Dirk Fuchs

Molecular clocks indicate turnover and diversification of modern coleoid cephalopods during the Mesozoic Marine Revolution

Coleoid cephalopod molluscs comprise squid, cuttlefish and octopuses, and represent nearly the entire diversity of modern cephalopods. Sophisticated adaptations such as the use of colour for camouflage and communication, jet propulsion and the ink sac highlight the unique nature of the group. Despite these striking adaptations, there are clear parallels in ecology between coleoids and bony fishes. The coleoid fossil record is limited, however, hindering confident analysis of the tempo and pattern of their evolution. Here we use a molecular dataset (180 genes, approx. 36 000 amino acids) of 26 cephalopod species to explore the phylogeny and timing of cephalopod evolution. We show that crown cephalopods diverged in the Silurian–Devonian, while crown coleoids had origins in the latest Palaeozoic. While the deep-sea vampire squid and dumbo octopuses have ancient origins extending to the Early Mesozoic Era, 242 ± 38 Ma, incirrate octopuses and the decabrachian coleoids (10-armed squid) diversified in the Jurassic Period. These divergence estimates highlight the modern diversity of coleoid cephalopods emerging in the Mesozoic Marine Revolution, a period that also witnessed the radiation of most ray-finned fish groups in addition to several other marine vertebrates. This suggests that that the origin of modern cephalopod biodiversity was contingent on ecological competition with marine vertebrates.

Adaptations to squid-style high-speed swimming in Jurassic belemnitids

Although the calcitic hard parts of belemnites (extinct Coleoidea) are very abundant fossils, their soft parts are hardly known and their mode of life is debated. New fossils of the Jurassic belemnitid Acanthoteuthis provided supplementary anatomical data on the fins, nuchal cartilage, collar complex, statoliths, hyponome and radula. These data yielded evidence of their pelagic habitat, their nektonic habit and high swimming velocities. The new morphological characters were included in a cladistic analysis, which confirms the position of the Belemnitida in the stem of Decabrachia (Decapodiformes).

Ancestry, Origin and Early Evolution of Ammonoids

In order to put the origin of the Ammonoidea into the broader evolutionary context, we review the hypothesis on the origin of cephalopods in general, the origin of bactritids as well as the origin of bactritids with their respective Bauplan characters. We also list major morphological changes that occurred between the origin of cephalopods until the early evolution of ammonoids.

New anatomical information on arms and fins from exceptionally preserved Plesioteuthis (Coleoidea) from the Late Jurassic of Germany

Plesioteuthis is a coleoid rather well known from the classical Fossillagerstätten of southern Germany (Solnhofen–Eichstätt region, Nusplingen). Here, we present two new specimens that display unusually preserved cirri-bearing arms and two pairs of fins. Based on these specimens, we shortly discuss in how far arm arrangement in the fossils might reflect behaviour. Additionally, we revise the phylogenetic position of the Jurassic vampyromorphs.

The gladiuses in coleoid cephalopods: homology, parallelism, or convergence?

In the cephalopod subclass Coleoidea, several homology problems exist, mainly owing to unsolved phylogenetic relationships between decabrachian orders. The present contribution reviews the “similarity” of the gladius, the chitinous shell rudiment in the dorsal mantle that provides rigid attachment sites for the locomotory-relevant musculature. As a secretion product of the shell sac epithelium as well as in the light of a common three-layered construction, both the octobrachian and the decabrachian gladius types most probably represent homologues with identical developmental mechanisms; “similarities” in gladius shapes in unrelated lineages therefore should be considered as the result of parallelism. Ultrastructural comparisons with Mesozoic coleoids suggest that an organic gladius is actually embedded in every proostracum-bearing phragmocone. It is therefore generally accepted that a gladius evolved through decalcification of a proostracum-bearing phragmocone. The character “gladius” accordingly represents a plesiomorphy within pro-ostracum-bearing coleoids. Whereas the gladius of Vampyroteuthis as well as the octopod fin supports indirectly derived from phragmoteuthid-like phragmocone via Mesozoic gladius types, the decabrachian gladius types can morphogenetically be linked with various ancestral groups (Belemnitida, Diplobelida, Groenlandibelidae, Vasseuria, Belosepiella). Experimental decalcification of a sepiid cuttlebone demonstrates furthermore that a gladius might have also evolved from a secondarily proostracum-less phragmocone. Life styles and habitats of living and Mesozoic gladius-bearing octobrachians are finally discussed in the light of our conclusions.

A nearly complete respiratory, circulatory, and excretory system preserved in small Late Cretaceous octopods (Cephalopoda) from Lebanon

Although they are rare, fossilized gills are well known in Mesozoic coleoid cephalopods. In the Late Jurassic Solnhofen (South Germany) and Late Cretaceous Hâkel and Hâdjoula (Lebanon) plattenkalks, the feather-like gill remains are usually preserved as a yellowish staining. Small coleoids from Hâkel—tentatively determined as octopods—attracted our attention because these stains occur throughout the entire mantle sac in an unusual symmetrical pattern. Actualistic comparisons point to a compound of diverse vascular structures that most likely reflect central parts of the venous blood system (afferent branchial vessels, branchial hearts, vena pallialis, blood sinus) as well as the nephridial sacs. The nephridial sacs are clearly separated, which confirms the octopod nature of the fossils. A reticulated staining pattern in the rear of the mantle, which may reflect the gonad capillary system, suggests the presence of mature small-sized octopods. Based on its colour, its amorphous habit, and energy-dispersive X-ray spectroscopy (EDX) elemental analyses, the major components of the coelomic cavities have been replicated by an iron-rich phase (presumably goethite; copper was not detected). The goethite does not replace the tissues; rather, it traces their gross form as a well-defined “stain”. It is assumed the goethite is secondary after pyrite, which precipitated as a consequence of the oxygen-binding capacity of the copper-bearing haemocyanin and its ability to locally regulate redox potentials immediately postmortem.KurzfassungFossilisierte Kiemen bei mesozoischen coleoiden Cephalopoden sind trotz allgemeiner Seltenheit gut bekannt. Die federförmigen Kiemenreste sind in den spätjurassischen und spätkretazischen Plattenkalken von Solnhofen (Süddeutschland) und Hâkel und Hâdjoula (Lebanon) üblicherweise als gelblich verfärbte Strukturen erhalten. Kleine Coleoiden aus Hâkel—provisorisch als Octopoden bestimmt—erweckten unser Interesse, weil die Verfärbungen auf ungewöhnliche Weise symmetrisch über den ganzen Mantelsack verteilt sind. Aktualistische Vergleiche deuten darauf hin, dass es sich hierbei um einen Verbund aus diversen vaskulären Strukturen handelt, die sehr wahrscheinlich zentrale Teile des venösen Blutsystems (afferente Kiemengefäße, Kiemenherze, Vena pallialis, Blutsinus) und der Nephridialsäcke widerspiegeln. Die klar voneinander getrennten Nephridialsäcke bestätigen, dass es sich tatsächlich um Octopoden handelt. Ein retikuläres Farbmuster im hinteren Mantelsackbereich könnte das Kapillarsystem der Gonaden darstellen, was darauf hindeuten würde, dass es sich hierbei um geschlechtsreife, kleinwüchsige Octopoden handelt. In Anbetracht von Farbe, amorphem Habitus und EDX-Analysen wurden die Hauptkomponenten der Coelomhöhlen durch eine eisenreiche Phase (vermutlich Goethit; Kupfer wurde nicht nachgewiesen) repliziert. Der Goethit ersetzte dabei nicht die Gewebe, sondern zeichnet vielmehr ihre Formen als klar umrissene Färbungen grob nach. Es wird vermutet, dass primär die Ausfällung von Pyrit eine Folge der Sauerstoffbindungskapazität von kupferbasierten Hämcyanin und dessen Fähigkeit ist, sofort nach dem Tod lokale Redoxpotentiale zu regulieren.

Amphispirula gen. nov. from the Eocene of southern Moravia (Czech Republic): a new ancestor of the Recent deep-sea squid Spirula?

A single specimen of an enigmatic coleoid cephalopod from the Eocene of southern Moravia (Czech Republic) represents the oldest record of a spirulid with a markedly, endogastrically coiled phragmocone. Distinctly oblique septa in Amphispirula gen. nov. show similarities to sepiid coleoids, but a ventrally closed siphuncle refers this taxon to the order Spirulida. The existence of a coiled phragmocone-bearing coleoid in the Eocene significantly precedes Miocene records of Spirulirostra – a guard-bearing coleoid, which is suggested to be ancestral to Recent Spirula. A mosaic of morphological features in Amphispirula might point to an older and unknown ancestor of modern Spirula, but more likely represents a new evolutionary lineage within spirulid cehalopods. http://zoobank.org/urn:lsid:zoobank.org:pub:BF5D1CBB-4AD4-4B54-9B45-07E224B24CF3

Grasping the shape of belemnoid arm hooks : a quantitative approach

Abstract. n Chitinous arm hooks (onychites) of belemnoid coleoid cephalopods are widely distributed in Mesozoic sediments. Due to their relative abundance and variable morphology compared with the single, bullet-shaped, belemnite rostrum, arm hooks came into the focus of micropaleontologists 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. Based on three well-preserved arm crowns of the Toarcian diplobelid Chondroteuthis wunnenbergi, we analyzed the shape of a total of 87micro-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 and along a single arm. Our quantitative data support former observations that smaller hookswere 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 hook morphotype. Here, we report the functional specialization of the belemnoid arm crown for the first time and speculate about the potential function of the four morphotypes based on comparisons with modern cephalopods. Our analyses suggest a highly adapted functional morphology and intra-individual distribution of belemnoid hooks serving distinct purposes mainly during prey capture.

The first coleoid cephalopods from the Upper Cenomanian of Sicily (Italy) and their implications for the systematic-phylogenetic position of the Palaeololiginidae (Teudopseina)

Our knowledge about the evolutionary history of coleoid cephalopods is mainly based on a few evolutionary windows. In particular, palaeogeographical data is strongly limited; every new fossil locality yielding coleoid remains is therefore of exceptional interest. Here, we describe the first coleoids from the Upper Cenomanian of Sicily (southern Italy). The material includes two fragmentary gladii, identified as Marekites nebrodensis sp. nov. and Rachiteuthis? sp. These two related taxa from the north-western Mediterranean region differ from most of their contemporaries in the south-eastern Mediterranean Lebanon fauna. Owing to their lanceolate posterior gladius, both taxa are classified as members of the Palaeololiginidae, a previously poorly defined family of Mesozoic gladius-bearing octobrachians. In the light of our observations, the family can now be characterized by its very gently arcuate hyperbolar zone, as well as the occurrence of a constriction of the median field. Marekites nebrodensis sp. nov. confirms that Cretaceous palaeololiginids share a relatively longer free (rachis-like) median field than their Jurassic forerunner Palaeololigo. Besides systematic-morphological implications, the higher level phylogenetic position of Paleololiginidae is discussed. In this context, we reject the idea of Palaeololiginidae as early bathyteuthoid decabrachians. http://zoobank.org/urn:lsid:zoobank.org:pub:075B36B1-2ECF-406F-AD99-79C98B06C271

First Middle–Late Jurassic gladius vestiges provide new evidence on the detailed origin of incirrate and cirrate octopuses (Coleoidea)

Limpet-like and non-mineralized fossils from the upper Kimmeridgian Nusplingen Plattenkalk are identified as internal shells of coleoid cephalopods, more specifically as octobrachian gladii. The significantly reduced median field provokes us to consider this new gladius type to be shorter than the mantle length. It is consequently seen as a vestigial gladius. The first recognition of an unpaired gladius vestige in the fossil record sheds new light on the evolutionary history of the gladius vestiges of incirrate and cirrate Octopoda. Patelloctopus ilgi sp. nov. is most similar to Callovian Pearceiteuthis buyi in having a rudimentary median field with an extraordinary large opening angle and radiating ribs on the lateral fields. Both P. ilgi sp. nov. and P. buyi are therefore combined in the new family Patelloctopodidae. The patella-shaped lateral fields of the gladius vestige exposes Patelloctopus and Pearceiteuthis as members of the superfamily Muensterelloidea, which includes, apart from Patelloctopodidae, the Muensterellidae and Enchoteuthidae. The unpaired patelloctopodid gladius vestige is morphologically intermediate between the muensterelloid gladius type and the paired (bipartite) gladius vestige of Late Cretaceous Palaeoctopodidae (Palaeoctopus, Keuppia). The gladius vestige morphology suggests that the mode of locomotion and the life style of these shallow water inhabitants were similar to those of extant deep-sea octopods (Cirrata) and that the Patelloctopodidae represents the stem group of the Octopoda (Cirrata and Incirrata), although Patelloctopus ilgi sp. nov. might alternatively be a stem incirrate.KurzfassungNapfschnecken-artige und nicht mineralisierte Fossilien aus dem Nusplinger Plattenkalk (Ober-Kimmeridgium) werden als die Innenschale coleoider Cephalopoden gedeutet, genauer als ein Gladius der Octobrachia. Das signifikant reduzierte Mittelfeld lässt uns annehmen, dass dieser neue Gladius-Typ kürzer gewesen sein muss als die Mantellänge. Er ist deswegen als Gladiusrest anzusehen. Die erste Entdeckung von unpaaren Gladiusresten im Fossilbericht gibt neue Aufschlüsse über die Evolutionsgeschichte der Gladiusreste von incirraten und cirraten Octopoda. Wegen seines rudimentären Mittelfeldes, dessen außergewöhnlich großen Öffnungswinkels und radiärer Rippen auf den Seitenfeldern ähnelt Patelloctopus ilgi sp. nov. am meisten Pearceiteuthis buyi aus dem Callovium. Patelloctopus ilgi sp. nov. and Pearceiteuthis buyi werden deswegen in der neu aufgestellten Familie Patelloctopodidae vereinigt. Die Patella-artig geformten Lateralfelder des Gladiusrestes lassen Patelloctopus und Pearceiteuthis eindeutig als Mitglieder der Superfamilie Muensterelloidea erkennen, in der neben den Patelloctopodidae die Muensterellidae und die Enchoteuthidae zusammengefasst sind. Morphologisch kann der unpaare Gladiusrest der mittel- und spätjurassischen Patelloctopodidae als intermediäres Stadium zwischen einem muensterelloiden Gladius und den paarigen (zweiteiligen) Gladiusresten der spätkretazischen Palaeoctopodidae (Palaeoctopus, Keuppia) angesehen werden. Die Morphologie des unpaaren Gladiusrestes lässt vermuten, dass sich die Art der Fortbewegung und die Lebensweise dieser Flachwasserbewohner denen heutiger Tiefseeoctopoden (Cirrata) ähnelte und dass ferner die Patelloctopodidae die Stammgruppe der Octopoda (Cirrata und Incirrata) darstellt, obwohl alternativ dazu Patelloctopus ilgi sp. nov. schon ein Stammgruppenvertreter der Incirrata gewesen sein könnte.