Lecture 15 - Mollusks III

Question 1

Class Cephalopoda:

Answer 1

Free-swimming mollusks with a highly developed nervous system; they have a highly adapted foot that is modified into many arms for use in predation; they have two eyes, a chitinous beak & a radula; most forms have a chambered, aragonite shell (the “phragmocone”), with a tube-like siphuncle connecting the many chambers; all members of the class are predators; exclusively marine; excellent fossil record of the shelled forms

Question 2

Class Cephalopoda Geologic Range

Answer 2

Late Cambrian to Recent

Question 3

Six main Subclasses of Class Cephalopoda:

Answer 3

Subclass Nautiloidea
Subclass Endoceratoidea
Subclass Actinoceratoidea
Subclass Bactritoidea
Subclass Ammonoidea
Subclass Coleoidea

Question 4

Subclass Nautiloidea:

Answer 4

Phragmocone with simple, dish-shaped septa; small siphuncle through the center of the septa; cameral deposits common in fossil forms; includes orthocones, cyrtocones, gyrocones & nautilocones; includes the modern “chambered nautilus”

Question 5

Subclass Nautiloidea Geologic Range

Answer 5

Late Cambrian to Recent

Question 6

Subclass Endoceratoidea:

Answer 6

Phragmocone with simple, dish-shaped septa; large siphuncle located at shell margin; characteristic cone-in-cone siphuncular deposits (“endocones”); usually orthocones

Question 7

Subclass Endoceratoidea Geologic Range

Answer 7

Ordovician to Silurian

Question 8

Subclass Actinoceratoidea:

Answer 8

Phragmocone with simple, dish-shaped septa; large siphuncle located at shell margin; characteristic ring-like siphuncular deposits (“annular deposits”); usually orthocones

Question 9

Subclass Actinoceratoidea Geologic Range

Answer 9

Ordovician to Mississippian

Question 10

Subclass Bactritoidea:

Answer 10

Phragmocone with simple, dish-shaped septa displaying a deep ventral lobe; small siphuncle located at shell margin; usually orthocones

Question 11

Subclass Bactritoidea Geologic Range

Answer 11

Silurian to Triassic

Question 12

Subclass Ammonoidea:

Answer 12

Phragmocone with highly corrugated septa, which produce geometrically complex sutures; small siphuncle located at shell margin; usually nautilocones, but some Cretaceous forms took on various other shapes (“heteromorphs”)

Question 13

Subclass Ammonoidea Geologic Range

Answer 13

Devonian to Cretaceous

Question 14

Subclass Coleoidea:

Answer 14

Cephalopods with either no shell or an internal shell; includes the modern octopus, squid, cuttlefish, and spirula; also includes the fossil belemnites

Question 15

Subclass Coleoidea Geologic Range

Answer 15

Devonian to Recent

Question 16

Visceral Mass:

Answer 16

Vital organs are located in the mass behind the head

Question 17

Gills:

Answer 17

One pair of leaf-like gills in coleoids, and 2 pairs of leaf-like gills in nautioloids

Question 18

Arms:

Answer 18

Octopus, squid & cuttlefish have 8 stout arms lined with suction cups; chambered nautilus has about 90 arms covered with a sticky secretion but no suction cups

Question 19

Tentacles:

Answer 19

Squid & cuttlefish have 2 long tentacles with suction cups only at the very ends

Question 20

Exhalent Siphon (=Hyponome=Funnel):

Answer 20

Tubular fold in the mantle, from which water is forcibly expelled to provide a means of locomotion (“jet propulsion”)

Question 21

Eyes:

Answer 21

One pair of eyes with a single lens-retina system

Question 22

Beak:

Answer 22

A chitinous, parrot-like beak in the mouth for biting and tearing food.

Question 23

Five common coleoids:

Answer 23

Octopus, Squid, Cuttlefish, Spirula, Belemnites

Question 24

Octopus:

Answer 24

Round visceral mass; 8 arms; beak

Question 25

Octopus Geologic Range

Answer 25

Recent

Question 26

Squid:

Answer 26

Cigar-shaped vsceral mass; 8 arms & 2 tentacles; beak; an internal chitinous shell (“pen”)

Question 27

Squid Geologic Range

Answer 27

Recent

Question 28

Cuttlefish:

Answer 28

Sausage-shaped