Archosaur tracksite from Italy!

[Italo40]

Hello dear members, 

Today I'd like to talk about my latest fieldtrip, to the Late Triassic tracksite of Zone, Lombardy prealps, Italy. However, I'd like to make it clear that it involved no fossil collecting, because of the scientific interest of the site and of italian laws, that prevent (almost) any form of this activity. I know there is the "Fossil sites" section, but I thought that here my post would have reached more people. I apologize in case this is not allowed.

Let's not waste any more time! Italy is quite well know for its tracksites, in particular those bearing dinosaur tracks: Altamura (the largest tracksite in Europe!) and Lavini di Marco, just to give an example. On the other hand sites of Late Triassic age, bearing archosaurian footprints are poorly documented. 

Zone is a tiny village located nearby the Lake Iseo, in the Southern prealps, some 80 km (50 mi) east of Milan (see the red arrow on the map below). Back in the Late Triassic (Carnian) this area was an alluvial fan, characterized by a semiarid climate and, further to the south, by the occurrence of a series of volcanic edifices. Tracks are, in fact, preserved in terrigenous-volcaniclastic beds. Ripple marks and groove casts can be found too.

The material is represented by a total of about 70 footprints, arranged in six trackways on two different layers. The older displays three trackways that cross each other, the younger three distinct trackways. Footprints are only moderately preserved, nonetheless several anatomical details are evident on those of the younger level. In addition to traditional mapping methods, a laser scanner was employed to obtain high-quality 3D digital models. Let's talk about who left this footprints for us to admire! Those of the younger level are referred to a quadrupedal trackmaker with plantigrade, pentadactyl pes (distal portion of the hind limb) and manus (distal portion of the fore limb). They have been assigned to the ichnogenus Brachychirotherium, known by a global distribution and probably left by a crurotarsan archosaur. It is not clear whether it was a rauisuchian (predator) or an aetosaur (armored vegetarian).

On the field, I must admit that I was a little disappointed. Judging by the pictures published in the 2009 paper that described the outcrop, at least two trackways were quite distinct and visible. However, that was not the case: only 4 tracks (two manus and two pes) were indeed immediately identifiable. I guess that's possibly due to two factors: on the one hand weathering (the fine grained sandstone is very fragile), on the other hand inclination of solar rays. Tracks are best visible in raking light, but I visited at around 10-11 am in a clear February day. In the summer period I'm quite sure that much more could be seen!!

In order to highlight the footprints and compare with the presente state, I chose to show also a pictures taken from the paper: you can distinghuish it easily, because it is in b/w.

 

 

Today this is the best that you could ask for in this section (older layer)

 

 

The overall best preserved manus-pes track, in the younger layer.

 

 

Reconstruction of this set of footrprints

 

 

Close up of the Manus, scale bar is 5 cm (2 in). total lenght of the track: some 30 cm (11,8 in).

 

 

The second best preserved manus-pes association

 

 

Reconstruction of a rauisuchian (on the left) and an aetosaur (on the right). On top lower right digital model of the best preserved trackway (I showed you the picture of the first two sets of imprints).

 

 

A rauisuchian

 

The significance of the Zone tracksite is that it represents the first definite ichnological record of archosaur tracks found in Lombardy and footprints are among the best preserved, although an upcoming paper is going to feature recently found tracks that are even better preserved (and I gave my contribution in the excavation campaign!). 

On the field, I must admit that I was a little disappointed. Judging by the pictures published in the 2009 paper that described the outcrop, at least two trackways were quite distinct and visible. However, that was not the case: only 4 tracks (two manus and two pes) were indeed immediately identifiable. I guess that's possibly due to two factors: on the one hand weathering (the fine grained sandstone is very fragile), on the other hand inclination of solar rays. Tracks are best visible in raking light, but I visited at around 10-11 am in a clear February day. In the summer period I'm quite sure that much more could be seen!! Anyway, it was a great experience: easy access, few people walking by, great scientific value!

I hope that you liked my short report, 

Fabio

 

[Tidgy's Dad]

Thank you, Fabio, and indeed I enjoyed your excellent report and photos. 

It's a shame they're eroding away, but that's nature and hopefully others will be revealed by nature here, or elsewhere, in time. 

[FossilNerd]

Thanks for the very informative report! 

Wonder how they were able to walk on the side of the wall like that?  
 

Only joking... 

 

 

[JarrodB]

Nice trip report. Thanks

[Ash]

On 24/02/2020 at 2:28 AM, FossilNerd said:

Thanks for the very informative report! 

Wonder how they were able to walk on the side of the wall like that?  
 

Only joking... 

 

 

 

Ancestors to geckos?