Dinosaurs Final Exam Study Guide !!

Allometry

Different parts of the body grow at different rates; Ex: puppies paws are very large in comparison to the rest of the body, but over time the body grows into them

Amniote

Evolutionary Novelties:

1. Amniotic Egg

2. Internal fertilization

3. Waterproof skin

4. Complex lungs

Synapsids and Reptiles in this group

Anapsid

a skull condition with no temporal fenestrae. This is an ancestral condition (i.e., early tetrapods and early amniotes were

Ankylosaurians

A type of Thyreophoran; “Fused lizards”; Dorsal Shield (Fused dermal bone, Symmetrically arranged into bony plates and spines, Not just on head!); Large size & Quadrupedal; Stout limbs; Broad hands; Stubby fingers

Nodosaurid

many had huge parascapular spines; a type of Ankylosaurian

Ankylosaurid

Evolutionary Novelties:

1. Skulls with horns

2. Clubbed tail

Antorbital fenestra

Archosaur evolutionary novelty; a hole in the front part of the skull, just anterior of the eye. Hole in front of eye socket.

Archaeopteryx

First specimen discovered in 1860/1861. Given a name that means “ancient feather/wing.” Has teeth, a long bony tail, and unfused fingers (different from modern birds). Has relatively long arms with large asymmetric feathers, possibly for powered flight (similar to modern birds).

Archosaur

Evolutionary Novelties:

1. Thecodonty

2. Antiorbital fenestrae

3. Mandibular fenestrae

4. Parental care

Types: Crocodiles & kin, Pterosaurs, Dinosaurs (& birds)

Aves

The most recent common ancestor of all living birds (also includes many extinct forms). Both fossils and DNA suggest that this group first appeared during Late Cretaceous. Novelty: no teeth; group explodes in diversity during the Cenozoic, after the K-Pg mass extinction. Includes Paleognaths and Neognaths

Avialae

May be defined by flapping wings (powered flight); Basically includes Archaeopteryx through modern birds; also have complex asymmetrical feathers, eggs laid sequentially, and an enlarged fore-brain.

Bacterial Body Fossil

single celled organisms that were preserved. Some of the oldest clear evidence of life. 3.5 billion years old (3,500 million)

Brachiosaurus

“Arm lizard;” Late Jurassic, Western n. America, ~13 m tall, ~25 m long; Not the largest sauropod, but among the largest known from relatively complete skeletons; Stance suggest that neck was often held up high (note size of front legs). A sauropod.

Cerapoda

Includes Marginocephalians (Ceratopsians + Pachycephalosaurids) and Ornithopods (Hadrosaurids and relatives)

Evolutionary Novelty: Diastema (gap between front and back teeth, specialization for herbivory)

Ceratopsians

“Horned faces;” Evolutionary novelty: Rostral bone; a category of Marginocephalians

Ceratopsid + Protoceratopsid novelties

1. Frill

2. Dental Batteries

3. Quadrupedal

Ceratopsids

Evolutionary Novelty: Horns (on their skulls)

Ex: Triceratops, Styracosaurus, Centrosaurus

Ceratosaurs

“horned lizard;” Jurassic and Cretaceous; a Theropod

Coelacanth

A fleshy-limbed vertebrate (Sarcopterygii); were thought to be extinct after the Mesozoic (fossils disappeared in the record after that period) but were found out to be still alive in the 1930s

Coelophysis

~216 Ma, Late Triassic; approximates the general body form of the ancestral dinosaur (small-bodied biped); carnivorous.

Coelurosaurs

Evolutionary Novelty: Simple feathers

A type of Tetanuran; includes Tyrannosauroids, Compsognathids, Ornithomimids, and Maniraptors.

Convergent Features

similarities not inherited from a common ancestor (independently acquired); The most recent common ancestor that 2 specimens share did not have this shared characteristic. Ex: Birds and bats both have wings, but their shared common ancestor did not.

Homologous Features

similar because they were inherited from a common ancestor; characters that are fundamentally the same biologically

Crocs & kin

Crocodiles, Alligators, Caimans, and Gharials; a type of Archosaurs; have some huge (30-50 ft) extinct ancestors

Darwin’s contributions to the theory
of evolution

• Common Descent with Modification

• Natural selection

argued that life is all related; acquired characteristics aren’t passed down but surviving traits are passed down

Common Descent with Modification

All living organisms are related, descending from a single common ancestor; traits change over time due to natural selection

Dermal Armor

Bone within skin; Become scutes/osteoderms, and spikes in Ankylosaurians; Become plates or spikes in Stegosaurians

Lung complexity in amniotes

Amniotes had more oxygen requirements than earlier tetrapods because they were more active (better adapted to land), so they developed more complex lungs

Development of limbs

Osteichthyes (“bony fish”): ray-finned “fish” and fleshy-limbed vertebrates. Fleshy-limbed vertebrates → tetrapods (over time)

Bones of fleshy-limbed vertebrates

Flesh and muscle at the base of their limbs (fins); covers bones

Diapsid

2 pairs of temporal fenestrae

Diastema

gap between front & back teeth; specialization for herbivory

Deinonychus

Early Cretaceous, United States; a type of Dromaeosaurid (aka “Fast-running lizards” or ‘raptors’)

Dromaeosaurids

“fast-running lizards” aka raptors

Late Jurassic to End Cretaceous; diverse and worldwide

Includes Utahraptor, Deinonychus, Velociraptor

Dinosauria

Groups: Theropods, Sauropodomorphs, Ornithischians

Novelties: Erect posture & narrow tracked gait, Opening hip socket bordered by bony upper ridge, Upright Femur, Femur with inturned head

Ancestrally small and bipedal, some species became large and quadrupedal

Diplodocids

A type of Sauropodomorph, includes: Diplodocus (Late Jurassic, N. America), Amargasaurus (Early Cretaceous, Argentina), and Apatosaurus (Late Jurassic, incorrectly known as Brontosaurus)

Dorsal Shield

Fused dermal bone symmetrically arranged into bony plates and spines; not just on head. An Ankylosaurian evolutionary novelty.

Endosymbiosis theory

how organisms went from prokaryotes to eukaryotes; Aerobic bacteria became incorporated into an ancestral eukaryotic cell, becoming the mitochondria. at the same time, photosynthetic bacterium was engulfed in these protoeukaryotes and they became the chloroplasts

End Cretaceous (K-Pg) extinction

• The 5th most severe extinction

• Worldwide

• The best studied mass extinction

• Usually focus is on dinosaurs

• Extinctions on land and oceans

• Causation Hypothesis: Extraterrestrial impact (worldwide iridium spike, tektites, shocked quartz, tsunami deposits, Chicxulub crater)

End-Permian Extinction

~250 Ma

• Earth’s most severe extinction event

• ~80% of all marine species went extinct!

• ~70% of all terrestrial vertebrate species became extinct!

• ~10-30 million years for recovery of global diversity

• Likely caused by the formation of Pangea and Volcanic Eruptions

Eukaryote

organism with an advanced cell structure, including a nucleus, organelles (like the mitochondria) and chloroplasts (where photosynthesis takes place)

include plants and animals; evolved via endosymbiosis

Falsifiability

Hypotheses and the predictions scientists make must be vulnerable to being proven wrong.

First definitive fossils

Fossil Stromatolites, Bacterial body fossils (sulphate reducers?)

Fossil Stromatolites

Layered colonial structures or rocks; Formed in shallow waters as microorganisms (cyanobacteria)

trap sediment → microbial mats!

preserved from 3.5 billion years ago

“Fleshy-Limbed” vertebrates (Sarcopterygii)

They have flesh and muscle at the bases of their limbs/fins; Bones enveloped in clumps of muscles; a sub-group developed arms, legs, and digits and moved to live on land (tetrapods)

Foundations of scientific thinking

Scientific method (Observe, Hypothesize, Predict, Test Predictions), Falsifiability, Scientific Theory (an explanation that has been tested again and again and again but hasn’t been falsified)

Geologic Time Scale

Precambrian (4500 Ma - 540 Ma)

Phanerozoic (540 Ma - Present):

• Paleozoic (540 Ma - 250 Ma)

• Mesozoic (250 Ma - 65 Ma):

• Cenozoic (65 Ma - Present)

Mesozoic (250 Ma - 65 Ma):

• Triassic (250 Ma - 200 Ma)

• Jurassic (200 Ma - 145 Ma)

• Cretaceous (145 Ma - 65 Ma)

Gnathostome

Vertebrates with jaws; “Jaw Mouths”

Half-life

the time required for one-half of the radioactive parent (unstable radioactive isotope) in a sample to decay into its daughter product (isotopes resulting from the decay of a parent)

Herrerasaurus

Among the oldest dinosaurs known from relatively complete material; small (2-3 m long) and bipedal

uncertain if its a theropod or an early relative of sauropodomorphs

Ichthyosaurs

“fish lizards”; First known from Early Triassic; dominant in Jurassic; go extinct in the mid Cretaceous; some are among the largest animals that ever existed. Some species grow to ~70 feet long! discovered by long under-acknowledged paleontological pioneer, Mary Anning.

Iguanodontids

Novelty: Loss of upper front teeth (shared with Hadrosaurids); a member of this group was the second dinosaur ever named; our understanding of it shifted over time; it’s an Ornithopod

Ischium

Back part of the dinosaur hip/pelvis structure (brown)

Ilium

Top part of the dinosaur hip/pelvis structure (red)

Pubis

Front part of the dinosaur hip/pelvis structure (orange); points forward ancestrally but points backwards (reverse) in Ornithischians and birds (convergent)

Isometric growth

proportions stay the same, animal just gets bigger over time; opposite of Allometry

Isotope

variants of the same element that have different numbers of neutrons. Two types: stable and unstable (break down over time)

Last common ancestor

represented by nodes (where two branches join) on cladograms. this is the most recent ancestor of groups before they split.

Lesothosaurus

~200 Ma; Ornithischian; small (~1m long); bipedal; good representative of early dinosaurs (small bipeds); Has a leaf-shaped tooth (characteristic of early ornithischians)

Mandibular fenestra

a hole in the lower jaw

Maniraptors

Evolutionary Novelties: Semi-lunate carpal (carpus), reverse pubis

Birds fall under this group

Ex: Therizinosaurians

Mammalia

Monotremes, Marsupials, Placentals

Monotremes

Egg-laying mammals, 15 species.

Marsupials

Most of development takes place in the pouch, ~350 species

Placentals

Young born after long gestation, ~4000 species

Marginocephalians

Novelty: shelf along back of skull

Includes Pachycephalosaurids and Ceratopsians

Milk

The ancestors of mammals, small-bodied endotherms, faced a SA/V “problem,” that was solved by hair and this.

Mammals produce this to feed their young as they require a lot of food in comparison to their body size to stay warm.

Mosasaurs

Common at the end of the Cretaceous: Ichthyosaurs had become extinct and plesiosaurs were declining, so they filled the ecological vacuum.

Become extinct end Cretaceous (Mass extinction).

A type of lizard, some ~60 ft in length

Natural selection

Components:

• Variation in a species

• Differential survival and reproduction

• Heritability of Variation

A mechanism that explains evolution.

Ornithischia

Evolutionary Novelties:

1. Reverse pubis

2. Predentary Bone

3. Low Jaw Joint

Groups:

• Thyreophorans

• Cerapods

Ornithodira

Dinosaurs and Pterosaurs

Evolutionary Novelties:

• Mesotarsal Ankle

• Digitigrade Stance

Ornithomimids

“bird mimics”

• lost teeth; herbivorous; fast

First evidence of feathers announced in 2012, based on fossils from Alberta, Canada.

Ornithopoda

Evolutionary Novelty:

• Kinetic Skull

Include Hadrosaurids and Iguanodontids

Orbit

The opening in the skull when the eye is

Oviraptor

“Egg snatchers” (but not really — were thought to eat Protoceratopsid eggs, but the eggs were actually their own)

Cretaceous of Asia and North America

Pachycephalosaurs

“Thick-head-lizards”

Evolutionary Novelty: Thick skull (skull cap up to 20 cm thick)

Evidence that domes were used as ‘battering rams:’

• Scars/Lesions on dome

• Lesions on dome associated with damaging tissue infected bone.

Paraphyletic

• Ancestor + SOME descendants = BAD (artificial, incomplete branch on evolutionary tree)

• A group that includes an ancestor and some but not all of its descendants

Plesiosaurs

First known from Late Triassic, dominant during Jurassic and Cretaceous

Become extinct at the end of the Cretaceous (mass extinction)

Sea turtles, best modern reptilian analog

Predentary bone

lacks teeth (like a beak), for cropping vegetation; An Evolutionary Novelty of Ornithischians

Protoceratopsids

Cretaceous, Asia; No horns; a Ceretopsian

Has frill and dental batteries

Polytomy

When more than two branches stem off of a node; example: Dinosauria (due to uncertain relationship between 3 groups)

Dinosaur Polytomy

CLASSIC VIEW:

Saurischians & Ornithischians, theropods and sauropods are sister groups

New proposal:

theropods and ornithischians are sister groups! Ongoing debate.

Prosauropods

“before sauropods”

• relatively small (2-10 m long)

• Earliest were bipedal, later were capable of both bipedal & quadrupedal locomotion

Mid Triassic - Early Jurassic

paraphyletic group!

Psittacosaurs

About a dozen different species

Known from hundreds of specimens (one of the best known dinosaur groups)

Small bodied, bipedal animals that retained that shape over time

A type of Ceratopsian

Pterosaurs

• First known from the Late Triassic

• Dominate Jurassic skies

• Some declined during the Cretaceous (as birds diversified)

• Became extinct end Cretaceous (mass extinction). 

• Capable fliers:

  • Keeled sternum

  • hollow bones

  • Air sacs for unidirectional breathing

• An Ornithodire

Ray-finned “fish” (Actinopterygii)

An Osteichthyes; “ray wing”; These fish have little needles of bone running from the ends of the fins to the body wall

Reptile

Evolutionary Novelty: B-keratin scales; two types: early anapsid and diapsid

Reverse pubis

An ornithischian and maniraptor evolutionary novelty; Ancestrally, this bone faces forward but it faces backwards in Ornithischians and Maniraptors

Secondary loss

A feature was developed and then a species lost that feature. An evolutionary novelty appeared and then was lost later. Ex: Snakes are tetrapods, their ancestors had limbs, but they lost those limbs later

Sedimentary Rock

Form from eroded pieces of other rocks (sediments) that accumulate in low lying areas. Sediments often bury organisms, preserving their remains. As sediments become rock, these remains become fossils. Often we can determine the RELATIVE ages of these rocks (not the absolute ages because that would just reveal the age of the sediments making up the larger rock).

Igneous Rock

Form from melts (magma, lava) that cool and solidify. Only rarely preserve fossils (ash). We can often determine their ABSOLUTE ages.

Metamorphic Rock

Underwent heating or pressure during their history, changing everything about them. Formed in places where rocks get carried to great depths (like seduction zones). Usually destroys any fossils that were in the rocks before pressure was applied (but rarely fossils can be found in them).

Sister group

The branches stemming from the same node; also known as closest relatives

Surface area to volume ratios

Surface area (SA) increases as Volume (V) increases BUT NOT AT THE SAME RATE! Generation of heat is proportional to volume and Loss of heat is proportional to surface area

Small things loose heat more readily than big things -> greater relative surface area

Large animals need fewer calories to maintain heat (relative to size). Therefore, they can live off of lower quality food (but still need lots of it).

Stegosaurs

“roof lizard”

• plates and spikes

• quadrupedal (stout limbs, broad hands, stubby fingers)

• simple teeth

Sauropodomorphs

• First known from Late Triassic

• Dominant in Jurassic, with worldwide distribution

• Decline in Cretaceous

Evolutionary Novelties:

• Long neck (at least 10 vertebrae)

• Small heads relative to body size

Sauropods

Evolutionary Novelties:

1. Denser, columnar limb bones

2. Nasal openings on top of skull

3. Necks with at least 12 vertebrae

4. Even smaller heads

Includes Diplodocids, Brachiosaurus, and Titanosaurians

Snakes

A part of “lizards and kin”; a diapsid; saw secondary loss of legs (tetrapod ancestrally)

Synapsid

characterized by one temporal fenestra; includes mammals

Tetanurans

a type of theropod

evolutionary novelties:

• Stiff tails

• 3-digit hands

• complex branching air sacs