so when i see museum paleobotany illustration like especially pre-cenozoic most of the plants look intuitively 'simpler' to me; more cartoonish than modern plants, even modulo the overall realism of the illustration. i vaguely assumed this was because they were based on degraded fossil evidence, but lately i was thinking it's not inconceivable that morphology actually tended simpler in the past. any insight?
(buckle in lads im going to go hog wild here)
for instance, going way back (before the earthâs whole Lepidodendron coal swamp phase, so like, ancient relatives of nonvascular plants like liverworts and mosses were around, but that was it), plants were really starting to invest hard into the whole âwhat if our bodies were tubes?â innovation brought forward by ancient hornwort relatives (thatâs an entirely different tangent). so the very first vascular plants ever, as they emerged in the very early Devonian, probably looked something like this (sculpture reconstruction is of Aglaophyton major):
no leaves yet. also note that each branch is split into perfect pairs (dichotomous branching), and each pair of branches has a single reproductive organ at the end. these are both classic hilarious beta test plant kingdom problems as i talked about in this post and i WILL cyberbully these extinct squiggles for it
at this point thereâs like, still a good few iterations of Noodle Time that will happen in the next few million years before the whole âwhat if leaf?â idea really becomes a thing. along with Aglaophyton we have Horneophytopsida (arguably the most primitive), and a couple others. after that, things really start to heat up with the famous Cooksonia, in whose fossils we see the first transitions from Noodle Moss Time to the first real vascular plants (tracheophytes) on earth: extremely primitive Noodle Vascular System Time. as you can see, this is all really variations on a theme
still very cartoonish-looking. still no real leaves. the first leaves, in fact, will be two different kinds of leaves: for the Isoetes party of plants, consisting of modern-day quillworts, spike mosses, and club mosses, and their ancient relatives of Lepidodendrons and the like, the first leaves will be called âmicrophyllsâ, and will be basically a little point coming off the main vascular system with a single vein running through it. this is what Lepidodenrons had instead of âproperâ modern leaves and is why they look weirdly furry. real modern leaves never really caught on with this group of dudes.
one of the things Lepidodendron is REALLY well known for is for the scale texture left on their upper trunks. these are called leaf cushions, can be used to identify the species found in a fossil (the size, shapes, and details are very minutely different from species to species), and are left over from when the plant had microphylls attached to itâs trunk. as the plant matured, it would shed these leaves and leave behind the scaley bases, and as it grew even taller the scales themselves would shed and leave the plant looking smooth. in maturity, itâs suspected that only the top of the plant had microphylls, but older illustrations will depict the scales going all the way to the base.Â
(side note: some modern lycopods still have these. see lycopodium, aka the modern club moss genus. the club moss ones are irresistible not to pet and feel really stiff when you touch them and inevitably lightly grasp a stalk and run your entire fist down the length of it because of a primal urge to Touch The Weird Plant)
now, meanwhile while all this is happening Isoetes crowd, other plants are realizing that maybe thereâs a more efficient way to Be A Tube on planet earth. the ancient relatives of whisk ferns, horsetails, and ferns â a group whoâs diverged descendents will eventually go on to evolve seeds and then, 300 million years down the line, flowers â will evolve the first modern leaves as we know them by making âmegaphyllsâ, which unlike microphylls have a leaf blade stretched between multiple veins as opposed to just a weird hair/point with a single vein. behold:
oh yeah baby. Noodle Time just got organized. it turns out that if you stretch some leaf between those hilariously poorly thought out branches and figure out how to not kill yourself doing it, youve really got something going on, and plants have been riding that ever since.
so in conclusion: yes, they really did look like that. at least to the extent of our current knowledge. 400 million years ago the earth was but a noodle wild west