Class Notes (1,100,000)
CA (640,000)
UTSC (30,000)
Lecture 9

BIOC50H3 Lecture 9: Lecture Nine

Biological Sciences
Course Code
Jason Weir

This preview shows page 1. to view the full 5 pages of the document.
Lecture Nine:
Tetrapods Part 2: Marine Monsters of the Triassic, Jurassic and Cretaceous
- We’re talking about Pterosaurs, Dinosaurs and relatives
- In phylogeny tree, this is Archeosauromorpha
o It’s a diapsid
o Closely related to squamates and tuatara
- Crocodilians
o They’re a highly successful group; evolved in the Triassic and survive until today
o Crocodile
o Alligator
o Gharial
o There was a lot of diversity
Some standing
Some adapted to swimming
o The largest crocodilian that lived is sarcosuchus, close to 20m in length
Probably fed on dinosaurs
- Pterosauria
o First reptile group able to achieve true flight
Very closely related to dinosaurs
o Earliest pterosaur are from the late Triassic, but are already adapted for flight
Missing links here
o Transitional form leading to Pterosaurs were able to glide but not capable of flight
(mostly possible)
Such as Draco Lizard, found in the squamates
o Shavovipteryx
Closely related to Archosaurs
It might have been the intermediate stage leading to pterosaurs
It has a membrane between its hind limbs and tail and possible also to its
It’s not an ancestor of Pterosaurs
o Pterosaurs had adaptations for flight, shared with bird
They had hollow bones are necessary to make bone light weight
Hollow bird bones with struts for supports
o While Pterosaur bone had ridges for bone support
o Another adaptation for flight are three distinct gliding membranes
1. From neck region to one of the digits
2. Hind part of the digit
3. Connecting between the inside of the hind leg
These membranes were not just flaps of fragile skin or leather
You're Reading a Preview

Unlock to view full version

Only page 1 are available for preview. Some parts have been intentionally blurred.

They had an inside layer of vascularized muscle and three layers of
closely spaced fibers called actinofibrils
o They have a keel sternum; another adaptation for flying
Flying muscles are attached to the keel sternum
o They have hair like structures;
They have hair like fibrils…not homologous to birds and mammals
It might give the birds the coloration
It suggested they were warm bodies
o Pterosaurs diversified into a large group which are specialized into different
groups, niches, like modern birds
o Pteranodon
Lacked teeth
Fossils show fish in their stomach; thought they were catching fish by
skimming the water instead of going under the water
o Quetzalcoatlus
Largest pterosaurs to fly; largest flying animal with wingspan of 10-11
Fed terrestrially like a stork
o Liaoningoperus
Had strong needle like teeth; up to 4.1 cm
Probably ate fish as well
o Cnetochasma
Finely shaped teeth pointed outwards from jaw forming a basket like
Used their jaw in water to catch small invertebrates
o Pterodaustro
Teeth on the bottom jaw are so fine they form a tight nit comb like a
modern flamingo
Used to filter feed
o Cycnorhamphus
Teeth at the tip of jaw only
May have been used to seek invertebrates in the mud
o Dsungaripterus
A highly specialized jaw
Pointed jaw tip with NO teeth at the tip
This part of the bill was used to pry invertebrates from the rocks along the
edges of the rock
They have knob like flat teeth to crush shellfish
o Aburognathus
Probably fed on airborne insects with its large gaped mouth much like a
Use the mouth to catch moths
o Sexual selection in pterosaurs
You're Reading a Preview

Unlock to view full version