#ichnofossil

Feeding patterns

These swirly patterns were made by living organisms at the bottom of the sea approximately 250 million years ago while they were feeding on an organic matter mixed within the sediment. The pictured sediments were buried by more sediments, hardened and eventually brought to the surface by tectonic processes without messing up such signs of ancient life.

From Niedźwiedzki et al., 2013

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Prorotodactylus is an ichnofossil from a Dinosauromorph, and so we’re doing it here during our coverage of Dinosauromorphs! It is a footprint known from the Holy Cross Mountains of Poland. It is known from the Early and Middle Triassic, so sometime between 251 and 247 million years ago. As such it helps to provide more evidence to the idea that Dinosaurmorphs evolved much earlier than previously supposed - instead of evolving midway through the Triassic, the general group must have evolved close to the start of the Early Triassic, or potentially even earlier, right in the crux of the Permian-Triassic mass extinction event. 

Protodactylus are tracks made by a small quadrupedal animal with a long stride, with the hind feet placed on the same line as the fore feet. it had claws on its feet and it shows distinctly Archosaurian features, with a narrow trackway and a particular pace angle that showed that Protodactylus had an erect gait like later Dinosaurs rather than a sprawling one, and also a digitigrade posture like Dinosaurs did. In fact, its tracks line up fairly neatly with Lagerpeton, and could have been made by an animal similar to Lagerpeton. It was probably transitioning to a bipedal form of locomotion. 

Sources:

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

Niedźwiedzki, G., S. L. Brusatte, R. J. Butler. 2013. Protodactylus and Rotodactylus tracks: an ichnological record of dinosauromorphs from the Early-Middle Triassic of Poland. Anatomy, Phylogeny, and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379. 

Ichnofossils or trace fossils, are marks left in the sedimentary record by living organism but are not a body part of the organism. For example, pictured are burrows left by an organism that was feeding on an organic matter in the sediment. These provide an evidence of ancient organism activity after sediment deposition but before it turned into hard rock.

From Brusatte et al., 2011

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Sphinogpus is a Dinosauriform trackway known from the Grès d’Antully Formation in France, as well as the Holy Cross Mountains in Poland. It lived about from 228 to 250 million years ago, indicating that this track form was very common for a long time in the Triassic. Though it is unknown what sort of species made these tracks, it is likely to be that of a Dinosauriform, given its bipedal gait and the overall shape corresponding to something more derived than Lagerpeton, and might even be that of a Dinosaur proper, though that cannot be corroborated fully. It is a fairly rare track in Poland, indicating that this group of more-derived Dinosauromorphs took a while to establish in the Earliest Triassic. 

Sources:

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

Brusatte, S. L., G. Niedźwiedski, R. J. Butler. 2010. Proceedings of the Royal Society B 278 (1708): 1107-1113. 

From Niedźwiedzki et al., 2013

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Rotodactylus is another Dinosauromorph footprint fossil from Poland, known from the Baranów Tracksite of the Röt Formation of Poland, living in the Olenekian to Ansian ages of the Early Triassic, about 251 to 247 million years ago. This is a common track type that is thought to have been made by an early Dinosauromorph, similar to Lagerepton, and the tracks of Rotodactylus show notable similarities to what one would expect early-derived Avemetatarsalians to make tracks of. Like Protodactylus, Rotodactylus is notable for implicating an earlier date of Dinosaurmorph divergence than previously supposed. It is, however, slightly more enigmatic than Protodactylus. 

Sources:

Niedźwiedzki, G., S. L. Brusatte, R. J. Butler. 2013. Protodactylus and Rotodactylus tracks: an ichnological record of dinosauromorphs from the Early-Middle Triassic of Poland. Anatomy, Phylogeny, and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379. 

Another ichnofossil, thought to be a crustacean burrow. They're generally smooth inside, and lumpy outside, where the sediment was packed in tight to support the burrow. They date as far back as the early Permian (298mya).

Unlike Zoophycos, Ophiomorpha is usually found in rocks that form from sand off beachs and in tidal sandflats, although some have been found in turbidite layers where those turbidites were well-oxygenated. We can only presume that the Zoophycos organisms are much more tolerant of low oxygen levels than Ophiomorpha. Other ichnofossils from the same near-shore rocks include Skolithos, Arenicolites, and Diplocraterion. In fact that assemblage of four ichnospecies is called the Skolithos ichnofacies, and is used to infer a shallow-water paleoenvironment.

Not a fossil animal. Not a fossil plant, either, although that's what they were originally described as in 1855. They're actually an ichnofossil - a trace fossil preserving the activity of a long-dead animal. What the creature WAS is an open question - it was probably worm-like. Although of course there's no guarantee that it's the same animal that's been making these ichnofossils for 521 million years.

The ichnofossils can be a meter across and deep. In structure they're closely packed J- or U-shaped lobes around a burrow, although as the epochs rolled on Zoophycos traces have been getting more and more elaborate, with branching lobes or layers built up in a corkscrew-fashion. Earlier examples are from shallower depths, but later they're more often found in deepwater turbidite beds, where mud and sand was deposited by huge underwater landslides. However, even in more recent times they're also known from nearshore formations where storms deposit a lot of sediment.

From all the evidence, it would seem the Zoophycos organism (or organisms) lived in places where there aren't many other animals to compete with them, and were methodically searching freshly settled sediment around them for anything to eat.