Box Dinosaur behavior

Dinosaur tracks are probably the most familiar trace fossils, and they can tell us a great deal about how the dinosaurs lived. Some dinosaur track sites cover huge areas, and may reveal hundreds or thousands of footprints, often in long trackways, sometimes representing numerous different species. It is fascinating to use these trackways to speculate about ancient behaviors - but you have to be careful! It is important to check whether all the tracks were made at the same time - do they overlap each other or not? A busy-looking track site might have been produced by just one hyperactive dinosaur trotting back and forwards around a water hole.

Three-dimensional dinosaur prints are quite rare. Normally, the dinosaur trots across firm mud or sand, and you are left with simple impressions on the top surface. In some cases, though, the dinosaurs got bogged down in soft sediment, and their feet went in a meter or more. Then, when they wanted to move on, they had to haul their feet out of the gloop, leaving odd-shaped closure traces behind.

A remarkable find from the Late Triassic of Greenland (Gatesy et al. 1999) shows this. Stephen Gatesy, from Brown University, Rhode Island, and his collaborators found strange, narrow, bird-like prints (Fig. 19.9a). Had they been made by a theropod dinosaur with feet made from wire? When they pulled apart the rock layers, they could see that the dinosaur foot had gone in, and sunk through layers of mud, so that the mud flowed back around its ankles. Then, in moving forward and pulling the foot out, the mud flowed back around the exit trace, leaving a long forward trail made by the long middle toe. Computer animations (Fig. 19.9b) demonstrated how the foot may have moved as it went into the mud, and then pulled out at the end of the stride.

Read more about dinosaur tracks on web sites linked to http://www.blackwellpublishing.com/ paleobiology/.

Theropod Feet

Figure 19.9 Theropod dinosaur tracks from the Late Triassic of Greenland. (a) A three-dimensional computer reconstruction (top) shows a theropod foot at three stages in the creation of a deep track, moving from right to left. A photograph of a deep Greenland footprint is shown below. (b) A three-dimensional computer image reconstructing theropod foot movements through sloppy mud. The first toe creates a rearward pointing furrow (1, 2) as it plunges down and forward. The sole of the foot leaves an impression at the back of the track (3) because it is not lifted as the foot sinks. All toes converge below the surface and emerge together from the front of the track (4). (Courtesy of Stephen Gatesy.)

Figure 19.9 Theropod dinosaur tracks from the Late Triassic of Greenland. (a) A three-dimensional computer reconstruction (top) shows a theropod foot at three stages in the creation of a deep track, moving from right to left. A photograph of a deep Greenland footprint is shown below. (b) A three-dimensional computer image reconstructing theropod foot movements through sloppy mud. The first toe creates a rearward pointing furrow (1, 2) as it plunges down and forward. The sole of the foot leaves an impression at the back of the track (3) because it is not lifted as the foot sinks. All toes converge below the surface and emerge together from the front of the track (4). (Courtesy of Stephen Gatesy.)

in lake sediments and lake shores. Others, such as Lockley et al. (1994), have proposed ichnofacies that discriminate among different kinds of assemblages of dinosaur footprints. These proposals do not, however, cover long time spans, as do the classic Seilacher marine ichnofacies, and they are still much debated.

The Glossifungites, Trypanites and Teredo-lites ichnofacies are controlled by substrate alone, and they could theoretically occur

Behavioral Trace Fossil

Figure 19.10 The behavioral classification of trace fossils, showing the major categories, and some typical examples of each. Illustrated ichnogenera are: 1, Cruziana; 2, Anomoepus; 3, Cosmorhaphe; 4, Paleodicyton; 5, Phycosiphon; 6, Zoophycos; 7, Thalassinoides; 8, Ophiomorpha; 9, Diplocraterion; 10, Gastrochaenolites; 11, Asteriacites; 12, Rusophycus. (Based on Ekdale et al. 1984.)

Figure 19.10 The behavioral classification of trace fossils, showing the major categories, and some typical examples of each. Illustrated ichnogenera are: 1, Cruziana; 2, Anomoepus; 3, Cosmorhaphe; 4, Paleodicyton; 5, Phycosiphon; 6, Zoophycos; 7, Thalassinoides; 8, Ophiomorpha; 9, Diplocraterion; 10, Gastrochaenolites; 11, Asteriacites; 12, Rusophycus. (Based on Ekdale et al. 1984.)

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