#anomoepus

[mesozoicmarket]

A pair of dinosaur footprints of the ichnotaxon Anomoepus sp. from the Passaic Formation in a private quarry in New Jersey, United States. This Upper Triassic to Lower Jurassic aged ichnogenus possibly belongs to an early ornithischian of some kind. The footprints have been highlighted or stained for clarity and one of the cracked corners has been repaired. There is also a third footprint on the back of the slab.

[a-dinosaur-a-day]

Anomoepus

Anomoepus is a trackway that’s actually fairly well characterized, originally found in the Hettangian age Early Jurassic beds (between 201 and 199 million years ago) of the Connecticut River Valley in Massachusettes, part of the famous Newark Super Group. 

They were made by Ornithischians, though originally they were thought to be evidence of very early birds - this was later disproven through the absence of claws on the rear digits and the number of toes present. It has also had trackways assigned to it from Western Australia. 

It may have been made by an ornithopod, though this is more uncertain, and many consider it to simply be tracks form a basal ornithischian. In fact, various animals that may have made the tracks commonly attributed to Anomoepus include Heterodontosaurus, Lesothosaurus, Scutellosaurus, and Hypsilophodon, the last of which being the only Ornithopod.

It is also unclear if all the trackways assigned to Anomoepus are really from the same ichonogenus, or if it should be split further. The varying species show a wide variation in footprint length, foot width and toe extension, as shown below; however, whether or not this constitutes major enough differences is uncertain. 

Anomoepus trackways have shown varying different types of pace length and style, with one particular trackway showing a slowing of pace legnth and then stopping, with the length decreasing steadily - this could be due to normal behavior or to animal injury. 

(Anomoepus shown in green) 

Anomoepus trackways have often been shown in tandem with the common early theropod trackway Grallator, indicating a possible predator-prey relationship.It is possible that Anomoepus may have been a slower animal, and thus would not have ventured out into open space where it could have been hunted by Grallator; indeed, Anomoepus tracks in open mudflat and lake environments are much rarer compared to theropod trackways. Only one trackway showed evidence of trotting behavior in Anomoepus, indicating that it remained in more crowded environments for safety. 

Anomoepus has also been described in other formations and time periods including the Norian age of the Late Traissic and the Tithonian age of the Early Cretaceous, indicating that the ichonogenus lasted for a long time, further pointing to a basic Ornithischian origin for the animal. At times, imprints have also indicated quadrupedal movement in the animal, as well as various distributions of body weight and stance while walking and standing. A truly fascinating ichonofossil, Anomoepus shows a remarkable amount about how early Ornithischians walked and lived. 

Sources (Images and Text): 

https://en.wikipedia.org/wiki/Anomoepus

Dalman, S. G., and R. E. Weems. 2013. A new look at morphological variation in the ichonogenus Anomoepus, with special reference to material from the lower Jurassic Newark Supergroup: Implications for Ichnotaxonomy and Ichonodiversity. Bulletin of the Peabody Museum of Natural History 54 (1): 67-124. 

Shout out goes to @captainfartarse​!