Nautiloids and Ammonoids Flashcards
What is their class and phylum
Cephlapoda
Mollusca
What shape shell does it live in (Nautilus)
Conical
What part of the shell does the organism grow in (Nautilus)
Final body chamber
What is the wall called that separates the walls (Nautilus)
Septum
What are the chambers joined by and what is it used for (Nautilus)
Siphuncle
Used to adjust the proportion of gas and liquids within the chambers which helps control the animals position in the water column
What are the forms of coiling
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
What do some have (Ammonoids)
A keel for stability
Nektonic - lateral movement (Ammonoids)
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
Nektonic - vertical movement (Ammonoids)
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
Hunter killer (Ammonoids)
Evidence points to them being predatory, hunting their prey
What does the suture line mark (Cephalopod)
The wall of the chamber
What does the septum fuse with
The inside of the shell
What is the most acceptable explanation for changes in the suture types
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
What changed in the later forms of the Ammonites septal necks
Face towards the aperture :)
What is the difference in Nautiloid and Ammonite siphuncle
Ammonite siphuncle is closer to the edge