polar ice caps
* high sea level
* warm, equitable climates
* less seasonality due to high global sea levels

climate indicators:

* stable isotopes, tropical vegetation in polar regions

what was the climate like during the cretaceous?

1st half:

* warm equitable; polar free of ice
* global tectonic activity
* higher sea level
* oceanic spreading

2nd half:

* deterioration of equitable climate
* high seasonslity
* polar to equator gradient much like today

how is climate different than weather?

climate is the analysis of weather conditions/patterns over time in a specific area, while weather is only a short period of time.

how did CO2 levels compare to today? should we be worried?

fluctuated but were generally higher than they are today. our levels are increasing at a much higher rate due to climate change, and we should be concerned about the human effects.

did darwin propose evolution? what did he do?

not the first person to propose evolution, but he discussed it at length, proposing it and natural selection and adding decent with modification he helped it to be understood better.

define cladistics

modern way to organize life based on shared characters

what are used to make cladograms?

characters

character

an isolated feature of an organism that is distributed among a group of organisms

what are the two types of characters?

derived and primitive

derived characters

specific; diagnostic of smaller groups

primitive characters

ancestral; general; distinguishes larger groups

_____ anatomical structures that can be traced back to a single structure in a common ancestor.

homologues

what is convergent evolution?

similar characters evolve separately in two independent lineages; can be adaptions to similar environments

why are transitional fossils important?

help “bridge gaps” and explain better ancestry between organisms; can help explain evolution and its process

what are a few features that make cynodonts a transitional fossil between reptiles and animals?

2 jaw hinges, erect hind limbs/sprawling front limbs, and partially developed 2nd palate

what are the two groups of dinosaurs?

saurischian and ornithischian

how do we differentiate between the two groups of dinosaurs?

pubis direction

* saurischian: forward facing
* ornithischian: rear facing

what are two features that all ornithischians share?

predentary bone and rear-facing pubis

what is the reason behind a posterior facing pubis?

to make room for the large gut cavity needed to digest plant matter

what is the feature shared by genasauria?

muscular cheeks

name the five main members of the ornithischian

stegosaurs, ankylosaurs, ornithopods, pachycephalosaurs, and ceratopsians

what feature is necessary for chewing?

cheeks

what do ornithischians eat?

plant matter

which group of ornithischian was likely the best at eating?

ornithopods due to pluerokinesis and dental battery

what is pluerokinesis?

complex muscle jointing that allowed more movement in jaw for chewing; top jaw is mobilized

what group was likely the worst at eating?

stegosaurus or ankylosaurus due to weak, small teeth and extensive need for fermentation due to body size

what is the shared character of thyreophora?

osteoderms (bone embedded in the skin)

what are the two members of thyreophora?

stegosaurus and ankylosaurus

what does stegosaurus posture suggest about movement and feeding?

very slow due to long back legs and short front legs; too slow to chase prey, meaning that they were low-grazing herbivores

what is the main benefit of having a large gut cavity?

easier digestion of plant matter

did stegosaurs have a second brain?

it was once thought that they did because the sacrum was enlarged, but they do not.

what is the likely function of stegosaur spines? plates?

defense, display (intra- and interspecific) and thermoregulation

what are some lines of evidence that support stegosaur plates for defense?

* spikes on tail could wack a predator
* most likely hard structures; could take blunt force

what are some lines of evidence that support stegosaur plates for display?

* species specification: difference among species
* large plates = intimidate predators

what are some lines of evidence that support stegosaur plates for thermoregulation?

* blood vessels in the plates

what do we know about ankylosaur feeding based on hyoid bone, teeth, and large gut?

herbivores due to low head, tooth wear, gut for fermentation, etc.

what modern day animal has an enlarged hyoid bone analogous to that of the ankylosaur, and what does this allow for?

giraffe; long, flexible tongue

can we assume ankylosaurs were fast moving and nimble? why or why not?

no; due to round/broad body shape, smaller flocculus, etc. they were all about defense, not speed

at what time were stegosaurs most abundant? ankylosaurs?

stegosaurs: jurassic

ankylosaurs: cretaceous

what two forms of protection did ankylosaurs have against predation? are there any lines of evidence that would support that these functioned as protection?

* tail club
* force generated by club tail confirm use
* armor (osteoderms)
* biomechanics confirm durability