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Species Pachydiscus (Pachydiscus) neubergicus Hauer 1858

[1] 4a-b Ifrim et al. (2005) [2] 4c Ifrim et al. (2005) [3] 5h Ifrim et al. (2005)

Alternative name:
Pachydiscus neubergicus Hauer 1858
Diagnosis / Definition:
Ifrim et al. (2005):
DESCRIPTION. The shell is moderately involute and expands at a moderate rate. The test is little compressed, with a WB/WH ratio of about 0.85. The umbilicus spans 29% of the diameter. The vertical umbilical wall arches widely into slightly convex and convergent flanks. Greatest whorl breadth is below mid-flank. The venter is widely rounded. The flanks display approximately six sigmoidal primary ribs per half whorl. The ribs are concave on the umbilical shoulders, rectiradiate on the dorsal flank, and they bend convexly backwards at mid-flank. They cross the ventrolateral shoulders in a wide concavity and weaken towards the venter. Up to a diameter of about 9 cm, the two ventrolateral secondary ribs are parallel to the primaries. At a diameter of 10 cm, the shell displays at least one secondarybetween each primary rib. At a shell diameter of 12 cm, the primary ribs flatten and become straighter on the outer flanks, while secondary ribs are more distant and seem to weaken. Unfortunately the shell is badly weathered and crushed in this part. The suture line is partially visible and corresponds to that of the genus.
FATMI & Kennedy (1999):
Description. -GSP 1046: crushed composite mold 80 mm in diameter, wholly septate, moderately involute, with U = 21 percent of diameter, umbilical wall low, umbilical shoulder more narrowly rounded, inner flanks feebly convex, outer flanks convergent, ventrolateral shoulders and venter broadly rounded. An estimated 12 primary ribs per whorl arise on umbilical wall and strengthen into narrow concave bullae on ventrolateral shoulder that give rise to single narrow, distant prorsiradiate ribs that may branch. Intercalated ribs arise on outer flank and all ribs strengthen across venter to give 25 ribs per half whorl at ventrolateral shoulder at greatest diameter preserved. Types. -Lectotype.. by the subsequent designation of de Grossouvre, 1894, p. 209, is the original of Hauer, 1858, p. 12, pl. 2, figs. 1, 2, no. 1858.01.6 in the collections of the Geologisches Bundesanstalt, Vienna. Three paralectotypes have the same inventory number; all of the types are from the Lower Maastrichtian of Neuberg, Steiermark, Austria.
Discussion / Comments:
Ifrim et al. (2005):
TYPE. The lectotype is GBA 1858.01.6, which comes from the Early Maastrichtian of Neuberg, Steiermark, Austria. It is the original of Hauer, 1858, pl. 2, figs. 1-3, by subsequent designation of Grossouvre, 1894, p. 209. The specimen was refigured by Kennedy and Summesberger, 1986, pl. 3, figs. 1-3, and Kennedy, 1986, pl. 4, fig. 3. Material. One deformed, weathered specimen from the base of the middle member of the Cárdenas Formation at the railway section east of Cárdenas. DISCUSSION. Pachydiscus (Pachydiscus) neubergicus Hauer from the Mexican Cárdenas Formation presents the slightly compressed whorl section of the type material of P. (P.) neubergicus (Hauer, 1858), although ornamentation is more typical of P. (P.) jacquoti Seunes (1891) with one or two ventrolateral rib between two moderately distant primary ribs. The type material of Pachydiscus (Pachydiscus) neubergicus is slightly compressed, with a WB/WH ratio between 0.72 and 0.78. Shape of its primary ribs corresponds to that observed in our specimen, with nine primary ribs per half whorl in the Mexican specimen and in the type material, but it differs in the higher number of secondary ribs: eighteen per half whorl in the lectotype, whereas thirteen are recognized in the last half whorl of the Mexican specimen (but at this diameter our specimen is larger than the lectotype). P. (P.) neubergicus is subdivided into two subspecies which differ in ornamentation of adult shells. See Henderson and McNamara (1985), Kennedy and Summesberger (1986), and Ward and Kennedy (1993) for discussion of subspecies. Pachydiscus (Pachydiscus) jacquoti Seunes is also similar. In this species, 10 to 12 primary ribs are present per whorl with one or two ventrolateral ribs, and ornamentation is comparable to that of our specimen. However, whorl section of the type material is considerably less compressed in P. (P.) jacquoti than in our specimen, and the WB/WH ratio of Pachydiscus (Pachydiscus) jacquoti is 0.95 to 1.20, compared to a WB/WH ratio of 0.85 in the Cárdenas specimen. None of the subspecies of Pachydiscus (Pachydiscus) jacquoti are close to our specimen. They differ in ornamentation during late ontogeny (Henderson and Mcnamara, 1985; Kennedy, 1986; Stinnesbeck, 1986; Ward and Kennedy, 1993). The higher density of ventrolateral ribs, the shape of primaries and a similar whorl section relate the Cárdenas species closer to P. (P.) neubergicus than to P. (P.) jacquoti, although the density of the primary ribs is less than that of P. (P.) neubergicus. The disappearance of secondary ribbing is most probably an artifact due to mechanical abrasion, because faint traces of ribs remain visible on the shell of our specimen. Material. One deformed, weathered specimen from the base of the middle member of the Cárdenas Formation at the railway section east of Cárdenas. Occurrence. All species discussed below are Maastrichtian in age. Pachydiscus (P.) neubergicus, which appears to be conspecific with our specimen, is the index fossil for the Early Maastrichtian (Christensen et al., 2000; Odin and Lamaurelle, 2001). In North America, the species was recorded only once from the Navesinsk Formation of New Jersey (Kennedy et al., 2000).
FATMI & Kennedy (1999):
Discussion.-Two subspecies have been recognized in Pachydiscus neubergicus. In the nominate subspecies, which ranges from Lower to lower Upper Maastrichtian, specimens at the ontogenetic stage corresponding to the present specimen have 1417 umbilical bullae, and 48 to almost 60 ribs at the ventrolateral shoulder. Subspecies dissitus Henderson and McNamara, 1985 (p. 72, pl. 7, figs. 7, 9; pl. 10, figs. 3-6; text-figs. 11, 12c, 13c) of the upper Upper Maastrichtian cannot be separated from the nominate subspecies at this diameter, but adults of the two differ in that neubergicus neubergicus has numerous primary ribs separated by single secondary or intercalated ribs or not, whereas neubergicus dissitus has many more ventral than umbilical ribs. Having only a juvenile, we cannot identify the present specimen to subspecific level. See Kennedy and Summesberger (1986), Henderson and McNamara (1985), and Ward and Kennedy (1993), for a comprehensive synonymy and discussion of the species and subspecies.
Ward & Kennedy (1993):
Discussion. - Juvenile Pachydiscus (P.) neubergicus that are too small to be referred either to the nominate subspecies or to dissitus of Henderson and McNamara (1985) occur well above the upper range limit of P. (P.) neubergicus neubergicus at Hendaye and Bidart. They probably represent the upper Maastrichtian subspecies dissitus, but in the absence of adult whorls, we cannot be certain. Occurrence.- In the Biscay sections this taxon is found in Member IV (upper Maastrichtian).
Synonym list:
Ifrim et al. (2005):
1846 Ammonites chrishna Forbes. - Forbes : p.103 pl. 9, fig. 2
1858 Ammonites Neubergicus Hauer. - Hauer : p.12 pl. 2, figs. 1-3 [non pl. 3, figs. 1-3 = Pachydiscus epiplectus (Redtenbacher, 1873)]
1986 Pachydiscus (Pachydiscus) neubergicus Hauer. - Kennedy & Summesberger : p.189 pl. 2, figs. 1-2; pl. 3, figs. 1-3; pl. 4, figs. 1-5; pl. 5, figs. 1,4-5; pl. 6, figs. 1-2,5; pl. 15, figs. 7-8; fig. 5a,b (with full synonymy)
1986 Pachydiscus (Pachydiscus) neubergicus Hauer. - Kennedy : pl. 4, fig. 3
2000 Pachydiscus (Pachydiscus) neubergicus Hauer. - Kennedy et al. : p.9 fig. 4u-w
2005 Pachydiscus (Pachydiscus) neubergicus Hauer. - Ifrim et al. : 54, 55 figs. 4a-c, fig. 5h
FATMI & Kennedy (1999):
1858 Ammonites Neubergicus Hauer. - Hauer : 12 (pars) pl. 2, figs. 1-3, non pl. 3, figs. 1,2
1986 Pachydiscus (Pachydiscus) neubergicus Hauer. - Kennedy & Summesberger : p.199 pl. 2, figs. 1, 2; pl. 3, figs. 1-3; pl. 4, figs. 1-5; pl. 5, figs 1, 4, 5; pl. 6, figs. 1, 2, 5; pl. 15, figs. 7, 8, text-fig. 5a, b (with full synonymy)
1992 Pachydiscus (Pachydiscus) neubergicus neubergicus Hauer. - Kennedy & Henderson : p.421 pl. 10, figs. 6-8; pl. 11, text-fig. 6a (with additional synonymy)
1993 Pachydiscus (Pachydiscus) neubergicus neubergicus Hauer. - Ward & Kennedy : p.30 figs. 25.9, 25.10, 25.11, 25.12, 25.14, 25.16-25.18, 27.3-27.5, 27.7, 28.1-28.3, 30.4, 30.6
1993 Pachydiscus (Pachydiscus) neubergicus neubergicus Hauer. - Kennedy & Hancock : p.158 pl. 3, figs. 6, 7; pl. 9, figs. 5-8; pl. 12, figs. 7-9; pl. 13, figs. 5-7
1997 Pachydiscus neubergicus Hauer. - Ward & Orr : fig. 4.1
1999 Pachydiscus (Pachydiscus) neubergicus Hauer. - FATMI & Kennedy : figs. 8.1-8.3
Ward & Kennedy (1993):
1993 Pachydiscus (Pachydiscus) neubergicus Hauer. - Ward & Kennedy : p. 16, 25 fig. 16.4-16.6; 23.13, 23.14 (subspecies undetermined)
Was used in synonym list of:
Pachydiscus (Pachydiscus) neubergicus neubergicus Hauer 1858
Stratigraphy - relative ages:
Maastrichtian: Ifrim et al. (2005)
upper Maastrichtian - upper Maastrichtian: Ward & Kennedy (1993)
upper Maastrichtian - lower Maastrichtian: FATMI & Kennedy (1999)

Forbes,E.. (1846):
Report on the Cretaceous fossil invertebrates from southern India, collected by Mr. Kaye and Mr. Cunliffe . Transactions of the Geological Society of London Vol. 2(7) p. 97–174

Hauer,F.. (1858):
Über die Cephalopoden der Gosauschichten . Beiträge zur Paläontologie von Österreich Vol. 1 p. 7-14

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

Kennedy,W.J.. and Summesberger,H.. (1986):
Lower Maastrichtian ammonites from Neuberg, Steirmark, Austria: . Beiträge zur Paläontologie von Österreich Vol. 12 p. 181–242

Kennedy,W.J.. and Henderson,R.A.. (1992):
Non-heteromorph ammonites from the Upper Maastrichtian of Pondicherry, south India . Palaeontology Vol. 35 p. 381-442

Kennedy,W.J.. and Hancock,J.M.. (1993):
Upper Maastrichtian ammonites from the Marnes de Nay between Gan and Rebenacq (Pyrenees-Atlantiques), France . Geobios Vol. 26 p. 575-594

Ward,P.D.. and Kennedy,W.J.. (1993):
Maastrichtian Ammonites from the Biscay Region (France, Spain) . Memoir (The Paleontological Society), Journal of Paleontology34 (Supplement to Vol. 67)(5) p. 1-58

Ward,P.D.. and Kennedy,W.J.. (1993):
Maastrichtian ammonites from the Biscay Region . Journal of Paleontology Vol. 67(5 II) p. 1-58

Ward,P.D.. and Orr,W.. (1997):
Campanian-Maastrichtian ammonite and planktonic foraminiferal biostratigraphy from Tercis, France: implications for defining the stage boundary. . Journal of Paleontology Vol. 71 p. 407-418

FATMI,A.N.. and Kennedy,W.J.. (1999):
Maastrichtian ammonites from Balochistan, Pakistan. . Journal of Paleontology Vol. 73(4) p. 641-662

Kennedy,W.J..; Landman,N.H..; Cobban,W.A.. and Johnson,R.O.. (2000):
Additions to the ammonite fauna of the Upper Cretaceous Navesinsk Formation of New Jersey . American Museum Novitates Vol. 3306 p. 1–30

Ifrim,C..; Stinnesbeck,W.. and Schafhauser,A.. (2005):
Maastrichtian shallow-water ammonites of northeastern Mexico . Revista Mexicana de Ciencias Geológicas Vol. 22(1) p. 48-64

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