Longest recorded fossil drag mark

by Philip Robinson

A remarkable drag mark, 8.5 m (28 ft) long, has been located in the renowned Solnhofen Limestone deposit, Germany.1 The drag mark belongs to an ammonite, Subplanites rueppellianus, which was located embedded in the limestone at the end of this trace fossil. Ammonites are extinct squid-like creatures with a characteristic spiral chambered shell.

Fig 1. The entire drag mark created by the drifting shell of a dead ammonite (Subplanites rueppellianus), with close-up of several portions. A. The first portion of the drag mark clearly showing two prominent ridges. B. Drag mark showing two prominent ridges with additional faint ridges. C. Drag mark showing four prominent ridges and a gentle curve. D. Drag mark showing numerous prominent ridges, along with the ammonite. Large scale measures 1 m. Small scales measure 10 cm. See reference 1 for source.

The fossil is perhaps one of the most unlikely of fossils to have ever been preserved, let alone be discovered

Trace fossils previously located in the limestone at Solnhofen include those of a horseshoe crab,2 crustaceans, and fish. The largely straight drag mark consists of parallel ridges with a single furrow, but a number of times additional ridges can be observed, created by the ‘ribs’ of the ammonite’s shell. The drag marks appear to have been made by the ammonite as it was carried along by a shallow wave making contact with the fresh sediment surface before coming to rest.

Fig 2. The ammonite Subplanites rueppellianus, the producer of the drag mark. The shell is approximately 10cm across.

The paper’s authors think the ammonite was already dead, as it was missing the aptychus (a part of its body thought by many to be a jaw-piece). If they are correct then this “… represents the hitherto longest fossil drag mark created by a dead animal, complete with the animal preserved at the end”.1 Such a drag mark would not wait for any great period of time before being eroded away, and would need to have been covered by rapid sedimentation to be preserved. Solnhofen, known also for the fossils of the famous Archaeopteryx, has revealed a number of other breathtaking fossils that similarly do not fit with a millions-of-years framework and slow deposition.3

Dean Lomax, University of Manchester, who led the research, declared, “The fossil is perhaps one of the most unlikely of fossils to have ever been preserved, let alone be discovered”, adding that it “provides a snapshot of a moment that is captured in time—it really tells a story.”4 Yes, but that story is not one of millions of years, rather it is the historical account of Noah’s Flood found in Genesis 6–9, which would have provided ready mechanisms for rapid burials such as this one.