taxonID	type	description	language	source
0397878A0C3CFFCFFF5AFC965BF42C05.taxon	description	(Figs 3; 4; 5; 6 A, B; 7 A, B; Table 1)	en	Jattiot, Romain, Boursicot, Pierre-Yves (2026): An enigmatic ammonite population from the late Callovian of Montreuil-Bellay (Maine-et-Loire, France). Geodiversitas 48 (13): 273-285, DOI: 10.5252/geodiversitas2026v48a13
0397878A0C3CFFCFFF5AFC965BF42C05.taxon	materials_examined	EXAMINED MATERIAL. — France • 10 specimens; Pays de la Loire, Maine-et-Loire, Montreuil-Bellay; late Callovian (Pseudopeltoceras leckenbyi Horizon); MNHN [MNHN. F. A 99979, A 99980, A 99981, A 99982, A 99983, A 99984, A 99985, A 99986, A 99987, A 99988].	en	Jattiot, Romain, Boursicot, Pierre-Yves (2026): An enigmatic ammonite population from the late Callovian of Montreuil-Bellay (Maine-et-Loire, France). Geodiversitas 48 (13): 273-285, DOI: 10.5252/geodiversitas2026v48a13
0397878A0C3CFFCFFF5AFC965BF42C05.taxon	description	DESCRIPTION Most specimens are fully septate. OnlyMNHN. F. A 99985 and A 99987 (Fig. 3 S-U, Y-AA) appear to preserve the beginning of the body chamber, since a very small portion of shell without suture lines can be observed at the adapertural end of their outer whorl. Yet, neither specimen shows any obvious signs of maturity (e. g., sutures approximation or distinctive change in ornamentation on the small portion of body chamber). All of the material (Fig. 3) is therefore interpreted as phragmocones of an immature assemblage, of which the adult morphology remains unknown for the time being. The shell is very involute, with a U / D ratio of 0.12 on average (Table 1). The whorl section is moderately to weakly compressed (W / H ratio ranging from 0.58 to 0.87), elliptical. Noteworthy, the ventral shell outline is irregular in some specimens (i. e., a few ventral, discreet bulges are visible along the external whorl; Fig. 4 A-C). The whorls are high; the ventral part is wide and rounded. Flanks are nearly parallel on their inner part and gently converging on their external part (e. g., Fig. 3 C, I, U). Hence, maximum thickness is, overall, at mid-flank. The umbilicus is deep, with a high, nearly perpendicular wall. The umbilical shoulders are narrowly rounded and notably elevated, hence forming a distinct umbilical ridge. The umbilical region is slightly depressed. At earlier ontogenetic stages, the shell is more evolute and exhibits more depressed whorls with convex flanks (Fig. 5 A-G). The ornamentation is characterized by biconcave ribs, with the point of convexity located slightly below mid-flank in all specimens. In the umbilical region, the ribs are extremely fine and dense. As a general rule, they then merge in pairs (or more) at the point of convexity to form a significantly thicker rib. Around the ventrolateral shoulders, some ribs irregularly bifurcate (see, e. g., Fig. 3 Y). On the venter, the ornamental pattern often appears chaotic: a simple rib that bifurcates on one flank often correspond to two separate ribs on the opposite flank and the ribs pass through the venter in several disordered manners (Fig. 4 D-F). The venter ribbing in specimen MNHN. F. A 99984 is notably interrupted in the middle of the venter by a distinctive line (Fig. 3 Q). Noteworthy, most specimens exhibit an extremely discreet spiral strigation, slightly more noticeable in specimens MNHN. F. A 99984 and A 99985 (Fig. 4 G, H). In specimen MNHN. F. A 99984, the spiral strigation is accompanied with an inconspicuous spiral ridge located at the point of convexity of the ribs (Figs 3 S; 4 H). Suture lines of specimen MNHN. F. A 99984 (Fig. 6 A) are moderately complex, with trifid lobes and rather wide saddles. Suture lines of specimen MNHN. F. A 99988 (Fig. 6 B) slightly differ, with a wider lateral lobe and slightly more frilled, incised elements. Importantly, no signs of exogenous physical injury (e. g., brutal change in shell morphology and ornamentation, or repaired shell areas) can be identified.	en	Jattiot, Romain, Boursicot, Pierre-Yves (2026): An enigmatic ammonite population from the late Callovian of Montreuil-Bellay (Maine-et-Loire, France). Geodiversitas 48 (13): 273-285, DOI: 10.5252/geodiversitas2026v48a13
