Trace fossil of the second III: Asteriacites lumbricalis

The Tfots today is Asteriacites lumbricalis von Schlotheim, 1820, a resting trace produced by the (in)activity of ophiuroid echinoderms or brittle stars (Twitchett & Wignall 1996). I took these photographs from material found on the slopes of Costabella mountain in the Dolomites. These slabs are float from an outcrop exposing the Campil Member of the middle Werfen Formation (Lower Triassic, Early Olenekian). These trace are quite widespread in this member and known for more than a hundred years although they were erroneously recognised as body fossils in the first place (e.g. Wittenburg 1908). They come from more or less storm-dominated shoreface deposits composed of micaceous fine-grained sandstones and siltstones.

Thanks to a comment by David, I hoped to see some decent specimens during the recent field session and finally I was really lucky finding these well-preserved traces at the last day of the campaign. I never saw better ones at least in the literature so far.

Fig. 1: Asteriacites lumbricalis preserved as convex hyporelief (positive structure on a lower bedding plane). Black bar represents 5 mm.

Fig. 2: Asteriacites lumbricalis preserved as concave epirelief (negative structure on an upper bedding plane). Black bar represents 5 mm. Note the ripple-marks.

References:

Schlothheim, E.F. von, 1820: Petrefactenkunde auf ihrem jetzigen Standpunktedes Thier- und Pflanzenreichs der Vorwelt. Gotha, Becker, 437 p. durch die Beschreibung seiner Sammlung versteinerter und fossiler überreste.

Twitchett, R.J., Wignall, P.B., 1996: Trace fossils and the aftermath of the Permo-Triassic mass extinction: evidence from northern Italy. Palaeogeography, Palaeoclimatology, Palaeoecology 124, 137–152.

Wittenburg, P. von, 1908: Beiträge zur Kenntnis der Werfener Schichten Südtirols. Geologische und Palaeontologische Abhandlungen 8, 251–289.

Trace fossil of the second II: Brutalichnus brutalis Mikuláš et. al 2006

Today I picked this one because of its adorable name. Brutalichnus has been erected by Mikuláš et. al 2006 with a bunch of other neat traces like Nihilichnus and Machichnus from bone material found in Miocene Sediments near Chomutov (Czech Republic). All of these structures represent biting and gnawing traces on bones. Brutalichnus brutalis is interpreted by the authors as breakage due to bites of animals in order to feed on cancellous bones which are rich in organic material. Evidence for this hypothesis is provided by small radial patterns at the points where the bone is broken. It proves that the bones did not simply collapse as a result of compaction.

Fig. 1: Brutalichnus brutalis on a mandible (Mikuláš et al. 2007).

Fig. 2: The suggested trace maker action being responsible for the observed morphology (Mikuláš et al. 2007)

Reference
Mikuláš R., Kadlecová E., Fejfar O., Dvořák Z. (2007): Three New Ichnogenera of Biting and Gnawing Traces on Reptilian and Mammalian Bones: A Case Study from the Miocene of the Czech Republic. Ichnos, 13, p. 113–127. link

To close this post you may enjoy the audio version of Brutalichnus brutalis: Converge's Fault and Fracture.

And now all together: Chirotherium is not an Archosaur!

Actually this one is not really important and I thought about publishing this post altogether. Although it is rather a popular problem than a scientific or academic one, it still teases me. You can find it everywhere: Newspaper, blogs and wikipedia for instance. Trackways of the ichnogenus Chirotherium are constantly mistaken for an Archosaur or related creatures.

For instance, the german Wikipedia article on Chirotherium: Fossilised footprint (ichnite) of the ichnogenus Chirotherium, an archosaur of the Lower Triassic, first found 1833 in Hildburghausen (Thuringia, Germany).

This is just wrong. An archosaur cannot be an ichnogenus.

Unfortunately, Chirotherium literally means something like "hand beast" or "hand animal". However, the term Chirotherium is scientifically used for a certain type of trackway(s), which is found in Sediments with a Triassic age, ranging from Olenikian to Anisian (KLEIN & HAUBOLD, 2007). In fact, Chirotherium is the first scientifically described trackway (KAUPP, 1835) and, by the form of the pes imprints (rear leg) resembling human hands, it animated the early palaeontologists imagination for the mysterious ancient beast that once left its trackway on the wet sand of the vast Triassic plain. In a way the "hand animal" is a chimera of those early days of palaeontological research. From a modern point of (ichno)taxonomic view, the scientific name Chirotherium, however, is attributed to the trace fossil only, although the trace maker most likely was an archosaur of some sort. Yes, you are right, this is scientific quibble but still; it is not correct.

Yours Ichnogeek!

Chirotherium (pes imprint) from the Triassic of Germany.


The "Chirotherium Monument" with a reconstructed "hand beast" (Hildburghausen, Germany)

References:

Kaup, J.J., 1835: Über Thierfährten bei Hildburghausen. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde. v. 1835, pp. 227-228.

Klein, H., Haubold, H., 2007: Archosaur footprints - potential for biochronolgy of Triassic contintal sequences. In Lucas, S.G., Spielmann, J.A., (eds): The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41.