Class Cephalopoda

1
Phylum Mollusca
Class Cephalopoda
Geo-range Cam-Rec.
Pearly nautilus A favorite in Shell shops
Octopus in the rocks
2
Most cephalopods we are familiar with dont have
a shell But we assume they all had this type of
soft parts These organisms were highly advanced
with eyes, jet propulsion, Jaws and tentacles
3
Class Cephalopoda Cam. Rec. Free swimming
molluscs with or without CaCO3 shells, usually
some number of tentacles Subclass Nautiloidea
Cam.-Rec. Mostly paleozoic, with shells 8
suborders, only one still living, has central
siphuncle Subclass Dibranchiata
Miss.-Rec. Includes most of the modern forms Such
as squid and octopus, few fossil Forms Subclass
Ammonoidea Dev. Cret. Only group that is
extinct, siphuncle Can be either dorsal or
ventral, as in Nautiloids these all possess
carbonate shells
4
Subclass Nautiloidea Cam. Rec. All possess a
central siphuncle and shell,Variety of shell
morphologies and simple septa Order
Ellesmeroceroida Cam.-Ord. Curved shells
Order Michelinoceroida Ord.-Trias.
Curved or straight shells Order Ascoceroida
Ord. Sil Slightly curved shells Order
Oncoceroida Ord.-Dev. Strongly curved to
straight shells Order Endoceroida Ord.
Mostly straight shells Order Actinoceroida
Ord.- Penn. Straight shells Order
Discosoroida Ord. Dev. Curved shells
Order Nautiloida Ord. Rec. Curved shells,
only order still extant
5
What makes this group Distinct are the septa That
divide the shell into Chambers Also the organism
has A siphuncle that the Animal can use to
regulate Pressure inside the shell chambers
6
Belemnoid
rostrum
Straight shelled Nautiloid
Large siphuncle and Endcone of an
Endoceroid Nautiloid
Ascoceroid Nautiloid With truncated shell
Planispiral coiled Nautiloid Pearly Nautilus
7
General geological Ranges for each of the Major
subclasses- Note that Dibranchiata Are now the
most Common but the latest To
evolve-mostly unshelled
8
Many types of coiling or not Coiling as the case
may be The difference between these And
gastropods is that these Have septa-I.e.
chambers-while The snails dont The septa are
represented by Sutures on the outer part of
the shell
9
Nautiloids have a Number of internal Structures
used for Classification-one Here is cameral
deposit
Cameral Deposits may act as A ballast or
Balancing mechanism
Cameral deposits Are infillings Around the
Siphuncle and up the Sides of the chambers
10
Siphonal deposits Can be diagnostic To help
separate Genera, families, species The great
thing about these Is that you can see
them Clearly in x-sections of The siphuncle and
they are distinctive
11
Evolution of the Ascoceroids
Order Ascoceroida Ord. Sil
5
4
3
2
1
12
Oncoceroids-short curved shells and distinctive
Actinosiphonate deposits
Order Oncoceroida Ord.-Dev.
13
Note the calcified siphuncle Again another
distinctive Feature that helps to
differentiate This group
Order Endoceroida Ord.
14
Thick annulosiphonate Deposits characterize The
order Ascoceroida
15
Shelbyoceras sp. Very simple form
Only order in the Cambrian
Order Ellesmeroceroida Cam.-Ord.
16
Centrotaphyceras sp
By this time all Nautiloid orders are present
17
Straight shelled Nautiloid with Well
developed Cameral deposits
18
Cystoceras sp.
19
Lower Miss. nautiloid
Only 5 orders Left by the Devonian
20
Order Michelinoceroida Ord.-Trias.
Order Actinoceroida Ord.- Penn.
Order Nautiloida Ord. Rec.
Only three Orders left by The end of the Paleozoic
21
Some Mesozoic Nautiloids
Hamites rotundas Jurassic
Cosmoceras sp. Jurassic
Order Michelinoceroida Ord.-Trias.
Order Nautiloida Ord. Rec.
Only Nautiloida persists Through the Mesozoic to
today
Hibolites jaculoides Cretaceous
22
Subclass Dibranchiata Miss.-Rec. Has
internal shells or no shell Order Septoida
Jur.-Rec. Internal flat shield
containing remnants of Chambers, 10
tentacles, cuttlefish Order Teuthoidea
Jur.-Rec. Shell consisting of horny pen,
10 tentacles, Squids Order
Octopoida Cret. Rec. No shell, 8
tentacles, Octopus Order Belemnoida Miss.
Eoc. Chambered phragmocone (shell)
surrounded By a counterweight
(rostrum), Only group That leaves a
distinctive fossil record from this
Subclass
23
Morphological Features for belemnoids
24
Geologic ranges Of some common Dibranchiata
Fossil forms
25
The cuttlefish A common delicacy In the
Mediterranean Area Has an internal shell With
membranes on The outside
26
Soft parts Of Sepia Its shell is Almost
a bivalve
27
Oldest known octopus Fossil from Palestine Upper
Cretaceous Argonauta-female has Shell Pliocene
of Italy
28
The success of the Dibranchiata over the early
shelled Groups is perhaps the most striking
example in the invertebrate World of speed and
quickness being a much larger asset Than
Carrying around a thick shell.