On Mon, 08 Nov 1999 06:09:20 +0000, mortongr@flash.net wrote:
[...]
CL>No major phyla have come into
>>existence since that strange episode. Don't tell me this is because
>>all the niches got taken up! Niches are ecological, not spatial.
GM>I won't tell you it is because of niches. But I will tell you that you are
>wrong. Here are the phyla that have appeared since the Cambrian. Some of
>them are quite major.
It is Glenn who is "wrong" here on several counts.
First, Glenn bases his argument on the fallacy that the first appearance
of a taxon *in the fossil record* was the first appearance of that taxon
*on Earth*. But as Glenn himself has previously pointed out, such is
not necessarily the case:
----------------------------------------------------------------------
Re: A. Crowl's flood questions Glenn R. Morton
(grmorton@waymark.net)
Tue, 24 Nov 1998 21:28:36 -0800
[...]
If you would look at the statistical distribution of the first and second
finds of any given fossil in the paleontological record you would realize
that there can be very significant gaps in which NO evidence for the
existence of a given species/genus/family exists. A case in point in 1980
there was no known fossil record of tarsiers. In 1986 a discovery in
Thailand proved the oldest known Tarsier was from the Miocene about
20 million years ago. Then one was found in China in 1993 and it was
from around 50 million years. The fossil record of tarsiers has gaps of
30 million and 20 million years."
[...]
http://www.calvin.edu/archive/asa/199811/0336.html
----------------------------------------------------------------------
Second, as Glenn himself admits at the foot of his message, the context
of Cliff's statement was the Cambrian Explosion, which was the first
appearance in the fossil record of the *animal* phyla, and most of Glenn's
"phyla" below are not animals. It is no defence for Glenn to say that Cliff
did not specify this in his note above. This was presumably Cliff's intent by
his words: "No major phyla have come into existence SINCE THAT STRANGE
EPISODE" (my emphasis). In fact at the end of his message Cliff actually
said "...the lack of progress since the Cambrian is so obvious".
It is simply *irrelevant* for Glenn to list *non*-animal phyla as a reply to
Cliff's statement about *animal* phyla.
Third, Glenn gets wrong some of his times of first appearance in the
fossil record.
Fourth, Glenn lists as phyla, some things which are not, strictly speaking,
phyla.
GM> Dinoflagellates Triassic
Margulis et. al. say the fossil evidence dates dinoflagellates "to at least
the earliest times of the Cambrian period, 580 million years ago":
"Phylum: Dinomastigota. Some people have estimated that there are
20,000 species of dinomastigotes. Even if you have never heard of
them, you probably know what some of them can do. Dinomastigotes
(also called dinoflagellates) are remarkably sculptured and diverse
organisms. They are known mainly because some of them form the
toxic red tides...Fossil evidence dates dinomastigotes to at least the
earliest times of the Cambrian period, 580 million years ago."
(Margulis L., Schwartz K.V. & Dolan M., "The Illustrated Five
Kingdoms", 1994, p88)
GM> Calcareous nanoplankton Triassic
AFAIK none of my books list a phylum called "Calcareous
nanoplankton". I presume they are what Margulis, et. al., call
Prymnesiophyta:
"Phylum: Prymnesiophyta...Prymnesiophytes (also called haptophytes
or haptomonads) are typical of "cosmopolitan" photoplankton. Mostly
singlecelled algae, prymnesiophytes have chrysoplasts, just as the
chrysophytes do (see page 90), but are mainly marine. Some
prymnesiophytes also form the distinctive resting stage called the
coccolithophorid, a single cell covered with little calcium carbonate
buttons or plates called coccoliths, which means "berry stones."
Fossilized coccolithophorids and forams (shelled granuloreticulosans;
see page 96) make up the famous chalk cliffs of England...For many
years scientists were not aware that the free-swimming stage of
prymnesiophytes (e.g., Prymnesium parsum, A) and the
coccolithophorid (such as Emiliania huxleyi, B.) are two different
stages of the same group of organisms. Coccoliths are distinguished by
their shapes; some examples of different types of coccoliths include
discoasters (C), rhabdoliths (D), pentaliths (E), and helicoid placoliths
(F)....Within the motile stage, organic scales form inside an organelle
called the Golgi apparatus. Calcium carbonate crystallizes on the scales
in species-specific patterns. As these microscopic coccoliths assemble,
microtubules move them out to the surface of the algal cell." (Margulis
L., et. al., 1994, p76).
Margulis has no date of first appearance of Prymnesiophytes in the
fossil record but she has a chart on page 17 which shows the Kingdom
Protoctista (of which Prymnesiophyta is a member) originating about
1.2 billion years ago. Indeed she says that "Fossils interpreted to be
robust walled cysts of protoctists are recorded in the fossil record well
over a billion years ago" and that "...the appearance of protoctists may
have occurred about two billion years ago..." (Margulis L., et. al.,
1994, pp17 & 49).
GM> Diatoms Cretaceous
Margulis, et. al., has these as "Phylum: Bacillariophyta. Known as
diatoms, these organisms are sexual protoctists. Primarily single-celled,
aquatic, photosynthetic organisms, all of them form elaborate and
beautiful tests (shells) of silica. Some form complex colonies"
(Margulis L., et. al., 1994, p100). Since they are part of the Kingdom
Protoctista, the above dates for Prymnesiophytes apply to diatoms.
GM> Bryophytes Late Paleozoic
"Bryophyta" are "low-lying, leafy, nonvascular plants" such as "the
mosses..." (Margulis L., et. al., 1994, p152).
Weier, et. al., say that "The fossil record of bryophytes is rather
meager. One liverwort fossil dates from the Devonian, but no moss
fossil dates back further than the Carboniferous..." (Weier T.E.,
Stocking C.R., Barbour M.G. & Rost T.L., "Botany: An Introduction
to Plant Biology," 1982, p553). According to Stanley S.M., "Earth and
Life Through Time", 1989, p345, the Devonian (408-360 mya) was
Middle Paleozoic (438-360 mya) not Late Paleozoic (360-245 mya), so
Glenn is slightly wrong on this time of first appearance.
Interestingly Weier, et. al., say that "the first fossils of vascular plants
appear 50 to 100 million years earlier in the record. It is more likely
that bryophytes evolved from primitive vascular plants, than the other
way around... The most common guess, however, is that bryophytes
represent an evolutionary dead end, an historic branch that did not lead
from thallophytes to higher plants, but which instead lead from vascular
plants to simpler, modified, degenerate forms." (Weier T.E., et. al.
1982, pp553- 554).
GM> Psilophytes Middle Paleozoic
Margulis, et. al., say of "Phylum: Psilophyta" that "This phylum
consists of just two living genera, one of which... [is] ...Psilotum (the
whisk fern)... Plants of this genus are unique because they lack both
leaves and roots, giving them a resemblance to the earliest vascular
plants, the rhyniophytes, although whisk ferns may have evolved from
a fernlike ancestor." (Margulis L., et. al., 1994, p154).
Weier, et. al., say that: "The first undisputed fossils of terrestrial,
vascular plants do not appear until the late Silurian period. In the
Silurian and Devonian, many types of plants began to occur in the
fossil record: representatives of the Psilophyta, Lycophyta,
Sphenophyta, and pre-ferns." (Weier T.E., et. al. 1982, p650). So I
agree with Glenn on this era of first appearance in the fossil record.
GM> Lycopods Silurian
Margulis, et. al., say of Lycopods: "Phylum: Lycopodophyta. Some
lycopods, known as club mosses or ground pines and represented by
the genus Zycopodium, can be found throughout the temperate forests
of the United States. Others, such as the quillworts (genus Isoetes), are
far less common. Both of these nonflowering vascular plants, however,
display distinctive sterile microphylls small evergreen leaves that
probably evolved as outgrowths of the main photosynthetic axis."
(Margulis L., et. al., 1994, p152). The Weier quote above re
Psilophytes' first appearance in the fossil record applies to Lycopods
also.
GM> Sphenopsids Devonian
Margulis, et. al.: "Phylum: Sphenophyta. Sphenophytes, including the
common horsetail, Equisetum arvense (A), are easily recognized by
their jointed hollow stems and rough, ribbed texture, which is due to
hardening caused by silica (SiO2) embedded in the tissue....Today only
forty species of these seedless vascular plants remain, all smaller than
their illustrious ancestors and all members of the genus Equisetum.
Some live on salt flats, others along the banks of streams, and many
others in colonies in wooded areas. The Weier quote above re
Psilophytes applies to Sphenopsids also.
GM> Ferns Devonian
"Ferns" is AFAIK not the name of a phylum! I presume Glenn is
referring to: "Phylum: Filicinophyta. Today ferns are the most
widespread and well known of the seedless, vascular plants. Ferns have
distinctive megaphylls called fronds (D)-large, photosynthetic
structures that develop spores. Although often called leaves,
propagules called fronds differ botanically from the leaves of
angiosperms...The large, conspicuous sporophyte generation grows
from a small, heart-shaped gametophyte, where motile sperm fertilize
eggs" (Margulis L., et. al., 1994, p152). I can find nothing that
unequivocally states when ferns originated, so I won't dispute Glenn on
this point.
GM> Cycadeoids Middle Paleozoic
I presume Glenn here means: "Phylum: Cycadophyta. Cycads
traditionally have been classified as gymnosperms because their seeds
are naked, not inside an ovary. Some cycads are called sago palms;
however, they resemble and are more closely related to flowering
plants...than to conifers...Cycads have compound fern- or palmlike
leaves and produce seeds. Approximately one hundred species of
cycads exist today, mostly in the tropics and subtropics... Cycads were
very abundant and diverse in the Mesozoic period, the time of the
dinosaurs." (Margulis L., et. al., 1994, p154).
Again I have no information on when the cycads first appeared, but
they became dominant in the Mesozoic: "The Permian extinctions
marked the start of the Mesozoic era. The plants that replaced the
lower vascular plants in dominance were gymnosperms: the true
conifers (Coniferophyta), Cycadophyta, and Ginkgophyta. Most of the
Mesozoic era was the age of the gymnosperms." (Weier T.E., et. al.,
1982, p656).
GM> Ginkgos Early Mesozoic
This is a phylum with only one species: "Phylum: Ginkgophyta. Since
only one species of this living fossil exists today, we are lucky that it is
a hardy ornamental often planted along streets. The only wild stands of
ginkgo trees left grow vigorously on the steep hillsides of southern
China." (Margulis L., et. al., 1994, p158). Glenn here appears to be
confusing the era of Ginkgophyta *dominance* (see Weier immediately
above) with its origin.
GM> Conifers Late Paleozoic
Here Glenn no doubt means: "Phylum: Coniferophyta. Conifers such as
Pinus rigida (D), pitch pine, are the most familiar of the gymnosperms
(plants that produce naked seeds). Conifers are grouped into fifty
genera, including Pinus (pine), Taxus (yew), Abies (fir), Picea (spruce),
and Larix (larch). The phylum also includes the largest living plant,
Sequoiadendron gigantea, the giant sequoia of California. The seeds of
conifers are naked in the sense that the embryos are not covered by the
diploid tissue of the ovary wall from the female parent. Rather,
embryos are embedded in the megasporangium, the haploid tissue of
the parent that produces megaspores. Most of these cone-bearing
plants are softwood trees with needles. Some are shrubs or low-lying
plants with needles." (Margulis L., et. al., 1994, p156). Since Weier
above says that conifers became dominant in the Mesozoic, I have no
reason to dispute Glenn's claim they first appeared in the fossil record
of the Late Paleozoic.
GM> Angiosperms Early Cretaceous
Angiosperms are the "Phylum: Angiospermophyta. With more than
400,000 species, the angiosperms, or flowering plants, are today the
most widespread, diverse, and successful plants. During the past 100
million years, angiosperms have replaced cycads...ginkgos...and
conifers...as the dominant phylum of plants on Earth...The flower and
its ovaries, which develop into fruit that enclose seeds, are the
distinctive characteristics of flowering plants. In these flowers, the
alternation of generations that is so distinctive in other plants is
reduced to microscopic size, with the male microgametophyte, or
pollen sac, consisting of just three cells and the female
megagametophyte, or embryo sac, made up of just seven cells. Fully
capable of life on land, flowering-plant pollen grains grow tubes that
convey sperm nuclei to eggs inside the ovaries deep within the flowers.
Insects...like the butterfly shown here, are crucial to the survival of
flowering plants many depend on insects, bats, or small mammals for
pollination. Other angiosperm pollen is borne by wind. Because of this
relationship, insects have co-evolved with angiosperms, have spread
with them across the planet, and enjoy an equally diverse and pervasive
presence in the animal kingdom." (Margulis L., et. al., 1994, p162).
But Glenn here confuses the time of their *dominance* as the time of
their origin. The point that Kerkut makes regarding vertebrates applies
to all fossils:
"FIG. 40. Diagram to illustrate a simple view of the level of origin of
the various vertebrate fossils. Note that the sequence runs Fish -
Amphibia Reptilia - Mammals. This account, though a simple one,
contains one serious fault. The figure shows not the time of *origin* of
the different classes of the vertebrates but instead the time of
*dominance* of that class. If we consider the time of origin we get a
more complex picture (Fig. 41). Thus instead of having the reptiles,
amphibia, bony fish and elasmobranch fishes all separated from each
other by hundreds of millions of years, they all arose during the course
of less than 100 million years." (Kerkut G.A., "Implications of
Evolution", 1973, p135. Emphasis in original)
Weier, et. al., say that Most of the Mesozoic era was the age of the
gymnosperms. However, the group that dominates the world today, the
flowering plants, must have been evolving all through the Mesozoic
era. Pieces of wood, leaf impressions, and pollen scattered through the
geologic record as far back as the Triassic period seem to be
angiosperm in nature. But the first uncontestable appearance of fossil
angiosperms is in the Cretaceous period."(Weier T.E., et. al., 1982,
p656)
In fact the first definite appearance of angiosperms in the fossil record
is
now thought to be Upper Jurassic:
-------------------------------------------------------------------------
SCIENCE
27 Nov 1998
[...]
In Search of the First Flower: A Jurassic Angiosperm, Archaefructus,
from Northeast China Ge Sun, * David L. Dilcher, * Shaoling Zheng,
Zhekun Zhou
Angiosperm fruiting axes were discovered from the Upper Jurassic of
China. Angiosperms are defined by carpels enclosing ovules, a
character demonstrated in this fossil. This feature is lacking in other
fossils reported to be earliest angiosperms. The fruits are small follicles
formed from conduplicate carpels helically arranged. Adaxial elongate
stigmatic crests are conspicuous on each carpel. The basal one-third of
the axes bore deciduous organs of uncertain affinities. No scars of
subtending floral organs are present to define the individual fertile parts
as floral units, but the leaf-like structures subtending each axis define
them as flowers. These fruiting axes have primitive characters and
characters not considered primitive.
[...]
Volume 282, Number 5394 Issue of 27 Nov 1998, pp. 1692 - 1695
(c)1998 by The American Association for the Advancement of Science.
[...]
http://www.sciencemag.org/cgi/content/abstract/282/5394/1692
-------------------------------------------------------------------------
GM> Bryozoa Ordovician
Margulis, et. al., do not have an entry for a phylum named Bryozoa.
But Wilson, et. al., say that Bryozoa's other name is Ectoprocta:
"PHYLUM BRYOZOA or ECTOPROCTA: bryozoans or moss
animals (4000 species)" ( (Wilson E.O., et. al., "Life on Earth", 1975,
p645). Margulis, et. al. do have an entry for Ectoprocta:
"Phylum: Ectoprocta. Ectoprocts have a mouth surrounded by
tentacles on a reduced head, a U-shaped gut, and ciliated larvae. In
these ways the ectoprocts, phoronids, and entoprocts depicted here
resemble one another. What distinguishes ectoprocts from phoronids
and entoprocts and defines the phylum is that their anus opens outside
the crown of tentacles. (The term ectoproct comes from the Latin for
'outside anus.") Colonial ectoprocts thickly encrust marine shells, ship
hulls, ocean rock, kelp, and other algae, such as Sargassum. Marine
fish, such as the rock fish, Sebastes serriceps (B), nibble bits of these
soft sea ectoprocts. Freshwater ectoprocts form gel balls on branches
that have fallen into lakes. The soft, living ectoproct individual secretes
a nonliving shelter either of the tough, nitrogen-containing polymer
called chitin or of a rigid calcium carbonate skeleton overlaid with
chitin, within which it is anchored" (Margulis L., et. al., 1994, p138).
The lack of Cambrian bryozoa fossils is usually put down to a failure to
find them, rather than that they weren't there. Thus Gould:
"The Cambrian then began with an assemblage of bits and pieces,
frustratingly difficult to interpret, called the "small shelly fauna." The
subsequent main pulse, starting about 530 million years ago,
constitutes the famous Cambrian explosion, during which all but one
modern phylum of animal life made a first appearance in the fossil
record. (Geologists had previously allowed up to 40 million years for
this event, but an elegant study, published in 1993, clearly restricts this
period of phyletic flowering to a mere five million years.) The Bryozoa,
a group of sessile and colonial marine organisms, do not arise until the
beginning of the subsequent, Ordovician period, but this apparent delay
may be an artifact of failure to discover Cambrian representatives.
(Gould S.J., "The Evolution of Life on the Earth", Scientific American,
Vol. 271, No. 4, October 1994, p67)
and Erwin, et. al.
"Ten or 11 phyla with skeletonized representatives first appear during
the Vendian-Cambrian radiation, and the first well documented
Bryozoa, which appear in the Early Ordovician, could very well have
been preceded by nonskeletonized members. (The earliest fossil
bryozoans are the Stenolaemata, which require a skeleton; the
Ctenostomata, however, are distinct, do not require a skeleton, but
appear in the Late Ordovician fossil record ...All phyla that appear in
the record after the Ordovician lack readily fossilizable representatives
(e.g., Sipuncula, Nematoda, Nemertea ...). Their absence from lower
Paleozoic strata requires no special explanation, and there is good
reason to believe that some, perhaps most, actually date from early
metazoan history. For example, the flatworms, which have no
confirmed fossil record, are commonly believed to have evolved prior
to the first coelomate phyla, which may date from the late Vendian..."
(Erwin D.H., Valentine J.W. & Sepkoski J.J., "A Comparative Study
of Diversification Events: The Early Paleozoic Versus the Mesozoic,"
Evolution, Vol. 41, No. 6, p1179).
There are several good reasons why Bryozoa would be difficult to find
in the fossil record:
1. They may have existed mainly in a non-skeletonised form (see
Erwin, et. al. above)
2. They are *very* small:
"BRYOZOA, a phylum of quite common, though often inconspicuous,
aquatic animals, alternatively known as moss-animals, which are
present in freshwater but are especially numerous in the sea. There are
nearly 4,000 living species of Bryozoa and perhaps four times as many
preserved as fossils. This number corresponds fairly closely to that of
the echinoderms, for example; but whereas a starfish or sea urchin can
be readily seen and admired, the beauty of bryozoans can generally be
appreciated only by the use of a microscope." (Ryland J.S., "Bryozoa",
Encyclopedia of the Animal World", Vol. 3, 1982, p275).
3. They are more sensitive to mechanical abrasion:
"Mechanical destruction may be an important abrasive factor if the
early post-mortem history of an organism takes place in high-energy
environments, i.e. areas where the action of wind, waves, and currents
are strongly felt It was found in simulated experimental conditions that
skeletons of bryozoans and calcareous algae were more sensitive to
mechanical abrasion-such as tumbling with other pointed, unpolished
pebbles-than were gastropods. Results such as this shed some light on
the possible explanation of the relative fossil abundance of some
organisms." (Pun P.P.T., "Evolution: Nature and Scripture in
Conflict?", 1982, pp80-81).
GM>You are going to now say 'Animal phlya' is what you meant. But you didn't
>specify this in your note above. Phyla have appeared since the Cambrian.
See above. This is irrelevant as Cliff was clearly talking about the
Cambrian Explosion which was only of the "Animal phyla". Glenn knows
this, otherwise what is the point of his afterthought "Phyla have appeared
since the Cambrian"?
It is interesting that plants had their own version of the `Cambrian
Explosion':
"The "sudden" evolutionary spurt 600 million years ago marked the
end of the Proterozoic era and the beginning of the long Paleozoic era,
a time when the land was low-lying, and inland seas moderated the
climate so that seasonal and latitudinal effects were minor. Apart from
periods of glaciation in the Silurian, Devonian, and Permian, it was a
time when a climate much like that in the tropics today dominated the
entire world. It was a time of enormous evolutionary change in the
plant kingdom. However, the rate of evolution did not proceed at a
constant pace during the entire Paleozoic era. Most of the new and
successful experiments in plant form appeared in only 25 to 50 million
years, during the late Silurian to mid-Devonian periods. It was then
that plants came to dominate the land; it was then that the oxygen level
of the air may have reached 10% of the present level, according to one
hypothesis." (Weier T.E., et. al. 1982, pp648-649).
GM>>And now some phyla are found before the Cambrian like Sponges and molluscs.
This may be nothing new. The Ediacaran fauna are in the Vendian
(590-580 mya) which makes them technically Pre-Cambrian, since the
Cambrian was 570-510 mya (Harland W.B., et. al., "A Geologic Time
Scale 1989", 1990, p10). Really the Cambrian Explosion should be
called the Vendian-Cambrian Explosion -see above where Erwin, et.
al., call it the "Vendian-Cambrian radiation".
Perhaps Glenn can supply more details of these "Sponges and
molluscs" and when exactly they appeared in the fossil record?
Steve
--------------------------------------------------------------------
"One of the most surprising negative results of palaeontological research in
the last century is that such transitional forms seem to be inordinately
scarce. In Darwin's time this could perhaps be ascribed with some
justification to the incompleteness of the palaeontological record and to
lack of knowledge, but with the enormous number of fossil species which
have been discovered since then, other causes must be found for the almost
complete absence of transitional forms." (Brouwer A., "General
Palaeontology", [1959], Transl. Kaye R.H., Oliver & Boyd: Edinburgh &
London, 1967, pp162-163)
Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones
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