A 120 million-year-old example of polycephaly, found in China in 2006. This is a bizarrely two-headed fossil of a newborn Hyphalosaurus, a member of a group of extinct semi-aquatic reptiles known as choristoderes.

Hyphalosaurus lived in freshwater lakes, and their remains are so numerous that their entire lifespan is represented from embryos to fully grown adults. Females have even been found with developed embryos still inside their bodies, showing that they gave birth to live young.

Once again, Champsosaurus by Frederik Spindler. I’m starting to run out of respectable champsosaur pics.

- Choristoderes appearently are the sister taxa to Rhynchosauria. You know, the ugly rodent-like archosauromorphs. In restrospect, the giant temporal fenestrae and associated muscles make sense.

- Champsosaurus probably was fully aquatic after all. The female forelimbs certainly allowed for movement in the shallows, but true terrestrial locomotion was appearently difficult if not impossible. Likely, they gave birth on the shores or on highly vegetated swamp environments.

- Monjurosuchus was appearently ovoviviparous, suggesting that ovovivipary was quite basal for these animals.

- The Greenland Champsosaurus fossils were found in association with turtles. These turtles were appearently dermochelids. There’s also coral fossils, so it was definitely a marine environ.

- There’s appearently a Campanian fossil from Austria (Buffetaut, 1989), which does suggest they travelled across the sea from Asia/North America to Europe.

Marine Reptile Month #2 — Tchoiria

Early Cretaceous period (125-112 mya)

Although technically a freshwater reptile, Tchoiria is a member of an interesting yet often-overlooked group known as choristoderes. Despite its rather gharial-like appearance this 1.5m long (~5ft) animal wasn’t related to any of the crocodyllians — it was fully aquatic, spending its entire life in the water, and probably gave birth to live young.

Choristoderes actually lived through the K-Pg extinction event, with some forms surviving until the end of the Oligocene epoch 34 million years ago. One species, the small lizard-like Lazarussuchus, made it even further, with fossils known from just 20 million years ago in Europe.

Color palette used: “Christmasy

Champsosaurus snout. Several workers have compared champsosaur teeth and snout shape to modern Lepisosteus gars.

As I’ve discussed previously, champsosaurs were basically like freshwater marine reptiles, being fully aquatic as opposed to modern amphibious crocodillians, turtles and water lizards. I even compared them to modern river dolphins, also fully aquatic freshwater predators with gavialine jaws that incidently also seem to display cryptic behaviour.

It came to my attention recently that a very good modern analogue for neochoristoderes might actually be lepisosteidid fish, aka gars. Again, both are slender jawed, fully aquatic freshwater hunters with cryptic behaviours, but gars take one step further by relying on their pectoral fins for propulsion (just like choristoderes used their paddle like limbs), co-existing with similar crocodillian faunas that occured in neochoristodere fossil sites, occuring in temperate latitudes and in salt water environments, having similar integrument (though lepisosteidids have far more robust scales) and even having eyes located in a medium, forward oriented position in the skull (unlike the eyes of crocodillians, hippos and amphibious vertebrates, with eyes on a very dorsal position), as indicative of the reliance of eyesight in hunting.

Recent studies appearently have shown that the snouts of Lepisosteus and Atractosteus are uncannily similar in shape to those of Champsosaurus and Simoedosaurus respectively, and neochoristodere teeth have historically been noted as very gar-like.

Considering modern gar genera co-existed with neochoristoderes, this is especially interesting for our understanding of early Cenozoic aquatic biomes. Studying gars might also shed light as to why these fish survived and neochoristoderes died out.

Mammal-Like Choristodere: Failtastic addition to the Yesterdays movement

So, basically, with Nemo Ramjet’s All Yesterdays competition, I gave my shot with my luck charms, the champsosaurs. Here is a horrendously failtastic depiction of a Champsosaurus gigas engaging in a mammal-like defense pose.

Let’s take a closer look, shall we?

First off we have the snout. Loosely inspired by giant snalamanders and cetaceans, this is one of the few pics in existence of champsosaurs with lips (based on soft shells and other aberrant turtles). I also have it a “rhinarium”; champsosaurs, much like mammals and crocodiles, usually have fused nares. The weird things along the jaws are fleshy “whiskers”, akin to those of some salamanders.

Here we see it with the tail raised and waving on the water, much like newts do today, only with a more mammalian angle. The feet are deliberately made rounded and simplistic because choristoderes actually had paddle-like limbs, hence something between a flipper and a land vertebrate leg.

A closer inspection at the tail. It has loose patterns, also newt inspired, and deliberately raised in a skunk style.

Another look at the flipeprs/paddle-like limbs, raising the animal erect over the sea floor, presumably in a territorial display. In the far corner there is another male; I intended it to be actually attracted to the main displaying male (not enough pics of homosexuality in choristoderes, ha!), but you can also interpret it as fleeing or something.

A final, closer look at the snout. The lips are bigger on the upper jaw, making the snout look thicker than it actually is. In the lower jaw, you can still see the teeth.
A Simoedosaurus' Journey part 1

Dzhylga, Kazakhstan, Late Eocene.

One day, this will be a cold desert. But now, the old Tethys stretches itself, breathing in warm water from the Indian Ocean, and exhaling it int he Arctic. To the west, there lies a chain of islands that will be Europe; to the east, a fragmented Central Asia, warm seas spreading across what was a few decades of milions of years ago a cold desert dominated by dinosaurs, and that one day will be a cold desert again. But, again, in this warm world, the sea dominates, relaxed and calm, it’s warmth heating up all landmasses. This is the closest thing to Eden that Earth has ever experienced.

And the hints of the Dantesque frozen hell begin surfacing in the horizon.

For now, on this shallow sea, plains exist underwater. Seagrass expanses have appeared for the first time, colouring in green an ocean where the only plants were once seaweed and plankton. How ironic, that the water demanding plants only now decided to invade the sea. This suits the herds of sirenians and desmostylians just fine; one day, here, there will be grass, but it will be grazed by mammoths, relatives of these aquatic mammals, whose ancestors are now tapir like things in a swamp several miles to the south.

There are only two seasons here, a reflection of the land seasons: wet and dry. It is the wet season, when the rivers vomit freshwater in the ocean, and the Arctic defrosting feeds the Tethys. The grass is pleased, and so are the seacows, replenished by the amrita dropped by the Vishuddha of the continents.

Among the afrotheres swim early whales. They come in many shapes: the remingtonocetids look more like otters than whales, and have long, slender jaws like a gharial’s. Still having normal rhinariums like most mammals, they spend most of their time hunting fish and squid in these underwater plains, only the tip of their snouts surfacing like snorkels. A weirder whale is the Makaracetus: it looks roughly like a seal, though the long hindlimbs and tail are seperate, giving it a slightly frog-like appearence. More interesting, it has a trunk, just like an overgrown desman, which it uses also as a snorkel. Other passing whales have a similar body plan, though they lack snorkels, be them long jaws ending on rhinariums or trunks.

The most recent evolutionary experiment is Pelagoceti, whales that lost all their ties to the land. A lone Dorudon is one such example. It’s hindlimbs are small, useless for swimming and certainly useless for walking. These new whales have began replacing the seal-like forms, with only the slender-jawed and otter-like remingtonocetids and the mollusc specialist Makaracetus being safe from competition, for the moment.

The Dorudon is exhausted; it swam all the way from South America’s inland sea, where the breeding season took place. It is on the middle of a longer journey into Arctic waters, to take advantage of the summer bounty. His black upperside bears the scars of multiple mating mattles, white in colour, each year bleaching his body further. He rests near the surface, too tired to hunt, waiting for nightfall, when benthic squids and fish rise from the depths.

He is also awaiting for another phenomenon.

After several hours, the first evidence of this appears: a strange aquatic reptile, looking like a bizarre mixture between a marine crocodillian and a pliosaur, with a salamander and gar thrown in for good measure, comes from the waters to the northwest, presumably having swam it’s way from Europe.

The female Simoedosaurus touches the surface with the tip of her long snout, inhaling air, before diving, landing on the ocean bottom to rest, her lime skin combining well with the seagrass. She lays inert for several minutes; a perch-like fish passes by, and she snaps her jaws with such an immense force that blood and guts are forced out of the prey’s body. After swallowing, she swims upward, her jaw tips reaching the surface again, before falling off to the bottom, this time swimming slowly, taking a new hunting roost. The curious Dorudon approaches her, his head looking down as he remains near the surface.

She again makes a kill, only to have the whale lap the guts and blood expelled from the fish. Some remingtonocetids notice, and she displays her fierce jaws, threatning to use them on mammalian flesh. None of the whales leave.

Another Simoedosaurus appears, also from the same direction, remaining in a pelagic position, his snout skimming the surface from below, before eventually falling to the bottom.

More and more Simoedosaurus arrive, and soon are the most numerous tetrapods around, outnumbered only by the seacow herds. The remingtonocetids leave, intimidated by the enormous group, while both the Dorudon and the Makaracetus stay, though keeping some distance. Most of the Simoedosaurus rest at the bottom, surfacing occasionally; the schools of small fish are now in a minefield.

Suddenly, the Simoedosaurus males begin their mating bellowing, producing roar like sounds. They soon become long infrasound chants, spreading across the shallows. Soon, the water is filled by swimming Simoedosaurus: females being drawn to particular males, males chasing smaller males, et cetera.

Not too long after, the orgy begins, and continues for the better part of a day, animals spending most of their time either mating or resting.

By the end of the day, the water has white sperm clouds, attracting fish and squid, which in turn are eagerly eaten by the Simoedosaurus. The males retreat back into the northwest, starting the long journey back home. Some are already too exhausted, and cannot bring themselves to surface again. These are quickly eaten by the patient scavengers, including the females. They will stay here; their journey has just started.

3 months latter…

Fig. 1.- Choristoderan skulls drawn to scale: neochoristoderan –a) Simoedosaurus lemoinei (modified from Sigogneau-Russell and Russell,
1978) –b) Ikechosaurus pijiagouensis (IVPP V13283) –c) Tchoiria namsarai (redrawn from Efimov, 1975) –d) Champsosaurus
gigas (SMM P77.33.24): non-neochoristoderan –e) Cteniogenys sp. (Evans, 1990)–f) Lazarussuchus inexpectatus (Hecht, 1992) –g)
Hyphalosaurus baitaigouensis (redrawn from Gao and Ksepka, 2008) –h) Monjurosuchus splendens (Matsumoto et al., 2007) –i) Philydrosaurus
proseilus (Gao and Fox, 2005).

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