BZ 214 EX4

What is the difference between the jaws of crocs and alligators

V (crocs) shape vs U shape (alligators).

What is special about the the jaws of crocodylians?

complete secondary palate so they can breathe and eat at the same time.

What animals fall under the lepidosaur lineage and not the dinosaur one?

Reptilian versions of marine animals

What did birds exist at the same time with?

Pterosaurs

There were two evolutions of flight historically, what animals had them and were they related?

pterosaurs and birds and no they were not related.

How does the ankle bend change in the major lineage of archosaurs?

The presence of the heel and change in bones to allow for increased flexion of the foot.

Change in

marine mammals give birth tail first, head last so they can get oxygen from mother.

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Why are Ornithischian dinosaurs have “orn-” in the front.

they have a pelvic anatomy that is very similar to modern day birds. They were named this before we knew of a relationship with modern birds.

What did birds evolve from?

theropods.

What are pliosaurs and plesiosaurs and what type of predators were they?

reptilian versions of seals and sea lions, pelagic predators.

What were metriorhynchids?

marine crocodylomorphs

What is unique about the wings of pterosaurs?

Pterosaurs wings are thin membranes of skin that connect by one extended finger.

How did size differ between pterosaurs and modern birds?

Pterosaurs had a huge wing size range, some had large bodies, and these could not fly just glide. Modern day birds that have a weight limit (not more than 55 lbs). 

How does locomotion on land differ between pterosaurs and birds?

Pterosaurs were quadrupedal (walk on all fours) vs. birds are bipedal (walk on two feet).

True or False, birds and pterosaurs occupy different ecological niches?

False! They historically occupied all of the same ecological niche’s as modern birds.

True or False. there is no evidence to support the idea that Pterosaurs ever had feathers.

False! we have some evidence that pterosaurs had feathers on their bodies but not wings.

True or False, Pterosaurs walked with four limbs

False! They were quadrupedal but the front body part that touched the ground is a finger not a limb.

Where does the strength of bone come from?

Its ability to flex, hollow bones give more flexion.

What rises up first to become major land organisms?

Synapsids.

Why did the synapsids go extinct?

Pangea, due to large desert continent where moisture could not reach the center.

What did the breaking up of Pangea allow for?

The reptilian forms of organisms to rise up and colonize land.

How did reptilians anatomy change in order to conquer land?

Change in ankle, and shoulders to allow limbs to be pulled under the body allowing for the mammalian stance.

In what organism do we first see the mammalian stance?

Dinosaurs

How did large bodied Dinos go extinct?

volcanic activity and meteor.

After the extinction of large bodied dinos, only smaller animals remained, why?

Smaller animals need less food from their environment to survive. They don’t require as much energy from their environments as large bodied ones do. The environment did not have as much to give.

Why do so few sea turtles eggs make it to adulthood? How does this relate to energetics.

Enough energy must be put into the egg to allow it to develop as a mini adult and then complete a triathlon from the sand to the water.

What are more closely related to dinosaurs? modern birds or modern reptiles?

modern birds

What are the synapomorphies of dinosaurs?

Reduced/lost fourth and fifth digit on the hand. Foot reduced to three main toes. Three or more sacral vertebrae. Open acetabulum 

What does the increase in sacral vertebrae do for dinosaurs?

It strengthens the pelvis.

Why was there a low diversity of dinosaurs during the triassic?

Supercontinent pangea was most extensive which created a hot, dry, desert climate that rain. Rain couldn’t infiltrate the center part of pangea. Not a lot of hospitable land so very low diversity of dinosaurs.

What did the evolution of the pelvis allow for in dinosaurs?

Allowed for the dinosaur's legs to be held directly beneath the body. 

What makes a Ornithischian dinosaur unique?

Their pubis points posteriorly, lies against the ischium. 

What makes a Saurischian dinosaur unique?

Pubis points anteriorly (toward the head of the animal), separated from the ischium. 

Why do sauropods have long necks?

There was an environmental shift from low hanging to high hanging vegetation so the long necks allow them to maximize their food source.

What is the purpose of sacral vertebrae in dinosaurs?

They help to strengthen the pelvis.

How does the acetabulum in dinosaurs differ from other tetrapods?

It is open.

What happened during the Jurassic period that increased dinosaur diversity?

Pangea split into Laurasis and Gondwana. This created more temperate zones and greater diversity of biomes. More hospitable land.

What happened during the Cretaceous period that increased dinosaur diversity?

The diversity of biomes began to increased and temperature gradients formed. Ocean starts to break up land and the first flowering plants appeared.

What is the main shift from the triassic to jurassic and cretaceous periods that increased dinosaur diversity?

The increase in hospitable land.

Why does the fossil record not accurately reflect the true diversity of dinosaurs?

Only 10% of everything that has ever lived will fossilize and due to biases in the fossil record.

What are the two biases in the fossil record?

(1) We can only excavate on land (and only specific land) (2) Fossilization is very rare (only 10%)

What are the two main kind of dinosaurs?

Ornithschians and Saurischians

What are some of the primary features of Ornithschians?

They are bird hipped and all herbivores

True or False! Since Ornothischians are “bird hipped” birds evolved from them?

False! Ornothischians secondarily evolved this hip condition and in reality birds evolved from Saurischians.

What are the three kinds of Ornithischians?

Thyreophora, Ornithopoda and Marginocephalia

What makes Thyreophoran Dinosaurs unique?

They are heavily armored with osteoderm bony plates used for protection.

This is a stegosaurus, does it fall into Saurischian or Ornithischian and what sub category?

Ornithischia, Thyreophora.

What makes Ornithopoda dinosaurs unique?

They have a battery of teeth which re tooth plates on either side and top and bottom of the mouth.

What makes Marginocephalia dinosaurs unique?

They have bony shelves on the rear of the skull which they may have used to fight.

This is a triceratops, does it fall into Saurischian or Ornithischian and what sub category?

Ornithschia, Marginocephalia.

What are the primary features of Saurischian dinosaurs?

They are lizard hipped with some carnivorous.

What are the synapomorphies of Saurischian dinosaurs?

Anterior pointed pubis, increase in number and elongation of neck (cervical) vertebrae, hollow chambers (pleurocoels) in cervical vertebrae for a series of air sacs.

What is the purpose of the pleurocoels in Saurischian necks? What other organism is this similar to?

They lighten the neck and this is similar to birds who also use pneumatization.

What are the two categories of Saurischian dinosaurs?

Sauropods and Theropods

What makes sauropods unique?

They are long necked and lizard footed, quadruped posture, small heads, bifurcated vertebrae which allows for U shaped depression for possible dorsal ligament attachment, herbivorous.

What is an advantage of being a sauropod?

Having a long neck means you can reach higher growing vegetation.

What does the bifurcated vertebrae allow for in sauropods?

The dorsal ligament attachment helps to support the long neck. The ligament goes through a U shaped depression which supports the head, tail and neck.

True or false, it is easy for the sauropods to break down and digest plant material since they are herbivores.

False! No vertebrate can natural break down cellulose on their own and food would have to stay in the stomach for long periods of time. They depend on extra bacteria in the stomach.

When did the first sauropods appear?

Late triassic

There are two categories of Sauropods, what are they?

Macronarian and Diplodocid

What makes Macronarian Sauropods unique?

They have enlarged naris’s and longer forelimbs

What makes Diplodocid Sauropods unique? 

long flat snouts with elongated skulls, forelimbs are shorter than hind limbs, whip like tail.

What type of Sauropod does this skull belong to?

Macronarian Sauropod

What type of Sauropod does this skull belong to?

Diplodocoid Sauropod

Does this dinosaur fall into Saurischian or Ornithischian and what sub category?

Saurischian, Sauropod

What type of dinosaur was very diverse during the Cretaceous period?

Theropods

True or False! Theropods are not considered extinct.

True! Since theropods are the ancestors of birds and birds are still alive today they are not fully extinct.

Primary characteristics of theropods

Beasted footed and carnivorous.

Synapomorphies of theropods

bipedal with bird like 3 clawed feet, mostly carnivorous, presence of a furcula (wishbone), pronounced ant orbital fenestra and the presence of a maxillary fenestra.

What is the role of the pronounced antorbital fenestra and maxillary fenestra in theropods?

It allows for greater room for muscle attachment and therefore strengthens their bite.

What are the different groups of dinosaurs within theropods?

Tyrannosoroids and Maniraptorans

What makes Tyrannosoroids unique?

They are the largest theropod, with powerful jaws and strong skulls, small forelimbs, serrated knife like teeth.

What makes Maniraptorans unique?

feathered bodies, small and turkey sized, solitary, huge claw on the second digit of hind foot to grasp prey with feet.

What did birds descend from?

Maniraptorans which are theropods within Saurischian

Does this dinosaur fall into Saurischian or Ornithischian and what sub category?

Saurischian, Theropods, Tyrannosoroids.

What are some similarities between Maniraptorans and their bird descendants?

Feathered, carnivorous, use grasping feet and use their weight to hold down prey, furcula (wishbone), solitary hunters.

What is the Archaeopteryx fossil?

A fossil found that shows a mix of non avian and avian dinosaur traits, important transitional fossils.

What did the Archaeopteryx fossil suggest about birds?

That they were related to dinosaurs

What features did the Archaeopteryx fossil have that made scientists think that dinosaurs and birds were related?

Avian features like wings and flight feathers and non avian features like sharp teeth, three clawed fingers and a bony tail.

How are theropods and sauropods different?

Sauropods are quadrupedal theropods are bipedal, theropods have some carnivorous species while sauropods are strictly herbivores, different feet shapes, theropods are the ancestors of birds and have a wish bone, sauropods hav bifurcated vertebrae.

What is Gigantothermy?

The ability to maintain a stable internal temperature by simply being huge (low surface area/volume ratio) which means you lose less heat to your environment.

Why were large dinosaurs likely not covered in feathers?

They did not want to overheat.

Would a large dinosaur that uses gigantothermy have a high or low metabolic rate? How would this affect their temperature

low and they would maintain a body temp higher than their environment that varies little.

Why were dinosaurs most likely ectothermic?

Since their environment is hot they don’t have to worry about heat retention and true endothermy only evolved twice (birds and mammals).

True or False! Birds only evolved after dinosaurs went extinct?

False! Birds (avian dinosaurs) existed alongside non avian dinosaurs.

What is an example of a paleontological discovery that challenged our understanding of dinosaurs?

The discovery of the fossil “Archaeopteryx” challenged whether or not birds evolved from dinosaurs and changed our understanding of dinosaur evolution. 

What characteristics allowed some groups to survive the mass extinction that killed the dinosaurs?

Widespread geographic range, small body size, wide environmental tolerance, broad diet. Being adaptable and not needing a ton of resources. 

What are the characteristics of a mass extinction event?

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Large number of species must go extinct (65-75% or more). Affects a broad range of biomes, global, occurs shortly.

What makes the cretaceous-paleogene mass extinction unique?

It happened over a short geological time period.

What went extinct during the cretaceous paleogene mass extinction?

All non avian dinosaurs, all pterosaurs, 75% of birds, 23% of mammals, and more.

What caused the mass extinction?

Sea regression, volcanism, meteorite impact and climate change

What evidence do we have for the meteorite impact?

iridium layer and impact creates.

What happened after the volcanic activity and meteorite impact?

Crazy temperature swings which caused mass extinctions.

True or False, if the mass extinction of the dinosaurs never occurred humans and dinosaurs would live in harmony today.

False! The extinction of the dinosaurs opened up an ecological niche that mammals filled. If the dinosaurs never went extinct we would not exist today.

What is included in Lepidosaurs?

lizards, snakes and tuatara

What are the general characteristics of the cloacal slit of Lepidosauromorpha?

Transverse cloacal slit. 

What is included in Archosauromorpha?

crocodilians, dinosaurs, birds and pterosaurs.

What is special about the femur shaft and pelvic girdle in archosaurs?

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ventral side of the femur shaft has a caudofemoralis muscle inserted onto it. Modified pelvic girdle.

What is special about the skulls of archosaurs?

They are deep and the orbit of the eye is not circular but instead is shaped like an inverted triangle.

What trend in mobility started with the archosaurs?

Bipedalism