Sarcopterygii

It All Started with a Fish

Class Sarcopterygii

Class Sarcopterygii

• “Lobe-finned”
• sárx = flesh (Greek)
• ptérux = wing/fins (Greek)
• Group includes tetrapods
• These notes will discuss the early branches that are still fully aquatic
• Have paired and median fins present like Actinopterygiians
• What makes these guys unique is the single basal skeletal element in those paired appendages with short dermal rays
• The muscles that move these paired appendages are on the appendage, not in the body like the other fishes.

Class Sarcopterygii

• Unlike other fishes we’ve seen:
• They have double circulation with pulmonary and systemic circuits.
• The swim bladder is vascularized, used for both respiration (like a lung) and buoyancy.

Class Sarcopterygii

• Osmotic regulation is like that of the Actinopterygiians
• Lateral-line System
• Sexes are separate and fertilization can be internal or external
• 3 subgroups

Class Sarcopterygii -

Subclass Actinistia

• Means “ray group”
• Only 2 living species
• Coelacanths
• Were believed to have been extinct since the end of the Cretaceous period
• 23 December 1938, the first specimen was found off the east coast of South Africa, among the catch of a local angler, by museum curator Marjorie Courtenay-Latimer

https://www.bbc.com/future/article/20240507-the-deep-ocean-photographer-that-captured-a-living-fossil

Sarcopterygii - Order Dipnoi

• Means “double breathing”
• Lungfish
• Only 6 known extant species
• only in Africa, South America, and Australia
• Highly specialized respiratory system
• lungs of lungfish are subdivided into numerous smaller air sacs, maximizing the surface area available for gas exchange
• homologous to the lungs of tetrapods

Superclass: Tetrapodomorpha

• Sister group to Sarcopterygii
• Means “four feet/limbs”
• Includes all the groups we will look at from now on