Anapachydiscus fresvillensis Seunes 1890 from: Kennedy, W.J.. (1986): The ammonite fauna of the Calcaire à Baculites (Upper Maastrichtian) of the Cotentin Peninsula (Manche, France) . Palaeontology Vol. 29(1) p. 25-83
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Species Anapachydiscus fresvillensis Seunes 1890
|Diagnosis / Definition:
Description. All specimens studied are internal moulds ofmacroconeh phragmoeones, 67-148 mm in diameter. Coiling involute, umbilieus eomprising 19•8-22•4% of diameter with 60% of previous whorl covered. Whorl section depressed, reniform in juvenile (breadth to height ratio up to 1-12) with greatest breadth at umbilical shoulder, umbilical wall rounded and undercut, inner flank rounded, outer converging to broadly rounded venter. Whorl breadth to height ratio decreases through ontogeny and section is slightly compressed from 120-130 mm diameter. Up to 60-65 mm (PI. 9, figs. 1-3), ten or eleven low, broad ribs arise at umbilical seam and develop into prominent umbilical bullae. These give rise to paired (rarely three) ribs, while occasional non-tuberculate ribs arise at shoulder and shorter intercalatories arise on inner flank to give a total of thirty-one or thirty-two ribs per whorI. These are narrow and prorsiradiate on inner flank at smatlest diameter visible, curve forwards over ventrolateral shoulder and cross venter in broad convexity, attenuating and effacing over mid¬venter. As size increases (pI. 8) ribs strengthen and are strongest over venter by a diameter of 50 mm. Bullae decline beyond 60-65 mm and migrate out to inner flank position (PI. 8, fig. 2), giving rise to pairs of ribs with, in addition, both long and short intercalatories that strengthen markedly over venter; there are forty ribs at 115 mm. Umbilical bullae decline beyond 120 mm and ribs progressively efface on inner and middle flank so that, by largest diameter seen in the present material (the lectotype; PI. 7), ornament is confined to coarse, broadly convex, rounded ribs, forty per whorl, on ventrolateral shoulders and venter only, with smooth flanks on mould at least.
The suture (text-fig, 4A) is finely subdivided.
Ward & Kennedy (1993):
All specimens crushed, and original whorl section
cannot be reconstructed. Coiling very involute with small
umbilicus comprising around 20 percent of diameter. Whorls
high, expanding rapidly; in juveniles to diameter of 60-70 mm,
estimated 10-1 1 ribs per whorl arise at umbilical seam and strengthen into large conical tubercles perched on umbilical
shoulder. These are flat topped and were septate bases of umbilical
spines, occasionally visible on external molds in field.
Tubercles give rise to one or two narrow, sharp, distant primary
ribs, straight and prorsiradiate on inner to mid-flank, where
occasional short ribs intercalate, to give a total of 30-32 ribs
per whorl. Ribs flex forward on ventrolateral shoulder and
strengthen, crossing venter in broad convexity. As size increases,
umbilical tubercles weaken and migrate out to inner flank position.
They give rise to pairs of ribs, with both long and short
intercalatories that are weak on mid-flank but strengthen markedly
on outer flank and venter where they are narrow, rounded, and separated by wide interspaces, totalling up to 23 per half
whorl. Beyond 120-140 mm diameter, bullae decline, as does
inner flank ornament, so that large specimens have coarse distant
concave ribs on ventrolateral shoulders that cross venter
in broad convexity. Adult specimens up to 300 mm in diameter,
and may have up to 50 ventral ribs.
|Discussion / Comments:
Discussion. Massive whorls, depressed and with strong umbilical bullae giving rise to groups of ribs, plus the effacement of ornament on all but the ventrolateral shoulders and venter in rniddle growth readily distinguish macroconch A. [resvillensis from the other pachydiscids present in the Ca1caire a Baculites. Most workers refer the species to Pachydiscus, but the massive, involute whorls and the presence of umbilical spines and tubercules giving rise to paired ribs suggest it is better placed in Anapachydiscus. Of the European species, the present form has generally been confused with P. colligatus (Binkhorst, 1861). This species is discussed at length elsewhere in my revision of the ammonites of the type Maastrichtian (in prep.). Suffice it to say that the proposed lectotype (the original of Binkhorst 1861, pI. 8, which is also the holotype by monotypy of P. vandenbroecki de Grossouvre, 1894, p. 207) is a much less massive shell, more evolute, and slower expanding; moreover, on moulds, the primary ribs extend to the umbilical shoulder and the secondaries extend weIl down the flank at a diameter where they have disappeared in P. (P.) [resvillensis, while the ventral ribbing is much more subdued in middle growth. The smallest topotype of P. (P.) colligatus seen is over 200 mm in diameter, so that comparison ofthe early stages is difficult, The reader is referred to the revision ofthe Maastricht fauna noted above for additional discussion. P. quiriquinae Steimnann, 1895 (p. 74, pI. 6, fig. 3; text-fig. 5) from the Upper Maastrichtian of Quiriquina Island, Chile (lectotype, here designated, the original ofSteimnann 1895, pI. 6, fig. 3) has the following dimensions (after Steinmann): The style of ornament is identical to that of A. fresvillensis, and there are, according to Steimnann, eleven umbilical tubercles and forty to forty-five ventral ribs as opposed to thirteen to fifteen umbilical tubercIes and forty-eight ventral ribs in [resvillensis. An exarnination of the lectotype of fresvillensis shows identical ornament in both form and density, although the lectotype of quiriquinae is more compressed (Wb: Wh ratio is 0.77 vs. 0,94). I regard them as conspecific.
P. supremus Pethö, 1906 (p. 88, pl. 5, fig. I) is also a macroconch fresvillensis; it is from the Maastrichtian ofFruska Gora, Yugoslavia. The sketchily figured Brazilian P. sumneri, P. poseidon, and Canadoceras riogramense of Maury (1930) may belong here, but they are scarcely recognizable from the figures; they are Maastrichtianin age. P. subrobustus (Seunes, 1891) (p. 15, pl. 13 (2), fig. 1) is immediately distinguished by its evolute coiling, coarse ribs, and lack of umbilical bullae/spines. A. wittekindi(Schlüter, 1872) (see Blaszkiewicz 1980, p. 50, pl, 42, figs. 1 and 2; pI. 43, fig. 2; pls, 44-47; pI. 48, figs. 3 and 4; pI. 49, figs. 1 and 3; pI. 50, figs. 2 and 3; pls. 51-53) and A. vistulensis Blaszkiewicz, 1980 (p. 48, pI. 42, figs. 3 and 4; pI. 43, figs. land 3; pI. 48, figs. 1 and 2) both have much more coarsely ribbed nuclei than the present form, while P. wittekindi has a middle feebly ribbed and an adult strongly ribbed growth stage and P. vistulensis a strongly ribbed adult stage, all features which
immediately distinguish them from the present species. •
P. auritocostatus of Seunes (1890b, p. 239, pI. 8, fig. 4) non Schlüter, a diminutive bituberculate form that occurs with A. fresvillensis at the Carriere des Bernes between Gan and Rebenacq in the Pyrenees-Atlantiques, may be the rnicroconch of this species; I have, however, failed to locate the original specimen and can do no more than suggest the possibility
Ward & Kennedy (1993):
Lectotype, designated by-Kennedy, 1986c, p. 44, is
No. A1 186 in the collections of the Ecole des Mines, Paris, now
in the collections of the Université Claude-Bernard, Lyon, the
original of Seunes, 1980a, p. 3, Pl. 2(1), fig. 1, from the Calcaire
21 Baculites of Fresville, Manche, France (Figure 36.1, 36.2).
The lectotype is an internal mold (Figure 36.1,
36.2), and ornament is relatively subdued. External molds from
the Maastricht area (Kennedy, 1987, Pl. 10, figs. 1-3, Pl. 23,
fig. 5) show the strong umbilical spines that indicate fresvillensis
to be an Anapachydiscus, as well as sharp distant ribs like those
seen on the composite molds from the Biscay sections. Stinnesbeck
(1986, p. 221, Pl. 14, fig. 1, Pl. 16, fig. 1, text-fig. 28b)
has recently redescribed material from central Chile as Anapachydiscus
fresvillenis quiriquinae (Steinmann, 1895). For reasons
outlined by Kennedy (1986c, 1987), we regard this as a
synonym of A. fresvillensis sensu stricto. Through the kindness
of Professor A. A. Atabekian (Leningrad) we have been able to
study casts of species described by Atabekian and Akopian
(1 969). Pachydiscus colligatus michailovi Atabekian and Akopian,
1969 (p. 14, Pl. 5, fig. 2, Pl. 6, fig. 2, Pl. 7, figs. 1, 2) is
based on crushed composite molds of the present species, with
the same distant ribbing, and the flat-topped bases of septate spines clearly visible in some specimens (Figure 37.1-37.6). A
typical Armenian example referred to fresvillensis by these authors
is shown in Figure 38.1-38.3. Differences between A.fresvillensis
and European Campanian species of the genus are discussed
by Kennedy (1 986c, 1987) and do not require repetition
here. Sparse ribbing, umbilical spines, and massive shell form
immediately distinguish the species from all other Pachydiscus
described from the Biscay region. Anapachydiscus terminus n.
sp., described below, has a comparable gross morphology, but
is easily separated by the much finer, dense crowded ribs, up to
60 per whorl, that persist to up to 100 mm diameter, whereas
fresvillensis has around 40-45 ribs at this size, the ribs already
effaced on the middle of the flanks. Adults of both species show
a restriction of ribs to ventrolateral shoulders and venter.
In the Biscay sections this taxon ranges from
near the top of Member I (lower Maastrichtian) to low in Member
IV (upper Maastrichtian). Where well dated elsewhere, the
species is restricted to the upper Maastrichtian, with records
from Tercis, Landes, inland sections in Pyrénés-Atlantiques,
and Haute Garonne, the Calcaire à Baculites of the Cotentin
Peninsula, Manche, France; Limburg, the Netherlands, Denmark,
Yugoslavia, the Armenian SSR, southern India, Madagascar,
western Australia, Chile, and possibly Brazil.
Species Anapachydiscus fresvillensis
Species Anapachydiscus fresvillensis
1861 Ammonites colligatus Binkhorst. - Binkhorst
: 25 (pars) pl. 6, fig. 3a-f(?); pl. 7, fig. 2c; pl. 8, figs. 1 and 2
1894 Pachydiscus colligatus Binkhorst. - Grossouvre
: 202 (pars) pl. 24, figs. 1 and 3 only (non pl. 33, fig. 1)
1908 Pachydiscus colligatus Binkhorst. - Grossouvre
: p.28 pl. 4, figs. 1-3; pl. 5, fig. 1; pl. 6, fig. 1 sp. emend. de Gross
1930 Parapachydiscus sp. indet. Hyatt. - Wetzel : p.86 pl. 14, fig. 1
Ward & Kennedy (1993):
1987 Anapachydiscus fresvillensis Seunes. - Kennedy
: p.173 pl. 6;
pl. 7, fig. 1,2;
pl. 9, fig. 1, 2;
pl. 10, fig. 1-5;
pl. 11, fig. 5, 6;
pl. 12, fig. 12-14;
pl. 13, fig. 6, 7;
pl. 14, fig. 1-3, 7, 11, 12;
pl. 15, fig. 4-6;
pl. 23, fig. 5.
1993 Anapachydiscus fresvillensis Seunes. - Ward & Kennedy
: p. 41, 42, 43, 44, 4 fig. 35.3, 35.5, 35.6, 36.1, 36.2, 37.1-37.6,
38.1-38.3, 40.8, 45.1
|Was used in synonym list of:
|Stratigraphy - relative ages:
|upper Maastrichtian - Maastrichtian: Kennedy (1986)
upper Maastrichtian - lower Maastrichtian: Ward & Kennedy (1993)
|Collections of the Université Claude-Bernard - Lyon, Inventory number: No. A1186
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