Animals

Triassic 250-200mya

Palaeosols Plants Lichens Insects

Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event (like soil mites), new groups that flourished briefly, and other new groups (many beetles, grasshoppers) that went on to dominate and are still present to this day. Many ground animals did not go through any extensive evolutionary advances during the Triassic, but their survival and adaptions did provide a launch pad for later radiations. Insects developed a key characteristic that was to provide a major advantage as time went on - holometaboly.

“Clearly, the post-apocalyptic ecosystem on land was a caricature of a natural system. Not only was it unbalanced but it seemed to be almost identical worldwide”

Lystrosaurus

The early part of this Triassic the world was filled by a single reptile, Lystrosaurus, a dog-sized pig-looking herbivorous reptile that made up 95% of the fauna. It has been suggested that Lystrosaurus survived and became dominant because its burrowing life-style that made it able to cope with an atmosphere of "stale air". Wear on the tusks indicates that the animal used them for digging or rooting out vegetation. It was a herbivore that ate small plant life. Although it was not high on the food chain, it thrived largely due to the absence of predators after the End-Permian extinction. They gave rise to the ‘age of reptiles’ later on in this period, as dinosaurs first walked the earth.

How did their rooting around and pooing help the soil survive?

Soil breathing

The Collembola – those living fossils – would have eaten many of the soil-living bacteria, perhaps consuming dead bacteria too, and passed on their spores to where they would be feeding – on root fungi. It seems there was an ancient transition in Methylobacteriaceae ('methane munchers') ancestor from a free-living lifestyle to association with plant roots occurred (Leducq et al., 2022)

Oxygen heavier than methane

We need to try and work out the relation between methane and oxygen environments. How would they have co-existed? The molecular weight of each is the sum of the atomic masses of all atoms in any molecule, in which the atomic masses of hydrogen, carbon, nitrogen, and oxygen are 1, 12, 14, and 16, respectively. Methane (CH4) adds up (C=12 + H=1+1+1+1 ) to 16 while the weight of molecular oxygen O2 in the air is (2 X16) 32 –making it twice as heavy as methane in the atmosphere. So the oxygen would fall to ground and aerate the soil.

However, we have to pause here, and remember that springtails are aerobic, whereas many of the 'methane munching' bacteria could live in methane dominated air. How did the springtails survive? Luckily, oxygen is heavier in the air than methane This may have saved life on earth; the oxygen would have fallen to the ground. This would have helped enable the soil to keep breathing - ie. running aerobically. Clearly this is important for the survival of the earth. The springtails, mites, symphylans and enchytraeids would be able to live and the maintain the main soil functions.

While the animals on earth were pretty well wiped out, those below survived. They must have. It is strange to think that that relative molecular weights of two molecules and the dull sounding methane eating bacteria may have saved the world for all the evolution that followed.

From 400-360 mya Springtails

Springtails

There wasn't much radiation of springtails. The Neelidae, Entomobryomorphs and Poduromorphs would all still be springing about while the Sminthuridae were yet to arrive.

Oribatids

There was a major development among oribatid mites. Some seem to have changed eating, (red arrow), presumably to cope with the after math of the EPE

Their great radiation happens during the next 100 million years..

From Oribatids - Higher

Funky Worms

Worm-like creatures called caecilians (Gymnophiona) have been found in Arizona's Petrified Forest Park. These Caecilians are a family of legless, salamander-adjacent, cylindrical bodied, burrowing creatures (Kligman et al 2023)

Microscopic jaw

Funcusvermis

The name of the amphibian ancestor, Funcusvermis, is a Latinized way of saying “Funky Worm” after an Ohio Players’ 1972 song of the same name from their album 'Pleasure'.

Modern caecilians are limbless amphibians with cylindrical bodies and a compact, bullet-shaped skull that helps them burrow underground. Now exclusively home to South and Central America, Africa, and southern Asia, caecilians spend their lives burrowing in leaf litter or soil searching for prey such as worms and insects. Did they appear in Gondwana as Pangea was splitting? And did they then feed on insect larvae or were they after enchytraeids?

First Oligochaete?

Oligochaetes are in the class Annelids, which include present-day earthworms. One Oligochaete fossil has been found in this period, but it may well have been marine. Otherwise there is still no sign of earthworms as we know them today.

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