LIFE AND DEATH AT THE PERMO-TRIASSIC BOUNDARY Pelycosaur vs. Therapsid Jaw Dinocephalians Dicynodonts Theriodonts
Lewis, Walter, Coordinating Producer has reference to this Academic Journal, PHwiki organized this Journal LIFE AND DEATH AT THE PERMO-TRIASSIC BOUNDARY Pelycosaur in addition to Therapsid Evolution In their position on the family tree of life, the Pelycosaurs are the earliest in addition to most primitive members of the synapsids, the group that (in the old classification) leads to or (in the new classification) includes mammals. Thus the mammal-line split off from the rest of the reptile line (including turtles, lizards in addition to snakes, crocodiles, in addition to dinosaurs in addition to birds) very early. Pelycosaurs were abundant at low latitudes in early Permian, but disappeared by mid-Permian. At low latitudes, Diapsid Reptiles became important. At high latitudes, Therapsids (descendants of pelycosaurs) in addition to Anapsid Reptiles became important.
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Pelycosaur vs. Therapsid Jaw Although Therapsids resemble pelycosaurs in some ways, they had a much larger hole in the outer skull armor, flange on lower jaw as long as muscle attachment, in addition to shorter heads. All these differences from pelycosaurs are related to more elaborate chewing. In addition, some had a more upright posture. Dinocephalians Skeleton of the dinocephalian Moschops about 2,5 metres long, mounted in the American Museum, New York. The skull bones of this herbivorous reptile have undergone enormous thickening. Ulemosaurus svijagensis -Rjabinin, 1938- skull Therapsida: Dinocephalia: Tapinocephalidae Locality: Isheevo, Tatarstan, eastern European Russia Age: Late Permian, 255 million years ago Dinocephalians: most were large, with massive bodies in addition to thick skulls. They had a differentiated tooth row (incisors, canines, flattened back teeth). Some had bizarre horns (head-butting). Most were herbivores Dicynodonts Reconstruction of the Late Permian South African dicynodont Diictodon Dicynodonts: wide range of sizes (from rat- to cow-sized). They reduced all their teeth except the canines, in addition to probably had a horny pad as long as shearing food. They were very diverse herbivores, with many distinct modes of life, including some burrowers. Dicynodon trautscholdi – skull, Age: Late Permian
Theriodonts Theriodonts: Mostly active predators. They had longer legs, saber teeth, in addition to much more erect posture. Some were large, but other were small carnivores in addition to insectivores. Thrinaxodon Summary The fact that these animals were able to invade high latitudes, as well as the fact that they are the group from which mammals arose, raises questions about how they regulated their body temperature. Similarly, their upright posture raises questions about patterns of activity in addition to exercise. These issues will be discussed later in the context of dinosaur temperature regulation in addition to activity patterns.
The Paleozoic Marine Fauna Dominant animals: Articulate brachiopods, bryozoans, archaic corals, crinoids, cephalopods Dominant modes of life: Sessile, filter feeders extremely common. Mobile detritus feeders (Cambrian-style organisms) are still around. Mobile carnivores in addition to herbivores are more common. Free swimming in addition to burrowing animals still somewhat rare. Range: These organisms became important by end Ordovician, drop in importance after Permian. Some Example of Mid to Late Paleozoic Marine Fauna Articulate brachiopods Crinoids The Paleozoic Marine Fauna cont. Diversity: Many more groups trying each mode of life. Local communities have more species ~ 9 species in stressed zones, 18 in near shore zones, 30 in open marine regions Tiering: One important ecological feature of Paleozoic marine communities. Non-mobile, filter-feeding organisms are intercepting particles from the water column at different heights above the sediment-water interface. They are chopping up space vertically, kind of like l in addition to plants.
The End Permian Extinction The Paleozoic was marked by a series of major extinctions, including ones in the late Ordovician (takes out the Cambrian Fauna), the late Devonian (takes out armored fish) in addition to the late Permian (takes out almost everything). In this end Permian extinction, ~ 95% of marine species died. The End Permian Extinction cont. In the oceans: Trilobites in addition to Archaic corals gone as long as good. Brachiopods, bryozoans, crinoids, ammonoids (shelled cephalopods) hit very hard. Snails, clams, nautiloids (another type of shelled cephalopod) do ok. Absolutely no reefs known as long as the next 15 million years Stromatolites spread into “normal” environments as long as the first time since the Ordovician. On l in addition to : J ust 2 groups of therapsids survive. ~ 67% of the amphibians (including all reptile-like amphibians) go extinct. ~ 30% extinction of the orders of insects go extinct. What happened Asteroid or Comet Impact Volcanism Drop in sea Level Stagnant Ocean Hypotheses Drop in oxygen content of surface ocean water Belch of carbon dioxide from deep ocean
After the fall: the Triassic Recovery Recall that prior to the extinction, in the late Permian, l in addition to communities at high latitudes were dominated by a type of Synapsid Amniote, the Therapsids. After the extinction, it is a different story. Diapsid reptiles become increasingly important at all latitudes. There are two major groups of diapsids: 1. Lepidosaurs: Scaly Reptiles: first appear in the late Permian. Their shared novelties include a as long as ked tongue in addition to a as long as ked penis. Smallish lizard-like animals. Active insectivores in addition to carnivores. Ancestors of modern snakes in addition to lizards. 6000 living lepidosaur species. Lepidosaurs – Scaly Reptiles Tuatara from New Zeal in addition to
Their shared novelties include one hole in the head armor in front of the eye, in addition to teeth that are in separate sockets, rather than a long groove. When they first appear, they were also small lizard-like animals. In the Triassic, they diversify in spectacular fashion, in a series of pulses or waves 2. Archosaurs: Ruling Reptile: also first appear in the Permian. Archosaurs – Ruling Reptiles Early Archosaur (Dinosaur), Euparkeria The Three Waves of Triassic Archosaurs 1. Early Triassic: “Primitive” archosaurs 2. Middle Triassic: Crocodile-like archosaurs – Phytosaurids: – Crocodiles: – Aetosaurs – Rauisuchians: 3. Late Triassic: Dinosaurs in addition to Pterosaurs
Rhynchosaurs: Beaked lizard” Abundant pig-sized herbivores. Triangular head, large area as long as jaw muscles, beak, 2 tooth rows above, 1 row below, jaws close like a pocket knife, digging claws, sprawled gait. Primitive carnivorous archosaurs: medium-to-large (up to 2m), sprawling to semi-erect gait with limbs swung out to side. Aquatic in addition to terrestrial as long as ms. Cistecephalus – late Permian period Phytosauridae – “Plant lizard”: Rutiodon The Phytosaurs (this un as long as tunate name means “plant lizards”, because it was originally mistakenly believed that petrified.mud fillings in the jaw of the first specimen found were herbivore teeth) were crocodile-like semi-aquatic thecodonts that suddenly appeared in addition to became very abundant during the latter part of the Triassic period. Aetosaurs Aetosaurs were sizeable reptiles that grew to be one to five meters long, the average being about three meters (10 feet). Most aetosaurs possessed possessed a rather narrow crocodile-like body, although some had a broad turtle-like midsection, probably exp in addition to ed to contain a large fermenting gut. The animal was protected throughout by an armor covering over the neck in addition to the upper in addition to under surfaces of the trunk in addition to tail. Some species, such as Desmatosuchus, also had heavy spikes along the shoulders in addition to flanks. Based on their fossils in addition to the fact that they were herbivores, aetosaurs probably relied on their armor in addition to large size rather than speed to protect them from predators. Neoaetosauroides engaeus from the Upper Triassic
Rauisuchians SAUROSUCHUS “Lizard crocodile” Saurosuchus is not a dinosaur, but it shares Dinosaur World with other non-dinosaurs in addition to dinosaurs. With teeth like these, Saurosuchus is a meat-eater with a lot to smile about. Notice that these teeth are in various sizes in addition to degrees of wear. Throughout their lives meat-eaters replaced old, worn teeth, probably broken from biting into bone. Old meat-eaters most likely did not die of old age but of starvation, when their last set of teeth wore out.
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