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Examples of extinct belemnoid onychites. (A) Hook bearing belemnoid specimen, AMNH 046611. (B) Close up image of AMNH 046611, brachial crown. (C) Schematic drawing of a fossil arm hook with particular morphological elements and their terminology modified from Kulicki & Szaniawski 34 . (D-) Examples of different onychites identified by Kulicki & Szaniawski 34 : Falcuncus falcus onychites (a); Longuncus longus onychites (b); Paraglycerites gracilis onychites (c); Deinuncus brevirostris onychites (d).
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Ammonite soft body remains are rarely preserved. One of the biggest enigmas is the morphology of the ammonite brachial crown that has, up till now, never been recovered. Recently, mysterious hook-like structures have been reported in multiple specimens of Scaphitidae, a large family of heteromorph Late Cretaceous ammonites. A previous examination o...
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Context 1
... a doublesided opening (Fig. 4). Hooks in extinct cephalopods (onychites) such as Belemnitida, Donovaniconida, and Phragmoteuthida are also elongate, unicuspid, and curved. They differ from modern decabrachian hooks by often presenting a small spur on their left or right side and having only a single-sided slanted opening at their base 23,25,34 (Fig. ...
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... fall in the same size range as those in modern decabrachians 35 and belemnoids 12,36 . Morphotypes 2 and 4 in R. halli are similar in morphology to some of the bicuspid hooks of Taonius pavo 37,38 (Fig. 4D,E). Morphotypes 1 and 5 in R.halli resemble onychites with well-developed lateral shafts such as the onychites of Paraglycerites (Fig. ...
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... is plausible the structures in Rhaeboceras halli served the same function. One hypothesis is that R.halli developed some sort of ambush hunting strategy in which the hooks were used to clasp small prey despite being slow swimmers 54-56 , as perhaps suggested by the co-occurrence of hooks and fish remains preserved together in a single concretion (Fig. S5). Further work must however be conducted before being able to elucidate the exact function of these hooks, as grasping devices for mating remains, among others, a plausible hypothesis. Nonetheless, these structures are the very first ammonite brachial crown elements described, considerably improving our knowledge about the evolution of ...
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... hooks occur inside the body chamber and although some of them are visible on the surface (Fig. 2A,B), most of them are still embedded in the matrix. We observed only one occurrence of hooks not in connection with an ammonite; the hooks are preserved in a small limestone concretion (15 cm in length) associated with a nearly complete fish skeleton (Fig. S5). The nature of this co-occurrence remains however unclear. A high proportion of the specimens with hooks also retain the jaws inside the body chamber (Table S2), which is interpreted as evidence of rapid burial after ...
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... Specifically for extinct cephalopods like the ammonoids, this kind of technical innovations have been key to the description of structures which would have been rarely found in this group otherwise. Examples include the employment of a wide variety of tomographic techniques such as grinding tomography, X-ray microtomography, synchrotron tomography, and neutron tomography (e.g., Hoffmann et al., 2013;Tajika et al., 2015;Takeda et al., 2016;Kruta et al., 2020;Cherns et al., 2021;Smith et al., 2021;Tanabe et al., 2021), laser-induced fluorescence (Barlow et al., 2021), and digitization techniques such as surface or 3D scanning and photogrammetry (Peterman et al., 2019(Peterman et al., , 2020. Ammonoids are extinct cephalopods that appeared during the Early Devonian and went extinct at the Cretaceous/Paleogene boundary, with a few members eventually surviving into the earliest Paleogene . ...
We report on remains of the buccal apparatus and possible associated structures for the Late Cretaceous ammonite Maorites
seymourianus from the López de Bertodano Formation (Antarctic Peninsula). This is the first description of these structures for the family
Kossmaticeratidae. Further, we discuss the most likely taphonomic processes taking place that allowed this exceptional preservation.
Reflectance Transformation Imaging (RTI) technique was employed in this work to better document the faint structures. We briefly provide a
review of this method and its potential importance for paleontological studies because it seems that this powerful technique has been largely
overlooked by paleontologists.
... Overall, the cuvature of the structure differs strongly from Type A fossils. From a superficially viewpoint, these elements may resemble the megahook-like structures of brachial crowns which are known from some Mesozoic ammonoids [60,61]. Moreover, some of these structures from Polzberg show an extended "base"(which more closely resembles cartilage-elements than hooks). ...
Although hyaline cartilage is widely distributed in various invertebrate groups such as sabel-lid polychaetes, molluscs (cephalopods, gastropods) and a chelicerate arthropod group (horseshoe crabs), the enigmatic relationship and distribution of cartilage in taxonomic groups remains to be explained. It can be interpreted as a convergent trait in animal evolution and thus does not seem to be a vertebrate invention. Due to the poor fossil record of car-tilaginous structures, occurrences of mineralized fossil cartilages are important for evolutionary biology and paleontology. Although the biochemical composition of recent cephalopod cartilage differs from vertebrate cartilage, histologically the cartilages of these animal groups resemble one another remarkably. In this study we present fossil material from the late Triassic Polzberg Konservat-Lagerstä tte near Lunz am See (Lower Austria, Northern Calcareous Alps). A rich Carnian fauna is preserved here, whereby a mor-phogroup (often associated with belemnoid remains) of black, amorphous appearing fossils still remained undetermined. These multi-elemental, symmetrical fossils show remarkable similarities to recent cartilage. We examined the conspicuous micro-and ultrastructure of these enigmatic fossils by thin-sectioning and Scanning Electron Microscopy (SEM). The geochemical composition analyzed by Microprobe and Energy Dispersive X-ray Spectros-copy (SEM-EDX) revealed carbonization as the taphonomic pathway for this fossil group. Mineralization of soft tissues permits the 3D preservation of otherwise degraded soft tissues such as cartilage. We examined eighty-one specimens from the Polzberg locality and seven specimens from Cave del Predil (formerly Raibl, Julian Alps, Italy). The study included morphological examinations of these multi-elemental fossils and a focus on noticeable structures like grooves and ridges. The detected grooves are interpreted to be muscular attachment areas, and the preserved branched system of canaliculi is comparable to a channel system that is also present in recent coleoid cartilage. The new findings on these long-known enigmatic structures strongly point to the preservation of cephalic cartilage belonging to the belemnoid Phragmoteuthis bisinuata and its homologization to the cephalic cartilage of modern coleoids.
... Overall, the cuvature of the structure differs strongly from Type A fossils. From a superficially viewpoint, these elements may resemble the megahook-like structures of brachial crowns which are known from some Mesozoic ammonoids [60,61]. Moreover, some of these structures from Polzberg show an extended "base"(which more closely resembles cartilage-elements than hooks). ...
Although hyaline cartilage is widely distributed in various invertebrate groups such as sabellid polychaetes, molluscs (cephalopods, gastropods) and a chelicerate arthropod group (horseshoe crabs), the enigmatic relationship and distribution of cartilage in taxonomic groups remains to be explained. It can be interpreted as a convergent trait in animal evolution and thus does not seem to be a vertebrate invention. Due to the poor fossil record of cartilaginous structures, occurrences of mineralized fossil cartilages are important for evolutionary biology and paleontology. Although the biochemical composition of recent cephalopod cartilage differs from vertebrate cartilage, histologically the cartilages of these animal groups resemble one another remarkably. In this study we present fossil material from the late Triassic Polzberg Konservat-Lagerstätte near Lunz am See (Lower Austria, Northern Calcareous Alps). A rich Carnian fauna is preserved here, whereby a morphogroup (often associated with coleoid remains) of black, amorphous appearing fossils still remained undetermined. These multi-elemental, mirroring fossils show remarkable similarities to recent cephalopod cartilage. We examined the conspicuous micro- and ultrastructure of these enigmatic fossils by thin-sectioning and Scanning Electron Microscopy (SEM). The geochemical composition analyzed by Microprobe and Energy Dispersive X-ray Spectroscopy (SEM-EDX) revealed carbonisation as the taphonomic pathway for this fossil group. 3D preservation of this otherwise degradable soft tissue can be explained by the mineralization processes that may take place in particular environments. Fifty-nine specimens from the Polzberg locality and five specimens from Cave del Predil (formerly Raibl, Julian Alps, Italy) underwent extensive studies. The detected grooves are interpreted to be muscular attachment areas, and the preserved branched system of canaliculi is comparable to a channel system that is also present in recent coleoid cartilage. The new findings on these long-known enigmatic structures strongly point to the preservation of cranial cartilage belonging to the belemnoid Phragmoteuthis bisinuata .
... "It thus appears conceivable that a belemnoid morphogenotype provided the basis for the alternative modifications of only one arm pair at two different occasions during coleoid evolution" (Boletzky, 2002, p. 13). The revived idea of belemnitid and diplobelid belemnoids as sucker-bearing ancestors of decabrachians, new insights about the chemistry of sucker surfaces (e.g., Miserez et al., 2009) as well as discoveries of ammonoid arm hooks (Kruta et al., 2020;Smith et al., 2021) reopen a series of questions that will be addressed here. When did suckers originate? ...
... Hook-like structures have been described repeatedly from Late Cretaceous ammonites (Kennedy et al., 2002;Kruta et al., 2013Kruta et al., , 2020Landman & Waage, 1993). These structures were found in body chambers of the scaphitids Hoploscaphites and Rhaeboceras from the Campanian and Maastrichtian of the US-American Western Interior (Kruta et al., 2020;Smith et al., 2021). Based on X-ray studies, Smith et. ...
... ly from Late Cretaceous ammonites (Kennedy et al., 2002;Kruta et al., 2013Kruta et al., , 2020Landman & Waage, 1993). These structures were found in body chambers of the scaphitids Hoploscaphites and Rhaeboceras from the Campanian and Maastrichtian of the US-American Western Interior (Kruta et al., 2020;Smith et al., 2021). Based on X-ray studies, Smith et. al. (2021) confirmed the existence of five morphotypes, which are generally typified by unicuspidate or bicuspidate uncini (Fig. 2m, n). The arrangement, chirality, paired occurrences and presence in many specimens is good evidence that these structures indeed belong to the ammonites. Their linear arrangement and similarity to belemnoid and oegops ...
The cephalopod arm armature is certainly one of the most important morphological innovations responsible for the evolutionary success of the Cephalopoda. New palaeontological discoveries in the recent past afford to review and reassess origin and homology of suckers, sucker rings, hooks, and cirri. Since a priori character state reconstructions are still ambiguous, we suggest and discuss three different evolutionary scenarios. Each of them is based on the following assumptions: (1) Neocoleoidea uniting extant Decabrachia and Octobrachia is monophyletic (= proostracum-bearing coleoids); (2) extinct Belemnitida and Diplobelida are stem decabrachians; (3) proostracum-less coleoids (Hematitida, Donovaniconida, Aulacoceratida) represent stem-neocoleoids; (4) Ammonoidea and Bactritoidea are stem coleoids. We consider a scenario where belemnoid hooks derived from primitive suckers as well-supported. Regarding belemnoid hooks and suckers as homologues implies that belemnoid, oegopsid, and probably ammonoid arm hooks arose through parallel evolution. Our conclusions challenge the widespread opinion, whereupon belem-noid hooks evolved de novo, and instead support earlier ideas formulated by Sigurd von Boletzky.
... In fossil cephalopods, exceptional taphonomic pathways led to soft-tissue preservation in some Jurassic coleoids through phosphatization or carbonization (Allison, 1988;Wilby et al., 2004;. By contrast, in contemporaneous ammonoids, soft-part anatomy is primarily inferred from muscle-attachment scars inside the shell (Mironenko, 2014) and hard parts housed in the buccal mass and associated with feeding (Keupp and Mitta, 2013;Klug and Lehmann, 2015;Smith et al., 2021); indigestible (skeletal) remnants suggest a crop and stomach (Jäger and Fraaye, 1997). The only known soft tissues from Jurassic ammonites are fragments of mantle and possibly gills in a cadoceratid (Mironenko, 2015), and detached, flattened body masses of jaws and organs outside perisphinctid shells . ...
The extreme rarity of soft-tissue preservation in ammonoids has meant there are open questions regarding fundamental aspects of their biology. We report an exceptionally preserved Middle Jurassic ammonite with unrivaled information on soft-body organization interpreted through correlative neutron and X-ray tomography. Three-dimensional imaging of muscles and organs of the body mass for the first time in this iconic fossil group provides key insights into functional morphology. We show that paired dorsal muscles withdrew the body into the shell, rather than acting with the funnel controlling propulsion as in Nautilus. This suggests a mobile, retractable body as a defense strategy and necessitates a distinct swimming mechanism of hyponome propulsion, a trait that we infer evolved early in the ammonoid-coleoid lineage.
Die Ammoniten, eine ausgestorbene Gruppe der
Kopffüßer, sind die wichtigsten Leitfossilien für
den marinen Ablagerungsbereich vom Devon
bis zum Ende der Kreide. Ihre schnelle Entwick�lung neuer Merkmale, Häufigkeit und globale
Verbreitung sowie gut überlieferungsfähige Kar�bonatschalen machen die Ammoniten zu idea�len Zeitmessern für die Rekonstruktion erdge�schichtlicher Vorgänge. Sie gehören zu den häu�figsten und artenreichsten Fossilien überhaupt.
Im starken Gegensatz zu ihrer biostratigraphi�schen Bedeutung steht das sehr begrenzte Wis�sen über die Lebensweise dieser Organismen
(Klug & Lehmann 2015). So ist bis heute relativ
wenig darüber bekannt, wovon sich Ammoniten
ernährten und wer ihre Fressfeinde waren.
Die Rekonstruktion fossiler Nahrungsnet�ze ist eine der spannendsten, aber zugleich
auch schwierigsten Herausforderungen in der
Paläobiologie. Der vorliegende Beitrag ver�sucht anhand überlieferter Mageninhalte auf
das Beutespektrum mesozoischer Ammoniten
aus Plattenkalklagerstätten zu schließen. Eben�falls wird die generelle Stellung der Ammoniten
in Nahrungsnetzen diskutiert. Seit ihrem Ur�sprung im frühen Devon (Klug & Lehmann 2015)
waren Ammoniten sowohl als Räuber als auch
als Beute über 300 Mio. Jahre lang ein wichtiger
Bestandteil des marinen Ökosystems. Bisher
wurde eine ganze Reihe direkter und indirekter
Versuche unternommen, um ihre Position in
den Nahrungsnetzen zu rekonstruieren.
