Taxonomy and palaeoecology of Cretaceous nautilids Angulithes galea (Fritsch in Fritsch and Schlönbach, 1872) and Angulithes westphalicus (Schlüter, 1872)

Abstract

Taxonomy and palaeoecology of Cretaceous nautilidsAngulithes galea (Fritsch in Fritsch & Schlönbach, 1872) and Angulithes westphalicus (Schlüter, 1872) JIØÍ FRANKAngulithes galea (Fritsch in Fritsch & Schlönbach, 1872) and Angulithes westphalicus (Schlüter, 1872) are representatives of Angulithes Montfort, 1808, occurring in the Late Cretaceous of Europe, from the Late Turonian to the Late Campanian. Following examination of the majority of specimens representing these species and their specific morphology, a detailed revision was made. Both species undergo significant morphological changes during their ontogeny, changing the shape of the ventral side and whorl cross-section attended by onset and loss of ventral keel and changing of the shell surface (by A. galea). Comparing these changes with the ontogeny of recent Nautilus suggests they are expressions of the approach and attainment of maturity. Due to this comparison, comparable changes in other taxa can be similarly interpreted, e.g. representatives of the genus Deltocymatoceras. The changes undergone by A. galea are at maturity accompanied by additional features such as strong radial ribbing, which is comparable with the ribbing in Deltocymatoceras. The affinity (ventral keel, suture, ontogeny and stratigraphy) of this genus with Angulithes is a topic for discussion.•

The endemic and morphologically remarkable nautilid genus Deltocymatoceras Kummel, 1956 from the Late Cretaceous of Central Europe

“…37-38) supported separation of Deltocymatoceras and Angulithes, but he proposed keeping the two genera in one family, Nautilidae Blainville, 1825. We agree with the interpretation that Deltocymatoceras is derived from Cymatoceras but we are also aware of inconsistencies in the systematics of the family Cymatoceratidae (Tintant 1989, Frank 2010. The relative importance of traits such as radial ribbing, the suture, the keel or the position of the siphuncle for systematic classification is still under debate.…”

“…In this paper we discuss the phylogeny of the genus and its affinity to Cymatoceras [see Kummel 1956; probably C. radiatum (Sowerby, 1822) Despite the low diversity of Deltocymatoceras with only two species and its limited geographic distribution, it is retained as a separate genus based on its specific morphological characters. Ontogenetic trends during the acquisition of maturity are comparable to those documented in recent nautilids (Collins & Ward 1987, Frank 2010. Nevertheless, mature shell modifications are more common and more strongly developed in several early Palaeozoic nautiloids (e.g.…”

“…The most noticeable difference is the lack of radial ribbing in A. westphalicus which has a smooth surface covered only by growth lines. An exception is the early Late Turonian Angulithes galea (Fritsch & Schlönbach, 1872), in which strong radial rib-like-folds appear in the adapertural area in the late premature stage, followed by a reduction of the keel (Frank 2010). This keel reduction is similar in D. leiotropis and D. rugatum.…”

“…In the same epoch as Deltocymatoceras, nautilids with prominent ventral keels such as Angulithes and with various types of radial ribbing such as Cymatoceras occurred. However, only Angulithes galea (Fritsch & Schlönbach, 1872; see discussion in Frank 2010) displays this combination of characters on the last third of the living chamber of mature shells. Furthermore, the fold-like-ribs of A. galea occur when the keel is reduced and disappeared.…”

Silicified sea life – Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany)

“…However, Kummel (1956Kummel ( , 1964, Wiedmann (1960), and Dzik (1984) presented significant contributions to the taxonomy and systematics of post-Triassic nautiloids while Shimansky (1975) and Matsumoto et al (1984) focused mainly on Cretaceous taxa and their phylogeny. Nevertheless, familyand genus-level classifications are still controversial, especially with respect to the family Cymatoceratidae Spath, 1927 Frank 2010;and Frank et al 2013). Here, the classification of Shimansky (1975) is followed (grouping of most 'cymatoceratid' genera with the family Nautilidae Blainville, 1825).…”