Isochirotherium = Erythrosuchid tracks

Haubold 1983 described Isochirotherium tracks (Fig. 1) from the Early Triassic Bundsandstein Formation as “thecodonts with partial affinities to dinosaurs or crocodiles.”

Figure 1. Isocheirotherium tracks matched to erythrosuchid pedes based on the longest digits from the heel are 2 and 3, unique to this clade.

Figure 1. Isochirotherium tracks matched to erythrosuchid pedes based on the longest digits from the heel are 2 and 3, unique to this clade.

Isochirotherium tracks have sub equal digits 2 and 3. The only reptiles with such a pes are derived erythrosuchids. If digit 3 is longer than 2 (X’d out in figure 1), then the track is more likely a rauisuchid or a more derived taxon. Shansisuchus and Erythrosuchus have a pes matching Isochirotherium. Primitive Garjainia does not. It has a longer pedal digit 4, like Proterosuchus and, to a less extent, Ornithosuchus.

References
Haubold H 1983. Archosaur evidence in the Buntsandstein (Lower Triassic). Second Symposium on Mesozoic Terrestrial Ecosystems, Jadwisin 1981. Acta Palaeontologica Polonica 28 (1-2):123-132.

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