Taxon Concept provided by
| Taxon Concept provided by
|
|
| Home | Search | |
| TaxonConcept data set details: |
||||||
| Back to Search | ||||||
| Anonymous: Unedited TaxonConcept data | ||||||
| Notice: This catalogue page may contain unedited data.
| ||||||
Species Pachydiscus (Pachydiscus) riccardi Macellari 1986 | ||||||
|
|
||||||
| Alternative name: | ||||||
| Diagnosis / Definition: | ||||||
|
MACELLARI (1986): DIAGNOSIS.- Shell involute with whorl section inflated to moderately compressed. Umbilical wall vertical. Ornamentation composed of slightly prorsiradiate radial ribs that are continuous across the flank in juvenile specimens. Umbilicus bordered by slightly elongated, blunt, rectiradiate nodes. Venter crossed by weak but clearly defined and evenly spaced radial ribs. DESCRIPTION.- Shell large (diameters of more than 30 cm common), involute. Whorl section moderately inflated to moderately compressed (mean W/H = 0.74) (Table 15); umbilical wall vertical, flanks slightly convex near the umbilicus, then become straight. Maximum width observed near the umbilicus. Venter broad and rounded. Ornamentation in the juvenile portion of the shell with well developed prorsiradiate ribs, continuous throughout the flank and slightly thickened near the umbilicus. Adult shell with the middle flank almost smooth, and short, rectiradiate umbilical tubercles (approximately 18 per whorl). Ventral portion of the flank and venter with closely spaced, weak, and slightly prorsiradiate ribs, less developed and more spaced in the adult. Suture line typical pachydiscid with the lobes narrow and symmetric (Figure 39). |
||||||
| Discussion / Comments: | ||||||
|
MACELLARI (1986): HOLOTYPE.- Pachydiscus (Parapachydiscus) aff. gollevillensis (d'Orbigny), Kilian and Reboul, 1909, Pl. 19, fig. 3, Pl. 20, fig. 1 (Mo 1905a). MATERIAL.- Ten specimens very well preserved. ORIGIN OF NAME.- Species dedicated to Dr. Alberto C. Riccardi, from the Museo de La Plata, Argentina. REMARKS.- This species is similar to P. (Pachydiscus) ultimus, and it is clearly related in the degree of involution and general shape ofthe ornamentation. However, it can be easily distinguished by its more inflated section (W/H = 0.74 in P. (P.) riccardi, vs. 0.56 in P. (P.) ultimus), by its more developed and incised ribs, and particularly by the shape and number of the umbilical tubercles, which are blunt, short, rectiradiate, and less numerous (approx. 18 per whorl) in P. (P.) riccardi, and elongated, strongly prorsiradiate, and more abundant (up to 31 per whorl) in P. (P.) ultimus. This species has been compared with P. (Pachydiscus) gollevillensis (d'Orbigny) (Kilian and Reboul, 1909), but clearly differs by its more inflated section and by the presence of more numerous and less defined radial ribs in the umbilical region. P. (P.) quiriquinae Steinmann (in Steinmann, 1895, P1. 6, figs. 3a, b) has a similar but slightly stronger ornamentation in the flank and a similar degree of involution; however, the ribs are more incised in the venter and the whorl section is much more inflated. LOCALITIES.- Seymour Island, 6 1 +, 15 1, 153, 188, 189, 190, 325, 326, 327, 329, 337, 356, 357, 360, 378, 397, D-83, 0-83, St. 6. STRATIGRAPHIC OCCURRENCE.- Lopez de Bertodano Formation, P. riccardi Zone ("middle" to late Maastrichtian). |
||||||
| Systematics: | ||||||
|
50 Ordo Ammonoidea Subordo Ammonitina Superfamilia Desmocerataceae Familia Pachydiscidae Genus Pachydiscus Species Pachydiscus (Pachydiscus) riccardi |
||||||
| Synonym list: | ||||||
| MACELLARI (1986): 1909 Pachydiscus (Pachydiscus) aff. gollevillensis d'Orbigny. - Kilian & Reboul : p.43 pl. 19, fig. 3;
pl. 20, fig. 1
1986 Pachydiscus (Pachydiscus) n sp. riccardi Macellari. - MACELLARI : p. 45, 47, 48 fig. 37.3-37.4, 38.1-38.3, 39
|
||||||
| Stratigraphy - relative ages: | ||||||
| lower Maastrichtian - middle Maastrichtian: MACELLARI (1986) |
||||||
| References: | ||||||
Kilian,W.. and Reboul,P.. (1909): MACELLARI,C.E.. (1986): |
||||||
| Anonymous: Unedited TaxonConcept data | ||||||
 This work is licensed under a Creative Commons Attribution 2.5 License. | ||||||
| Back to Search | ||||||
|
Taxon relations
Ranking (experimental) |
||||||