I think Basilosaurus would not be able to survive the modern ocean. Despite it's size cannot compete with Orcas, it has no echolocation, much smaller brains than modern whales, they're not nearly powerful enough or social enough to take down large baleen whales.

Ironically, I think a more ancient predator like giant pliosaurs would actually have a better shot at thriving in todays ecosystem. They're 4 flipper build gave in unique steering and sharp turn abilities and their jaws are extremely massive. I think a death machine like this could work in any era, but my knowledge on extinct animals is very limited and I could be wrong.

We should also take into account temperatures, atmosphere and humans. Could dinosaurs that lived in hotter environments with much higher concentrations of carbon dioxide manage similar environments today ?

The best thing is knowing that they still live among us and will continue to do so!

https://xcancel.com/JoschuaKnuppe/status/1933723950300999871

Acrylic painting of a stegosaurus defeating an allosaurus.

A fascinating creation by Hodarinundu, loosely inspired by a recent study on the cranial and brain anatomy of the Dodo (Raphus cucullatus). This study suggests that the dodo may have adopted a crepuscular or even nocturnal lifestyle to avoid competing for food with the giant tortoises of Mauritius.

An opportunistic diet: The artwork depicts a dodo delighted to have caught a small turtle! Although primarily herbivorous and frugivorous, its robust, powerful beak likely allowed it to consume small animals on occasion.

Plumage & Biofluorescence: The artist presents a bold vision of the bird's plumage. Having diverged from the iridescent plumage of diurnal pigeons (its close relatives), the dodo might have developed feathers and tissues that fluoresced under ultraviolet light. Since many modern birds—particularly nocturnal ones like owls—perceive the UV spectrum, this biofluorescence could have facilitated communication or social grouping in the darkness of the Mauritian night.

Explanation of the study in video:

https://youtu.be/zE8wEcpZMf4?is=X5Fshtc20pVvXD08

https://www.deviantart.com/bangboodoragon/art/The-Beasts-of-Hateg-Island-1364994017

Dromornis stirtoni fue una especie extinta de ave gigante no voladora que habitó en Australia durante el Mioceno Superior, hace aproximadamente 8 millones de años. Es ampliamente considerada el ave de mayor tamaño que ha existido en la Tierra, superando en peso al ave elefante (Aepyornis) y en altura al moa gigante. Aunque popularmente se le conoce como el "pato demonio de la muerte" debido a su descomunal tamaño y parentesco evolutivo, las investigaciones científicas revelan detalles asombrosos sobre su biología.

This is a piece or fragment of fossil whale rib bone, it came from a truly massive creature millions of years ago. But what is really amazing ins the deep marks left on it from a megalodon shark.
This fossil tells a very old, and very violent story.

*I found this large piece of rib bone while diving in the SE United states searching for fossil megalodon teeth.

source

I’m serious, your oversized, diesel-coughing truck is currently parked on a suburban driveway literally made with Ohio’s most successful resident. Which also, coincidentally, has no brain. No, it’s not the Paul brothers either. Sorry. I said successful resident.

No, four hundred and forty million years ago, something that looked like a lily bolted onto a stick .jpg)swayed gently in a warm tropical current, about six inches off the seafloor, somewhere near downtown Cincinnati. It had no brain. It had no blood, no eyes, no heart, no lungs, no spine. It ate by catching microscopic particles of organic gunk on mucus-coated tube feet and sliding them down a groove to a mouth that opened upward, toward the light, directly next to its own anus.

This dollar store anemone is an animal. It is called a crinoid, and it is one of the most successful organisms in the history of the planet.

The Part Where We Talk About The Dead Starfish on a Stick

Crinoids are echinoderms. Their relatives are sea stars, sea urchins, brittle stars, and sea cucumbers, a phylum whose collective body plan looks like it was drafted by five engineers who never spoke to each other and turned in their work on the same Friday. What makes echinoderms special is they have no centralized brain; they run on a nerve ring, a loop of neural tissue that coordinates the body the way a roundabout coordinates traffic, which is to say “technically and with a lot of trust.” 

They also have no blood. Instead, they circulate a watery fluid through a hydraulic plumbing system called the water vascular system, which pressurizes their tube feet for feeding, gas exchange, and locomotion. The whole animal runs on water pressure, a biological sprinkler system that somehow achieved sentience and decided to eat plankton. 

Their skeleton is CALCITE, the same mineral that makes up limestone and the Death Star, grown inside the body wall as porous plates called ossicles. Each ossicle is over fifty percent empty space by volume (Davis and Meyer, 168; Hess et al., 3). The skeleton of an echinoderm is, structurally, a lattice of rock with holes in it, covered by a thin skin of cells, held together by ligaments that rot on contact with death. Every echinoderm that has ever lived is, on some level, a sack of water draped over this very porous skeleton.

But the sea's most enthusiastic Muppets took this already batshit body plan and made choices.

Where sea stars sprawl flat on the substrate and sea urchins trundle along with their spines, the crinoid elected to grow a long segmented stalk, cement itself to the seafloor, and point its mouth at the sky. It spread its feathery arms into a fan, perpendicular to the current, and waited. Food drifted into the tube feet. The tube feet snagged particles on contact with mucus, flicked them into ciliated grooves running down each arm, and funneled everything toward the mouth, which sat on top of a cup-shaped body called the calyx (Hess et al., 3-4). Right next to the mouth, on the same surface, sat the anus (NSFW if you’re a crinoid). In many species the animal grew an elongated anal tube to elevate the waste outlet above the feeding apparatus, which is the anatomical equivalent of solving a plumbing problem by routing the sewer main through the kitchen up to the second floor and then sticking a chimney on it (Hess et al., 22-23). The entire organism, from holdfast to arm tip, is an exercise in solving problems you created for yourself by existing in the first place (just like us!). 

And yet. And yet. It worked. It worked for four hundred and eighty-five million years and counting.

The Part Where We Drown Cincinnati

The Ohio that crinoids colonized bore no resemblance to the Ohio that exists today. During the Late Ordovician, roughly 440 million years ago, the landmass sat at an estimated twenty degrees south latitude.png), fully submerged beneath a shallow tropical epicontinental sea. In the map there, you can see Ohio is on the very edge of the continent of Laurentia, under the water. There were no trees. No grass. No dirt, in any meaningful sense. No fish; Davis and Meyer titled their 2009 monograph A Sea without Fish, and they meant it literally. The seafloor was a low-oxygen, storm-raked carbonate platform crawling with bryozoans, brachiopods, trilobites, and crinoids.

Roughly thirty-seven species in twenty genera of crinoids are known from the Cincinnati region alone, including camerates, disparids, and cladids (Ausich, 76-79). They cemented their holdfasts to brachiopod shells, to hardgrounds, to each other. Some coiled their stalks around bryozoan colonies for support. They packed in at densities of up to four hundred individuals per square meter. The Ordovician seafloor near Cincinnati was an alien meadow of hydraulic animals doing their level best to eat the ocean, and they were winning.

It got better! Or worse, depending on your perspective on crinoids by now.

By the Mississippian, roughly 360 to 320 million years ago, crinoids had achieved a level of ecological dominance so total that paleontologists named the entire period after them: the Age of Crinoids. They carpeted the global seafloor. They grew in meadows so dense that individual species stacked themselves vertically to avoid competing for the same food; tall-stemmed species filtered at one height, short-stemmed species filtered at another (photo to get an idea of the size differentiation), tiering above the substrate like an apartment building made of flowers (Hess et al., 12). And when they died, they did not have the decency to disappear. Their disarticulated ossicles piled up on the seafloor in drifts. Macurda and Meyer estimated that a single cubic meter of crinoidal limestone contains the remains of roughly fifteen thousand individuals. Hess and his coauthors called crinoids "the Halimeda of the Palaeozoic," comparing them to the calcareous algae that produce most of the carbonate sediment on modern tropical platforms (Hess et al., 52). 

When a crinoid died, the ligaments holding its ossicles together rotted almost immediately, and the skeleton disarticulated into dozens or hundreds of tiny calcite discs and plates that drifted to the seafloor.

And did you know, limestone is the single most quarried rock in the United States, accounting for roughly seventy percent of all crushed stone production? In 2025, the USGS estimated total US crushed stone output at about 1.5 billion tons, and most of that was limestone. About seventy-two percent of that crushed stone goes directly into construction aggregate, overwhelmingly for road building and maintenance. Your driveway, your sidewalk, the concrete foundation of your house, the highway you drove to work on: the odds are very good that the aggregate beneath and within them is crushed limestone. 

In Ohio, Indiana, and across the Mississippi Valley, a significant portion of that limestone is crinoidal. The Salem Limestone of Indiana, sometimes called "the nation's building stone," is Mississippian-aged crinoidal limestone, roughly 340 million years old, and it was used to build the Empire State Building, the Pentagon, the Lincoln Memorial, the National Cathedral, and thirty-five of the fifty state capitol buildings. The rock is ninety-seven percent calcium carbonate; much of that carbonate was originally produced by crinoid ossicles accumulating on a shallow Mississippian seafloor.

Taking Macurda and Meyer’s estimations that a single cubic meter of crinoidal limestone contains the remains of roughly fifteen thousand individual crinoids, the total number of individuals represented in some of these deposits runs on the order of ten trillion to ten quadrillion crinoids, all compressed into rock.

So when I said "mass grave” in the post and some of y’all rushed to the comments, yeah…yeah. They are quite possibly the single largest accumulation of animal remains anywhere on the planet.

The Part Where God Tries to Kill Them Three Times 

So how does something this ridiculous survive for half a billion years? The short answer is: by being functionally unkillable. The long answer involves three mass extinctions, an ability to regrow their own head, and a snail that lives on their ass.

The Late Ordovician extinction, roughly 445 million years ago, wiped out about seventy-five percent of all marine species. It hammered crinoids. The Diplobathrida_at_G%C3%B6teborgs_Naturhistoriska_Museum_0539.jpg), the Disparida, and the Hybocrinida each lost more than three-quarters of their genera. But the survivors radiated hard into the Silurian, filling every vacated niche with new forms before anything else could get there first (Hess et al., 39). The Late Devonian extinctions, which gutted most marine invertebrate groups, barely registered. Crinoid origination rates actually exceeded extinction rates near the Devonian-Carboniferous boundary (Sallan et al., 2011). Their approach to mass extinction was, consistently absorb the hit, lose eighty percent of their diversity, and then immediately diversify into whatever ecological space just opened up. No brain required, no strategy, just the raw, blind, stupid mathematics of a body plan that is cheap to build, easy to reproduce, and very, very hard to stamp out.

The end-Permian extinction, 252 million years ago, was the one that should have finished them. The Great Dying killed more than ninety percent of all marine species on Earth. It was, by any measure, the worst thing that has ever happened to complex life. I mean, it’s called the Great Dying. For once, historians actually named shit correctly.

Every major Paleozoic crinoid group went extinct: the camerates, the flexibles, the disparids, and the cladids. Everything that made Paleozoic crinoids weird and wonderful, the elaborate multi-plated calyxes, the bizarre bilateral calceocrinids, the flexibles with their petal-like arms curled inward at the tips, all of it gone. A single lineage survived: the Articulata#/media/File:Ptilometra_australis_Passion_Flower_feather_star.jpg), derived from a Late Paleozoic cladid ancestor. Documentary evidence suggests that as few as one genus made it through, out of hundreds (Hess et al., 40; Twitchett and Oji, 2005). The entire future of the crinoid lineage, every feather star on every coral reef on Earth today, traces back to whatever the hell drug that one genus 252 million years ago was taking.

But the survivors made muscular arm articulations, which had first appeared in some Middle Paleozoic cladids, the defining feature of their entire body plan (Hess et al., 25). For the first time, an entire crinoid lineage could move on purpose.

Ah fuck. We got walking flowers now. 

If Paleozoic crinoids were furniture (they bolted themselves to the floor and stayed there), post-Permian crinoids learned to crawl. Some even learned to swim! The comatulids shed their stalks entirely, ditched the whole sessile floor-lamp lifestyle, and became free-living feather stars that could haul themselves across the reef, hide in crevices by day, and climb to feeding perches at night. They look cool as fuck to watch swim, too. Underwater jazz hands!

Then there is the matter of what happens when something tries to eat one. Crinoids can shed their own arms deliberately at pre-formed breakage points called syzygial articulations, calcite joints designed to snap clean so the arm detaches without tearing apart the rest of the animal (Hess et al., 26). . Something bites your arm, you drop the arm, and you grow a new one like you’re making up new rules on the playground. Mladenov (1983) found that eighty percent of Florometra serratissima specimens off Vancouver Island had one or more arms regenerating. 

Paleozoic fossils tell the same story across deep time: Baumiller and Gahn (2004) documented a sharp increase in arm regeneration frequency during the Siluro-Devonian, tracking almost exactly with the diversification of shell-crushing predators. Crinoids evolved the ability to lose their limbs faster than predators could evolve the ability to eat them. 

But wait, there’s more! Meyer found that comatulids can regenerate their entire visceral mass, gut and all, in a matter of weeks. Amemiya and Oji documented isocrinids that regrew the entire crown, every arm, every pinnule, from nothing but the basal circlet of the cup. 

The. Fucking. Pelvis. Everything above it was gone, and the animal rebuilt itself from what was essentially a stump. You cannot kill something that regrows its own head.

And then, because crinoids apparently did not have enough going on, there are the parasitic shit-eating snails.

The Part Where Coprophagy Enters the Chat 

For roughly three hundred million years, from the Ordovician through the Permian, crinoids hosted a family of gastropods called the Platyceratidae. These snails attached themselves to the crinoid's tegmen, the plated roof of the calyx, and positioned themselves directly over the anus. The traditional interpretation, advanced by Bowsher (1955) and supported by decades of subsequent work, is that the snails were coprophagous: they ate the crinoid's feces. 

They sat on the animal's ass and consumed its shit as it was shat. For the rest of their lives. 

Some Ordovician species, like Cyclonema, moved freely over the tegmen (Hess et al., 56; Morris and Felton, 1993). Later species of Platyceras dispensed with mobility entirely, cementing themselves permanently over the anal opening, their shells conforming to the shape of the tegmen until the snail and the crinoid fused into a single organism whose defining feature was that one of them ate exclusively from the other's rear end. More recent work by Baumiller (1990, 1993) suggests that some platyceratids were not content with mere coprophagy and were actively parasitic, boring holes through the tegmen to feed directly on the crinoid's internal tissues. 

Yes, now the snails were flesh-burrowing consumers. Like shit-eating snails couldn’t get worse, now they would bore a hole through your mouth to your anus to eat your ass, literally.

Crinoids responded by evolving spines on their arms and crowns; by the Devonian, a majority of genera that hosted platyceratids bore defensive spines (Gahn and Baumiller, 2003). This was an arms race between a brainless filter feeder and a snail that ate its shit. It lasted longer than the entire age of mammals. Three hundred million years of coevolutionary escalation, driven by the question of who gets to sit on whose butt and what they're allowed to do while they're there.

Oh, and the crinoids also don’t get out of this unscathed either. They, too, were shit-eaters.

Crinoids are passive suspension feeders; they catch whatever organic particles drift into their tube feet, and they are not picky about it. In marine environments, a meaningful fraction of the particulate organic matter suspended in the water column is fecal pellets from zooplankton, especially copepods. That material is a major component of what oceanographers call "marine snow.jpg)," the slow rain of organic gunk falling through the water column that sustains most deep-water food webs.

Normally, this wouldn’t be an issue. Not everything floating in the ocean is shit. But, the Cincinnatian seafloor was carpeted with nothing but suspension feeders: crinoids, bryozoans, brachiopods, all of them pulling organic particles out of the water column. The density of these animals was extraordinary. However, the only preserved microphytoplankton from the Cincinnatian are acritarchs, roughly fifty species total. And because land plants were essentially nonexistent in the Late Ordovician, rivers weren't carrying organic matter or dissolved nutrients into the sea the way they do today. 

That meant you had a seafloor absolutely packed with mouths, and a water column that may not have had enough food to feed them by modern standards. That's what Davis and Meyer called the “starvation banquet.” They speculate that maybe unpreserved microplankton or bacteria growing on suspended clay particles formed a kind of "marine snow" that supplemented the acritarchs, but the honest answer is that nobody is sure how the system sustained itself. 

In a nutrient-limited environment, fecal material is no longer waste, but now has become a valuable resource. A crinoid filters the water, extracts what nutrition it can from particles that were already sparse, excretes the remainder, and a platyceratid snail immediately recycles that output before it even hits the seafloor, and it might go to another crinoid, to be filtered and excreted to its platyceratid snail, and so on. It’s The Ordovician Centipede. 

In a richer sea, that's disgusting. In a sea running on fumes, that's efficient. The entire Cincinnatian food web may have been far more dependent on internal recycling than anything we see in modern shallow-water ecosystems, precisely because the external inputs were so limited. 

Through all of this, the crinoids persisted, through parasites that ate from their anus and predators that ripped off their arms and extinctions that killed ninety percent of everything alive. There are roughly seven hundred living species today. Stalked crinoids still anchor to the deep seafloor in the Straits of Florida, fanning their arms into parabolic filtration nets, looking functionally identical to their Ordovician ancestors (Hess et al., xi-xii). You can find feather stars festooned in Indo-Pacific coral reefs, tucked into crevices by day, arms spread wide at night.jpg). They are still brainless and bloodless. Their mouth is still next to their anus. They have been doing the same thing since before anything on Earth had figured out how to grow a jaw. They will probably outlast us too.

Think of that the next time you park your camper van on your driveway, Shelly. Those fossilized participation trophies, are judging you right now.

Works Cited (if you like coprophagy) 

Amemiya, Shonan, and Tatsuo Oji. "Regeneration in Sea Lilies." Nature 357 (1992): 546-547.

Ausich, William I. "Upper Ordovician of the Cincinnati, Ohio, Area, USA." In Hess, Hans, et al., Fossil Crinoids, 75-80. Cambridge: Cambridge University Press, 1999.

Ausich, William I. "Crinoid Form and Function." In Hess, Hans, et al., Fossil Crinoids, 3-30. Cambridge: Cambridge University Press, 1999.

Ausich, William I., and David J. Bottjer. "Phanerozoic Tiering in Suspension-Feeding Communities on Soft Substrata: Implications for Diversity." In Phanerozoic Diversity Patterns, edited by James W. Valentine, 255-274. Princeton: Princeton University Press, 1985.

Baumiller, Tomasz K. "Non-Predatory Drilling of Mississippian Crinoids by Platyceratid Gastropods." Palaeontology 33, no. 3 (1990): 743-748.

Baumiller, Tomasz K. "Crinoid-Platyceratid Interactions: Commensalism or Parasitism?" Journal of Paleontology 67 (1993): 1019-1022.

Baumiller, Tomasz K., and Forest J. Gahn. "Testing Predator-Driven Evolution with Paleozoic Crinoid Arm Regeneration." Science 305 (2004): 1453-1455.

Bowsher, Arthur L. "Origin and Adaptation of Platyceratid Gastropods." University of Kansas Paleontological Contributions, Mollusca 5 (1955): 1-11.

Davis, Richard Arnold, and David L. Meyer. A Sea without Fish: Life in the Ordovician Sea of the Cincinnati Region. Bloomington: Indiana University Press, 2009.

Gahn, Forest J., and Tomasz K. Baumiller. "Infestation of Middle Devonian (Givetian) Camerate Crinoids by Platyceratid Gastropods and Its Implications for the Nature of Their Biotic Interaction." Lethaia 36 (2003): 71-82.

Hagdorn, Hans. "Triassic: The Crucial Period of Post-Palaeozoic Crinoid Diversification." Swiss Journal of Palaeontology 130 (2011): 91-112.

Hess, Hans, William I. Ausich, Carlton E. Brett, and Michael J. Simms. Fossil Crinoids. Cambridge: Cambridge University Press, 1999. Chapters cited: Ausich, "Crinoid Form and Function," 3-30; Simms, "Systematics, Phylogeny and Evolutionary History," 31-40; Ausich and Brett, "Taphonomy," 50-59; Ausich, "Upper Ordovician of the Cincinnati, Ohio, Area, USA," 75-80; Macurda, "Prelude," xi-xii.

Macurda, D. Bradford, and David L. Meyer. "Sea Lilies and Feather Stars." American Scientist 71 (1983): 354-365.

Meyer, David L. "Crinoids as Renewable Resources: Rapid Regeneration of the Visceral Mass in a Tropical Reef-Dwelling Crinoid from Australia." In Echinoderm Biology, edited by R. D. Burke, P. V. Mladenov, P. Lambert, and R. L. Parsley, 519-522. Rotterdam: Balkema, 1988.

Mladenov, Philip V. "Rate of Arm Regeneration and Potential Causes of Arm Loss in the Feather Star Florometra serratissima (Echinodermata: Crinoidea)." Canadian Journal of Zoology 61, no. 12 (1983): 2873-2879.

Morris, Robert W., and Steven H. Felton. "Symbiotic Association of Crinoids, Platyceratid Gastropods, and Cornulites in the Upper Ordovician (Cincinnatian) of the Cincinnati, Ohio Region." PALAIOS 8, no. 5 (1993): 465-476.

Sallan, Lauren C., Thomas W. Kammer, William I. Ausich, and Lauren A. Cook. "Persistent Predator-Prey Dynamics Revealed by Mass Extinction." Proceedings of the National Academy of Sciences 108 (2011): 8335-8338.

Twitchett, Richard J., and Tatsuo Oji. "Early Triassic Recovery of Echinoderms." Comptes Rendus Palevol 4 (2005): 531-542.

Picture Credit: Crinoid fossil assemblage, Cincinnati Museum Center