Trilobite fossils In article C93ytt.7uH@mailer.cc.fsu.edu, dlecoint@garnet.acns.fsu.edu (D

---
Master Index Current Directory Index Go to SkepticTank Go to Human Rights activist Keith Henson Go to Scientology cult

Skeptic Tank!

Trilobite fossils Organization: Iowa State University From: danwell@IASTATE.EDU (Daniel A Ashlock) Message-ID: <1993Jun24.085314@iastate.edu> Reply-To: danwell@IASTATE.EDU (Daniel A Ashlock) Newsgroups: talk.origins In article , dlecoint@garnet.acns.fsu.edu (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[1], 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? Dan Danwell@IASTATE.EDU [1] 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 Organization: HASA From: jjh00@diag.amdahl.com (Joel Hanes) Message-ID: <32H.02Up47Hn01@juts.ccc.amdahl.com> Reply-To: jjh00@diag.amdahl.com Newsgroups: talk.origins danwell@IASTATE.EDU (Daniel A Ashlock) writes: > >[1] 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 limbs * 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. --- Joel Hanes ============================================================ Organization: Geology & Geophysics, Adelaide Uni From: cnedin@geology.adelaide.edu.au (Chris Nedin) Message-ID: Followup-To: talk.origins Newsgroups: talk.origins 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 /\/ | |/ | surface ___________|__________________________|_____________ 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: farrar@pops.navo.navy.mil (Paul D. Farrar) Message-ID: <1993Jun25.155416.23508@cs.tulane.edu> Reply-To: farrar@pops.navo.navy.mil Newsgroups: talk.origins 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. PDF 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