Wien, Februar 1997

1-15

Ann. Naturhist. Mus. Wien

Adaptyxis n.gen. (Umboniidae, Nerineacea, Gastropoda)
from the Mirdita Zone of Albania;
remarks on the early phylogeny of the Nerineacea

by Heinz A. KOL MANN* k, Luftulla H. PEZA**

(With 2 plates)

Manuscript submitted on October 1", 1996,
the revised manuscript on November 18'", 1996

Summary

Based on material from the Barremian/Aptian of Albania, the nerineacean Adaptyxis n. gen. is described. It possesses high turriculate shells with concave whorls of moderate height. Because of the hollow columella it is assigned to the Umboniidae LvssENvo & ALtEv. The columella is hollow. Of the internal plaits, the adapical columellar plait is very small. The other columellar plait, the palatal plait and the parietal plait are strong. Because of the internal morphology, Adaptyxis is considered as transitional between the genus Affiniptyxis LvssENKo & AUEv and Plesioploeus PcHELtNTsEv. Synchronously, Neoptyxis PcHEUNrsEv evolved from Affiniptyxis. Both genera are part of the Simploptyxidae HAKoBJAN. An origin of the Umboniidae and the Ptygmatidae from a Melanioptyxis-like group in the Jurassic is considered. It is not clear whether the Nerineidae originated from the same group as the other nerineacean families or from the Mathildoid family Anoptychoidae, as was postulated by BANAL (1995).

Xusammenfassung

Aufgrund von Material aus dern BarremiumiAptium Albaniens wird die Gattung Adaptyxis n.gen. beschrie- ben. Vertreter dieser Gattung besitzen hohe, turrikulate Gehause mit ma8ig hohen, konkaven Umgangen. Die Columella ist breit und hohl. Unter den Internfalten ist die adapikale Columellafalte sehr klein. Die andere Columellarfalte, sowei die Parietal- und Palatalfalte sind kraftig. Wegen der hohlen Spindel sowie der Anzahl und der Grogenverhaltnisse der Internfalten wird Adoptyxis als evolutives Zwischenglied von der zu den Umboniidae gehorigen Gattung Affiniptyxis LvssENKo & At.JEv zu Plesioplocus angenommen. Die Differenzierung zwischen Plesioplocus PcHELtNrsEv und Neoptyxis PcHELJNrsEv erfolgte in einem friihen Stadium des Ubergangs. Beide Gattungen gehoren der Familie Simploptyxidae HAtcoa>AN an. Der Ursprung der Umboniidae und der Ptygmatidae von einer mit Melanioptyxis nahe verwandten Gruppe wird diskutiert. Es ist unklar, ob der Ursprung der Familie Nerineidae in der selben Gruppe liegt oder ob sie von der den Mathildoidea angehorigen Familie Anoptychoidae abstammt, wie es von BANDEL (1995) angenommen wird.

1. Introduction

In Upper Cretaceous nerineaceans the columella is solid or possesses only narrow cavi- ties. This applies to the Nerineidae including the Nerinellidae and the Simploptyxidae

Naturhistorisches Museum, P.O.Box 417, A-1014 Wien. — Austria.

** Czech Academy of Sciences, Geological Institute, Rozvojova 135, CS-16500 Praha 6. — Czech Republic.

2 Annolen des lvaturhistorischen Museums in Wien 98 A

HAKQBJAN (1976). The Eunerineidae, with Funevinea Cox (Nevi nea DEFRANCE in CossMANN, 1896 and others) and Diptyxis OPPENHEIM, possess a single columellar plait. Representatives of the Simploptyxidae have two columellar plaits. HAKOBJAN (1976) considered Plesioplocus PCHELINTsEv, Simploptyxis TIEDT, Pavasimploptyxis HAKQBJAN, Haploptyxis HAKoBJAN, and Plesioptygmatis BoESE as members of this family. According to HAKOBJAN, all other genera evolved from Plesioploeus, which it- self had its origin in the "Diozoptyxisidae" in the sense of PCHELINTsEv (1931, 1965). Neoplyxis was not included into the Simploptyxidae by HAKoBJAN.

In the Mirdita Zone of Albania, nerineaceans with morphological characters of both the Umboniidae and the Simploptyxidae have been found by PEzA and his co-workers. They therefore provide direct evidence on the origin of the Simplopyxidae as it was assumed by HAKQBJAN. This material, which does not correspond to any of the known nerinea- cean genera, is described in the present paper.

2. Geological setting