#speculative

[makairodonx]

Spectember 2025 Day 30: Eobasilosaurus giganteus

What would mosasaurs look like if they have evolved to become baleen whale-like filter-feeders?Already towards the last 20 million years of the Cretaceous, from the Turonian to Maastrichtian stages, these aquatic cousins of monitor lizards were reaching the peak of their evolutionary diversity following the extinctions of the icthyosaurs and giant pliosaurs. Some of them such as Globidens and Platecarpus were specialized ammonite or fish eaters, some such as Mosasaurus hoffmani and Tylosaurus proriger were giant apex predators, and others such as Megapterygius and Plotosaurus developed large flippers and even small dorsal fins and were highly specialized, fast-moving pelagic or open-ocean hunters. But had the Cretaceous-Palaeogene extinction event never occurred, the shapes and sizes achieved by the mosasaurs might have been even greater, and some of them could become the largest marine animals the world has ever known.

Eobasilosaurus giganteus is a species of gigantic tylosaurine mosasaur which inhabits the shallow tropical ocean waters of an alternate earth in which the asteroid impact never occurred and the non-avian dinosaurs never went extinct, as well as the seas which surround Sekaia’s island continent of Aetherosia. Having evolved from a Tylosaurus-like ancestor around 66-56 million years ago, Eobasilosaurus represents a peak in mosasaur evolution in that it is a filter feeding hunter of small to-medium-sized fish and marine reptiles which occupies a similar niche to the late Triassic icthyosaur Icthyotitan, and its long, unhinged jaws and small but sharp teeth support a wide system of baleen rakes that can be opened or shut to trap in hundreds of fish in a single gulp. Like all mosasaurs, Eobasilosaurus is oviparious, giving birth to about 4 to 6 offspring, and the young stay very close to their mother until they reach the age of 10 and wander off to forage on their own. The species is also highly territorial, with adult males patrolling vast swathes of open ocean hunting or mating grounds and fighting off intruders with their toothy jaws and slaps of their large flippers and tails. With a head and flipper length ranging from 4.5-5.5 meters and a total body length of 34-35 meters from the tip of the snout to the end of the tail, Eobasilosaurus giganteus is not only the largest marine reptile of the Cretaceous, but also the largest Mesozoic reptile ever to have existed.

[chemical-bunz]

Alien Isabaeu for my Humans Are Space Orcs au!

He’s an animal handler and security detail for a marine biology lab and can move incredibly fast underwater!

Organs and height comparison to Siffrin under the cut!

[cheerypoptart]

What if therizinosaurus was epic and bird?

[aammorbidccuriosity]

So like I've been thinking about this whole thing about later pterodactyloid pterosaurs losing their tails as they became more advanced flyers, with earlier forms retaining them as a kind of "flight stabilizer" whilst they kinda got to grips with the whole flight thing. Trouble is, this has never really seemed a satisfying theory to me personally. Creatures like Rhamphorynchus were already clearly very sophisticated flyers in their time, with birds having lost their tails very early on precisely BECAUSE they cause drag and flight instability. Birds today such as swallows and terns that have deliberately developed long tail streamers have done so as an adaptation to more technical flight styles, playing off of sacrificing some efficiency for causing themselves deliberate drag that they can use to perform sharp and precise areal maneuvers. By contrast, soaring birds such as albatrosses have very short reduced tails as they focus primarily on long distance efficiency, which tracks well with the more long distance soaring lifestyles of a lot of later large pterosaurs. I dunno if anyone out there with more of an academic background might have some input on this, this is just my personal thoughts. Anyway, possible food for thought..?

EDIT

A word. Later pterodactyloid tailless pterosaurs evolved from earlier tailed rhamphorynchoid forms

[cellulosaurus]

Various speculative adults of “compsognathids”

i’m a big fan of the idea that all these species are juveniles/hatchlings of various theropod clades (megalosauroids for Compsognathus and Sciurumimus, spinosaurid for Scipionyx and basal coelurosaur for Sinosauropteryx)

[cakedotexe]

My home-made [creature] called █████.

⌞ I don't have a name for it yet, though ! (sooo it's just called [creature] for now. I'm up for suggestions) sorry it's a long read, tell me what u think!!! ⌝ 💉❤️

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Many of these symptoms overlap or are repressed by the [creature]; all [creatures] are one of a kind. The [creature] is a medical condition that is (as of now) incurable. This condition is categorized by near-human behavior that possesses specific physical and physiological tells. They are physically human, but biologically, they are alien. The [creature] once born does not know what it is, nor does it realize its nature. 80% of all [creatures] are unaware they are a biological anomaly, while the other 20% are often dangerously aware.

━━━━━━━━━━━━━━━━Biological behavior:━━━━━━━━━━━━━━━

➤ Spying & Watching -

Spying is the state of frequent, constant, or burst stalking, most commonly, in secret or without knowledge of the victim. This often appears more frequently in [creatures] that are more aware of their impulses.

Watching is the state of constant, often long, fixated staring in the presence of the victim, which they often don’t realize they are doing.

➤ Pinning -

Pinning is characterized by frequent and often constant appearances of the [creature]. This behavior usually points to the [creature] taking a deep, often incorrect liking to the victim. Pinning is an active choice of acknowledgment to the victim by the [creature]; their pins are (frequently) not random, but the intensity is. Pinning types include, but are not limited to:

Erotic (or Obsessive): This type of pinning is categorized by a possessive, clingy, and/or sexual attachment to the victim, commonly without solicitation from the victim. This specific pin is more frequently directed at people whom the [creature] sees as attractive or shows them attention.

Platonic: Platonic pinning is characterized as a friendly, non-sexual relationship towards the victim that the [creature] holds in high regard.

Melancholic: This form of pinning is characterized as a form driven purely by loneliness (or the longing for companionship) and is one of the few pinning types with the least harmful effects on both the victim and the [creature].

Sudden (or desperate): Sudden pinning (or desperate) pinning is characterized as a sudden, often desperate form of connection driven by loneliness or solitude. This often occurs in [creatures] that have been ridiculed.

➤ Taboo attraction - 

The [creature] is more likely to gain a strange attraction to taboo, weird, or dangerous items or characteristics, such as but not limited to: Needles, Flesh (often specifically, red pigmented flesh), Sharp objects, The human body, Rubbery textures, Leather, and more.

➤ Adrenaline runners - 

The [creature] often gains an intense rush of adrenaline when running or chasing someone. This act has little to do with the maliciousness of the reason for the run.

━━━━━━━━━━━━━━━━Differences:━━━━━━━━━━━━━━━━━━━━

➤ Reproduction -

Reproduction, while oftentimes difficult, is possible. If a [creature] and a human successfully give birth, two of the following can occur: 

There is a 65% chance that the child will be a [creature]. The [creature] gene is often significantly more dominant than the human gene, but the [creature] gene is drastically more affected by pre-birth usages (drugs, alcohol, medication, ect) by the mother, which often leads to fetal death. There is a 40% chance that the child will be human. When this occurs, the human in some cases may carry the [creatures] recessive gene, which can (as tested) be bred out.

If a [creature] and a [creature] successfully give birth, the child will always be a [creature].

➤ Physicality -

[Creatures] have a significantly higher chance to be taller, approximately around ~6’0 to 6’8, although shorter [creatures] do exist.

[Creatures] often have a visibly malformed or closed belly button. This is the only physical manifestation of this condition.

The [creatures] often struggle to understand their own anatomy and its function, which often leads them to pick, touch, or inspect themselves.

➤ Sub-sequence injury - 

Sub-sequence injury is a less severe form of decay; it involves a secondary injury to nearby tissue. Small nicks and pokes do not apply.

Large injuries:

With large wounds, the [creature] may experience the dislocation of the nearest joint, extreme pain, constant bleeding, and expansion of wounds.

Medium injuries:

With medium wounds, the [creature] may experience the dislocation of the nearest joint, medium to extreme pain, bleeding, and expansion of wounds.

Small injuries:

With small wounds, the [creature] may experience a ripple or tear surrounding the wound, making it larger and often deeper. This can apply to the above injuries.

➤ Extreme Weeping - The [creature] often, in overwhelming situations, may weep in a constant, violent state, often causing eye swelling and occasionally bleeding.

end of document.

[namu-the-orca]

Look guys here's a really cool commission I recently got to work on. Someone asked me to create a speculative illustration of a hybrid between a False killer whale and Pacific white-sided dolphin. A very fun mental exercise with a little sleuthing involved!

The intended hybrid does not exist as far as we know, however both Lags and Pseudorcas have hybridised with - you guessed it - our favourite free-for-all baby maker the Common bottlenose dolphin. By looking at those hybrids I could see how the different colour patterns interacted, and try to sort of "filter out" the middle man. Lucky for me, Pseudorcas have a very similar colour scheme to bottlenoses, so I could make some inferences there too.

I'm quite pleased with the end result! Of course I can't say whether this is truly what a hybrid between these species would look like, but I do think it's a well informed guess. Makes for a pretty dolphin!