The Probable Affinities of the Trace Fossil Diorygma Atrypophilia

Abstract

Modifications in the ultrastructure of the exoskeleton of the atrypid brachiopod Desquamatia subzonata Biernat indicate that, for the greater part of its life, it accommodated the trace fossil Diorygma atrypophilia Biernat. When these modifications are compared with the ultrastructure of the exoskeleton of Hemothiris psittacea (Gmelin), which has been attacked by a boring clionid sponge, it is evident that the ‘burrow’ occupied by Diorygma was not excavated by physical or chemical digestive processes, but fashioned by simultaneous growth of brachiopod shell and occupant. Because of its morphology and inferred habits Diorygma is best placed within the Phoronida.

Molecular evidence that phoronids are a subtaxon of brachiopods (Brachiopoda: Phoronata) and that genetic divergence of metazoan phyla began long before the early Cambrian

“…Typically, these inhabit a chitinous tube, which may be reinforced with mineral particles, packed into a dense lawn, or embedded in a substrate. About 12 extant species in two genera are recognised (Emig 1977a(Emig , 1979(Emig , 1982, and no ancient phoronid fossils are certainly known (Fenton and Fenton 1934;MacKinnon and Biernat 1970). Although the Lower Cambrian fossil Iotuba was originally described as a phoronid (Chen and Zhou 1997), this is now considered doubtful (Zhifei Zhang, pers.…”

Fossil Phoronida and their inferred ichnotaxa

“…The stylized reconstruction of a phoronid (Fig. 1b) proposed by MACKINNON & BIERNAT (1970) depicts a lophophore divided into two parts: the coils are anal and the tentacles at the mouth level are ventral, suggesting a double row of tentacles. In fact, the lophophore of all lophophorates (Phoronida, Bryozoa and Brachiopoda) has a single row of tentacles (EMIG, 1976(EMIG, , 1992 (Figs.…”

“…Finally, the interpretation of MACKINNON & BIERNAT (1970) does not apply to phoronids. Discussing the phoronid relationship to a rather similar structure in Eodiorygma BASSETT, POPOV et HOLMER, 2004, BASSETT et alii (2004 wrote: "in some groups are protected distally around the lophophore by a pair of collar folds (EMIG, 1979)", but this is a misinterpretation of the collar fold in Phoronopsis as originally described by GILCHRIST Nevertheless, among Recent marine groups there are several organisms, e.g., boring bivalve mollusks, capable of creating traces with a double aperture like those of the trace fossil Diorygma.…”

“…Each protuberance called Diorygma encloses two contiguous tubes interpreted by MACKINNON & BIERNAT (1970) as the separated anal and oral tubes of the U-shaped digestive tract of a phoronid. Actually, such a construction has never been described or proved to exist because it is impossible to do so anatomically.…”

Exploration of the Oxynoticeratidae ornamental morphospace using the discrete cosine transform (DCT) to analyze rib patterns

“…Additionally, even when preserved and detected, the quality of preservation will hamper examination and identifi− cation of such fossil parasitoses. In many cases, only faint traces of the parasite or the damage caused by it can be seen and not much, if anything at all, is known about the parasite it− self (e.g., MacKinnon and Biernat 1970;Welch 1976;Brett 1978;Conway Morris 1981Keupp 1986;Ruiz and Lindberg 1989;Underwood 1993;Bates and Loydell 2000;Lukševics et al 2009). In some other cases, fossil re− mains of invertebrate taxa are occasionally found that are commonly known to represent parasites today (e.g., Waloßek et al , 2006Maas and Waloßek 2001), but where the host is not preserved.…”