Re: disappointment

["David Marjanovic" <david.marjanovic@gmx.at>]

Freunde der Bayerischen Staatssammlung für Paläontologie und historische
Geologie München e. V. (ed.): Urvogel *Archaeopteryx*. Abstammung -
Entwicklung - Lebensraum [descent - development/evolution - habitat], 27 --
29 October 1995

Consists of an article about Archie by Peter Wellnhofer and one about its
habitat:
Walter Jung: Araukarienwälder oder Brachyphyllum-Dickichte die Heimat des
Archaeopteryx? [Araucaria forests or *B.* thickets the home of *A.*?], p.
136 -- 151

This describes what is known about the flora of Solnhofen and its
surroundings. There is no monograph, and many species and genus names are
rather useless. Many large groups of plants are absent:
- Mosses. No surprise as hardly any fossil mosses are known
- Lycopods. Need lots of fresh water which wasn't there.
- Angiosperms. You would never have guessed that...
- Horsetails. While there are a few from French and Spanish formations of
similar age, there are none in Germany. "Because the preferred habitat of
fossil sphenopsids are the margins of perennial inland bodies of water or at
least wet places, the lack of such biotops could offer a possibility of
explanation."
- Other ferns. Have been described, but apparently all are seed ferns and
suchlike."[...] not a single fossil from the plate limestones of our area
can be referred to [...] pteridophytes [...]. All plant remains [...] except
the [...] 'phyllothalli' and other alga-suspect specimina incertae sedis,
are derived from [...] gymnosperms."

*Cycadopteris jurensis* is a seed fern, possibly belonging to the Gondwanan
family Corystospermaceae.
Bennettitaleans = cycadeoids are present in the form of *Zamites* fronds and
*Bucklandia* twigs. The latter are thin and bear a spiral arrangement of
stigmata (leaf scars), indicating that they were low trees or bushes. The
density of the stigmata is periodical, indicating growth rhythms and
therefore seasons. Cycads could be present, but the only means of
discriminating them from bennettitaleans is an analysis of stomata anatomy
which is impossible in this material. *Sewardia* = "*Furcifolium*" is
possibly a cycad and not, as originally thought, a ginkgo relative.

The only specimen of a ginkgo is a single 4 cm long leaf called *Chondrites
flabellatus*, which could easily be an alga (it is impossible to tell from
the fossil). "[...] the group of ginkgophytes at none of the plate limestone
sites, not even at the fossil-rich French ones, makes up more than 1%. Often
remains of this sort are completely absent. The proportion of ginkgophytes
in the Upper Jurassic flora seems to have usually been overestimated."
Means, don't draw Archie perched in a ginkgo.

Conifers are plentiful. There are Araucariaceae, which are almost only
represented by the scales that bear the seeds, loosen from the cones and fly
away, whatever they're called. Twigs with scaly needles are known, however.
More frequent are twigs called *Brachyphyllum* and *Palaeocyparis*. These
are form genera and rather useless. However, at least the former is a member
of the Hirmeriellaceae = Cheirolepidiaceae (see below). About a dozen cones
are known from both. "Another suspicion that the author already expressed
two decades ago is supported by new findings: This family [not
Araucariaceae, as I have repeatedly written onlist] contained not only tree
forms but also small, densely branched, thus bush-shaped forms with
succulent [...] branches. Whether this succulence is to be regarded as an
adaptation to brackish places or a hot-dry environment may remain open."
Several other form genera for twigs and single needles have been named.

"There is unambiguous evidence for dry conditions. First there is the
succulence of the twigs, the concealment of the stomata [...], the sometimes
extremely thick cuticula and the [...] lack of pteridophytes. If it were
that way, the low growth of the brachyphylls and palaeocyparids could also
hint at lack of water at least at certain times. The [...] changing zones on
the *Bucklandia* twigs require a growth periodicity. Regarding the warm
climate -- generally sea water temperature is assumed to have been 26 °C -
one will have to think of a change of rainy and dry seasons, thus a
typically subtropical climate. [Indeed Solnhofen was at about the latitude
of today's Canary Islands.] Larger tree forms were probably the araucarias.
However, the rareness of their needle twigs, opposed to the nearly exclusive
occurrence of winged dispersal units shows they must have grown far away of
the plate limestone lagoons." Large stem remains are not known at all.
"[...] we may imagine thickets of Hirmeriellaceae and seed ferns at the
coast, possibly with single bennettitaleans and cycads, and farther from the
coast araucarias with some bennettitaleans, cycads and maybe even ginkgo
trees. Which of these plant associations was the home of *Archaeopteryx*?"
No answer. But the last page shows "A group of Chile araucarias at their
natural occurrence in the South American Andes. The Jurassic araucarias may
have formed similar associations on the heights of the Bohemian Massif",
which was 200 km away. Wellnhofer actually thinks (in the article before
this one) that Archie, an insectivorous ground runner capable of perching,
lived there and was only blown into the lagoon by "exceptionally strong
century storms"...

It seems that the brachyphyll vegetation was common in the Altmühlalb area
(AFAIK in the south), whereas *Cycadopteris* and *Arthrotaxites*, two other
conifer twig form genera, occur farther to the east, and that
*Brachyphyllum* and *Palaeocyparis* characterise the younger deposits,
*Cycadopteris* and *Zamites* the older ones.

Lots of fossils reside in private collections and have yet to be made
available to science. :-(

Hope this helps!