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Description

Finding alternate universes with divergences so deep and ancient is a fascinating and interesting event to study, only a substantially insignificant change at the moment ends up being a chain effect that modify the dynamics the evolutionary panorama in a way that makes these parallel worlds almost extraterrestrial, with worlds where certain lineages of animals never evolved, strange conditions or events that never happened, the deep and drastic possibilities turn out to be impressive. And here comes one of those worlds, one that goes to the roots of the primordial terrestrial life colonization that was coming out to take all over the land, however this has not colonized by the tetrapod quadrupeds, but from another extravagant clade of vertebrates, these came from one of cartilaginous skeletal lineages, but unlike most it had a dermal armor around its head and front part of the body, a prolific lineage that had conquered oceans, coasts and fresh water, expanding during the golden age of fish in different ecological niches, from the great predators, filter feeders, several medium carnivorous forms and the compact detritivores, the placoderms. They had their peak in the Devonian; however they had a sudden end during the mass extinction of the end of the period, taking them all to their doom ... except for a clade in this case, and this is how everything changes.

This alternative world has a point of divergence with double event during the end of the Devonian (light blue), the first would be the survival of a more successful placoderm clade, the Antiarchi, a type of quite armed form of robust body and by having characteristics articulated extremities as of arthropods; while the second would have enough consequences with the future of the Antiarchi, the absence of tetrapods or advanced groups of Sarcopterygii, which by luck or by some event disappeared or simply never existed, and with these conditions, would give way to the emergence of a totally divergent and strange clade of terrestrial placoderms.

The Carboniferous period (Dark Green) is a slightly different landscape, the enormous primordial tropical forests with the varieties of titanic arthropods, however, there are no amphibians like the Temnospondyls, or some of the earliest amniotes, but rather strange varieties of creatures covered in armor, slowly moving and limited by their heavy anatomy, this would be the descendant lineage of the Antiarchi that still exists in the bottom of the rivers. These first colonizers are descendants of a particular fish that developed their pectoral fins as limbs, almost like a crab in appearance, is able to stick them in the mud or bark of fallen trees, these are the Efferoterrus, similar to a jumping Mud, move through the coasts. They have been able to develop a separate lung due to their oxygen-free environment, being able now to resist time out of the water unlike others of its kind. From this other lineages were branched, some already being similar to the non-existent tetrapod amphibians with developed hind and forelimbs, among the most prominent are the ferocious Reptensarchia, which are the main semi-aquatic predators with heavy sharp jaws, some with teeth or others as beaks, they vary in size from some small species of 10 cm to titans of 3 meters in length; in the other spectrum are the Tyreoliposida, very calm and titanic herbivores, which move slowly and safely from the great hunters, with specimens up to 2 meters long and weighing more than 100 kg. Both of these clades are characterized by having both their fully functional back and front limbs, in addition to their predominant armor, since the lack of an appropriate mineralized skeleton all its support is mainly in the dermal plates structured in shells. Among the scavengers, small omnivores and terrestrial detritivores are the snake-like Scutophids, extremely long and narrow forms, only possessing a minimum part of the body covered by a cylindrical shell, with a retractable eye stalk which has both eyes at the tip.

Into the Permian (Yellow) and the desertification of the super pangea continent, these armored vertebrates had to face the ecological changes that force them to adapt and evolve in new and varied forms, of course dealing with the lack of a bony skeleton and the presence of an amphibious respiratory system. The remaining Antiarchi originals, the Scutophids, like the Efferoterrus remained relegated to the waters, while varieties of the large quadruped clades became scarce from the middle of the Permian, until extinct before the Great Death. Nevertheless this would not be the end of the terrestrial conquerors, since of some several small clades of Efferoterrus came one in particular that dealt adequately with arid environments. The Pherotria, a clade that had evolved from semi-arboreal ancestors that developed a single third limb by joining both the tail and its two pelvic fins, and also modifying the structure of the front leg that allowed them to support them with their tips constantly, with a scaled skin capable of retaining water inside the body. Like a reptilian crab they are able to cross the drier regions of the continental territory, expanding and taking the available niches, however, being just limited in size due to their cartilaginous skeleton, with few species capable of reaching lengths greater than one meter in length. On the side of the Scutophids as well emerged a variety better adapted to dealing with the lack of water, the Chirognathids, which evolved the same kind of skin covering with scales, and changing the function of the front legs to function as mouthparts, reduced eyestalks, and a cylindrical body which is much more articulated, with separated rectangular plates across the body.

At the end of the Permian and the overwhelming mass extinction was the end for most of the early terrestrial placoderms, being a small amount belonging to certain lineages, the Antiarchi, the Pherotria, the Scutophids and the Chirognathids the lucky survivors.

The Triassic (Light green) would a culminating point for the surviving terrestrial placoderms, with an explosion of diversity throughout the period, almost as occurred in our timeline with the various tetrapod reptiles. During the period several species with forms and behaviors arose that although most of them would lead to dead ends, some others began to derive and became the ancestors of the next wave of dominant animals in the Mesozoic, being the most prominent the Allobrachids, characterized by its more structured forelimbs that allows better movements and a more appropriate upright posture, has a mobile neck, the development of a differentiated arm and forearm, a rigid pseudo-tail for the balance and the modification of the third limb with long and articulated bones, with a foot of 5 fingers. Another important aspect that would differentiate them from the others would be the development of a mineralized skeleton, which provide sufficient support for larger forms. In the trees extend the Cladeorepenid, characterized by their thinner long limbs and more round and compact anatomy, these are adapted to climb and live on trees. Among the terrestrials, the Bulbosuterid are the first megafauna’s terrestrial placoderms that have appeared on the planet, with species capable of reaching up to 2.5 meters in height and weighing up to 300 kg. And of the most medium-sized and agile types are the Allopeda, jumping creatures which only use their long back foot to mobilize, are mostly omnivores.

The Chirognathids had their radiation as well with two main clades that eventually took important niches of quite unusual ways, with the long and aquatic Sobekidenus that have conquered rivers, lakes and oceans with crocodile-like shapes, having prominent mouthparts long enough to catch and cut prey; The Graciloplacodia are bizarre terrestrial Chirognathids which are able to stand on their pectoral limbs, which alongside with their vertebrae column have adapted to support their weight in such posture, being able to reach the foliage of tall branches, these as the majority of Relatives have mouth parts to grasp the plants and with their true jaws cut and eat them.

-----------------------------------------------

For some time I wanted to make a project dedicated to the evolution of terrestrial placoderms strongly inspired by the impressive high derived Antiarchi tripod created by Memo Kosemen . I already had done some sketches as well individual pictures of the evolution and diversity of such creatures, and eventually I tried to make a peculiar sapient species derived from these for my project Alternative Paths , however, I never felt really satisfied with the way I was developing it, so by that point I re-started again, something like I've done with TFIF and Cambrian Mars, I tried to work everything from 0 and start doing the basics and thus have a final result much more constructed and more divergent than I had planned. This is probably one of many random updates I would do for this project that will come eventually.

Description

Finding alternate universes with divergences so deep and ancient is a fascinating and interesting event to study, only a substantially insignificant change at the moment ends up being a chain effect that modify the dynamics the evolutionary panorama in a way that makes these parallel worlds almost extraterrestrial, with worlds where certain lineages of animals never evolved, strange conditions or events that never happened, the deep and drastic possibilities turn out to be impressive. And here comes one of those worlds, one that goes to the roots of the primordial terrestrial life colonization that was coming out to take all over the land, however this has not colonized by the tetrapod quadrupeds, but from another extravagant clade of vertebrates, these came from one of cartilaginous skeletal lineages, but unlike most it had a dermal armor around its head and front part of the body, a prolific lineage that had conquered oceans, coasts and fresh water, expanding during the golden age of fish in different ecological niches, from the great predators, filter feeders, several medium carnivorous forms and the compact detritivores, the placoderms. They had their peak in the Devonian; however they had a sudden end during the mass extinction of the end of the period, taking them all to their doom ... except for a clade in this case, and this is how everything changes.

This alternative world has a point of divergence with double event during the end of the Devonian (light blue), the first would be the survival of a more successful placoderm clade, the Antiarchi, a type of quite armed form of robust body and by having characteristics articulated extremities as of arthropods; while the second would have enough consequences with the future of the Antiarchi, the absence of tetrapods or advanced groups of Sarcopterygii, which by luck or by some event disappeared or simply never existed, and with these conditions, would give way to the emergence of a totally divergent and strange clade of terrestrial placoderms.

The Carboniferous period (Dark Green) is a slightly different landscape, the enormous primordial tropical forests with the varieties of titanic arthropods, however, there are no amphibians like the Temnospondyls, or some of the earliest amniotes, but rather strange varieties of creatures covered in armor, slowly moving and limited by their heavy anatomy, this would be the descendant lineage of the Antiarchi that still exists in the bottom of the rivers. These first colonizers are descendants of a particular fish that developed their pectoral fins as limbs, almost like a crab in appearance, is able to stick them in the mud or bark of fallen trees, these are the Efferoterrus, similar to a jumping Mud, move through the coasts. They have been able to develop a separate lung due to their oxygen-free environment, being able now to resist time out of the water unlike others of its kind. From this other lineages were branched, some already being similar to the non-existent tetrapod amphibians with developed hind and forelimbs, among the most prominent are the ferocious Reptensarchia, which are the main semi-aquatic predators with heavy sharp jaws, some with teeth or others as beaks, they vary in size from some small species of 10 cm to titans of 3 meters in length; in the other spectrum are the Tyreoliposida, very calm and titanic herbivores, which move slowly and safely from the great hunters, with specimens up to 2 meters long and weighing more than 100 kg. Both of these clades are characterized by having both their fully functional back and front limbs, in addition to their predominant armor, since the lack of an appropriate mineralized skeleton all its support is mainly in the dermal plates structured in shells. Among the scavengers, small omnivores and terrestrial detritivores are the snake-like Scutophids, extremely long and narrow forms, only possessing a minimum part of the body covered by a cylindrical shell, with a retractable eye stalk which has both eyes at the tip.

Into the Permian (Yellow) and the desertification of the super pangea continent, these armored vertebrates had to face the ecological changes that force them to adapt and evolve in new and varied forms, of course dealing with the lack of a bony skeleton and the presence of an amphibious respiratory system. The remaining Antiarchi originals, the Scutophids, like the Efferoterrus remained relegated to the waters, while varieties of the large quadruped clades became scarce from the middle of the Permian, until extinct before the Great Death. Nevertheless this would not be the end of the terrestrial conquerors, since of some several small clades of Efferoterrus came one in particular that dealt adequately with arid environments. The Pherotria, a clade that had evolved from semi-arboreal ancestors that developed a single third limb by joining both the tail and its two pelvic fins, and also modifying the structure of the front leg that allowed them to support them with their tips constantly, with a scaled skin capable of retaining water inside the body. Like a reptilian crab they are able to cross the drier regions of the continental territory, expanding and taking the available niches, however, being just limited in size due to their cartilaginous skeleton, with few species capable of reaching lengths greater than one meter in length. On the side of the Scutophids as well emerged a variety better adapted to dealing with the lack of water, the Chirognathids, which evolved the same kind of skin covering with scales, and changing the function of the front legs to function as mouthparts, reduced eyestalks, and a cylindrical body which is much more articulated, with separated rectangular plates across the body.

At the end of the Permian and the overwhelming mass extinction was the end for most of the early terrestrial placoderms, being a small amount belonging to certain lineages, the Antiarchi, the Pherotria, the Scutophids and the Chirognathids the lucky survivors.

The Triassic (Light green) would a culminating point for the surviving terrestrial placoderms, with an explosion of diversity throughout the period, almost as occurred in our timeline with the various tetrapod reptiles. During the period several species with forms and behaviors arose that although most of them would lead to dead ends, some others began to derive and became the ancestors of the next wave of dominant animals in the Mesozoic, being the most prominent the Allobrachids, characterized by its more structured forelimbs that allows better movements and a more appropriate upright posture, has a mobile neck, the development of a differentiated arm and forearm, a rigid pseudo-tail for the balance and the modification of the third limb with long and articulated bones, with a foot of 5 fingers. Another important aspect that would differentiate them from the others would be the development of a mineralized skeleton, which provide sufficient support for larger forms. In the trees extend the Cladeorepenid, characterized by their thinner long limbs and more round and compact anatomy, these are adapted to climb and live on trees. Among the terrestrials, the Bulbosuterid are the first megafauna’s terrestrial placoderms that have appeared on the planet, with species capable of reaching up to 2.5 meters in height and weighing up to 300 kg. And of the most medium-sized and agile types are the Allopeda, jumping creatures which only use their long back foot to mobilize, are mostly omnivores.

The Chirognathids had their radiation as well with two main clades that eventually took important niches of quite unusual ways, with the long and aquatic Sobekidenus that have conquered rivers, lakes and oceans with crocodile-like shapes, having prominent mouthparts long enough to catch and cut prey; The Graciloplacodia are bizarre terrestrial Chirognathids which are able to stand on their pectoral limbs, which alongside with their vertebrae column have adapted to support their weight in such posture, being able to reach the foliage of tall branches, these as the majority of Relatives have mouth parts to grasp the plants and with their true jaws cut and eat them.

-----------------------------------------------

For some time I wanted to make a project dedicated to the evolution of terrestrial placoderms strongly inspired by the impressive high derived Antiarchi tripod created by Memo Kosemen . I already had done some sketches as well individual pictures of the evolution and diversity of such creatures, and eventually I tried to make a peculiar sapient species derived from these for my project Alternative Paths , however, I never felt really satisfied with the way I was developing it, so by that point I re-started again, something like I've done with TFIF and Cambrian Mars, I tried to work everything from 0 and start doing the basics and thus have a final result much more constructed and more divergent than I had planned. This is probably one of many random updates I would do for this project that will come eventually.