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Belemnitid proostracum and phragmocone with soft parts and with Psiloceras planorbis Sowerby 1824, PIMUZ 27078, Planorbis Zone, Hettangian (Early Jurassic), Blue Anchor (Watchet, Somerset, southern England), leg. Gisela and Friedrich König (Oberbözberg, Switzerland). A. Detail of D, showing details of the ink sac and duct as well as the posterior lateral field. B. Detail of D, showing the questionable nuchal cartilage and the anterior tip of a lateral field. C. Detail of D, showing the complete belemnitid remains. D. Most of the slab, showing the absence of imprints of a thick rostrum and the complete, adult specimen of Psiloceras planorbis as well as a conspecific juvenile.
Source publication
A new specimen of an earliest Hettangian (Jurassic) belemnite (Coeloidea, Cephalopoda) is described herein. It displays the complete, typically belemnitid proostracum, the ink sac with its duct, questionable remains of the nuchal cartilage, and half of the phragmocone. Since the apical part of the phragmocone is missing, it is unclear what kind of...
Contexts in source publication
Context 1
... entire specimen measures 70.2 mm in length and 15.6 mm in width (at the anterior end of the lateral fields). It is dorsoventrally flattened but, as is usual at this locality, is preserved with aragonitic remains ( Figures 1A, 2). Since the ink sac and duct overlie the aragonitic phragmocone and proostracum remains, the specimen is visible from its ventral side. ...
Context 2
... proostracum is roughly 50 mm long and nicely displays the straight and pointed lateral fields ( Figure 1C). The posterior portions of the lateral fields are, in their deformed state, approximately 5 mm wide. ...
Context 3
... ink sac largely lies on the phragmocone remains and is preserved as an oval depression of a maximum length of 10 mm ( Figure 1A). It contains some fossil ink remains. ...
Citations
... Belemnites are extinct coleoid cephalopods, i.e., relatives of modern squids, cuttlefishes and octopuses (Fuchs 2006;Kröger et al. 2011;Iba et al. 2012Iba et al. , 2014Klug et al. 2016;Hoffmann et al. 2016. With the ten-armed coleoids, the decabrachians, they share an internal skeleton largely surrounded by a muscular mantle, a large brain compared to other invertebrates, ten arms, chitinous jaws, large lateral eyes, and a predatory mode of life (e.g., Naef 1922;Reitner and Urlichs 1983;Doguzhaeva et al. 2002Doguzhaeva et al. , 2003Weis and Delsate 2006;Klug and Fuchs 2010;Klug et al. 2010aKlug et al. , b, 2016Keupp and Mitta 2015;Clements et al. 2016;Donovan & Fuchs 2016;Klug and Tajika 2018;Wani et al. 2018;Jenny et al. 2019;. In contrast to other hard parts, the low magnesium calcite rostra of belemnites represent abundant fossils in the Jurassic and Cretaceous, sometimes occurring in rock-forming numbers (Doyle and Macdonald 1993;Rita et al. 2018). ...
Although belemnite rostra can be quite abundant in Jurassic and Cretaceous strata, the record of belemnite jaws was limited to a few specimens from Germany and Russia. Here, we describe and figure three cephalopod jaws from the Middle Jurassic Opalinus Clay of northern Switzerland. Although flattened, the carbonaceous fossils display enough
morphological information to rule out an ammonoid, nautiloid or octobrachian origin of the two larger jaws. Their similarities to belemnite jaws from Germany and Russia conforms with our interpretation of these specimens as belemnite jaws. Based on their rather large size, we tentatively assign these two jaws to the megateuthidid Acrocoelites conoideus. The third jaw is a rather small upper jaw of an ammonoid. Since Leioceras opalinum is by far the most common ammonite in this unit in northern Switzerland, we tentatively suggest that the upper jaw belongs to this species.
... Fossil ammonites predominate the cephalopod faunas through much of the Lower Jurassic succession along the West Somerset coast and in parts of the sequence are ubiquitous, whereas coleoid remains are extremely rare (Klug and Fuchs 2010). As elsewhere in the UK, the occurrence of very early Jurassic nautilids is relatively uncommon and only two species are currently known to occur on the West Somerset coast: Cenoceras malherbii (Terquem) from the Hettangian Stage (Liasicus and Angulata zones) and C. intermedium (Sowerby) from the Sinemurian Stage (Bucklandi and Semicostatum zones). ...
Substantial numbers of the nautilid Cenoceras occur in a stratigraphically limited horizon within the upper part of the Lower Jurassic (Sinemurian Stage) Blue Lias Formation at Watchet on the West Somerset Coast (United Kingdom). Individual nautilid conchs are associated with clusters of encrusting organisms (sclerobionts) forming ‘islands’ that may have been raised slightly above the surrounding substrate. Despite the relatively large numbers of nautilid conchs involved, detailed investigation of their preservation suggests that their accumulation reflects a reduction in sedimentation rates rather than an influx of empty conches or moribund animals. Throughout those horizons in which nautilids are present in relative abundance, the remains of ammonites are subordinate or rare. The reason for this unclear, and preferential dissolution of ammonite conchs during their burial does seem to provide a satisfactory solution to the problem.
... In our material, there is a single individual showing a pair of indistinct oval imprints in the anterior mantle region. Judged from its medial position one might assume the presence of a bipartite nuchal-locking cartilage (Fig. 9C,D; see Klug & Fuchs 2010). ...
A morphological comparison of shell-muscle contacts in coleoid cephalopods mainly from the Early Jurassic (Toarcian) Posidonia Shales of Holzmaden (Germany), the Middle Jurassic (Callovian) Oxford Clay of Christian Malford (UK), Late Jurassic (Kimmeridgian-Tithonian) plattenkalks of Solnhofen (Germany), and the Late Cretaceous (Cenomanian) of Hâdjoula and Hâkel (Lebanon) provides new and meaningful insights into their locomotion systems. The study shows that both pro-ostracum- and gladius-bearing coleoids are typified by a marginal mantle attachment and by distinctly separated fins, which usually insert (indirectly via the shell sac and basal fin cartilages) to posterior shell parts. While absent in gladius-bearing forms, mantle-locking cartilages might have existed already in pro-ostracum-bearing belemnoids. Similar to ectocochleate ancestors, funnel- and cephalic retractors are generally attached to the internal (ventral) shell surface. A comparison of Mesozoic and Recent gladius-bearing coleoids shows that the locomotion system (most significantly the dorsal mantle configuration, and the presence of nuchal- and funnel-locking cartilages) is fundamentally different. This does not support the concept of ‘fossil teuthids’, but suggests, owing to similarities with Recent Vampyroteuthis, placement of Mesozoic gladius-bearing coleoids within the Octobrachia (Octopoda + Vampyromorpha). Classification of Mesozoic gladius-bearing coleoids as octobrachians implies that: (1) unambiguous teuthids are still unknown in the fossil record and (2) the similarity between Recent and some fossil gladiuses represents a matter of homoplasy.
... These are the oldest belemnites so far known, and Schwegleria (Fig. 3M) was considered as a possible stockgroup of all belemnites (e.g., Doyle, 1994;Weis and Delsate, 2006). Occurrences of Hettangian proostraca and arm hooks of belemnites are also known from northern Europe, southern England, southwest Germany, and Luxembourg (e.g., Weis and Delsate, 2006;Klug and Fuchs, 2010). It has been concluded that the belemnites evolved in Europe as small forms in the Hettangian; their distribution was restricted to the European shelf seas until the Pliensbachian for 18 m.y. ...
Belemnites (order Belemnitida), a very successful group of Mesozoic cephalopods, provide an important clue for understanding Mesozoic marine ecosystems and the origin of modern cephalopods. Following current hypotheses, belemnites originated in the earliest Jurassic (Hettangian, 201.6-197 Ma) with very small forms. According to this view their paleobiogeographic distribution was restricted to northern Europe until the Pliensbachian (190-183 Ma). The fossil record is, however, biased by the fact that all the previous studies on belemnites focused on Europe. Here we report two belemnite taxa from the Hettangian of Japan: a new species of the Sinobelemnitidae and a large taxon of the suborder Belemnitina. The Sinobelemnitidae, which may be included in the future in a new suborder, have also been recorded from the Triassic of China, specimens so far poorly understood. The presence of a very large rostrum attributed to the Belemnitina suggests in addition that a diverse belemnite fauna evolved earlier than previously thought. Our new findings therefore (1) extend the origin of the belemnites back by similar to 33 m.y. into the Triassic, (2) suggest that this group did not necessarily originate in northern Europe, and (3) imply that belemnites survived the Triassic-Jurassic extinction, one of the five big mass extinctions in the Phanerozoic. Since belemnites provided a considerable amount of food as prey, the origination of belemnites is probably an important event also for the evolution of their predators, such as marine reptiles and sharks.
This chapter reviews the ammonoid taphonomy, especially focusing on recent advances in various methodologies (including new data on necrosis and fossil diagenesis of organic components and experimental techniques with modern analogues). Aspects on necrosis and fossil diagenesis of organic components in ammonoids are discussed based on the comparison of the jaw compositions between two modern cephalopods and four fossil cephalopods from the Upper Cretaceous of North America and Japan. Ammonoid taphonomy, especially biostratinomic processes (waterlogging, implosion, post-mortem surfacing, transport on the seafloor, deformation after sedimentation in soft sediments, shell fragmentation, transportation of jaws), is reviewed from various experimental analyses with modern analogues (e.g., experimental approaches with modern nautilus shells or plastic models, hydrostatic calculations). This chapter also reviews the diagenetic processes (compaction and dissolution), the exceptional preservation, and preservation styles of ammonoids in various rocks (clastic and carbonate rocks).
The systematic study of new belemnite assemblages from the Central Apennines and western Sicily revealed several new taxa for Italy. The specimens originate from Lower Jurassic sediments (Sinemurian–Toarcian), and their exact stratigraphic occurrence can be established by accompanying ammonite assemblages. The systematic analysis allows six genera of the suborder Belemnitina to be recognised (Subhastites, Passaloteuthis, Pseudohastites, Bairstowius, Cuspiteuthis, Megateuthis). The coeval occurrence of heterogeneous canaliculate belemnites (with alveolar grooves) was unexpected; their partially incomplete preservation does not allow assigning them safely to any existing genus, with the exception of a well-preserved specimen of Pachybelemnopsis sp. (with phragmocone, protoconch, and siphuncle). This represents the earliest known record of a belemnopseine belemnite. The Italian canaliculate belemnites are tentatively compared with canaliculate belemnites from the European Peri-Tethys, Japan, and New Zealand. A direct comparison is, however, hampered by the incomplete preservation of most of the
herein reported specimens. The records of canaliculate belemnites in the Early Jurassic of Italy show remarkably heterogeneous rostrum morphologies, indicating an earlier
diversification in belemnites than previously assumed.
Klug, C., Schweigert, G., Fuchs, D. & Dietl, G. 2009: First record of a belemnite preserved with beaks, arms and ink sac from the Nusplingen Lithographic Limestone (Kimmeridgian, SW Germany). Lethaia, 10.1111/j.1502-3931.2009.00203.x
A recent discovery of an unusually preserved belemnite from Nusplingen comprises the extraordinarily rare remains of beaks and nearly in situ arm hooks, as well as the ink sac and an incomplete phragmocone. So far, Hibolithes semisulcatus (Münster, 1830) is the only belemnite known from the Nusplingen Lithographic Limestone (Upper Jurassic, Late Kimmeridgian, Beckeri Zone, Ulmense Subzone; SW Germany) that has the same phragmocone shape and size, and thus we assign the new specimen to this taxon. The rostrum was probably lost due to a lethal predation attempt in which the prey was killed but not entirely eaten. For the first time a specimen reveals details of the belemnite beak morphology, which we compare with the beaks of other Jurassic coleoids. This specimen presently represents the only known rostrum-bearing belemnite of post-Toarcian age with preserved non-mineralized body parts. With the new discovery, Nusplingen now represents the only locality which has yielded complete beak apparatuses from all major Jurassic cephalopod groups. □Beaks, Belemnitida, Coleoidea, Germany, Late Jurassic, morphology, taphonomy.
