Nautiloids and Ammonoids

Question 1

What is their class and phylum

Answer 1

Cephlapoda

Mollusca

Question 2

What shape shell does it live in (Nautilus)

Answer 2

Conical

Question 3

What part of the shell does the organism grow in (Nautilus)

Answer 3

Final body chamber

Question 4

What is the wall called that separates the walls (Nautilus)

Answer 4

Septum

Question 5

What are the chambers joined by and what is it used for (Nautilus)

Answer 5

Siphuncle
Used to adjust the proportion of gas and liquids within the chambers which helps control the animals position in the water column

Question 6

What are the forms of coiling

Answer 6

Involute- The inner coils are almost hidden by the last one (shown by Nautilus)
Evolute-Means that all the earlier coils can be seen, and shows off the earlier coils and a wide umbilicus (common in ammonoids)
Planispiral- means that the shell is coiled in a single plane

Question 7

What do some have (Ammonoids)

Answer 7

A keel for stability

Question 8

Nektonic - lateral movement (Ammonoids)

Answer 8

Tentacles are used in a gentle swimming motion
Jet propulsion - The water which is circulated through the mantle for respiration can be forcibly expelled through a tube beneath the tentacles called the funnel

Question 9

Nektonic - vertical movement (Ammonoids)

Answer 9

Empty chambers all have a mix of gas and liquid, the gas is nitrogen rich. The liquid of gas ratio can be adjusted using the siphuncle

Question 10

Hunter killer (Ammonoids)

Answer 10

Evidence points to them being predatory, hunting their prey

Question 11

What does the suture line mark (Cephalopod)

Answer 11

The wall of the chamber

Question 12

What does the septum fuse with

Answer 12

The inside of the shell

Question 13

What is the most acceptable explanation for changes in the suture types

Answer 13

Linked with strength and the ability to exploit different environments, the septum had to withstand high pressures so were simply domed, but later forms had crenultions to give more strength

Question 14

What changed in the later forms of the Ammonites septal necks

Answer 14

Face towards the aperture :)

Question 15

What is the difference in Nautiloid and Ammonite siphuncle

Answer 15

Ammonite siphuncle is closer to the edge

Question 16

Difference in external structure in Nautiloid and Ammonites

Answer 16

Nautiloids were smooth shelled while Ammonites show a variety of ornament (some were streamline, some were ribbed and tubercles for defense)

Question 17

What are Heteromorphs

Answer 17

Forms that exhibit loose coiling in more than one plane ( these are often referred to as the uncoiled Ammonites) they are most likely like this to exploit different environmental niches.