#therocephalia

[alphynix]

Therocephalians were a group of synapsids very closely related to – or possibly even ancestral to – the lineage leading to modern mammals. They were a diverse and successful group of carnivores during the latter half of the Permian, but suffered massively during the "Great Dying" mass extinction, with only a handful of representatives making it a few million years into the Triassic.

Tetracynodon darti was one of these rare Triassic therocephalian survivors, living in what is now South Africa around 251 million years ago. Only about 25cm long (~10"), it had slender limbs and strong claws that suggest it was a scratch-digger. Its long snout was lined with pointed teeth, and it was probably an active predator hunting by snapping its jaws at fast-moving prey like insects and smaller vertebrates.

Its combination of small size, burrow-digging habits, and unspecialized diet may be the reason it scraped through the Great Dying when most of its relatives didn't – but unfortunately it seems to have been a "dead clade walking", disappearing only a short way into early Triassic deposits.

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References:

Fontanarrosa, Gabriela, et al. "The manus of Tetracynodon (Therapsida: Therocephalia) provides evidence for survival strategies following the Permo-Triassic extinction." Journal of Vertebrate Paleontology 38.4 (2018): 1-13. https://doi.org/10.1080/02724634.2018.1491404

Sigurdsen, Trond, et al. "Reassessment of the morphology and paleobiology of the therocephalian Tetracynodon darti (Therapsida), and the phylogenetic relationships of Baurioidea." Journal of Vertebrate Paleontology 32.5 (2012): 1113-1134. https://www.researchgate.net/publication/254315180_Reassessment_of_the_Morphology_and_Paleobiology_of_the_Therocephalian_Tetracynodon_Darti_Therapsida_And_The_Phylogenetic_Relationships_of_Baurioidea

Wikipedia contributors. “Tetracynodon” Wikipedia, 21 Aug. 2024, https://en.wikipedia.org/wiki/Tetracynodon

Wikipedia contributors. “Therocephalia” Wikipedia, 01 Oct. 2024, https://en.wikipedia.org/wiki/Therocephalia

[quark-nova]

By "as it currently is", you mean the crownwards tree with Biarmosuchia, the ugly ones, Anomodontia, Gorgonopsia, Therocephalia and Cynodontia in that order?

Don’t get too comfortable with therapsid phylogeny as it currently is, btw

[quark-nova]

Actual tier list of therapsids by cuteness because I'm bored

1. Cynodontia

Despite my love for dicynodonts, nope, I didn't forget two letters here. Cynodonts exist on a sliding scale of "good doggo" to "rat!!!", and they're honestly quite aww-worthy.

2. Therocephalia

Cynodontia's more experimental cousins. Quite a lot of variation, ranging from the adorable to the more badass than cute.

3. Dicynodontia

Geikia is absolutely adorable, and so are the Diictodon from Primeval. Some forms are definitely not as cute - although even some of the megafaunal ones are quite huggable. Still my favourite Permian piglets.

4. Biarmosuchia

Sleeker-looking than gorgonopsians, although still more on the cool than cute side. Nevertheless, these primitive therapsids already nailed down the group's most memorable looks.

5. Gorgonopsia

Powerful? Yes. Majestic? Definitely. Awe-inspiring? Absolutely. Cute? Only when reconstructed with lips and fur.

6. Anomodontia

The little tree climber Suminia is honestly extremely cool, but the teeth definitely weird me out. So much that they gave the group its name, in fact.

7. Dinocephalia

Estemmenosuchus alone - by mere virtue of being interesting to look at - is preventing the basal group from falling further. Couldn't stop their heads, unfortunately - the weird downward-facing trend is already present.

8. Anteosauria

The answer to the head problem is not "a bigger, meaner-looking head". They don't even have the majesty of gorgonopsians, just the look of unrefined brutes preying on their kin.

9. Tapinocephalia

Seriously. These smooth, downward-sloped heads will never stop being creepy to look at. Please spare the existential horror, Moschops.

[extinctworld-ua]

Ericiolacerta

Ericiolacerta — монотипічний рід тероцефалів родини ериціолацертових (Ericiolacertidae), що походить з раннього тріасу Африки та Антарктики. Єдиний встановлений вид – Ericiolacerta parva. Описаний Д. Вотсоном (David Meredith Seares Watson) у 1931 році. Назва означає – «ящірка-їжак».

Повний текст на сайті "Вимерлий світ":

https://extinctworld.in.ua/ericiolacerta/

[wtf-triassic]

Olivierosuchus parringtoni

By Ripley Cook

Etymology: Crocodile from Oliviershoek Pass

First Described By: Brink, 1965

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, Synapsida, Eupelycosauria, Metopophora, Haptodontiformes, Sphenacomorpha, Sphenacodontia, Pantherapsida, Sphenacodontoidea, Therapsida, Eutherapsida, Neotherapsida, Theriodontia, Eutheriodontia, Therocephalia, Scylacosauria, Eutherocephalia, Akidnognathidae

Status: Extinct

Time and Place: Olivierosuchus lived 251 to 249 million years ago, in the Olenekian of the Early Triassic.

Olivierosuchus is only known from South Africa.

Physical Description: I feel like most of you would look at Olivierosuchus and think “that’s a good pupper”. Olivierosuchus had a fairly long snout that was slightly wider than deep. The snout has a slight upwards bend and has small pits that indicate the presence of whiskers. It had three types of teeth: average-sized incisors, a pair of large canine teeth, and small teeth in the back of the jaw. The body was low-slung and may have had semi-sprawling forelimbs. Its forelimbs were robust and were likely adapted for digging. Olivierosuchus had whiskers, and may have had a more extensive covering of fur.

Before you ask - Olivierosuchus was not venomous like has been suggested for its relative Euchambersia. Its teeth do not have grooves for spreading venom.

Diet: Olivierosuchus was carnivorous, and fed on smaller animals like parareptiles and the young of other synapsids.

Behavior: First - burrows can preserve in the fossil record, and it’s really interesting. Such as one large, wide burrow preserved in early Triassic rocks from South Africa. Interestingly, this burrow has the skeleton of a juvenile Lystrosaurus inside. The Lystrosaurus was too small to dig the burrow, but it’s the perfect size for something like Olivierosuchus. So an Olivierosuchus probably lived in the burrow, and brought back a dead Lystrosaurus juvenile as food. The back teeth of therocephalians suggests they may have been able to chew their food a bit before swallowing it. This is in contrast to gorgonopsians, which were forced to tear off swallowable chunks of food.

Ecosystem: Olivierosuchus lived alongside Lystrosaurus, because of course it did, everything alive at the beginning of the Triassic lived alongside Lystrosaurus. In fact the specific rock layer it was found in - which was deposited immediately after the Permian-Triassic Extinction - is called the Lystrosaurus Assemblage Zone. The environment was arid and not exactly lush, because of the extinction that just happened. The biostratigraphy of the Lystrosaurus Assemblage Zone is well-mapped enough that we know which therocephalians lived at exactly the same time as Olivierosuchus: those being Moscorhinus, “Tetracynodon” darti, Ericolacerta, Regisaurus, and Zorillodontops. The Lystrosaurus Assemblage Zone is also known for lots of Procolophon and Sauropareion, as well as cynodonts such as Thrinaxodon and Galesaurus. Early archosaurs are also known, such as Prolacerta and Proterosuchus, as well as temnospondyls like Broomistega and Lydekkerina.

Other: Olivierosuchus was originally named Olivieria by A.S. Brink in 1965. It was renamed Olivierosuchus in 2002 by Christian Kammerer and Christian Sidor, because Olivieria was already taken by a fly.

~ By Henry Thomas

Sources under the cut

Brink, A.S. 1965. A new Ictidosuchid (Scaloposauria) from the Lystrosaurus-Zone. Palaeontologia Africana 9: 129-138.

Kammerer, C.F., Sidor, C.A. 2002. Replacement names for the therapsid genera Criocephalus Broom 1928 and Olivieria Brink 1965. Palaeontologia Africana 38: 71-72.

Botha-Brink, J., Modesto, S.P. 2011. A new skeleton of the therocephalian synapsid Olivierosuchus parringtoni from the Lower Triassic South African Karoo Basin. Palaeontology 54(3): 591-606.

Modesto, S.P., Botha-Brink, J. 2010. A burrow cast with Lystrosaurus skeletal remains from the Lower Triassic of South Africa. Palaios 25(4): 274-281.

[nevver]

Therocephalia, Cristian Girotto

[thisisnthappiness]

Therocephalia, Cristian Girotto

[alphynix]

The synapsids were an incredibly successful and diverse group during the Permian period, but after the devastating "Great Dying" mass extinction event 252 million years ago only three lineages survived into the Triassic – the cynodonts (close relatives and ancestors of modern mammals), the dicynodonts (beaked tusked weirdos who briefly took over the world), and the therocephalians.

Therocephalians were close relatives of cynodonts, and convergently evolved several very mammal-like anatomical features in their skulls, teeth, and limbs. But unlike their cousins this lineage never fully recovered in the Triassic, and they ultimately disappeared completely around 242 million years ago.

Ericiolacerta parva was one of these short-lived Mesozoic therocephalians, known from the early Triassic (~252-247 million years ago) of South Africa and Antarctica, in regions that were connected at the time as part of the supercontinent of Pangaea. It was a fairly small animal, about 20cm long (~8"), with small sharp teeth that indicate it mainly fed on insects, and semi-opposable thumbs and inner toes that suggest it was also a capable climber.

Holes in the bones of its snout would have carried numerous nerves and blood vessels, which may be evidence of sensitive fleshy lips and possibly whiskers. And while there's no direct evidence of fur in therocephalians, they do appear to have been active warm-blooded animals – and possible fossilized synapsid hair from the Permian period suggests fuzziness might have been ancestral to all of the "protomammal" lineages that survived into the Triassic.

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[alphynix]

If there's any equivalent to carcinization in mammals, it's turning into an otter-beaver-like semi-aquatic form.

Because it just keeps happening.

Modern examples alone include otters, beavers, muskrats, giant otter shrews, desmans, aquatic genets, yapoks, lutrine opossums, and platypuses – and in the fossil record there were early pinnipeds, remingtonocetids, pantolestids, stagodontids, and Liaoconodon going as far back as the early Cretaceous. Even outside of the true mammals there were also Castorocauda, Haldanodon, and Kayentatherium during the Jurassic, and much further back in the late Permian there was the early cynodont Procynosuchus.

So a non-cynodont synapsid doing the exact same thing really isn't all that surprising.

Perplexisaurus foveatus was a member of the therocephalians, a group of synapsids that were close evolutionary "cousins" of the cynodonts-and-true-mammals lineage. Similar in size to a modern rat, about 20cm long (8"), it lived in Western Russia during the Late Permian about 268-265 million years ago.

At the time this region was a river plain with a tropical climate, experiencing seasonal floods that turned the whole area into what's known as "viesses" (a name based on the abbreviation "V.S.S." standing for "very shallow sea"), vast shallow lake-seas that persisted for weeks or months at a time.

So this little animal has been interpreted as being semi-aquatic, swimming around and feeding on aquatic invertebrates and tiny fish and amphibians. Its skull had numerous pits around the front of its face, suggesting that it had a highly sensitive snout – probably whiskery, allowing it to hunt entirely by touch in dark murky water, but it's also been proposed to have possibly had an electroreceptive sense similar to modern platypuses.

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Nix Illustration | Tumblr | Pillowfort | Twitter | Patreon

[extinctworld-ua]

Megawhaitsia

Megawhaitsia — рід гігантських тероцефалів з родини вайтсіїд (Whaitsiidae), відомий за фрагментами правої верхньощелепної кістки з відкладень верхнього перму з території Володимирської (місцезнаходження «В’язники-2») та Нижньогородської області (місцезнаходження «Пурли»). Єдиний встановлений вид – Megawhaitsia patrichae, що був описаний в 2008 році.

Повний текст на сайті "Вимерлий світ":

https://extinctworld.in.ua/megawhaitsia/

[alphynix]

Weird Heads Month #30: Lumpy-Faced Synapsids

Among the synapsids ("proto-mammals"), head ornamentation evolved multiple times in the therapsids, from basal members of the group like Tetraceratops, burnetiamorphs, and dinocephalians to later lineages like dicynodonts and gorgonopsids.

But these sorts of structures don't seem to have really ever developed in one of the lineages most closely related to the ancestors of modern mammals, a group known as therocephalians.

…With the exception of Choerosaurus dejageri.

Living in South Africa during the late Permian, around 259-254 million years ago, this small synapsid was only about 35cm long (1'2") but sported some large bulging bony bosses on the sides of both its snout and lower jaw.

The bosses would have been covered by tough skin in life, similar to modern giraffid ossicones.

A study of Choerosaurus' skull found that its head was rather delicately built, and the bosses were relatively fragile and lacked the sort of reinforcement needed to resist impacts, suggesting that these structures weren't used as weapons for fighting each other but were probably more for display – so they may even have been brightly colored.

The upper jaw bosses were also well-supplied with nerves and blood vessels, and would have been quite sensitive to touch.

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