#rhynchosaur

[knuppitalism-with-ue]

Results from the Flocking #paleostream!

Platycerabos, Mixosaurus, Tetrameryx and Hyperodapedon

[roygattero]

Ischigualasto series, alternate takes:

Hyperodapedon, acrylic painting, 2023}

(yes, I did this in a hurry)

[typhlonectes]

Unique dentition of rhynchosaurs and their two-phase success as herbivores in the Triassic

Thitiwoot Sethapanichsakul, Robert A. Coram, Michael J. Benton

Abstract

Rhynchosaurs were key herbivores over much of the world in the Middle and Late Triassic, often dominating their faunas ecologically, and much of their success may relate to their dentition. 

They show the unique ankylothecodont mode of tooth implantation, with deep roots embedded in the bone of the jaw and low crowns that were rapidly worn down in use. During growth, the main area of oral food processing, located in the middle and posterior portions of the occlusal surfaces of the jaws, moved posteriorly relative to the anterior tips of the jaws, which curved up. As the maxilla and dentary grew by addition of new bone posteriorly, the dental lamina fed in new teeth at the back of the tooth rows. 

CT scanning of the holotype skull of Bentonyx sidensis from the Middle Triassic of England reveals previously concealed details of the dentition. Together with new dentary material from the same location, this has enabled us to examine the tooth replacement process and elucidate ontogenetic changes in dentition and jaw morphology as the animals aged. 

There were major changes in rhynchosaur anatomy and function through their evolutionary history, with the early forms of the Middle Triassic dying out before or during the Carnian Pluvial Episode (233–232 Ma), and the subclade Hyperodapedontinae, with broad skulls and adaptations to chop tough vegetation, subsequently diversifying worldwide in a successful ecological expansion until their global extinction 227–225 Ma.

Read the paper here:

https://onlinelibrary.wiley.com/doi/10.1111/pala.12654

[alphynix]

Taking place during the 50-million year span between two huge mass extinctions, the Triassic was a very weird time. At the start of the period there was world domination by the synapsid Lystrosaurus, then after a few million years of recovery time came an evolutionary “explosion” from the rest of the survivors – filling new roles in their ecosystems and producing a brief but bizarre menagerie of unique species.

And one of the groups that rose to prominence during this time were the rhynchosaurs. Part of the archosauromorph branch of reptiles, they were closely related to the ancestors of crocodilians, pterosaurs, and dinosaurs, and evolved from small superficially lizard-like forms living in southern Africa during the very start of the Triassic, around 250 million years ago. But within just a few million years they became larger and bulkier, specialized for herbivory and scratch digging, and they soon spread all over Pangaea and became incredibly abundant in some fossil deposits.

Stenaulorhynchus stockleyi was one of larger member of this lineage, around 1.2m long (4’), known from Tanzania about 247-242 million years ago. It had a typical triangular rhynchosaurian skull, with wide deep cheeks supporting powerful jaw muscles and multiple rows of grinding teeth, along with a narrow hooked “beak” formed from the premaxillary bones of its snout.

Its unclear what the actual life appearance of the rhynchosaur “beak” was, with some reconstructions having a shrinkwrapped “alien mole-rat” look, others giving them keratinous parrot-like actual beaks, and still others going with fleshy tuatara-like lizard lips. In the past I’ve leaned somewhat towards the latter, but since one fossil does actually show some evidence for a keratinous covering I’ve gone for an extensive full beak this time around.

———

Nix Illustration | Tumblr | Pillowfort | Twitter | Patreon

[wtf-triassic]

Hyperodapedon

By @stolpergeist​

Etymology: Excess Pavement Tooth 

First Described By: Huxley, 1859 

Classification:  Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Deuterostomia, Chordata, Olfactores, Vertebrata, Craniata, Gnathostomata, Eugnathostomata, Osteichthyes, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiformes, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Crocopoda, Rhynchosauria, Rhynchosauridae, Hyperodapedontidae, Hyperodapedontinae 

Referred Species: H. gordoni, H. huenei, H. huxleyi, H. mariensis, H. sanjuanensis, H. stockleyi, H. tikiensis

Status: Extinct 

Time and Place: Between 231 and 227 million years ago, in the Carnian of the Late Triassic

Hyperodapedon is known from a variety of locations across Pangea, from the Ischigualsto Formation of Argentina, to the Wolfville Formation of Nova Scotia, to the Maleri Formation of India, the Lossiemouth Sandstone of Scotland, and the Pebbly Arkose Formation of Zimbabwe. In many ways, it safer to assume that Hyperodapedon was present in an environment in the late Carnian, than it is to assume it wasn’t.

Physical Description: Hyperodapedon was a typical rhynchosaur, stockily-built and low to the ground. The clade Rhynchosauria means “beaked reptiles”, because the front of their skulls had toothless prongs, or “beaks”. The back of the skull was very wide, but the beaked front region were very narrow. Hyperodapedon had an overbite; the front beak overhung the lower beak. Although traditionally restored exposed, this beak was likely covered up at least partially by lips when the mouth was closed. Also interestingly, the nares were conjoined and facing the front of the skull. Although this is very rare in reptiles, this is the condition in mammal skulls

Rhynchosaurs like Hyperodapedon did have teeth, but they were smaller and modified into broad, continuous chewing plates located at the back of skull. Said back of the skull had large openings indicative of powerful chewing muscles. The neck and tail were relatively short, and the spine was overall rather flexible. The limbs were short, semi-splayed, and powerful. Each foot had five digits. The entire body could grow up to 1.3 meters (4.2 feet) long.

Diet: Hyperodapedon was an herbivore; its diet likely consisted of tough but not hard plants such as seed ferms, ginkgos, cycads, and conifers. It would have also used its snout and powerful limbs to dig for roots and tubers.

Behavior: The amount of Hyperodapedon remains found gives us a look into its senses, musculature, and mobility. There’s a lot to go into; if you’re interested, Michael Benton wrote a huge monograph on it. Its large nares and eyes indicate it was diurnal and had a good sense of smell. Like modern snakes, it lacked tympanic ears, but could hear vibrations picked up through the ground. It had a powerful tongue and a shearing bite, that would have helped it cut up tough plant material.

Ecosystem: Hyperodapedon was an incredibly common small herbivore. As above, it’s safer to assume that Hyperodapedon was present in a Carnian environment than to assume it wasn’t. Across the globe Hyperodapedon would have regularly encountered early dinosaurs, pseudosuchians ranging from herbivorous aetosaurs to large predators like rauisuchians, early pterosaurs, other weird archosauromorphs, early lepidosaurs, dicynodonts, cynodonts, mammaliaforms, temnospondyls, and the occasional marine reptile that hauled itself onto land. This sounds like a quick overview of terrestrial Triassic fauna, but if a Hyperodapedon traveled from one end of Pangaea to the other, it wouldn’t have thought much of how the dinosaurs were slightly chunkier and differently-colored in this region. Its main concern would have been finding more chewy plants to eat.

Other: Rhynchosaurs were a super abundant group. In some places, they could make up to 60% of the vertebrate fauna! Then they went extinct before the end of the Triassic.

~ By Meig Dickson and Henry Thomas

Sources Under the Cut

Benton, M.J. 1983. The Triassic reptile Hyperodapedon from Elgin: functional morphology and relationships. Philosopical Transactions of the Royal Society of London B 302: 605-717.

Headden, J. 2012. Do Skulls Lie To Us? The Bite Stuff. https://qilong.wordpress.com/2012/09/27/do-skulls-lie-to-us/

Huxley, T. I. 1859. Postscriptum to Sir Rod. Murchison “On the Sandstones of Morayshire (Elgin, etc.) containing Reptilian Remains: Quartly Journal of the Geological Society XV: 435.  

Huxley, T. I. 1869. On Hyperodapedon. Quarterly Journal of the Geological Society 25: 138 - 152. 

http://fossilworks.org/?a=taxonInfo&taxon_no=38210 

[captainswaglord500]

Razortail/Pinetail/Chichilen

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Clade: Archosauromorpha

Clade: Crocopoda

Order: Rhynchosauria

Family: incertae sedis

Genus: Acanthocaudasaurus

Species: A. tahuretensis (“Tahureti spiny-tailed lizard”, “Tahureti” being a demonym for the historical region of Tahuret, a jungle and dry forest kingdom in northern Xenogaea)

Temporal range: Holocene to recent (10,000 kya - present); genetic divergence suggests a probable Miocene origin (10 mya - present).

Information:

A member of the rhynchosaur clade, this reptile’s placement within its own family is a contentious topic, in part due to its mix of basal and derived features. There are three competing theories regarding this, however: the first is that the razortail is a basal rhynchosaur which has convergently evolved derived rhynchosaur features (such as a partially beaked jaw), the second is that it is a derived rhynchosaur which has re-evolved several atavistic traits (such as the more slender, lizard-like build of earlier members of the clade), and the third and most widely-accepted theory being that it represents an early offshoot of the lineage leading to more derived forms, a so-called “missing link” between the two. Alas, this is not the only thing which makes this species quite unique compared to other members of its clade: an unusual example of an omnivore coming from an ancestrally herbivorous lineage, the razortail’s diet is best described as “indiscriminate”. Its main food sources consist largely of palm fronds, fallen fruits, nuts, seeds, large arthropods, small vertebrates (though it especially takes a liking for the multituberculates which share its habitat), and even eggs, the latter of which it actively seeks out. Individuals living in cities have been observed to even go after stray dogs and cats, as well as feral pigeons. Scavenging is also frequent, and cannibalism is documented but rare. Of course, with such indiscriminate dietary habits comes a high ecological pressure for competition, and as such, the razortail is fiercely territorial and reactive. However, while it extends such aggression towards its own kin mercilessly, rarely if ever tolerating the company of other razortails outside of its small hunting group, known as a caravan, with other animals, it is the embodiment of the phrase “its bark is worse than its bite”: it tends to flee from threats it does not believe it can successfully intimidate, though it may puff itself up and hiss and gurgle towards those it believes it can intimidate, throwing its spiny tail in front of it to add to the display. If approached or handled further, it may lunge forward, hissing and gurgling even more loudly, and will only bite if all else fails. The bite of this animal is deceptively strong, and can be strong enough to sever fingers and toes. That said, the amount of provocation it takes to get to this point is extreme, and to get bitten by this animal practically requires you to go looking to get bitten. Unfortunately, this animal often lives near human settlements, in part due to the easy source of food that is refuse piles and in part due to its acquired liking for coconuts and bananas, crops imported during medieval times by Austronesian sailors. As such, its relationship with the native inhabitants of the region is complicated, being simultaneously valued for its prowess for hunting the multituberculates and rodents which commonly eat crops but also detested or its own proclivity towards eating these crops itself. 

Despite being only around the size of a Komodo dragon, this animal’s reputation far precedes it in the jungles and dry forests (and increasingly the neighboring grasslands) it calls home: this animal’s tendency to square up against significantly larger troodonts, dromaeosaurs, and even hyaenodonts has earned it the moniker of the “bulldog lizard” in some areas. Alas, this animal also squares up against rauisuchids and medium-sized theropods. So reviled is this creature by the animals it shares its ecosystem with, that dinosaurs which have lost chicks to razortails will abandon entire nests and start anew. Nonetheless, this animal is also preyed upon by the most brazen predators, its catalogue of predators including large theropods, amphicyonids, saber-toothed cats, prestosuchids, phytosaurs, hyaenids, hyaenodonts, oxyaenodonts, marsupial lions, sparassodonts, and humans. As such, this animal’s mottled, vibrant green and brown coloration is an adaptation which allows it to blend in with the foliage of its home. Another unique adaptation this animal has is its metabolism: a rare example of a heterothermic non-archosaurian diapsid, the razortail is able to inefficiently moderate its own internal temperature. However, as this is energetically costly, it typically relies on the surrounding environment to regulate its body temperature. With superb eyesight, the razortail is cathemeral and is able to be active in both the high afternoon sun and the pitch black of the midnight, hauling itself into the trees with its powerful forelimbs to sleep in the branches when not foraging or socializing. Able to run at speeds of up to 30 mph, this animal is also well-adapted for running fast in short bursts, something which aids it both in hunting and in fleeing from predators. This species appears to be uniquely resistant to the venom of many hymenopterans and snakes, the venom only knocking it unconscious for an hour or two before being metabolized. As such, it has little if any issue feeding on the nests of bees and wasps and is one of the few animals which control venomous snake populations. Some evidence suggest it engages in a form of commensalism with some species of therocephalians living in the same region as it, the more endothermic and muscular therocephalians serving as the brute force needed to make the kill while the razortails serve as the speed needed to corral prey into waiting jaws. This animal is quite versatile as well, and can regenerate damaged body parts with ease, even being able to regenerate parts of its eye if damaged. This species is one of the most successful in Xenogaea from a conservation standpoint, numbering nearly 2 million animals and counting, and its adaptability has allowed it to colonize previously uncharted territory for its species over a relatively short period of time, with most evidence pointing towards this species undergoing a distributive radiation. Likewise, this species’ presence in its native range is likely vital to the spread of the Xenogaean jungle pine, an araucarian conifer species found throughout the northern stretches of the Isle of Perils, as the razortail eats the cone by first crushing them before consuming them, spreading a few stray seeds on the ground in the process and allowing others to pass through its bowels to be excreted in its urea. Another thing to note about this bizarre creature is that the teeth at the front of the lower lip are fused into an exposed, bony plate whereas those on the top are concealed by lips.

In the winter months, when the tropical air is cooler, these animals are one of the few to make love. Congregating in massive groups, the males, whose hormones turn their throat pouches a vibrant blue and red during the mating season, are drawn in by the pungent pheromones the female produces, which are often described as having a strong mushroom-like smell. Though the female will mate with as many males as possible to ensure the fitness of her clutch, males will still fight one another for mating rights. Mating usually occurs on the ground, but maybe also occur in the trees, and the males will usually bite down gently on the back of the female’s neck to prevent her from struggling during copulation. After the female has mated with as many viable males as possible, she will chase away any other suitors aggressively. In a few weeks, she will lay a clutch of 20-30 leathery-shelled eggs in a small burrow at the foot of a tree, which she will guard ferociously, continuously adding and removing dirt as needed and only leaving the burrow for short periods to eat and drink, something which is risky, given that other razortails might eat her clutch. Sex determination is based on temperature, with the colder eggs producing males and the warmer eggs producing females. In roughly 5 weeks, the eggs will hatch and the young are cared for by the mother for roughly a year, after which they are big enough to fend for themselves. Full size is reached at 5 years old and sexually maturity at 7 years old, and in the wild, the young may live to nearly 20-25 years old, whereas in captivity, they may live as long as 30-40 years old. Homosexual behavior is extensively documented in this species, with both males and females engaging in same-sexual copulatory behaviors such as mounting. In fact, an estimated 50% of razortail sexual encounters are same-sex. 

As touched on earlier, this species has a long and highly-complicated relationship with the native inhabitants of the region: simultaneously treated as a savior from pest animals which feed on cash crops and as a nuisance for feeding on said crops itself, captive-bred razortails appear to be undergoing a form of domestication, the first instance of true domestication ever being documented in a nonavian and non-archosaurian reptile. These captive-bred razortails are stockier, have larger eyes, and appear to be undergoing greater encephalization than their wild-born cousins. In captivity, they are used as pest control and guard dogs, their aggression deterring large predators and humans looking to do harm alike. However, its tendency to see other domesticated animals as potential prey make it extremely difficult to keep in close quarters with other pets, especially birds and rodents. Hence, most house-trained razortails are either kept alone, kept with a companion, or sleep outside. Captive-bred specimens are often given a very diverse diet, with the most highly-recommended diet consisting of mice, fish, crab (used as a substitute for the giant invertebrates it normally hunts), lettuce, celery, tomato, avocado, mango, peanuts, bananas, and strawberries. Likewise, this species is exceptionally emotionally intelligent, forming a similar level of emotional connection to its caretakers as dogs, chirping, grumbling, and rumbling to convey happiness to its owner. Its flesh is variously considered a delicacy in some areas, its taste supposedly being gamey and not unlike goat meat. That said, it is tough and sinewy, which makes it difficult to cook properly. Though fossils of this species are quite young, only going back to the very beginning of the Holocene around 10,000 years ago, genetic divergence when comparing its genetic sequence to close relatives indicates its lineage likely originated around 10 millions years ago in the Miocene.

[dragonfelling]

Hyperodapedon. Plentiful and Cursed looking

Please be nice to him

[paleofan]

Teyumbaita sulcognathus from the Late Triassic of Brazil. Rhynchosaurs were perhaps the rodents of the Late Triassic period. This is not a dinosaur, folks! #rhynchosaur #dinosaurs #triassic #paleoart #paleontology #fossil #caturrita https://www.instagram.com/p/Bv8Y_07AL40/?utm_source=ig_tumblr_share&igshid=y5xk1urnxtvz