(Bild: M. van Engelen)
Details of the paper
| Title | Ichnological evidence on the behaviour of mitrates: two trails associated with the Devonian mitrate Rhenocystis |
| Co-Author(s) | Richard P.S. Jefferies & Owen E. Sutcliffe |
| Year: | 2000 |
| Language: | English |
| Source: | Lethaia, 33, S. 1-12 |
| Keywords: | locomotion trails, mitrates, Rhenocystis latipedunculata, Hunsrück Slate, Natural History Museum, chordates, echinoderms |
| Summary: | In this paper a slab with four individuals of the mitrate Rhenocystis latipedunculata is described. Two of them have associated trails. The find is unique and scientifically important since the systematic position (Chordata or Echinodermata) and orientation of these animals are controversial. The trails indicate that, just before death, the mitrates were moving tail-first, pulled by the tails and with the flat dorsal surface of the head upwards. This favours the chordate interpretation of the mitrates, rather than either of two current echinoderm interpretations. |
| Reaction 1: | R.P.S. Jefferies and A.G. Jacobson firstly mention in their paper: 'An Episode in the Ancestry of Vertebrates: From Mitrate to Crown-Group Craniate' in the journal Integrative Biology, 1998, Volume 1, Issue 4, page 123, that by an extraordinary piece of luck and sharp eyesight, an individual of the German Devonian mitrate Rhenocystis has been found dead at the end of ist own locomotion trace. |
| Reaction 2: | The senior editor of the journal Nature, H. Gee, informs in Volume 407 dated 19 October 2000, pages 849 and 851 in the section news and views, under the title: 'Mitrates on the move', that this important find confirms Jefferies's opinion, that the mitrates have features, that we would usually associate with chordates or hemichordates. |
| Reaction 3: | The French authors B. Lefebvre and B. David have written a reply in Lethaia 34, 2001. They assert that the association between the body fossils of Rhenocystis and the trails on the same piece of rock could be accidental. |
| Reaction 4: | R.P.S. Jefferies, in the same part of Lethaia comments on their reply. According to him, firstly, the reply of Lefebvre and David merely emphasises the importance of the described specimen. He then gives a number of reasons which make the accidental nature of the association of body fossils and trails unlikely. |
| Reaction 5: | Gudo (2005; in his paper [Body plan and evolutionary trends in fossil echinoderms (Homalozoa, Blastoidea, Edrioasteroidea)] in Senkenbergiana lethaea, 85(1): 51) states, that for the reconstruction of the life habit of the Homalozoa must be assumed, and this is in agreement with some trails, which were found in association with such animals, that these animals were lying on the substrate with some of their flat sides and were moving with the stem. However, from engineering-anatomical point of view Homalozoa are a separate evolutionary line of echinoderms and not basal chordates. |
| Reaction 6: | Gudo & Dettmann (2005: [Hypotheses for the origin of echinoderms: summary and discussion], in Paläontologische Zeitschrift, volume 79(3): 316, 317) present the theories for the origin of echinoderms. In the case of the calcichordate-theory of Jefferies is stated, that firstly the rearward locomotion was explained by the fact that it is easier to pull as to push an asymmetrical body and that secondly, partly also functional-morphological approaches (like the ribs of the body, which grip the sediment) were used. |
| Reaction 7: | Lin et al. (2010) in their paper "Bioturbation in Burgess Shale-type Lagerstätten: Case study of trace fossil-body fossil association from the Kaili Biota (Cambrian Series 3), Guizhou, China" (Palaeogeography, Palaeoclimatology, Palaeoecology 292: 245-256) refer to the documented direct associations between echinoderms and trace fossils described by Sutcliffe et al. (2000). |
| Reaction 8: | Rahman & Lintz (2012) in their paper "Dehmicystis globulus, an enigmatic solute (Echinodermata) from the Lower Devonian Hunsrück Slate, Germany" (Paläontologische Zeitschrift 86(1): 59-70) mention the very few cases, in which direct associations between ichnofossils and their echinoderm tracemakers have ever been reported. |
| Reaction 9: | Lefebvre (2003) cited Sutcliffe et al. (2000) twice in his paper "Functional morphology of stylophoran echinoderms", when discussing their possible mode of life (epibenthic or infaunal). |
| Reaction 10: | Sumrall et al. (2009) - in their paper: "Cardiocystella, a new cornute stylophoran from the Upper Cambrian Whipple Cave Formation, Eastern Nevada, USA" - identify the study of functional morphology, as in Sutcliffe et al. (2000), as one of the three main themes of research on stylophoran echinoderms. |
(Bild: M. van Engelen)
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