Martin A. Whyte

Probable stegosaurian dinosaur tracks from the Saltwick Formation (Middle Jurassic) of Yorkshire, England

A unique dinosaur track, figured by the authors in 1994, from the Saltwick Formation (Aalenian Stage, Middle Jurassic) of Yorkshire, has been referred to Ravatichnus kotshnevi from the Middle Jurassic of Tadjikistan, Central Asia. This ichnospecies has been attributed to an ornithischian, possibly stegosaur, producer. This track is here reinterpreted as two superimposed tracks of Deltapodus brodricki Whyte & Romano, 1994 . Deltapodus brodricki , originally thought to have been made by a sauropod, is here interpreted as having been made by a stegosaurian dinosaur which makes it one of the earliest known records of this group.

A dinosaur ichnocoenosis from the middle jurassic of Yorkshire, UK

An assemblage of dinosaur tracks from the undersurface of a sandstone bed in the Saltwick Formation (Middle Jurassic) of Yorkshire shows a range of morphological types, preservational variants and behavioral styles. The tracks are combinations of transmitted prints and underprints and include three distinct trackways. One trackway was made by an animal walking on exposed damp sand, another was left by an animal swimming diagonally across a current and being swept down current, while the third may have been made by an animal either running or pushing off with its feet as it drifted down current. Environmental conditions that existed during the formation of the trackways varied between crevasse splay floods and exposed damp sand. The morphology of the swimming tracks is sufficiently distinctive to warrant the erection of a new ichnogenus and ichnospecies—Characichnos tridactylus. Previously described material from Kansas, Wyoming and New Mexico can be attributed to this new ichnogenus, while specimens from Germany and Utah are only provisionally referred to it. This indicates a known range from Triassic to Cretaceous.

Trackway Ratio: A New Look at Trackway Gauge in the Analysis of Quadrupedal Dinosaur Trackways and its Implications for Ichnotaxonomy

A new parameter, the Trackway Ratio (TR), is proposed to supplement the previously used trackway gauge to describe and quantify the relative width of trackways in dinosaur quadrupedal gaits. It is expressed as the ratio of the width of the tracks relative to the total width of the trackway (both measured perpendicular to the long axis of the trackway). The ratio may be used with either pes (PTR) or manus (MTR) tracks. The PTR range of values for wide-, medium- and narrow-gauge trackways of previous authors are provisionally suggested to be ≤35%, 36–49% and ≥50%, respectively. The application of such a ratio would permit a more consistent ichnotaxonomy to be adopted where both track morphology and trackway parameters are used to define ichnotaxa. Determination of the TR, as well as other parameters, will be affected by track preservation quality. Recent experiments on track simulation in the laboratory have shed further light on observations made in the field concerning the value of track measurements (in particular track length and width) recorded from below the surface on which the maker was moving. Experimental track simulations in the laboratory have shown that the dimensions of transmitted tracks preserved below the surface on which the foot was impressed may vary from 65% to 135% of the true dimensions of the indenter. Two case studies are presented that quantify the errors that may be made on calculating TR and the size, gait and speed of the maker, from trackways if the preservation of the tracks are not fully understood. It is shown that in individual trackways the PTR may vary along the length of the trackway; so that part of the trackway may be classified as wide-gauge and other parts medium-gauge. There is a relationship between variation in PTR and that of pace angulation along the length of a single trackway. An analysis of 42 trackways, principally sauropod, shows a temporal distribution that does not agree closely with previous suggestions relating to narrow- and wide-gauge trackways.

Reconstruction of Middle Jurassic Dinosaur-Dominated Communities from the Vertebrate Ichnofauna of the Cleveland Basin of Yorkshire, UK

Globally, skeletal remains of dinosaurs are particularly rare throughout much of the Middle Jurassic. Thus, other sources of evidence, and most importantly ichnofaunas, are important indicators of the contemporary terrestrial vertebrate communities. The outcrops of the Ravenscar Group (Aalenian—Bajocian) within the Cleveland Basin of Yorkshire, UK, which have recently been recognised as a megatracksite of global significance, provide one such major source of ichnofaunal information of this age. A comprehensive database on the variety and occurrence of dinosaur and other vertebrate traces within the Ravenscar Group has been built from a long-term and detailed study of the sequence. Thirty different and distinct morphotypes of vertebrate traces have been recognised and are being analysed and further differentiated morphometrically. Some of the morphotypes represent behavioural, preservational and perhaps ontogenetic variants of other morphotypes, but nevertheless the range of quadrupedal and bipedal prints allows an overall fauna of sauropod, stegosaurian, ornithopod and theropod dinosaurs along with crocodiles, pond turtles and fish to be reconstructed. The distribution and abundance of prints and print types within the succession shows evidence of environmental control on the behaviour and distribution of the vertebrates. Case studies highlight both the advantages and disadvantages of this type of data in reconstructing palaeocommunities.

Laboratory-controlled simulations of dinosaur footprints in sand: A key to understanding vertebrate track formation and preservation

Abstract Dinosaur tracks and trackways yield invaluable information as to the identity, size, and gait of the trackmaker and the conditions of the media (=substrate) it traversed. Correctly interpreting tracks requires consideration of their three-dimensional morphology. Laboratory-controlled simulations were conducted to investigate the subsurface track morphology formed from differently shaped feet, as the shape of the footprint deteriorates with depth. A circular, triangular, and a tridactyl dinosaur foot-shaped template, or indenter, were indented vertically into two types of sand, with four moisture contents—dry, 10%, 20%, and saturated. The morphology of all three indenters was preserved most accurately in the moist sand. Tracks in dry and saturated sand were distorted by a greater degree of media deformation. Digit imprints of tridactyl tracks were only clearly discernible in near-surface layers and were deformed by shear zones or inward movement of sediment in dry and saturated sand. The long digits of the template produced the greatest degree of outward displacement, and tracks became wider with depth and deepest in the heel region. This was most distinct in dry sand, where extensive shear zones in cross section demonstrated the outward and upward movement of sediment. All tracks in saturated sand were characterized by considerable downward displacement of sediment and features related to the upward pull of sediment as the templates were withdrawn. These diagnostic features allow vertebrate tracks to be differentiated from nonbiogenic, soft-sediment deformation. Fossil tracks studied from the Middle Jurassic succession of the Cleveland Basin, Yorkshire, demonstrate affinities to the experimental tracks formed in saturated sand.

Turning points in Phanerozoic history

During the last 450 Myr there has been concomitant variation in the Earths rotation rate, the polarity bias of the geomagnetic field, the amount of activity at ocean ridges, sea level and climate. At turning points when trends in the variables reverse themselves, climatic instabilities have disrupted biological ecosystems and led to mass extinctions.

Phosphatized soft tissues in bivalves from the Portland Roach of Dorset (Upper Jurassic)

Phosphatized soft tissues are preserved in abundance in the trigoniids (Bivalvia) Laevitrigonia gibbosa and Myophorella incurva from the Portland Roach (Upper Jurassic) of Dorset. Cellular structures are preserved and fossilization is almost exclusively the result of a dense coating of mineralized microbes. Phosphatized soft tissues are restricted entirely to those trigoniids whose valves remained tightly closed after death. Only in these specimens was sufficient phosphorus concentrated by the decay of their most ‘labile’ soft tissues to trigger the precipitation of apatite in and around microbes infesting their more ‘refractory’ soft tissues. The absence of fossilized soft tissues in the rest of the fauna implies that phosphatization was very taxon-specific.

The first record of xiphosurid (arthropod) trackways from the Saltwick Formation, Middle Jurassic of the Cleveland Basin, Yorkshire

Trackways attributed to a xiphosurid (arthropod) maker are described for the first time from the Middle Jurassic Saltwick Formation, Ravenscar Group, of the Cleveland Basin, Yorkshire. The trackways are assigned to Kouphichnium aff. variabilis (Linck, 1949) and clearly demonstrate the heteropody and varied behaviour of the maker. Their occasional asymmetry indicates a slight rotation of the body relative to the direction of locomotion. The Saltwick Formation has generally been regarded as a coastal plain deposit, and the presence of xiphosurid tracks reinforces the suggestions of periodic marine influences.

Range of Experimental Dinosaur (Hypsilophodon foxii) Footprints Due to Variation in Sand Consistency: How Wet Was the Track?

The laboratory-controlled simulations of dinosaur footprints in this study revealed characteristic track features that could be used to identify the consistency of sand substrates and provide an insight into the paleoenvironment. A model foot of Hypsilophodon foxii was indented into three sands of four different moisture (= water) contents. The two intermediate moist states were characterized by shallow tridactyl impressions, in which only digits II–IV were impressed, showing details of padding and claws. Where the foot penetrated more deeply, in the dry and saturated states, the hallux and heel were also impressed; in these cases, the foot detail was not preserved accurately and track morphology deviated significantly from that of the foot. Dry sand tracks were characterized by the outward and upward movement of sediment and tracks in saturated sand by mainly downward displacement. The finer-grained saturated sand was also associated with liquefaction and closure of digit imprints. Tracks from the Middle Jurassic Cleveland Basin of Yorkshire showed features of the saturated state. The range of experimental track morphotypes formed by one foot highlighted the difficulties in assigning a print type to a particular trackmaker and the importance of excluding preservational variants from ichnotaxonomic studies.

New finds of stegosaur tracks from the Upper Jurassic Lourinhã Formation, Portugal

Eleven new tracks from the Upper Jurassic of Portugal are described and attributed to the stegosaurian ichnogenus Deltapodus. One track exhibits exceptionally well-preserved impressions of skin on the plantar surface, showing the stegosaur foot to be covered by closely spaced skin tubercles of ca. 6 mm in size. The Deltapodus specimens from the Aalenian of England represent the oldest occurrence of stegosaurs and imply an earlier cladogenesis than is recognized in the body fossil record.