Acanthoteuthis problematica Naef, 1922, an almost forgotten taxon and its role in the interpretation of cephalopod arm armatures

Fuchs, Dirk; Heyng, Alexander M.; Keupp, Heiner

doi:10.1127/0077-7749/2013/0347

Cited by 6 publications

(12 citation statements)

References 9 publications

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“…First, we provide for the first time direct evidence for the existence of 10 arms of equal length in Chondroteuthis . Second, we observed that hooks in Chondroteuthis are arranged in a single row, which is in contrast to the biserial arrangement in all other known belemnoid taxa with articulated arm crowns (e.g., compare with Engeser and Clarke 1988; Fuchs et al 2010, 2013a,b). According to the uniserial arrangement of hooks and the assumed maximum number of hooks per arms (i.e., about 20–40), in Chondroteuthis the maximum number of hooks per arm crown ranges between 200 and 400 micro-hooks.…”

Section: Discussioncontrasting

confidence: 56%

“…A belemnoid arm crown is composed of 10 arms, each equipped with up to 40 pairs of chitinous micro-hooks, that is, hooks rarely larger than 5 mm, resulting in 200–800 micro-hooks per specimen (Engeser 1987; Engeser and Clarke 1988). Published records of belemnoid micro-hooks mainly refer to Jurassic deposits (e.g., Münster 1834, 1839; Owen 1844; Quenstedt 1849; Engeser and Reitner 1981; Reitner and Engeser 1982; Reitner and Urlichs 1983; Engeser 1987; Urlichs et al 1994; Riegraf 1996; Klug et al 2010, 2016; Fuchs et al 2013a,b), while Cretaceous findings were first reported by Riedel (1936) and are rare in comparison (Engeser and Suthhof 1992; Reich and Frenzel 1997; Reich 2002; Mitta and Bogomolov 2014). The rarity of reports on Cretaceous coleoid hooks may reflect a form of selection bias, as it is believed that they occur more abundantly but have often been overlooked, possibly due to lack of interest by researchers (Reich and Frenzel 1997; Reich 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Complete or incomplete arm crowns associated with the remaining parts of the belemnoid specimen provide important paleobiological insights, particularly with respect to functional morphology, systematics, and taxonomy. Examples include the Late Triassic Phragmoteuthis (Rieber 1970; Doguzhaeva et al 2007); Early Jurassic Sueviteuthis (Reitner and Engeser 1982), Acrocoelites , Passaloteuthis (Reitner and Urlichs 1983), and Clarkeiteuthis (Quenstedt 1849; Riegraf 1996; Fuchs et al 2013a,b; see Garassino and Donovan [2000] for an extended list); and Middle to Late Jurassic Belemnotheutis (Owen 1844; Donovan and Crane 1992), Acanthoteuthis (Engeser and Reitner 1981), Winkleriteuthis (Fuchs et al 2013a) and Hibolithes (Klug et al 2010). Individuals of the above-mentioned species develop arms of similar length, and their arms are equipped with micro-hooks of similar shape.…”

Section: Introductionmentioning

confidence: 99%

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Grasping the shape of belemnoid arm hooks—a quantitative approach

Hoffmann¹,

Weinkauf²,

Fuchs³

2017

Paleobiology

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Chitinous arm hooks (onychites) of belemnoid coleoids are widely distributed in Mesozoic sediments. Due to their relative abundance and variable morphology compared to the single, bullet-shaped belemnite rostrum, arm hooks came into the focus of micropalaeontologist as a promising index fossil group for the Jurassic-Cretaceous rock record and have been the target of functional, ecological, and phylogenetic interpretations in the past (e.g. Reitner & Engeser 1982;Fuchs et al. 2013;Hammer et al. 2013). Based on three well-preserved arm crowns of the Toarcian diplobelid Chondroteuthis wunnenbergi, we analyzed the shape of a total of 87 micro-hooks. The arm crown of Chondroteuthis is unique in having uniserial (rather than biserial) hooks. The first application of elliptic Fourier shape analysis to the arm weapons of belemnoid coleoids allows for the distinction of four micro-hook morphotypes and the quantification of shape variation within these morphotypes. Based on the best preserved arm crown, we reconstructed the distribution of morphotypes within the arm crown as well as along a single arm. Our quantitative data support former observations that smaller hooks were found close to the mouth and at the most distal arm parts, while the largest hooks were found in the central part of the arm crown. Furthermore, we found a distinct arm differentiation, as not every arm was equipped with the same hookmorphotypes. Here, we report the functional specialisation of the belemnoid arm crown for the first time and speculate about the potential function of the four morphotypes. Our analyses suggest a highly adapted functional morphology and intra-specimen individual distribution of belemnoid hooks, serving distinct purposes mainly during prey capture, prey digestion, as well as reproduction. In this regard, hooks at the distal end of the arms show stronger curvature to effectively catch and hold the prey, while hooks closer to the belemnoids mouth are more suitable for prey dissection and for transporting food to the mouth. We speculate that this highly specialised arrangement is an adaptation of Chondroteuthis towards its uniserial hook-arrangement. This is supported by the fact that belemnoids with biserial hook armament do not show interindividual changes in micro-hook morphology (Engeser 1987).

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Section: Discussioncontrasting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Grasping the shape of belemnoid arm hooks—a quantitative approach

Hoffmann¹,

Weinkauf²,

Fuchs³

2017

Paleobiology

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“…Until now, arguments supporting octobrachian affinities were mainly based on negative characters such as the absence of tentacles, tentacular pockets, toothed or hooked sucker rings, and rudimentary septation of the conus or rostrum (Bandel & Leich ; Fuchs , ; Fuchs et al . , ,c; Fuchs & Larson ,b; Arkhipkin et al . ).…”

Section: Methodsmentioning

confidence: 99%

“…Other characters not related to the locomotion system such as ‘absence of sucker rings (hooked or teethed)’ in Mesozoic gladius‐bearing coleoids would have likewise indicated a convergent evolution in decabrachian subgroups (Fuchs et al . ,c). Assumption of homoplasy in each of these complex characters is here regarded as implausible (see discussions above).…”

Section: Methodsmentioning

confidence: 99%

The locomotion system of Mesozoic Coleoidea (Cephalopoda) and its phylogenetic significance

Fuchs

Iba

Tischlinger³

et al. 2016

LET

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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.

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New evidence from exceptionally “well-preserved” specimens sheds light on the structure of the ammonite brachial crown

Smith

Landman

Bardin³

et al. 2021

Sci Rep

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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 of these structures revealed that they belong to the ammonites. Their nature, however, remained elusive. Here, we exploit tomographic data to study their arrangement in space in order to clarify this matter. After using topological data analyses and comparing their morphology, number, and distribution to other known cephalopod structures, in both extant and extinct taxa, we conclude that these hook-like structures represent part of the brachial crown armature. Therefore, it appears that there are at least three independent evolutionary origins of hooks: in belemnoids, oegospids, and now in ammonites. Finally, we propose for the first time a hypothetical reconstruction of an ammonite brachial crown.

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Acanthoteuthis problematica Naef, 1922, an almost forgotten taxon and its role in the interpretation of cephalopod arm armatures

Cited by 6 publications

References 9 publications

Grasping the shape of belemnoid arm hooks—a quantitative approach

Grasping the shape of belemnoid arm hooks—a quantitative approach

The locomotion system of Mesozoic Coleoidea (Cephalopoda) and its phylogenetic significance

New evidence from exceptionally “well-preserved” specimens sheds light on the structure of the ammonite brachial crown

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