Lecture 4: Vertebrate Origin and Evolution: Fish through Tetrapods

Comprehensive vocabulary flashcards covering the origin of vertebrates, major jawless and jawed fish lineages, tetrapod transitions, skull fenestrations, and mammalian/avian taxonomy based on Chapter 3 lecture notes.

Who coined the term "Vertebrate Story”?

Alfred Romer (paleontologist / anatomist). Vertebrates evolved ~0.5 billion years ago between the Cambrian period (542 mya) and the Ordovician period (444 mya).

Sequence of appearance

Agnathans “jawless”, Gnathostomes “jawed” (Chondrichthyans- “cartilaginous fish” and Osteichthyans- "bony fish"), followed by early tetrapods.

Chondrichthyans

are a class of jawed vertebrates that includes sharks, rays, and skates, characterized by a cartilaginous skeleton.

Osteichthyans

are a diverse group of jawed vertebrates known as "bony fish". They have a skeleton made primarily of bone and include both ray-finned and lobe-finned fish.

Tetrapods

are vertebrates that have four limbs, including amphibians, reptiles, birds, and mammals. They evolved from lobe-finned fish and adapted to life on land.

Anamniotes

lack extra-embryonic membrane. ex) labryinthodonts and amphibians

Amniotes

extra membrane. They are vertebrates that possess extra-embryonic membranes, allowing for reproduction in a terrestrial environment. This group includes reptiles, birds, and mammals.

Extinction #1

Permian. ~250 mya. Pangea merge. Volcanoes lead to CO2 and temperature increases, and Oxygen decrease.

Extinction #2

Cretaceous. ~66 mya. Asteroid.

Prevertebrates and earliest agnathan vertebrates

Pikaia, Haikouella, Myllokummingia and Haikouichthyes

label prevertebrate phylogeny

Pikaia

Early Cephalochordate or Prevertebrate? in Burgess Shale 503 mya (mid-Cambrian). 5 cm long. segmentation protects spinal cord.

Haikouichthyes

possession of protovertebral column, notochord with cartilaginous composition

Haikouella

early jawless vertebrates, Includes Haikouichthys and Myllokunmingia

Myllokunmingia

early jawless vertebrates

Agnthans (jawless fish)

Cyclostomata

Condodonts

Ostracoderms

Agnathans Phylogeny tree

Gnathostomes (Jawed)

• Placoderms

• Chondrichthyans

  • Elasmobranchs

  • Holocephali

• Acanthodians

• Osteichthyans (bony fish)

  • Actinopterygians

  • Sarcopterygians

• Tetrapods

Cyclostomata

A group of jawless fish characterized by round mouths, comprising Myxinoidea (hagfish) and Petromyzontida (lampreys).

Myxinoidea → Hagfishes ("slime eels")

(Bdellostoma) release slime that helps break down their food. Agnathans

Conodonts

Extinct agnathans known for specialized micro-fossilized dental elements, including P, S, and M elements.

Ostracoderms

Jawless fish characterized by armored bony plates on their skin. dorsal eyes, lobe-like pectoral fin. Cephalospidomorpha and Pterospidomorpha are Ostracoderms.

Gnathostome phylogeny

Osteichthyan phylogeny

Achinistia Coelocanths phylogeny

Pterospidomorpha

A clade of ostracoderms characterized by bony armor surrounding the mouth.

Cephalaspidomorpha

A clade of ostracoderms featuring bony armor over the mouth, dorsal eyes, and lobe-like paired pectoral fins.

Gnathostomes

A major evolutionary lineage of vertebrates defined by the presence of jaws.

Placoderms

Early jawed fish possessing armor-plated or bony skin.

Chondrichthyans

Cartilaginous fish possessing serial replacement teeth, divided into Elasmobranchs (sharks, skates, rays) and Holocephali (chimaeras/ratfish).

Acanthodii

An extinct clade of jawed fish known as spiny forms.

Osteichthyans

Bony fish divided into two major groups: Actinopterygii (ray-finned) and Sarcopterygii (lobe-finned).

Actinopterygians

Ray-finned bony fish encompassing primitive Palaeonisciformes and advanced Neopterygii.

Sarcopterygians

Lobe-finned or fleshy-finned bony fish including Actinistia, Dipnoans, and Rhipidistians.

Actinistia

Deep-sea coelacanths with cosmoid scales and a divided diphycercal tail, exemplified by the "living fossil" Latimeria.

Dipnoans

Lungfish that inhabit shallow waters and possess paired lungs for breathing air.

Rhipidistians

Lobe-finned fish within the labyrinthodont lineage ancestral to land-dwelling tetrapods. anatomy of animal that can go from sea to land.

Latimeria

“Living Fossil”of the coelacanth, a deep-sea fish thought to be extinct until its discovery in 1938. It possesses unique features such as cosmoid scales and a lobed fin structure.