CAPTIONS FOR FOSSIL IMAGES - version 0.2 - 17/01/94 This collection of images consists of

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CAPTIONS FOR FOSSIL IMAGES - version 0.2 - 17/01/94 This collection of images consists of various kinds of fossils, concentrating on types that are either attractive, bizarre, or evolutionarily interesting. They have been obtained from various sources (listed below). If there is interest in these, the collection will continue to grow, perhaps to include more examples of "nonexistant" :-) transitional forms, or morphologic series of fossils that demonstrate evolutionary lineages. As it currently exists, the collection is fairly small, although the images themselves are fairly bulky. It also tends to the bizarre, rather than useful. I am open to suggestions for additions, changes to format, etc. No promises, of course, but let me know what you think, especially whether the amount of space these images occupy is worth it. Notes for this version: 1. By popular demand, all files have been converted to JPEG, resulting in substantial reduction in size, with no significant reduction in quality. 2. Moire effects which plagued the early images have been greatly diminished for the newer images (YAY!). 3. All the new additions are trilobites, from Riccardo Levi-Setti's "Trilobites, 2nd edition". Make sure you check out psychopyge1.jpg and psychopyge2.jpg - they are amazing. 4. Check out olenellus_fremonti.jpg and bristolia_insolens.jpg - what would you expect as intermediate forms? Key: description first, magnification/size, [publication (see bottom)]. -Andrew macrae@pandora.geo.ucalgary.ca or: macrae@geo.ucalgary.ca ----------- skara.jpg - 8 bit greyscale, JPEG. Phosphatized 3D "arthropod" recovered from limestone by dissolution with acetic acid. Upper Cambrian, Alum Shale of southern Sweden. The genus _Skara_, and similar "arthopods" from this locality are remarkably similar to modern cephalocardians, but aren't :-) Ostracodes and agnostid trilobites are also found incredibly well-preserved here (appendages and other details preserved). 90X. [(1), p.275] tullymonstrum.jpg - 8 bit greyscale JPEG. A compression in an FeCO3 concretion from the classic Mazon Creek fauna of Illonois. This creature has a flattened tail (left), and an elongate body ending in a mouth (right). A bar-like structure with two terminating circular "blobs" extends across the middle of the body. The apparent segmentation is thought to be due to partial decay of muscle blocks. Affinities? Ha. Good luck. Possibly related to pelagic gastropods. Carboniferous age. 0.7X. [(1), p.280] edrioasteroid.jpg - 8 bit greyscale JPEG. A discoidal extinct echinoderm. Many edrioasteroids were encrusting forms. Most common in the Cambrian and Ordovician, but also found throughout most of the Paleozoic. 2-3X. [(3), p.595] eocrinoid.jpg - 8 bit greyscale JPEG. An extinct echinoderm with a body composed of many plates, and thin, ambulacra-bearing "arms" for food collection. Most common in the Early Cambrian. Genus _Gogia_. This morphology is intermediate between the "bag-like" morphology of some early free-living echinoderms (the helicoplacoids), and later crinoids. However, they probably represent an independent group that diverged from the crinoid lineage, rather than an ancestor. 1.7X. [(3), p.587] graptolite_climacto.jpg - 8 bit greyscale JPEG. _Climactograptus_. Graptolites are extinct colonial organisms with an organic wall. This specimen has been completely removed from its matrix, and is preserved in 3D. This type of graptolite was planktonic. Some others were sessile. Note the two rows of chambers (biserial). This type of graptolite is typical of the Late Ordovician and Early Silurian. SEM image. Total width at top is about 1mm. [(2), p.280] [NOTE: what would you expect as an "intermediate form" between the specimen above, and the specimen below?] graptolite_monogr.jpg - 8 bit greyscale JPEG. _Monograptus_. This graptolite has a single row of chambers (monoserial), and is typical of the Silurian and Early Devonian. It is a good example of the fact that evolution does not necessarily lead to greater complexity - this form is probably a simplification of the biserial graptolites in the Late Ordovician. This sort of simplification is a consistent trend in the graptolites. 6X. [(2), p.211] homalozoan.jpg - 8 bit greyscale JPEG. Homalozoans are extinct free-living echinoderms. They had a "tail-like" appendage for locomotion, and a series of slit-like pores. They lack the pseudo-radial symmetry of most echinoderms. Apparently homalozoans lived on the bottom by filtering detritus through the slit-like pores. Some people have suggested they could slowly push along the sediment-water interface with their appendage, and that the slit-like pores are analogous to gill slits in later deuterosomes - perhaps even indicating chordate affinities, or some sort of echinoderm-chordate intermediate. Very weird. Most common in the Cambrian. About 2cm long. [(3), p.561] homalozoan2.jpg - 1 bit B/W JPEG. Sketch of a homalozoan. Note the dispute about the interpretation of the mouth or anus. [(2), p.267] paracrinoids.jpg - 1 bit B/W JPEG. Paracrinoids are yet another sessile extinct echinoderm sort of similar to crinoids. Found only in the Ordovician. 1.6X. [(3), p.581] rudist.jpg - 8 bit greyscale JPEG. Rudists are a highly specialized type of clam that formed huge reefs in tropical areas during the Cretaceous (mostly along the Tethys Ocean). They have a conical shape, with a "lid", and a shell with internal cavities (shown in cross section). 0.3X. [(3), p.283] shark_hybodus.jpg - 8 bit greyscale JPEG. _Hybodus_ is a type of shark with large dermal spikes (the two black pointy things towards the top). This spectacular specimen shows an outline of the soft parts of the animal, including fins. Because sharks are mostly cartilagenous, they do not usually preserve this way. The specimen is even more exceptional because it shows the gut contents, which consists of hundreds of belemnite shells. Belemnites are Jurassic to Cretaceous cephalopods with an internal shell, similar to modern squid, but with a much more robust shell (rather than the thin "pen" or "cuttlebone" of modern squid). Obviously this shark was eating a great many before it died. 2m long. [(1), p.365] Lower Jurassic, Posidonia Shales, Holzmaden, Germany. trilobite_apianurus.jpg - 8 bit greyscale JPEG. A spectacular trilobite covered with spiny ornamentation. This is a reconstruction. Middle Ordovician, Virginia. Probably a few cm long. [(3), p.233] trilobite_ogygioc.jpg - 8 bit greyscale JPEG. 3 individual trilobites on a single specimen. The full generic name is _Ogygiocarella_. They appear to be shed exoskeletons (the upper one is missing its free checks, for example). Ordovician. 1.35X. [(1), p.93] trilobite_phacops.jpg - 8 bit greyscale JPEG. An enrolled trilobite with large compound eyes. _Phacops_ is common in the Devonian. 1X. [(3), p.234] olenellus_fremonti.jpg bristolia_insolens.jpg - 8 bit greyscale JPEG. Cephalon (head) of two trilobite species. Note the pair of prominant genal spines on each. The pair of crescent-shaped structures on either side of the cephalon are eyes. Lower Cambrian, Lantham Shale, Marble Mountains, S. California. 2X (approx.) Ok - questions: What if anything would you expect as an intermediate between these? [4] elrathia.jpg - 8 bit greyscale JPEG. Complete specimen of _Elrathia_kingii_, a trilobite, from the Wheeler Shale, Antelope Springs, Millard County, Utah. Middle Cambrian. 3.5X. [4, pl.101] olenoides.jpg - 8 bit greyscale JPEG. Reconstruction of a specimen of _Olenoides_serratus_ with appendages, based on specimens from the Burgess Shale, Middle Cambrian of British Columbia, Canada. Note the prominant anterior and posterior antennae. About 1X. [4, pl.14] paradoxides.jpg - 8 bit greyscale JPEG. "Monster" trilobite, more than 30cm long (!) - _Paradoxides_davidis_davidis_. Middle Cambrian, Manuals River, Newfoundland, Canada. About 0.65X. [4, pl.A2] pernopsis.jpg - 8 bit greyscale JPEG. "Tiny" agnostid trilobite with only two thoracic segments, and similarly-shaped cephalon (head) and pygidium (tail). Also from the Wheeler Shale, Middle Cambrian (see Elrathia.jpg). 6.3X (only 1-1.5cm long). [4, pl.121] psychopyge1.jpg psychopyge2.jpg - 8 bit greyscale JPEG. Spiny trilobite with large eyes. Quite bizarre looking due to a spoon-like projection from the cephalon (I.e. it is appropriately named :-)). Lower Devonian, Hamar Laghdad Formation, Alnif, Morocco. NOTE: probably the coolest-looking image in this collection. Approx. 1.4X. [4, pl.219] triarthus.jpg - 8 bit greyscale JPEG. _Triarthus_eatoni_ (Hall) from "Beecher's trilobite bed", Utica Shale, Upper Ordovician, Rome, New York, U.S.A. Preserved by pyrite in black shale, this spectacular specimen has the appendages preserved. The high iron content of the pyritization versus the shale allows the internal structures of these specimens to be studied with X-rays. Details of the appendages, digestive system, and musclature are preserved. 6.3X. [4, pl.126] [1] Briggs, D.E.G.; Crowther, P.R. (eds.), 1990. Palaeobiology: A synthesis. Blackwell Scientific Publications: Oxford, p.1-583. [2] Clarkson, E.N.K., 1986. Invertebrate palaeontology and evolution. 2nd edition. Allen and Unwin: London, p.1-382. [3] Boardman, R.S.; Cheetham, A.H.; Rowell, A.J. (eds.), 1987. Fossil Invertebrates. Blackwell Scientific Publications: Palo Alto, p.1-713. [4] Levi-Setti, R., 1993. Trilobites, 2nd edition. The University of Chicago Press: Chicago, p.1-342.

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