Jurassic

Life restoration of Harpactognathus gentryii, a pterosaur from Jurassic USA

Reconstructed skull of Duriavenator hesperis showing known material (white) of the holotype and only known specimen. Unknown bones based on related Eustreptospondylus oxoniensis. Scale bar is 10cm, image is 10px/cm. Cranial anatomy based on Benson (2008) "A redescription of "Megalosaurus" hesperis (Dinosauria, Theropoda) from the Inferior Oolite (Bajocian, Middle Jurassic) of Dorset, United Kingdom"

Reconstructed skull of Wiehenvenator albati based on holotype specimen (white). Scale bar is 10cm, image if 10px/cm. Unknown material based on related Torvosaurus tanneri. Cranial anatomy based on Rauhut et al (2016) "A new megalosaurid theropod dinosaur from the late Middle Jurassic (Callovian) of north-western Germany: implications for theropod evolution and faunal turnover in the Jurassic"

Reconstructed skull of the holotype and only specimen of Leshansaurus qianweiensis based on the possibly related megalosaurid Dubreuillosaurus valesdunensis. Scale bar is 10cm, image is 10px/cm. Cranial anatomy from figures in Fei et al. (2009) "A new carnosaur from the Late Jurassic of Qianwei, Sichuan, China". White bones are figured, light grey bones are unfigured and minimally described.

Fossil of Streptospondylus, a dinosaur from the Middle Jurassic period of France. Took the photo at the Gallery of Paleontology and Comparative Anatomy in the French National Museum of Natural History, Paris.

A reconstruction of Aorun, a small coelurosaurian theropod from the Middle Jurassic China.

Ceratopsipes goldenensis Lockley & Hunt, 1995 - ceratopsian dinosaur trackway in the Cretaceous of Colorado, USA. Ceratopsians are the "horned dinosaurs". They were large, quadrupedal, herbivorous dinosaurs having a beaked skull and a frill - an extension of bone behind the skull that partially covered the neck. Ceratopsian dinosaurs are known from the Jurassic and Cretaceous. The last members of the group died out at the Cretaceous-Tertiary boundary, 65 million years ago. Seen here is a ceratopsian dinosaur trackway. Ceratopsian footprints are very rare. The best examples are in Colorado's Laramie Formation, a nonmarine, coastal plain to deltaic succession of mostly mixed siliciclastic sedimentary rocks - sandstones, siltstones, claystones, and coals. The footprints here consist of convex bulges on the basal surfaces of structurally-tilted sandstone beds. The ichnospecies Ceratopsipes goldenensis was named based on footprints at this locality. The trackmaker was very likely Triceratops, the # 1 most famous ceratopsian dinosaur. From on-site signage: Triceratops Tracks Several tracks of Triceratops, or a closely related horned dinosaur were first discovered in this area and named Ceratopsipes goldenensis (meaning tracks of a horned dinosaur from Golden). By happy coincidence, the first Triceratops known to science also comes from the greater Denver area near 13th Avenue and Federal Blvd. Growing to a length of almost 25 feet, Triceratops and other members of the horned dinosaur family were herbivorous animals that roamed in herds. Their trademark horns and frills that covered their necks probably served for defense. A replica Triceratops skull is on display in the clubhouse at the Fossil Trace Golf Club. These tracks (identified by small signs) help us understand that Triceratops walked with a narrow gait and erect front limbs than with a wide, sprawling gait as previously depicted. In 1887, the first Triceratops bones known to science were also discovered locally at a site near 13th Avenue and Federal Boulevard in Denver. Nearby one may see many other traces of life such as burrows, probably made by invertebrates and impressions of plant debris. Note that you are looking at all tracks and traces from the underside - in negative aspect - what one might call a worm’s eye view. All of these trace fossils indicate that the Golden area once had a warm, temperate to subtropical climate. Classification: Animalia, Chordata, Vertebrata, Reptilia, Archosauria, Dinosauria, Ornithischia, Marginocephalia, Ceratopsia, Ceratopsidae Stratigraphy: Laramie Formation, Maastrichtian Stage, upper Upper Cretaceous Locality: outcrop along Triceratops Trail, Parfet Prehistoric Preserve, southern side of the town of Golden, Colorado, USA (~vicinity of 39° 44' 35.24" North latitude, 105° 13’ 09.69" West longitude) Some info. from: Lockley & Hunt (1995) - Ceratopsid tracks and associated ichnofauna from the Laramie Formation (Upper Cretaceous: Maastrichtian) of Colorado. Journal of Vertebrate Paleontology 15: 592-614.

reconstruction of the Early Jurassic sauropod Perijasaurus lapaz.

Figure 1: Reconstruction of the skull of Bellusaurus sui from the Middle-Late Jurassic Shishugou Formation of Xinjiang, China. This reconstruction is a composite based on isolated holotypic and referred material. (A) Right lateral view. (B) Dorsal view. Holotypic elements are indicated in blue and referred elements are in green.

Original figure caption: .mw-parser-output .smallcaps{font-variant:small-caps}The Middletown Slab covered with the Footprints of Carnivorous Dinosaurs. The tracks are in high relief. Additional notes: Most if not all of these tridactylous (i.e. three-toed) footprints/tracks (but not the actual trackmaker!) are referred to as Grallator or as Grallator-type trace fossils. “High relief” means that these are actually casts of footprints forming a positive relief on the lower surface of the sandstone slab (so-called positive hyporelief). The material that originally formed the mud over which the dinosaurs walked was too friable to be recovered from the quarry in one piece. The slab consists of so called ‘brownstone’ which is the trading name of the sandstone quarried at Middletown, Connecticut. This sandstone belongs to the Lower Jurassic Portland Formation of the Hartford Basin (“Connecticut Valley”) and thus to the upper part of the Newark Supergroup. The trackmakers probably were relatively small ‘primitive’ theropod dinosaurs (coelophysoids) such as Podokesaurus the remains of which were recovered from Lower Jurassic deposits of the Hartford Basin.

Eubrontes dinosaur track from the Jurassic of Connecticut, USA. Trace fossils are any indirect evidence of ancient life. They refer to features in rocks that do not represent parts of the body of a once-living organism. Traces include footprints, tracks, trails, burrows, borings, and bitemarks. Body fossils provide information about the morphology of ancient organisms, while trace fossils provide information about the behavior of ancient life forms. Interpreting trace fossils and determination of the identity of a trace maker can be straightforward (for example, a dinosaur footprint represents walking behavior) or not. Sediments that have trace fossils are said to be bioturbated. Burrowed textures in sedimentary rocks are referred to as bioturbation. Trace fossils have scientific names assigned to them, in the same style & manner as living organisms or body fossils. This track was made by a theropod, a group of small to large, carnivorous, bipedal dinosaurs. The specimen comes from a Triassic to Jurassic terrestrial sedimentary succession that filled up a half graben, many of which occur along America's eastern seaboard. Such half-graben basins formed during the Triassic as the Pangaea supercontinent tried to rift apart, but failed. Pangaea successfully broke apart during the Jurassic. Stratigraphy: East Berlin Formation, Newark Supergroup, Lower Jurassic Locality: unrecorded / undisclosed site at or near the town of Rocky Hill, central Connecticut, USA Info. at: mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=CTJeb%3B0 and en.wikipedia.org/wiki/Eubrontes

The type specimen of the ichnogenus Cheliceratichnus, from the Early Jurassic East Berlin Formation of Holyoke, Massachusetts.

Bifurculapes laqueatus trackway (positive hyporelief, i.e. casts on the bottom surface of the bed) from the Early Jurassic East Berlin Formation (Hartford Basin) of Holyoke, Massachusetts (not the same specimen as this one). See coin (1 U.S. cent, 19.05 mm in diameter) for scale.

Bifurculapes laqueatus trackway (positive hyporelief, i.e. casts on the bottom surface of the bed) from the Early Jurassic East Berlin Formation (Hartford Basin) of Holyoke, Massachusetts (not the same specimen as this one). See coin (1 U.S. cent, 19.05 mm in diameter) for scale.

A trackway of the trace fossil Bifurculapes laqueatus (positive hyporelief, i.e. casts on the bottom surface of the bed) from the Early Jurassic East Berlin Formation (Hartford Basin) of Holyoke, Massachusetts (not the same specimen as this one). Scale is in cm.

Morrison Formation (lower half), Jurassic-Cretacous boundary (K1 Unconformity) at red and orange paleosol, Cedar Mountain Formation (drab gray), and capping Naturita Formation. West of Dinosaur National Monument.