DEVONIAN
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DEVONIAN
419.2 - 358.9 mya
The Devonian is a period of the Paleozoic era, spanning a little over 60 million years, being preceeded by the Silurian period, which ends 419.2 mya, and being followed by the Carboniferous period, that starts 358.9 mya. By the middle part of the period, diversification of vascular plants with leaves and roots was on the rise, with the very first seed-bearing plants (the so called "seed ferns" appear around the mid-late Devonian). The Devonian is nicknamed the Age of Fishes, as fish diversified into dominant aquatic organisms, especially the jawed fish, in this period.
The Devonian period was named after The Great Devonian Controversy, an argument in the 1830s between geologists Roderick Murchison, Adam Sedgwick and Henry De la Beche over the age and structure of rocks of the county of Devon, England; the Devonian period was therefore added to the geological time scale to settle this debate, which was won by Murchison and Sedgwick. In the 19th century, the Devonian was nicknamed the "Old Red Age" in reference to the often red and brown deposits from that age found across the United Kingdom, with old literature dividing the Anglo-Welsh basin into the Downtonian, Dittonian, Breconian and Farlovian stages, with only the latter three actually placed in the Devonian period. The climate of the Devonian varied across time, ranging from a more arid climate in the early parts of the period and gravitating towards a lesser arid and more temperate climate in the late Devonian.
The Devonian period is formally divided into the Early (419.2 - 393.3 mya), Middle (393.3 - 382.7 mya) and Late (382.7 - 358.9 mya) Devonian periods. The early Devonian, divided in three stages, Lochkovian (419.2 - 413.2 mya), Pragian (413.2 - 410.6 mya) and Emsian (410.6 - 393.3 mya), was a period of origin for the ammonoids, typically coiled-shelled cephalopods that, at the time, were still very much similar to other shelled cephalopods, like the nautiloids. The middle Devonian, divided in two stages, Eifelian (393.3 - 387.7 mya) and Givetian (387.7 - 382.7 mya), was a period with shallow warm inland waters, depleted of oxygen due to the overgrowth of primitive plants, leading early lunged air-breathing fish to slowly develop the capacity to move on land, at least for short periods of time, eventually giving rise to the late Devonian, divided in two stages, Frasnian (382.7 - 371.1 mya) and Famennian (371.1 - 358.9 mya).
During the Devonian period, the temperature gradient between the poles and the equator was, for the most part, not as large as today. Carbon dioxide levels dropped steeply throughout the period, due to the large rise of terrestrial plant life.
In the early Devonian, the continents of Laurentia and Baltica collided to form Laurussia (or Euramerica), and as they joined they formed mountain ranges, such as the Acadian Orogeny (manifesting today as the Appalachian mountains) and the Caledonian Orogeny, forming the Caledonian mountains of Great Britain and Scandinavia; as the Caledonian Orogeny wound down in the later part of the period, orogenic collapse facilitated a cluster of granite intrusions in Scotland. For much of the period, the western parts of Laurussia (corresponding to North America) were bathed by subtropical inland seas, hosting a diverse array of marine reef life. In the early-mid Devonian, the western laurussian coast was a passive margin with broad coastal waters, deep silty embayments, river deltas and estuaries, found today in Idaho and Nevada. Many of the Devonian collisions in Laurussia produce both mountain chains and foreland basins, which are frequently fossiliferous. In the southern part of the globe, the mighty continent of Gondwana persisted, being surrounded by smaller asian microcontinents, such as the South China-Annamia continent, being the most recent devonian addition to the asian terranes. Volcanic activity was abundant in these continental chaos, such as nearby the continent of Siberia, in the microcontinent of Amuria (corresponding to today's Mongolia and Manchuria). The exact position of Amuria is somewhat uncertain due to contradictory paleomagnetic data. The Rheic ocean, separating Laurussia from Gondwana, shrunk steadily throughout the period as the two continents approached each other near the equator, teasing the future formation of Pangaea. The closure of the eastern part of the Rheic is associated with the assemblage of central and southern Europe. Parts of Gondwana, corresponding to the central european terranes of Franconia and Saxothuringia, collided with Laurussia at the end of the early Devonian, pinching the easternmost parts of the Rheic. The sequence of rifting and collision events that followed led to the successive creation and destruction of several small seaways, including the Rheno-Hercynian, Saxo-Thuringian, and Galicia-Moldanubian oceans.
Across much of the Devonian, sea levels were generally high. Reefs were built out of various carbonate-secreting organisms, erecting wave-resistant structures near sea level. On land, the biota inherited from the Silurian period, continued to diversify, with micro forests of early moss relatives, bacterial and algal mats, and diversifying primitve rooted plants that allowed stabler soils for arthropods, such as mites, scorpions, trigonotarbids and myriapods, to flourish. Insects may have first originated in the early Devonian. Land plants were mostly composed of small primitive leafless organisms, such as Cooksonia, with dichotomous axes with terminal sporangia, being generally just a few centimeters tall. Trees start to be observable in the Devonian period, appearing in the lycopod lineage, as well as the woody cladoxylopsids and the progymnosperms, such as Archaeopteris. This expanse and diversification of plants across the Devonian landmasses acted as a major carbon sink, dramatically dropping the carbon dioxide levels globally. The expansion of plants with roots, specifically, revolutionized the speed of erosion and sediment deposition of soils. Due to this flourishing of terrestrial life, the final moments of the period eventually saw the otherwise aquatic vertebrates to seek a life on land.
Around the end of the Devonian, a major mass extinction occured, the Late Devonian extinction, occuring about 372 million years ago, in the late Frasnian, which primarily affected marine ecosystems, selectively affecting organisms from warm waters, in opposition to those that lived in cooler climates. The reasons behind this extinction have been debated, with some speculating it was caused by a violent asteroid impact and/or global cooling, but it was nevertheless quickly followed by the Hangenberg event, that terminated the period, with a lesser extinction event, 358.9 mya.
main source: Wikipedia
A Earth map reconstruction, some 390 mya
SUGGESTED SUBMISSIONS
(this space will be reserved to catalogue submissions done for this contest, simply for people to get a sense of what other people are working on)
Species (singular species submissions)
Species (singular species submissions)
Name: Pisciscrura secundus
Creator: AlDodo
Size: Around 1.9 to 2.8 meters long
Location: Canada
Time period: 372 mya
Clade: Animalia, Eumetazoa, ParaHoxozoa, Planulozoa, Bilateria, Deuterostomia, Chordata, Olfactores, Vertebrata, Gnathostomata, Eugnathostomata, Osteichthyes, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Choanata, Elpisostegalia, Stegocephali
The Devonian period, often rightfully nickamed the "Age of Fishes" due to the important increase in domination of all clades of fishes (jawless as well as jawed such as core placoderms, cartilaginous and lobe-finned fish), was an era notably marked by global warming, sometimes increasing step by step over the course of the period, which finalized with important extinctions due to the sea temperature changing dramatically and leading to numerous secondary effects, affecting water and so the animals inhabiting in it. That and the overgrowth of plants on land which, without major important or efficient herbivores to regulate them (insects and other arthropods at the time seem to not have been particulary large to have notable impacts in plant life to prevent this) also had important influcences on both the freshwater and oceanic life as a whole.
This included predominantly the important decrease in oxygen levels almost everywhere and even with regions where aquatic settings were seemingly almost entirely depleted of oxygen.
This ultimately saw the complete extinction of the "placoderms", a major decrease in the diversity of the sea scorpions, or eurypterids, and trilobites (which, after this, only survive as fossils in the form of proetids) and it also hit the first ammonites, which appeared before during this period, though these would later recover.
This general context would however trigger what would be among life’s last major evolutionary footsteps. Indeed, alongside plants on land further developing and truly massively blooming by this period, the depletion of oxygen in aquatic biomes would force some representatives of a group of lobe-finned fish, named sarcopterygiians, to adapt and seek fresh air outside of the water.
Overtime this led these fish to develop more specialized lungs to directly breathe air out of the water and pass more time to the water’s surface, see the shores, and ultimately leading some to even leave water momentarily.
This would make these animals the first land-venturing vertebrates.
These possibly included the genera Panderichthys and the famous Tiktaalik, the latter being often described as the "missing link" between more traditional fish and tetrapods, somewhat half-fish and half-tetrapod, fantasized as being at the very middle between the two. These animals represent a very restricted grade which are colloqually known as "fishapods".
But another fishapod akin to Tiktaalik, named Pisciscrura, existed.
Having existed in what corresponds to Late Devonian strata in western-south Canada, it was even closer to fully evolved tetrapods, being slightly more robust and with a physiology clearly more adapted to slightly more terrestrial lifestyles.
This semi-aquatic animal had stronger "fin-legs", especially the fore ones, and a shorter, more robust head and jaw. It’s body was proportionnaly shorter, rounder and less slender than the one of Tiktaalik. It’s eyes were slightly more elevated and directed slightly on this sides than the latter too, likely to see better the landscape's surroundings when on land.
It still nonetheless passed considerable time in water, reproducing in it and relying to it to keep its skin wet.
Overall, however, this animal was pretty similar to Titaaklik and anything which can be said or is known about that taxon is applicable on this younger, slightly more evolved relative.
Pisciscrura could be speculated to draw from the appearance of typical looking tetrapods, such as the stem-tetrapod (related but not yet true tetrapods) Acanthostega and Ichthyostega, which both lived around 365 mya ago, 7 millions years after Pisciscrura.
Clades (multiple related species submissions; 2 - 3 species)
Clades (multiple related species submissions; 2 - 3 species)
To be added
Ecosystems (2-6 species that live in one shared real or fictional ecosystem)
Ecosystems (2-6 species that live in one shared real or fictional ecosystem)
To be added
SUGGESTED EXTINCTIONS
(clades that are suggested to go extinct in this time period)
SUGGESTED EXTINCTIONS
(clades that are suggested to go extinct in this time period)
"Placoderms" (†358.9 mya): - The Devonian ultimately saw the complete extinction of the "placoderms", alongside a major decrease in the diversity of the sea scorpions, or eurypterids, and trilobites (which, after this, only survive as fossils in the form of proetids) and it also hit the first ammonites, which appeared before during this period, though these would later recover. (AlDodo)
SUGGESTED ECOSYSTEMS
(real or fictional ecosystems suggested by the community for other people to build into)
SUGGESTED ECOSYSTEMS
(real or fictional ecosystems suggested by the community for other people to build into)
Ucayali Formation / Peru (385 mya) - Some Cambrian fauna still persists into the Devonian, despite the increased competition from jawed fish pushing many over the brink. Despite this, the ones who remain still thrive even in the presence of fierce predators. The shallow water of Peru in particular is a hotspot where the old and new can interact. (IC1101)
CANON
CANON
OFFICIAL
(ultimate canonical compilation of submissions; official submissions, extinctions and ecosystems can only fall in this category after the deadline is over and proper judging can occur; I will have authority to canonize my own submissions before the deadline, however, and that information can be used by other people to build over the canon in anticipation)
OFFICIAL
(ultimate canonical compilation of submissions; official submissions, extinctions and ecosystems can only fall in this category after the deadline is over and proper judging can occur; I will have authority to canonize my own submissions before the deadline, however, and that information can be used by other people to build over the canon in anticipation)
SPECIES
Name: Neoselkirkia profunda
Creator: YellowPanda2001
Size: 1 to 5 centimeters long
Location: Western Panthalassa
Time period: 412 mya
Clade: Selkirkiidae, Selkirkiinae, Neoselkirkiini
During the early Devonian, in the Lochkovian stage, the deep sea was filled with a myriad of strange organisms, some of them part of lineages completely alien to fossil strata known from this period. In the abyss of western Panthalassa, hidden from the rest of the world, lie strange tubular organisms smaller than a human hand. These are Neoselkirkia profunda. These are members of the Scalidophora clade, containing our timeline's modern priapulids (penis worms) and kinorhynchs (mud dragons), as well as the enigmatic loriciferans. Resembling penis worms, Neoselkirkia and its fossilized kin have, however, inexact relationships to them.
Neoselkirkia has a very restricted distribution, and lives in the ocean floor. It is related to the fossilized Selkirkia from the Cambrian and Ordovician, forming a ghost lineage of about 110 to 60 million years. These would have formed conic tubes around their worm-like body, sitting under the sediment with only their soft head poking out, unless when threatened by predators, when it just hides under its shell. It has a long proboscis adapted to hunt small organisms moving or swimming in or near the surface of the sediment. Despite these relictual survivors seeming to be fine in these secluded deep sea paradises, they don't reproduce in the most obvious fashion. Neoselkirkia reproduce through parthenogenesis, and all individuals of this species are female. Females actually copulate with each other but only to trigger their assexual reproduction, with clones of themselves eventually being born. Its probable that this method of reproduction was what allowed this lineage to survive in these untouched environments for millions of years, surviving catastrophic extinction events in the meantime.
Name: Notoarthropleura maxima
Creator: YellowPanda2001
Size: 20 centimeters long
Location: Mozambique
Time period: 376 mya
Clade: Arthropleurida, Notoarthropleuridae
In the southern lands of Gondwana, during the Frasnian stage of the late Devonian, a plethora of life existed in these south polar lands. It wasn't a frigid landscape, but rather a forested environment filled with plant life. Under the various stems, a plethora of small organisms existed in a small archipelago of coastal islands, in what is today Mozambique, 376 million years ago. Isolated from the rest of the mainland, it was a land dominated by small arthropods, most of them smaller than a human's thumb nail. However, there were some giants.
The largest animal in the small island it was endemic to was Notoarthropleura maxima. It belonged to a family of arthropleuridans known as Notoarthropleuridae, characterized for its large size and gondwanan distribution (in opposition to the more tropical arthropleurids of the Carboniferous). Notoarthropleurids are in fact ancient relatives of the titanic Arthropleura from the Carboniferous period, but unlike them they could be found in less tropical climates and their sizes were generally smaller. Notoarthropleura itself was 20 centimeters long, already making it larger than any known fossil myriapod in the Devonian, and one of the largest land animals in its environment.
Notoarthropleura was an insular giant adapted to the relatively colder climate of the south. It lived in a time when atmospheric oxygen was surprisingly low, so much that the densely vegetated environment it lived in was surprisingly immune to forest fires. Nevertheless the environment was not always humid, so these large myriapods tend to gather near the coastal areas. It is a dedicated detritivore, and at this size, it has very few to no predators. It shares many features with Arthropleura, including the stalked eyes that may actually be a plesiomorphic trait inherited from basal non-myriapod euthycarcinoids, and perpetuated into the diplopod lineage. Notoarthropleura itself, alongside other arthropleurideans, are most surely stem-millipedes.
Name: Saxumorsus squalupellis
Creator: TheTiger773
Size: 40 centimeters long (full body)
Location: Shallow seas of southern Euramerica
Time period: 375 mya
Clade: Chordata, Olfactores, Vertebrata, Gnathostomata, Placodermi, Arthrodira, Smilidontidae
When one thinks of Placodermi, the first thing that comes to mind is the image of the fearsome Dunkleosteus - an armored "shark" of its time. However, not all of the traditional "placoderms", nor even just arthrodires, were just apex predators, similarly to aforementioned sharks of our timeline's Holocene. Arthodires, as a whole, were the most species diverse order of armored fish at the time, filling a wide array of niches, from small sediment dwellers to large predators and even filter feeders. Locally, they were getting even weirder than that. In the seas of southern Euramerica, among sparse reefs, lived a small family of arthrodires - Smilidontidae, or "chisel teeth". Their name mostly derives from their adaptations for feeding on hard shellled and/or slow moving prey, like brachiopods or mollusks. However, among their ranks, there was yet another strange fish - Saxumorsus squalupellis. This species, which is the sole member of its genus, in contrast to their carnivorous relatives, was an omnivore supplementing its diet with algae. However, how can an animal with such hard jaws feed on something so delicate? Simple, by scraping them right from the reefs themselves. This in turn makes them what is essentially a Devonian equivalent of parrot fish, even if the reef they gnaw on is composed of different organisms than those from Cenozoic times. Because of that, this fish was characterised by an unusually thick skull and strong jaws, powered by powerful muscles. While, just like other arthrodires, they don't have true typical teeth lining their mouths, they are equppied with flat and wide bony plates, covered with a layer of ever growing enamel to withstand constant wearing. Such feeding habits allow this species to play quite an important role in its ecosystem. However, one could wonder how such a peculiar animal didn't left any traces of its existence. There are several reasons for this. First, their size. Due to their smaller size, their bones were relatively easer to be carried away by water and scavengers. Secondly, its range. This species had a very limited range, so there are less places where fossils could be found. Third, their diversity. This species, and the rest of Similidontidae, were relatively poor in abundance. These are the main reasons they are absent from the fossil record. Unfortunately, they went extinct with the rest of their family during the Kellwasser Event, or Late Devonian extinction event, with the rest of the arthrodires going extinct after the start of the Hangenberg event delineating the end Devonian extinction.
Name: Thalassognathus intangibilis
Creator: MrBlueShark
Size: 1.6 meters long
Location: Central Panthalassa
Time period: 382.7 - 359.3 mya
Clade: Dipnoi, Thalassognathidae
This member of the lungfish lineage lived in a geologic formation that represents a deep sea benthic environment on the outer continental shelf some 200~ meters deep. It was consisted by a skeleton that indicates an animal of around 1.6 meters long. Its classification as a member of the lungfish lineage is interesting as it appears this lineage had moved from the shallow marine waters that Devonian dipnoians were common to, to deeper offshore waters. It belongs to its own distinct family, the Thalassognathidae, which might itself be related to the Dipteridae family. One could compare it to our timeline's modern Latimeria coelacanths in terms of niche. Being a slow moving predator of anything smaller than itself, with large front flippers to aid in steering and swimming, the blunt tooth-like plates indicate a diet of hard-shelled organisms like deep sea thylacocephalans, ammonoids and crustaceans. They appeared to have had large eyes which would have helped them catch the faintest of lights in the twilight zone. It had a very wide temporal range, ranging from the start of the Frasnian to the late Famennian, having survived past the Kellwasser event unscathed in the deep sea environments. In the Famennian stage, it would have coexisted with the large thylacocephalan Tenebricaris, which would occasionally hunt these fish, when young, though an adult could, in rare circumstances, be taken down by the large arthropod.
Name: Tenebricaris deceptorius
Creator: YellowPanda2001
Size: 50 centimeters long
Location: Central Panthalassa
Time period: 370 mya
Clade: Concavicarida, Concavicarididae, Tenebricaridinae
Shortly after the Kellwasser event (or the Late Devonian mass extinction) the life that narrowly survived the cataclismic extinction had a boom in diversity, in response to the eccological vacuum. Among the organisms that managed to endure the mass extinction more easily, were the deep sea organisms, in stark contrast with the coastal reef dwellers that took a big hit. Two million years after the extinction, a monster evolved in the depths: Tenebricaris deceptorius.
This is a giant deep sea predatory thylacocephalan, belonging to its own subfamily in the Concavicarididae family. This large predator is larger than most other thylacocephalans, measuring half a meter long, inhabiting the depths of central Panthalassa, in the early Famennian stage of the late Devonian. It has a very stout body, with rows of fins on the back to swim steadily in the water column, enormous eyes to see in the dark, and three pairs of large raptorial claws, filled with spines to catch any small creatures that might be a potential meal. Its most interesting characteristic is the asymmetrical frontal pair of limbs, where the left limb has one thing the right one doesn't have: a long stringy protuberance that ends in a fleshy and hairy dangly tip that resembles a small swimming shrimp-like arthropod. Quite like an anglerfish of our timeline's modern day, Tenebricaris uses this to lure small prey to its death. This fishing arthropod can, therefore, hunt much larger prey and, coupled with its large size, it is easily one of the most menacing predators of its environment.
CLADES
Name: Protoloukida
Creator: YellowPanda2001
Location: Oceans surrounding Gondwana
Clade: Eukaryota, Euanaerobia
While the Paleozoic is filled with hidden lineages of animals that were never or hardly fossilized, a much more cryptic world of unpreserved organisms exists in the microscopic realms. Single-celled lineages of strange origins and evolutionary backgrounds remain completely unknown to us, and an incredible diversity must have existed in the deep past without our knowledge. This is the case of the Protoloukida. This is a specific group of anaerobic eukaryote organisms that exist in the sediments in the shallow seas surrounding Devonian Gondwana. They're anaerobic for they lack mithochondria, despite being eukaryotes, but they're tolerant to aerobic environments. They ancestrally had mithochondria, but eventually lost them, belonging to a wider group of anaerobic basal eukaryotes, the Euanaerobia, which includes our timeline's parabasalids. Unlike parabasalids, protoloukidans are not parasites, and instead free living flagellated bacteriophages.
Name: Protoloukas mongoliensis
Size: 15 micrometers
Location: Mongol-Okhotsk ocean
Time period: 407 mya
Protoloukas mongoliensis is a species of protoloukid from the shallows of the Mongol-Okhotsk ocean. Like other protoloukids, it lacks a cell wall, making its fossilization complicated. Like other of its relatives it has an elongated flagellum and a collection of smaller ones next to it to move around. It hails from the Emsian stage of the early Devonian.
Name: Promissocauda rheia
Size: 25 micrometers
Location: Rheic Ocean
Time period: 415 mya
Promissocauda rheia is a slightly larger protoloukidan. It exists in more shallower waters of the Rheic ocean, near the land strip that was about to form the Laurussian-Gondwanan isthmus, dating to the middle Lochkovian stage of the early Devonian. This bacteriophage is characterized by a very long flagellum, which can range from 2 to 4 times longer than the main cell body.
ECOSYSTEMS
NO IMAGE
Name: Ucayali Formation
Creator: IC1101
Time period: 385 mya
Location: Peru
Some Cambrian fauna still persists into the Devonian, despite the increased competition from jawed fish pushing many over the brink. Despite this, the ones who remain still thrive even in the presence of fierce predators. The shallow waters of Peru, in particular, are a hotspot for the old and the new to interact.
Name: Aptarachne lecythiocercus
Size: 5 millimeters long
Clade: Chelicerata, Euchelicerata, Prosomapoda, Planaterga, Dekatriata, Sclerophorata, Arachnida, stem-Palpigradi
The enigmatic palpigrades of today weren't always so strange, in fact their ancestors looked downright generic. Aptarachne somewhat resembled a "generic arachnid", with a round segmented opisthosoma, eight mid-length legs and two smaller pedipalps, and six eyes. Where it differed from this generic bodyplan was the small bottlebrush-like flagellum sticking out of its back, alongside a slightly more elongated opisthosoma. The pedipalps bore two large claws at their ends, eerily similar to a miniature version of a scorpion's claws. Meanwhile their legs were lengthened, particularly the first ones, which gave it an eerie resemblance to the Carboniferous Plesiosiro. The eyes too were shrunken, being no more than black pinpoints. This suggests Aptarachne was likely a nocturnal or subterranean predator, feeling for its prey and leaping upon them before shredding them with its pedipalps and clawed chelicerae.
Name: Paracaris scarabostoma
Size: 15 centimeters long
Clade: Arthropoda, Dinocaridida, Deuteropoda, Euarthropoda, Arachnomorpha, Chelicerata, Habeliida, Habeliidae
The intricate mouthparts of the habeliids already granted them success in the Silurian through the mighty Deinocaris, but in the quiet shallows of Peru a new form has been developing. This one eerily resembles a new dynasty of land dwelling mandible-wearing organisms. Yes, this is a chelicerate with mandibles. In fact, its head resembles that of a shrimp, one of the most “generic” mandibulates of all. The exopods of its two front appendage pairs have lengthened into antennae, while their gnathobases have become enlarged for processing food. As it isn’t exactly a large predator which needs to crush hard shells, its endopods have also become antenna-like, although smaller and broader than the exopods. Paracaris also shows an unusual level of tagmatisation, with the next three limbs being used for walking, like in the related mollisoniids, and the head therefore was lengthened, meanwhile all but the first three opisthosomal endopods are reduced with the exopods, now used for swimming and breathing. Altogether this results in an oddly hexapod-like body arrangement with a mandibulate head, a leg-bearing thorax and a long abdomen. It’s unclear whether they’ll give rise to a new great clade of arthropods, but their odds aren’t looking good with the pre-existing mandibulates encroaching on their potential.
Name: Ankistrocaris marisimia
Size: 3 centimeters long
Clade: Arthropoda, Dinocaridida, Deuteropoda, Euarthropoda, Antennulata, Fuxianhuiida
While an abyssal sister clade of the fuxianhuiids, including the already known Bathycaridipodia, went extinct back in the Silurian, Fuxianhuiida itself is still surviving. A few still remain in their original niche of benthic detritivores, but many have changed. One of the most specialised is this one. Its exopods are somewhat reduced, meaning it cannot swim very well. It has long, moth-like antennae which are used as filtering appendages to catch plankton. Its head shield extends forwards to give it a peytoiid-like visage, with paired indents aligning with the position of its antennae. Above all, its tail is elongated and lined with serrated edges, alongside having two hook-like appendages at its end. All this combined leads to an eerily seahorse-like ecology; a slow benthic creature which mostly hangs onto algae or reef-builders to catch plankton. It also bears two brightly coloured and lobed extensions of its head shield likely used to attract mates. These seem to have been jointed at their base, suggesting they may also have worked as swimming aids if needed.
Name: Thaumaptera prosdokimos
Size: 3 centimeters long
Clade: Mandibulata, Pancrustacea, Allotriocarida, Hexapoda, Cercophora, Insecta, Dicondylia, Paranotalia
The greatest find of Ucayali was one which had been long awaited: a basal pterygote relative. While this position was already held by the giant Carbotriplura, the new fossil was even closer to pterygotes. Its body did resemble this Carboniferous relative, with small abdominal leglets, relatively large pleurae, large eyes and long legs, but it also bore some similarities to more derived pterygotes such as only two cerci on its back segment, a thinner abdomen and mandibles evolved for chewing. But neither of those were particularly shocking, as these sorts of transitional features were expected for a stem-pterygote. What was shocking, however, was its thorax, where six large plates roughly twice the thorax's width were preserved, which seemed for all the world like proto-wings. Analysis only confirm this, as they line up with theories of wing evolution, and the posterior four were jointed with muscles at their base and even had venation resembling those of palaeodictyopterans. In short, it is the holy grail of insect palaeontology. In life Thaumaptera was likely an arboreal animal (well, as arboreal as it could be in a world where trees had just evolved) feeding on leaves, spores and detritus. Its proto-wings also allowed it to glide from tree to tree if resources were depleted or if it was chased by a predator.
Name: Lambanocheira archaianax
Size: 1.3 meters long
Clade: Lobopodia, Tactopoda, Arthropoda, Aysheaiidae
The reign of the primitive lobopodians was once fruitful, producing such terrors as Omnidens all the way back in the Cambrian. And while this reign may be approaching its end, they still have a few tricks before the finale, for this is one of their last great predators. The radiodonts have declined, the opabiniids are all but extinct, and all others are long gone (perhaps not, though, as you never know what didn't preserve). In their place, the aysheaiids produced nothing short of a behemoth. This lengthy creature bears two stout appendages on its face, each triangular and lined with razor-sharp spines at their margins, giving them the appearance of some strange amphibian's face turned on its side. Its mouth is surrounded by inwards-facing plates, with gaps at the top and bottom giving it rudimentary jaws. While it may be eyeless, it bears several long, whisker-like spines around its mouth, giving it an excellent sense of touch alongside being able to detect motion nearby. Its legs too have changed from those of the ancient Aysheaia, their claws being angled outwards on projections of the lobopod like toes. The higher-up "claws" have become armour plating for, while it may be a venerable predator, even it has enemies. Its papillae have also grown into cone-shaped thorns, giving it as much defense as offense. Due to its armor and spines, it likely laid in wait on the seabed, lunging at any fish or arthropod which crossed its path before swallowing them whole.
Name: Lepadobelos pterostoma
Size: 1 centimeter long
Clade: Gnathifera, Cucullophora, stem-Chaetognatha
One of the most bizarre Ucayali fossils known is this one. While it looks quite like a generic barrel-shaped blob attached to some algae or rock, with what would appear to be a translucent body, a mouth hole at the top, small fringes along its sides and a disc-like holdfast at the bottom, its internal anatomy is particularly odd. For starters, it was a filter-feeder, with several pairs of large bristly spines serving to trap plankton. The small fringes on its sides also seem to be vestigial fins, with the tail fin being its holdfast. And the strangest thing about it was that it had a small unknown organ in its chest, with its purpose being unknown but speculated to be a heart. Upon closer inspection, this can be identified as a ventral ganglion, which alongside with a retractable pocket around the spines would only make sense if this feathery blob was somehow a chaetognath. Further examination of isolated spines sharing the shape of Lepadobelos only seemed to confirm this, as their microstructure lined up with those of already known chaetognaths. The discovery of Capinatator in the Burgess Shale luckily solved a few mysteries, as the many fine spines and possibly reduced fins lined up between both species. Exactly what caused the macropredatory chaetognaths to give up the hunt and settle down on the seabed is unclear, although competition from arthropods likely drove the Capinatator-like ancestors to become filter-feeders and eventually more sedentary.
EXTINCTIONS
Pectocaridida (†411 mya): - Pectocarididans were enigmatic basal arthropods, likely located at the very base of the stem-mandibulate lineage, perhaps being more basal than the artiopods (trilobites and kin). These are only known from Cambrian fossils, in the form of bivalved nektonic predators such as Occacaris and Forfexicaris. However, these strange arthropods actually survived past the Cambrian, however, undetected as their last refuge was in the abyssal regions. They narrowly survived the end Ordovician extinction, with only a very small amount of species enduring in very secluded regions of the Silurian. Finally, these raptorial deep sea predators became extinct in the late Lochkovian stage of the early Devonian, some 411 million years ago, perhaps due to competition with other more diverse arthropods groups, such as thylacocephalans. (YellowPanda2001)
Xenusiidae (†408 mya): Another late surviving lineage hailing from the Cambrian were the xenusiids. Xenusiids were peculiar lobopods known from the fossil record of the early Cambrian, but they do seem to have survived in restricted marine regions up until the early Devonian. The last species eventually went extinct during the Pragian stage. (YellowPanda2001)
Nektaspida (†385 mya): - Nektaspidans were a wide-spanning lineage of primitive artiopods (related to trilobites) with non-mineralised exoskeletons. They were very abundant in the Cambrian but a few species survived into the fossil record of the Ordovician and Silurian periods. The group actually survived into the Devonian, undetected by the fossil record, as, by that time, they were rarer and their exoskeleton made preservation harder compared to their trilobite brethren. The last genus was Naraoia (already known from fossils from the Cambrian to the Silurian) surviving in secluded regions up until their ultimate extinction in the Givetian stage of the middle Devonian, 385 million years ago. (YellowPanda2001)
Smilidontidae (†372 mya): - In the seas of southern Euramerica, among sparse reefs, lived a small family of arthrodires - Smilidontidae, or "chisel teeth". Their name mostly derives from their adaptations for feeding on hard shellled and/or slow moving prey, like brachiopods or mollusks. Unfortunately, they went extinct during the Kellwasser Event, or Late Devonian extinction event, alongside many groups of "placoderms". (TheTiger773)
Vetulicolia (†370 mya): - Surprisingly, vetulicolians, a group whose fossil record lasts no later than the Cambrian period, survived long after its record, almost 145 million years later. It is unknown exactly how they survived through the Ordovician and Silurian periods undetected, but it is believed that they actually appropriated from the provinciality of specific locations, around the asian terranes, and their high relictual endemism prevented them from expanding elsewhere. They eventually extinct a couple of million years after the Kellwesser event, 370 million years ago, in the early Famennian, narrowly surviving total reef ecosystem collapse, and eventually disappearing with the diversification of new species after the extinction. (YellowPanda2001)
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