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Retispira undata

Gastropoda - Bellerophontida - Bellerophontidae

Taxonomy
Bellerophon decussatus undatus was named by Etheridge (1876). It is not extant.

It was recombined as Bucaniopsis undatus by Weir (1931); it was recombined as Bucanopsis undatus by Moore (1958); it was recombined as Retispira undata by Peel (2016) and Wagner (2017).

Synonymy list
YearName and author
1876Bellerophon decussatus undatus Etheridge, Jr. p. 155 figs. pl. 9 f. 9-10
1878Bellerophon decussatus undatus Etheridge p. 19 figs. pl. 2 f. 30
1931Bucaniopsis undatus Weir pp. 826 - 827 figs. pl. 4 f. 13-16
1958Bucanopsis undatus Moore p. 142
2016Retispira undata Peel p. 416 figs. 6C, D, G–J, M–O
2017Retispira undata Wagner p. S6381

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Protostomia
Spiralia
Schizocoela
phylumMollusca
classGastropodaCuvier 1797
RankNameAuthor
orderBellerophontidaUlrich and Scofield 1897
suborderBellerophontina
superfamilyBellerophontoidea()
familyBellerophontidae
subfamilyKnightitinae
genusRetispira
speciesundata()

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Diagnosis
ReferenceDiagnosis
J. Weir 1931Shell subglobose, aperture expanded (but without exaggeration of the expansion as in B. striatus). Umbilicus narrow. Surface of the shell thrown into a number of irregular folds at the prominent growth halts. Tho ornament is a reticulation of closely set ribs; the transcrescent ribs are irregular and somewhat flexuous, and occur in two or even three orders of size; these orders may be in fairly regular alternation or irregularly distributed; the concrescent ribs are strongly curved. Band flat on top, somewhat elovated in the young shell, later depressed in a shallow hollow of the dorsum; ornament of the band consists of irregular, closely set transcrescont ribs intersecting curved concrescent ribs, which disappear in the latest stages.
J. S. Peel 2016Species of Retispira with uniformly convex dorsum and a rate of whorl expansion of about 3.5, measured from the width of successive whorls (Fig. 6M). Aperture reniform in crosssection (Fig. 6M), its margin periodically slightly flared in latest growth stage to produce dorsal undulations in larger specimens (Fig. 6N, O). A low median pad of inductura is deposited on the floor of the whorl covering the dorsum of the previous whorl (Fig. 6G). Dorso-lateral apertural margins almost straight near the umbilici (Fig. 6J) but becoming increasingly convex, adaperturally (Fig. 6C, H–J, N, O), prior to passage into a broad but shallow median sinus and a short slit which generates a flat-topped selenizone bounded by spiral cords (Fig. 6N, O). Selenizone varies between slightly depressed to raised, but becomes raised in the final growth stage (Fig. 6C, O). Selenizone ornamented by a single median cord (Fig. 6D, H) which becomes inconspicuous in the latest growth stage (Fig. 6N, O), crossed by numerous concave lunulae. Ornamentation dominated by spiral cords, usually of two size orders, crossed by growth lines and forming small nodes at the intersections; additional spiral elements introduced as fine threads between pre-existing cords. Growth lines becoming more pronounced and lamellar in later growth stages (Fig. 6J, N, O), accompanied by comarginal undulations.