Test 4 ALL - DINOSAUR TRACKS TRACKWAYS AND OTHER TRACE...

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DINOSAUR TRACKS, TRACKWAYS, AND OTHER TRACE FOSSILS - INTRODUCTION Dinosaur footprints are trace fossils, as are previously discussed skin impressions, leaving behind information on dinosaurs without fossil bones. Dinosaur tracks or footprints are left behind as impressions of the foot (pes) or hand (manus) made in sediment. The best tracks were made in sediment that was moist but not too moist. Preservation occurs in one of two ways, as molds left by the limbs or as casts by filling of impressions by overlying sediment. More than one consecutive track is a trackway. Undertracks (web) are deep deformed layers under the original track surface. An excellent web site on this subject is Overview of Dinosaur Tracking (web). - WHERE ARE TRACKS AND TRACKWAYS FOUND? Dinosaur tracks have been found on all continents, except Antarctica. Dinosaur tracks localities number more than a thousand, many of them with hundreds of tracks. In many regions they are the only evidence of the former presence of dinosaurs. - TAKING MEASUREMENTS AND NAMING TRACKS TAKING MEASUREMENTS The initial step in measuring dinosaurs tracks and trackways is to measure the size and shape of individual fore (manus) and hind (pes) footprints and the angles and distances between them. Such measurements offer clues to differences between front and hind feet, the number of weight bearing digits, the presence of soft tissue structures (hooves, pads, etc.), etc. The number of digits in dinosaur hands and feet vary from three to five. The term pentadactyl refers to those with five digits, tetradactyl to those with four digits, and tridactyl to those with three digits. Among the important measurements taken at trackways is the stride. The stride represents the distance between successive steps of an individual limb, for example, between one step of the left forelimb and the next step of the left forelimb. The pace refers to the distance between successive steps, for example, the distance between the step of your right foot and your next step of the left foot. The pace angulation is the angle formed between the pace and the opposite footprint. In a bipedal dinosaur the pace angulation would be that angle formed between a right print and the two left prints that preceded or
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followed it, or visa versa. Other important measurements are of the footprint width, length, and trackway width. NAMING TRACKS Trace fossils like footprints are given scientific names for the same reason scientific names are given to species based upon their bones The Linnaean system of nomenclature provides a uniform language of communication for scientists to refer to the same object or species. Names given to tracks are binomial, the first name refers to the ichnogenus (trace fossil genus) and the second to the ichnospecies (trace fossil species).
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