lab/lecture 12: cephalopoda 2

Question 1

Describe (Subclass) Ammonoidea.

Answer 1

(Phylum Mollusca, Class Cephalopoda, Subclass Ammonoidea) Extinct, coiled, chambered shells, often ribbed; ventral siphuncle; complex sutures (goniatitic, ceratitic, ammonitic). Devonian–Cretaceous.

Question 2

Describe goniatitic sutures.

Answer 2

Simple, rounded saddles and pointed lobes; seen in early ammonoids (Devonian–Permian).

Question 3

Describe ceratitic sutures.

Answer 3

Rounded saddles, lobes with small crenulations; typical of Ceratida, especially Triassic ammonoids.

Question 4

Describe ammonitic sutures.

Answer 4

Complex, highly frilled saddles and lobes; seen in Jurassic–Cretaceous ammonoids.

Question 5

Describe (Order) Goniatida.

Answer 5

(Subclass Ammonoidea) Devonian–Permian; simple goniatitic sutures, round saddles, pointed lobes.

Question 6

Describe (Order) Ceratida.

Answer 6

(Subclass Ammonoidea) Carboniferous–Triassic; round saddles, serrated lobes, ceratitic sutures.

Question 7

Describe (Order) Ammonitida.

Answer 7

(Subclass Ammonoidea) Permian–Cretaceous; folded saddles and lobes, fractal patterns, ammonitic sutures.

Question 8

Describe ornamentation in ammonoids.

Answer 8

Many had ribs, spines, tubercles, and keels; some had tricarinate venters with a true keel and side furrows.

Question 9

Describe (Subclass) Coleoidea.

Answer 9

(Phylum Mollusca, Class Cephalopoda) Includes squid, octopus, cuttlefish; internal or no shell; excellent vision, smart; Mississippian–Recent.

Question 10

Describe (Order) Belemnoida.

Answer 10

(Subclass Coleoidea) Mississippian–Cretaceous; internal shell with phragmocone, pro-ostracum, and rostrum (guard); bullet-shaped fossils.

Question 11

Describe (Order) Teuthoidea.

Answer 11

(Subclass Coleoidea) Jurassic–Recent; squid; internal horny pen (gladius); no shell or rostrum.

Question 12

Describe (Order) Sepioida.

Answer 12

(Subclass Coleoidea) Jurassic–Recent; cuttlefish; shield-like internal “cuttlebone” skeleton; Spirula has ventral siphuncle and coiled shell.

Question 13

Describe (Order) Octopoida.

Answer 13

(Subclass Coleoidea) Cretaceous–Recent; octopus; no internal shell; some females secrete a delicate brood pouch shell.

Question 14

What’s the main taxonomic feature in ammonoids?

Answer 14

The suture line — the pattern where septa meet the inner shell wall.

Question 15

What is a saddle vs. a lobe on ammonoid sutures?

Answer 15

Saddle: curve pointing toward head; Lobe: curve pointing away from head.

Question 16

How did ammonoid sutures evolve over time?

Answer 16

Simple (goniatitic) → moderately complex (ceratitic) → highly complex (ammonitic), then some reversal in later Cretaceous.