Porifera
Precambrian-Recent
Geologic range:
Class Calcarea: Devonian-Recent
Class Hexactinellida: Cambrian-Recent
Class Demospongea: Cambrian-Recent
Class Sclerospongia: Ordovician-Devonian
The fossil record of sponges is quite spotty because sponges are often soft and cellular, making sponges
rarely preserved. However, some sponges have a rigid skeletal framework and this calcareous or siliceous
framework, or isolated spicules are more commonly preserved.
Morphological features:
Sponges are the simplest forms of multicellular life. They possess no organs and the skeleton has
many pores and canals lined with cells. Each of the cells create a current with a whip like flagellum to
move water and food particles into the sponge. The skeleton itself is composed of organic substance
called spongin with needle-like elements known as spicules. The spicules are the only part fossilized and
are commonly composed of calcite or silica, which are interconnected to provide support.
Habitat:
Most species prefer shallow marine waters; however, some modern sponges are found in deep waters.
Cnidaria
Precambrian-Recent
Geologic range:
Class Hydrozoa: Cambrian-Recent
Class Scyphozoa: Precambrian-Recent
Class Anthozoa: Ordovician-Recent
Morphological characteristics:
Common cnidarians include jellyfish, sea anemones, and coralsCnidarians are slightly more complex
than sponges. They have true tissues but no discrete organs. Most cnidarians are soft-bodied, except for
corals which have a calcareous skeleton, making them difficult to fossilize. Their major characteristic is
nematocysts, which are stinging cells used to paralyze prey or predators.
Habitat:
Cnidarians are almost exclusively marine. They are typically either sessile (attached) most abundant in
shallow waters (however sea anemones can be found in the deepest parts of the ocean) or free-floating
usually found at the surface.
Brachiopoda
Cambrian-Recent
Geologic range:
Class Inarticulata: Cambrian-Recent
Class Articulata: Cambrian-Recent
Morphological features:
Brachiopods have two calcite valves surrounding the soft body. The plane of symmetry for most
brachiopods runs through both shells so that one half of the shell is the mirror image of the other. One
valve is larger than the other (called the ventral or pedicle valve). The two valves are attached at a hinge.
The hinge teeth and hinge line can be used to identify particular types of brachipods.
Habitat:
Brachiopods are exclusively benthic marine, living primarily on the shallow shelf and in epicontinental
platform seas.
Bryozoa
Ordovician-Recent
Geologic Range:
Class Stenolaemata: Ordovician-Recent
Class Phylactolaemata: Recent
Class Gymnolaemata: Ordovician-Recent
Morphological Features:
Bryozoans are colonial marine organisms that make a calcareous skeleton. Bryozoans are commonly
mistaken for corals; however, bryozoans have smaller holes for the individual animal. They also lack the
radial septa characteristic of coral skeleton. The soft parts of the animal are not preserved, but the details
of the calcareous colonial skeleton are.
Habitat:
Bryozoans are found in modern oceans at all latitudes and as deep as 5500m, but most abundant in
shallow, tropical seas. Most species require a hard substrate to attach.
Mollusca
Cambrian-Recent
Geologic Range:
Class Monoplacophora: Cambrian-Recent
Class Polyplacophora: Ordovician-Recent
Class Scaphopoda: Ordovician-Recent
*Class Bivalvia: Cambrian-Recent
*Class Gastropoda: Cambrian-Recent
Class Rostroconcha: Ordovician-Silurian
*Class Hyolitha: Cambrian-Permian
Class Cephalopoda: Cambrian-Recent
*major classes
Morphological features:
Mollusks include clams, snails, nautiloids, ammonoids, chitons, and several minor groups. Most
mollusks have a calcareous shell, which is well fossilized. They are bilaterally symmetrical with a
muscular foot, mantle (secretes shell) and radula. Bivalves have, as the name suggests, two valves
surrounding the soft body.
Habitat:
Mollusca are found in marine, freshwater and land environments. Most are marine.
Arthropoda
Cambrian-Recent
Geologic Range:
Class Trilobita: Cambrian-Permian
Class Crustacea: Cambrian-Recent
Class Uniramia: Cambrian-Recent
Class Chelicerata: Cambrian-Recent
Class Arachnida: Ordovician-Recent
Habitat:
Arthropods are the most diverse phylum and are found in marine, freshwater and land environments.
They inhabit all extremes (deep ocean, hottest deserts and coldest ice).
Morphological Features:
Arthropods include insects, crabs, spiders, and trilobites. Arthropods have segmented bodies and
jointed appendages. They possess an exoskeleton composed of chitin and molt or shed the exoskeleton in
order to grow larger. Even though they possess an exoskeleton, arthropods have a relatively poor fossil
record because of the organic chitinous cuticle. Only the arthropods with mineralized skeletons such as
the calcified triobites and ostracodes have a good chance of being preserved.
Echinodermata
Early Cambrian-Recent
Geologic Range:
*Class Crinoidea: Cambrian-Recent
Class Paracrinoidea: Early Ordovician-Early Silurian
Class Eocrinoidea: Early Cambrian-Late Silurian
*Class Blastoidea: Middle Ordovician-Late Permian
Class Stylophora: Middle Cambrian-Pennsylvanian
*Class Ophiuroidea: Early Ordovician-Recent
*Class Asteroidea: Early Ordovician-Recent
*major classes
Class Holothuroidea: Middle Cambrian-Recent
Class Helicoplacoidea: Early Cambrian
Class Edrioasteroidea: Early Cambrian-Late Pennsylvanian
Morphological Features:
Common echinoderms include sea stars, sea urchins, and sand dollars. Echinoderms typically have
penta-radial symmetry. Most echinoderms have a skeleton with individual plates (ossicles) made up of
single crystals of high-magnesium calcite. Some even have spines on their external ossicles. One of the
most distinctive features is their internal water vascular system used for locomotion, feeding and
respiration. Echinoderms have tube feet used for locomotion and feeding.
Habitat:
Echinoderms are exclusively marine. They can be found in shallow waters as well as the deep abyssal
seafloor.
Chordata
Subphylum: Vertebrata
Late Cambrian-Recent
Geologic Range:
Class Agnatha: Late Cambrian-Recent
Class Plaodermi: Early-Late Devonian
Class Chondrichthys: Middle Devonian-Recent
Class Acanthodii: Middle Silurian-Early Permian
Class Osteichthyes: Middle Devonian-Recent
Class Amphibia: Early Carboniferous-Recent
Class Reptilia: Middle Carboniferous-Recent
Class Aves: Upper Jurassic-Recent
Class Mammalia: Late Triassic-Recent
Morphological Features:
Common vertebrates include fish, birds, dinosaurs and mammals. Characteristics of vertebrates are
they have a notochord, nerve cord, vertebrae (either bone or cartilage), and pharyngeal gill slits – at least
sometime in their development.
Habitat:
Vertebrates inhabit marine, freshwater, terrestrial and aerial environments.
Phylogenetic relationships