Jurienella, Pictet & Bulot, 2025

Genus Jurienella nov. gen.

ZooBank LSID: urn:lsid:zoobank.org:pub: https://zoobank. org/ 96DBBC1B-3A26-470D-9923-8033214DDC85.

Type-species. Breistrofferella peyroulensis Atrops, Autran, Reboulet, 1996 . Te holotype of the species, as well as the paratypes, are preserved in the Autran , Davoux , and Mascarelli collections, which casts are stored at the Université Claude Bernard Lyon 1, Laboratoire de Géologie de Lyon—Terre , Planètes et Environnement (LGL-TPE).

Locus typicus of the type-specimens. Clausson section, Peyroules, Alpes-de-Haute-Provence, France.

Derivatio nominis. Genus dedicated to André Jurien, who collected rare specimens of this new genus in the Pateroux section ( Vaud, Suisse).

Stratum typicum. Bed 20aII, Formation 13, C. loryi Zone , lower Hauterivian.

Diagnosis. Small ammonites (approximately 40–50 mm in diameter), with fairly evolute colling. Te ornamentation is relatively coarse, composed of an alternation of main ribs which arise from umbilical bullae, and shorter, external, intercalated ribs, which can arise from a mediolateral bifurcation from the main ribs. Te bifurcation is marked by a slight tuberculiform elevation. All ribs exhibit a distinct backward inflection in the upper part of the flanks. Wide and nearly tabular venter in inner whorls, bordered by marginal tubercle and not by clavi contrary to the indication of Atrops et al. (1996). Ventral ribbing interrupted by a large smooth ventral band. On the end of the body chamber, the venter becomes well rounded and the ribs cross the siphonal circumference by drawing a marked sinus, strongly projected forwards.

Content. Te genus seems monospecific at the moment.

Relationships and differences. Te species " B." peyroulensis was assigned to the genus Breistrofferella Tieuloy, 1971 on the basis of its final falcate ribbing stage, which is formed by a fairly regular alternation of a main rib and a shorter intermediate rib. Te intermediate rib may arise from a fork from the previous rib. Nevertheless, the genus Breistrofferella is also distinguished by its subangusti-umbilical and ovoid section, a relatively narrow umbilicus, moderate umbilical bullae and external ribs tending to cross the ventral region by marking a provers chevron, on occasion accompanied by a superficial constriction, at any stage of growth.

" B." peyroulensis does not exhibit any of the aforementioned characteristics. Its whorl section is subquadratique to polygonal with a large smooth ventral band bordered by marginal tubercles. Te umbilic is clearly evolute, and its umbilical bullae are clearly developed. Its external ribs tend to cross the ventral region by marking a provers chevron only at the end of the body-chamber.

As mentioned by Atrops et al. (1996), the ornamentation of " B." peyroulensis , with its margino-ventral clavi and thickened primary ribs, is similar to that of the inner whorls of Acanthodiscus , which led these authors to consider the genus Breistrofferella as a possible microconch of Acanthodiscus (see also Reboulet, 1996). However, according to uncondensed stratigraphic records, both genera seem to not share the same stratigraphic range. Acanthodiscus covers the whole A. radiatus Zone , while " B." peyroulensis is only present with certainty in the upper A. radiatus Zone , L. buxtorfi Horizon. If this age of appearance of " B." peyroulensis proves to be correct, then it becomes difficult to consider Breistrofferella as the microconch of Acanthodiscus , not to mention their total difference in ornamentation at all ontogenetic stages. Although similar, " B." peyroulensis and Acanthodiscus have notable ornamental differences. In Acanthodiscus , the costal differentiation into main and multiple secondary ribs is very pronounced from the youngest whorls, with the ribs projecting forward markedly in the upper third of the flanks and the latero-ventral tubercles often clavate. In " B." peyroulensis , the costal differentiation is not clearly visible until the last whorl, mainly because the weakest rib is obliterated around the bifurcation point, the ribs project very markedly backwards on the upper third of the flanks and the latero-ventral tubercles are more conical.

As discussed, " B." peyroulensis is distinct from the genera Acanthodiscus and Breistrofferella and thus is attributed to a new genus, Jurienella gen. nov.

Stratigraphic repartition.? Upper part of the A. radiatus Zone and maybe the C. loryi Zone of western Switzerland and SE France.