Macropodosaurus

History of discovery

In 1963, Russian geologist F.H. Khakimov discovered unusual bipedal trackways at the Shirkent-1 locality of the Shirabad Formation in the Shirkent River valley (Tajikistan). The material consisted of a series of four-toed footprints found in Cenomanian slabs of hard clayey limestone. They later became the holotype material for the new ichnogenus and ichnospecies Macropodosaurus gravis, described and named in 1964 by Sergey A. Zakharov. He stated that they were made by a bipedal four-toed dinosaur and not a quadrupedal animal.

More later, in 2006 Andrey G. Sennikov re-examined these footprints and concluded that a therizinosaurid dinosaur likely made those tracks. He compared Macropodosaurus with the feet of Erlikosaurus and Therizinosaurus noting that in a plantigrade position they match the morphology of the tracks. Sennikov considered these tracks to be more associated with therizinosaurids and proposed a plantigrade stance for them.

In 2008 two Macropodosaurus tracks were discovered in sediments of the Ferron Formation, Utah, in a locality known as the Muddy Creek Canyon. Although these have been in knowledge since their discovery, in 2013 they were described by Gerard Gierlinski and Martin Lockley.

Macropodosaurus has also been discovered in the Maastrichtian strata of Poland in 2007. This footprint is reminiscent of the tracks described by Zakharov and was assigned to Macropodosaurus sp. This discovery may indicate the ancient presence of therizinosaurids in Europe.

In 2017 Masrour with colleagues reported more Macropodosaurus footprints in what is now Morocco, further expanding the paleobiogeographical range of therizinosaurids.

Sennikov re-analyzed Macropodosaurus and the overall foot anatomy of therizinosaurids, concluding that this group had a plantigrade stance. While ancestral therizinosaurs had a gracile and digitigrade stance, therizinosaurids evolved a robust, ponderous body plan and plantigradism.

Description

Macropodosaurus tracks are relatively large, having average dimensions of 50 cm long and 30 cm wide. Individually, they are narrow/long, and have four distinct digits which are set closely together. Each digit ends in moderately pronounced claws. Long trackways are narrow, running nearly parallel to each other at a distance of ~1 m.

References

References

1. (1964). "Paleontology of Tajikistan". Academy of Sciences of Tajik S.S.R. Press.
2. (2006). "Читая следы сегнозавров". Priroda.
3. (2013). "At the Top of the Grand Staircase: The Late Cretaceous of Southern Utah". Indiana University Press.
4. (2015). "New Dinosaur Footprints from the Upper Cretaceous of Poland in the Light of Paleogeographic Context". Ichnos.
5. (2017). "Anza palaeoichnological site. Late Cretaceous. Morocco. Part II. Problems of large dinosaur trackways and the first African Macropodosaurus trackway". Journal of African Earth Sciences.
6. (2021). "The Plantigrade Segnosaurians: Sloth Dinosaurs or Bear Dinosaurs?". Paleontological Journal.
7. (2016). "Dinosaur Facts and Figures: The Theropods and Other Dinosauriformes". Princeton University Press.