WEB TAXONOMY

The following is a work in progress. It is intended as a guide to major groups of invertebrates we will discuss in this course with web links. Check back from time to time as I add more links. As we discuss some significant genera of these phyla I will add them to the list. 

I. "Phylum" Arthropoda (Crabs, Spiders, Insects, etc.) (pp. 252-279)

A. Subphylum Chelicerata or Cheliceratamorpha- Order (Chelicerates & kin) (p. 265-270))

• body divided into prosoma (head and thorax) and opisthosoma (abdomen)
• a pair of pincers (chelicerae) in front of the head
• no antennae
• four pairs of uniramous legs on the head
• Includes mites, ticks, scorpions, spiders, horseshoe crabs, eurypterids and much more.

Subclass Eurypterida (water scorpions)- Mid. Ordovician to Permian
largest arthropods of all time
major predators of the Paleozoic

B. Subphylum Crustacea or Crustaceamorpha (Crustaceans)- Cambrian to Recent (p. 270-279)

• Mainly aquatic arthropods with specialized appendages that include: 2 compound eyes that are often stalked, gills, mandibles, and two pair of antenna.
• This group is extremely diverse with over 35,000 living species.
• all share the possession of two pairs of attennae during some stage of their life cycle
• three pairs of appendages (maxillae and two sets of mandibles)

Class Malacostraca (Devonian-Recent) (pp. 271-272)
•  Includes crabs, krill, lobsters, shrimp, pill bugs, and more!
• 20,000 species described

Order Decapoda (Devonian-Recent)
• Contains some the largest and most highly specialized crustaceans.
• Named for their five pairs of legs (first three pairs of appendages modified into feeding structures (maxillipeds)
• 20 body segments (6-8-6)
• Their fossil record is described as being poor, however few studies document the ubiquitous, highly resistant fragments (mostly pincers).  This order includes: shrimp crayfish, lobsters, and crabs.
Class Maxillopoda (pp. 272-276)
• Includes ostracods, copepods, barnacles, and others.

Subclass Cirripedia (Middle Cambrian- Recent)
• Barnacles and relatives, 1000 species
• hermaphroditic, internal fertilization
• acorn barnacles have six side and base plates and four lid plates

Ostracoda (Cambrian-Recent)

• 8000 living species
• carapace with five pairs of appendages on the head and 1-3 pairs on the body
• most microscopic to 35mm in size, some Paleozoic ones to 80mm

C. Subphylum Tracheata or Uniramia (Insects, millipedes, centipedes & kin) (pp. 276-279)

• Uniramous appendages with only one branch
• 75% of all animal species, 870,000 described species but only 30,000 fossil species
• first in Middle Cambrian, rare until Middle Silurian
• First butterflies in the Jurassic

Note: During our Paleozoic field trip, we will not encounter many whole trilobites.  Many of our sites do contain common to even abandant trilobite fragments. Most of these are from the cephalon which often separates along cephalic sutures. The free and fixed checks are the most common elements found.

Trilobites have three distinct segments (head, thorax, and pygidium),  a pair of antennae, and biraous limbs. Calcified exoskeleton.

1. Order Agnostida (Cambrian-Ordovician)
2. Order Polymerida (Cambrian-Permian)

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II. Phylum Brachiopoda

A. Subphylum Linguliformea (L. Camb. to Recent) (Inarticulate)

• valves not hinged by teeth and sockets
• shell organophosphatic

1. Class Lingulata  (L. Camb. to Recent)
Chitinophosphatic or calcareous shells lacking structures homologous with tooth and socket articulation.  The valves are attached by muscles.  This class comprises only 5% of the known genera, but was important during the Cambrian.
    Lingula (extant)

1. Class Strophomenata (M. Cambrian to Triassic)

• Order Strophomenida (Ordo.-Triassic)
• pseudopunctate with a wide hinge line
• one valve generally concave and other convex, some plano-convex with long hinge lines
• Shells are  and a bilobed cardinal process.
• the largest and most diverse brachiopod order.
• smooth or surface costate
• simple or reduced teeth
• Rafinesquina
• Strophomena
• Order Productida (L. Devonian to Permian)
• usually plano-convex
• deep mantle cavity
• interareas reduced or lacking
• some even conical
• spines along posterior margin or over whole shell
• Productus

• Order Spiriferida (M. Ordo.-Permian)
• contain a spiral brachidium, laterally directed
• biconvex
• usually long hinge line
• well-developed interareas
• with a prominent fold and sulcus and well developed plications
• Interarea limited to the ventral valve.
• Spirifer
• Mucrospirifer
• Brachyspirifer
• Order Terebratulida  (L. Dev.-Recent)
• shell punctate
• short hinge line
• round and large foramen in the beak region
• looped brachidium
• most subcircular to elongate
• smooth biconvex shells with short non-strophic hinge
• Terebratula
• Order Pentamerida (M. Cam.- U. Dev.)
• biconvex impunctate
• short hinge line
• open delthyrium
• well-developed spondylium in beak of pedicle valve
• Pentamerus
• Order Orthida (L. Cam.-U. Perm.)
• subcircular to semielliptical
• generally wide hinge line
• generally unequal biconvex wth radial ribs
• have brachiophores
• simple or lobate cardinal process
• distinct interarea
• Platystrophia
• Herbetella
• Order Rhynchonellida (M. Ordo.-Recent)
• biconvex
• generally strongly plicate shells
• short hinge line and prominent pedicle beaks
• shells have well-developed plications that meet along a zigzag plane of commissure.
• the hinge is curved without an interarea.
• Rhynchonella

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III. Phylum Bryozoa ("Moss animals") (pp. 144-156)

• Filter feeding, colonial metazoans cosisting of linked zooids.
• Can be encrusting, creeping erect or in chains.

A. Class Stenolaemata (Ordovician-Recent)

Order Fenestrata (L. Ordo. to U. Permian) Zoaria net-like with unilaminate branches, autozooids short and commonly with hemisepta.
1. Fennestella- lacy bryozoans, colonies fan or funnel-shaped. Nearly parallel slender branches joined by cross bars. Zooecial aperatures in two rows along each branch. First occurred in the Middle Silurian and abundant through remainder of the Paleozoic.
2. Archimedes- also lacy bryozoan but with a spiral axis (hence named after Archimedes screw). Solid screw-like support. Particularly abundant in the Mississippian.

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IV. Phylum Cnidaria

• Metazoans with radial or biradial symmetry, nematocysts, and a calcareous or organic skeleton.  They may be solitary, but most are colonial.
• Often polymorphic with alternate polyps (attached forms) and medusae (free swimming forms).
• Includes the classes Hydrozoa (Hydra, hydracorallines), Scyphozoa (jellyfish), and Anthozoa.

A. Class Anthozoa (Corals, Sea Anemones, Gorgonians and sea pens)- PreCamb. to Recent

Corals, sea-anemones, gorgonians, sea pens.  Exclusively marine polyps (no medusoid stage).

Subclass Actinaria (Sea Anemones)

Subclass Octocorallia (Soft Corals)

Order Alcyonacea (Soft corals)
Order Gorgonacea (Sea fans, sea whips)
1. Gorgonia
Order Helioporacea (Blue coral)
Order Pennatulacea (Sea pens)
Order Stolonifera (Organ-pipe corals)
1. Tubipora
Order Telestacea (Soft corals)
Subclass Zoanthiniaria
Order Rugosa (Horn Corals)- (M. Ordovician to U. Permian)
• Solitary or colonial corals.
• Major septa inserted in four quadrants relative to the prosepta.
• Up to three orders of septa, dissepiments in advanced forms.
• Tabulae normally present.

 Cystiphyllum
Streptelasma
Zaphrentites
Order Scleractinia (Hard Rayed Corals) -(M. Triassic to Recent)
• These corals are the dominant reef builders of the Cenozoic, although algae also play a major role.
• They are distinguised from other corals by the having their septa inserted in multiples of six, in the radial partioned endoderm  (mesenteries).

 
Order Tabulata (Tabulate Corals)- (L. Ordovician to U. Permian)
• Always colonial
• Usually small corallites
• Prominent tabulae, septa reduced or absent

Favosities
Halysites
Syringopora

B. Class Cubozoa (Box jellies)- not to be studied

C. Class Hydrozoa (Hydroids)- PreCamb. to Recent

Order Hydroida (Cambrain to Recent)
1. Obelia
Order Hydorcorallina (Tertiary to Recent)
1. Millepora
2. Stylaster

D. Class Scyphozoa (Jellyfish)- PreCamb. to Recent

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V. Echinodermata (Starfish, sea urchins, sea cucumbers, etc.)

These animals posses external skeletons of calcite plates, usually have pentameral symmetry, and are believed to be closely related (possibly ancestors) to the chordates.  This phylum includes starfish, brittle stars, sea urchins, sand dollars, crinoids, cystoids, and blastoids.

Subphylum Echinoidea

• Class Holothuroidea (Sea cucumbers) (285-286)
Fusiform or subcylindrical, mouth and anus at opposite ends of longitudinal axis. Have a very poor fossil record because have only calcareous sclerites.
• Class Edrioasteroidea (Edrioasteroids) (pp. 286-288) (Late Camb-Late Carboniferous)
The most ancient echinoidea. Five distinct ambulacral anf five interambulacral areas all confined to the upper surface and running to a central mouth. Flattened and discoidal but some globular or elongated.
• Echinoidea (Sea urchins and sand dollars)
 

Relatively rare in the fossil record since they disarticulate after death.

• Subclass Asteroidea (True starfish) (pp. 288-289) (Ordovician-Recent)
Have five arms of varialbe lenght, rduced in some to give a more pentagonal shape. Upper surface with a series of three types of plates: cardinals, dorso-laterials and marginals. Lower surface with a double row of ambulacral plates, through which the tube feet connect by pores to the ampullae.
Failure of articulate brachiopods to radiate after Permian extinctions may have been due to Asteroid predation.
• Subclass Ophiuroidea (Brittle stars) (pp. 290-291) (Ordovician to Recent)
Thin, snake-like arms used in locomotion. Ambulacra enlarged to form vertebrae and with an enclosed water vascular system. Today very abundant in bathyal and abyssal depths. Genera long ranging.

• Class Crinoidea (Crinoids) (pp. 291-293, 298-301) (Middle Cambrian-Recent)
Free-moving "feather stars" and stalked forms. Stalked forms hving a column of connected ossicles with an axial canal. Also with calyx, bracials, arms.

• Class Blastozoa (305-307) (Silurian-Permian)
Stalked, pentameral symmetry, with internal respiratory structures called hydrospires.Stem short, calyx with a crown of brachioles. Sessile filter feeders.
Maxium abundance and diversity in the Lower Carboniferous.
• Cystoidea (301-303) (Cambrian-Devonian)
Considered a group of blastoids with many kinds of pores between plate of the theca,  providing the primary classification trait.  Pores are respiratory in nature. Most attached by the thecal base or had short (few cm) stems. Brachioles rarely found. Sessile filter feeders.
• Class Eocrinoidea (Eocrinoids) (Late Camrian- Silurian)
Primitive echinoderms with pores along the sutures.

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VI. Phylum Mollusca (pp. 281-317)

Class Bivalvia (pp. 294-306) (oysters, clams, mussels, scallps, etc.)
• Possess two mirror-imaged asymmetrical calcareous valves.
• Classification is based on shell microstructure, dentition, hinge structure, surface ornamentation, and soft part anatomy.

 


Class Gastropoda (pp. 287-294) (snails and slugs)

• Gastropods are the most diverse group of mollusks.
• They inhabit marine, freshwater, and terrestrial environments.
• Unlike bivalves, they posses a true head that often has tentacles, eyes and other sensory organs.
• The majority of gastropods have coiled shells, although slugs are entirely soft-bodied.
• Gastropod orders are based on their gill morphology, heart, kidneys and reproductive system.

 
Class Cephalopoda (pp. 307-311)
• head, well developed sensory organs, including eyes and a large brain, making them the most highly evolved mollusk.
• Cephalopods may be entirely soft-bodied or possess an internal or external shell.
• Most cephalopods are excellent swimmers and predators.
• Members of this class include: squid, cuttlefish, octopus, belemnites, nautiloids, and ammonoids.

Subclass Nautiloidea (extant Nautilis)
• Possess an external shell (phragmocone) that may be straight, curved, or coiled, with simple sutures, mostly central siphuncle, and septa concave towards thr aperature.
• Four gills
• Much of knowledge of the nautiloids is based on the living genus Nautilus.  This genus has 38 tentacles, parrot-like jaws and swims by jet propulsion.  Nautilus hatchlings are 25um in length and have seven fully formed chambers.

Order Orthoceratida (Early Ordovician-Late Triassic)
These nautiloids are common in the Paleozoic and you should see some on our spring field trip. They have a straight (orthocone) to weakly curved shell (cyrtocone) shell with a subcentral siphuncle.
Orthoceras
Michelinoceras
Order Nautilida (Early Devonian-recent)
Coiled, moderately elongate shell with narrow subcentral siphuncle.
Nautilus
Subclass Ammonoidea (extinct ammonites) (Early Devonian-Late Cretaceous)
• During their reign, these were the most abundant and diverse of all cephalopods.
• Their shell may be straight or coiled with complex sutures, septa convex towards the aperture, and a ventral siphincle.
• Ornamentation of ribs, bumps, and spines are common.
• Siphuncle ventral or nearly dorsal.
  Order Goniatida (Middle Devonian-Late Permian)
Possess coiled shells with septal necks directed forward and angular sutures without intricate folding.
  Order Certitida (Late Permian-Late Triassic)
Have sutures with complexly folded lobes and smooth saddles.  They usually have well-developed ornamentation and are coiled in a single plane.
  Order Ammonitida (Early Jurassic-Late Cretaceous)
Ammonoids with thick tightly coiled shells (external) and prominent ornamentation of ribs, bumps, and/or spines.  Chambered, both the saddles and lobes of the sutures are complexly folded.   Some ammonites may have been sexually dimorphic.
Scaphites nodosus
Baculites
Ammonite
Subclass Coleoidea (squids, octopuses, and belemnites) (p. 311)
Differ from other subclasses by having a single pairs of gills within the mantle cavity.  Shell internal, straight or coiled, siphulcle may be lacking.
Belemnites (mainly Jurassic and Cretaceous)
internal shells of fossil squid-like cephalopods
Shell of three parts:
1. guard- largest and most posterior section, massive bullet-shaped cyclinder of solid calcite, conical cavity (aveolus) at anterior end. Most often the only preserved hard part.
2. phragmocone- conical, thin-walled aragonitic structure projecting outside the aveolus
3. pro-ostracum- long, flat, expanded tongue projecting forwards

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VII. Phylum Porifera (all of Chapter 4, pp. 85-100)

Note: Abundances of spicules in deep-water sections are often indicative of re-deposited sediment.

Class Calcarea (Calcareous sponges)

Class Demospongia (Most sponges)
Sponges that consist of layered calcareous masses having affinities recently attributed to the demospongea because of their  spicules.  Stromatoporoids were the dominant reef builders of the Ordovician and Devonian.

Stromatoporods (Cambrian-Oligocene, abundant in Silurian and Devonian)

•  important reef formers of the Ordovician-Devonian
• grew in lamellar sheets accreted over one another
• Ordo-Dev. forms usually domal
• may have small swellings (mamelons) and stellate grooves (astrorhizae)
Class Hexactinellida (Glass sponges)
Most are inhabitats of he deep-sea today.

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VIII. Phylum Hemichordata

• Order Graptoloidea (pp. TBA) (M. Cambrian- Devonian)
• Graptolites are thought to represent an extinct order of Hemichordates. Hemichordates are today represented by two orders, acorn worms and pterobranchs are modern representatives.
• the colony of the graptolites is known as the rhabdosome and its branches are stipes. The thecae on the stipes were occupied by zooids. Individual zooids may have been linked by a retractable stalk to a type of "pectocaulus" running throough and connecting the colony (like the modern hemichordate Rhabdopleura, p. 329).
• usually preserved as carbon films
• planktonic so good index fossil, particularly in Ordovician and Silurian
• often the only fossils in dark shales