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(^44) JOHN C. W. COPE
superfamily Modiolopsoidea Fischer, 1887, for-
merly often classified with the heteroconchs, but
shown by Carter & Seed (1998) to include some
taxa that display multiply inserted non-parivin-
cular ligaments; they may thus be related to the
pteriomorphs. In the Treatise (Cox el al. 1969)
the modiolopsoids are included in the order
Modiomorphoida and the superfamily Modio-
morphoidea. Fang & Morris (1997) revised the
taxonomy of this problematic superfamily and
showed that it included two distinct groups of
bivalves: the modiomorphoids, typified by
the Devonian genus Modiomorpha, had well-
developed ligamental nymphs that allowed
them to be distinguished from the Ordovician
modiolopsoids, a group with which they had
frequently been confused, but which lacked the
ligamental nymphs. Fang & Morris (1997) also
showed that the family Permophoridae Van de
Poel, 1959 was a subjective junior synonym of
the family Modiomorphidae Miller, 1877 and
recommended that order Modiomorphoida be
abandoned and that the superfamily Modiomor-
phoidea Miller, 1877, as used in the Treatise
(Cox et al. 1969), should be replaced by the
Modiolopsoidea Fischer, 1887, in which they
recognized the families Modiolopsidae Fischer,
1887, Colpomyidae Pojeta & Gilbert-Tomlinson,
1977 and the Modiolodontidae Fang & Morris,
1997. Carter & Seed (1998) showed that some
modiolopsoids had multiply inserted non-
parivincular ligaments and suggested that their
affinities thus lay with the pteriomorphs (see
above). The modiomorphoids, on the other
hand, possessed a periostracum with calcified
spicules and Carter & Aller (1975) suggested
that this feature, widely found in the anom-
alodesmatans, indicated that their affinities lay
with that group.
Modiolopsids are recorded as far back as
the Early Tremadoc of Argentina, whence
Harrington (1938) figured a form he described
as Cosmogoniophorina tenuicostata sp. nov.
Harrington figured three syntypes, two of which
(Harrington 1938, p1. 3, figs 1, 5) show an almost
carinate shell and one (Harrington 1938, fig. 1)
also shows clear radial ornamentation on the
post-umbilical shoulder. There appears to be
little quarrel that these are modiolopsids, but
I find myself in agreement with Pojeta
(1971, p. 17) that Harrington's other syntype
(Harrington 1938, p1. 3, fig. 4) appears to show
taxodont teeth, and a less marked post-umbonal
shoulder and apparently lacks radial ornamenta-
tion, suggesting this specimen is a nuculoid. To
clarify matters I designate the specimen figured
by Harrington (1938, p1. 4, fig. 1) as lectotype of
the species Goniophorina (Cosmogoniophorina)
tenuicostata (Harrington), 1938. The same
species has been recently recorded from the early
Middle Arenig of Argentina by Sanchez (1997b)
who noted that as Harrington did not describe
the dentition, the generic and subgeneric
assignments are uncertain.
The next oldest species are two species of
Modiolopsis from the Early Arenig of South
Wales (Cope 19966) where the modiolopsids
Cosmogoniophorina and Parallelodus also
occur. Middle Ordovician modiolopsids are
recorded possibly from Spain (Babin &
Gutierrez-Marco 1991, pp. 123-124), from the
Middle and Upper Ordovician of Argentina
(Sanchez 1990, 1999b) and the Upper Ordo-
vician of Laurentia (Pojeta 1971), Kazakhstania
(Khalfin 1958) and Siberia (Krasilova 1970.
1979). The genus Corallidomns appears in the
Upper Ordovician; this genus is noteworthy
because it is the first boring bivalve (as first
reported by Whitfield 1893) and lived in crypts
excavated into colonial corals or bryozoans;
the same mode of life was followed by
Semicorallidomus Isberg, 1934.
Colpomyids normally have rather amorphous
bulbous-shaped teeth, referred to as articulating
devices by Pojeta and Gilbert-Tomlinson (1977
p. 27), that are not mounted on a hinge-plate.
The earliest forms are from the Late Tremadoc
of the Amadeus Basin of Australia, Colpantvx
and Xestoconcha (Pojeta & Gilbert-Tomlinson
1977); the latter genus also occurs in the Early
Arenig of South Wales (Cope 1996b).
Colpomyids are known from the Upper
Ordovician of Laurentia (Pojeta 1978). Siberia
(Krasilova 1979) and western Gondwana
(Sanchez 1999b) and survived into the Silurian.
The Modiolodontidae are modiolopsoids that
have a small number of cardinal teeth in each
valve. They are known from the Middle and
Upper Ordovician and younger rocks. One of
the earliest is the Modioliodon recorded from
the Llanvirn of Avalonia by Cope (1999).
Anomalodesmata
The earliest generally accepted anomalodes-
matan is Arenigomya from the Early Arenig of
South Wales (Cope 19966). Arenigomya shows
already several of the principal characters of the
group, including a finely pustulate shell orna-
ment and an edentulous hinge that sometimes
carries subumbonal articulating devices (see
Cope 19966, p1. 7, figs 12-14; text-fig. 7). These
characters are evident in the genera Cuneamya
and Rhytimya (the latter also possesses a pos-
terior gape), both of which are known from the
Late Ordovician of the United States, Canada