Early Cretaceous ribbed aptychi – a proposal for a new systematic classification

Abstract

The older system for classification of ribbed calcareous Early Cretaceous aptychi consisted of two genera:<i>Punctaptychus</i> and <i>Lamellaptychus</i>. Later, I. Turculet divided <i>Lamellaptychus</i> into several subgenera. Within the frameworkof both the genera, species and subspecies were distinguished, which resulted in binominal and trinominal nomenclature.With regard to the richness of newly described species and subspecies in recent years, is not possible to continueusing the original system. It is the basic ribbing that plays the decisive role in the generic and subgeneric classificationof ribbed aptychi. In the case of subspecies systematics, all details on the valve surface are used with the exceptionof the sigmoidal bend <i>(fractocostatus)</i> and radial lines <i>(radiatus)</i>. The ribbed aptychi are newly divided into the followingfamilies: Punctaptychidae fam. nov. and Lamellaptychidae fam. nov. Within the family Punctaptychidae we are ableto distinguish two genera: <i>Punctaptychus</i> Trauth, 1927 and <i>Cinctpunctaptychus</i> gen. nov. The family Lamellaptychidaeincludes five genera differing in the basic arrangement of the ribs: <i>Lamellaptychus</i> Trauth, 1927, <i>Beyrichilamellaptychus</i>Turculet, 1994, <i>Mortilletilamellaptychus</i> gen. nov., <i>Thorolamellaptychus</i> Turculet, 1994 and<i>Didayilamellaptychus</i> Turculet, 1994. Eight species and one subspecies are established as new: <i>Cinctpunctaptychusundulatus, Beyrichilamellaptychus pseudostuderi, Mortilletilamellaptychus mortilletioides, M. submortilleti noricus,M. stanislavi, Didayilamellaptychus hennigi, D. andrusovi</i> and <i>D. renzi</i&gt

Biostratigraphy of the Lower Cretaceous Schrambach Formation on the classical locality of Schrambachgraben (Northern Calcareous Alps, Salzburg Area)

“…-The valve was found in the area of the right tributary downstream, on the level of approximately 122 m in the thickness of section. Typical specimens of M. stanislavi occur, according to Měchová et al (2010), in the Early Valanginian.…”

“…Later, Lamellaptychus was divided by Turculet (1994) into subgenera. Only recently, a proposal for a new classification of ribbed Lower Cretaceous aptychi (Měchová et al 2010) was submitted, respecting the basic ribbing and nomenclatoric rules. We follow this classification.…”

Late Jurassic aptychi from the La Caja Formation of northeastern Mexico

“…Similar to L. latus and other related taxa of the genus, concentric lines and radial lines and wrinkles of irregular strength and distribution are also present (Trauth, 1931). However, the occurrence of radial lines is related to an exceptionally favourable type of preservation (Měchová et al, 2010). The outer margin is short, strongly convex; it curves towards the apex close to the harmonic margin.…”

“…According to Trauth (1931, p. 77), the most characteristic feature for the subspecies L. (Latuslaevaptychus) latus meyrati is the presence of concentric and/or radial rings of unequal width and distribution on the convex side, which are also visible in our specimens. However, the occurrence of radial lines was interpreted by Měchová et al (2010) to be related to an exceptionally favourable type of preservation. Similar concentric rings are also present in L. longus, L. favrei and L. meneghinii var.…”

“…Lamellaptychus is well known from the Bajocian-Valanginian of the Tethyan Realm (e.g., Carpathians, Gąsiorowski, 1962;France, Fischer, 2003;Spain, Calzada, 1985; distribution summarized by Měchová et al, 2010). Trauth, 1929;Villaseñor and González-Arreola, 1988).…”