#Plesiosauroidea

[fishenjoyer1]

Fish of the Day

Today's fish of the day is the Freshwater Plesiosaur!

The freshwater plesiosaur was requested by Jasper, thank you Jasper! Plesiosaurus as a marine reptile, well known for their prowess as apex predators, but freshwater plesiosaurs are a relatively new idea. Based on the finding of a couple of fossils in what is now Morocco's Sahra desert river system, specifically an area called the Kem Kem beds. These fossils are scattered, showing us that this is not just the bones of one animal but a group of freshwater plesiosaurs that lived in the area, at least a dozen of them. The finding of many teeth in particular shows that these animals didn't just swim in from the ocean temporarily, but lived in the area long enough to shed teeth. This has led to some theories that the popular cryptid, The Loch Ness Monster, may be a freshwater plesiosaur, although no fossils have been yet found in that area. Although this does not confirm their existence it raises a strong argument for them. However, with limited knowledge about them for the time being, let's go over plesiosaurs in general!

Found and named in the early 1800's the plesiosaur, from order Plesiosauria, is thought to have first appeared in the late Triassic Rhaetian stage, about 203 million years ago. These animals went extinct about 66 million years ago, to the Cretaceous-Paleocene extinction event. How they swam is still up for debate, many favor the theory that they had wide range with each of their fins, and had identical strokes, but other theories are that they may have used only the fore or hind fins for locomotion, or perhaps used them in reciprocal movement. Similar debate exists for how these animal may have dived, although we know they dived for food, as signs of decompression sickness have been found. As apex predators they ate through anything they could get close to, small fish, larger fish, sharks, cetaceans, crustaceans, one another. It is found that although they were certainly near the top of the food chain, some of them were still occasionally prey for large sharks, but mostly they fell to one another, larger plesiosauria hunting smaller. It is thought they evolved to fill the niche left open by the extinction of Ichthyosaurs, which died out in the late Cretaceous, and allowed for diversification to take place in Plesiosauria. Plesiosauria during this era evolved two distinct morphological types: the pliosauromorph build, the Pliosauroidea family, and the plesiosauromorph build, the Plesiosauroidea family.

Pliosauroidea is defined by their large heads and short necks, often compared to the build that crocodiles have.  They are also known for having larger hind flippers than other plesiosaurs and can be found mostly across South America, and along the equator, although some fossils have been found as far north as Norway. The largest genus found so far, the Liopleurodon, is as large as 6 feet 5 inches, or just a little under 2 meters.

Plesiosauroidea was defined by the long skinny neck, which was used to hunt in small holes, and could move fast to snap up small marine animals nearby them. Although Plesiosauroidae is often depicted as a fast moving predator, it is found that they were likely slow swimmers, pushing their way through the water similar to the swimming methods of turtles, staying close to the surface and using their four limbs for mobility, making it easy to snap at nearby animals. Despite the common displays of them in swan-like positions, with the head raising out of the water, this is unrealistic, as they could not raise their heads up to a degree like that, and the weight of the muscles would prevent them from surfacing. The size difference between differing species was huge, as some could be only as large as 3 meters to 20 meters in length. It is currently thought that the freshwater finds belong to Plesiosauridea.

Everyone have a good day!

[corvuserpens]

Plesiopharos moelensis

In between my Masters project, I managed to squeeze this one in the middle. It's summer, so that means my longing for the sea has awoken from its slumber to kick me in the teeth. Plus, it's been a hot minute since I've drawn a plesiosaur! They're such marvelous and strange creatures.

This one is a portuguese form from the early Jurassic (Sinemurian), discovered in São Pedro de Moel, Marinha Grande, in the district of Leiria. The fossils were found by collectors António Silva and Vítor Teixeira in 2017 and later donated to the Museum of Lourinhã, where they were prepared and described.

Plesiopharos was a basal member of Plesiosauroidea and a close relative of Plesiosaurus, discovered by Mary Anning in the famous Jurassic Coast of Dorset, England in the XIX century. Therefore, I tried to make it look as basic as possible, without many special features, except for the color pattern. We only have a limited number of body fossils for this animal, like part of the spine, some ribs and gastralia, pelvic girdle and a few digits, so not much to go on. Still, this was meant to go on a t-shirt, so I still had some creative liberty for myself!

This was made on Clip Studio Paint, Gods know how many hours. More than five, less than ten, it's my estimate.

Find me on Instagram, Cara, Bluesky and Twitter.

[suryp]

It was a calm day.

The water was clear, the waves calm, and the sun shined through them. Mothers dark dorsal absorbed the light, but her pale belly was painted with the shine, even as far down as we were.

"Are you ready to go out today?"

She'd been pressing me. I was two meters long by then, and had yet to see open water.

"Um..."

"There's no need to worry. Predators don't like calm days like this, and we don't need to go far."

"...alright. Lets go."

So we went. Even to the outer reefs, hunters avoided mother. Small fish crowded around the flotsam, some like islands more than twice her length, casting shadows down below. We continued onto the barrens, then the jelly fields, avoided stingers as we went, and eventually made it to the wall.

"..."

"...It's alright sweetie. I'll be right behind you."

"...ok."

We swam slowly, cautiously. I curved my neck in every direction, to see what was out there. Above us, only driftwood. Below... I flipped over to get a better look.

Nothing.

Just shadow. the light slowly fading in the dark water. I turned back. My dappled gray skin wasn't so obvious as mothers black, but I had spots that might give me away.

We rose to breathe, I stayed just below mother, her flippers curved under to cradle me, the hard skin at their edges could cut sharks.

I lifted my head up, out of the water...

Something cut my sides.

In a panic, I thrashed and dove, before quickly finding cover on the underside of the driftwood, clinging to it with fins.

And I looked to the void.

And then I looked for mother.

Blood... her blood. Mothers blood was around me, it was still falling into the water. I could taste it...

...Falling?

Cautiously, I crept to the side, preparing to look up and out of the water...

A great pile of flesh crashed into the waves. The taste was intoxicating, and filled me with fear...

So I swam. Away. I didn't know where. Open water wasn't familiar, and there were no landmarks to tell where home was.

...I'm lucky to be alive.

The people I swim with now are not like me. They do not speak my language, cannot speak it, with only two flippers and no neck, and I can only sing a fraction of their songs over a fraction of the distance...

But they are kind. They have learned my strengths, and support my function in the pod. Together, we are more effective hunters.

But not really a family. I guard their pups with my agility, wrestle large game with my size, and am allowed to eat first with hunts I help with, but I can not sing their songs, and there is nowhere to write or draw in this abyss.

But there are drifters.

The things that took my mother.

And I could not make them pay without my pod.

-

Cast in the same (overall) world as my previous short story (singular paragraph of a story) but with a different main character.

I'm sure at least some of you will be able to figure out whats actually happening here, but if you need help:

The narrator (and their mother) are Plesiosaurs. for a rw species I'd liken them to Tricleidus seeleyi, particularly the illustration by @ddinodan (twitter) on their plesiosauroidea chart, which is also featured on wikipedia.

The pod, who takes the narrator in, are cetaceans most similar to Acrophyseter deinodon, if a bit smaller.

the drifters are... well, it should be pretty obvious. no-one else really uses boats in this setting, since they can't or don't need to.

well. thats a wrap, folks! :3

[slothknight-art]

specevo freshwater plesiosauroidea!

The black-snouted river pseudolphin,which evolved from basal plesiosauroidea,is a plesiosaur live in early Cretaceous in Morocco unique for its freshwater adaptation which convergence with river dolphins.

They have a long snout for catching fish,two large flipper-like fins for movements,and two fins near their short tail which works like tail fin on whales.Their way to move is like a mixture of movement of dolphins and sea turtles.

(their way to move is shown in pic 2)

[ancientmarinereptiles]

Opallionectes andamookaensis

Photo by: Steve, https://www.deviantart.com/lizardman22/art/Opallionectes-andamookaensis-583247675

Name: Opallionectes andamookaensis

Name Meaning: ‬Opal swimmer

First Described: 2006

Described By: Kear

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Plesiosauroidea

Opallionectes was a plesiosaur that lived during the Early Cretaceous of what is now known as Australia. Data suggests that this plesiosaur may have dwelled in very cold waters. Opallionectes may have had blubber as an adaptation for this freezing type of environment. Paleontologists actually found Opallionectes in an opal mine down in South Australia.

Sources:

https://en.wikipedia.org/wiki/Opallionectes

[cryptidchronicles]

Instead of laying eggs like other reptiles, a mother Polycotylus gave birth to a single, large offspring. Here, an artist imagines what that looked like.Stephanie Abramowicz/NHMLA Unlike some better-known long-necked plesiosaurs like Plesiosaurus and Elasmosaurus, Polycotylus had a short neck. This led to it being classified as a pliosaur, a marine reptile within the superfamily Pliosauroidea, closely related to true plesiosaurs (which belong to the superfamily Plesiosauroidea). Polycotylus and other polycotylids superficially resemble pliosaurs like Liopleurodon and Peloneustes because they have short necks, large heads, and other proportions that differ from true plesiosaurs. As phylogenetic analyses became common in the last few decades, the classification of Polycotylus and other plesiosaurs have been revised. In 1997, it and other polycotylids were reassigned as close relatives of long-necked elasmosaurids. In a 2001 study, Polycotylus was classified as a derived cryptocleidoid plesiosaur closely related to Jurassic plesiosaurs like Cryptocleidus. Viviparity, or live birth, may have been the most common form of reproduction in plesiosaurs, as they would have had difficulty laying eggs on land. Their bodies are not adapted to movement on land, and paleontologists have long hypothesized that they must have given birth in water.

[silvokrent]

An excerpt from the zoological text The Hunter’s Encyclopedia of Animals (First Edition).

Chapter VI: Plesioth

The plesioth (Plesichthys coxa) is a species of pelagic wyvern found off intertropic coasts across the globe. At a weight of 4.7 tons and a length averaging 26 meters, it contends for the title of largest marine predator. The plesioth’s physiology is adapted to a life spent transitioning between land and water — it is capable of diving to depths of 450 meters at speeds of 54 km/h (34 mph), and remaining submerged for 40 minutes at a time. The plesioth’s ability to fly was forfeited early in its evolutionary history, replaced by adaptations that allow it to withstand extreme deep-sea pressure and low concentrations of dissolved O2. Its vestigial wings, meanwhile, underwent exaptation and have been jury-rigged into fin-like appendages that assist in swimming. According to one study, the plesioth’s lifespan is approximately 50 years.

The plesioth has few natural predators as a result of its venomous spines. Laterally-visible, horizontal orange stripes advertise the neurotoxin to any potential predators. Every so often, juveniles are susceptible to predation by sympatric predatory megafauna. In addition to its aposematic coloration, the plesioth can ward off predators by forcefully ejecting a fluid from a pair of glandular sacs inside its mouth. This liquid projectile can be accurately sprayed as far as 5 meters (16 feet). The fluid is miscible in water, and therefore exclusively used on land. Both of the aforementioned adaptations are utilized as antipredator mechanisms and have no function in hunting. Rather, the plesioth is an ambush predator that kills its prey through a combination of stunning (tail-slaps, high-velocity breaches) and drowning. Countershading obliterates its outline in the water, with its dark dorsal scales making it inconspicuous to animals looking down on it from above. The bulk of its diet is comprised of fish, and as the plesioth matures it begins to incorporate larger prey species such as pinnipeds, pseudophids, and ornithischians. Because of the plesioth’s moderate fecundity and wide distribution, its conservation status is classified as least concern.

The plesioth has a recurring presence in the cultures of seafaring people. Although it doesn’t actively hunt humans or wyverians, plesioths have been known to follow ships at a distance. They scavenge on bycatch and waste jettisoned from vessels, and occasionally raid nets and fishing lines for an easy meal. As a consequence of conditioning them to associate boats with food, plesioths are the most likely culprits of attacks on shipwreck victims. Their ghostly white, translucent third eyelids, in conjunction with their habit of congregating near sunken ships, may have influenced the myth of plesioths being psychopomps. A number of equatorial communities honor the plesioth through week-long ceremonies and parties. Such festivals are accompanied by the custom of mounting a plesioth’s skull or severed head on an ornately-carved pole, not unlike a Mari Lwyd. Anthropologists speculate that a misunderstanding led to the belief that the mounted head was actually a hammer. Traditional dishes include a ceviche marinated in citrus, and rotten flesh fermented in lactic acid. In medicine, the plesioth’s venom has potential as an anesthetic and a pharmaceutical drug for treating insomnia.

Other names for the plesioth include the plesio, water wyvern, and shark wyvern. The latter is a title it shares with the cephadrome (Selacharena alata) and anorupatisu (Pristocephale glaciesecans).

The plesioth’s name is an example of semantic drift. The word is originally derived from the clade Plesiosauroidea, a group of long-necked marine reptiles. Plesiosaurus is a compound of the Greek words plēsíon “near” and saûros “lizard,” and refers to the group’s resemblance to limbed squamates. Over time, the prefix plesio- was recontextualized to have the meaning “like or similar to a plesiosaur.” Thus, the plesioth was named for its resemblance to plesiosaurs, and was assigned the suffix -ioth to maintain the naming convention already established in the common names of other animals (like the lavasioth and epioth). Ironically, the genus Plesichthys is a portmanteau of plēsíon and ikhthús “fish,” and was named for the plesioth’s near fish-like appearance.

Taxonomy and evolution

Fossil evidence suggests that the plesioth evolved from a unique lineage of diving wyverns 10 million years ago. Unlike other vivernans of that period, the plesioth’s ancestor Marincola marincola [†] was semiaquatic, roosting in small colonies on seaside bluffs. Its streamlined body reduced drag when plunging from flight, allowing it to hit the water at breakneck speeds exceeding 80 km/h (50 mph). Air sacs in the face and chest cushioned the impact, a feature which was later lost in its descendant (along with skeletal pneumaticity). The ancestral plesioth moved underwater via foot propulsion, with the wings used for steering. Today P. coxa primarily swims using a combination of its webbed feet and an undulatory locomotion reminiscent of BCF (body-caudal fin) swimming. A comparison of the foot morphology between the holotype M. marincola and modern gannets supports the diving → swimming transition theory, and proposes a convergence amongst semiaquatic theropods.

While the plesioth shares a common ancestor with flying wyverns, it has a long history of genetic independence from its closest relatives (raths, khezus, and other vivernans). Molecular systemic DNA research places the plesioth in a basal lineage of gymnopteronoid.

Subspecies

There are only 2 extant representatives of the family Marincolidae. Each subspecies is characterized by scale coloration, distribution, circadian rhythms, and preference for hunting techniques.

The oil-backed plesioth, or informally simplified to oil-back (P. c. coxa), is the nominate subspecies. Its range encompasses the subtropic and tropic coastlines of the West Dragon and East Dragon Oceans, and the interior seas of South Elde: Jyuwadore, Shikuse, and Moga. It inhabits seagrass meadows, kelp forests, coral reefs, and coastal alcoves which have a water temperature between 13°C and 29 °C (56°F and 85°F). Although P. c. coxa is active during the day it is primarily a crepuscular predator, and has greater success at hunting during the hours of dusk and dawn. It gets its name from the appearance of its dark blue scales when seen in clear water with low turbidity; the contrast gives it a resemblance to “an oil spill come to life.”

The green plesioth (P. c. viridis), unlike P. c. coxa, dwells in brackish ecosystems, including wetlands, swamps, and estuaries. They typically avoid venturing out into saltwater, although fishermen have reported seeing them as far as a mile from the nearest coast. It’s generally accepted that the presence of green plesioths in mangrove swamps (near Jumbo Village) and river mouths (like those of the Metape Jungle and Flooded Forest) reduces competition with the oil-back. P. c. viridus takes advantage of its green pigmentation by concealing itself amongst hydrophytic plants such as water lettuce and duckweed. Perhaps because of its greater reliance on camouflage, this diurnal subspecies almost never breaches when hunting.

Characteristics

Physical description

As a member of the clade Viverna, the plesioth’s body plan is largely representative of the wyvern archetype: a bipedal stance and horizontal posture with the tail held parallel to the ground. Where the skeletal structure differs is in the wings. While the thumb in other wyverns is short and supports the leading edge of the wing, all of the plesioth’s metacarpals and phalanges are elongated and involved in supporting the membrane. The pleated patagium can be tucked against the plesioth’s torso while swimming, thereby reducing surface area and contributing to its streamline, hydrodynamic shape. The wings range in color from white to cream, with orange spots on the outer edge of the dactylo- and iliopatagium. The backside of the torso and head are deep blue, while the underbelly features white scales. The ventral and dorsal regions are sharply delineated by lateral orange stripes that run from the conical snout to the tail along the frontal/coronal plane. Imbricate, ovate scales flow down the body in a head-to-tail configuration that allows for a smoother flow of water over the body to reduce drag. Their visual and functional similarity to cycloid scales on teleosts is homoplastic. The feet are totipalmate.

The plesioth partly owes its charismatic appearance to its white red-tipped semifins. The semifins are webbed structures supported by cartilaginous spines, attached to an endoskeletal base with associated muscles for movement. Being cartilaginous makes the semifins flexible and allows them to flare or collapse against the body. They are classified according to location on the body: dorsal, supercaudal, subcaudal, cranial, tarsal, and pseudopercular. The semifins’ spines are the site of venom conduction.

When submerged, the palatal valve at the back of the mouth creates a watertight seal which barricades the esophagus and trachea. This enables the plesioth to seize prey underwater without drowning, although it has to return to land in order to eat. When hunting, its cone-shaped, slightly recurved teeth allow it to tear through small and medium-sized fish. The carinae (edges of the teeth) are finely-serrated with denticles on the front and back, suited for biting prey outside of an exclusively piscivorous diet. The dentary and premaxilla/maxilla hold 36 teeth that are more densely-packed toward the front of the jaw, and that decrease in size toward the back of the mouth. During attacks, the nictitating membrane is drawn across the eye to protect it from abrasions.

The loss of tyrosinase function results in a genetic mutation called amelanism. Colloquially known as seabream plesioths (after fish in the genus Pagellus), individuals with this pigmentation abnormality don’t produce melanin and have white in lieu of their typical aegean coloration. Because the mutation only disrupts melanocytes, the chromatophores responsible for their orange and iridescent properties — erythrophores and iridophores — are still expressed. The continued production of light-reflecting and carotenoid pigments is what gives the seabream plesioth is distinctive white and reddish-orange look.

Venom

In total, the plesioth has 31 spines distributed across its body. They form part of the semifin, which occurs either in symmetric pairs, or along the medial region of the body. Although the semifins are superficially reminiscent of the ray-fins found in actinopterygians, they aren’t homologous. Semifins are classified into 6 categories according to body region, with the following spine distribution: 4 cranial, 8 pesudopercular, 7 dorsal, 4 tarsal, 4 subcaudal, and 4 supercaudal. The largest spines measure at 7’ 4” (2.2 meters) and are more than capable of penetrating the skin of the largest marine animals.

The primary structural element of the spines is cartilage, a supple and elastic tissue comprised of a dense network of collagen fibers embedded in a gelatinous ground substance. Its composition gives the spines tensile strength, enabling them to resist changes in weight and pressure while possessing greater flexibility than bone. Because cartilage is an aneural, avascular tissue, spines cannot be regrown if they’re damaged or removed. A protective integumentary sheath obstructs the opening of the spine. During envenomation, the sheath is pushed back as it enters the attacker. This process compresses the venom gland at the base of the spine, and allows the venom to diffuse into the puncture wound by travelling through shallow grooves in the now-exposed spine.

It’s thought that the semifins originally evolved as accessories for swimming, and that venom acquisition was a supplementary feature. The plesioth’s venom glands produce a subgroup of neurotoxins known as hypnotoxins, a soporific venom that depresses the central nervous system and affects the neurotransmitter gamma-aminobutyric acid (GABA) at the GABAA receptor. Its symptoms are much like the effects of anesthesia, and can be divided into the same 4 stages of the Guedel’s classification: induction, excitement, subconsciousness, and overdose. At Stage 1, the victim progresses from analgesia without amnesia to analgesia with amnesia. It’s entirely possible that the lack of pain — coupled with memory impairment — can lead to the victim’s inability to recall the initial sting and recognize that they are in danger. Stage 2, arguably the most dangerous, is when life-threatening conditions occur, such as delirium, arrhythmia, vomiting, respiratory distress, pupillary dilation, and spastic movements. Species that lack gills can quickly become disoriented after envenomation and drown as a consequence of the respiratory system becoming compromised (through pulmonary aspiration, apnea, et cetera). Stage 3 is the cessation of the previous symptoms and the onset of subconsciousness. Branchial predators become incapable of pursuing the plesioth, while air-breathing predators at this stage are all but 100% guaranteed to drown. Stage 4 is incredibly rare, and usually occurs if the spines puncture the victim for a long enough duration, or if multiple spines are involved in envenomation. Overdose results in brainstem or medullary depression, followed by complete respiratory and cardiovascular arrest. Without medical intervention this stage is always fatal.

Additional health risks posed by envenomation include: pieces of the spine breaking off and embedding themselves in the wound, leading to infection; and anaphylactic reactions to the venom.

Water-spitting

Before the plesioth’s phylogeny was properly understood, a common misconception was that P. coxa had gills and was descended from an unknown clade of branchial tetrapods. Its ability to spit a high-pressure jet of water from its mouth was likened to various species of archerfish. Later studies proved that the plesioth is a theropod, which made the archerfish’s mode of liquid projectile an impossibility as it involves contracting the opercula (gill covers). Dissection and field observations led to the discovery of paired sacs at the back of the mouth. Dubbed the paralingual glands, these poorly-understood organs can expel up to a quart (32 ounces) of liquid at once and possess just enough of the chemical for 10 discharges (2.5 gallons’ worth), before the glands have to produce a new supply over the next fortnight. The expulsion release is controlled by muscles behind the jaws. There is insufficient data as to what the liquid is composed of, but preliminary chemical analysis suggests a high presence of hydrogen and oxygen.

Diving adaptations

Even though the plesioth is most frequently observed inhabiting the photic layer (the uppermost layer of the pelagic zone, 0 m — 200 m), it can also be found within the mesopelagic layer (200 m — 450 m). At these depths, pressure can be greater than 40 times that of the surface. A combination of stressful deep-sea conditions such as high pressure and low oxygen can cause mechanical barotrauma. To eliminate the risks of physical damage like decompression sickness and organ rupture, the plesioth’s bones became depneumatized. The loss of postcranial air-sacs in the skeleton makes the plesioth denser and prevents embolisms (from buildups of dissolved N2) by decreasing the total air volume in the body. Similarly, the presence of air-filled pockets in the skeleton would have increased buoyancy, a trait that would have been disadvantageous to a diving animal.

Enhanced anaerobic capacity and hypoxemic tolerance are essential for facilitating long dives. When submerged at certain depths, the heart rate is reduced to as low as 20 — 30 bpm. Bradycardia occurs when the plesioth exceeds its aerobic dive limit (ADL), at which point tissue perfusion and oxygen uptake are decreased in order to preserve respiratory and blood oxygen stores. Non-essential organs are shut down and muscles are isolated from circulation, which together cut down on oxygen depletion and extend dives for as long as 40 minutes. Hemoglobin in plesioths shows high cooperativity with oxygen, a phenomenon whereby the binding of one molecule of oxygen with hemoglobin facilitates the binding of the next oxygen molecule and so on up to binding four oxygen molecules by one hemoglobin. The degree of cooperativity hemoglobin has is expressed by the Hill coefficient, which is estimated to be well above 4 in P. coxa. High cooperativity increases the efficiency of the oxygen delivery to tissues. Without these traits, the plesioth wouldn’t be able to withstand the extreme demands placed on its respiratory and circulatory systems that would otherwise result in unconsciousness.

To compensate for diminished olfaction and the mesopelagic layer’s low visibility, the plesioth has evolved powerful visual acuity. Its emmetropic eyes possess a flattened cornea that makes the cornea’s refractive power in air and the corneal power loss in water negligible. Roughly 10% of the eyes’ refractive power is contributed by the cornea, unlike in humans, which contribute up to 70%. Instead, the lens performs the majority of the focusing. This feature minimizes the optical effect of submergence. Sharp images above and underwater are formed by plesioths changing the shape of the lens through muscle contractions.

Behavior

Intraspecific interactions

Plesioths do not routinely seek out conspecifics outside of the breeding season. When plesioths do encounter others in the water they tend to ignore each other, though they demonstrate a remarkably high tolerance for each other’s presence. Socialization isn’t unheard of, however; plesioths may engage in cooperative hunting behavior if two or more are pursuing the same target. Juveniles and subadults will sometimes swim in small bands of three as an added precaution against predators.

Hunting and diet

The plesioth is a predominantly piscivorous animal, with 60% of its diet featuring a large diversity of fish species that are obligate shoalers. Despite this, they are not fastidious in their food choice and readily vary their prey selection according to availability, as evidenced by the remains of other animals found in their stomachs and fecal matter. Juveniles are restricted to hunting fish and other small vertebrates, and only begin to diversify their diet around the age of three. Mature adults are slightly more opportunistic, having the required size to take on larger non-fish prey items. A 30-kilo (66 lbs) meal can sustain a plesioth for up to 5 to 9 days before it is required to hunt again. Scavenging on carcasses isn’t overly common, nor is venturing inland to hunt. Plesioths only go after terrestrial prey when it’s near the water’s edge and within striking range. There are three generally-accepted hunting tactics employed by plesioths, with a slight skewing of preference between the subspecies: ambush-drowning, breaching, and tail-slapping.

The preferred method of taking down non-aquatic animals involves the plesioth motionlessly dwelling along the waterfront. The blue (P. c. coxa) and green (P. c. viridis) dorsal coloration is cryptic for each subspecies’ respective habitat. Concealment allows the plesioth to remain undetected long enough for it to ambush prey. Its conical, recurved teeth are suited for preventing prey from escaping once it seizes them in its jaws. The blinding speed with which it strikes gives the plesioth enough time to drag its prey into deeper water, where it then holds it beneath the surface until it succumbs to a combination of exhaustion, blood loss, and oxygen deprivation.

Breaching is a tactic reserved for animals such as epioths, ludroths, and seals, and is almost exclusively seen in P. c. coxa. The oil-back slams into prey from the deeper water below, with the momentum often taking it partially or fully clear of the water (achieving a max height of 10 meters). At speeds of 54 km/h, the g-force behind the impact is sufficient enough to fully stun prey.

The final hunting strategy is a tail-slap deployed either overhead or sideways. A kinematic study of plesioths attacking bait balls found that the tail-slap occurred with such force that it caused dissolved gas to diffuse out of the water column, forming small bubbles. Due to acceleration of waterflow around the leading edge of the tail, turbulent pressure drops below the saturated vapor pressure, causing the aforementioned plume of bubbles. The associated shockwave is powerful enough to immobilize as many as 20 fish in one tail-slap, which cuts down on the energy costs of hunting active prey.

The diet of P. c. coxa includes a wide array of aggregating fish such as pin tuna, speartuna, glutton tuna, Moga tuna (Katsuwonus katsuo), knife mackerels, wanchovies, sardines, and blue cutthroats. Oil-backed plesioths may sometimes take medium-sized sharks (most commonly Centrinis armatus). Epioths (Cetuserpens repandus and Pseudophis nitidus), immature ludroths (Harpaga leo), and island narwhals (Monodon mysticus) are hunted in deeper waters. Qurupecos (Cantio sirenius) that fish along the shore and passing aptonoths (Parasaurolophus cristatus) are known to have been attacked as well.

The diet of P. c. viridis contains a variety of freshwater and euryhaline fish such as gajuas (Palustincola ferox), fen catfish (Palustincola gravis), silverfish, red-finned arowanas (Osteoglossum esculentum), and burst arowanas (Osteoglossum authothysia). The green plesioth’s proximity to biodiverse terrestrial ecosystems allows it to feed on animals such as slagtoths, immature ludroths (Harpaga blattea), otters, bullfangos (Ossispina taurus), epioths (Pseudophis esmeraldus), congas (Flovorator altilis), and assorted frog species.

Enemies and competitors

Very few attacks made on the plesioth are successful, and are only perpetrated by a handful of species. The venom glands are active at birth and even juvenile plesioths are capable of delivering a potent sting to would-be attackers. Nevertheless, there have been a few documented cases of immature plesioths being killed and consumed by sharks and adult ludroths. The remains of adult plesioths found in the digestive systems of lagiacrus (Heres jormungandrii), pliosaurs, and large placoderms suggests that these predators are capable of hunting them. A counterargument often made in response is that these remains are not the result of active predation, but rather scavenging on the carcasses of plesioths either adrift in water or washed up on shore.

Resources such as nesting sites are highly competed for. The caves and abandoned cliff dwellings of Moga in particular are sought after by both P. c. coxa and H. leo. As a conflict-avoidant organism, plesioths go to extreme lengths to ward off predators and rivals through complex agonistic signaling such as wing-flapping and stomping. If these threat displays fail, the plesioth may discharge a warning shot with its paralingual glands. Plesioths will only retreat and abandon a nest if it’s unoccupied by eggs or chicks, or if there are a significant number of intruders. The culprits behind nest raids are immature royal ludroths and jaggis (Magnaraptor ebrius) for P. c. coxa, and immature purple ludroths and wroggis (Magnaraptor paluster) for P. c. viridis.

Attacks on hunters

To date, there is still a lack of consensus over whether or not attacks on humans, wyverians, and lynians are motivated by predatory intent. While there is evidence to suggest a correlation — as testified by shipwreck survivors that watched plesioths bite passengers in the water — it could be possible that the plesioths are drawn by the sounds of struggling, and are merely exploiting an otherwise unusual opportunity to feed. Outside of narrow circumstances like capsizes and founderings, plesioths don’t actively engage people. Most hostile encounters appear to be the result of provocation by people, whether intentional or accidental. Divers that were unaware of their surroundings ,or that deliberately approached the animal, either spooked it or provoked it into envenoming them with its flared semifins. Spear-fishers have reported accounts of theft, where an emboldened plesioth (typically a juvenile or subadult) stole fish off the end of the spear tip but didn’t try to attack the person holding the equipment. On average, there are 10 deaths associated with plesioths every year, with 8 being attributed to envenomation and 2 to bites. This number excludes fatalities of hunters under the employment of the Guild, whose careers necessitate engaging these animals for the sole intent of combat.

Immunologists studying the venom of P. coxa have dispelled the myth that injections in successively larger doses can achieve mithridatism.

Reproduction and life cycle

Each spring, male plesioths return to the area where they hatched as chicks to participate in a lek. These yearly aggregations commence the start of the breeding season, in which males vie for mates through courtship displays. As many as 25 to 30 individuals — each guarding a territory a few meters in size — occupy the lek mating arena, which consists of shallow cliffs and the adjacent water. Competition manifests in the form of elaborate diving and breaching rituals, meant to demonstrate fitness and overall health to the observing females. Preferential selection by the female results in the formation of monogamous pair-bonds that only last for the duration of the spring and summer. After copulation, the pair retreats to land where they scrape out a saucer-shaped depression in the ground. If the materials are available, plesioths may line the perimeter of the nest with debris, vegetation, stones, shells, or driftwood. A clutch can contain up to 4 eggs, which are monitored and incubated in shifts by both parents until they hatch around 26 days. The eggs are buff, cream, or brown, marked with streaks or blotches of brown or gray to camouflage them. Plesioths that are unable to secure a nest site beneath an overhang or within a cleft must contend with the heat. On hot days, the brooding parent may dive into the water to wet its body before returning to its eggs, thus regulating the temperature. The nest site is defended by the mate that isn’t preoccupied with tending to the eggs or hatchlings. Intruding conspecifics are usually chased off from individual nest sites, while wandering chicks are tolerated. All of the adults in the colony will collectively repel potential predators.

Hatchlings are altirical, and have minimal motor coordination and thermoregulatory capacity. Over the next 12 weeks they undergo rapid development while under the care of their parents. They are fed a protein-rich diet of fish and are presented with suitably-proportioned stones to swallow. These stones become the young plesioths’ first gastroliths, which serve as ballast. By the twelfth week, the chicks are developed enough to now accompany their parents on hunting expeditions. At the onset of autumn and the end of the breeding season, the mated pair departs, as do the now-independent offspring.

Health

Diseases and parasites

The plesioth is a host for epibionts and ectoparasites across multiple taxonomic divisions. Some organisms — like algae and barnacles — have a minimal impact on the wellbeing of the plesioth, and only inconvenience it by increasing hydrodynamic drag. Other organisms that anchor themselves to the plesioth’s body have measurably more harmful effects. Isopod larvae of the family Gnathiidae have serrated, piercing mouthparts, including a pair of toothed mandibles and maxillules, grooved paragnaths, and strong maxillipeds. They feed on blood and tissue fluids at the site of attachment, and are transmission vectors for protists of the phylum Apicomplexa (haemogregarines) which parasitize red blood cells. Sea lice cause abrasion-like lesions on the skin as a result of physical and enzymatic damage. Feeding on epidermal tissue and blood creates a generalized chronic stress response in the plesioth. Monogenean flatworms use attachment organs called haptors, which are specialized structures in the shape of hooks and clamps that adhere them to the host. Infestations on the skin can cause lethargy, infection, scale loss, and respiratory distress.

To rid itself of hitchhikers, the plesioth solicits help from fish at cleaning stations. In a cleaning symbiosis, cleaner fish gather in conspicuous areas and advertise their services through bright hues and stripes. Convergent patterns/colorations amongst different cleaner species reinforce their recognizability to clients, a phenomenon known as Müllerian mimicry. When the plesioth approaches one of these stations it opens its mouth and flares its semifins to signal that it needs cleaning. Wrasses, tangs, and neon gobies maintain the health of the plesioth by removing dead flesh and parasites from its skin, nostrils, and mouth. The relationship is a mutualistic service in that the cleaners are provided a free meal without the threat of predation from the client, and the client is ridden of ectoparasites.

Outside of these accepted congregation sites plesioths have to rely on other means for treating their parasites. Remoras and pilot fish can usually be found in the company of P. coxa. In the case of the former, they are suctioned onto its body by a modified dorsal fin comprised of slat-like flexible membranes. Both groups of fish associate themselves with plesioths for not only protection from other predators, but for the particulate matter left over from the plesioth’s meals, and its nutrient-rich feces. In exchange for tolerating the presence of both species, the plesioth benefits from the removal of ectoparasite and loose flakes of skin.

Distribution and habitat

Plesioths are a common sight in the waters of the Moga Archipelago. The abandoned ruins that sculpt the cliffs are prime nesting grounds for them. The leeward side of the Deserted Island (the largest isle in the chain) is sheltered from the prevailing wind by the area’s elevation, making the ruins above the alcoves and beaches comfortably dry. The islands’ coral reefs and sunken ships teem with prey capable of supporting large numbers of plesioths. The nearby island of Tanzia is similarly rife with the habitats and resources needed to support them, but strangely, plesioths avoid the waters outside of the harbor. It’s thought that the hydrothermal vents and geothermal activity in the Tainted Sea exceed P. coxa’s temperature threshold. Other well-known plesioth congregation sites include Cheeko Sands and Sunsnug Isle.

A popular rumor that continues to circulate (much to the chagrin of the International Hunters’ Guild) is that there exists a colony of oil-backed plesioths in the Dede Desert. Allegedly cut off from the ocean by an isolated river system, these plesioths are believed to have acclimated to the biological, geological, and meteorological properties of their new environment. To date, no evidence exists of plesioths managing to venture upriver and permanently establish a colony there. More than likely the idea was proposed by travelers that were hallucinating as a result of heat exhaustion and dehydration. It’s possible that what looked like a plesioth lifting its head above the water was actually a piece of debris or a branch, making its origins a case of mistaken identity. Another more credible theory is that a cephadrome was somehow mistaken for a plesioth. Despite assurances from the scientific community that a plesioth couldn’t travel hundreds of miles from the sea and survive in a desert climate, dozens of undeterred hunters and explorers make the dangerous expedition each year in search of proof.

[a-dinosaur-a-day]

Liopleurodon ferox, L. pachydeirus

By Jack Wood on @thewoodparable

PLEASE SUPPORT US ON PATREON. EACH and EVERY DONATION helps to keep this blog running! Any amount, even ONE DOLLAR is APPRECIATED! IF YOU ENJOY THIS CONTENT, please CONSIDER DONATING! 

Name: Liopleurodon ferox, L. pachydeirus

Name Meaning: Smooth-sided Teeth

First Described: 1873

Described By: Sauvage

Classification: Cellular Life, Archaea, Proteoarchaeota, Eukaryota, Unikonta, Opisthokonta, Holozoa, Filozoa, Metazoa, Eumetazoa, Planulozoa, Bilatera, Nephrozoa, Deuterostomia, Chordata, Craniata, Vertebrata, Gnathostomata, Eugnathostomata, Teleostomi, Euteleostomi, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiformes, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Anthracosauria, Batrachosauria, Cotylosauria, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Pantestudines, Eosauropterygia, Pistosauroidea, Pistosauria, Plesiosauria, Pliosauroidea, Pliosauridae

Happy April Fool’s! As per tradition, I am writing an article about a non-dinosaur - specifically, the marine reptile Liopleurodon. Made famous by the landmark documentary series Walking with Dinosaurs, Liopleurodon was not really much like as shown in that series - though an important marine predator, it wasn’t... huge. In fact, it was really just around the same length, at maximum, as the modern orca, so there is that misconception shattered. 

Never forget. By Slate Weasel, in the Public Domain

The reason for this misconception is primarily because the skeleton of pliosaurs like Liopleurodon are not really well known, and in fact it was difficult to estimate the size of Liopleurodon in the first place, though of course, it was a known exaggeration to portray it so large. Since the program was made, research of another pliosaur, Kronosaurus, has shown that the heads of these animals made up about one fifth of their total body length - which shows how weird their heads were, for one, but for two it allowed for the estimation of Liopleurodon’s body size based on its skull. It’s skull was, overall, about 1.51 meters in length, making its body around 6.39 meters long. 

By Nobu Tamura, CC BY 2.5

Liopleurodon is known from near Boulogne-sur-Mer and Caen in France, but other fossils are known from England, Russia, and Germany. It lived about 166 to 160 ish million years ago, in the Callovian to Oxfordian ages of the Middle to Late Jurassic, though of course it may have lived longer than that. A large predatory reptile of the Jurassic seas of Europe, it would have been a powerful swimmer, using its four flippers to accelerate rapidly, ambushing prey in the seas. It may have even been a good smeller, able to locate prey easily, and then rush after it to attack it. 

By Dmitry Bogdanov, CC BY 2.5 - note that the fish in the background is inaccurate 

Liopleurodon was a pliosaur, a group of marine reptiles a part of the bigger group of Plesiosaurs. Though Liopleurodon had a short neck, it’s a common misconception that the difference between Pliosaurs and other Plesiosaurs is that Pliosaurs had short necks - plenty of Pliosaurs didn’t have short necks (though most did, and long heads to boot), and there are Plesiosaurs to the exclusion of Pliosaurs with short necks and long heads same as Pliosaurs. Sill, Liopleurodon was fairly typical for its group, and a common figure in its environment. 

Sources:

https://en.wikipedia.org/wiki/Liopleurodon 

https://en.wikipedia.org/wiki/Plesiosauroidea 

https://en.wikipedia.org/wiki/Plesiosauria 

https://en.wikipedia.org/wiki/Pliosauroidea

[ancientmarinereptiles]

Vinialesaurus caroli

Art by: Christopher Chávez, https://www.deviantart.com/christopher252/art/Vinialesaurus-painting-332570487

Name: Vinialesaurus caroli

Name Meaning: ‬Viñales lizard

First Described: 2002

Described By: Gasparini et al.,

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ ‬Plesiosauroidea, Cryptoclididae

Vinialesaurus was a Late Jurassic plesiosaur that was discovered in the Jagua Formation in Cuba. It shared the seas with Gallardosaurus, a pliosaurid also from the same formation. Check out my previous post of Gallardosaurus. Originally, Vinialesaurus was thought to be just another species of Cryptoclidus, but in 2002, it was reexamined and determined to be pretty different from Cryptoclidus. Anyways, paleontologists found a fairly complete skull, parts of the vertebrae, and jaw of Vinialesaurus.

Sources:

http://www.prehistoric-wildlife.com/species/v/vinialesaurus.html

https://en.wikipedia.org/wiki/Vinialesaurus

[ancientmarinereptiles]

Georgiasaurus penzensis

Art by: Andrey Atuchin, https://www.deviantart.com/olorotitan/art/Georgiasaurus-150470248

Name: Georgiasaurus penzensis

Name Meaning: ‬Georgy’s lizard (In honor of Georgy Otschev)

First Described: 1977

Described By: Otschev

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Plesiosauroidea,‭ ‬Polycotylidae‬

Georgiasaurus was a polycotylid from the Late Cretaceous. It was discovered in Russia and paleontologists unearthed part of its skull, some back vertebrae, and two of its flippers. This plesiosaur was originally going to be called Georgia, but that name was already taken, unfortunately.

Sources:

http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=234698

https://en.wikipedia.org/wiki/Georgiasaurus

[ancientmarinereptiles]

Thililua ‬longicollis‭

Art by: Nobu Tamura, CC BY 2.5

Name: ‭Thililua ‬longicollis‭

Name Meaning: Named directly after Thililua, the ‬aquatic god in Berber mythology‭

First Described: 2003

Described By: Bardet, Suberbiola & Jalil

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria, ‬Plesiosauroidea, Leptocleididae

This Late Cretaceous polycotylid plesiosaur is actually the very first polycotylid found from Africa, thus far. It was discovered in the High Atlas Mountains of Morocco. What was recovered of ‭Thililua consisted of the majority of the skull, mandible, and its vertebrae. Speaking of vertebrae, Thililua had more vertebrae in its neck than other currently known polycotylids, this suggests that Thililua was much more primitive.

Sources:

http://www.prehistoric-wildlife.com/species/t/thililua.html

https://en.wikipedia.org/wiki/Thililua

[ancientmarinereptiles]

Polycotylus latipinnis, P. sopozkoi

Art by: S. Abramowicz, Dinosaur Institute, NHM

Name: Polycotylus latipinnis, P. sopozkoi

Name Meaning: ‬Very cupped vertebra

First Described: 1869

Described By: Cope

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Plesiosauroidea,‭ ‬Polycotylidae‬, Polycotylinae

Polycotylus was a basal plesiosaur from the Late Cretaceous. Anyways, one really interesting fossil specimen (LACM 129639) was discovered with a fetus inside of it. The discovery of this amazing specimen helped paleontologists determine that Polycotylus and other plesiosaurs were most likely viviparous and gave birth to their young directly underwater. This completely shatters the obsolete idea that these marine reptiles hauled themselves on land to lay eggs or gave birth on land. In addition, the single fetus in the mother most likely meant that plesiosaurs used the K-selection strategy for caring/parenting their offspring. The K-selection strategy involves parent(s) dedicating more time and effort in raising typically one offspring at a time until they reach full maturity.

LACM 129639 specimen of P. latipinnis with fetus. Photo by: Dawn Pedersen [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Sources:

http://www.prehistoric-wildlife.com/species/p/polycotylus.html

https://en.wikipedia.org/wiki/Polycotylus

https://en.wikipedia.org/wiki/R/K_selection_theory

[ancientmarinereptiles]

Sulcusuchus erraini

Photo by: Gasparini & Spalletti

Name: Sulcusuchus erraini

Name Meaning: ‬Trough crocodile

First Described: 1990

Described By: Gasparini & Spalletti

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauroidea,‭ ‬Polycotylidae‬

Sulcusuchus was actually a polycotylid plesiosaur that lived during the Late Cretaceous. It was unearthed in Argentina’s La Colonia Formation. It was originally thought to have been an ancient crocodile, hence the suffix ‘suchus’ of its generic name. Sulcusuchus was thought to have been an ancient crocodile from 1990 until 2013, 23 years later it was realized that it was really a plesiosaur.

Sources:

http://www.prehistoric-wildlife.com/species/s/sulcusuchus.html

https://en.wikipedia.org/wiki/Sulcusuchus

[ancientmarinereptiles]

Plesiopleurodon wellesi‭

Art by: Dmitry Bogdanov, CC BY 3.0

Name: Plesiopleurodon wellesi‭

Name Meaning: ‬Near Liopleurodon

First Described: 1996

Described By: Carpenter

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria, Plesiosauroidea,‭ ‬Polycotylidae

This Late Cretaceous polycotylid swam the seas of the Western Interior Seaway of North America. It was discovered in the Hailey Shales Formation. What was found of Plesiopleurodon consisted of a complete skull, cervical (neck) vertebrae, lower mandible (jaws), and part of its right shoulder.

Sources:

http://www.prehistoric-wildlife.com/species/p/plesiopleurodon.html

https://en.wikipedia.org/wiki/Plesiopleurodon

[ancientmarinereptiles]

Plesiosaurus dolichodeirus

Art by: Andrey Belov, https://www.deviantart.com/abelov2014/art/Fish-Dapedium-Plesiosaurus-dolichodeirus-666113848

Name: Plesiosaurus dolichodeirus

Name Meaning: ‬Near lizard

First Described: 1821

Described By: Conybeare‭

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria, Plesiosauroidea,‭ ‬Plesiosauridae

Plesiosaurus lived during the Early Jurassic, and they actually weren’t as large as you’d think, because they were about 11 feet (3.5 meters) in length. We have lots of fossil specimens that have been found for the genus, but in the past, Plesiosaurus was once the poster child for being a wastebasket taxon. Anyways, Plesiosaurus in contrast to other plesiosaurs, had very small heads. In addition, the positioning of their nares (nostrils) indicate that Plesiosaurus most likely didn’t have a sense of smell while submerged under water. They most likely could not hold their necks out of the water especially like a swan “S” shape as popular media often depicts them. Also, Plesiosaurus and other plesiosaurs were probably obligatory marine, meaning they could not venture on to land because their bodies could not support their weight. Since they were obligatory marine animals, they were most likely viviparous and gave birth to live young underwater.

Sources:

http://www.prehistoric-wildlife.com/species/p/plesiosaurus.html

https://en.wikipedia.org/wiki/Plesiosaurus

[ancientmarinereptiles]

Tricleidus ‬seeleyi

Art by: AlternatePrehistory, https://www.deviantart.com/alternateprehistory

Name: Tricleidus ‬seeleyi

Name Meaning: ‬Three collarbone

First Described: 1909

Described By: Andrews

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ ‬Plesiosauroidea, Cryptoclididae

Tricleidus was a cryptoclidid plesiosaur discovered in England in Norway. This plesiosaur swam the Middle Jurassic seas and most likely hunted for fish. We have unearthed a skull and some of its post-cranial skeleton.

Sources:

http://www.prehistoric-wildlife.com/species/t/tricleidus.html

https://en.wikipedia.org/wiki/Tricleidus