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A possible fossil paralarva (Cephalopoda: Coleoidea) from the Solnhofen Lithographic Limestones (Upper Jurassic, southern Germany)

Joachim T. Haug, Isabelle Kruta and Carolin Haug

Plain Language Abstract

The first possible fossil remains of a (para-)larva of a cephalopod (e.g., cuttlefish, octopuses) were discovered in the Upper Jurassic Solnhofen Lithographic Limestones from southern Germany, which are ca. 150 million years old. The fossil is three millimetres long and leaf-shaped, consisting of mainly the central part of the pen, which is related to the cuttlebone in cuttlefish. Parts of the lateral areas are faintly preserved. The middle line is marked by a sharp keel, a pear-shaped structure is present posteriorly (the side opposing the arms). On the opposite, anterior side the pen has a kite-shaped area bearing small pits. This general morphology is, for example, similar to certain trachyteuthids, exclusively fossil coleoid cephalopods from different Jurassic and Cretaceous deposits. Also resemblances to certain other Jurassic coleoids (muensterellids) are pointed out. The special morphology of the here described specimen is interpreted as special characters of an early developmental stage. This together with its small size makes its very likely that the new fossil is a paralarva, although we cannot provide the evidence from its ecology usually necessary for this assignment. As there is no similarly small comparative material available, the exact systematic identification of the new specimen is currently not possible.

Resumen en Español

Una posible paralarva fósil (Cephalopoda, Coleoidea) de las calizas litográficas de Solnhofen (Jurásico superior, sur de Alemania)

Se describe un posible gladius fragmentario de un cefalópodo paralarval de las calizas litográficas de Solnhofen (Alemania meridional, Jurásico superior, Titónico inferior). El ejemplar tiene 3 mm de longitud y forma de hoja, y corresponde principalmente al campo medio del gladius, aunque existen también restos apenas perceptibles de los campos laterales. La línea media está marcada por una quilla aguda. En el extremo posterior se encuentra una estructura piriforme, mientras que en el anterior se observa un área con forma deltoidea ornamentada con pequeñas fosetas. Teniendo en cuenta la forma general, la presencia de una quilla y la región anterior deltoidea y ornamentada, el gladius se asemeja al de ciertos Trachyteuthididae, aunque algunos caracteres también son similares a los de los Muensterellidae. La especial morfología del ejemplar descrito se interpreta como consecuencia de su estadio ontogenético, lo que, unido a su pequeño tamaño, nos hace pensar que se trate de un ejemplar paralarval, aunque no podemos aportar las necesarias evidencias ecológicas en favor de esa atribución. Tampoco es posible una clara asignación sistemática, dado que no existe material comparable de tan pequeño tamaño.

Palabras clave: paleo-evo-devo; cefalópodos; gladius; ontogenias fosilizadas; larva; microscopía de fluorescencia

Traducción: Miguel Company

Résumé en Français

Une possible paralarve fossile (Cephalopoda: Coleoidea) des calcaires lithographiques de Solnhofen (Jurassique supérieur, sud de l'Allemagne)

Nous décrivons un possible gladius fragmentaire de céphalopode paralarvaire provenant des calcaires lithographiques de Solnhefen (Jurassique supérieur, Tithonien inférieur). Le spécimen fait 3mm de long et est en forme de feuille, représentant principalement le champ médian du gladius. De faibles restes indiquent l'ancienne position des champs latéraux. La ligne médiane est marquée par une quille anguleuse. Sur la partie postérieure il y a une structure en forme de pointe. Antérieurement, une surface en forme de cerf-volant est ornementée avec de petits trous. La morphologie principale ressemble, par exemple, a certains trachyteuthididés, sur la base de la forme, de la présence de la quille et de la région antérieure en forme de cerf-volant ornementée. La ressemblance avec certains caractères de muensterellidés est également mise en évidence. La morphologie spéciale du spécimen décrit est interprétée comme due à des causes ontogénétiques.

Ces observations de même que la petite taille attribuent à ce spécimen un statut paralarvaire potentiel, bien que nous ne puissions pas fournir les preuves écologiques de cette assignation. Une attribution claire à un quelconque groupe systématique est empêchée par le fait qu'il n'existe aucun matériel de taille similaire disponible pour comparaison.

Mots clés : paléo-évo-dévo ; céphalopodes ; gladius ; ontogénies fossilisées ; larve ; microscopie par fluorescence

Translator: Olivier Maridet

Deutsche Zusammenfassung

Eine mögliche Paralarve (Cephalopoda: Coleoidea) aus den Solnhofener Plattenkalken (Oberjura, Süddeutschland)

Wir beschreiben hier ein mögliches unvollständiges Gladius der Paralarve eines Kopffüßers aus den Solnhofener Plattenkalken, Süddeutschland (Oberjura, Untertithon). Das Fossil ist blattförmig und etwa drei Millimeter lang. Erhalten ist vor allem das mediane Feld des Gladius, die lateralen Felder sind nur undeutlich und unvollständig erhalten. Die Mediane ist durch einen prominenten Kiel gekennzeichnet, der posterior in eine birnenförmige Struktur übergeht. Anterior befindet sich eine mit kleinen Gruben ornamentierte Fläche in Form eines Drachenvierecks. Die grundlegende Morphologie erinnert beipielsweise an manche Trachyteuthiden, vor allem in der Form, im Vorhandensein eines prominenten medianen Kiels und der ornamentierten Fläche in Form eines Drachenvierecks. Auch manche Muensterelliden zeigen diese Merkmale. Die ungewöhnliche Morphologie des hier beschriebenen Fossils interpretieren wir als Folge seines frühen ontogentischen Stadiums. Auch aufgrund der geringen Größe des Fossils halten wir es für wahrscheinlich, dass das Fossil eine Paralarve ist, auch wenn die erforderlichen ökologischen Informationen fehlen. Eine sichere systematische Zuordnung des Fossils ist zur Zeit nicht möglich; andere Stücke vergleichbarer Größe sind bisher nicht bekannt.

Schlüsselwörter: Palaeo-Evo-Devo; Cephalopoda; Gladius; fossilisierte Entwicklung; Larve; Fluoreszenzmikroskopie.

Translators: Authors

Arabic

322 arab

Translator: Ashraf M.T. Elewa

 

 

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author1University of Greifswald
Zoological Institute and Museum
Department of Cytology and Evolutionary Biology
Soldmannstr. 23
17487 Greifswald
Germany

Joachim T. Haug studied animal ecology (major), sociobiology and palaeontology (minors) at the Julius-Maximilians-Universität Würzburg. After the receipt of the Diplom in 2005, he moved to the work group Biosystematic Documentation at the University of Ulm for his PhD thesis. There he worked on the early crustaceans from the Cambrian 'Orsten', which are preserved three-dimensionally and with minute details. To make the entire morphology clearly visible, Joachim produced computer-based 3D models for each developmental stage of a species, resulting in a 4D model of the species. With 4D models reconstructed for the different species, differences in the developmental pattern between the species became visible. These changes in the developmental timing, so-called heterochronic events must have occurred several times during early crustacean evolution. Due to these findings, Joachim got interested in studying such evolutionary changes of development also in fossils from other deposits and focussed on Palaeo-Evo-Devo (see also http://www.palaeo-evo-devo.info). After his defense in 2009 and two further years as postdoctoral researcher in Ulm, he received a Feodor Lynen research fellowship from the Alexander von Humboldt-Foundation, with which he went to Yale University and returned to Germany, now doing research at the University of Greifswald. Besides 3D modelling, Joachim is also interested in different methods of imaging (documentation and presentation).

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author2Yale University
Department of Geology and Geophysics
PO Box 208109
New Haven, Connecticut 06520-8109
USA
and
American Museum of Natural History
Division of Paleontology (Invertebrates)
New York, New York 10024
USA

Isabelle Kruta studied at University Modena e Reggio Emilia and obtained both her diploma (MD- 2007) and Ph.D (2011) at the Museum d’Histoire Naturelle in Paris. She got postdoctoral training at Yale University and at the American Museum of Natural History (AMNH). Her research interest is on cephalopod paleobiology and more specifically on exceptional preservation of soft tissue in ammonites. Among several techniques she uses Synchrotron µCT in order to reconstruct elements that are present in the body chamber of the animal. Her aim is a better understanding of the ecology of this group as well as new insights in phylogeny.

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author3University of Greifswald
Zoological Institute and Museum
Department of Cytology and Evolutionary Biology
Soldmannstr. 23
17487 Greifswald
Germany

Carolin Haug studied biology at the Julius-Maximilians-Universität Würzburg with animal ecology as major subject and sociobiology and palaeontology as minor subjects. She received her Diplom in 2005 and moved to the University of Ulm for her PhD thesis. In the work group Biosystematic Documentation she investigated the ontogeny and evolution of the arthropod head shield on a wide spectrum of fossil and extant specimens. Due to the very different demands of the material, she developed new imaging techniques or modified existing methods together with her collaborators, for example, composite imaging, stereo photography or autofluorescence macro- and microscopy. In 2011, Carolin defended her PhD thesis. She was at Yale University as postdoctoral researcher and is currently at the University of Greifswald. Besides optimising imaging techniques, she is interested in fossilised development (see also http://www.palaeo-evo-devo.info) and in the evolution of tagmosis. For this purpose, she investigates mainly arthropods from different deposits yielding exceptional preservation, such as Rhynie chert, Solnhofen Lithographic Limestones, the 'Orsten', Burgess Shale, or Mazon Creek, always in comparison to their extant relatives.

 

FIGURE 1. Comparison of gladius shapes between older (1.1, 1.3) and younger stages (1.2, 1.4) of the same species of Coleoidea. 1.1-2. Gladii of Onykia robusta (Verrill, 1876). Gladius of younger stage much stouter than that of older stage. Redrawn after Tsuchiya and Okutani (1991, figures 18, 19). 1.3-4. Gladii of Pholidoteuthis massyae (Pfeffer, 1912), exhibiting shape differences between the different stages. Redrawn after O'Shea et al. (2007, figures 36, 37).

 figure 1

FIGURE 2. The supposed gladius of a fossil cephalopod paralarva (SMNS 67904b), documented with different methods. 2.1. Macrograph under North-West lighting. 2.2. Autofluorescence micrograph. Note the lateral field and the pits, forming a reticulate pattern. 2.3. Red-cyan stereo image with pronounced keel and pits; use red-cyan glasses to view. Abbreviations: ap = apex; ke = keel; lf = lateral field; p = pitted area.

 figure 2

FIGURE 3. 3D models of the gladii of the supposed new paralarva and its posssible adult (red-cyan stereo images). Images not to scale to show the different length-width ratios. 3.1. Gladius of the possible paralarva presented in this paper. The faint areas represent the only partially preserved lateral fields. 3.2. Gladius of the keeled type of Trachyteuthis with morphological similarities to that of the possible paralarva.

 figure 3