Spec-Dinovember Day 30: Spinofaarus’ Revenge, a weird and unexpected reconstruction of your favorite Mesozoic creature

Pachyrhinosaurus canadensis, reconstructed based on the ‘rhinoceros horn’ idea of the '90s, the neck and frill musculature of McLoughlin’s 1979 book (for more see here), and the integument famously suggested by Mark Witton in 2013.

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No this is not anywhere close to an accurate reconstruction, but it was fun! And these three ideas were the most extreme hypotheses I could remember that apply to my favorite dinosaur. McLoughlin’s hypothesis was basically never considered to be possible for a litany of reasons. The 'rhino horn’ idea had some staying power, apparently being advocated by some until as late as 2008! Since Heironymus et. al. done their deep dive into osteological correlates for epidermal structures in 2009 the horn is out of the realm of reality. Witton’s argument for integument is interesting as it seems reasonably possible. Especially since the species within Pachyrhinosaurus are in direct opposition to Bergmann’s Rule, the species get progressively smaller the further north they are. This means that in addition to living in progressively colder climates, they have progressively less thermal inertia due to reduced body size and therefore more reason to develop an insulating integument. P. canadensis here is both the southernmost and largest, so if (big if) it had any fuzz it’s likely be a very sparse coat. What I’ve given here would be more plausible for either of the two more northern species.

Spec-Dinovember Day 29: Blooming Gardener, an early pollinator or seed disperser of flowering plants

Longipterygids are a group of frugivorous enantiornithes with distinctive long snouts. With their association to fruits it was a small leap to begin feeding on flower nectar, their snouts already long and thin to fit within. Pseudotrochilus acutirostris is one such bird. They are generalists and don’t specialize in any particular species of flower, though their snout is better suited to deep and narrow ones. When they attempt to feed on broader, more open flowers such as this Magnolia sp. they can get a little messy

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I don’t have any particular knowledge of plants, let alone knowledge of the reproductive structures of Cretaceous flowers, so I went with a flower I’ve seen IRL and know was present by the end Cretaceous. As for the bird, longipterygids look like they should be like a kingfisher or something but there have been specimens found with seeds in their gizzards so they’re best assumed as frugivores, and to me it seems a logical leap from having a long nose and feeding on fruit to having a long nose and feeding on the thing that becomes fruit.

Spec-Dinovember Day 28: Slurping Around, slurpasaurs as real Mesozoic ceatures

Revisiting the island fauna of Zealandia from days 1 and 6, the local dinosaurs are not the only oddity present as a couple of unexpected lizards call the island home as well. The first is Dolichovaranus aigailos, a plesiopedal mosasauroid related to the ‘Aigailosaurs.’ being plesiopedal it is still terrestrially competent, beaching themselves to sleep and sunbathe before venturing to sea to forage. Though they are theoretically capable of hunting prey on land much as a monitor would, they seem to have already lost the instinct to. However they are not completely passive on the shore, as they will grapple and wrestle each other over prime basking rocks and the most productive stretches of shoreline, these rarely end in serious injury save for competing males during breeding season. The other odd lizard is Eotrioceros ornithophagous, a stem-chameleon that has grown to an unprecedented size in a case of island gigantism. It lacks the full development of their modern relatives’ signature adaptations: the hands and feet are zygodactyl but the fingers and toes are still well separated, the tail is only semi prehensile, and the eyes lack the highly modified eyelid and independent movement chameleons are famous for. It does have the iconic ballistic tongue of a chameleon, and with their great size have turned to using it upon the many birds and pterosaurs that use the island as a migration stop. They are territorial and will spar over the most productive hunting grounds. Despite occupying completely different niches the mutual territoriality of these two species can lead them to combat when flocks and sunning rocks overlap.

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When I first read the prompt list I actually had no idea what a slurpasaur was, I was aware of the practice but I didn’t realize that was the name for it. A slurpasaur is that thing schlocky B-movies from the 40’s and 50’s did where they glued rubber fins and horns and whatever to a live lizard to play the dinosaurs of their movies. A great write-up on them was done by @balanceoflightanddark for those who want to know more (link). Quite a few slurpasaurs were played by monitors, and mosasaurs are related to them so that seemed like a good starting point. There’s also quite a few mosasaurs that retain proper legs that haven’t been modified into flippers, though these taxa are rather small, which is where I got the idea to put them on the island from the beginning of the month. And since we’re revisiting I added the lizards to the size chart (and also reusing the background because time-saving and holiday, you noticed nothing!) The chameleon is a stretch to have here. The oldest definite chameleon is from the Miocene, and the oldest probable chameleon is from the Plaeocene. The Wiki page has a single unsourced line that says they probably split from other lizards around 100mya, so that sounds suuuuuper reliable. There is a critter found in Cretaceous amber from Myanmar that has been called a juvenile chameleon (complete with ballistic tongue even!) but some paleontologists claim it’s actually an albanerpetontid amphibian. Whatever, shaky reasoning be damned, I wanted a chameleon for this because they already grow sails, and head crests, and horns, and kinda look a lil’ slurpy to begin with. The primary inspiration was Trioceros montium with a little bit of Trioceros melleri.

Spec-Dinovember Day 27: No Hands! a theropod loses its little arms

Returning to the Kerguelen Plateau for a final time, the top predator of the island is unsurprisingly an abelisaur. Melesaurus abrachius is a Majungasaurine, and shares their peculiar long torso and short legs. It is the smallest member of its clade weighing only around 200lbs, a clear instance of island dwarfism. It’s preferred prey are the island’s mammal species, many of which create burrows to shelter from the elements. Their small stature and long narrow bodies allow them to reach deep within the burrows to catch their cornered prey. This has led to the almost total loss of their arms, which are nothing more than a singular spur hidden amongst their shaggy down. While mammals make up the bulk of their diet, they aren’t averse to trying new things, as many dinosaurs, lizards, and even a few pterosaurs will make use of abandoned mammal burrows. Occasionally Melesaurus will hunt out in the open, using their low stature and camouflaged coat to hide in the tussocks of grass before ambushing with the explosive bursts of speed abelisaurs are known for. They are the only predators on the island that can attempt to hunt the plateless stegosaur and are the reason they still carry a thagomizer. Attempted hunts are rare and successful ones rarer, but they are a significant cause of 1st year mortality for the young.

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This was a fun locale to play around with. I covered a bit of the geology in the Day 19 prompt, and this chunk may never have actually broke the waterline, but it was neat to work with. Feels a little excessive to do back-to-back prompts in the same area but this one was always intended to pair with Ahoplophorus. Yesterday’s mud sifter was one I didn’t have a good grasp on until it was almost done, and it got put here because A) it would flesh out a location that was already going to be revisited and B) it would be another ceratosaur to contrast with; Numeniasaurus being the really odd shaped one and Melesaurus being the more typical looking one.

Spec-Dinovember Day 26: Mud Sifter, a theropod specialized for feeding on small invertebrates

Returning to Elan Bank and the Kerguelen Plateau from day 19, the limited number of founding taxa present during the bank’s breakaway has allowed many niches to be filled by unorthodox clades. Noasaurs are already unorthodox creatures without an island environment, so the ones marooned here have become even more odd. Numeniasaurus limulus is a elaphrosaurine that has become specialized in feeding on the worms, snails, and crustaceans that burrow into the muddy coastal volcanic sands. They can be found in large flocks feeding on the flats during low tide, retreating to sheltered cliffsides and uplands of tussock grasses during high tide.

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I swear when I started this one I wasn’t looking at ibises! I was going with the idea of Limusaurus as a godwit, but the upturned snout reminded me of Alec Baldwin’s face stretch thing from Beetlejuice, so then I looked at curlews, and when I finished drawing the beak I stepped back and realized that’s just an ibis. Ah well, chalk that one up to convergent evolution and call it a day! So then I leaned into that and gave it a bald head and neck like the Australian white ibis, and a little neck ruff. I wanted to make the ruff into the hood turkey vultures have, as I imagine these critters would have need of keeping warm where I’ve placed them. They’d probably just have fuzzy necks and heads instead, but maybe they need to go bald for picking into beached carcasses or something, I dunno

Spec-Dinovember Day 25: Treehouse, a creature from the canopy of a Jurassic forest

The Jurassic period saw the highest diversity of rhynchocephalians and the origin of redwoods. As the giant trees spread and diversified they brought with them their peculiar canopy ecosystems: dead branches, needles, and epiphytes collect in the crooks of branches and compost into a kind of soil which supports a rich community of plants, lichens, and invertebrates found nowhere else. Naturally something would evolve to capitalize on these resources. Enter the rhynchocephalians, a group of superficially lizard-like reptiles today only represented by the Tuatara, Sphenodon punctatus. Similisaurus loveii is the apex predator of this forest in the sky, hunting down the slugs, beetles, millipedes, and other ‘bugs’ that thrive up there. It captures its prey with the use of a short, muscular, and sticky tongue much like a skink. To aid it in climbing it has gecko-like toe pads and a prehensile tail. The only threats Si. loveii has to contend with are mamenchisaurids eating its home and the rare anurognathid that doesn’t feel like catching insects out of the air.

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This one was hard. Arboreal creatures are hard to preserve because it’s kind of hard to bury treetops without destroying pretty much everything. There are rare finds out there but I didn’t have enough time to hunt down the references, so I winged-it. Tuataras are cool and so are the redwood canopy 'forests’ and luckily they overlapped in time. I don’t know how widespread redwoods would have been in the Late Jurassic, but I know the depositional environment of the Dashanpu locality of the Shaximiao Formation was a large lake surrounded by dense forest. I didn’t specify a place in the description but this area was what I had in my head.

Spec-Dinovember Day 24: Time Warp, a creature from a clade that was not supposed to exist in a given time

In 1914 an Australian farmer found a bit of jaw and tusk in a gulley on his ranch. This fragment was identified as a dicynodont, which was very intriguing because that farmer’s property was on Cretaceous rock. Temnospondyls managed to survive into the Cretaceous in southern Australia so maybe there was a refugium just right to keep these Triassic relics around for so long. After 100 years the fragment was reassessed and was shown to definitively come from a diprotodont which had washed onto the farm from Pleistocene rocks further up the gulley. But what if there were a refugium? Belluchoerus kilmisteri is one of the last dicynodonts, found in the spikemoss savannas and alpine valleys of Antarctica during the mid Cretaceous. Not only is this dicynodont unexpected, but the kind of dicynodont it is is unexpected. During the Late Triassic the dominant lineage of these synapsids were kannemeyeriiformes, namely stahleckeriids. B. kilmisteri is a lystrosaurid, proving once again their survivability. They have not been unchanged by their tenure at the bottom of the world though. They have grown much larger, adults weighing between 800 and 1500lbs on average. To insulate themselves from the months of darkness they have a dense pelt and have taken the final steps toward endothermy. Their forelimbs are now nearly erect, and all the limbs have become digitigrade to help them outpace local theropods. During the summers they gorge themselves on the moss and ferns that grow continuously under the endless sun, bulking up as much as possible in preparation for the long winter. When the sun sets for the final time they find a shelter, usually a mountain cave or log-jammed gulley to hunker down and sleep through the worst of the winter. Like bears they often wake and forage intermittently. They will also brood their eggs while hibernating, their coat and body protecting from the cold. The two above have woken early and get to witness the first dawn of spring.

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Dicynodonts are a very close #2 behind ceratopsids in my list of favorite old-dead-things, so I knew I was gonna have one for this prompt the moment I read it. Antarctica is still a giant question mark in terms of Mesozoic faunas. We can make inferences based on what taxa are found across Gondwana, but actual fossils from the continent itself are few and far between, most of which come from the islands around the Antarctic Peninsula. Lystrosaurus itself has been found there, and it was connected to Australia for much of the Mesozoic so those all sound like good reasons to play hypotheticals there.

Spec-Dinovember Day 23: Dino-mite, an ectoparasite of a Mesozoic host group

Sanguinornis minutus is an odd pengornithid. It has the largest teeth and is the smallest member of its family, both are in service of its specialized diet. S. minutus is a hematophage, feeding upon the blood of larger dinosaurs. Their primary hosts are hadrosaurs, but they are not picky. This lifestyle began with an ancestor opportunistically feeding upon the bugs and dead skin of the larger dinosaurs. Occasionally one would peck just a little too hard and break the skin only to find a protein packed liquid snack in the blood which issued forth. In removing existing parasites, these birds have become one of their ranks.

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So, this is obviously a play on vampire bats (Desmodus sp.), but cool thing is there are a handfull of extant birds that are blood feeders! vampire finches (Geospiza difficilis) are the closest to full-on obligate hematophages, but what I find really cool is oxpeckers (Buphagus sp.) are an extant example of the transition from parasite-cleaners to blood drinkers. I went with a pengornithid because there was a study that concluded their tail feathers were stiffened and thus they may have used them as a prop like woodpeckers do. The conclusions reached by that have been questioned and are currently regarded to be in error. But I figured it was as good a group of Mesozoic birds as any so I rolled with it. A tail prop would probably be helpful in holding onto the sides of a hadrosaur given how they tend to be tall and narrow bodied.

Spec-Dinovember Day 22: Parody, an incorrect/outdated reconstruction that turns out to be a real creature

The first fossils of Therizinosaurus to be found were the fragmentary remains of three massive claws. Uncertain of what kind of creature they belonged to, they were tentatively hypothesized to be from a large turtle-like reptile. Many further excavations revealed the therizinosaurs and segnosaurs to be the same animals, and that they were very odd theropod dinosaurs. However, a continent away and across the Tethys there would yet be a giant scythe-clawed turtle. Austrochitra maleevii is the largest member of the trionychidae family and one of the largest turtles, matching Archelon in dimensions but falling short in mass. Like the other giant turtles it is marine in habit, natively found within the shallow Eromanga Sea which covers much of Australia in the mid-Cretaceous. They are carnivorous and will attempt to eat just about anything they can catch. Much like their relatives they often wait buried in the seabed for prey to come close. also like their relatives they are capable of gas exchange via the vascularized oral tissue. They are rather swift swimmers if the need arises, occasionally pursuing prey for short bursts if their initial ambush misses. The large claws aid them in digging and tossing sand and mud over themselves when they hide, and in fending off potential predators or rivals. Their range is quite limited as their hunting method requires a loose sediment floor and comparatively shallow water depth. Occasional vagrants can be found out around the coasts of greater Australia, but no permanent populations have been able to establish themselves outside the Eromanga Sea.

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Not a dinosaur this time, but tangentially relevant. I dunno why, but it just felt like it had to be a softshell, and like the family is already named for having 3 claws so… it kinda fits. Australia is a long ways from the original Therizinosaurus locality, but I couldn’t just plop this thing back into the Nemegt fauna with how well sampled it is. So I done what I’ve been doing for all these and trying to think of times and places that are poorly represented. The inland sea has produced the most Mesozoic fossils from anywhere in Australia, but that’s just how scrappy most of the fossils of that time are there, so I went with it. Plus I’ve always just kinda had a soft spot for the dinosaurs of Down-Under ever since seeing the original Walking With Dinosaurs and reading Dinosaurs of Darkness (mine’s a 1st edition hardcover, but it appears this 2nd edition has a few new chapters at the end, cool!). Also I don’t know anything about turtles, so turtle experts how’d I do?