Animals - Late Carb

Carboniferous 360-300mya

Plants Vascular Micro-aggregation Early Soils
Animals - Early Origin of Insects Oribatids - lower

Animals

Deadly poisonous centipedes two metres long crawled in the company of mammoth cockroaches and scorpions as much as a metre long. A millipede-like Arthropleura is the largest-known land invertebrate of all time. Most impressive of all were dragonflies that grew to the size of seagulls. An exquisitely detailed fossil of a dragonfly that died 320 million years ago had a wingspan of 0.75m.

The giant millipede Arthropleura would have been one of the largest invertebrates ever, 'living over 300 million years ago'. A fossil of the huge creature found in Northumberland is at around 2.6 metres, similar to that of a small car. "Lower delta plain depositional environment supports the contention that Arthropleura preferentially occupied open woody habitats, rather than swampy environments,

There were much higher levels of oxygen – up to 35% instead of 21% - higher than today, and warm and wet, which these creatures made the most of. It means some creatures were much larger then than they are today - like dragonflies and scorpions.

But what did they do for the soil? The centipedes, cockroaches and centipedes would all be walking and running round on the surface, but it is hard to see how larger these sorts could invade the newly formed soils. It is most probablt that centipedes ate many springtails, and scorions ate the centipedes, setting up a food chain based in the soil.

Most of the creatures in this period are now found all over the world. With the formation of Pangea, we can take stock of the overall state of soil creatures. It is surprising that most groups of soil animals are found across the world. implying most soil animal evolution had occurred by this period. The major exceptions are earthworms and higher oribatids, which is a story we will find out about later. The creatures here would have the whole of Pangea to explore in the next period While you can find the same groups across the world, many are divided into species with quite specific niches - presumably because movement in soil is very limited.

There were ground-dwelling predators, like scorpions, living across the surface of the sands and mud, able to move quickly out of danger. They were predators of other primitive arthropods, as today most are predatory on insects, like cockroaches. Again, we see a marked similarity between fossil and recent forms in overall body plan and morphology suggesting few changes over hundreds of millions of years, and have survived when the dinosaurs did not.

Cooperation or Competition

There we find a combination of characters and components, working ‘cooperatively’ at all levels. This is from basic chemistry of minerals interacting with single celled organisms (nano-plankton), to more complex fungi and rotifers and nematodes with small arthropods, various worms, simple and vascular plants, and all together producing the structures that provide living spaces as well as protection from all sorts of temperature, pressure and humidity changes.

When I say ‘cooperatively’ this is because there is talk about cooperation among soil creatures rather than competition. We’ve already seen how roots and fungi get on, how bacteria live in arthropod guts, and there are a myriad of other such relations. Most of the many grazers do not compete for food sources, as they feed generically -they do not rely on niche food. Many soil arthropods may prefer certain feedstocks, but generally will eat other stuff if around. This is very common practice underground.

In my agricultural zoology classes I was taught endlessly that ‘competition’ dominated population dynamics – fighting for limited resources. Of course, it is important. But there is more to life, and death. Some people talk about ‘survival of the fittest’, quoting Darwin, to claim meaning that life means fighting over anything, whereas it really means ‘best fitted to the environment’; that does not have to involve fighting.

There was a long debate in the 1950’s as to whether external elements (like food) controlled populations, or whether internal factors ought about self-control. Mites in particular can adapt to less favourable conditions without competing with others. Not only can they roll up in balls they can change the way they reproduce that doesn’t use as much energy. It is said that conditions in soil are harsh enough to prevent overproduction leading to competition?

Do you believe that we should put values like ‘cooperation’ or ‘competition’ on soil communities. Soil populations are pretty stable. Till we came along. They may be running round eating each other on the earth, but not in the earth. (revisitCooperation Among Animals, With Human Implications W C (Warder Clyde) 1885-1955 Allee (creator)

Oribatids - lower

Any soil would have had Oribatids. There are 12,000 species although there may anywhere from 60,000 to 120,000 total species. Oribatid mites are by far the most prevalent of all arthropods in forest soils, and are essential for breaking down organic detritus and distributing fungi

There are loads of soil mites – all sorts of different sorts - they are everywhere.’ Today we find oribatid mites all over. Many have strong outer coverings and are called 'Armadillo mites'. But these were not around in this Period. Here we encounter 'lower' oribatids.

Survival

These mites seem capable of withstanding drought by rolling up in a ball. These animals completely retract appendages into a secondary cavity and encapsulate themselves. (Schmelzle & Blethgen 2019) It is another 150 million years before we see how ants learned to crack the carapace of the higher oribatids.. They can also stay put for as long as it takes, relying on trehalose to withstand the conditions for long periods of time. This is the exact opposite way to dealing with dryness as springtails – which jump away. The oribatid way paved the way, accidentally, for dealing with other adverse conditions.

Oribatid mites generally have low metabolic rates, slow development and low abundance of offspring. Species have multiple reproductive cycles over the course of its lifetime, with adults living a relatively long time. Many oribatid mites give birth to live forms (parthenogenic) at various times Apparently, sex uses a lot of energy. So there are complex debates about why some animals do sex or are parthenogenic.

We saw that oribatids were pretty well established in the soil web 380 mya, but they really come into their own in this later Carboniferous period, with six genera turning up around 330 mya. “This diversity of oribatid mite lineages, which originated in the Palaeozoic, suggests that this group of mites was already functionally diverse in early soils, and that these mites have been evolving within the soil-system ever since… Early-derived species are dominantly small and elongated but oribatid mite evolution was accompanied by various shifts in these traits during the Devonian and Carboniferous. The round to ovoidal body form was fixed in higher oribatid mites at the end of the Carboniferous.” (Schaefer & Caruso 201). For more on Oribatids in this Period.

Oribatid evolution

400-360 mya (Late Devon)
330-300mya (Late Carb)
300 -250 mya (Permian)
Higher (200-145 mya Jurassic)
Mites (145-66 mya (Cretaceous)

Insects

Dragonflies and damselflies

Odonata appear an ancient lineage, probably originated during the Carboniferous. The fossil record suggests that during the Pennsylvanian (323–298 My) and the Permian (298–251 My), stem-odonates both diversified and were ubiquitously distributed, including often famously large griffinflies and the more gracile damselfly-like †Archizygoptera (Li et al., 2013; Nel and Huang, 2009; Nel et al., 2012). They are the first flying insects and pose a fascinating question as to how later insects evolved their ability to fly - from dragonflies? And was their life history - a series of water living nymphs hatching into airborne adults - also adopted?

Cockroaches

The Carboniferous is sometimes called the ‘Age of Cockroaches’ because insects broadly resembling modern roaches flourished during that era. Cockroaches had been before – over 350mya. Ancient cockroaches looked very much like this modern one, Macropanesthia rhinoceros... There were 'roachoids' before cockroaches, like this these over 330 mya This creature from 300+mya has been reconstructed in 3D and called Anebros phrixos ‘young and bristling’ (where it is referred to as juvenile or 'nymph'. But was it a ‘nymph’, or a creature that existed like this in its adult form? Later it could have evolved another stage in development later - with wings, like cockroaches.

Where do the vast majority of insects come from? How could they arrive?

The insects at this period were able to live on land because they had key characteristics of a protective skin, could breathe air, poo efficiently and have sex. How did they come to have those characteristics? Where did they come from? Could it have been like ‘manna from heaven’ , ‘magic’ or ‘the great leap to land’? Those characteristics – if you believe in evolution – would have taken tens of millions of years to evolve.

Macropanesthia rhinoceros

Anebros reconstructed

Worms

We have seen in the earlier part of this period, enchytraeid worms would have been burrowing, pushing their way through, leaving a tunnel behind, perhaps even tracks. Those tunnels open up the soil pores to loads of other smaller creatures, like mites, to explore.

Penis worms

There were no great earthworms moving massive lumps of earth around. The first true priapulids (penis worms) appeared during this period. Priapulans inhabit soft sediments, with larger species found in very soupy muddy bottoms. Some of the smaller species live in sandier sediments, where there is considerable interstitial space for movement. They are considered predators feeding on smaller worms in the mud. Their diversity when they appear shows that these arthropods were both well developed and numerous. It is likely they played some role in soil development, but that may have been feeding on eel worms (nematodes) pot worms (enchytraeids) which were numerous in the early part of this period.

Woodlice

The first Isopods were marine isopods which were around in this Carboniferous period. “By evaluating phylogenetic studies, palaeobiogeographic context of fossil specimens and current biological considerations, we support a pre-Pangaean origin…most likely during the Carboniferous." (Brolly & Maillet 2013).

Present-day woodlice are the only order of Crustacea that are terrestrial. The name woodlouse (plural woodlice) is descriptive of their being found in old wood. If ever there was a living fossil, this is it – and it looks like it when scurrying away from under a pot or stone.

Woodlice are a key group to study the “’conquest of the land’ among arthropods because of their interesting gradation of morphological, physiological and behavioural adaptations for terrestriality. However, the origin and evolution of this model group are still poorly known." (Brolly & Maillet 2013). They look like they did millions of years ago, which is like lots of animals that have spent millions of years underground! But they must have had stable damp conditions to do so. Were these conditions present at this time, or did they arrive much later?

Spiders

We saw, when the litter was being laid down 400-350 mya, the emergence of spider-like creatures, but none with proper silk making facilities. The oldest known spider fossil comes from the Montceau-les-Mines, a coal seam in eastern France. That spider was 305 million years old. (Perrier & Charbonnier 2014) The newfound fossil from the same time period reveals that these ancient spiders lived alongside not-quite-spider cousins.

Most of the early fossil spiders from the Coal Measures of Europe and North America probably belong to a group of spiders with the spinnerets placed underneath the middle of the abdomen. It was probably used then to make a protective covering for their eggs, or lining holes. It was not for another 25 million years before we can see spiders producing silk at the end of their abdomen – and used to catch creatures.

There were no holometabolous insects at this period. There were no beetle or fly larvae living in these early soils

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