At 10:09 AM 2/2/98 -0800, Arthur V. Chadwick wrote:
>At 09:47 PM 1/30/98 -0600, Glenn wrote:
>>I can understand why organic deposits like dung would be oxidized into
>>oblivion in an extremely arid desert. I have difficulty with the idea that
>>all organics would be destroyed in a subaqueous environment
>Maybe you can also explain why these animals were living on a barren
>desert. What did they eat?
>>At least with the Mongolian deposits I can cite the rhizoliths as evidence
of former vegetation. I will admit to more trouble with the Coconino and
Navajo in regards to food. I have lots and lots of articles on order for the
Navajo and Coconino (first shipment due tomorrow) and we will see.<<
Well, the first shipment didn't arrive until today. But I have an answer to
Art's question about what the animals in the Navajo ate. They ate plants
that grew in interdune areas.
Winkler et al write:
"Trackways in the Navajo Sandstone and others from desert environments
are concentrated in localized ephemeral wetted areas (fluvial intertongues
and interdunes..). All fossils reported here are confined to interdunes, and
most to wet interdunes. ONly root casts and burrows are locally abundant in
some dry interdune deposits or on deflationary interdune surfaces
(first-order bounding surface). Of the seven localities in the Navajo
Sandstone now known to have produced body fossils of terrestrial
vertebrates, three are associated directly with interdune deposits. We have
not examined the other four localities reported in the literature. However,
the discussion and illustration of the occurrence of the theropod dinosaur
Segisaurus show its clear proximity to interdune deposits.
"Wet-interdune deposits near Eggshell arch are surrounded by dunes and
deflation surfaces, and are not derived from fluvial systesm that invaded
the erg. A relatively diverse biota, especially one that includes large
vertebrates, in deposits from wet interdunes implies either that these
plants and animals were able to utilize locally mesic environments within
active ergs, or that these interdune areas formed during periods of wetter
climate and relative dune stabilization during erg development."~Dale A.
Winkler,et al, "LIfe in a Sand Sea: Biota from Jurassice Interdunes" Geology
19:889-892, p. 891
It seems that the animals ate plants in the interdune wetlands and drank
that water also.
Adam, Apes, and Anthropology: Finding the Soul of Fossil Man
Foundation, Fall and Flood