Platykopus stuartjohnstoni Lucas & Schultz, 2007

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

Ichnospecies Platykopus stuartjohnstoni Lucas & Schultz, 2007

Fig. 9

Materials.

Three footprints of a trackway, molded by plaster ( IFMI -687 / 1-3) .

Diagnosis.

Footprints of an ursid that differ from Platykopus ilycalcator in having: manus narrower than pes, clear separation of metatarsal / metacarpal pads from digital pads, digits II-V of subequal size on the pes, metatarsal pad on pes wide and short and only four pes digit imprints.

Description.

Three footprints of a trackway were poorly preserved as concave epireliefs on the upper bedding plane of dislocated, thick bedded large sandstone slab. Imprints of pes and manus are not distinguishable and it seems that one set of footprints of the trackway has been preserved. The first footprint is circular in outline, and no digit imprints are visible (Fig. 9 B, D ). Footprint 2 includes five-digit imprints that are visible in the 3 D image as short and having sharp tips. Metatarsal imprint is short and has a straight proximal outline (Fig. 9 E – G ). The third footprint shows round, small digit imprints without a claw imprint and includes a circular outline in the metatarsal imprint (Fig. 9 H – J ).

Discussion.

Platykopus has been attributed to large trackmakers such as Amphicyonidae or Ursidae by its main feature as large plantigrade footprints, with all five digits, close to the manual / pedial pad. Dietrich (2011) named the large cave bear footprints Ursichnus europaeus and noted that Ursichnus have all digital pads spaced from the metatarsal / metapodial imprints, as an anatomical feature and differs from Platykopus. Platykopus includes three ichnospecies: P. ilycalcator Sarjeant et al. (2002) (type ichnospecies of the ichnogenus; Late Miocene, Nevada USA), P. stuartjohnstoni Lucas and Schultz (2007) (Upper Miocene, Texas, USA), and P. maxima ( Kordos, 1985) (Miocene, Hungary, new combination by Botfalvai et al. 2023). The studied footprints from the Deh Nar area show triangular digit imprints without distinct claws in the tips of digits; this indicates a difference from P. ilycalcator and P. maxima . These imprints are closely similar to P. stuartjohnstoni . Usually, Platykopus was preserved as pentadactyl imprints, and the type materials of P. stuartjohnstoni is tetradactyl. Lucas and Schultz (2007) believed that tetradactyly of P. stuartjohnstoni is an extramorphological feature that may reflect either an extremely small pes digit I or a walking pattern in which digit I was not impressed. The studied footprints of Deh Nar are poorly preserved and the pes and manus imprint are not distinguishable.

Figures

Figure 9. Platykopus stuartjohnstoni in the studied slab (A), and closeup view of footprints (B, E, H), with photos of plaster molds (C, F, I IFMI - 687 / 1-3) and photogrammetric false-color depth maps (D, G, J).