A scolecodont is the jaw of a Polychaeta Annelida, a common type of fossil-producing segmented worm useful in invertebrate paleontology. Scolecodonts are common and diverse , which range from the Cambrian period (around half a billion years ago at the start of the Paleozoic era) to the Holocene. They diversified profusely in the Ordovician,
Relatedly, more problematic worm-like have been described in even older, Neoproterozoic era deposits in the Ediacaran Hills of southern Australia and in mid-Cambrian deposits of Burgess Shale in British Columbia.
Since the other classes of annelids (specifically, the and ) lack hard parts, only the sea-dwelling polychaetes are frequently represented in the fossil record. Polychaetes are commonly due to their teeth and their dwelling tubes made of durable calcite (a calcium carbonate), hardened mucus (a.k.a. parchment), and/or chitin-like cement.
Taxonomy
Scolecodonts belonging to the
extinct families
Atraktoprionidae,
Hadoprionidae,
Kalloprionidae,
Mochtyellidae,
Paulinitidae,
Polychaetaspidae,
Ramphoprionidae,
Rhytiprionidae,
Skalenoprionidae, Symmetroprionidae,
Xanioprionidae, and the still-
Extant taxon (living) family
Oenonidae (which includes the Arabellidae) are known from
Silurian rocks in Scotland. Scolecodonts representing the present-day families
Onuphidae and
Dorvilleidae first appeared in
Mesozoic era deposits.
History
Segments of the fossil jaw of a polychaete worm were first reported from Silurian strata on the Estonian island of
Saaremaa in 1854,
[EICHWALD, E. 1854. Die Grauwackenschichten von Lieu-und Esthland. Bulletin de la Société Impériale des Naturalistes de Moscou, 27, 1–111.] but they were misinterpreted as fish teeth. A year later, impressions of whole polychaete worms with poorly preserved jaws were described from Italian Tertiary deposits.
[MASSALONGO, A. 1855. Monografica delle Nereidi fossili del Monte Bolca. Antonelli, Verona, 55 pp.] Subsequently, E. Ehlers, a specialist on recent polychaetes, recorded them from the Jurassic Solenhofen Stone of Bavaria, Germany, demonstrating their affinity and proposing the generic names
Eunicites and
Lumbriconereites.
[EHLERS, E. 1868a. 12Iber eine fossile Funicee aus Solenhofen (Eunicites aritus), nebst Bemerkungenvtiber fossile Wtirmer tiberhaupt. Zeitschrifl ftir wissenschaftliche Zoologie, 18, 421–443.][EHLERS, E. 1868b. Ueber fossiler Würmer aus dem lithographischen Schiefer in Bayern. Palaeontographica, 17, 145–175.] Extensive studies in the late 19th century by George J. Hinde of material from England, Wales, Canada and Sweden
[HINDE, G. J. 1879. On annelid jaws from the Cambro-Silurian, Silurian and Devonian Formations in Canada and from the Lower Carboniferous in Scotland. Quarterly Journal of the Geological Society of London, 35, 370–389.][HINDE, G. J. 1880. On annelid jaws from the Wenlock and Ludlow Formations of the west of England. Quarterly Journal of the Geological Society of London, 36, 368–378.][HINDE, G. J. 1882. On annelid remains from the Silurian strata of the Isle of Gotland. Geologiska Föreningen i Stockholm Förhandlingar, 6(6): 254–255.][HINDE, G. J. 1896. On the jaw-apparatus of an annelid ( Eunicites reidiae sp. nov.) from the Lower Carboniferous of Halkin Mountain, Flintshire. Quarterly Journal of the Geological Society of London, 52, 438–450.] established a basis for the nomenclature of what he regarded as isolated components of annelid jaws; but study of them lapsed thereafter for almost 50 years.
External links
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scolecodonts.net including complete scientific bibliography, lists of fossil genera and species, and selection of images
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graptolite.net Piotr Mierzejewski's page on microfossils
