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
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)].
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.
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.
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]
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.
Ok - questions: What if anything would you expect as an intermediate between
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]
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]
 Briggs, D.E.G.; Crowther, P.R. (eds.), 1990. Palaeobiology: A synthesis.
Blackwell Scientific Publications: Oxford, p.1-583.
 Clarkson, E.N.K., 1986. Invertebrate palaeontology and evolution. 2nd
edition. Allen and Unwin: London, p.1-382.
 Boardman, R.S.; Cheetham, A.H.; Rowell, A.J. (eds.), 1987. Fossil
Invertebrates. Blackwell Scientific Publications: Palo Alto, p.1-713.
 Levi-Setti, R., 1993. Trilobites, 2nd edition. The University of
Chicago Press: Chicago, p.1-342.