#evolition

While teliphones are building calamite catacombs, few vertebrates have mastered the arid terrain. One of them was the first angarovenator - Lapideusunguis adam, the "stone nail", which occupied a niche similar to modern geckos.

Lapideusunguis is significantly smaller than Moropiton and, possibly, slightly larger than adult Ariekanerpeton individuals.

Clockwise from top to bottom: Moropiton moropiton ssp. pushkini, pearl mole spider, Lapideusunguis, Oxykoilia, Poseideongenia. In the background - Ichthyocetus megalos

The body is elongated, has a triangular shape in cross section due to the high raised ribs: the thickness from the head to the middle of the tail remains the same. The legs are longer than those of the ancestors, which allows you to travel long distances.

The fingertips are covered with a keratin cover, convergent to the fingertips of tree frogs: they protect the foot from hard and often very hot/cold soil and aggressive substances and allow effective digging.

One recent scientific paper (Evolutionary origin of Hoxc13-dependent skin appendages in amphibians - the pictures above are taken from there) suggests that the claws of amphibians and amniotes were not independently developed, as previously thought. This means that the common ancestor had keratinized fingertips like modern axolotls.

The skin is much thicker (especially the feet and eyelids) than that of the ancestors, but without scales: it hangs slightly at the edges of the trunk. The muzzle is pointed, the head is narrow; the parietal eye is developed, the pupils of ordinary eyes are vertical due to the need to hunt both in the morning sun and in almost complete darkness. The color is bright due to the absence of predators with developed eyesight and serves as a means of communication and recognition of each other at a distance.

Unlike sedentary discosaurids, lapideusunguis is a nomad. Although its anatomy does not allow it to move as fast as modern quadrupeds, this angarovenator constantly (once every two weeks) surveys its territory in search of arthropods. Usually the territory includes two or three calamite catacombs or the usual burrows of some Arachnetiflopontics - Lapideusunguis periodically hunts them, as well as spiders and insects, especially young individuals. His main time of activity is twilight, night and day, he waits in burrows dug by himself or abandoned phone burrows. In the evening, the angarovenator comes out before sunset and basks on the rocks; in the morning it warms up by contracting muscles like some modern pythons - another adaptation important for future evolution.

Another important difference from discosaurids is rapid maturation: instead of 20 years, the larvae mature in a few months. In general, reproduction for lapideusunguis as for amphibians in the desert is a hemorrhoid due to the need to search for a reservoir. Usually, adults are found near the catacombs at night, when rare rains fall. The female lays eggs on wet ground, the male fertilizes the eggs and the female swallows the future offspring like the recently extinct Rheobatrachus silus frogs, after which she drinks some water.

Famous Rheobatrachus silus photo

However, these seymouriamorphs have not yet developed this behavior to perfection, and therefore they usually search for the nearest large body of water, migrating to the remaining forest regions. During the mother's wanderings, the eggs manage to develop into larvae at the beginning or middle of metamorphosis. It is obvious that the following daughter species will abandon the habitat stage in lakes and puddles in favor of throat gestation.

Palaeontologists have previously struggled to work out how this rainforest collapse affected the first ancient vertebrate animals that lived there – the early tetrapods. This is because the fossil record for this time is patchy and incomplete. My colleagues and I have now published new research that reveals how the collapse initially caused the number of species to fall, affecting water-loving amphibians the most. But this event ultimately paved the way for the ancestors of modern reptiles, mammals and birds – known as the amniotes – to flourish and spread across the globe.

About 310m years ago, long before the first dinosaurs and mammals evolved, North America and Europe lay in a single landmass at the equator covered by dense tropical rainforests, known as the “coal forests”. The warm, humid climate and rich vegetation provided an ideal habitat for amphibian-like early tetrapods. This allowed them to quickly diversify into a variety of species.