Monday, December 29, 2008

Correction: Lepidodendron sp. actually Sigillaria sp.

The post below was the result of a quiz of a fossil I put on GYBO quite a while back. Prem Subrahmanyam was kind enough to not only correct the identification but to also provide the reason (a very interesting one at that). I refer you to his comment below.
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Keith nailed this one. It is Lepidodendron. A genus of vascular "trees" from the Carboniferous period (~300MYBP) that are closely related to quilworts (Isoetes) and club mosses (Lycopodium). This partiular specimen was found by a botanist friend in Arkansas. During the Carboniferous period, modern land masses were located along Earth's equator and the world was warmer and more humid. Plants like Lepidodendron lived in the lush swamps that formed the massive coal, oil and natural gas reserves that presently fuel our modern world. As we all know, by re-releasing the carbon of the Carboniferous we are warming the earth and thus altering the patterns of biotic distribution.

6 comments:

Keith said...

Serendipity strikes again! In looking around at plant fossils online, I was astonished to discover that Mazon Creek in Kankakee, Grungy (Grundy), and Livingston Counties in Illinois is well known for beautiful fern fossils. Amazing! See link below. I botanized Mazon Creek near Morris once, but couldn't enjoy it as my left cornea had been punctured by a long thorn on Elaeagnus angustifolia at the previous stop. The drive home with double-vision was no small challenge.

Paste link into URL bar and scroll down the page a bit:
http://www.nmnh.si.edu/rtp/students/2007/schedule07_paleobiology_tour_photo_botany.html

Keith said...
This comment has been removed by the author.
Keith said...

Crap. For whatever reason, when I paste the link and then publish the comment, part of the link is missing - every time. Just Google it!

Prem Subrahmanyam said...
This comment has been removed by the author.
Prem Subrahmanyam said...
This comment has been removed by the author.
Prem Subrahmanyam said...

I will have to respectfully disagree. This is actually Stigmaria and not Lepidodendron. Stigmaria is the genus applied to the fossilized rhizomes of these ancient club moss 'trees', and Lepidodendron is the genus applied to the fossilized trunk of these plants...in paleobotany, you can often end up with one actual plant spanning several 'genera' as the likelihood of finding all pieces of the plants articulated was very small, and if paleontologists waited until everything was found together to describe their finds, science would not progress at all.

The way you can distinguish Stigmaria from Lepidodendron is that Stigmaria has a number of small pits as is shown in this photo with a relatively smooth surface between the pits. The pits are formed by the rootlets that extended out from the plant's rhizome. Lepidodendron presents more of a 'fish-scale' appearance from the bases of the 'leaf' scars, such as can be seen in this photo:

click here to see a Lepidodendron photo

So, while Keith was close, he was not quite correct.