Lecture 7 Flashcards
What is the primitive character of all vertebrates?
a vertebral column
What is the precursor to a vertebral column? How is it similar to a vertebral column?
a notochord (is a fluid fuel structure that runs through the body), had similar functions as a vertebral column like structure and support
What is subphylum vertebrata?
has animals with a jointed vertebral column
What is the difference between a cephalochordata and a chordate? Give an exmaple of a cephalochordate?
cephalochordates have heads as well notochords- ex pikaia (small 5 cm, discovered in the burgess shale and 505 ma, is one of oldest known ancestor of all cephalochordates)
chordates- have notochords but no head
What was the first animal to develop a vertebral column?
The jawless fish
What are some examples of jawless fish?
Modern hagfish and lampreys
What are lampreys?
are jawless fish that are parasitic- they attach to other fish and get food from them and travel on them, have blocks of cartilage as a vertebral column
The first vertebrates possessed what?
A head and a vertebral column
Jaws likely evolved from what?
pre-existing support structures in the gills
What are gnathostomes? What about the primitive forms?
are animals with jaws and vertebral column, some primitive forms have a skeleton made of cartilage
What happens to the diversity of jawless animals when gnathostomes evolve?
decrease due to competition
What are osteichthyes?
are fish with bony skeletons
Osteichythyes can be split into what two big groups?
the ray finned fishes and the lobe finned fishes
What are sarcoptergyii?
Are the lobed finned fishes, have fleshy and limb like fins along with vertebral column, jaws, and mineralized skeleton
What is tiktaalik?
is a transitional taxon- was an extinct lob-finned fish that had weight bearing elbows, simple wrist bones, and simple fingers- called a fishapod - fish with feet, also had gills and lungs
What are tetrapods?
Are vertebrates with four true limbs
Modern tetrapods have lost what? What have they retained?
Have lost tehir gills, but have retained their lungs
How are primtive amphibians (frogs, newts, toads, and salamnders) bound to water?
they need it to reproduce
What are ichthyostega?
are the first tetrapoda (vertebrate to live on land)
Do lobed finned fishes and primitive tetrapods share homologous structures?
Yes, the shoulder girdle, humerus, and radius and ulna are all present and similarly arranged in both
What are amniota?
Are animals that developed a membrane called the amnion in eggs which allowed them to becoe fully terrestrial as the eggs was protected from drying out. Amniota do not include amphibians.
What evolved with amniota?
a calcified/leathery shell, yolf for nutrition, and waste management system
Are humans and other mammals also amniotes?
yes but the eggs is retained internally
The amniotes are split into what two groups?
The diapsids and the synapsids, diapsids have a single pair of temporal fenstera, dipasids have two pairs
What do the temporal fenestra accomodate?
A bulging jaw
synapsids include what?
mammals and their ancestors
Diapsida include what?
dinosaurs
How is a clade a monophyletic group?
it is a group of organisms that includes a common ancestor and all descendants
Are dimetrodon and wooly mammoths dinos?
No are synapsids- had one temporal fenestra
What is dimetrodon referred to as? When did it live?
mammal like reptiles- wrong as they don’t have characteristics of mammals or reptiles- are synapsids
lived beyond the time of the dinos
dinosaurs have two temporal openings and are therefore…
diapsids
What includes diapsids?
birds, pterosaurs, crocodiles, lizards, snakes
The diapsids are split into what two groups?
split based on differences in skeleton, are split into lepidosauromorphs (have short, non-overlapping vertebrae in the neck) and archosauromorphs (have longer vertebrae in the neck which overlap to provide support for longer necks)
Are pterosaurs dinos?
no they’re flying reptiles
What are the archosauria?
they are a subset of archosauromorphs so they have two pairs of openning behind the eyes, have long overlapping vertebrae in neck but they also have a addtional oppening in front of the eye called the antorbital fenestra
what are the two groups of archosauria?
Ornithodira and Crurotarsi
What differentiates the ornithodira and crurotarsi?
-Diffences in stance due to ankle structure (crocs sprawl- pterosaurs, bords, and dinos are upright), motion is limited to front to back
How are pterosauria and dinosauria and birds flight an example of convergent evolution?
pterosauria adapted to fly by elongating digit IV, birds formed a seperated adaptation to fly
What is a digitgrade posture?
Is something dinosauroorphs exhibit, is due to the hinge like ankle joints which cause them to stand on the balls of their feet- allowing for a longer stride, move effeciently and continuously
What are the characteristics of dinosauromorpha?
were small (~ 1 m or
less including the tail), lightly built, insectivorous or carnivorous, and many walked
on all fours but ran bipedally.
What indicates that primtive dinos were bipedal, and quadropedal stance came after?
The group of dinosauromorphs most closely related to dinosaurs were apparently
bipedal
