Trilobite fossils In article C93ytt.7uH@mailer.cc.fsu.edu, email@example.com (D
Organization: Iowa State University
From: danwell@IASTATE.EDU (Daniel A Ashlock)
Reply-To: danwell@IASTATE.EDU (Daniel A Ashlock)
In article ,
firstname.lastname@example.org (Darius A. Lecointe) writes:
> Why don't you give me a good layman's view of trilobite fossils
> and I can then give you my opinion of them. Just a synopsis.
> If I can't handle it I'll let you know.
Trilobites look like enlongated crabs wearing motocycle helmets,
or, sort of like horseshoe crabs. There are big ones and little
ones in the fossil record spread out through a large number of
strata. From their appearance (counting legs, noting if the legs
are used for breathing or walking, and other details) we deduce
the trilobies are arthrapods but in a different group from the
crustaceans or insects.
They died out a very long time ago but used to be real major players.
Thier fossils appear all over the place and can often be purchaced in
meusem gift shops. There are scads of clearly different types of
trilobites and the types change with time.
What else did you want to know? Was that lay enough?
 Correct me if I'm wrong but the number of legs and their
specialization for breathing or walking/swimming is a major
classification tool in arthrapods, right?
From: Joel Hanes
To: All Msg #45, Jun-24-93 08:34AM
Subject: Re: Trilobite fossils
From: email@example.com (Joel Hanes)
danwell@IASTATE.EDU (Daniel A Ashlock) writes:
> Correct me if I'm wrong but the number of
>legs and their specialization for breathing or
>walking/swimming is a major classification tool
>in arthropods, right?
From reading Gould's _Wonderful_Life_, I remember the following:
* arthropods are segmented.
* in general, each segment bears a pair of bilaterally-symmetric
* in a generalized primitive arthropod, each limb has
two branches, or _ramia_; upper and lower.
* the presence and specialization of the ramia
are important in classification -- e.g. the Uniramia
retain only the lower "leg" branch.
Organization: Geology & Geophysics, Adelaide Uni
From: firstname.lastname@example.org (Chris Nedin)
Actually all the trilobite legs were use for walking *and* breathing.
They posessed Biramous limbs which had the gill above the walking limb
but attached to it
shell =========> ___________________/ | half body shown
/ ___ |
/ \\\\\\\\\\\\\\ | > |
gill ============> ----------------| > |gnathobases
////////////// /___/ |
/ / |
segmented =====> / |__|___|___|___|__| |
leg /\/ |
The segment with to which the gill attached, the Coxa, also had on its
inner surface a set of gnathobases which were used to grind up food before
passing anteriorly to the mouth.
From: email@example.com (Paul D. Farrar)
Trilobites aren't the only arthropods to breathe with their legs.
As a boiled crab lover (clarification: I love to eat boiled crabs, NOT
I am a cancerophile who has been boiled) I have noted that they also
possess gills on the upper "leg" of their biramous assembly. These gills
are tucked up inside their lower shell.
Arthropods have made a lot of things out of "legs," including their
"jaws" (our jaws are gill arches) and antennae.
This post does not reflect they official views of the US goverment, or
any of its agencies, heirs, or assigns, on the interpretation of
invertebrate or vertebrate anatomy or physiology, or anything else.
E-Mail Fredric L. Rice / The Skeptic Tank