March 15 Lecture
Pterosaurs (one of three groups we look at with powered flight- other 2=bats, birds)
-means “winged lizard”
1st appear in Triassic (same as dinosaurs)
Extinct @ end of Cretaceous
*50 genera known
***synapomorphy= elongate 4th finger (main wing support)
Pterosaurs are broken down into 2 groups:
1) Pterodactylids- “wing finger”- the larger of the two groups
Synapomorphies (ACTUALLY ARE SYNAPOMORPHIES):
-nasal opening and antorbital fenestra are combined (a bone that separates
them is usually wiped out during fossilization)
-cervical ribs are only on the posterior end
-short tail, or no tail
-may not have teeth
-long metacarpals (longer than the radius and ulna)
-short 5th toe
-new wrist bone called “pteroid” (ALSO IN RHAMP.)
2)Rhamphorhynchids- smaller of the two groups
differentiating features (not synapomorphies):
-teeth
-nasal opening and antorbital fenestra are separate
-cervical ribs
-short metacarpals
-long 5th toe
-tail
***Interestingly, we don’t know if rhamphorhynchids are their own separate group or not
because they haven’t found any synapomorphies.
-On a cladogram, this ambiguity is portrayed as a “polytomy”- it looks like a
number of different lines diverging from one point
-Pterosaurs use 1 finger to support wing (bats use 4)
***Why we think they were active flyers:
-Have good eyesight (large optic lobe)
-Large floculus in brain (suggests they have good balance and agile birds are similar)
-Huge sheet of bone in chest (like birds) used for flight muscle attachment (sternum)
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-large well-developed shoulder muscles (impression left on fossils)
Locomotion Controversy:
1) Berkley Model:
a. Leg w/ mesotarsal ankle feet below body…thus, they ran like a
theropod
2) George Washington University Model
a. Crawling stance, pressure is on hind feet and claws
i. Trace fossils of footprints and clawprints support this model
Where was the wing membrane attached?
-if wing attaches to ankle, the Berkley model (upright stance) is less viable
*Pterosaurs are thought to have similar wing membranes to bats
-in bats, there is a correlation between the wing length and the leg length (no
correlation for birds)
-We’ve found a similar correlation in Pterosaurs, supporting the attachment of the
wing membrane to the ankle
#cool fact: the “quetsecotelus” (sp?) is friggin huge- size of a plane and shit!
March 22nd 2005 Dinos Notes

Archaeopteryx = first bird –p. 7.2 note the overall similarity in hand and wrist between birds and
dinosaurs (short metacarpal, phalangeal formula 2-3-4, ascending process on astragulus, and
reversed hallux).

Protoavis (Triassic) –is he too old to have evolved from the Triassic? He is much older than his
closest relatives on the cladogram (all Cretaceous) –this means that:
A) fossil record is badly incomplete (implies we will find maniraptura in Jurassic
B) birds branched off earlier in Therapod tree (or, if you believe in Proto, before
theropods)
Tends to prefer A) because of similarities between theropods and archaeopteryx: semilunate
carpal, reversed hallux, phalangeal formula, anterior knob of pubis, pubic foot disappearing,
short first metacarpal.
Fossil of protoavis horribly incomplete (wishbone, for example, assumed from piece that has perfectly
broken off—nearly impossible)
FEATHERS
Modified scales for a) insulation (most likely) b) predation c) display d) flight (wrong because feathers
occurred earlier in theropods than did flight) e) combination of some of these
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DID FLIGHT ORIGINATE FROM THE “GROUND UP” OR FROM “TREES DOWN”?
Ground up: --therapods lived on the ground, so they somehow gained lift, so maybe birds went ground up
BUT HOW TO MAKE THE TRANSITION?
Trees down: --gliding came first, then powered flight—allows for incremental improvement
SO WHERE DID ARCHAEOPTERYX LIVE, AND HOW WELL DID HE FLY?
Ground up: --Ostrum at Yale argued that claw arch indicated ground-dwelling birds (but just qualitative)
Trees down: --more rigorous analysis indicates that claws used for perching, climbing

Archaeopteryx has large chest for attachment of flight muscles, suggesting active powered flight
BUT HOW WELL DID ARCHAEOPTERYX FLY?
The wishbone is poorly developed, so less bone for muscle attachment. But if cold-blooded, this wouldn’t
matter, because cold-blooded burst of speed is higher (cold-blooded muscles more potent).
SO WAS ARCHAEOPTERYX COLD-BLOODED?
The similar, more modern birds with growth rings in their bones would imply this, so the muscle
attachment might not preclude good flying. BUT 1) Archaeopteryx had symmetrical feathers, which would
imply poor flying…maybe a flightless bird?
Animals that can’t have their arms meet behind their heads have small articulations surfaces. Birds have
large articulations surfaces because they need large range of motion. 2) Archaeopteryx is in the middle,
with less mobility than modern birds. So 1) and 2) would imply trees-down.
AND THEN
It was discovered the partridges used their wings for inverse lift—flapping to keep legs on ground, even on
obstacles past the vertical. SO GROUND UP plausible for the first time.
BUT
That same week, Chinese published evidence of a cretaceous dino with wings on all legs, tail—glider—
TREES DOWN.
This lecture was, I believe, supposed to illustrate the still-massive questions and holes left
in the records…..but it ended up being very confusing as a result, with no definitive
answer at the end.
March 24th .2005 Dinos Notes
--Ornithischian hip—pubis backwards, pre-pubis
--ornithischians start out as small bipeds but evolve into wide range of different creatures (all start
off as small bipeds, though)
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ORNITHISCHIAN SYNAPOMORPHIES: (see picture of heterodontus)
1) ilium elongated forward (to compensate for rotated pubis for muscle attachment?)
2) rotated pubis
3) ossified tendons, at least above sacral region
4) teeth become leaf-shaped with central ridge (**independent origin of herbivory**)
5) predentary bone (NEW BONE—rare, because most are modifications!)
6) reduced antorbital fenestra (due to chewing food)
7) palpebral bone (boney eyelid—also NEW BONE!)
8) foot reduced to three functional toes
neomorph—a new structure
Everything that isn’t lesothosaurus is called…genosaurus!
GENOSAURIAN SYNAPOMORPHIES:
9 Recessed tooth rows (cheeks)
10 mandibular fenestra much reduced
Hypsilophodon—all the fixins AND a rigid tail (related to running agility)
Thought to be tree-climbing because thumb was dislocated during fossilization
Thyreophorans (stegs/Ankylosaurs)—shield of modified dermal scutes--**tooth row is S-shaped
Scutellosaurus—biped with lots of dermal scutes
Scelidosaurus—larger, obligate quadrupeds, dermal scutes, and mandibular fenestra lost
Synapomorphies that unite anchylosaurs and stegosaurs:
1)
ilium forward and outward (muscles attach to femur—maybe because they are now
really large??)
2)
closure of antorbital fenestra
Stegosaurian synapomorphies: large plates and/or spines on back and tail
SKULL—tiny, herbivorous teeth, predentary bone, no mandibular
fenestra, no antorbital fenestra
PLATE—spongy bone at bottom for flesh attachment (evenness on
both sides implies plate stood upright), grooves for blood vessels for
keratin sheath (maybe for heat exchange??)
JUST OVER ONE ROW of plates, larger ones in back
Sacral Brain??? Enlarged portion of nerve cord in hip (in some mammals, e.g. cows, as a relay station, not
an actual brain)
April 5th.2005 Dinos Notes
Ornathischians have palpebral and predentary bones, to the exclusion of the saurischians and euparkeria
Ankylosaurs—1) Expansion of hooded ilium
2) 3 extra sacral vertebrae (8 total)
2) Internal nostrils at back of mouth (secondary palate—can chew and breath at same
time… similar to Parasaurolophus)—developed independently of mammals
3) Armour spread evenly over body
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Nodosaurids—Jaws follow curve in tooth row, long limbs held erect underneath the body
Ankylosaurids—Skull wider than it is long, tail club (vertebrae interlocked), some skulls horned,
lower temporal fenestra closed, internal nostril in back of mouth
Randomly stops here to talk about the lab where we measure leg
lengths, decide whether the dinos are running or not, figure out
the scenario, etc……don’t know if this matters or if he was just
explaining….
THREE TYPES OF REINFORCING THE TAIL! (THE VERTEBRAE INTERLOCKED
ARE THE THIRD EXAMPLE, THOUGH HE DOESN’T GO THROUGH THE FIRST
TWO—THEY ARE LIKELY IMPORTANT, THOUGH)
OSSIFIED TENDONS is another example.
**********************************this all links to that lab, which he tries to explain*************
He then goes into how heavy were dinos—and how do we weight things that heavy?
1) make a model, then estimate volume, then displace water (a la Archimedes)
2) measure circumferences of humeri and femurs, use it to guess
These two methods gave very different answers, and whichever one you choose depends on how
you reconstruct your dinos (i.e. thin or meaty).
Cold-blooded animals need less muscle, because that muscle is more powerful…SO…how we
construct dinos depends on whether they were warm- or cold-blooded….which translates into how
dinos would have walked on different surfaces
If a fossilized footprint breaks off at any point, you could be left with just the very bottom (the
underprint), which would show something very different than would the entire fossil, had it not
broken. BEWARE!---thus, in the same dino, you could get different footprints, simply depending
on where the fossil broke.
For sauropods, the center of mass is over the hip. Thus, the large hind feet might give shallow prints, while
the tiny front feet might sink deep. There are all these pictures of footprints, and the prof. goes through all
the possible scenarios for each—for example, because sauropods have such tiny feet, they likely didn’t live
in watery environments, because they would sink.
********************************end of lab talk******************************************
Ornithopod (Hypsilophodon/Hadrosaurs/Iguanadonts) synapomoprhy: prepubic process
extends anteriorly of ilium
Hypsilophodon synapomorphies: prepubis rod-shaped, tail ensheathed in ossified tendons
(mistakenly thought to be tree-climbing)
Orodromeus—eggs have creatures with bones fully formed, implying little parental care needed
Apr. 7th
Ornithopods
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Heterodontosaurus (NOT AN ORNITHOPOD) very much like ornithopods with teeth in
front of mouth.
 Two major groups of ornithopods

Iguanadont

Hadrosaurs (Duck billed dinos)
 Synapomorphies (sheet 11-5, uses Ouranosaurus as example for both Iguanadont
and Hadrosaurus):
2. Loss of teeth in front jaw
3. Nares (bony expression of external nostril) increases in size (half size of skull in
some)
4. Prepubis gets particularly large
5. Back prong of pubis reduced in size
6. Third finger has a “hoof” on it
Synap of Iguanadont
7. Thumb spike
In ourranosaurus you should notice the elongated neural processes  has hump in back,
buffalo have same elongation of neural processes (looked alike?)
Didn’t go over Iguanadont a lot b/c we had already covered it
Flesh covers neural processes (up and over, not just in between)
Hadrosaurs (Duck bills)
 First dino found in US, in New Jersey
 Edmontosaurus (sheet 11-6)  spectacular size of noses…
8. Four fingers
9. Prepubis continues to grow (enormous)
10. Even more reduced pubis (tiny)
11. Increased # of sacral vertebrae (up to 10)
Skull is almost size of the man
Nostril half the size of skull
Fossil skin is preserved
Mumified Hadrosaurs (guts included…)
Structure associated with giant nostril
 Bony part of nostril =/= nostril proper
 1 artist assumed it was inflatable

warning

attracting mates

maybe both are right…
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In mummified Hadrosaurs (dried out first, then buried) there appears to be extra skin in
the nares  supports notion of inflation
These Two major groups of ornithopods (Iguanadonts and Hadrosaurs) have flexible
jaws.
Chewing process:
Grinding surfaces
// \\
As lower jaw moves up
Upper jaw moves out
Teeth continually erupt forward as they are worn down
Largest Hadrosaurs can have ~ 3000 teeth!
Maiasaura (Slide 11-6)
- 1st dinosaur ever named with feminine ending (saurA, not saurUS)
- Outlines nostril, beak, eye socket, upper temp. fenestra, lower temp. fenestra, and
famous “gap” in area of jaw articulation
- Adult femur compared to a juvenile femur
- up to this point there had been no juvenile fossils found
- 1st extensive fossil record of juveniles
- in adults you have fully ossified ends of limb bones
- in juveniles ends are NOT fully ossified
Adult Jaw  see teeth stacked in there “waiting to erupt”
- in juveniles, # of tooth rows are greatly reduced
- extensive wear on teeth = suggests eating “adult” food
Nests:
 many juveniles in each (mother lays clutch of eggs)
 in each nest juveniles are the same size = implies that they hatched at the same
time
 juveniles were different sizes in different nests = implies that they are living for
some time in their nests
!!!Suggests very strongly adult care!!! (sophisticated parental care)
- could be foraging with protection
- could be brought food
Behavior of Parenting in Maiasaura:
1. not fully ossified limb bones = implies not fully self sufficient individuals
2. extensive wear on teeth = suggests eating “adult” food
In Maiasaura nests we find lots of tiny egg shell fragments (eggs that were being hatched
were being trampled on)  evidence of duration
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In Orodraunus (theropod) nests there are few large egg shell fragments  hatched and
just left (?)
Spacing between the Maiasaura nests is about ½ an adult body length = implies packed in
tight (as close as you can get them)
- in modern bird rookeries you have a similar pattern
Large number of Maiasaura come and lay/hatch their eggs and then move on
 you would expect to find dino “trash” – coprolites (crap)
 many coprolites around the nest
many pictures of dino nests, alligator nests, alligators carrying young (parental care like
maiasaura)
Tending of young appears to be an Archosaurian condition (all major groups have it in a
way)
In Montana, there are bone beds of Maiasaura with thousands of bones present
Finds bone bed A, finds identical bone bed B, hill  bone beds extend over several miles
There are in the order of 10,000 + individuals preserved
Herds of 10,000 Maiasaura like buffalo.
Clear evidence of herding
Implies catastrophic death
Hypothesis:
Volcanic eruption (killed through poisoning/afiixiation of CO2)
Two major groups of Hadrosaurs
1. Non-crested group (at most small but solid crests)  still very elaborate nasal structure
2. Spectacular Hollow Crests
Might have been comfortable in water, but just b/c they have a duck-bill, doesn’t mean
they lived like ducks…
Parasaurolophus (slide 11-7):
- spectacular crest
- neck has rather elaborate curvature (initially reconstructed with neck out, but then fixed)
- usually neck twisted after death in fossils (tendons contracted)
- with Parasauralophus anatomical research suggests it was actually curved
- down flexure in neck associated with need to feed from ground
Slide 11-7 (part with hand of duck bill dino)
- trace fossils support this reconstruction in some cases.
- appears to be a flesh pad at the palm (like elephant, to support the weight)
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Nostril
- internal nostril at back of throat (chew and breathe at the same time… similar to
ankylosaurs)
 consistent with chewing mechanism we have seen so far
Nostrils make nice musical sound.
But no flaring at the nostril
 like bassoon, so volume is muted
so its not like a trumpet (which actually does flare out…)
Evolution (Simple Darwinian evolution):
1. Variation
2. Selection
a. Natural selection: right locomotive equipment to function in world
b. sexual selection: if opposite sex doesn’t find me attractive, I wont be able to
pass on my genes…
(a vs. b?)
Sexual Selection:
- can be very strong if mating is non-monogamous (harems: one male, many females)
if male is very attractive, long crest
makes it to next generation
 next guy w/ long crest gets all girls
 can lead to exaggeration of characters
Peacock with large tail feathers.
Sexual selection less important in monogamous relationships b/c everyone finds some
sort of mate (attractive w/ attractive, ugly w/ ugly… all genes are passed along, mostly)
Evidence that Sexual selection operates:
Widow birds: - long “sexy” tails
- tails get you girls
cut some tails and taped it onto another (so extra long)
females REALLY like long tails (more nests)
correlation between length of tail and # of nests
why are tails not incredibly large???
- principle of frustration: if tail feather gets excessively long, so difficult to survive
- getting girls v. getting girls…
- attractiveness vs. survivability (tradeoff)
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Apr. 12th
Finish from last time and look at pachysephalosaurs and ceratopsians
Many animals within genera, Prof. just chooses some from each group
Parasaurolophus
Hollow crests
- some suggest that they are there to hold air under water (snorkels as well)
- no opening
- not enough room for much air
NOT probable
Back to sexual selection
- can cause exaggeration of traits that indicate that some would be better mates than
others.
- Assumption:
- males have bigger crests
- females have smaller crests
 females do the choosing and males are chosen.
Why does this make sense?
- females have large parental investment (lay, grow, care for eggs)
 if they pick wrong guy, they lose a lot
Gender with the highest parental investment usually does the choosing
- making, laying of eggs
- actual parental care (post birth)
it’s the general rule, but not always true.
- Birds, it’s the males with the bright plumage, so again are the chosen
Exception (not violation of principle, just of which sex does the choosing):
- Seahorses: female lays eggs and male promptly picks them up and puts them in
a pouch
- female seahorses are chosen (“parade around”) and males choose
Seems to be the case for reptiles, and therefore probably for most dinos as well
Test hypothesis that: Sexual selection is responsible for crest in hadrosaurs
1. Variation of “Use it or lose it” law: takes combinations of genes to make structure, if
they are not kept by natural selection and those genes are not preserved, then they will
fade away.
- Extra flange of bone (w/o opening for nostril) that makes the crest larger than it
needs to be. Why is that there? This is extreme in Lambiosaurus
- Extra pieces of bone must be used for something, this may very well be for
display purposes (a.k.a. sexual selection)
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 Suggests that some parts of crest’s external morphology does not correspond to
the shape of the internal airways.
 extra bone is therefore for display
2. Eyes (and ears b/c they are making noise) should be well developed is expectation if
sexual selection is responsible for crests.
- not a strong expectation as there are better (much better) reasons to have well developed
eyes and ears  mostly could be used to disprove hypothesis if these are not present
 well developed eye and ear present
 fail to reject on this notion
3. Crest shape should be species specific: you don’t want to attract other species, b/c they
can’t pass on your genes.
 each species have unique crests
 one of strongest hypothesis.
4. You’d expect to see more elaborate crests where more than 1 species exists
- not too strong a hypothesis…
 if only game in town, you don’t need to differentiate yourself that much
there does seem to be a general correlation that there are more elaborate crests when
more species exist in the same time
- could be part of skewed fossil record
Nothing in paleontology that says that we are clearly wrong to assume that crests are
result of sexual selection
“The hypothesis is not contradicted and seems reasonable”
If this is true, you might expect to see more differences between males and females
This seems to be true, and has led to many reassignments of fossils from one genus to
another.
 Fossils with different crests could have been classified as different species or genera,
when in reality there was only one species with males and females that had different
crests
 morphological species concept.
Lambeosaurus: crest lies in front of the eye rather than above it. Helped match same
species. Before some female Lambeosaurus were classified as Corythosaurus (crest
above eye).
Names of bones that make up the skull:
- Premaxila bone
- in non hollow crested hadrosaur it forms the anterior of the nares
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- nasal bone occurs in posterior
- nostril in between
Nasal bone can get to be behind the head. The premaxiliary bone starts in right place, but
ends up by top of skull or way back, actually behind head.
Crest atop skull is made up of the bones that surround the nostril.
Almost all synapomorphies created from preexisting structures, as opposed to completely
new ones.
Sliced through crest shows air passages  extensions of nasal cavities inside them.
Part of elaborate color schemes in paintings of dinos are not only for camouflage, but also
for sexual selection.
Shows range of hollow crested hadrosaurs  not examinable
- just know there are a diversity of forms
Marginocephalians (cephalic = head, having a margin on the skull)
Synapomorphy:
- incipient frill
Pachysephalosaur:
- frill doesn’t get any bigger
In ceratopcians, it gets completely out of control (the frill)
Pachycephalosaur Synapomorphies (Pachy= Thick; cepha = head; saur = lizard… thick
head lizards)
2. widened hips #
3. thickened skull roof #
4. Pubis excluded from acetabulum (like crocs)
3. thick skull: extra thickness of bone not from premaxiliary or nasal bone, but rather of
bones that usually lie on top of skull (which just thicken)
2. Widened hip:
Hip region of pachycephalosaur (Slide 12-1; view from top)
 illium is displaced away from backbone by hips (ilia usually plastered against
backbone)
4. Pubis doesn’t make contact with acetabulum. Ischium makes contact with ilium at the
front.
- technical only
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Teeth diagnostic: beady edges indicative of pachycephalosaur.
Stegocerus (type of Pachy) (Steg = roof; cerus = head… roof head)
- thick skull for headbutting?
- all are bipedal
1. Thick skull – indicates head butting of course
2. Wide hips – stable stance so that you are not propelled at a weird angle when striking
opponent.
- physics of butting heads: bowling balls (skulls are dome shaped, so will bounce
at weird angles
 could have made for many broken necks
- probably hit on foreheads where they could SEE opponent (instead of random
guess, you are both in trouble if you miss)
- probably didn’t run long distances before butting, but short starts.
3. Stiffened backbone: have additional bones in region between neural process and
backbone. Hence mobility of backbone is really limited, so can’t rock from side to side
- this does not appear in tail
- expected if you undergo many collisions
4. Angle at which backbone joins skull. Particular to stegocerus
- in all our dinos the backbone attaches right to the back of the skull.
- in humans it attaches from bottom to skull
- In stegoceras it attaches at an angle.
- if it connected straight, you are at a danger of breaking your neck
 upon contact all the impact force goes straight down your backbone and into the body.
5. Shelf at back of skull for extra musculature (muscle attachment) to help stabilize the
head during impact
6. Closure of upper temporal fenestra (due to thick skull roof)
- a little feeble
A lot of morphological characteristics that make stegoceras a unique group that does
suggest that they butted heads.
Head butting as part of sexual display? It creates a loud noise…
Pachycephalosaurs:
- Bony knobs on skull
Evidence Sexual dimorphism: characteristic of sexual selection operating.
- men try to dominate the other males instead of parading for women
Last great group of Ornithicians  Ceratopsians
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Synapomorphy:
5. Rostral bone on top of snout (opposite the predentary bone)
 neo-morph: brand new structure as opposed to modification of old one (just like
predentary bone
Psittacosaurus (Slide 12-2)
Ceratopcian: frill, but its tiny
- no horns
- bipedal!
Face of this animal reminded discoverers of parrot
- has rostral bone, so we know he is ceratopcian, but otherwise we wouldn’t know that
these evolved from a quadraped
- does not have wide hips of pachycephalosaurs
-Ilia are right up against the backbone
-box shape skulls
- small group in numbers as well as in stature.
Neoceratopsians: next group up
Synapomorphies:
6. First 3-4 neck vertebrae fused
- frill is starting to grow, so need support
- weight of skull going downwards, but fusing helps support this
- little ball that connects neck to head, particular to only Neoceratopcians (if you see one,
and only that, you know you have a neoceratopcian)
Proceratopcians:
- frill has grown in size – musculature to the neck from here (assumed)  come down
onto sheering jaws.
- frill itself is not solid (has random holes there)
- it has become a quadraped
- in some of them there is a hint of a horn
A number of protoceratopcians… some have horns…
Looks like there is sexual dimorphism:
- largest frills males (are chosen) and smaller ones females (do the choosing)
- b/c of parental care again.
Dino’s Lecture Apr. 14th
Frills break off in a lot of fossils.
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Ceratopsids (giant horned ceratopcians)
Synapomorphies
7) obligate quadrapeds
8) prominent frills
9) Secondary skull roof (slide 12- 3)
- primary skull roof is in front of brain case
- seems to be associated with development of horns is that you get a second sheet
of bones coming up, which makes the secondary skull roof
- have to go through two sheets of bone to get to the brain.
- if you see from above, you see the secondary skull roof
- probably nothing to do with respect to protecting the brain, but rather with
development of large frill
dental synaps.
10) development of teeth batteries
11) teeth have split roots
- teeth stacked on top of each other like hadrosaurs, but with two differences
1. Morphological: if look in at the side (front of animal) you see that teeth have
split roots (stacked on top of each other like chevrons /\). In hadrosaurs the teeth are
stacked side by side and not split (we saw this in lab)
2. Functional: skull is massive, and not flexible, so cant grind food like
ornithopods, so how do they grind their food?
- surface of the tooth is essentially vertical, so it is a sheering edge, not a grinding surface
chewing: lower jaw goes up and teeth intersect like scissors and slice food.
- led some to believe that they were carnivores cutting meat with teeth, but
could be large things like logs
Taxonomy of this group (ceratoptians) is not well established
- many variations and species designated and we don’t know if there are 9, 12
or 24 species (triceratops), or if they are just one species with some variation.
**Function of the frill and horns:
1. (Frill) Muscle attachment (all the way down to the jaws)
2. (Frill and horns) Protection – very reasonable
3. (Frill and horns) Display/competition for mates (sexual selection)
4. All of the above
5. (Frill) For cooling of heating
- vascularized sheet of bone, like elephants, use their ears for heat/cooling
Said that this is good for multiple guess tests…
Any time that we see something ornate, it could be for sexual selection
There are many ceratopcian bone beds  implies herding (like Maiasaura)
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Genera in ceratopsids traditionally split in two groups (Slide 12-3)
1. Centrasaurs: characterized by centrasaurids (long face, short frill)
Skull base long
Nose horn longer than eye horn
2. Chasmosaurs: (short face, long frill)
Eye horn longer than nose horn
Slide 12-4 Centrasaur
Rostral bone
Predentary bone
Large nostril area
Recessed tooth line
Little bit of eye horn but not much
Short frill
Ossified tendons (ornithician synap)
Sclerotic ring
Show several pictures, says that they look like rhinos, and are about the same size
Not clear how musculature was set up, could have been smooth from back to frill so that
frill is not noticeable with flesh, or it could come up from neck, highlighting the frill
(sizable gap between frill and rest of body).
Bone beds of 50 + centrasaurs found, evidence for herding
Stirachasaurus (spectacular spines going off of frill)
Color on frills (in drawing)?
- assumption that frills are part of sexual selection, so they are ornamented
Chasmosaurus:
Huge frills
Huge nostril area
Big chunks of bone that don’t usually break off, so great fossil record
Big eye horns
Reminds us that there are large diversity of forms
**One last tax-on:
Triceratops:
A little bit strange
1. Eye horns are larger than nose horn, BUT
2. It has a short frill
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Is it a centrasaur or chasmasour?
Suggests that split b/w centrasaurs and chasmasaurs is artificial
 not a good classification b/c triceratops doesn’t fit into it neatly
- no satisfactory cladogramatic arrangement
Slide 12-4 (horns hitting each other)
Intra-specific conflict: within own species
- frills also for sexual selection
So:
Not for natural selection between different species, but for sexual selection within
species.
Ball for skull attachment in ceratoptians
Discovery of it in north slope of Alaska
Only ever seen in backbone of ceratopsians
North slope of Alaska is close to North Pole
- has led to suggestion that significant vegetation in Alaska
- 70 million years ago North slope of Alaska was actually closer to north pole
than today (continental drift)
In late cretaceous we have dinosaurs at the poles (don’t know if they were there all the
time or if they migrated in summer/winter)
Evidence of large plants
 These two things imply that late cretaceous was much warmer than today
the world that we live in is about in the coldest of times
During late cretaceous (controversial) the world was sea ice free
 Today, the average temperature difference between the pole and the equator is approx.
80 degrees F.
 in late cretaceous we think this temp. gradient was approx. 40 degrees F. If 80 degrees
at equator, its 40 degrees at pole.
World still on axis  poles are dark for ½ the year  vegetation can’t grow
Suggestion: Extensive migration
Evidence of herds
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Social beasts
Lived in poles
 This all started from fragments of bones that were JUST identifiable
Now we have completed our survey of our dinosaurs.
Generalities:
Dinos are characterized by giants, but they start off as small bipeds
Theropods
Sauropods
Ornithicians
Thireopheans
Ceratoptians
Even though fossil record is dominated by obligate quadrapeds, or giants, small bipeds
dominate the origins of all the major groups
 Implies with gigantism (assicated with, but not always meaning, quadraped) evolved
several times.
Lots of small insignificant beasts in Triassic
We have covered about 80% of the well preserved dinosaur groups
Missed a couple of them
 expect new types to be discovered! Particularly given the incomplete nature of the
fossil record
Things that have more recently come to light:
Sauricitian type with fused neck, huge ischia, long tail, long fingers
Expect that in the next 2 decades we discover and classify new groups
Looked at all Archasourian groups
In this lecture he will try and look at new animals relatively “synapomorphy-free”
Gustavo note: so don’t expect to see synapomorphy questions from this lecture
Nothosaurs (Euryapsids)
Plesiosaurs (Euryapsids)
Placodonts (Euryapsids)
Ichthyosaurs (Euryapsids)
Think Plesiosaurs evolved from Nothosaurs
All these groups evolved in the Triassic
Different skull types:
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Anapsids: turtles (no temp. fenestra)
Synapsids: Mammals (only lower temp. fenestra)
Diapsids: (upper and lower temp. fenestra) Archosaurs, snakes, lizards
Euryapsids: Plesiosaurs, ichthyosaurs (only upper temp. fenestra)  all marine
 in bottom of Euryapsid skulls you find remnant of a lower temporal fenestra
means that a Euryapsid is just a modified diapsid
Euryapsids classified in cladogram under diapsids.
Euryapsids:
- modified diapsids
- all marine
- all derived from terrestrial ancestors
- means that they all breathed air
- means that they all started with four limbs etc.
Nothosaurs:
Exclusively in Triassic
Least modified of all these
Real paleontologists use bones surrounding holes to classify fenestra, not just location
like we have in this class
Distance between front of nose and nostril
- no antorbital fenestra, b/c not an archosaur
These guys are rather large, but some are tiny
Important characteristics:
How did we know that they lived IN ocean, and didn’t simply live by the water and got
washed into the ocean sediments upon death?
Short version: how do we know that they’re marine?
1. Only found in marine rocks (not conclusive, but only found by salt water not
sweet)
2. Ilium is barely attached to the backbone.  not bearing weight, supported by the
water
- In Eupacheria, there were 2 sacral vertebrae, then in dinos there are 3, and they
get up to 10. In this case they are only loosely attached, as opposed to “plastered” to
backbone
3. Limb bones not fully ossified  doesn’t look like limbs are load bearing in same
way as terrestrial organism
4. In some cases there are stones in the stomach  think may be due to ballast (in a
ship you put stones or bricks to keep it floating to keep it flowing in the right
direction) – possibly for gastroliths like birds and sauropods, but these rocks don’t
appear to be really smooth (tumble)
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5. Front legs are often more robust than hind legs  locomotion in water
- in terrestrial animals, even quadrapeds, hind limbs are usually larger
- humuri are thicker larger bones than femurs
- on land hind legs are more important for locomotion
- For swimming
- In dolphins and other marine animals, front fins disappear.
6. Pubis and shoulder girdles lie under the body, not at side
- You can see all of them from underneath
- Bones associated with front limbs and pubis, ischium and ilium have all been
moved underneath
- If you’re going to locomote in water you want your limbs underneath, where
your propulsive force is
7. Long and pointy teeth, used to eat fish, like pterosaurs (a little “lame” for an
explanation)
Nothosaurs:
Suspect that they lived relatively near land
Locomoted in land for some extent, but most of time in water
Laid eggs on land like turtles
Plesiosaurs
Confusing in terms of origin
Body of plesiosaur, but skull of nothosaurs ???????????????????????????????????????
Found separated but close
 May have evolved from Nothosaur, but could be 2 different species
Skull of plesiosaur ?????????????????????????????????????????????????????????????
Nostril pulled away from tip of snout
Large eye
Upper temp fenestra (huge)
Embament (remnant of lower temp fenestra?)
Large pointy teeth on the outside
Two varieties
Pliosaurs: short neck, long head
Plesiosaurids: can have incredibly long necks and short heads
- 96 vertebrae (longest found)
Limbs have become flippers (on both)
Fingers now create a solid surface for propulsion
How did these locomote?
Two models
Oars?
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- just push huge volume of water behind you, pulling yourself forward.
Wings?
Generate lift, wings for underwater.
Pengins, sea turles have flippers, but use them mainly for lift
We believe the wings locomotion, given shapes of plesiosaur flippers, like penguin and
sea turtles.
Like Nothosaurs: limbs and girdles (shoulder) are underneath the body
April 19: Mesozoic Monsters: Going from land back to
water
Wkshts. 14-1 and 13-1
Last lecture: Studied euryapsids and argued that they are modified diapsids, and studied
nothosaurs and began looking at plesiosaurs.
This lecture: We will finish studying the plesiosaurs and move on to studying
placodonts, Ichthyosaurs, and living reptiles.
The marine Mesozoic monsters are euryapsids (only an upper temporal fenstra) and it is
likely they are modified diapsids (so they lost their lower temporal fenestra).
Four marine Mesozoic monsters (a 5th group, the cretaceous marine varanids we will look
at in the end of the lecture): see diagram on 14-1
Nothosaurs – Triassic
Plesiosaurs - Most likely originated from Nothosaurs. Lived to end of Cretaceous
Placodonts – (small group) Triassic
Ichthyosaurs – Became extinct ~ midway through the cretaceous
How have limbs lost differentiation of bones as they have re-invaded the water?
The nothosaur’s limbs resemble most closely a terrestrial form, then the plesiosaurs, then
placodonts, then Ichthyosaurs. In the nothosaurs the front limb becomes more robust
than the hind limb (in all dinos except brachiosaurus the hind limb was longer). In
plesiosaurs phalanges are added to lengthen limbs. In Ichthyosaurs the paddle widens
and additional columns of phalanges appear.
This could definitely be an exam question – refer to the last question on lab #9
Plesiosaurs:
Variety of ecologies associated with Plesiosaurs:
Some had long necks and short headed; others short neck long headed
Some had sharp teeth used to hunt fish; others had robust teeth used to eat oyster and
clams
Placodonts: Small group that needs to be worked on
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Ilium not attached to vertebrae because it no longer needed to have load bearing limbs
Like nothosaurs they still have chevrons and neural processes – disappear in ichthyosaurs
Crushing Feeding Mechanism – see diagram on 14-2
Used spatulate teeth to scoop up clams and oysters, and then used the crushing teeth to
crush their food.
Possible Exam Question: See diagram on top of 14-2
Give three reasons why we know this isn’t a turtle:
1) Turtes are anapsids and this is a euryapsid
2) It (turtle) has lost the chevrons and neural processes on its tail
3) Limbs aren’t typical of terrestrial forms, they aren’t robust enough
4) In turtles shoulder blades sit inside ribs and this specimen has shoulder blade outside
the ribs.
Ichthyosaurs:
Schlerotic Ring see diagram on right side of 14-2
Preserved in many
Had huge eyes possibly so they could dive deep and hunt or hunt at night.
Bacterial pseudomorph: Excellent exam question
No bone in the dorsal fin, but there are many specimens where a body outline is
preserved. Carbonatious film (synonym for bacterial pseudo morph) shows body outline,
and after analyzing biochemically the black substance is bacteria in composition. We are
seeing a bacteria pseudo morph of the original shape of the Ichthyosaurs (people often
fabricated this outline to increase the value of their discovery).
Evolution of Ichthyosaurs: Extreme modification of the limbs
1st Ichthyosaurs:
No Bend in tail
Ilium attached to backbone, but just two vertebrae
In 1998, Ichthyosaur discovery in Japan illuminates relationships
Provides conclusive evidence that the ilium was attached to two vertebrae
Oddly shaped neural processes on tail we presume were used to support initial part of the
tail.
Loss of lower temporal fenestra: 14-2 lower left corner
We see remnant of lower temporal fenestra, but it fills in as they evolve
Controversial and poorly preserved: diagram lower left 14-2
Since only one specimen has this we suspect something weird happened in preservation.
In advanced Ichthyosaurs: (most Jurassic and all cretaceous forms)
The tail bends downwards, is this bend real? Yes
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1. It is always down; if it was arbitrary we would expect to see different orientations
2. Body outlines (Bacteria Pseudomorphs) show tail vertebrae in position
3. Wedge shaped caudal vertebrae create the bend. This morphological reason clinched
the fact that the bend is real and not just a matter of the way preservation operates.
Bloating:
Ichthyosaur, like dolphins and whales, gave live birth and had breech births (the infant
comes out feet or buttocks first)
When whales and dolphins die their stomachs rot and begin to bloat. We suspect
Ichthyosaurs bloated also
Bloating explains why fossils of pregnant Ichthyosaurs falsely appear like they died while
giving birth; the position of the infant is a result of bloating.
Did Ichthyosaurs give live birth?
Yes, but we suspect eggs were laid internally and hatched while still in mother
Plenty of present evidence for this in snakes, lizards, and sharks.
Of all the nothosaur, plesiosaur, and placodont fossils none have infant fossils inside
them, so we suspect they laid eggs on land as sea turtles do.
Dolphins echo-locate, could Ichthyosaurs? NO
In dolphins the ear (otic) capsule is isolated from the scull by soft tissue. This isolation is
necessary for echo-location because if not the whole skeleton will pick up the vibrations
from the echo.
The ichthyosaurs’ otic capsules are fused to the skull, so they did not echo-locate.
Now we move to the living reptiles!
Reptiles are more diverse than mammals
- 4,000 species of mammals
- 6,000 species of reptiles
Lepidosaurs (diapsids) – what lizards and snakes together are called.
Lose the lower bony bar of the lower temporal fenestra.
This allows for greater flexibility in the skull
Diagram 13-1 top left; Cross section of the skull
Reduction of bone in back of skull increases flexibility
2 Lepidosaur synapomorphies:
1. Mesokinetic Suture (Flexure Joint):
Some surmise that it aids in feeding, it allows them to open their mouths wider
2. Pleurodont Teeth:
Teeth are plastered up against the inside of the jaw, not in sockets
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Varanid (subdivision of Lepidosaurs) Lizards: The 5th group to invade the water
Ex. Komodo dragon
1. All have a coronoid bone (banana shaped bone).
2. Intramandibular Joint provides flexure in the lower jaw
These 2 characteristics are found in Mosasaurs.
Lecture April 21st
General Overview:
Look at remaining group of living reptiles: snakes, crocodiles, turtles and another strange
group called amphisbaenids. Then move to general question if dinos were warm-blooded
and more general how we infer the physiology of things.
Snakes:
Evolved from one of the lizard groups
Just as birds are dinosaurs, so are snakes lizards
Skull has extreme flexibility. See wksht 13-1 lower left. Many points of flexure.
Some snakes can dislocate their lower jaw.
Snakes have a variety of poison delivery mechanisms
N. America – hollow fangs, very effective delivery
Australia – groove in fangs, slow injection
Snakes and Lizards - 6,000 living species – tend to be tropical because their small size
doesn’t hold up well in the cold.
Mammals - 4,000 living species
Fossilization for snakes and lizards is poor because of their small size and their terrestrial
habitats. Thus, even though they first appear in the fossil record in the Jurassic, we
suspect their origins were in the Triassic.
I think this is just professor Marshall getting jollies from ranting about random dino
knowledge that we will never be tested on (esp. since he never wrote it down) but here it
is just to be sure:
Before producing cladograms (cladistics) snakes, lizards, turtles, birds, and dinos used to
have their own classification. However, the use of cladistics shifted the philosophical
approach to classification. Instead of looking for what separates organisms, scientists
began to look at what unites them using morphology and DNA. This lead to the
disintegration of the use of the Linnaean hierarchy. The Linnaean hierarchy is now only
used informally because it was based on the distinctiveness between things, rather than
what they have in common.
Turtles: Anapsids
Built very differently from other vertebrates
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Moving from the outside of the turtle to the inside, here is what we hit:
1. Keratin plates
2. Bone of shell
These two layers are called the shell
3. Ribs/backbone
4. Shoulder blades!!
Shoulder blades lie inside ribs!
Arms come out from inside the rib cage!
Wksth 13-2 top
Top of shell is called carapace
Bottom of shell is called plastron
The dotted line is the keratin
The solid line is the bone
Origins of turtles are shrouded in mystery:
The line of 5 different skulls shows the remnants of upper temporal fenestra.
Wksht 13-2 R. side of page 2nd from top
1st turtle fossil
Couldn’t contract its neck
3 Ways to differentiate between Cryptodires and Pleurodires See diagram on 13-2
I. Neck contraction – develops independently in each
Cryptodires – (N. Hemisphere) vertical neck contraction
Pleurodires – (S. Hemisphere) horizontal neck contraction
II. Plastron is different in the two – never says how
III. Location of some of jaw closing muscles
Musculature runs over the palate in the pleurodires
Musculature runs up and over the otic chamber in cryptodires
We also have evolution of sea-going turtles
Developed rear flippers and front limbs that like wings, not paddles.
The shell also has been reduced.
Amphisbaenids:
Really, really strange, only specialists know about
Have no legs
Wormlike in appearance
Many burrow in the gound
Have giant areas for muscle attachment see diagram on 13-2
Neck muscles are primary means for locomotion and digging holes
Burrow into soil, then lift head, do over and over, push, lift, push, lift
Crocodiles and Alligators (looked at earlier in course)
8 living genera
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Also have internal nostrils at the back of the mouth (parasaurolophus and ankylosaurs)
Geosaurs (marine and in Mesozoic)
Unusual hips: in living crocs
Perforated acetabulum
Pubis excluded from acetabulum (like pachycephalosaur)
Reason for mentioning the above list (internal nostrils and unusual hips) to illustrate a
complication in terms of their similarities and differences with other groups
Warm-Bloodedness:
Warm blooded and cold blooded are too simple when talking about physiology
So we have six terms. Know these! Very important! See 15-1
Warm blooded – body temperature relatively high
Cold blooded – body temperature relatively low
Endothermic – endo means interior, so they use an internal heat source
Ectothermic – ecto means external so they use an external heat source i.e. the sun
Homeothermic – maintain a constant body temperature
Poikilothermic – having a variable body temperature.
To clear up terminology:
Typcially, when we say warm blood we mean an endotherm; and when we say cold blood
we mean ectotherm, but ectotherms can have warm blood (if they’re in the sun)
Endotherms can live in a variety of latitudes because they have an internal heat source,
where as ectotherms are more concentrated, they dominate the tropics.
Super Important!! This is the General Rule!
Human are warm-blooded endotherms and homeothermic
It makes sense if you think about it. If an animal temperature is always high then it must
have an internal heat source.
Lizards are cold blooded ectotherms poikilotherm
But there are exceptions!
Professor Marshall now gives many exceptions to rule, I don’t think it is important to
know specific examples, just know there are exceptions
Birds are all endotherms
Hummngbird: Exception to typical rule of endotherms being homeothermic
Humming birds are endotherms and poiklotherms
While sleeping they drop their body temperature in order to save energy for active flight.
Sea Turtles
Keep body temperature about 4 degrees C above ambient
So they have low capacity for endothermy, but are usually cold bloods
Sail Fish (marlin) are cold bloods, endotherms. It turns out that they have a heater organ
that warms the retina and fore brain. So a bit of their body is warm-blooded, but the rest
is cold blooded.
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If ectotherm, does it mean you must be a poikilotherm? NO
If you live in an environment that is the same year round i.e. caves
These examples are rare, but the point of all these examples is that we need all 3 terms.
**What is your temperature, where does your heat come from, does your temp. vary.
So were dinosaurs endothermic or ectothermic? Or to what degree?
Traditionally, it was believed that dinosaurs were ectotherms because they are “reptiles”
Then in the 1970-1980s deinonychus was discovered and we realized that dinosaur
hunted in packs which implied sustained activity which implies endothermy.
Birds are endotherms, and at time of deinonychus discovery we also discoverered that
birds evolved from dinosaurs (theropods) which tipped scales toward endothermy again.
Finally, we discovered polar migration with things like ceratopsians, which implies active
biology and thus endothermy.
Most conclusive evidence for Endothermy: the way we infer physiology
Bob Barker:
Endotherms must eat about 10X as much food as ectotherms
Thus, in a population there are many more prey than predators.
If predator is endothermic, only 1% of population is predator
If predator is ectotherm, only 10% of population is predator.
Looking at the percentage of predators in each of the six time periods on wksht 15-1 we
can infer that the dinosaur predates were endothermic because of the low percentages, so
the theropods were endothermic.
However, he ends by saying the next lecture offers evidence to believe ectothermy.
May 3—Characteristics that make mammals mammals
Professor Marshall spent the lecture going through the second half of the mammalian
synapomorphies.
First Half:
1)
2)
3)
4)
5)
6)
7)
8)
elbow turned backwards
knees go forwards
boney processes for muscle attachment
ventral part of shoulder girdle reduced to collar bone
ilium changes to forward projecting prong
pubis and ischium fuse together and turn backwards
femur get boney prongs (trochanters) for musc. Att.
Upright stance (1-8 related to upright stance and locomotion)
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9) Specialized first and second neck (atlas and axis)
10) Double attachment of skull to backbone
He started by talking about what defines a synapsid, which is that they have a lower
temperal fenestra, but no upper temperal fenestra. He then showed pictures of early
mammals, which were very small, probably covered in fur, and ate insects.
Synapomorphies –
- he went through synapomorhpies 11-22, really relying on the diagrams. So pay
careful attention to those. All the diagrams are from handout 16
- He showed the transition from Pelycosaurs to Therapsids to Mammals. He said
we don’t need to know the exact changes at each step, just the general trends.
Synapomorphies of Mammals 11 – Lower temperal fenestra greatly enlarged - The lower temperal fenestra is not
defined by its position, but rather by the bones which surround it.
12 – No boney bar between eye socket and lower temperal fenestra – most but not all
mammals have this.
13 – Secondary palate, can breathe and chew at the same time – internal nostrils move to
the back of the throat
14 – Teeth differentiated – So there are molars, bicuspids, etc.
15 – Teeth no longer grow continuously – why would you stop growing your teeth? With
mammals when their teeth fall out they die from starvation.
16 – Lower jaw is made of just one bone – mammals have only one bone of the lower
jaw, whereas reptiles have four
17 – Remaining bones of lower jaw in middle ear – Marshall spent a lot of time on this,
he showed that slide video thing which showed the transformation, but he said we didn’t
need to know the names of the bones. You can see the transformation to some extent in
living Opossums, who when young still have the more reptilian structure, but as they get
older their inner ear resembles that of most mammals. Also the inner ear is why we have
such good hearing. Mammals have better hearing than reptiles because we have more
bones in our inner ear. Its why some mammals can use echolocation.
18 – New bones involved in jaw joint – the new jaw articulation is with the lower jaw in
a different place, see the diagrams. The old reptilian jaw articulation is now inside the
inner ear. The first mammal is defined by the first time the dentary articulates with the
skull. (Some early mammal fossils reveal both jaw joints still present)
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19 – Large upwardly direct process on lower jaw – this is for muscle attachment, which
aids in chewing. Muscle on both sides of the lower jaw, also helps with side to side
chewing.
20 – Highly controlled closure of lower jaw (lower jaw slung in new muscles) – probably
why lower temp. fen. grew so much… for musc. Att.
21 – Teeth interlock with high precision
22 – Brain fully encased in bone
Some of the general points of the lecture:
The characteristics that we think define mammals are:
- Mammary glands
- Warm blooded (endothermy)
- Fur/hair
**However, these don’t fossilize well. So we do not consider them syapomorphies,
instead the first mammal is defined by the new jaw articulation
Also characteristics 11-21 are all designed to aid faster digestion. A lot of digestion
occurs in the mouth, which is why we have more muscles for chewing and teeth that help
to grind better. We need to digest more in the mouth so that we get energy faster, which
we need as endotherms. It all goes back to endothermy.
Price of Endothermy – need to eat more
Fossil Record – living mammal groups originated after the dinosaurs. DNA clocks
suggest much older origins.
Molecular clocks suggest modern primates originated in the cretaceous 85 million years
ago, but the first fossil primates are 55 million years old.
Many species are not in the fossil record, it is incomplete. Mammals are older than the
fossil record suggests.
May 5—Finishing Mammals, Humans, Identifying
Ancestors in Fossil Record, Genetics
Mammalian body plans are quite diverse—land mammals, water mammals, very large
mammals (e.g. elephants) and even flying mammals; ecological diversity exceeds that of
dinosaurs (who never entered oceans or flew)
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However, that’s not a fair comparison, because the correct basis of comparison (based on
“grand cladogram”) is mammals with reptiles—and these two groups have similar
ecological diversity
Mammal groups:
Monotremes—one of most primitive mammal groups (just two living species: platypuses
and echidna). Very unusual. They lay eggs, so retain some reptilian heritage. Also, while
they secrete milk, they don’t have organized mammary glands; instead, the milk secretion
is spread over the fur. (!) Skulls have electro-receptor organ, which allows them to pick
up electric currents of the muscles of prey in water, which they need because they’re
almost blind (cf many fish). Male is poisonous, with bony spur. On handout, we see tooth
of male platypus-type monotreme from late Cretaceous. (Mammal teeth are diagnostic,
because they don’t really break down)
Marsupials—largely in southern hemisphere. First marsupials in fossil record are in the
Cretaceous in the northern hemisphere. (Again, teeth are used to determine which species
is which.) They then became extinct in northern hemisphere, but later a land bridge
allowed opossum to remigrate to northern hemisphere. Marsupials have live birth, but
baby comes out extremely small, and climbs into pouch and attaches to pouch teat.
(Almost like still being in womb.) There is also a “conveyor belt” cycle from conception,
to womb, to pouch, that allows one baby to be in readiness while an older baby is nursing
in the pouch. If it dies, the fetus begins to grow. This complex biology allows marsupials
to overcome infant mortality issues and dump baby if you’re threatened. Note convergent
evolution (e.g. marsupial “wolf” and dog), functional convergence of features.
Eutherians—full development in the womb—if not a monotreme and not marsupial,
then it’s a eutherian. (Majority of mammals) On handout, Panamian land bridge allows
mammal migrations both north and south; almost everything large that invaded north
became extinct at end of Ice Age (see handout), partly because of homo sapiens. Large
species, including dinosaurs, are generally extinction prone.
(everything following is a eutherian…)
Primates: note tooth on handout is completely incorrectly labeled—not a primate tooth
and not late Cretaceous (whoops). First unequivocal primate is roughly 55 million years
old. Gorillas (close relative of homo sapiens) have lengthened ilium and head articulation
at back of skull (humans have shortened ilium and head articulation at skull base), as well
as opposable toes.
Closest living relatives are chimpanzees, who diverged from us around 4-8 million years
ago (based on fossils and molecular clocks); gorillas diverged around 7-11 mya.
Relatively rich fossil record of human-like things, but chimpanzee fossil record is
nonexistent, while gorillas are almost nonexistent in fossil record. Gorillas and
chimpanzees are African, while orangutans are in Indonesia; until 100 years ago,
orangutans were thought to be closest living human relative. For most primates, it’s rare
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to have complete skeletons (see handout for examples). After chimpanzee diverged but
before homo sapiens evolution, you had Australopithecus (4.5 mya to 1 mya)—“Lucy”
fossil (female due to width of hips). Structure of top of femur suggests bipedal stance, as
do fossil footprints in volcanic ash (3.6 mya). See toe curvature in handout, although it’s
not a straight line evolution chimp-austral-human. “Lucy” is intermediate between chimp
and human in characteristics, though.
Homo: our genus, starting with Homo habilis (handy man, from tools associated with
fossils; 1.5-2.5 mya). Homo erectus (1.6 mya-200k years ago); Lake Turkana boy and
Peking man—note wide geographic distribution. Homo sapiens neanderthalis had brain
size of around 1400 cm3, while Homo sapiens sapiens has brain size of around 1360 cm3
(but runs from 1000 cm3 to 2000 cm3), so not a huge difference. But point is that
Neanderthal man had a large brain. Homo sapiens sapiens emerges around 500k years
ago. At least in Europe, looks like modern humans and Neanderthals coexisted for a bit.
Some success in pulling out DNA from Neanderthal fossils, and indicates no evidence of
interbreeding between Neanderthals and humans at 30,000 years ago.
Ancestors: wide range of hypotheses as to relationships between Homo and
Australopithecus—maybe Lucy is pivot or maybe ancestry split earlier, with Lucy on
separate lineage, for example. Then, “hobbit” fossils found that seem to belong to Homo
erectus but became extinct around 18k years ago. As to relationship of chimps and
humans, seems we had a common ancestor and then the two branches became different
species. Missing link: link between anthropoid apes and human beings. Ancestors lack
unique characteristics, so they are identified on the basis of negative evidence; since
preservation of fossils is incomplete, these relationships remain provisional. Many
fragmentary fossils make human ancestor relationships tough to determine, but looks like
bipedality and low, broad pelvis evolve first; then barrel chest and elongated legs; then
chin, large brain and possibly language. Missing link is not standard, never preceded by
“the” and means something whose morphology may be used to determine the order of
appearance of evolutionary innovations and whose age may be used to place a minimum
estimate on the time of origin of evolutionary innovations. Peking man has “Broca’s
area” of brain preserved, that we think had to do with speech; however, it’s not only
necessary part for speech. Narakatomi boy has neck vertebrae preserved, and they show
that our nerve cord evolved to be much thicker.
Genetics: turns out most of the genes we have are in common with most other animals.
For example, we have 98.6% similarity with a chimp. Further, the genes for body
development are very similar between fly maggots and humans. By playing with these
development genes, you can dramatically influence development (e.g. get rid of wings,
get extra wings; extra eyes instead of antennae, etc.), whether in flies or humans.
Strikingly, you can use mouse eye development genes in a fly and it still develops an eye
in the fly! Thus, the gene differences are really relatively minor between very different
looking species.
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