In North America 1. the Triassic is represented by the thick Newark Group along the east coast, 2. by widespread red-bed and fluvial sediments in the

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1 The Triassic System The name Triassic derives from the three parts into which the Triassic is divided on the European platform: 3. Keuper (highest) 2. Muschelkalk 1. Bunter (lowest)

2 In North America 1. the Triassic is represented by the thick Newark Group along the east coast, 2. by widespread red-bed and fluvial sediments in the Great Plains, 3. and by marine sediments in scattered basins in the western states.

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4 Land Reptiles Reptiles first invaded the sea during the Triassic System archosaur A reptile having a diapsid skull type with teeth set in sockets. This group includes the crocodiles, pterosaurs, dinosaurs, and birds.

5 Ginkgophyta Gaining importance, but not dominance were the, dioecious plants of which Ginkgo biloba is the only extant genus and species. The pollen is borne on catkinlike structures [a catkin is a type of inflorescence (cluster of flowers on a common stalk) in which the flowers are attached directly to the common stalk without an individual stem]. The ovules, in pairs, are borne on stalks and form seeds upon pollination and fertilization. These re-productive organs are intermediate between

6 Marine Vertebrates plesiosaur: A Mesozoic marine reptile with a euryapsid skull type, abroad body, and large, and paddle like limbs. Ichthyosaur (literally "fish lizards"): A Mesozoic marine reptile with a dolphin like body.

7 The Plants The dominant Triassic land plants were the Cycadales CYCADALES: a class of Cycadophyta that had evolved from the Lycopodiophyta in Late Permian time. The Cycadales, in contrast to the Lycopodiophyta, have specialized pollen and seed cones (strobili) that are borne on different plants (they are, therefore, dioecious). The ovules are borne on the scales of female cones (as in Coniferophyta). In gross appearance the cycads resemble palm trees, with a bulbous or columnar trunk and a crown offronds on top. Heights range from 1 to 18 m.

8 The Triassic Plants The dominant Triassic land plants were the Cycadales, a class of Cycadophyta that had evolved from the Lycopodiophyta in Late Permian time. The Cycadales, in contrast to the Lycopodiophyta, have specialized pollen and seed cones (strobili) that are borne on different plants (they are, therefore, dioecious). The ovules are borne on the scales of female cones (as in Coniferophyta). In gross appearance the cycads resemble palm trees, with a bulbous or columnar trunk and a crown of fronds on top. Heights range from 1 to 18 m

9 The Triassic Plants: Ginkgo Gaining importance, but not dominance, were the Ginkgophyta, dioecious plants of which Ginkgo biloba is the only extant genus and species. The pollen is borne on catkin like structures [a catkin is a type of inflorescence (cluster of flowers on a common stalk) in which the flowers are attached directly to the common stalk without an individual stem].

10 Triassic Plants The Cycadeoidales (Bennettitales) are an extinct (Triassic-Cretaceous) class of plants that were common in the Mesozoic forests. They closely resembled the Cycad ales in the shapes of their leaves and trunks. They had, however, stalked fruiting structures containing both pollen and seeds and resembling primitive flowers. The Angiospermophyta (flowering plants) may have evolved from this group (Cretaceous).

11 The Reptiles In Early Triassic time a remarkable group of reptiles, the thecodonts, evolved, of which Euparkeria is a typical example. Euparkeria evidently was built for running.

12 The Reptiles

13 The Reptiles: Thecodonts During the Triassic, the thecodonts evolved into the saurischian and ornithischian dinosaurs. Both groups appeared in Late Triassic time.

14 Classification and characteristics of dinosaurs Order Saurischia Suborder Sauropodomorpha: partly bipedal in Late Triassic, evolving into large, quadrupedal, herbivorous types in the Jurassic and Cretaceous [e.g., Aptosaurus and Diplodocus (Fig. 23.5A), Late Jurassic] Suborder Therapoda: fully bipedal, carnivorous [e.g.. Tyrannosaurus (Fig ), Late Cretaceousl Order Ornithischia Suborder Ornithopod a: bipedal [e.g., Camptosaurus (Fig. 23.6A). Late Jurassic to Early Cretaceous] Suborder Stegosauria: bipedal/quadrupedal, with a double row of plates along the back (vascularized heat-exchange devices?) and horns on the tail [e.g.. Stegosaurus (Fig ), Late Jurassic] Suborder Ankylosauria: quadrupedal, with bony plates on back (e.g., Anky/osaurus. Late Cretaceous) Suborder Ceratopsia: horned dinosaurs [e.g., Triceratops (Fig. 23.6C). Late Cretaceous)

15 Other important groups of reptiles that evolved in the Triassic are: the lizards (Lacertilia, Early Triassic-Holocene), the snakes (Serpentes, early Triassic-Holocene), the crocodiles (Crocodylia, Late Triassic-Holocene), the turtles (Chelonia, Late Triassic-Holocene) and the marine reptiles (Ichthyosauria and Plesiosauria, Early Triassic-Late Cretaceous). The turtles are a "primitive" group of reptiles (i.e., they have not evolved much since they first appeared). Most species were and are freshwater dwellers (rivers, lakes, marshes), but some have become adapted to land (the tortoises, Eocene-Holocene), and others became fully marine (Chelonidae, Dermochelyidae: Late Cretaceous-Holocene).

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17 Early dinosaurs, including Rioarribasaurus, were relatively small, sleek predators. This skeleton is from Triassic rocks of New Mexico. Rioarribasaurus

18 Two types of synapsids are known from Triassic strata Primitive synapsids (or "mammal-like reptiles) persisted from the Late Paleozoic. Mammals, represented first by a group called the multituberculates, appeared in the Late Triassic.