Dehnaripus, Abbassi & Salehi Tinooni & Ghorbani Dehnavi & Shakeri & Eshaghi, 2024

Abbassi, Nasrollah, Salehi Tinooni, Mohammad, Ghorbani Dehnavi, Mahdi, Shakeri, Safoora & Eshaghi, Ali, 2024, Oligocene vertebrate footprints from the Lower Red Formation, Central Iran, Fossil Record 27 (2), pp. 265-287 : 265-287

Ichnogenus Dehnaripus igen. nov.

Type ichnospecies.

Dehnaripus incognitus

Etymology.

From village Deh Nar, where the footprints were discovered, and pus meaning foot.

Diagnosis.

Large, circular footprints consisting of manus and pes imprints (> 10 cm). Manus imprint is larger than the pes, deeper in epirelief preservation. Usually, footprints show unorganized radial large wrinkles, and digital and metatarsal / metacarpal position are ambiguous. The technical imaging shows five thick digits in the manus with large metacarpal imprints, and three-digit imprints in the digitigrade pes imprint. Outlines of digit imprints in pes and manus are unclear.

Discussion.

Morphology and quality of the preservation of footprints are controlled by numerous factors, partly related to sedimentological features of the substrate and others by the biological characteristics of the track-maker and, finally, preservational conditions. Some reports of vertebrate tracks include ambiguous footprints with unusual morphology; these mostly were reported from the dinosaur tracks (e. g., Harris and Lacovara 2004). There are a few documents about enigmatic footprints from the Cenozoic (e. g., Mayoral et al. 2023). Demathieu et al. (1984) reported mammal enigmatic small footprints from the Oligocene of southern France. These footprints are pentadactyl with forwarded three-digit imprints (II-III-IV) and set backward two digits (I-V). They were named as Sarcotherichnus enigmaticus and attributed to canids or felids. Dehnaripus differs from Sarcotherichnus by larger size and unclear digit imprints, on the other hand, preservation quality of specimens of Dehnaripus is well, so that it shows even fine wrinkles. Aenigmatipodus Mayoral et al. (2023) comprises series of tracks that are grouped in sets of three tracks or triads, each track constituting a subunit of the whole set and consisting of a depression or cleft formed by a central body and two bodies placed at the ends ( Mayoral et al. 2023). Dehnaripus differs from Aenigmatipodus by its morphology, so that Dehnaripus is mound-shaped, with circular outline, and Aenigmatipodus, however, is a depression formed by a central body that is three times as long as it is wide, with two shorter bodies placed at the ends.

There are other non-biogenic mound shape structures, which may look similar to Dehnaripus ; for example, sand-volcano occurs on upper bedding surfaces, and result from liquefied sand being extruded through a local vent at the sediment surface ( Collinson and Mountney 2019). Sedimentary biogenic structures, such as stromatolites, have mound shapes on the carbonate platforms. Essentially, these structures differ from Dehnaripus , not only by their morphologies but also by their lithofacies. Although there are no complete and convincing trackways, we would rather consider Dehnaripus as a new ichnotaxon, because of:

The extramorphology of Dehnaripus is not the result of substrate conditions, because it was found in the different horizons of the lower rock units of LRF. It is difficult to conclude that the same extramorphologically conditions were repeated in different lithohorizons. On the other hand, the preservation of Dehnaripus is good so that fine wrinkles were preserved, which shows the unusual morphology of the sole of pes or manus.

The extramorphology of Dehnaripus is related to the unusual morphology of the sole of the track makers. In comparison, the pentadactyl toes of proboscideans, embedded by digital thick cushions and their broad sole, are flat and full of wrinkles. The impressions of these feet are large oval to subcircular imprints, with large and flat sole surfaces either ornamented or smooth. The digit impressions may point anteriorly ( Panin and Avram 1962; Neto de Carvalho et al. 2021). These footprints are completely different from the skeletal anatomy of proboscideans. Like this, Dehnaripus shows the morphology of the sole of the track maker as radial unorganized thick wrinkles. These ornamentations could be formed by thick, unorganized and disordered radial cushions or hooves.