diadectes

Suggested sketch by armaknee : A plethora of Squamozoic concepts and amphibians from an earth covered 90% in water (I’m sure you remember that concept of mine)

Yep, I remember :) Here are three animals from such a world; a lurking, armored estuarine form that works like an ecological crossover between a turtle and a crocodile, an amphibian equivalent of an ichthyosaur (but with gills,) and a big, semi-terrestrial herbivore.

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Diadectes

Localización: América del Norte.

Periodo: Pérmico Inferior.

Tamaño: 3 metros de longitud.

Alimentación: Herbívoro.

Peso: Hasta 300 kg.

Diadectes era un anfibio gigante estrechamente emparentado con los reptiles que vivió a principios del período Pérmico, cuando la Tierra sufrió un período de congelación que ocasionó que el ambiente se tornara más seco y frío que en el Carbonífero. Los niveles de oxígeno descendieron y los anfibios comenzaron a perder la supremacía, que fue ganada por los reptiles. En esa época surgieron nuevos tipos de anfibios más resistentes al cambio climático que se había ocasionado, fruto de ello surgieron especies como Diadectes, uno de los primeros anfibios herbívoros. Los fósiles de Diadectes han sido encontrados en la actual Texas, en Estados Unidos, una zona que en aquella época era semi desértica como consecuencia del enfriamiento en los polos. Diadectes se alimentaba de helechos bajos, puesto que no podía subir a los árboles debido a su peso. Muy posiblemente viviera en pequeñas manadas para protegerse de los depredadores, puesto que era un animal pesado y lento.

Permian scene

During the Permian, the Earth bakes and desiccates. Seas dry into deserts that drift across Pangea, leaving just pockets of green where lakes pool and streams list beneath Dawn World forests. Here amphibians float and meander, scuttle in the mud, and feed on fish and worms, or skulk in the underbrush to munch on vegetables and bugs. Diplocaulus, Diadectes, Eryops—their names sound like how they move, waddling, undulating, bobbing. There’s still some tadpole in them. 

Eryops is like a mammoth frog, though the fat tail, squat legs, and scalpel teeth suggest crocodile. It’s too big to breathe through its skin, so throat pouches balloon and deflate under its chin. It likes to pull millipedes from the leaf litter or corner fat fish in the shallows. Eryops is a bully. 

But bullies are not immune to the food chain. Orthacanthus swims here too. It’s eel-like, with twin-forked teeth—not an amphibian, but a freshwater shark whose reign as apex predator lasts 175 million years, from the Devonian to the Carboniferous to the Permian, where it slithers after Eryops who have grown too relaxed, too careless, then snags them with its mouthful of fishhooks. The prongs tear flesh messily, turn meat into uneven ribbons. The shark’s prey chokes, writhes, tries to swim away, but fails, bleeds out, dies. Orthacanthus feeds until it cannot. Then the others come—other amphibians, once-bullied lobe-finned fish, swimming insects, even late summer pollywogs—and dine until the Eryops is just a clatter of bones tangled among the weeds and fallen trees of the desert-fenced bayou. 

The crosswise biter, Diadectes (1878)

Phylum : Chordata
Class : Amphibia
Order : Reptiliomorpha
Suborder : Diadectomorpha
Family : Diadectidae
Genus : Diadectes
Species : D. lentus, D. sideropelicus, D. tenuitectus, D. carinatus, D. sanmiguelensis, D. absitus

  • Permian (290 - 272 Ma)
  • 3 m long and 80 kg (size)
  • Texas, United States (map)

It possesses some characteristics of reptilians and amphibians, combining a reptile-like skeleton with a more primitive, seymouriamorph-like skull. Diadectes has been classified as belonging to the sister group of the amniotes.

Among its primitive features, Diadectes has a large otic notch (a feature found in all labyrinthodonts, but not in reptiles) with an ossified tympanum. At the same time its teeth show advanced specialisations for an herbivorous diet that are not found in any other type of early Permian animal. The eight front teeth are spatulate and peg-like, and served as incisors that were used to nip off mouthfuls of vegetation. The broad, blunt cheek teeth show extensive wear associated with occlusion, and would have functioned as molars, grinding up the food. It also had a partial secondary palate, which meant it could chew its food and breathe at the same time, something many even more advanced reptiles were unable to do.

These traits are likely adaptations related to the animals’ high-fiber herbivorous diet, and evolved independently of similar traits seen in some reptilian groups. Many of the reptile-like details of the post-cranial skeleton are possibly related to carrying the substantial trunk, these may be independently derived traits on Diadectes and their relatives. Though very similar, they would be anaologous rather than homologous to those of early amniotes like pelycosaurs and pareiasaurs, as the first reptiles evolved from small, swamp dwelling animals like Casineria and Westlothiana.

Diadectes was first named and described by the American paleontologist Edward Drinker Cope in 1878, based on part of a lower jaw (AMNH 4360) from the Permian of Texas. Cope noted: “Teeth with short and much compressed crowns, whose long axis is transverse to that of the jaws,” the feature expressed in the generic name Diadectes “crosswise biter” (from Greek dia “crosswise” + Greek dēktēs “biter”). He described the animal as “in all probability, herbivorous.” Cope’s Neo-Latin type species name sideropelicus (from Greek sidēros “iron” + Greek pēlos “clay” + -ikos) “of iron clay” alluded to the Wichita beds in Texas, where the fossil was found. Diadectes fossil remains are known from a number of locations across North America, especially the Texas Red Beds (Wichita and Clear Fork).

Dimetrodon, Ely Kish

The rain tapped on the forest’s leaves and left no room for other sounds. It spattered on Diadectes’ body and dripped into the mud. The damp smell of earth was everywhere. Mold was blooming. Somewhere in the distance small amphibians were chirping. Diadectes swayed between sleepiness and anxiety. The rain made it difficult to detect predators, and the sun had never broken through the clouds to warm the body.

This was Dimetrodon’s advantage. It slid silently from the vegetation like a grotesque ghost, emerging from the green to clamp toothy jaws on Diadectes’ hind leg. With a violent jerk, Dimetrodon flipped its prey to its side. The big amphibian emitted a pained whine and batted Dimetrodon’s side with its forefeet, punching the predator, trying to push away. But Diadectes was weak, tired, unable to wrestle free from Dimetrodon’s bite.

Blood pulsed from the wounds and mixed with the puddles on the forest floor. Dimetrodon held fast, waiting patiently for Diadectes to lose all its strength. Then the predator could feed.