Exam 2 Geo 2150 Flashcards
Jawless fishes
Two modern taxa (hagfish and lamprey) but there were a variety of armored forms in the Ordovician and Silurian called ostracoderms
Jawed fishes
(gnathostomes) first appear near the end of the Silurian
Successful groups of Paleozoic jawed fishes included
-Placoderms(Silurian-Carboniferous) heavily armored group, dominated the Devonian
-Acanthodians(Ordovician-Permian) extinct shark-like group, aka“spiny sharks”
-Chondrichthyans(Silurian-recent) modern sharks and rays and their ancestors and distant unclesOsteichthyans(Silurian-recent) the bony fish
Bony fish (two groups)
ray-finned- (actinopterygian)dominant fish today
lobe-finned- (sarcopterygian)fossil record goes back to the Devonianancestor of the tetrapods
Cladogram
branching diagram (aka dendogram) that groups organisms based on the presence of shared derived characters.
Lobe-finned fish are the group from which ______ evolved
tetrapods
- Connecting salamanders and Ceolacanths
- there are many skeletal details that match between lobe-finned fishes and tetrapods (vertebrates with 4 limbs) even if the bones have different functions in different groups
Tiktaalik
- The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb
- a transitional form (aka“missing link”) described in 2006
- Tiktaalik- a fish with wrists
Why would fish want to climb out on land?
1) avoid predators
2) get from one drying puddle to another
3) access to terrestrial food sources
Individuals with an ability to survive and move on land (even to a limited degree) might have survived better in some environments compared to closely related individuals more wholly dependent on water.
Fish challenges of living on land
breathing
support/locomotion
desiccation (drying out)
reproduction
The transition between water and land fish
drought tolerant fish can gulp air and “breath” a little through moist skin
amphibians have lungs as adults (often with some “breathing” through moist skin)
reptiles- breath through lungs
also skeletal modifications
Ichthyostega
an early tetrapod that lived during the Late Devonian (~370 Ma) in Greenland
7 TOES!
How are lobe-finned fish and amphibians similar?
Lobe Finned Fish & Amphibians share similar body plan & style of locomotion
Reptiles* vs Fish
- Reptiles still flex but are less “fishy” when walking
- more solidly interconnected skeletal structure
- weight carried by bones
- more rigid support
- Scaly, dry, keratinized skin- reduces water loss (no “breathing”through skin either)
Amnion (chicken egg)
protection, encloses embryo in aqueous environment
Allantois (chicken egg)
waste, gas exchange
Yolk sac (chicken egg)
encloses food source
Chorion (chicken egg)
gas exchange (inside of the albumen/egg white)
amniotes
can be divided into three major groups recognized by the number and position of holes in the skull behind the eyes (= post-orbital fenestra)
(Anapsid, Diapsid, Synapsid)
Are turtles anapsids or diapsids that lost their fenestra?
New molecular data suggest the latter, and this conclusion is increasingly being accepted, but it is not important for this class.
Generalized Tetrapod Phylogeny
Relationships among major tetrapod groups. Labels on branches represent clades that include all taxa from the location of the label upwards and away from the stem. Characteristic Mesozoic groups are shown in blue.
Archosaurs
- diapsids with additional pre-orbital fenestra, also teeth set in sockets and a different ankle structure than other diapsids
- archosaurs include dinosaurs and pterosaurs (extinct) and birds and crocodiles(extant)
- modern archosaurs are the birds and crocodilians,but dinosaurs and pterosaurs are also archosaurs
features in rocks allow the environment at the time of ______ to be inferred
deposition
some taxa have distributions limited by ________
Temperature
Triassic Global Climate
1) Arid
2) Hot (warm at poles)
Jurassic Climates:
1) Arid
2) Warm (cooler than Triassic, still not freezing at poles)
Cretaceous Climates:
1) Relatively wet
2) Hot (mostly warm at poles)
synapsids include:
mammals and their relatives
Synapsid
the dominant tetrapods during the Permian (290 Ma –250 Ma), but anapsids & diapsids (maybe including the early archosaurs) also lived then.
Phanerozoic diversity-
the biggest change after the Cambrian explosion is arguably the extinction at the end of the Permian
Geography, climate, and vegetation all very______ from today
different
Sprawling posture
In a sprawling posture legs project ~horizontally from the body. Bodyweight supported by muscle and the feet swing laterally while moving.
Upright posture
In an upright stance, legs are ~vertical under the body. Bones carry much of the weight and motion is all front to back.
Dinosaurs (and their closest relatives)
upright posture
-ball on the proximal femur (joint with hip) offset from shaft of the femur
-hip socket thickened, acetabulum perforated
-novel ankle (front/back hinge instead of rotation)
4thdigit has 3 or fewer phalangies
three or more sacral vertebrae
backward directed glenoid (shoulder socket)
Saurischians
“Lizard-hipped”dinosaurs
Ornithischians
“Bird-hipped”dinosaurs
Allosaurus
- could tell (in theory) chordate, vertebrate, tetrapod, diapsid, archosaur, dinosaur, “saurischian”