Vert Anat. Exam 3

How do turtles relate to other tetrapods?

Anapsid Skull

What major features define turtles?

• shell

• all lay eggs - no parental care

• long-lived with slow population growth

• environmental sex determination

What class do turtles belong to?

Sauropsids

What skull type were turtles originally thought to have?

anapsid skull, but now thought to be a secondarily derived characteristic

Anapsid Skull

a solid roof of bone with no temperal openings behind the eye socket

What are the pros and cons of having a shell?

Pro - protection, habitat adaptation, and strucutal suppot

Con - limited mobility, vulnerability to damage, and enviromental sensitivity

What are the TWO extant lineages of Turtles?

1) Crytodires

2) Pleurodires

What is a major difference between the two extant lineages?

• Cryptodires retract their head into a shell by bending in a vertical S-shape

• Pleurodires retract their head in a horizontally (to the side)

What are the main structures of a Trutle’s shell?

Scutes

Carapace

Plastron

Scutes

horny epidermal plates that cover the bones of the carapace and plastron

Scutes Function

protection against predators, injuries, and infections

What are the 3 types of Scutes?

1) Vertebral - center

2) Pleural - sides

3) Marginal - edges

Carapace

dermal bone under scutes (top shell)

Carapace Function

protect vital organs and structural support

Plastron

dermal ossifications; allows for flexibility (bottom shell)

Plastron Function

provides anchorage for muscles, aid in respiration, and hinges between bones to help with protection and mating

What are Turtle’s two main skeletal adaptations?

1) vertebrae and ribs fused to shell 2) girdles internal to ribs

What is the importance of fused ribs for turtles?

important for the structure to support a specialized muscle sling for breathing and provide stability for digging.

What is unique about turtle girdle placement?

girdles inside the Wharibcage

So how ventilate lungs if ribs are fused?

using specialized abdominal muscles that wrap around their organs to move them, which expand and compress the lungs to breathe. Rather than moving ribs, they shift thier visceral organs up and down to change pressure inside the shell.

Where are turtle lungs attached?

attached to the carapace

How do aquatic turtles get oxygen underwater?

They can exchange gases via the pharynx and cloaca

What are the two INHALE muscles?

Serratus and Abdominal oblique

What are the two EXHALE muscles?

Transverse abdominus and Pectoralis

What’s the process of Inspiration?

Serratus pulls the pectoral girdle forward —> abdominal oblique pulls the posterior limiting membrane back —> viscera drops and lungs expand

What’s the process of Expiration?

pectorlais pulls pectoral girdle backward —> transverse abdominus pulls posterior limiting membrane forward —> viscera is forced upward which froces aid out of lungs

How many chambers does a turtle's heart have?

3 - 2 atria and 1 ventricle split into three compartments

What are the 3 ventricular compartments?

1) Cavum pulmonale 2) Cavum ateriosum 3) Cavum venosum

How do turtles reduce blood mixing?

The ventricle has muscular ridges that help physically separate blood before it leaves the heart. During specific conditions, cardiac shunting allows turtles to regulate their circulation.

Right-to-left Intracardiac Shunt

deoxygenated blood bypasses the lungs and flowing into the systemic circuit

What’s the function of Right-to-left Intracardiac Shunt?

• helps during diving and apnea

• improves O2 usage

• Aids in digestion (CO2 —> gastric acid)

How do turtles thermoregulate?

bask in the sun (small turtles) or thermal interia (larger turtles)

Thermal Inertia

The ability to resist rapid temperature changes helps them retain warmth and cool down at a slow rate

What reproduction strategy do all turtles follow?

Oviparous

How do sea turtles find nesting sites?

use magnetic and chemical cues to find the place where they were born to lay there nest

What sex is usually produced at higher temperatures?

High-heat incubation produces the larger sex -- females

What are the major threats to turtles?

• habitat loss

• climate change

• overharvesting

• pollution

How does blood flow through the turtle's heart?

enter through the right and left atrium —> right atrium, blood comes from the body and passes to the cavum pulmonale / left atrium comes from the lungs and passes to the cavum arteriosum —> then blood goes through cavum venosum —> ejected into the left and right aortas to supply body and lungs

Mesozoic Era

”Age of the Reptiles”

What are Diapsids?

two pairs of temporal openings on thier skull sides, allowing for larger jaw muscles

Archosaurs

dinosaurs, pterosaurs, and others like crocs and birds have evolved from this group

What percentage of marine life died in the Permian extinction?

95%

Name two possible causes of the extinction

1) asteroid 2) massive volcanism

Why was this extinction important for diapsids?

This event allow diapsids to diversify

What does the late Cretaceous show about modern lineages?

shows evolutionary radiation success

Evolutionary Radiation

where a single ancestor splits into many new species over a relatively short geological time period.

Key features of Archosaurs

• Antorbital fenestra

• inverted triangular orbit

• Trend towards bipedalism

• 4th trochanter

What are the three main groups in Archosaurs?

1) Dinosaurs

2) Pterosaurs

3) Crocodilians

Whats the purpose of the antorbital fenestra?

gland, muscle and air filled. In front of the orbit

Bipedalism

only use two legs

Caudofemoral muscle

On the 4th trochanter on femur and believed this is why they could stand up right on two legs.

Crocodylomorphs

group of archosaurs including modern crocodilians

Features of Crocodylomorphs (mesozoic)

• Aquatic + terrestrial

• Bipedal and quadpedal

• Huge size variation

Extant Crocodylia (modern)

Alligators/Caimans, Crocs, and Gharials

Key features of Extant Archosaurs (Crocodylia) (modern)

• Allis + caimans —> freshwater

• Crocs —> salt water

• Gharials —> fish specialists

• Grow slowly throughout (indeterminate)

• The opening of the jaw is weak, but the muscles closing the jaw are strong

How are crocs caring parents?

• guard nest and hatchlings

• Respond to baby distress call

How is sex determined in crocodiles?

temperature sex determination. low temp = female and high temp = male

Why are crocs great predators?

• death roll

• ambush predator

• can sense vibration of single drop of water

• can gallop on land

Secondary Palate

nasal + mouth closed off so they eat + breathe at the same time, also being partially underwater, they can still breathe through their nose.

What are crocs’ social behavior and vocalizations?

• Courtship and territorial displays are common

• often hunt in groups

• mandibular glands secrete green lipid-pheromone

What role does sound play in croc behavior?

used for communication, territorial defense, mating, and maternal care

What are mandibular glands used for?

used to attract mates, mar

What are Croc heart characteristics?

• 4-chambered heart

• NO mixing

• Foramen of Panizz

• right and left shunting

What benefits come from blood mixing?

1) to aid in digestion 2) to accerlate warming

Why do crocs use shunting?

facilitate rapid digestion of large meals, conserve oxygen druing long dives, and mange metabolic waste

What group did our modern birds evolve from?

Avemetatarsalia

What does the diverse clade Avemetatarsalia include?

Pterosaur and Dinosaurs

What is pneumatization?

air filled cavities wtihin bones - make them lightweight

Why is Bipedalism important?

freed up forelimbs for other functions like seizing prey and may evolve to become wings

What do Dinosaurs divide into?

Ornithischians (extinct) and Saurischians (includes extant birds)

Which group developed flight from the Avemetatarsalia?

Peterosaurs

What unique characteristics do Ornithischians and Saurischians have?

widespread bipedalism with hindlimbs beneath body

Synopomorphy

shared or derived trait found in two or more taxa in their recent ancestors, not found in their past ancestors.

What were Pterosaurs?

flying diapsids/reptiles

What are some common characteristics of Pterosaurs?

• skin for the wing, but had fine hair covering

• soar/coastal vulture-like flight

• unsure if they lefts egg to fend for themselves

What are the characteristics of Ornithischians?

• herbivores - horny beaks, no teeth

• all extinct

• believed that the plates on thier back were used to exchange heat — but not sure

What are the characteristics of Saurischians?

• elongated, mobile, S-shape neck

• very long tails and neck to balance each other

What are the two groups Saurischians are divided into?

1) Sauropods 2) Theropods

What are the characteristics of Theropods?

• bipedal

• carnovores

• very strong bite force

• Some have fused bony sternum and a furcula

Which group led to birds?

Theropods

Sauropods

quadrepedal herbivores

What are the shared traits between birds and theropods?

• hollow bones

• feathers

• furcula

• S-shape neck

• tridactyl foot

• egg boarding

What is an Archaeopteryx?

MOST IMPORTANT FOSSIL - link between are birds and theropods

What bird traits did it have?

feathers, large furcula, and long mobile neck

What reptile traits did it have?

Teeth, long tail, and scales

What are the two main groups of Diapsids?

Lepidosaurs and Archosaurs

What significant adaptations are found in the crocodile's heart?

right-to-left shunting and the Foramen of Panizza

How can we infer that dinosaurs provided parental care and were social?

inferred from fossilized nests, hatchlings found in large colonies, and skeletons of adults nearby. Some fossils show parents atop nests, suggesting incubation similar to that of modern birds.

What are the two major amniote lineages?

Synapsids and Sauropsids

What are the two divisions of Lepidosaurs?

1) Squamata 2) Sphenodontidae

What are the characteristics of Squamata?

• skin covered in overlapping scales

• shed

• loss or reduction of limbs

• transverse cloaca slit

• determinant growth

• bilateral penis (hemipene)

What are Squamate’s kinetic skull adaptations?

• loss of quadratojugal bone

• movable joints in the skull

• allows cranial kinesis

Why is skull flexibility important?

allows them to eat things bigger than their head

Why kinesis matters?

better prey handling, stronger bite, and can swallow prey larger than its head

What are the key adaptations of chameleons?

• Zygodactylous feet

• long tongue

• Prehensile tail

• eyes move independently

• camouflage

What are the characteristics of Amphisbaenians?

• limbless or reduced limbs

• burrowing —> annuli (ring outside the body)

• skin loosely attached

• specialized skull for digging

What did early snakes (Mesozoic) have?

• legs

• pelvic remnants

What are the key anatomical features of modern snakes?

• forked tongue

• body elongation

• one lung reduced

• organs staggered

What is the function of a forked tongue?

delivers chemical stimuli to paired vomeronsasal organs

What are snake skull adaptations?

• extremely kinetic skulls

• loss of 2nd temperal bar

• paired links operate independently

• mandibles joined only by muscles and skin