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Probable root structures and associated trace fossils from the Lower Pleistocene calcarenites of Favignana Island, southern Italy... 753

Fig. 9. ?Egadiradixus rectibrachiatus sp. nov. in Lower Pleistocene
calcarenites, Frascia, S of cemetery, site 3

?Skolithos-like and Macanopsis-like specimens below the first (1st d)
and second (2nd d) discontinuities

Root mats
(Fig. 10)

D e s c r i p t i o n. – Tubular, slightly winding, branched,
unlined or thinly lined structures built of calcium carbonate,
1–5 mm wide (Fig. 10A, B) or 2–5 mm wide (Fig. 10C). The
branches are of smaller dimension than the master tunnels.
Commonly, they overlap and form a dense, irregular network.

R e m a r k s. – The root mats belong probably to small
shrubs, as are currently common in the island. They occur on
several erosional or lamination surfaces, most of which are
younger (Tyrrhenian and younger) than the structures de-
scribed.

ASSOCIATED ANIMAL TRACE FOSSILS

Faviradixus robustus co-occurs with Ophiomorpha Fig. 10. Root mats
nodosa, Ophiomorpha isp., Thalassinoides isp., and
Beaconites isp. No animal trace fossils are associated with A – ?Tyrrhenian surface covered with root mats, Lido Burrone; B – closer
Egadiradixus rectibrachiatus, except for tubular forms that view of the specimen NGUJ183P9, Lido Burrone; C – ?Tyrrhenian surface
could be interpreted as Skolithos isp., which is a common trace covered with root mats; Frascia, S of cemetery, near site 3
fossil in high-energy shallow marine deposits. But more proba-
bly these tubular forms represent incomplete E. Ophiomorpha nodosa is produced mostly by callianassid
rectibrachiatus, as they penetrate from the same surfaces, and shrimps (Frey et al., 1978; Ekdale, 1992). It is most typical of
display the same size parameters and mode of preservation. the Skolithos ichnofacies (Frey and Seilacher, 1980; Pemberton
et al., 2001), but also occurs in deeper shelf tempestites (Frey,
Ophiomorpha nodosa Lundgren, 1891 (Fig. 11A, C) is a 1990; Frey and Goldring, 1992).
common trace fossil in shallow marine deposits. It forms a sys-
tem of vertical, oblique and horizontal tubular burrows, the Exceptionally large Ophiomorpha isp. (Fig. 11B), 52 mm
wall of which consists predominantly of dense, regularly dis- in diameter, was exposed as an unbranched horizontal segment.
tributed discoid, ovoid or irregular polygonal pellets (see Frey Pellets in its wall are more or less oval. This trace fossil is rare.
et al., 1978). The tube is 8–35 mm, mostly 19–30 mm, in exte-
rior diameter. The pellets are up to 8 mm long and 5 mm wide.
Commonly the pellets are elongated perpendicular to the bur-
row axis. The segments between branching points are straight
to slightly curved or winding, up to 60 cm long. The branches
are Y- or T-shaped. The branch junctions are slightly enlarged.