Diversity of Life Part Two

Question 1

What are Acanthodians?

Answer 1

A poorly understood group of extinct jawed fishes that are distinguished by the bony spines projecting in front of their fins.

Question 2

What time period are Acanthodians attributed to?

Answer 2

Among the earliest of the jawed fish, fragmentary remains have been recovered as early as the Upper Ordovician to the Lower Permian.

Question 3

What are Placoderms?

Answer 3

Organisms that bore heavy bony armour on their head and neck, and most of the body was either naked of (less commonly) covered in small scales. Highly successful and diverse taxon, but lasted only 50 million years (went extinct in the late Devonian).

Question 4

What are Chondrichthyans?

Answer 4

The cartilaginous fish (shark rays and skates) that have skeletons of cartilage instead of bone. Includes shark-like forms, freshwater forms, and flattened ray-like forms.

Question 5

When did Chondrichthyans appear?

Answer 5

In the late Silurian, and were diverse in the Palaeozoic.

Question 6

What were the Bony Fishes?

Answer 6

The most numerous, varied, and successful group of aquatic vertebrates. They gave rise to the tetrapods. There were two main groups, the actinopterygians (ray fin) and sarcopterygians (lobe-fin).

Question 7

What were the Ray-Fin Fish?

Answer 7

Actinopterygians; they lacked a muscular base to their paired fins. The fins were made of thin structures supported by thin bony rays. They are the dominate fish in the modern world.

Question 8

What were the Lobe-Fin Fish?

Answer 8

Sarcopterygians; they have sturdy, fleshy, lobe-fins. They also have a pair of openings on the roof of the mouth that lead to the nostrils. They can rise to the surface and breath in air due to functional lungs.

Question 9

What are Conodonts?

Answer 9

Extinct chordates resembling eels, there are tiny fossils known as conodont elements. They are very useful in biostratigraphy, but until recently people were not sure what they belonged to. 1995 South African fossils showed they were chordates. Their exact placement within the chordates is still debated; the elements were thought to have acted similar to teeth.

Question 10

What did Tetrapods evolve from?

Answer 10

Lobe-finned fish.

Question 11

What were the first Tetrapods and what did they give rise to?

Answer 11

The first tetrapods were amphibians, and they gave rise to all of the other groups.

Question 12

What did Amphibians evolve from?

Answer 12

The Rhipidistians.

Question 13

What were the Rhipidistians?

Answer 13

And extinct group of love-finned fish with skulls and limb structures similar to the first amphibians.

Question 14

What are the earliest Amphibian fossils?

Answer 14

From the Devonian of Greenland (including Icthyostega), early ones were freshwater fish eaters and had a mixture of fish and advanced amphibian characters. Had 8 fingers and toes.

Question 15

How many families of Amphians were there in the Carboniferous?

Answer 15

40 families; their diversity of forms and sizes make them difficult to classify. They all returned to water to lay their eggs.

Question 16

What do modern Amphibians belong to?

Answer 16

The Lissamphibia; first appear in the fossil record in the early Triassic.

Question 17

What does the Lissamphibia include?

Answer 17

Anuria (frogs), Urodela (Salamanders), and Caecilians (limbless amphibians).

Question 18

What did the group of amphibians known as reptilomorphs include?

Answer 18

The anthracosaurs. (Amniotes)

Question 19

What evolved the ability to lay eggs on land in the Carboniferous?

Answer 19

The Anthracosaurs. (Amniotes)

Question 20

What did the evolution of the amniote egg allow?

Answer 20

Reptiles and their descendants to colonize a wide range of habitats not accessible to amphibians.

Question 21

What did the amniote egg include?

Answer 21

A yolk that feeds the embryo as well as space for waste and air.

Question 22

When did the earliest amniotes appear?

Answer 22

In the Carboniferous.

Question 23

What were the first amniotes?

Answer 23

Small in size, probably cold blooded - the Hylonous from Nova Scotia.

Question 24

What were the three main clades of amniotes that evolved in the Carboniferous divided by?

Answer 24

The number and position of holes in their skulls.

Question 25

What were the three main clades of amniotes that evolved in the Carboniferous?

Answer 25

Anapside (0), Synapside (1), Diapside (2).

Question 26

What were the Anapsids?

Answer 26

Clade of amniotes that had no opening on the side of their skull. It includes modern turtles (first group to evolve); it was never a diverse group. The greatest diversity was in the Permian. The shell evolved in the Triassic.

Question 27

What were the Synapsids?

Answer 27

Amniote clade; had one opening in the side of the skull. Main radiations were of the pelycosaurs in the early Permian, the therapsids in the later Permian, and the mammals in the Palaeocene.

Question 28

What were the Pelycosaurs?

Answer 28

The first group of synapsids to radiate. Included both herbivores and carnivores. Many evolved to large sizes - a paraphyletic group (A paraphyletic group is a group of organisms that includes an ancestor but not all of its descendants).

Question 29

What were the Therapsids?

Answer 29

Amniote clade; diversified later in the Permian from earlier pelycosaurs. Shorter and more squat that the pelycosaurs. Probably at least partially warm blooded.