Reading:

• Textbook Chapter 15, specifically pages 279-286; 298-307
• Wells, M., 1998. On being both sexes In: Civilization and the limpet, p. 18-27.
• Have a look at a Mesozoic Ocean environment and its organisms.
• Read up on the Upper Cretaceous Pierre Shale, deposited in that Western Interior Seaway.

Both cephalopods and gastropods have a well-developed head, and a commonly coiled shell, which is only in cephalopods subdivided into chambers. The gastropod shell serves as protection, the cephalopod shell as flotation device.

There are 6 different species of Cephalopods available (Jeletzkyes brevis, Jeletzkytes quadrangularis, Eutrephoceras dekayi, Baculites sp. cf ovatum, Placenticeras planum, and Anaklinoceras reflexum), some of which can be seen also in the rock sample.

• One of the 6 is a Nautiloid, the other are ammonites. Which is the Nautiloid? How can you see?
  • E. dekayi is the nautiloid. The larger specimen has a broken shell, and the simple septa are visible.
• For each species, give a short description of important features: type of coiling; the shape of the septa the line of connection to the shell if visible, and type of preservation.
  • E. dekayi: involute spiral, very inflated spiral (cadicone to sphaerocone, text book figure 15.21). Whole shell preserved; recrystallized, somewhat deformed.
  • J. brevis: involute spiral , fine ribs, tubercles pronounced; cross-section rather square; between sphaerocone and platycone (Fig. 15.21); tubercles. For most outer shell preserved, septal sutures not visible. Original material preserved.
  • J. quadrangularis: involute spiral , fine ribs, tubercles pronounced; sphaerocone but with a more square outline (Fig. 15.21); For most outer shell preserved, septal sutures not visible. Original material preserved.
  • Baculites sp.: straight; for most outer shell dissolved, septa visible; note ammonoid sutures.
  • P. planum: involute spriral, flat oxycone; outer shell dissolved, septal sutures well visible, ammonoid, highly complex.
  • A. reflexum: complex shape (heteromorph): shell started out as a snail-like torticone, followed by a straight, then curved section. Outer shell preserved; ribs, some tubercles. Septa not visible.
• Use your textbook (p. 304) to speculate on the mode of life of each.
  • E. dekayi: not known; maybe similar to present Nautilus? Shell does not look like fast mover; slow swimmer-floater, close to bottom; scavenger.
  • J. brevis, J. quadrangularis: probably close to bottom (as numbers 2 and 3 in figure 15.27)
  • Baculites sp.: slow floaters (17 in figure 15.27); maybe scavenger, maybe filter feeders
  • P. planum: fast swimmer; maybe predator
  • A. reflexum: slow moving floater; maybe scavenger, maybe filter feeders

Snails belong to the Phylum Mollusca; gastropods means 'stomach foot', because many crawl on their 'foot'. Most snails have kept their radula, and snails have kept a separate head. Many species are active predators. Quite a few species have lost the external carbonate shell. Snails superficially look like the 'primitive mollusc', but their internal organs are asymmetrical, and are 'twisted' in a process called torsion during their development. Snails occur in fresh water, in the ocean and on land, the only group of the Mollusca to become adapted to land-dwelling (although they still need moist environments). Snail shells show a very wide morphological variability, and many are appreciated by people who like shells (conchologists).

• There are 21 species of snail, all from the Recent, Sanibel Island, Florida. Use your textbook, to see which of these species are Mesogastropods, which Neogastropod. Describe presence/relative size of siphonal canal; is the shell reduced in size (compared to boday) or not.
  • Only the bubble shell is an opisthobranch (p. 279); all others are prosobranchs. Only the turban shell and the button shells are archaeogastropods (p. 284; note complete lack of siphonal tube); all others are meso- and neogastropods (p. 285).
• Speculate and read in textbook about way of life; compare morphology/mode of life.
  • See pages 279-285 of text book)
• For Strombus alatus: compare a small and a large individual, and describe in which aspects the growth of this species is allometric.
  • The herbivorous fighting conch as a large adult has a large flap, sticking out beyond the spiral, with a clear notch.

	siphonal canal?	group of gastropods?
Moon snail (Polinices duplicatus)	no	prosobranch; mesogastropod;predator
Baby ear (Sinum perspectivum)	no	prosobranch; mesogastropod;predator
Lightning whelk (Busycon contrarium)	yes, long	prosobranch; neogastropod;predator (can burrow deeply)
Fig shell (Ficus communis)	yes, long	prosobranch; neogastropod; predator (can burrow deeply)
Auger (Terebra spp.)	short	prosobranch, neogastropod, predator on small clams
Cerith (Cerithium spp.)	no	prosobranch; mesogastropod; predator on burrowing small clams
Nutmeg (Cancellaria reticulata)	yes, short	prosobranch; neogastropod predator
Bubble shell (Bulla striata)	no; reduced shell	opisthobranch; planktonic (shell reduced); predator
Fighting conch (Strombus alatus)	yes, long	prosobranch, mesogastropod, see siphonal  notch in large specimens; herbivore
Slipper shells (Crepidula fornicata)	no	prosobranch, mesogastropod;grazes algae from rocks
Lettered olive (Olivia sayana)	yes	prosobranch; neogastropod deep burrower; eats infaunal clams
Button shell (Modulus modulus)	no	prosobranch; archaeogastropod; algae grazer
Apple murex (Phyllonotus pomum)	yes, long	prosobranch, neogastropod;predator
Lace Murex (Chicoreus florifer)	yes, long	prosobranch,neogastropod;predator
Chestnut turban (Turbo castanea)	no	prosobranch,archaeogastropod; algae grazer on rocks
worm shell (Vermicularia sp.)	no	prosobranch; neogastropod;free-moving on rocks; graze
Horse conch (Pleuroplaca gigantea)	yes	prosobranch; neogastropod; predator (pen-shells)
Banded tulip (Fasciolaria lilium)	yes	prosobranch; neogastropod;active predator
Crown conch (Melongena corona)	yes	prosobranch; mesogastropod;grazes algae
Pear whelk (Busycon spiratum)	yes	prosobranch; neogastropod;predator
Florida cone (Conus floridanus)	yes	prosobranch; neogastropod;predator