Cenomanian ammonites from Santander ( Cantabria ) and Sopeira ( Aragón , south-central Pyrenees ) , northern Spain

Upper Cenomanian (Cretaceous) ammonites are described for the first time from the environs of Santander (Cantabria) and Sopeira (Aragón, Huesca province) in northern Spain. The following species are present: Tetragonites subtimotheanus Wiedmann, 1962, Calycoceras (Newboldiceras) asiaticum asiaticum (Jimbo, 1894), Calycoceras (Newboldiceras) planecostatum (Kossmat, 1897), Eucalycoceras pentagonum (Jukes-Browne,1896), Eucalycoceras jeanneti Collignon, 1937, and Thomelites sornayi (Thomel, 1966). This assemblage is typical of the lower Upper Cenomanian Calycoceras (Proeucalycoceras) guerangeri Zone, with the exception of E. jeanneti, previously known only from Madagascar.


INTRODUCTION
The ammonite faunas described below have two origins (Fig. 1).The first is the material collected by Louis Mengaud in the Santander area of Cantabria during the course of his thesis research (Mengaud, 1920), housed in the collections of the University of Toulouse (UPS).The second is new collections made by one of us (MB) in the Sopeira area of Huesca province in the south-central Pyrenees.Ammonite faunas of this age are sparse; Mengaud's material is revised, while the new material is described for the first time.Both collections are cha rac terised by an association of Eucalycoceras pentagonum (Jukes-Browne, 1896) and Thomelites sornayi (Thomel, 1966), typical of the lower Upper Cenomanian Calycoceras guerangeri Zone of the standard North-West European sequence.Of note is the presence of Eucalycoceras jeanneti Collignon, 1937, previously known only from Madagascar.

LOWER AND UPPER CENOMANIAN AMMONITES FROM SOPEIRA
The first records of Cenomanian ammonites from the southern flank of the Pyrenees are all from the Sopeira region.Dalloni (1910Dalloni ( , 1930) ) mentioned the discovery of Cenomanian ammonites (Turrilites costatus, Mantelliceras mantelli) in the sequence of marls subsequently termed "Marnes de Sopeira" by Souquet (1967) and formally Sopeira marl Formation (Mey et al., 1968).Bilotte & Souquet (1972) recognised Upper Cenomanian faunas in the conglomerates that overlie the Sopeira marl Formation.Martínez (1982a, b) recognised abundant Lower and Middle Cenomanian ammonite faunas from the Sopeira marl Formation.In the latest study, Caus et al. (1993) correlated the abundant benthic and planktonic microfaunas in this transitional platform to basinal sequence.
Assemblages 1 and 2 were assigned to the Lower Cenomanian by Martínez (1982a, b), and assemblage 3 to the Middle Cenomanian.
The presence of Eucalycoceras pentagonum and Thomelites sornayi date both the Santander and Sopeira assemblages very precisely, to the lower Upper Cenomanian Calycoceras (Proeucalycoceras ) guerangeri Zone, which can be recognised across western Europe from southern England and Germany to Haute Normandie, Sarthe, and Provence in France, while we have previously recognised elements of the zonal fauna from Pech de Foix in Ariège (Kennedy et al., 1996).A particularly interesting occurrence in the present fauna is Eucalycoceras jeanneti Collignon, 1937, previously known only from the holotype, from Ankilimanarivo, Madagascar (Fig. 2), a locality that is the source of the type material of Hourcquiceras Collignon, 1937, a poorly understood genus of Euomphaloceratinae that also occurs in south India, and only now precisely dated.
Description and discussion.UPS J10 is a well-preserved composite mould 56.4 mm in diameter.Coiling is involute, the umbilicus deep, with a flattened, outwardinclined umbilical wall and narrowly rounded umbilical shoulder.The whorl section varies from compressed to depressed as a result of post-mortem distortion: the original whorl proportions cannot be established.The flanks are flattened, the ventrolateral shoulders broadly rounded, the very broad venter very feebly convex.There are at least six constrictions on the adapertural half whorl; the last four progressively closer together.They are  prorsiradiate, straight on the inner flank, flexed feebly forwards and feebly concave on the outer flank, flexed back and convex across the ventrolateral shoulder and feebly concave across the venter.The specimen closely resembles individuals of comparable size and preservation described by Thomel (1987) from southeast France as Tetragonites subtimotheanus maclearni Wiedmann, 1973.Occurrence.Upper Albian to lower Upper Cenomanian, southern England, southeast France, Sopeira (Huesca province, Spain), Crimea, Ukraine, KwaZulu-Natal (South Africa), Madagascar, south India, Alaska and British Columbia.
Material.UPS LM 101, from the glauconitic marls of the "Pas du Chat" section, Santander.
Discussion.This well-known species is represented by a large worn individual 150 mm in diameter; it differs in no significant respect from specimens of similar size from southern France figured by Thomel (1992, pl. 13, figs. 1-3) and Kennedy (1994, pl. 5, figs. 8, 9).
Occurrence.Upper Albian to Upper Cenomanian; widespread throughout Europe, Africa, south India, and Japan.
Discussion.Calycoceras are the commonest element of the "Pas du Chat" fauna, with 18 individuals, of which most are comparable to the subgenus Newboldiceras Thomel, 1972.Unfortunately, all but five are specifically indeterminate.
Calycoceras (Newboldiceras) Thomel, 1972 Type species.By original designation by Thomel (1972:  105), Acanthoceras newboldi Kossmat, 1897: 5 (112), which is a junior synonym of Acanthoceras rhotomagense var.asiatica Jimbo, 1894: 177, pl. 20, fig. 1 (Wright & Kennedy, 1990: 239)  Material.UPS J6, UPS J0, from Sopeira and UPS LM 106, from Santander.Description and discussion.UPS J6 (Fig. 6.J) is a wellpreserved juvenile 49 mm in diameter.The umbilicus comprises 30% of the diameter, with a convex wall and broadly rounded umbilical shoulder.The whorl section is depressed, with a costal whorl breadth to height ratio of 1.15, rounded-trapezoidal in intercostal section and polygonal in costal section.Nine bullae perch on the umbilical shoulder of the outer half whorl, and give rise to single straight ribs with, in some cases, a second rib feebly linked to the bulla.There are one or two long or short intercalated ribs.All ribs bear a small rounded-clavate inner ventrolateral tubercle, outer ventrolateral and siphonal clavi, linked across the venter by a strong straight transverse rib.
Specimen UPS J0 (Fig. 4.D-F) is a well-preserved, and 81 mm in diameter.The umbilicus comprises 31% of the diameter.The whorl section is depressed.Nine to ten small umbilical bullae give rise to one or two primary ribs, with short intercalate ribs between the primaries to give a total of 17 ribs per half whorl at the umbilical shoulder.All ribs bear rounded inner ventrolateral tubercles and outer ventrolateral and siphonal clavi, linked across the broad, feebly convex venter by a strong transverse rib.This specimen is close to the holotype of Calycoceras newboldi newboldi (a synonym of asiaticum), as figured by Kossmat (1897, pl. 1 (12), fig.2; reproduced by Wright & Kennedy, 1990, text-fig. 98).Calycoceras (Newboldiceras) asiaticum asiaticum and C. (N.) asiaticum spinosum (Kossmat, 1897)  Type.The lectotype, by the subsequent designation of Wright & Kennedy (1990: 252), is number 14842 in the Collections of the Geological Survey of India, the ori ginal in Kossmat (1897, pl. 2 [13], fig. 1) (Wright & Kennedy, 1990, text-fig.101c-e), from the Utatur Group of Odium, south India.
Material.UPS LM 103, UPS LM 109, from Santander and UPS J7, from Sopeira.Description and discussion.UPS J7 (Fig. 4.C) is a wellpreserved individual with a maximum preserved diameter of 71.5 mm.The umbilicus comprises 20% approximately of the diameter.The original proportions cannot be established as the specimen is partially embedded in matrix, but the umbilical wall is flattened, the umbilical shoulder quite narrowly rounded, the flanks very feebly convex, convergent, the ventrolateral shoulder broadly rounded and the venter flattened.There are four welldeveloped umbilical bullae on the outer half whorl of the specimen, with up to three non-bullate primaries and occasional shorter intercalated ribs between to give 22 ribs per half whorl at the ventrolateral shoulder.All ribs bear outer ventrolateral clavi only, linked across the feebly convex venter by a broad flat-topped rib, the ribs separated by narrower interspaces.The second specimen, UPS LM 109 (Fig. 4.A, B) is typical of the numerous poorly preserved Calycoceras in the fauna, although retaining diagnostic features: crowded variably bullate primary ribs with occasional shorter intercalated ribs, and outer ventrolateral clavi only.

B
C A
Material.Specimen UPS LM 108, from Santander.Description and discussion.The specimen is 37.5 mm in diameter.Strong, coarse straight prorsiradiate ribs primary ribs bear strong umbilical and inner ventrolateral tubercles, and weaker outer ventrolateral clavi.They are separated by intercalated ribs with outer ventrolateral and siphonal clavi only.This pattern of ribs and tubercles is characteristic of C. (N.) hippocastanum, and corresponds to that of better-preserved juveniles figured by Wright & Kennedy (1990, pl. 71, figs. 1, 2).
Description and discussion.The inner whorls are not seen in the present material.On the outer whorl, the whorl section is compressed, the coiling moderately evolute.The ornament of the phragmocone, well-shown by UPS J2 (Fig. 6.A, B) consists of strong umbilical bullae that give rise to pairs of low, coarse, straight ribs, with up to three non-bullate long or short intercalated ribs between.All ribs bear strong outer ventrolateral clavi, linked over the venter by a coarse transverse rib with a weaker siphonal clavus.This ornament extends onto the adapical part of the adult body chamber.Thereafter, the bullae are lost, and the ribs are predominantly long primaries.On the adapertural part of the body chamber the ventral and siphonal clavi are lost, the venter broadens and rounds, and is crossed by coarse transverse ribs.Specimen UPS LM12303 (Fig. 6.F-H) is a complete adult that shows the change in ornament from phragmocone to body chamber well.The fragmentary UPS J1 (Fig. 5.A, B) is very wellpreserved and demonstrates the loss on tuberculation on the adapertural part of the body chamber.An adult, UPS LM 110 (Fig. 5.E) bears a close apparent similarity to the specimen of Eucalycoceras jeanneti Collignon, 1937 from the "Pas du Chat" (Fig. 5.C, D), but has predominantly long ribs with persistent ventrolateral clavi, and the typical coarse umbilical bullae of T. sornayi on the poorly preserved adapical part of the outer whorl.
Thomelites sornayi is comprehensively reviewed by Wright & Kennedy (1990), who discuss differences from other Thomelites species.
Description.The holotype (Fig. 2) is a complete adult with a half whorl of body chamber preserved.The inner whorls are damaged, but show bullate, straight, feebly prorsiradiate ribs, with occasional long intercalated ribs.Inner and outer ventrolateral tubercles persist on the phragmocone to an estimated diameter of 70 mm, beyond which the venter is damaged until the beginning of the body chamber at an estimated diameter of 80 mm, where the first few ribs have outer ventrolateral tubercles only, thereafter lost.The body chamber is compressed, with flattened subparallel flanks; the whorl breadth to height ratio is 0.82 at the adapical end, and 0.69 at the adapertural end.The ventrolateral shoulders and venter are broadly rounded.There are 12 umbilical bullae on the adapertural half whorl of the body chamber, weakening on the last few ribs before the aperture.The bullae are small, sharp, and linked to the umbilical seam by a welldeveloped rib.At the adapical end of the body chamber they occasionally give rise to a pair of ribs, thereafter single ribs only.The ribs are narrow, straight and prorsiradiate across the flanks, with one to three long or short intercalated ribs between.All ribs flex forwards, and are feebly concave over the ventrolateral shoulder, strengthening, the ventrolateral clavi lost, the ribs strong, and passing straight across the venter.
Discussion.Although poorly preserved, the present specimen shows the distinctive coiling, rib style, and, so far as can be established, the tuberculation of the holotype and previously only known specimen of Eucalycoceras jeanneti.
original designation.
differ in the much more robust tuberculation of the latter, although there are transitional forms.