RE: Fossil Insects

Karen G. Jensen (
Tue, 16 Mar 1999 19:14:40 -0600

Dear Mr. Frack,

Thank you for the information you sent on Mesozoic insects.

>Apparently, you know something about fossil insects I don't. Moreover, you
>seem to be more up-to-date than the references in my library on fossil

Well, it looks like you know quite a lot. The data from the Treatise
provides a baseline. Here it is, summarized in a table:

Mesozoic Fossil Record of Four Insect Orders:
number of fossil families and their stratigraphic distributions
(each order considered in two groups, "primitive" and "advanced")

38 families found as Mesozoic fossils, 28 of them extant (10 extinct):
Tr Jur K T R
13 (4) (4)
1 (0)
4 (4 )
13 (13 )
7 (7)
31 families post-Cretaceous only.

59 families found as Mesozoic fossils, 17 of them extant (42 extinct):
Tr Jur K T R
35 (1)
6 (6)
12 (3)
6 (6)
56 families post-Cretaceous only.

49 families found as Mesozoic fossils; 33 of them extant (16 extinct):
Tr Jur K T R
1 (1)
13 (4)
9 (2)
26 (26)
23 families post-Cretaceous only.

1 family found as a Mesozoic fossil, not extant.
Tr Jur K T R
20 (all other) families post-Cretaceous only.

As you may know, I am comparing interpretations of the fossil insect data
from two different viewpoints, a Creation/Flood model as well as an
Evolution/Long Ages model. Differing expectations of the two models

Expected Characteristics of the Insect Fossil Record

Creation/Flood Model Evolution/Long Ages Model

all kinds* contemporaneous all from one common ancestor
flood burial with assoc. veg. co-evolution with assoc. veg.
flood extinction of many various extinctions
survival of many via eggs some groups long-lasting
much postflood speciation much speciation

*probably suborders or superfamilies

In the Flood model under consideration, the sequence of events during the
worldwide water catastrophe (Genesis 7-8) produced an orderly progression
of layers -- briefly the lower (Paleozoic) being mostly marine, the middle
(Mesozoic) including much land-derived material eroded by rising waters,
and the upper (Cenozoic) mostly resulting from decreasing sea levels and
subsequent tectonic adjustments.

Insects in this scenario would be expected to take cover in their
respective vegetation types until this vegetation was inundated by rising
sea levels. At that time they would be expected to be caught in the
sediments, float, and/or be destroyed. The more water-resistant forms
would be expected to be fossilized more often than the easily dismembered
forms. Most populations would survive only as eggs attached to floating

This model predicts insects with the coal forest vegetation (Paleozoic),
some at the onset of erosion of the truely soil-rooted land forest
vegetation (Mesozoic - Triassic & Jurassic) and others as the last upland
vegetation was inundated (Cretaceous), but attenuation of each fauna after
its initial abundance, due to disintegration of the fragile bodies.

The above data show some interesting patterns, consistent with the
hypothesis of Mesozoic sediments as recording the erosion of true
soil-rooted trees with their associated insect faunas.

Coleoptera, which are relatively water-resistant (and include many aquatic
species), are well represented (38 families), including many survivors (28
of the 38 are extant).

Diptera, which are not as water-resistant (many being incapacitated by
raindrops), are well represented in Tr-J seds (47 families), but fewer (12
families) in K seds. Some of these families are extant (16 of 59), but
many more extinct (43 of 59 or 72%).

Hymenoptera, which are somewhat water-resistant, able to survive some wetting,
have one subgroup (the primitive) well represented in Tr-J sediments (14
families) with none in K, and the other (advanced) forms which are better
represented in K than in Tr-J (26 cf 9 families). The former group is
largely extinct (only 5 of 14 families extant) while the latter group is
mostly extant (28 of 35 families, including all 26 of the K families).

Lepidoptera, which are not water-resistant, being easily incapacitated by
wetting, is very poorly represented (1 family); all other families are
post-Cretaceous only.

All these orders include many families (31 Coleopteran, 56 Dipteran,23
Hymenopteran, 20 Lepidopteran) have no pre-Tertiary record, as would be
expected for such fragile animals.

I wonder if the paucity of Cretaceous Coleopterans will be filled in with
further discoveries. I would like to know more detail, especially of the
abundances and stratigraphic distributions of the 26 Cretaceous
Hymenopteran families.

>Unless you have information more recent or contradictory to these
>references, you appear to be mistaken. If you do have such information, I
>would appreciate it if you could cite it so I can add it to my library.
>You further state that these insects are "not anything like what would be
>expected if the flowering plants were co-evolving with insects" I have no
>idea what this is supposed to mean. The numbers of insects in the fossil
>record is affected by their diversity, abundance, and the chances that they
>will be fossilized. How many should we "expect"? Most of the co-evolution
>discussed is a Cenozoic phenomenon, not Mesozoic. Why would you expect
>great numbers of insects within the context of co-evolution if the plants
>weren't diverse enough to encourage the insects?

Cretaceous flowering plants are quite diverse. Paleobotanists recognizing
the importance of insects to the clearly insect-pollinated Cretaceous
plants have expressed disappointment in the Cretaceous insect record, e.g.
pp. 52-57 of Paleobiology of Angiosperm Origins by Norman F. Hughes,
Cambridge University Press 1976 (see especially Figure 6.2, p. 54), and pp.
50-51 (and 249, etc.) in The Enigma of Angiosperm Origins by the same
author and publisher, 1994.

The Cretaceous is the
>first time that angiosperms appear at all commonly. Their adaptive
>radiation in the early Cenozoic is matched by an increase in those insect
>groups most commonly associated with pollination, Lepidoptera and
>Hymenoptera: Apocrita. If there is not a cause-effect relationship here, do
>you have a better explanation for the coincidence?
Coordinated adaptive radiation of insects and flowering plants has clearly
occurred. Some diversity increases may have other explanations, however,
such as contributions from additional source areas. Diversity increase
does not always mean diversification.

>> This has been noted as a "problem" among angiosperm paleobotanists. I
>> remember talking to the entomologist that worked with N.F.Hughes at
>> Cambridge, who was eager to find any Cretaceous insects. That was 1980.
>> Some have been found, showing that the depositional environments were
>> capable of preserving insects. The paucity is a puzzle for those who
>> expect to trace the origins of entomopyllous (insect pollinated) plants in
>> the fossil record.
>I'm still with Steve in wondering what you mean to imply by "problem" and


In the trivial sense, every researcher deals with "problems" and


You clearly seem to imply that these have some important

Yes. At the very point where a complete fossil record of insect-plant
interaction would be welcomed by those studying angiosperm origins, there
are relatively few insect fossils. This is predicted in the flood model,
since insects could not be expected to do well after their associated
vegetation was eroded and afloat.

To me the vast difference between Cretaceous and Paleogene insect fossil
abundances is an indicator of a profound change in ecological conditions
and depositional environments.

I doubt that all of the fossils I referred to above have been
>found since 1980,

Yet there have been some significant discoveries -- including finds from
the lower Jurassic of Dorset (Whalley, 1985), the Kimmeridgian of Russia
(supplementing the Solenhofen of Germany), the Lower Cretaceous of
Transbaikalia (Krassilov and Rasnitsyn, 1982), and more from the English
Wealden (Jarzembowski, 1984 and 1991), and the Aptian of Australia (Jell &
Duncan 1986), and others. These have changed the picture considerably.
And more can be expected.

so either the person you refer to above wants specimens,
>wants a better fossil record than we have, or doesn't know the literature.
>What point are you trying to make here?
The man was Dr. J. Smart, I believe, who wrote for the Royal Entomological
Society. He was about to retire in 1980. He was eager to see the insects
we were finding from the Green River Formation (Eocene), to help bridge the
relatively sparse record between the Jurassic and the Paleogene.

What I see as significant is that the data which is seen as consistent with
an evolution/long ages model of earth history is also consistent with a
Creation/Flood model of earth history. I don't expect you to agree :-).

Thank you again for the Treatise data you sent.