The origin of the Phoronida, certainly monophyletic with the other Lophophorata, goes back to approximately 800-1000 MA. Though as fossils, the phoronids are known since the Devonian (the brachiopods from the Cambrian and the bryozoans from the Ordovician): they have preserved the ancestral form and life way, nearly to those of the predecessor protolophophorate (Emig, 1984).

Several authors suggested that tubes or tubicolous burrows in fossil records, described under various ichnogenera, i.e. Skolithos, Talpina, Diorygma..., belong to Phoronida (Fenton & Fenton, 1934; Avnimelech, 1955; Josey, 1959; Voigt, 1972; Mackinnon and Biernat, 1970; Sokoloski, 2005). Recently, Voigt (1975) has proved the identity of Phoronis species with the ichnogenus Talpina von Hagenow, 1840, confirmed in 1978. He also demonstrated (Voigt, 1972) that Conchotrema Teichert 1945 is a junior synonym of Talpina, as was confirmed by Plewes (1996).

Talpina is abundant today and is well known from the Cretaceous (Voigt, 1972) and Jurassic (Fürsich et al., 1994). The ichnogenus ranges back to the Late Devonian (Thomas, 1911; Rodriguez & Gutschick, 1970; see Bromley, 2004). The fossil phoronid burrows seem to have been present since Devonian times (see Emig, 1982).

The Talpina burrowed in such diverse calcareous substrata as calcareous algae, echinids, mollusc shells and rostra of Belemnites. Voigt gives criteria used for the discrimination of the phoronid burrows from other similar ones such as those of Thallophytes, sponges, Bryozoa or "worms". The frequent presence of agglutinating Foraminifera surrounding the opening the tube of a worm-like fossil animal provisionally determined as Phoronopsis and suggesting commensalisms between both fossil organisms (Voigt, 1970) in Upper Maastrichtian, has never been confirmed in recent observations on Phoronida. Tubes of the ichnogenus Talpina ramosa which occur frequently within the guards of Belemnella and Belemnitella (cf. Voigt, 1972) are described within the cavities probably originating from diagenetically destroyed aragonitic corals of the Maastrichtian chalk-tuff (Voigt, 1978).

Towe (1978) and Larsson (1979) raised the possibility that Tentaculites were related to the brachiopods or perhaps more closely to the phoronids. However, the later author noted that the lophophorate feeding system of phoronids is incompatible with the planktonic mode of life proposed for some tentaculitids. Vinn (2005) and Vinn & Mutvei (2005) hypothesized that phoronids were perhaps the closest living relatives of Cornulites and Tentaculites, , but also the brachiopods or the bryozoans (Vinn & Isakar, 2007). Nevertheless, to reconstruct cornulitids as 'skeletal phoronids' is entirely speculative. The only two groups with which Cornulites can be compared directly are bryozoans, and cnidarians with which comparable morphologies and shell structures are found (Herringshaw et al., 2007).

Iotuba chengjiangensis, a form known from three speciemens from the Lower Cambrian Chengjiang fauna of China, has been interpreted by Chen & Zhou (1997) as a phoronid, having a U-shaped gut and is tentaculated. In the same fauna, another soft-bodied fossil has been claimed to be phoronid, Eophoronis, by Chen (2004). But the affinities of these fossils have been questioned (Cohen & Weydmann, 2005), and according to Conway Morris (2006) and Huang (2006), they may be priapulids.

There is a tendency in the recent work to attribute ichno-tubes to fossil phoronid (see recent references) without any comparison the real structure and chemical composition of the characteristic tube of the Phoronida. Moreover, it seems curious to propose a phyletic tree base upon ichno-tubes hypothetically attributed to Phoronida (see Skovsted et al., 2008). A short review has been proposed by Emig (2010).

Fig. - Molecular divergence estimates for brachiopods and phoronids (from Sperling et al., 2011, modified).

According to these authors, the mean age for the divergence along the Brachiopoda between the Linguliformea and Rhynchonel-liformea is 547 Ma, while that between brachiopods and phoronids is at 578 Ma. However, on the basis of the morpho-anatomical characters, we have estimated this latter divergence much earlier (Emig, 2008). The tree on the figure confirms the presence of three main phoronid groups as stated and described by Emig (1985).

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Fossil Phoronida and their inferred ichnotaxa    

Tribulations d’un manuscrit... de Lethaia à Acta Palaeontologica Polonica.  
Tribulations of a manuscript... from Lethaia to Acta Palaeontologica Polonica.