Nilsson, Dan-E., and Pelger, Susanne (1994).  A pessimistic estimate of the
time required for an eye to evolve.  Proc. R. Soc. Lond. B, 256, p.53-58.
The "partially developed" eyes as shown in the paper can see just fine, but
the spatial resolution is not as high as later developments.  Every step
starting from a blob of light detecting cells can be improved upon, but each

This document contains miscellaneous information relevant to discussions in
talk.origins.

Where can I find an example of "transitional fossil species"?
Bristolia insolens
Bristolia bristolensis
Olenellus mohavensis
Olenellus fremonti

From the Lower Cambrian Lantham Shale of the Marble Mountains, southern
California, U.S.A. Illustrations are from: Levi-Setti, R., 1993.
Trilobites, 2nd. Edition. University of Chicago Press:Chicago, 342pp.

The fossils are arranged in standard stratigraphic order - oldest at the
bottom, youngest at top. These specimens are only the cephalon - the "head"
of a trilobite. Other changes are observed in the shape of the thoracic
segments of these species.

Eocoelia (a Silurian brachiopod)
Eocoelia is a small (about 1cm long) brachiopod ("lamp shell") from lower
Silurian-age (Upper Llandovery and lower Wenlock) rocks. It is found
world-wide, including Britain, Nova Scotia, Pennsylvania, Iowa, Siberia,
Norway, and South America. In several of these locations, a succession of 4
species has been recognized (see above), which is found consistently over
wide areas (all of North America and Europe at least). Besides the species
succession, statistical variations in the properties of the species can be
observed. These are best documented in the illustration presented above,
modified from:

Zeigler, A.M., 1966. The Silurian Brachiopod Eocoelia hemisphaerica (J. de
C. Sowerby) and related species. Palaeontology, v.9, part 4, p.523-543.

In this case, the variation in "rib strength" - the distinctiveness of the
ribs - is depicted. Similar "progressive" variations occur in other
characteristics within this lineage.

Other brachiopod lineages within the same interval of the Silurian also
show consistent morphological change with time, although this may be due to
paleoenvironmental changes in some cases. See:

Johnson, M.E., 1979. Evolutionary brachiopod lineages from the Llandovery
series of eastern Iowa. Palaeontology, v.22, part 3, p.549-567.

Baarli, B.G., 1986. A biometric re-evaluation of the Silurian brachiopod
lineage Stricklandia lens/S. laevis. Palaeontology, v.29, part 1,
p.187-205.

Other references pertinent to "transitional" fossils:

Johnson, J.G., 1982. Occurrence of phyletic gradualism and punctuated
equilibria through geologic time. Journal of Paleontology, v.56, no.6,
p.1329-1331.
MacLeod, N., 1991. Punctuated anagenesis and the importance of stratigraphy
to paleobiology. Paleobiology, v.17, no.2, p.167-188.
Lineages within the irregular echinoids, described in chapter 5 ("Fossil
Lineages") of:
Smith, A., 1984. Echinoid Palaeobiology. Allen and Unwin: London, p.1-190.
ISBN 0-04-563001-1
But the rocks are dated by fossils, and the sequence of fossils is dated by
evolution. Isn't this circular?

NO. The sequence of fossils is an empirical observation with no assumptions
based on evolutionary theory. The fossils are simply observed in a vertical
sequence of rock, which, by the principle of superposition, is oldest at
the bottom of the stratigraphy, and youngest upwards (when restored to its
original orientation by independent means -- e.g., wave ripples which
indicate "stratigraphic up"). That the sequence of fossils is not dependent
upon evolutionary theory is demonstrated by William Smith, an engineer who
used sequences of fossils to construct detailed geological maps in southern
England in 1815 and earlier -- decades before Darwin's evolutionary theory
existed.

Here is a copy of Smith's map:
Most of the commonly-known periods of time in the geologic time scale were
described in the 1700s and early 1800s, also before Darwins theory was
published. For example, the Cretaceous was proposed in 1822 by J.J.
d'Omalius d'Halloy for the (mainly) chalk units in the area of northern
France.

See: Harland, W.B.; Cox, A.V.; et al., 1982. A Geologic Time Scale.
Cambridge University Press: Cambridge, p.1-131, ISBN 0-521-28919-X.
Chapter 2 provides documentation of the origin of all the major time
intervals. A very large proportion pre-date by decades the 1859 publication
of Darwin's "Origin of Species".
Are there any Precambrian metazoan animal fossils?
Metazoans are commonly found in an interval known as the Ediacaran, named
for the location in Australia where fossils of this age were first found.
Examples of Cnidaria ("jellyfish", "sea anemones", and "sea pens") are
common, as well as other groups of uncertain affinities (possible annelid
worms, lophophorates, etc.). The Ediacaran fauna is found world-wide in
rocks of late Precambrian age, and is entirely soft-bodied.
Charnia masoni - a pennatulacean or "sea pen"
Dickinsonia costata - thought by some to be an annelid worm.
Specimens are from the Khatyspyt (northern Yakutia) and Ust-Pinega (White
Sea region) formations in the former U.S.S.R.
Illustrations are from: Fedonkin, M.A., 1990. 1.3. Precambrian metazoans.
IN: Briggs, D.E.G. and Crowther, P.R. (eds.) Palaeobiology: A Synthesis.
Blackwell Scientific Publications:Oxford, p.17-24. It contains citations of
several other references on the subject of Precambrian animals.
What is the theoretical maximum mass for a land animal?
See: Hokkanen, J.E.I., 1986. The size of the largest land animal. Journal
of Theoretical Biology, v.118, p.491-499.
Abstract:
The upper mass limit to terrestrial animals is studied using physical
arguments and allometric laws for bone and muscle strength and animal
locomotion. The limit is suggested to lie between 10^5 and 10^6 kg. A
possibility for a still higher mass, in case of new adaptations, is not
excluded.
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