Late Triassic

Global and temporal distribution of silesaurids shown on a Middle and Late Triassic (Ladinian-Norian) map of the northern and southern regions of Pangea.

A reconstruction of Erythrovenator jacuiensis based on a skeletal by Maurissauro. This basal theropod comes from the Late Triassic Candelária Formation of Brazil.

Ahvaytum is a saturnaliid sauropodomorph from the Late Triassic of what is now Wyoming. It is the oldest known dinosaur from the northern continent of Laurasia, challenging previous hypotheses of dinosaur origins and dispersal. Typical of basal dinosaurs from the Triassic, Ahvaytum was a small slender biped, reaching about 1 m in body length.

Life restoration of the Triassic ichthyosaur Callawayia neoscapularis. Three specimens of this ichthyosaur are known, the holotype, ROM 41993, and two referred specimens, TMP 94.380.11 and 94.382.2. The skull is primarily based on ROM 41993, cross-checked against TMP 94.380.11 and TMP 94.382.2. The vertebral column is based primarily on TMP 94.382.2 as it is the most complete of these specimens, while the ribs were based on ROM 41993. The forelimbs were mainly based on those of ROM 41993, with TMP 94.380.11 used to determine their breadth. The hindlimbs were based on TMP 94.380.11, especially the more complete right hindlimb. ROM 41993 was cross-scaled with TMP 94.380.11 by the dimensions of the forelimb epipodials, which produced similar vertebral dimensions. The two TMP specimens were cross-scaled based on femoral length, also producing similar vertebral dimensions. Nicholls & Manabe (2001) stated that no wedge-shaped caudal centra supporting a tailbend were found and that there was no evidence of a bend being present, though considered that they might have existed in the gap in the preserved caudals. Since various other Triassic ichthyosaurs have since been found to have tail bends, one was illustrated here. A modest downturn of roughly 15° was illustrated, comparable to that in Guanlingsaurus, and the location of the bend within the gap in the preserved vertebrae matches well with the location of the bend in Guizhouichthyosaurus. References McGowan, C. (1994). "A new species of Shastasaurus (Reptilia: Ichthyosauria) from the Triassic of British Columbia: The most complete exemplar of the genus". Journal of Vertebrate Paleontology 14 (2): 168–179. DOI:10.1080/02724634.1994.10011550. Nicholls, E. L.; Manabe, M. (2001). "A new genus of ichthyosaur from the Late Triassic Pardonet Formation of British Columbia: Bridging the Triassic-Jurassic gap". Canadian Journal of Earth Sciences 38 (6): 983–1002. Ji, C.; Jiang, D.Y.; Hao, W.; Sun, Y. (2011). "True tailbend occurred in the Late Triassic: Evidence from ichthyosaur skeletons of South China". Acta Scientiarum Naturalium Universitatis Pekinensis 47 (2): 309–314. Shang, Q. H.; Li, C. (2009). "On the occurrence of the ichthyosaur Shastasaurus in the Guanling biota (Late Triassic), Guizhou, China". Vertebrata PalAsiatica 47 (3): 178–193.

Californosaurus perrini, an ichthyosaur from the Late Triassic of North America, pencil drawing

Fossil samples – e.g. ‘primitive’ bony fish (1, 2), a skull of a temnospondyl ‘amphibian’ (probably a metoposauroid) in dorsal view (3), a skull of an archosaur of the crocodile lineage (probably a phytosaur) in palatal view (4), holotype of the “gliding reptile” Icarosaurus siefkeri [1] (5) and Atreipus-Grallator-type dinosaur tracks (bottom right) – from the Newark Supergroup, i.e. a series of mainly Late Triassic to Early Jurassic sedimentary rocks of eastern North America ↑ Edwin H. Colbert: A gliding reptile from the Triassic of New Jersey. American Museum Novitates, 2230. American Museum of Natural History, New York 1966, digitallibrary.amnh.org, cf. fig. 3 therein.

Tawa is an early theropod from the Late Triassic. The genus is named after the Hopi word for the Puebloan sun god. It was a bipedal carnivore, estimated around 2.5 m in length, and weighing about 15 kg. A basal theropod, Tawa shares physical characteristics with coelophysoids and herrerasaurids, and its discovery supports the theory that dinosaurs originated in the southern supercontinent of Gondwanna, before diversifying as Pangea split apart.

Thalattosaurus alexandrae (left) and Nectosaurus halinus (right) of Late Triassic California

Laurasia during the closure of the Iapetus Ocean at 430 Ma. Made using GPlates: Citations: Golonka, J. (2007), Late Triassic and Early Jurassic palaeogeography of the world, Palaeogeography, Palaeoclimatology, Palaeoecology, 244(1-4), 297-307. Müller, R., M. Sdrolias, C. Gaina, and W. Roest (2008), Age, spreading rates, and spreading asymmetry of the world's ocean crust, Geochemistry, Geophysics, Geosystems, 9(Q04006), 19. Seton, M., R. Müller, S. Zahirovic, C. Gaina, T. Torsvik, G. Shephard, A. Talsma, M. Gurnis, M. Turner, and M. Chandler (2012), Global continental and ocean basin reconstructions since 200 Ma, Earth-Science Reviews, 113(3-4), 212-270. Torsvik, T., and R. Van de Voo (2002), Refining Gondwana and Pangea Palaeogeography: Estimates of Phanerozoic non dipole (octupole) fields, Geophysical Journal International, 151(3), 771-794. Wright, N., S. Zahirovic, R. D. Müller, and M. Seton (2013), Towards community-driven, open-access paleogeographic reconstructions: integrating open-access paleogeographic and paleobiology data with plate tectonics, Biogeosciences, 10, 1529-1541

Laurasia during the closure of the Iapetus Ocean at 430 Ma. Made using GPlates: Citations: Golonka, J. (2007), Late Triassic and Early Jurassic palaeogeography of the world, Palaeogeography, Palaeoclimatology, Palaeoecology, 244(1-4), 297-307. Müller, R., M. Sdrolias, C. Gaina, and W. Roest (2008), Age, spreading rates, and spreading asymmetry of the world's ocean crust, Geochemistry, Geophysics, Geosystems, 9(Q04006), 19. Seton, M., R. Müller, S. Zahirovic, C. Gaina, T. Torsvik, G. Shephard, A. Talsma, M. Gurnis, M. Turner, and M. Chandler (2012), Global continental and ocean basin reconstructions since 200 Ma, Earth-Science Reviews, 113(3-4), 212-270. Torsvik, T., and R. Van de Voo (2002), Refining Gondwana and Pangea Palaeogeography: Estimates of Phanerozoic non dipole (octupole) fields, Geophysical Journal International, 151(3), 771-794. Wright, N., S. Zahirovic, R. D. Müller, and M. Seton (2013), Towards community-driven, open-access paleogeographic reconstructions: integrating open-access paleogeographic and paleobiology data with plate tectonics, Biogeosciences, 10, 1529-1541

Original figure caption: Trackway S1 (Eosauropus sp.), here attributed to a sauropod trackmaker based on pedal synapomorphies; trackmaker is moving towards the south-west. Two consequtive pes impressions of a tridactyl Grallator [i.e. a theropod] trackway can be seen left to the S1 trackway. Note: The tracks are preserved on a bedding plane of a thin siltstone bed of the Late Triassic Fleming Fjord Formation of East Greenland. A) shows a photograph of the trackway(s) as preserved on the bedding plane (i.e. as concave epireliefs); B) shows a color shaded relief map based on a high-resolution photogrammetric 3D-model of the bedding plane; C) is an interpretative outline drawing of the S1 trackway; abbreviations: LM = left manus (i.e. forefoot), LP = left pes (i.e. hindfoot), RM = right manus, RP = right pes, numbers increase in walking direction.

Californosaurus perrini, an ichthyosaur from the Late Triassic of North America, pencil drawing

Californosaurus perrini, an ichthyosaur from the Late Triassic of North America, pencil drawing

Left maxilla of the silesaurid Agnosphitys cromhallensis from the Late Triassic (Rhaetian) of England.

Pantydraco caducus, a sauropodomorph from the Late Triassic or Early Jurassic of England, after Yates, 2003, pencil drawing, digital coloring

Photograph of Museo civico di scienze naturali di Bergamo (MCSNB) 2888, the holotype specimen of Eudimorphodon ranzii ZAMBELLI 1973, a basal pterosaur from the Norian (middle Upper Triassic) of the Italian Alps.[1] ↑ see fig. 8A in Silvio Renesto (2006): A reappraisal of the diversity and biogeographic significance of the Norian (Late Triassic) reptiles from the Calcare di Zorzino. In: Jerry D. Harris, Spencer G. Lucas, Justin A. Spielmann, Martin G. Lockley, Andrew R.C. Milner, James I. Kirkland (eds.): The Triassic-Jurassic Terrestrial Transition. New Mexico Museum of Natural History and Science Bulletin 37:445–456 (online)