Flashcards in Phylogeny and diversity - Part 2 Deck (49)
Draw the simplified tree of gnathostomes including the key traits of each group.
(mixini --> true vertebrae --> Petromyzontiformes) --> jaws, paired fins --> Placoderms, Chondricthyes --> Operculum, branchiostegal rays --> Acanthodii --> lepidotrichia, pleural ribs --> Actinopterygii --> true enamel on teeth, lobed fins --> Actinistia --> Choana --> Dipnomorpha --> folded tooth enamel --> Osteolepimorha --> tetrapoda
Also, indicate which are the osteichthyes and which are the sarcopterygii
Describe the acanthodii.
Very speciose group.
Now extinct gnathostomes.
Two pump system
May have outcompeted placoderms
Predominant in oceans for a while.
What is a dipnomorpha?
What is an osteolepimorpha?
Transitional, may not be a fish, important fish-tetrapod fossil
Actinistia includes what kind of extant fish?
Where did jaws come from?
First 2 gill arches of agnathans.
What could have been the selective advantage of half a jaw?
Increase in size of the first gill arch may have aided in respiration.
Can open and close the mouth for better respiration.
A stronger proto-mouth could have aided in filter-feeding.
What was the purpose of the second arch?
Hyoid arch forming part of the jaw suspension.
What was the first arch?
What were the purposes of the first two arches when becoming jaws?
Arches 1 and 2 got bigger for respiration with more muscles then got to feeding.
1st arch is main jaw and the second arch is for suspension
Tetrapods don't have gill arches. What did they become?
Middle ear bones.
What was the split early on from Osteichthyes?
When did it happen?
Sarcopterygii and Actinopterygii
Early on in Devonian (around 400 mya)
What are the most likely ancestors to all actinopterygians?
Skeleton mostly cartilage
extant species include paddlefish and sturgeon
More of a bony skeleton
Most of the actinopterygians are this.
Most diverse group of fishes.
Majority of fish species.
Modern bony fishes.
Draw a basic graph including osteichthyes, sarcopterygii, tetrapods, actinopterygii, holosteii, chondrosteii, teleosteii and palaeoniscids
refer to notes
What are neopterygii?
Stands for new fin.
These fish had more flexible fins, more rays, more lepidotrichia, more mobile.
Gave mobility and maneuverability leading to diversification
What is one way to reconstruct fossil phylogeny?
a lot of the early work on fish phylogeny was driven by discovering fossilized _____ in different strata
What are the 5 kinds of scales?
Placoid, ganoid, cosmoid, cycloid, ctenoid
Describe placoid scales.
Sharks have this.
Smooth one way, sandpaper the other way.
Do not grow.
Can be replaced
Related to teeth.
Cannot be used for aging
Describe cosmoid scales.
Found in sarcopterygians.
Grow with fish
have some blood flow
sturdy and thick, not flexible.
Describe ganoid scales.
Found in sturgeon
Very hard, bony armour
grow with fish, hard and good for protection
bad for flexibility
Describe cycloid and ctenoid.
Teleosts have these
provide less protection
more flexible and provide mobility
What are the 6 characters that make a teleost, a teleost?
1 - Reduced or missing scales.
2 - Two pump respiratory system
3 - Modified swim bladder
4 - Flexible jaws
5 - Homocercal tail
6 - Specialized fins
What is the evolutionary advantage of reduced or missing scales?
Lost ganoid for cycloid/ctenoid.
More mobility alloted.
Can now go into more environments.
Can catch prey faster and better avoid predators.
What is the evolutionary advantage of the two pump respiratory system?
Breathing without moving.
Can now hide of be stationary.
What is the evolutionary advantage of a modified swimbladder?
Better buoyancy control.