Taxonomic review of the ichnogenusHelminthopsisHeer 1877 with a statistical analysis of selected ichnospecies

Abstract

The ichnogenus Helminthopsis Heer 1877 is a relatively simple, unbranched, horizontal, internally unstructured, pre-or postdepositional burrow, or trail, that follows an irregularly sinuous or more commonly an irregularly winding or meandering course. The geometric variation in course, its most significant ichnotaxobase, is invariably complex and has resulted in considerable taxonomic disorder, particularly at the ichnospecific rank. This confusion is compounded by the fact that no diagnoses, and, or, detailed descriptions of several of its historically defined ichnospecies were provided and for other ichnospecies such considerations are ambiguous.In view of these problems, the validity of the 21 previously described ichnospecies is reviewed and each taxonomically reassessed. We suggest that of these ichnospecies, H. regularte Crimes and Crossley 1991 is best regarded as a synonym of Cochlichnus anguineus Hitchcock 1858; H. irregularis (Schafhäutl 1851), H. antigua Sacco 1888 and H. curvala (Katto 1960) are synonyms of Helminthoida crassa Schafhäutl 1851; H. tunluensis Yang 1986 and H. yushuensis Yang 1986 are synonyms of Helminthoida miocenica Sacco 1886; H. akkesiensis (Minato and Suyama 1949) is a synonym of Helminthoida cf. miocenica; H. sinuosa Azpeitia Moros 1933 is a synonym of Cosmorhaphe sinuosa (Azpeitia Moros 1933); H. involuta Stefani 1895 and H. concentrica Azpeitia Moros 1933 are synonyms of Spirorhaphe involuta (Stefani 1895); H. horizontalis (Kern 1978) is a synonym of Phycosiphon incertum Fischer-Ooster 1858; H. magna Heer 1877 and H. intermedia Heer 1877 are synonyms of Scolicia Quatrefages 1849, namely Scolicia plana Książkiewicz 1970 or Scolicia prisca Quatrefages 1849 for the former and S. prisca the latter; H. barbeyana Stefani 1895 and H. labyrinthica Heer 1877 are. best considered nomina nulla and H. toyoensis Katto 1964 and H. sigmoideus Wang 1989 are nomina dubia. Of the remaining 4 ichnospecies of Helminthopsis, H. granulata Książkiewicz 1968 is easily and readily distinguished by its external granulate or tuberculate ornamentation. However, H. abeli Książkiewicz 1977, H. hieroglyphica Heer in Maillard 1887 and H. tenuis Książkiewicz 1968 cannot easily be differentiated. For these more problematic ichnospecies, a frequency component analysis using a FORTRAN program to perform a Fourier transform algorithm was applied in an attempt to statistically assess their validity or otherwise. The results suggest that H. tenuis is best considered a synonym of H. abeli, whereas H. hieroglyphica, although historically poorly defined, should still be regarded as a valid ichnospecies.Thus, we believe that of the many ichnospecies previously assigned to Helminthopsis, only 3, namely H. abeli, H. granulata and H. hieroglyphica, can be regarded as taxonomically valid and useful forms. H. granulata is characterized by its external ornamentation and the precise nature of its irregular course is not an essential ichnotaxobase. H. abeli should be adopted for irregularly meandering Helminthopsis that do not e...

The Gerola Valley site (Orobic Basin, Northern Italy): A key for understanding late Early Permian tetrapod ichnofaunas

“…The material displays slightly meandering to straight trails that are low amplitude, smooth, lacking ornamentations and self-overcrossing, and 1-2 mm wide. These are typical features of Helminthopis hieroglyphica Wetzel andBromley, 1996 (Han andPickerill, 1995;Wetzel and Bromley, 1996). These trace fossils are regarded as grazing trails of insect larvae or nematodes (Buatois et al, 1998).…”

A predatory Rusophycus burrow from the Cambrian of southern New Brunswick, eastern Canada

“…As discussed by , however, a surficial origin can in certain examples be equally plausible, particularly those demonstrating rheotactic orientation. With the particular example o f Rusophycus documented herein, however, an intrastrated origin appears unequivocal as the specimen is intimately associated with and clearly intersects and post-dates the infaunally produced burrow o f Helminthopsis hieroglyphica, the latter a product o f a worm-like organism, most likely a polychaete annelid (see Han and Pickerill 1995;Wetzel and Bromley 1996), H. hieroglyphica was clearly produced infaunally as it is now preserved essentially in positive epirelief, a preservational style inconsistent with a surficial origin. It appears likely, therefore, that at the time o f its production the annelid was deposit feeding along a mud-sand interface, now represented by only the upper surface o f the amalgamated quartz arenite.…”

“…It comprises a composite ichnotaxon (sensu Pickerill 1994) consisting o f the arthropod-produced (trilobite) impression Rusophycus isp. superimposed on the annelidproduced (see Han and Pickerill 1995;Wetzel and Bromley 1996) straight segments, is 8 -12 mm wide and extends 15 mm from the anterior and axial end o f the rusophycid for a total distance o f approximately 150 mm. It is preserved essentially in positive relief though small segments are preserved in negative epirelief.…”

The stratigraphic significance of trace fossils from the Lower Paleozoic Baskahegan Lake Formation near Woodstock, west-central New Brunswick

“…Rem arks: Recent discussion on Helminthopsis and its many historically defined ichnospecies has been presented by Han and Pickerill (1995), Wetzel and Bromley (1996) and Uchman (1998). Despite the slightly conflicting conclusions of these authors regarding its taxonomically valid and useful ichnospecies, all were in agreement that H. hieroglyphica is characterized by broad and low amplitude, irregular meanders interspersed with straight segments, a conclusion also supported herein.…”