ORDOVICIAN

SPECIES

Name: Phytokeeda incognita

Creator: YellowPanda2001

Size: 3 millimeters long

Location: Shallow seas of Madagascar, Maldives and India

Time period: 484 mya

Clade: Nephrozoa, Schizocoelomata, Ikariidae, Mongolohelminthiinae

The early Ordovician seas of western Gondwana were a haven for a myriad of fauna that was just diversifying with the onset of the Great Ordovician Biodiversification Event. The chaotic circumstances surrounding the biotic overhauls that succeeded the end of the Cambrian signified that this point in history had an array of traditional Ordovician fauna often coexisting with holdovers from earlier eras. One of those were the ikariids, where the shallow seas that surrounded Mongolia and western Gondwana served as a last refuge from this otherwise Ediacaran lineage.

Phytokeeda incognita hails from the early Tremadocian stage, and it belongs to the subfamily Mongolohelminthiinae, a subfamily of ikariids characterized for their presence in the Ordovician Mongol-Okhotsk sea and vicinities, including what corresponds to modern Mongolia, north and south China, Tibet, southeast Asia, Australia, India, Madagascar, eastern Africa and Arabia. Ikariids were too small and minute to be preserved in the most pristine conditions, and they were not very eccologically relevant, which allowed them to evade preservation in the Cambrian and Ordovician periods. The action of burrowing organisms in post-Ediacaran ecosystems made preservation of such small soft-bodied organisms harder, and the provincialism of this lineage certainly contributed to this.

Phytokeeda is special among Ordovician ikariids, for its green coloration. Not quite is the green itself that is outstanding, but the reason why it has green. This stem-protostome feeds on algae, and it manages to steal the chloroplasts of its meal and incorporate it into its cells. This is a tactic that resembles that of some sea slugs of the Holocene. Predating them by nearly half a billion years, the ikariids show that they have been innovating over their early history, albeit secretly. Phytokeeda is an often common inhabitant of very shallow coastal waters of what is now India, Madagascar and the Maldives, where the algae they feed on are abundant. Not infrequently, these small invertebrates may find themselves stranded and die on land as the tides retreat, though some manage to survive by holding onto moist surfaces, permitting them to survive until the tide returns water to their location.

Name: Mongolohelminthes vividus

Creator: YellowPanda2001

Size: 1 centimeter long

Location: Shallow seas of Mongolia

Time period: 481 mya

Clade: Nephrozoa, Schizocoelomata, Ikariidae

The Tremadocian stage, of the early Ordovician, was a period of intense faunal revolutions, caused by the aftermath of the end of the Cambrian. This signified that many ancient holdovers of earlier eras were struggling to fit in an ever changing world, where an intense array of new incredible creatures were evolving, with the onset of the Great Ordovician Biodiversification Event (GOBE). In the reefs of the Mongol-Okhotsk ocean, interspersed by an insular archipelago that would one day correspond to the central asian terranes of Mongolia, a unique undocumented diversity resided, and one curious inhabitant existed: Mongolohelminthes vividus.

This small organism moved through the sediment, munching on organic detritus. This worm had two rows of fleshy protuberances on its back that gave it a distinctive appearance, and allowed it to camouflage in the reef surfaces, mimicking algae or cnidarians. This slug-like creature does not, in fact, however, have much to do with slugs or with most animals that it coexists with, and it instead is an holdover from a much more ancient lineage not seen since the Ediacaran. It is a stem-protostome, and its closest known relative is Ikaria wariootia, an enigmatic australian bilaterian from the Ediacaran. This lineage must have survived through the entire Cambrian period, likely surviving fossil preservation by simply being far too small and lacking any hardened structure for fossilization. Ikariids don't seem to have been very relevant in their ecosystems since, but Mongolohelminthes proves that they have been diversifying in hiding, for nearly 75 million years. Curiously, this species is among the largest ikariids, and leaves out distinctive trace fossils. The absence of similar trace fossils in other localities of this time implies ikariids like these were not found elsewhere in the globe, meaning the provincialism of the Mongol-Okhotsk proved a refuge for this ancient ghost lineage.

Name: Onusnostus moltus

Creator: TheSirenLord

Size: 5.08 centimeters long

Location: Sweden

Time period: 467.3 - 458.4 mya

Clade: Trilobita, Agnostida, Agnostina, Agnostoidea, Ammagnostidae

It has been argued that trilobites explored every possible niche, except for parasitism, in the Paleozoic oceans. However, this may not be true, and a conclusion based purely on preservational bias, as, indeed, parasites are poorly well preserved in fossil history, especially those with mostly just soft tissue. The Agnostida are a group that is already blind and of a mysterious eccological background, and one branch of this group experiemented with parasitism. This creature, nicknamed "the great tricklobite", was the largest member of a genus with many species, one for each of the many species from the cephalopod lineage that had diversified during the period. This specific species lived as a parasite on the body of the apex predator of its time and place, Endoceras, with the amount of Onusnostus moltus being likely harmless to the giant mollusk in lower numbers, only suffering from the onset of the arthropods inevitable haematophagy or consumption of overly dead tissue, no doubt annoying its host with tickling movements in high infestation levels. Sadly, due to a poorly mineralized body, and the fact that soft body tissue preservation is hardly existent in the majority of now extinct shelled members of the cephalopod lineage, means that this great dynasty of trilobites has been entirely forgotten. When the genus first evolved and went extinct is impossible to determine, though it may be probable that this species lasted as long as its host temporarily did in the region, during that time, and the genus as a whole may have lasted as long as shelled members of the cephalopod lineage existed in the Ordovician.

Name: Rufognathus ranupiscis

Creator: TheTiger773

Size: 6 centimeters long

Location: Shallow seas of Southern Laurentia

Time period: 450 mya

Clade: Chordata, Olfactores, Vertebrata, Thelodontomorphi

Rufognathus ranupiscis is a species of jawless fish belonging to the sister lineage of the Thelodonti, and by extension, its a member of the paraphyletic group known as "ostracoderms", which are actually a gradient towards the jawed vertebrates that would dominate the Earth in later periods. Rufognathus, particularly, is a very basal thelodontomorph, sister to true thelodonts, forming a ghost lineage dating back since at least the Sandbian or Darriwilian. Due to its lack of functional jaws, they feed on plankton suspended in the water, so this filter feeding fish is actually a rather active swimmer, with an incredibly flexible tadpole-like body that allows it to make fast turning moves to avoid predators in the water column. Rufognathus was a reef specialist, covered in colorful scales which helped them to blend among early corals and crinoids.

Despite the moderate success of this basal tadpole-like thelodontomorph, it went extinct during the Hirnantian glaciation, which was underway during this time, causing climatic upheavals at a global scale. The shallow ocean regions were the most affected, causing massive extinctions and killing off totally unique endemic creatures found nowhere else in the globe.

ECOSYSTEMS 

Name: Wimal Formation

Creator: AlDodo

Time period: 470-467 mya

Location: Laurentia (North America), USA’s western coasts, at the boundaries between Oregon and Washington

One novel Ordovician formation, is one notably interesting for its placement and age within the range of the period as it occured before the sharp changes that define the second half of the period, giving a glimpse to what life was before the start of the cooling climate.

Spanning a very large, but scattered area, in the boundaries between the states of Oregon and Washington, USA, in North America, with an almost, near equal, 50/50 distribution on the territories of both states, is the Wimal Formation (named as such in reference to the Upper Chinook name given to the Columbia River which is also located there). Its a formation which, while short in terms of lifespan, with dating studies suggesting to have existed for around nearly 3 millions years, between 470 to 467 mya (spanning virtually the entire Dapingian stage, though it could have been older by some additional million years into the late Floian stage, around the end on the early Ordovician), it is nonetheless surprisingly very rich in faunal and floral life and biodiversity, and interesting enough to support a cast of organisms typical of the early Ordovician period and from southern regions.

The Wimal Formation is a decently warm, shallow and marine ecosystem, which seems to benefit and take advantage of the still current overall climate of the Early Ordovician which was typical of the period and remaining much of the same, during the Dapingian. The Early Ordovician’s climate as a whole was transitioning towards an in-between the hothouse conditions of the Cambrian and the icehouse conditions of the second half of the Ordovician, reaching moments of less warmth as in the late Cambrian but not as cold as in much of the later middle or late Ordovician. It could be suggested that this was in part the result of a decrease in the anoxic conditions of the Cambrian, and the subsequent increase in euxinic conditions (or an increase in hydrogen sulfide concentrations) in some of the early stages of the Ordovician. Such a context, suggested to be the initiator of the GOBE, also benefited greatly the organisms in the first moments after the end of the Early Ordovician. As a result, the biota found here is very similar to the more famous early Ordovician Fezouata Formation from Morocco, in the Maghreb, North Africa.

The fauna assemblage found at the Wimal Formation is found very deep underground, in the Columbia River, where the streams erode through the land, with the lithogy seemingly being a mix between limestone and dolomites. The fauna and other organisms of the formation comprised mostly of invertebrates, such as demosponges, mitrates, "lepadomorph" barnacles, brachiopods, such as hyoliths, soft-bodied annelid worms, palaeoscolecid worms and machaeridians, while panarthropods were represented by many types of lobopodians, such as radiodonts (mostly filter-feeding genera akin to Aegirocassis), phyllocarid-like crustaceans, marrellomorphs, nektaspidans, ostracods, and cheloniellidans in decent number and diversity.

Graptolites, trilobites, echinoderms, nautiloid-like members of the cephalopod lineage (from the orders Ellesmerocerida, Endocerida, Dissidocerida, Discosorida and Orthocerida, among a plentiful of other orders from or outside their own respective subclasses that each of these fit in) and conodonts are particulary abundant and, no doubt, important clades in the food chain and ecosystem of this biota. While few early primitive eurypterids, also known as "sea scorpions", are also recorded, most chelicerates present in the formation are their, lesser known and more basal cousins, the chasmataspidids, which fill what would become one day their guilds before eurypterids become much more numerous. Additionally, some members of the paraphyletic synziphosurinan group are present as well. There is what seem to be some potential xiphosurans (the horseshoe crab group) but known and current fossil material isn’t conclusive about the true nature of these animals, which, as current knowledge goes, only undoubtedly appear in the fossil record by the Silurian, and while a ghost lineage extending to the Ordovician is possible, for now, it is conjecture.

Like in the Cambrian, the radiodonts are among the largest megafauna, with members reaching nearly 2 meters on average, however, the dominant and most numerous large animals, at this point, are the various and much larger shelled members of the cephalopod lineage.

What appear to be some possible skaniids have been found, as well as potential late surviving canadaspidids, megacheiran leanchoiliids and halkieriids, both last three being only undoubtedly known Cambrian groups in our timeline as our current fossil records tell. If true, would extensively expand the lifespan of these groups until around the Middle Ordovician, as likely derived and specialized forms, and perhaps becoming extinct for good around this time, by the end of the Dapingian, almost 467 mya, with the start of the changing climate mentioned above.

Compared to the earlier, southern Fezouata Formation, the Wimal Formation is more northern, nearer the equator, under warmer temperatures, and one observes that most of the faunal cast of the Early Ordovician (comprising the Tremadocian and Floian stages) have lasted decently for a longer time and without major changes due to the overall and relatively stable global climate which occured for most of the period.

What is known for sure, is that the Wimal Formation represents a last shot for the typical life associated with the early Ordovician period, and its last hours of abundance and success, before the advent of the changing climate and progressive cooling, which ultimatly will define the remaining span of the period and the decline of many orders.

Name: Angustidontimimus relictum

Size: 2.5 meters long (average)

Clade: Arthropoda, Dinocaridida, Radiodonta, Anomalocarida, Hurdiidae, Aegirocassisinae

Angustidontimimus ("Angustidontus mimic") is a large species of radiodont found in the Wimal Formation, and among the larger animals found there, although it is surpassed by a great margin in size and lenght by the largest orthocones found there henceforth.

An aegirocassisine hurdiid, this animal is part to the same family as the earlier Hurdia and Peytoia, from the Cambrian, but also Cambroraster and Arthropodocetus, and, as a member of the subfamily Aegirocassisinae, its a suspension filter-feeder which feeds by eating plankton, such as zooplankton and other microscopic organisms present in abundance in the water column, and filling a similar niche to our timeline's modern baleen whales.

It is a large, placid and non-dangerous animal, moving itself by using several ventral and dorsal pairs of flaps running along its body, with a total number of 10 pairs for both the ventral and dorsal side. And while a typically slow animal when swimming normally and feeding, its able to swim at a faster pace for short periods of time when threatened by another animal. When adults, this species is safe from almost all possible predators, except likely for some large orthocones, and reaching sizes up to 2.5 meters long, even longer than Aegirocassis, it is the largest aegirocassisine, hurdiid and radiodont known to have ever existed.

Name: Velitesakontius geronimos

Size: 20-30 centimeters long (average)

Clade: Arthropoda, Dinocaridida, Deuteropoda, Euarthropoda, Chelicerata, Euchelicerata, Prosomapoda, Planaterga, Dekatriata, Chasmataspidida, Diploaspididae

Velitesakontius is a marine, free-swimming chelicerate arthropod belonging to the sea scorpion-like chasmataspididans, and found in a relatively relevant presence in the Wimal Formation. Its generic name is derived from the velites (ancient roman citizen-soldiers) and the ancient greek word ακόντια (akóntia, meaning "javelins"). While it's specific name, geronimos, honors the famous amerindian rebel, military leader and medicine man Gerónimo of the Ndendahe Apache people.

Its ecology and behavior are believed to have been pretty much the same as the general lifestyle of the group. Being small, likely ambush and generalist predators of small, likely soft-bodied prey, and using its paddle-like appendages to swim only when needed (most often to escape predators or go from one far location to another faster). A very small animal, at maximum around the same size than most of the larger trilobites, Velitesakontius is a mesopredator, which was nevertheless hunted by larger predators, such as Protoendoceras. While early eurypterids can maybe also sometimes hunt on the adults, specimens of this species, from time to time, hunt and feed on their own young and eggs, as cannibalism is verified in this species from a specimen showing larvae inside its body.

Name: Paraogyginus oregonis

Size: 50-60 centimeters long (average)

Clade: Arthropoda, Dinocaridida, Deuteropoda, Euarthropoda, Antennulata, Artiopoda, Trilobitomorpha, Trilobita, Asaphida, Asaphoidea, Asaphidae, Ogygiinae, Ogygiini

Paraogyginus ("next to Ogyginus") is a decently sized species of trilobite and a very common member of the group within the Wimal Formation, and among the most common bottom dwelling arthropods of the location. 

It is a relative of the genus Ogyginus, and like it, it belongs to the Asaphidae family, from the order Asaphida. It is a typical member of its family. It has the popular shape and appearance of what people think first about a trilobite, being wide, round, and short in lenght.

This arthropod is a generalist, opportunistic bottom-dwelling animal, scavenging and feeding on all possible organic matter in decomposition on the sea bed, integrating both animal and plant life into its diet. It reproduces near the coast, laying eggs at a certain point in the year, then returns to the more shallow parts of the formation. It is surprisingly a quite relevant component of the food chain, falling prey to almost all other major large predators known from the formation, in spite of its armor, including Protoendoceras, larger members of the cephalopod lineage, early eurypterid "sea scorpions" and some species of conodonts.

Name: Protoendoceras vasallus

Size: 1.5 meters long (average)

Clade: Endoceratoidea, Endocerida, Endoceratidae

Protoendoceras ("before inner horn") is a shelled member of the cephalopod lineage, common within the Wimal Formation and among the most common predators found in this biota. A relative of the more famous Endoceras, which is known from the second half of the Ordovician.

This animal, for its time, was a pretty typical species for a member of the cephalopod lineage, with a decent sized, long, thin, rounded and non-coiled mollusk shell. This member of the cephalopod lineage is an ambush benthic predator, preying on a variety of trilobites, mollusks, brachiopods and other small bottom-dwelling soft or hard-shelled organisms. It patrolls the sea bottom, moving or resting in a vertical or diagonal position, with the tip of the shell directed to the sky, thanks to it buoyant shell ideal for that, when in slow locomotion. And while capable of decent swimming, it isn’t as fast and agile as future coleoids and ammonites. Young are much more actively mobile than fully-grown adults.

Physiologically speaking, Protoendoceras is a rather simple species for an Ordovician member of the cephalopod lineage, with only its size, when adults, being the sole main difference compared with the other contemporary relatives, otherwise displaying plesiomorphic traits, with a configuration of 10 simple arms, simple eyes with lens, and a "hat" on its head, the latter being rounded and shaped like that of its close relative, Endoceras.

Name: Plumulites wimalis

Size: 15 centimeters long (average)

Clade: Annelida, Machaeridia, Plumulitidae, Plumulites

Plumulites is a marine annelid machaeridian worm. A group of true, segmented worms that have armored plates, from the plumulitid family (Plumulitidae). This is among the decently common non-arthropod invertebrates present in the Wimal Formation.

Plumulites isn’t a novel taxon, but one already found with decent fossil material, with the species located at the Wimal Formation not being known from fossils. This species is P. wimalis.

Like the other species of the genus, P. wimalis is mostly known from isolated sclerites, with complete specimens showing that this animal is surrounded by pairs of outer and interior shell plates and some of anterior outer and interior shell plates being different in shape. And like other plumulitids, this animal was somewhat flattened from above and looks much like the coat of mail armour of chitons.

Like other machaeridians, this worm is often found in association with stylophoran echinoderms - the cornutes and mitrates. This shows that they have a similar ecology to these, feeding on organic detritus, and sometimes the faeces of the accompanying stylophorans that they coexist with. As for its locomotion, P. wimalis moves across the surface of the sea floor using parapodia.

Name: Mikrapanderodus mesorapax

Size: 40 - 50 centimeters long (average)

Clade: Agnatha, Vertebrata, Conodonta, Conodonti, Protopanderodontida

Mikrapanderodus ("young Panderodus") is a member of the jawless vertebrates group of the conodonts, and among the few and largely dominant chordates in the Wimal Formation, an otherwise invertebrate-dominated world, like everwhere in this point in time in the Ordovician. Yet, it is a surprisingly common species of early fish, being a basal protopanderodontidan, retaining the basal anguilliform trait that the more derived flattened representatives of the group don't have.

Having a pretty typical appearance for a member of its group, this animal is known, due to its dentition, to be a mesopredator and likely passing most of its activities during the night. Using its large eyes to see through the dark and hunting small soft-bodied prey, with its teeth having a role to lock prey into place, it uses its small size and slender body to hide and evade larger predators within the aquatic vegetation and rock structures. Several deposits of this animals seem to indicate that this fish frequently remained in small groups, maybe representing amalgams of several specimens during their reproduction.

Name: Upper Nile Shale

Creator: YellowPanda2001

Time period: 465 mya

Location: Upper Nile, South Sudan

Most Ordovician fossil life hails from rich marine environments, that give us an extraordinary glimpse at the wonderful life that lived in the oceans of the time. However, a less documented environment was the inland areas. Although the land was mostly barren of life, freshwater courses ran through the mainland. In what was then upland regions of our timeline's South Sudan, lied the Upper Nile Shale, a rich community of freshwater fauna from the middle Ordovician period. Hailing from the early Darriwilian, 465 million years ago, shortly after the Ordovician meteor event (an event that was responsible for the presence of an equatorial ring circling the Earth), this freshwater environment preserved some unexpected inhabitants, including relics from more ancient times. This ecosystem was characterized for being cold and filled with algal blooms that contributed to an anoxic environment. This ecosystem predates the heavy glaciation episodes that would devastate this region of the globe, and probably put an end to this magnificent biota.

Name: Angelaspis largus

Size: 20 centimeters long

Clade: Arandaspidiformes, Arandaspididae

Freshwater inland areas of Gondwana appeared to have been teeming with a variety of vertebrates. Although fish were moderately abundant in proper marine contexts, the ostracoderm group (a paraphyletic grade of jawless armored fish that were distantly related to gnathostomes), was surprisingly pretty present in the Ordovician freshwater regions, and in fact, their surges of diversification throughout the period probably happened there, before an even bigger radiation event occured after the end of the period. Angelaspis largus might be the most impressive species of fish of the Upper Nile Shale. It is an arandaspidid, likely related to the more well known Sacabambaspis. It is characterized by a pair of very large fins on the tail for swimming, and perhaps also for display. It is, however, quite possible that these huge fins could have served to deterr potential predators, being able to escape in case they happen to get a good grip on their fins. The head region of this species is also relatively large, and flat at the tip, suggesting this fish was a slow swimmer, filter feeding near the benthos.

Name: Deinocyclops horridus

Size: 20 centimeters long

Clade: Deuteropoda, Kylinxiidae, Deinocylopinae

The Upper Nile most iconic and unexpected residents are actually strange relictual remnants of more primitive Cambrian biotas. The Ordovician has a well established global fauna of animals that have persisted throughout the rest of the Paleozoic, leaving few grounds for the survival of relictual survivors from less lucky lineages. For instance, basal deuteropods are mostly unknown from the Ordovician, unless they belong to the euarthropod group. But a few lineages of Cambrian basal deuteropods seem to have survived here. Perhaps the strangest is Deinocyclops horridus, an apex predator of the region. This shrimp-like hunter only has one large eye, and two very large raptorial appendages. This nektobenthic killer reminds us of the incredible raptorial radiodonts of the Cambrian, but this is in fact a relative of the lesser known Cambrian Kylinxia.

Name: Spathipleura ultima

Size: 3 centimeters long

Clade: Isoxyida, Isoxyidae

Isoxyidans were a moderately successful group of basal deuteropods from the Cambrian period, ruling as nektonic and nektobenthic small hunters across the oceans of the globe, but their fossils disappear before the end of the Cambrian. It is, therefore, quite shocking that a last straggler remains of this group, in the freshwater inland areas of Gondwana, in the middle Ordovician. Spathipleura ultima is a swimming isoxyid with spikes on the top of its carapace and a very long spade-like projection above its head. This tiny swimming arthropod hunts for smaller soft-bodied prey in the water column and in the bottom of algae-filled lakes. It itself can fall prey, however, to the larger and more menacing hunters, such as Deinocyclops.

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