What Created These Permian Trace Fossil Footprints?

[Rick_Jo]

I came across these Permian 'diplichnite' trace fossil footprints. Can anyone shed some light on what could have created them?

I do not think they are horseshoe crab tracks, the Trilobite tracks that I could find look very different to these sharp pointed trace prints. I would have said my money was on some kind of crab but on further reading most crabs walk sideways. What other articulate could it be from?

[Terry Dactyll]

Arthropleura survived until the start of the permian so if it is early permian strata then based on the width tracks from a juvenile could be a possibility... The track photo's I have seen are a little less crisp than yours and perhaps the leg distances further apart but obviously smaller juveniles must of existed...Its quite a rare creature....

Heres a couple of bits I found on my travels...a leg and armour plates...

Google.... Arthropleura trackways

[Rick_Jo]

Thank you very much Terry, you sent me off on a lead.. Coming back with my findings I am thinking it is something in the order of Eurypterid (spiders) as opposed to Arthropleuridea (centipedes).

From what I can find other examples of Eurypterid have been found in Australia (although Arthropleuridea is well represented). One of my strongest leads is Hibbertopterus, found to the end of the Permian period (although not currently represented in this area or time so assumption based off similarities. "Hibbertopterus were sweep feeders, inhabiting freshwater swamps and rivers, feeding by raking through the soft sediment with blades on their anterior appendages to capture small invertebrates." which would suit the environmental conditions better.

In one photo example:

the tracks can be seen with that of glossoptris leaf fossils embedded in the same bedding plane, along side that of drop stones (not pictured). From papers these were ether deposited locally by seasonal ice melts or annual glaciation. Other fossil of the area represented further south (50km) and at the same time period such as the diverse Eurydesma Fauna would suggest the tracks came from something that could survive a cold climate as a sweep feeder or macro scavenger either amongst leaf litter or swampy - silty deltas.

Something similar to Hibbertopterus from the order Eurypterid makes the most sense as the right contender. (However Hibbertopterus is from the swamps of Scotland during the Carboniferous.)

For curiosity my second contender is Xiphosura (horseshoe crab) however I can find little information on the family Limulidae to be able to make a judgement. The fossil tracks that I have found of Limulidae or Xiphosura indicate that the opisthosoma (tale) would have dragged along in the sand. (Although a smaller opisthosoma persumably may have existed.)

So I think I am looking for something in the Merostomata Class most likely in the Eurypterid order that walked with its tale held off the ground similar to that of Hibbertopterus.

Anyone have any ideas on a contender or a better 'order' fit?

[Auspex]

Do you know, or can you deduce/speculate on, the depositional environment of the horizon in which your tracks were made?

[Terry Dactyll]

Looking at the material and trackways online of Hibbertopterus, the tail dragway is even more distinct than the Xiphosura... In a fine sediment like you have there preserving detail there should be some signs of this Ider thought...

[Rick_Jo]

Thank you both for your comments.

I am not completely sure Auspex of the exact depositional environment (only recently started learning about stratigraphy) but it appears to be transitional, shallow tidal marine environment.

Yes on close inspection Terry it looks like you are right, Hibbertopterus tail dragway is present.

Have you seen any examples of Xiphosura tracks that are similar to these? or can you think of anything else that I could pursue in terms of a contender for the tracks that would suit a cold Permian environment?

[Terry Dactyll]

Rick_Jo.....I did see some Xiphosura resting places somewhere once but I cant recall any distinct trackways....If you find anything please add them to the thread.... The parallel nature of your trackway indicates all the legs were aligned?... is what made me think of Arthropleura....

[mstimson29]

I have looked at hundreds of Xiphosuran tracks... these are not them. Nor are they Arthropleurid. the impressions are too regular and well spaced and too small by comparison to the trackway width. Underprints have a very different form for both of these ichnogenera.

Being an underprint for sure, it is difficult to deduce the original trackmaker. That is ... if this is a walkign trace at all. there is a 3rd identical trace that is not in line with the obvious 2 "trackrows" This might be plant in origin that has left a deep impression in the sediment ( Walchia for example). Hard to say but cant be ruled out.

M

[Taogan]

Have you eliminated decapods? Lobsters and the like walk in a straight line, don't always leave tail drags and have long enough and few enough legs so they don't blur the track like some of the other candidates.

[izak_]

Cool! Where did you find them?