Lecture 09 Handout PDF

14/10/2012 Lecture 10 Tetrapods Part 3: Pterosaurs, Dinosaurs and relatives Vertebrate phylogenetic tree Eusthenopteron Panderichthys Tiktaalik Acanthostega...

14/10/2012 Lecture 10 Tetrapods Part 3: Pterosaurs, Dinosaurs and relatives Vertebrate phylogenetic tree Eusthenopteron Panderichthys Tiktaalik Acanthostega Ichthystega Balanerpeton Lissamphibia Caecilians Urodeles Tetrapoda Anurans 1 Synapsids Lepidosauromorpha Amniotic egg, able to be fully terrestrial Turtles Amniotes Squamates Diaspids Tuatara Archeosauromorpha 1  14/10/2012 Permian Triassic Jurassic Cretaceous Cenozoic Squamates Tuatara Lepidosauromorpha Mosasaurs Plesiosaurs ? Ichthyosaurs Marine Diapsids ? Thalatosaurs Champsosaurs Archosauromorpha Trilophosaurs Archosaurs Permian Triassic Jurassic Cretaceous Lepidosauromorpha Crocodilians Pterosauria Archosauria Dinosauria 2  14/10/2012 5) Diapsids Pelagosaurus d) Crocodilians Anatosuchus Mahajangasuchus Gharial Alligator Crocodile Sarcosuchus 3  14/10/2012 Permian Triassic Jurassic Cretaceous Lepidosauromorpha Crocodilians Pterosauria Archosauria Dinosauria 5) Diapsids e) Pterosaurs These were the first reptile group able to achieve true flight. They are closely related to dinosaurs The earliest pterosaur fossils are from the late Triassic, but are already fully adapted for flight. As yet we know of no transitional forms leading up to Pterosaurs. A likely possibility is that the transitional forms leading to Pterosaurs were able to glide but not capable of flight. We see multiple independent origins of gliding species of diapsids. 4  14/10/2012 i) Convergent evolution Carbon. Permian Triassic Jurassic Cretaceous Cenozoic of gliding Diapsids Turtles Turtles ? Draco Lizard Squamates Tuatara Plesiosaurs Ichthyosaurs Champsosaurs Shavovipteryx Archosaurs including Pterosaurs Shavovipteryx 5) Diapsids e) Pterosaurs A likely possibility is that the transitional forms leading to Pterosaurs were able to glide, but not capable of flight. We see multiple independent origins of gliding species of diapsids. The gliding Shavovipteryx like Pterosaurs had a membrane between its hind limbs and tail and possible also to its forelimbs. This genus has been proposed to be the ancestor or a close relative of Pterosaurs, but morphological phylogenies suggest it probably represents an independent evolution of gliding. Still it seams likely that Pterosaurs probably evolved from a similar transitional form. Shavovipteryx 5  14/10/2012 5) Diapsids e) Pterosaurs i) Adaptations for flight lightly built skeletons with air spaces in many bones. Bird bones likewise are hallow. Hollow bird bones with struts for support Hollow pterosaur bone with crossed ridges lining the interior surfaces 5) Diapsids e) Pterosaurs i) Adaptations for flight 3 membranes in most species These membranes were not just flaps of fragile skin or leather. Rather they had a inside layer of vascularized muscle and three layers of closely spaced fibers called actinofibrils, each crisscrossing the other. These presumably gave strength. 1 2 3 6  14/10/2012 5) Diapsids e) Pterosaurs i) Adaptations for flight The forearm was adapted into a wing with the fourth digit greatly elongated and supporting flight membranes. Compare with bats. Pterodactyle 4 2 3 1 bat 5) Diapsids e) Pterosaurs i) Adaptations for flight A keel on the sternum where flight muscles attached 7  14/10/2012 5) Diapsids e) Pterosaurs ii) hair Bodies of some species are covered in hair-like fibrils, similar to, but not homologous with mammalian hair These hair-like fibrils suggest Pterosaurs were warm blooded Sordes with hair-like fibrils 5) Diapsids e) Pterosaurs iii) Ecology diversity A great variety of jaws suggest specialization into a number of ecological niches, like modern birds. 8  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Pterodon 5) Diapsids e) Pterosaurs iii) Ecology diversity Pteranodon: lacked teeth. Fossils show fish in their stomaches. Originally thought to have fed on fish by skimming them off the surface or diving for them. This is now thought unlikely 9  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Quetzalcoatlus 5) Diapsids e) Pterosaurs iii) Ecology diversity Quetzalcoatlus : fed terrestrially like a stork on small vertebrates Was the largest animal ever to fly at 10-11 m wingspan (33-36ft) 10  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Liaoningopterus 5) Diapsids e) Pterosaurs iii) Ecology diversity Liaoningopterus : teeth up to 4.1 cm, probably a piscivore Liaoningopterus 11  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Cnetochasma 5) Diapsids e) Pterosaurs iii) Ecology diversity Cnetochasma: finely spaced teeth pointed outwards from jaw forming a basket. Probably used it to strain small invertebrates from water Cnetochasma 12  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Pterodaustro 5) Diapsids e) Pterosaurs iii) Ecology diversity Pterodaustro: The teeth on the bottom jaw are so fine they form a tight nit comb like in a modern flamingo. Almost certainly used it to filter feed. Pterodaustro 13  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Cycnorhamphus 5) Diapsids e) Pterosaurs iii) Ecology diversity Cycnorhamphus: teeth at tip of jaw only. May have been used to seek invertebrates in the mud? Cycnorhamphus 14  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Dsungaripterus 5) Diapsids e) Pterosaurs iii) Ecology diversity Dsungdipterus: pointed tip of bill had no teeth and was probably used to pry skellfish or other invertibrates from crevies. The exoskeletons could then be crushed with the knob-like flat teeth at back of jaw. Dsungdipterus 15  14/10/2012 5) Diapsids e) Pterosaurs iii) Ecology diversity Aburognathus: probably fed on airborne insects with its large-gaped mouth much like a nighthawk. 5) Diapsids e) Pterosaurs iv) Sexual selection Crests: many pterosaurs had elaborate crests that varied between closely related species in the same genus. Fossils show these crests were often extended beyond their boney base by keratin. The most likely purpose was for sexual selection (only adult males possessed them in some species). Tupuxuara 16  14/10/2012 5) Diapsids e) Pterosaurs iv) Sexual selection Crests of Nyctosaurus were probably the most extreme. 25 min Nyctosaurus 5) Diapsids f) Dinosauria i) Ancestors of Dinosauria Dinosauria is one group of the Permian Triassic Jurassic Cretaceous Cenozoic Dinosauromorpha. Three main groups of Pterosaurs Dinosaromorpha preceded evolution of Dinosaurs. Lagerpetonidae These were mostly < 3 m in length Marasuchus They appear to have persisted side by side with the early Dinosaurs Dinosauromorpha Silesauridae until end of Triassic End Triassic extinction event caused their demise allowing Dinosaurs to take over as dominant land vertebrates in the Dinosauria Jurassic. 17  14/10/2012 5) Diapsids f) Dinosauria ii) Early history Dinosaurs evolved in the mid to late Triassic The oldest discovered dinosaur is 231 Mya 5) Diapsids f) Dinosauria ii) Early history Dinosaurs evolved in the mid to late Triassic The oldest discovered dinosaur is 231 Mya Early in their history they split into two main groups defined by structure of the hips Permian Triassic Jurassic Cretaceous Cenozoic Ornithischia Saurischia 18  14/10/2012 5) Diapsids f) Dinosauria ii) Early history The early dinosaurs in both the Ornithischia and Saurischia were bipedal, walking upright. The earliest dinosaurs were small, mostly 1 to 2 meters Small size was true of both the Ornithischia and Saurischia Small size persisted through Triassic and much of Jurassic with large sizes evolving in parallel in different groups of Dinosaurs from the mid-Jurassic onwards. Permian Triassic Jurassic Cretaceous Cenozoic Ornithischia Saurischia 5) Diapsids f) Dinosauria ii) Early history The early dinosaurs in both the Ornithischia and Saurischia were bipedal, walking upright. The earliest dinosaurs were small, mostly 1 to 2 meters Small size was true of both the Ornithischia and Saurischia Small size persisted through Triassic and much of Jurassic with large sizes evolving in parallel in different groups of Dinosaurs from the mid-Jurassic onwards. Permian Triassic Jurassic Cretaceous Cenozoic Ornithischia Saurischia 19  14/10/2012 5) Diapsids f) Dinosauria iii) Ornithischia Ornithischians were primarily herbivores Most had beak-like structures at the tips of their mouths for tearing vegetation At the back of the mouth were specially adapted teeth for grinding vegetation Hadrosaurs (duck-billed dinosaurs) had hundreds of teeth Heterodontosaurus (one of the earliest Ornithischians Duck-billed Dinosaur Edmontosaurus (a hadrosaur) with hundreds of teeth 20  14/10/2012 Early Ornithischians are small until about the mid-Jurassic Scutellosaurus 1.2 m Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians Heterodontosaurs < 2m Pisanosaurus 1.0 m 200 Mya 146 Mya 251 Mya 65 Mya During the Jurassic, they radiated into 5 groups, each of which evolved much larger sizes Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians Heterodontosaurs < 2m Pisanosaurus 1.0 m 200 Mya 146 Mya 251 Mya 65 Mya 21  14/10/2012 The armored dinosaurs diverged into the Stegosaurs and Ankylosaurs Only one other group of dinosaurs evolved plated armour. They evolved from small bipedal Dinosaurs like Scutellosaurus Scutellosaurus 1.2 m Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Armored Dinosaurs: Stegosaurs Stegosaurs were characterized by presence of plates and spikes set along the spine and tail. The spines were for defense. The plates may have been for defense, thermoregulation (like elephant ears) or display. Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Stegosaurus Chialingosaurus 22  14/10/2012 Armored Dinosaurs: Stegosaurs Stegosaurs were most prevalent during the Jurassic and became less common during the Cretaceous when the Ankylosaurs become prevalent Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Stegosaurus Chialingosaurus Armored Dinosaurs: Ankylosaurs Ankylosaurs were heavily armored along their back and sides. They split into 2 families: one had a club at the end of its tail, the other didn’t Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Plain-tailed Club-tailed 23  14/10/2012 Armored Dinosaurs: Ankylosaurs QUESTION: Why might dinosaurs have lacked extensive armor prior to mid-Jurassic? 24  14/10/2012 Ornithopods Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Iguanodon Ornithopods Iquanodon and the later Hadrosaurs (duck-billed dinosaurs) are classic examples Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Iguanodon Hadrosaurs 25  14/10/2012 Ornithopods: Hadrosaurs Shantungosaurus: 15 m long, skull 1.6 m 1500 chewing teeth Male and female Parasaurolophus skulls 26  14/10/2012 Ornithopods: Hadrosaurs Ornithopods: Hadrosaurs and Iguanodon 27  14/10/2012 Pachycephalosaurs Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Iguanodon Pachycephalosaurs This group is believed to have used their exaggerated skull dome for head butting much like big-horned sheep Other alternatives is that it was for defense or for flank butting or for display Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Iguanodon 28  14/10/2012 Pachycephalosaurs Ceratopsians Triceratops is the most famous example Triassic Jurassic Cretaceous Stegosaurs Ankylosaurs Ornithopods Pachycephalosaurs Ornithischia Ceratopsians 200 Mya 146 Mya 251 Mya 65 Mya Iguanodon 29  14/10/2012 Ceratopsians :Yinlong Yinlong (described 2006) was the earliest and most primitive type of Ceratopian discovered was bipedal and 1.2 meters long has a number of skeletal features in common with the sister group of Ceratopians, the Pachycephalosaurs, indicating that these features were probably ancestral characters that were retained by Yinlong and Pachycephalosaurs but lost in later Ceratopsians. Yinlong represents a transitional fossil leading to latter Ceratopians. Yinlong Ceratopsians: other early forms Chaoyangsaurus Liaoceratops Archaeoceratops Graciliceratops 30  14/10/2012 Ceratopsians: late Cretaceous forms Ceratopsians: late Cretaceous forms 31  14/10/2012 Ceratopsians: late Cretaceous forms The frills around the head and various horns were highly variable between species. They may have been used for defense but they appear to be rather fragile in many species. An alternative is that they were a secondarily sexual character used for display to females, or in male to male combat 5) Diapsids f) Dinosauria iv) Saurischia Saurischians retained the ancestral state of the hip bones found in earlier diapsid reptiles. Permian Triassic Jurassic Cretaceous Cenozoic Ornithischia Saurischia 32  14/10/2012 5) Diapsids f) Dinosauria iv) Saurischia They diverged early on into a carnivorous clade, the therapods, and a herbivorous clade, the Sauropodomorphs. Ancestral groups belonging to Sauischia were bipedal and carnivorous like Herrerasaurids Triassic Jurassic Cretaceous Herrerasaurids Sauropodomorphs Saurischia Theropods 200 Mya 146 Mya 251 Mya 65 Mya 5) Diapsids f) Dinosauria iv) Saurischia Sauropodomorphs Triassic Jurassic Cretaceous Herrerasaurids Sauropodomorphs Saurischia Theropods 200 Mya 146 Mya 251 Mya 65 Mya 33  14/10/2012 5) Diapsids f) Dinosauria iv) Saurischia Sauropodomorphs Triassic Jurassic Cretaceous Herrerasaurids Panphagia 1.3 m Thecodontosaurus 2 m Saurischia Prosauropods 6 to 10 m Sauropods Theropods 200 Mya 146 Mya 251 Mya 65 Mya 5) Diapsids f) Dinosauria iv) Saurischia Sauropodomorphs Panphagia 1.3 m Bipedal and omnivorous Triassic Jurassic Cretaceous Herrerasaurids Panphagia 1.3 m Thecodontosaurus 2 m Saurischia Prosauropods 6 to 10 m Sauropods Theropods 200 Mya 146 Mya 251 Mya 65 Mya 34  14/10/2012 5) Diapsids f) Dinosauria iv) Saurischia Sauropodomorphs Thecodontosaurus 2 m Bipedal and herbivorous Triassic Jurassic Cretaceous Herrerasaurids Panphagia 1.3 m Thecodontosaurus 2 m Saurischia Prosauropods 6 to 10 m Sauropods Theropods 200 Mya 146 Mya 251 Mya 65 Mya 5) Diapsids f) Dinosauria iv) Saurischia Sauropodomorphs Prosauropods 6 to 10 m Mostly bipedal Triassic Jurassic Cretaceous Herrerasaurids Panphagia 1.3 m Thecodontosaurus 2 m Saurischia Prosauropods 6 to 10 m Sauropods Theropods 200 Mya 146 Mya 251 Mya 65 Mya 35  14/10/2012 Sauropods had many transitional forms leading back to their ancestor with theorpods 5) Diapsids f) Dinosauria iv) Saurischia Sauropodomorphs Sauropods 6 to 60 m Quadrupedal Triassic Jurassic Cretaceous Herrerasaurids Panphagia 1.3 m Thecodontosaurus 2 m Saurischia Prosauropods 6 to 10 m Sauropods Theropods 200 Mya 146 Mya 251 Mya 65 Mya 36  14/10/2012 5) Diapsids f) Dinosauria i) Saurichia Theropods Panphagia (1.3 m) bipedal, Thecodontosaurus (2 m) carnivorous omnivorous, 1 decreased skull size 2 herbivorous, elongated neck Prosauropods (6 to 10 m) 3 cheek pouches 4 quadrupedal Sauropods (5 to ?60 m) Theropods Panphagia (1.3 m) Prosauropods (6 to 10 m) Sauropods (5 to ?60 m) 37  14/10/2012 Several Sauropods: from left to right Camarasaurus, Brachiosaurus, Giraffatitan, and Euhelopus 38  14/10/2012 5) Diapsids f) Dinosauria i) Saurichia Bruhathkayosaurus up to 33 m Amphicoelias ? up to 60 m (only fossil is now lost) The gigantic sizes of many species required skeletal adaptations to support their heavy body weight: they had massive load-bearing limb bones and pelvis which helped support mass Amphicoelias 5) Diapsids f) Dinosauria i) Saurichia Prosauropods and Sauropods were herbivorous Their teeth were good for cutting vegetation but not for grinding it. In contrast Ornithiscians could do both. Fossil evidence indicates they swallowed stones and used them in a gizzard to grind food like birds do. 2 genera of Sauropod with different jaw designs 39  14/10/2012 QUESTION: Why might the late Sauropods have evolved such gigantic proportions? Vertebrate phylogenetic tree Acanthostega Ichthystega Balanerpeton Lissamphibia Caecilians Urodeles Tetrapoda Anurans 1 Synapsids and mammals Lepidosauromorpha Amniotic egg, able to be fully terrestrial Turtles Amniotes Squamates Tuatara Crocadilians Archiosauromorpha Diaspids Pterosaurs Ornithscians Dinosauria Sauropodomorphs Theropods 40  14/10/2012 In our next lecture we will discuss the Theropods Triassic Jurassic Cretaceous Herrerasaurids Sauropodomorphs Saurischia Theropods 200 Mya 146 Mya 251 Mya 65 Mya QUESTION: Major Trend Why might the late Sauropods have evolved such in Dinosauria gigantic proportions? All major dinosaur groups evolved from small, bipedal ancestors which, as they got larger in size became quadrupedal in most cases. 41  14/10/2012 For in depth review: Pages 151 – 159 in Chapter 12 of Cowen 65 min 42