December 22nd on the Cosmic Calendar: The first amphibians and the first flyin’ bugs! I feel safe using the term “bugs” because I don’t think there has ever been a flying arachnid (shudder).
It is thought the first of our amphibian ancestors evolved from lobe-finned fish like coelacanths and lungfish in the carboniferous period. Lobe-finned fish have thick, meaty ventral fins with muscle and bone structure. These fins literally do double as legs for walking on the sea floor, which is an interesting adaptation in itself. You may have heard of coelacanths — the “living fossils”. Coelacanths were already well known to paleontologists from the fossil record, when to everyone’s shock and disbelief a fisherman in South Africa pulled one up in his nets in the 1930s. They’re not extinct at all.
Lungfish are also lobe-finned, and as the name implies, developed primitive lungs. It seems that like algae they found themselves living in shallow ponds that tended to evaporate. They evolved lungs to breath air when necessary, and over time their lungs improved and their lobe-fins also evolved into land legs. Enter the earliest known amphibian, Ichthyostega!
Bugs took wing which eventually led in the carboniferous to this monster dragonfly, meganeura. Meganeura had a 2 foot (65 cm) wingspan. Yeah. Forget that can of Raid — try a shotgun.
You may remember Cosmos, the 1980 PBS series by Carl Sagan. Maybe you also recall Sagan’s “Cosmic Calendar” from the series, where in order to put the immensely vast history of the universe into a comprehensible scale, he mapped it onto a calendar year. In other words, if the entire history of the universe were one year, with the big bang in the first second of midnight on January first, and the present day on the last second of December 31st, New Year’s Eve. A project of mine this year has been to note the major events in the Cosmic Calendar, on the real calendar, on this blog!