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Species Desmophyllites larteti Seunes 1891


Diagnosis / Definition:
Ward & Kennedy (1993):
Description. - Type specimens are composite molds showing little, if any, indications of post-mortem crushing. Lectotype has 160° of body chamber preserved; paralectotype 50°. Early whorls oftypes restored in plaster of Paris, as is clearly shown in Seunes' figures. Coiling very involute, with tiny umbilicus comprising around 6 percent of diameter, shallow, with flattened umbilical wall and narrowly rounded umbilical shoulder. Whorl section compressed oval, with whorl breadth to height ratio 0.45-0.58, greatest breadth below mid-flank, inner flanks broadly rounded, outer flanks convergent and venter narrowly arched. Phragmocones appear smooth, but for traces of constrictions visible at smallest diameter in paralectotype. Constrictions much more conspicuous towards end of phragmocone and on body chamber, where number 5-6 per half whorl. They are narrow, deep, distant, prorsiradiate and biconcave, being concave on inner flank, convex at mid-flank and concave on outer flank, sweeping strongly forwards over ventrolateral shoulder to cross venter in narrow linguoid convexity. Constrictions preceded by rounded collar-rib, weak on inner flanks, but strengthening on outer flank and best developed over venter. Interspaces between constrictions bear delicate growth lines and striae that are most conspicuous on venter. Suture with narrow-stemmed, symmetrically bifid saddles; L deeply incised; numerous auxiliary saddles on umbilical lobe.
Discussion / Comments:
Ward & Kennedy (1993):
Types. - Lectotype, designated by Kennedy and Summesberger (1984, p. 156) is the original of Seunes, 189 1, Pl. 13(4), fig. 2; paralectotype is the original of Seunes, 189 1, Pl. 12(3), fig. 2; Pl. 13(4), fig. 3, illustrated here as Figures 23.5-23.7, 23.10- 23.12, 24, 25.15, and from the "Assize a Pachydiscus Fresvillensis. P. Jacquoti et Stegester," Gan, Route de Gan a Rébénacq, Pyrénées-Atlantiques, France. Both are unregistered specimens in the Sorbonne Collections, now in the Université Paris VI, Paris. Dimensions. - Dimensions are given in Table 2. Discussion. - Material from the coastal sections matches the types well, both in terms of size and the development of constrictions (Figure 23. l), extending to at least 120 mm diameter. Juveniles to an estimated 45 mm diameter are smooth, or show only the slightest trace of constrictions (Figure 23.2,23.3,23.9). Desmophyllites diphylloides (Forbes, 1 846) (p. 105, Pl. 8, fig. 8; see Henderson and McNamara, 1985, p. 54, Pl.4, figs. 1-4) is a smaller, stouter species with flattened subparallel flanks (whorl breadth to height ratios of 0.85-0.76 are cited by Henderson and McNamara), broadly rounded venter and shallow constrictions that are weaker than those of D. larteti and only feebly flexed in most described examples (e.g., Collignon, 196 1, Pl. 25, figs. 1-8). Henderson and McNamara (1985, p. 54, Pl. 4, figs. 14) regarded Desmophyllites phyllimorphum (Kossmat, 1898) (p. 1 10(175), Pl. 19(25), fig. 10) as a synonym of D. diphylloides, noting that the whorl section of large diphylloides is much more compressed than that of juveniles; the constrictions are far less flexuous than in D. larteti. A large Alaskan example (Jones, 1963, Pl. 10, figs. 4-6) referred to phyllimorphum by Jones, and to diphylloides by Henderson and McNamara, is much stouter than the types of larteti but has constrictions that are almost as flexuous. Immel, Klinger, and Wiedmann (1982, p. 16) regarded phyllimorphum as a synonym of larteti, but more and better adult specimens of Desmophyllites are needed to determine whether the three nominal species are in reality but one. The Desmophyllites cf. D. larteti (Seunes, 189 1) of Immel, Klinger, and Wiedmann (1982, p. 15, Pl. 4, fig. 4; text-fig. 4) has irregular ribs and constrictions, a broad umbilicus, and a broad stem to L/U2, quite unlike the present species. It is from the lower Santonian, and best excluded from the present form. Occurrence.- In the Biscay sections this taxon ranges from Member II (lower Maastrichtian) to the top of Member IV (upper Maastrichtian). Records from Madagascar (see synonymy) may rather represent Desmophyllites diphylloides (fide Henderson and McNamara, 1985, p. 54).
Systematics:

38
 Ordo Ammonoidea
  Subordo Ammonitina
   Superfamilia Desmocerataceae
    Familia Desmoceratidae
     Subfamilia Desmoceratinae
      Genus Desmophyllites
       Species Desmophyllites larteti
Synonym list:
Ward & Kennedy (1993):
1891 Desmoceras larteti Seunes. - Seunes : p.19 pl. 12(3), fig. 2; pl. 13(4), fig. 2, 3
1894 Schlüteria sp. larteti Seunes. - Grossouvre : p.218 pl. 34; fig. 2, 3
1895 Schlüteria larteti Seunes. - Kossmat : 105(9)
1907 Desmoceras larteti Seunes. - PERVINQUIERE : p.143
1925 Schlüteria larteti Seunes. - Diener : p.132
1929 Desmophyllites larteti Seunes. - Spath : p.270
non 1938 Schlüteria larteti Seunes. - COLLIGNON : p.92 pl. 7, fig. 3; text-fig. K, L (= D. diphylloides)
1955 Desmophyllites larteti Seunes. - Matsumoto & Obata : p.125 text-fig. 2
1957 Desmophyllites larteti Seunes. - Wright : L370 fig. 484, 1
? non 1961 Desmophyllites larteti Seunes. - COLLIGNON : p.66 pl. 26, fig. 2; text-fig. 6
non 1971 Desmophyllites larteti Seunes. - COLLIGNON : p.37 pl. 655; fig. 2416 (?=D. diphylloides)
1984 Desmophyllites larteti Seunes. - Kennedy & Summesberger : p.156 pl. 1, fig. 6; pl. 2, fig. 1-3, 5-6
1993 Desmophyllites larteti Seunes. - Ward & Kennedy : p. 25, 26, 27 fig. 23.1, 23.2, 23.3, 23.5-23.7, 23.9-23.12, 24, 25.15
Stratigraphy - relative ages:
upper Maastrichtian - lower Maastrichtian: Ward & Kennedy (1993)
References:

Seunes,J.. (1891):
Contributions à l’étude des Céphalopodes du Crétacé Supérieur de France. Ammonites du Calcaire à Baculites du Cotenin (Suite); II. Ammonites du Campanien de la région sous-Pyrénéenne, Département de Landes . Mémoirs de la Société Géologique de France, Paléontologie Vol. 2(2) p. 8-22

Grossouvre,d.A.. (1894):
Recherches sur la Craie Supérieure, 2, Paléontologie. Les ammonites de la Craie Supérieure, Mémoirs pour Servir à l’Explication de la Carte géologique détaillée de la France (mis-dated 1893).. p. 264

Kossmat,F.. (1895):
Untersuchungen,über die Südindische Kreideformation. Beitrage zur Palaontologie Osterreich-Ungarns und des Orients . Vol. 9 p. 97-203 (1-107)

PERVINQUIERE,L.. (1907):
Etudes de paleontologie tunisienne I: Cephalopodes des terrains secondaires.
In: Carte Geologique de Tunisie p. 438 pp

Diener,C.. (1925):
Ammonoidea neocretacea . Fossilium Cat, (1: Animalia) Vol. 29 p. 244 pp.

Spath,L.F.. (1929):
Corrections of cephalopod nomenclature . Naturalist Vol. 871 p. 269-271

COLLIGNON,M.. (1938):
Ammonites Campaniennes et Maastrichtiennes de I'ouest et du sud de Madagascar. . Annales Geologiques du Service des Mines de Madagascar Vol. 9 p. 55-118

Matsumoto,T.. and Obata,I. (1955):
Some Upper Cretaceous desmoceratids from Hokkaido and Saghalien . Memoirs of the Faculty of Science, Kyushu University, Series D, Geology Vol. 5 p. 119-151

Wright,C.W.. (1957):
Cretaceous Ammonoidea.
In: Treatise on Invertebrate Paleontology, Pt. L, Mollusca 4, Cephalopoda Ammonoidea Eds: Moore, R.C.. p. L1-L490

COLLIGNON,M.. (1961):
Ammonites néocrétacées du Menabe (Madagascar). VII. Les Desmoceratidae. . Annales Géologiques du Service des Mines de Madagascar Vol. 31 p. 1-115

COLLIGNON,M.. (1971):
Atlas des fossiles caracteristiques de Madagascar (Ammonites)(Maestrichtian). Vol. 17 p. 82

Kennedy,W.J.. and Summesberger,. (1984):
Upper Campanian ammonites from the Gischliefgraben (Ultrahelvetic, Upper Austria) . Beiträge zur Paläontologie von Östereich Vol. 11 p. 149-206

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
Anonymous: Unedited TaxonConcept data
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