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Late Jurassic marine vertebrates are extraordinarily well preserved in several Plattenkalk Lagerstätten in central Europe. Among them, the Solnhofen Archipelago has yielded the very rare fish Coccolepis bucklandi, which was the first fossil chondrostean to be found in sediments younger than the Triassic. The type specimen of this species was lost, but it was rediscovered recently, prompting the alpha taxonomic revision of this iconic fish. A new species Coccolepis solnhofensis has been identified among the specimens referred to C. bucklandi. The two species differ in the distinctive distribution of scutes and fringing fulcra. Based on the available evidence, C. bucklandi is restricted to the Eichstätt Basin and the Lithacoceras eigeltingense ß Horizon of the Lithacoceras riedense Subzone (Hybonoticeras hybonotum Zone), and C. solnhofensis sp. nov. is limited to the Solnhofen Basin and the slightly younger Subplanites rueppellianus Subzone (Hybonoticeras hybonotum Zone). Therefore, the two species are geographically and stratigraphically separated. The diagnosis of Coccolepis is improved with the addition of new characters, and the genus is here restricted to the two early Tithonian species from the Solnhofen Archipelago. Among the four species previously described or referred to Coccolepis, the generic assignment of “Coccolepis” australis and “Coccolepis” liassica, remains unclear. Sunolepis yumenensis is here returned to its original genus, and the new combination Condorlepis woodwardi is proposed for this Early Cretaceous coccolepidid from Australia.

International audience; Sea spiders (Pycnogonida) are strange arthropods characterized by a unique morphology, including reduced body, egg-carrying appendages and a proboscis. This peculiar body plan dates at least as early as the first undoubted occurrence of the group, 425 million years ago in the Silurian. All extant species belong to the order Pantopoda, characterized by cylindrical legs and an unsegmented abdomen. Palaeozoic fossils are much more diversified and exhibit features very different from pantopod morphology such as a segmented abdomen, limbs specialized to swim, or even a flagellum. The few Mesozoic fossils from the single Jurassic palaeoenvironment of La Voulte-sur-Rhône (south-eastern France) instead have strong affinities to Pantopoda. Here, we investigate the morphology of nine sea spider fossils using a new photographic protocol to document morphology, combining focus stacking and differential colourization. We also describe two new species of fossil pycnogonids from the Late Jurassic of Solnhofen (southern Germany): Colossopantopodus nanus sp. nov. is closely allied to a large species from La Voulte-sur-Rhône, but distinct in its smaller size; the other, ?Eurycyde golem sp. nov., is the first known fossil representative of the extant family Ascorhynchidae. Seven additional specimens, too poorly preserved for taxonomic description, are illustrated. The comparisons reveal that the shallow lagoons of Solnhofen contained a diverse assemblage of pantopods. Altogether with the fauna of La Voulte-sur-Rhône, the results suggest that Pantopoda became the dominant pycnogonid taxon of both deep and shallow marine waters after the Jurassic.

Sea spiders are a class of marine arthropods including more than 1,400 species. Their diversity and evolutionary history are still poorly known. In this thesis, tropical pycnogonids were studied using four approaches: (i) nine fossils from Solnhofen (Upper Jurassic) were examined using a new photographic technic improving visualization of body parts; (ii) for phylogeny, CO1 and 18S genes were analyzed for 107 taxa; (iii) 103 new mitochondrial genomes were assembled after Illumina shotgun sequencing; and (iv) 803 sea spiders collected during the Madibenthos expedition (2016) in Martinique were examined for integrative taxonomy using 172 CO1 sequences.All fossils from Sonhofen are shown to share strong affinities with the modern fauna, as they were identified as belonging to Pantopoda. Two new species are described. Together with fossils from La Voulte-sur-Rhône, these results suggest that Pantopoda were already diversified in shallow and deep Jurassic waters, indicating that an important faunal transition occurred between Palaeozoic and Mesozoic. The mitochondrial genome of sea spiders shows many different gene orders and most of the gene rearrangements involve tRNA genes. Some are correlated with changes in base composition bias, which can be misleading for phylogenetic reconstruction. Despite these problems, all families but Ascorhynchidae, Callipallenidae and Nymphonidae were found to be monophyletic. Furthermore, our analyses provide evidence for several interfamilial relationships (between Ammotheidae, Pallenopsidae, Endeidae and Phoxichilidiidae; and between Callipallenidae and Nymphonidae), and for many intergeneric and interspecific relationships. While only 20 pycnogonid species were previously known from Martinique, the number of species was multiplied by four after our study, i.e. 73. These results suggest that many species still remain to be discovered in the Caribbean Sea, whereas this region was thought to be well-explored regarding sea spiders., Les pycnogonides sont une classe d’arthropodes marins comptant plus de 1 400 espèces, et dont nous connaissons mal la diversité et l’histoire évolutive. Cette thèse pluridisciplinaire sur les pycnogonides tropicaux s’articule autour de quatre axes de recherche : (i) description de neuf fossiles de Solnhofen (Jurassique supérieur), grâce à une nouvelle technique de visualisation des volumes ; (ii) analyses phylogénétiques des gènes CO1 et 18S à partir de 107 taxons ; (iii) séquençage Illumina par shotgun et assemblage de 103 nouveaux génomes mitochondriaux ; et (iv) taxonomie intégrative des pycnogonides de Martinique reposant sur 803 spécimens collectés lors de l’expédition Madibenthos (2016) et 172 séquences CO1. Tous les fossiles de Solnhofen étudiés sont rattachés aux pantopodes, marquant leur affinité avec la faune moderne. Deux espèces nouvelles sont décrites. Avec les fossiles de La Voulte-sur-Rhône, ils montrent que les pantopodes étaient déjà diversifiés dans des eaux profondes et lagunaires du Jurassique, suggérant une importante transition de faune entre Paléozoïque et Mésozoïque. De nombreux réarrangements du génome mitochondrial, impliquant principalement les gènes des ARNt, sont mis en évidence. Certains sont corrélés à des changements dans le biais de composition en bases qui peuvent impacter la reconstruction phylogénétique. Malgré ces problèmes, nous retrouvons la monophylie de toutes les familles excepté les Ascorhynchidae, Callipallenidae et Nymphonidae, et identifions des regroupements interfamiliaux, d’un côté entre Ammotheidae, Pallenopsidae, Endeidae et Phoxichilidiidae, et de l’autre, entre Callipallenidae et Nymphonidae. Un très grand nombre de relations intergénériques et interspécifiques est également révélé. Alors que 20 espèces étaient auparavant connues sur les côtes de Martinique, cette étude a permis de multiplier par quatre la diversité connue de l’île, soit un total de 73 espèces. Ces résultats suggèrent une diversité encore plus importante à l’échelle des Caraïbes, que l’on pensait pourtant bien explorées.

International audience; Polychelidan lobsters (Decapoda: Polychelida) are crustaceans with extant species which are restricted to deep water environments. Fossil species, however, used to live in more varied palaeoenvironments, from shallow water to deep water, and were more diverse morphologically. We redescribe two species of polychelidan lobsters, the Late Triassic Rosenfeldia triasica Garassino, Teruzzi & Dalla Vecchia, 1996 and the Late Jurassic Eryon oppeli Woodward, 1866, recently assigned to the same genus, Rosenfeldia, based upon only a few characters. Our investigation of all available material of both species leads us to distinguish these two species and to erect Rogeryon gen. nov. to accommodate Eryon oppeli. The palaeobiology of both species is interpreted for the first time. Rosenfeldia triasica with its stout first pereiopods and mandibles with both incisor and molar processes (documented for the first time in Polychelida) was benthic and probably fed either on slow-moving sedentary preys or was a scavenger. Rogeryon oppeli gen. et comb. nov. was benthic, visually adapted to shallow water palaeoenvironments, and possibly had a diet similar to that of slipper lobsters and horseshoe crabs. The redescription of these two species highlights the palaeobiological diversity of fossil polychelidans.

Larvae of malacostracan crustaceans represent a large fraction of modern day zooplankton. Plankton is not only a major part of the modern marine ecosystem, but must have played an important role in the ecosystems of the past as well. Unfortunately, our knowledge about plankton composition of the past is still quite limited. As an important part of today’s zooplankton, malacostracan larvae are still a rarity in the fossil record; many types of malacostracan larvae dominating the modern plankton have so far not been found as fossils. Here we report a new type of fossil malacostracan larva, found in the 150 million years old lithographic limestones of southern Germany (Solnhofen Lithographic Limestones). The three rather incomplete specimens mainly preserve the telson. A pronounced middle spine on the posterior edge of these specimens indicates that they are either larval forms of a clawed lobster or of an axiidean lobster, or of a closer relative to one of the two groups. The tergo-pleura are drawn out into distinct spines in one specimen, further supporting the interpretation as a larva of a clawed lobster or an early relative. The telson morphology also shows adaptations to a prolonged planktic life style, the latero-posterior edges are drawn out into distinct spines. Similar adaptations are known in larvae of the modern homarid lobsterNephrops norvegicus, not necessarily indicating a closer relationship, but convergent life styles. The new finds provide an important new insight into the composition of Mesozoic zooplankton and demonstrate the preservation potential of lithographic limestones.

International audience; BACKGROUND: Modern representatives of Polychelida (Polychelidae) are considered to be entirely blind and have largely reduced eyes, possibly as an adaptation to deep-sea environments. Fossil species of Polychelida, however, appear to have well-developed compound eyes preserved as anterior bulges with distinct sculpturation. METHODS: We documented the shapes and sizes of eyes and ommatidia based upon exceptionally preserved fossil polychelidans from Binton (Hettangian, United-Kingdom), Osteno (Sinemurian, Italy), Posidonia Shale (Toarcian, Germany), La Voulte-sur-Rhône (Callovian, France), and Solnhofen-type plattenkalks (Kimmeridgian-Tithonian, Germany). For purposes of comparison, sizes of the eyes of several other polychelidans without preserved ommatidia were documented. Sizes of ommatidia and eyes were statistically compared against carapace length, taxonomic group, and outcrop. RESULTS: Nine species possess eyes with square facets; Rosenfeldia oppeli (Woodward, 1866), however, displays hexagonal facets. The sizes of eyes and ommatidia are a function of carapace length. No significant differences were discerned between polychelidans from different outcrops; Eryonidae, however, have significantly smaller eyes than other groups. DISCUSSION: Fossil eyes bearing square facets are similar to the reflective superposition eyes found in many extant decapods. As such, they are the earliest example of superposition eyes. As reflective superposition is considered plesiomorphic for Reptantia, this optic type was probably retained in Polychelida. The two smallest specimens, a Palaeopentacheles roettenbacheri (Münster, 1839) and a Hellerocaris falloti (Van Straelen, 1923), are interpreted as juveniles. Both possess square-shaped facets, a typical post-larval feature. The eye morphology of these small specimens, which are far smaller than many extant eryoneicus larvae, suggests that Jurassic polychelidans did not develop via giant eryoneicus larvae. In contrast, another species we examined, Rosenfeldia oppeli (Woodward, 1866), did not possess square-shaped facets, but rather hexagonal ones, which suggests that this species did not possess reflective superposition eyes. The hexagonal facets may indicate either another type of superposition eye (refractive or parabolic superposition), or an apposition eye. As decapod larvae possess apposition eyes with hexagonal facets, it is most parsimonious to consider eyes of R. oppeli as apposition eyes evolved through paedomorphic heterochrony. CONCLUSION: Polychelidan probably originally had reflective superposition. R. oppeli, however, probably gained apposition eyes through paedomorphosis.

The Upper Jurassic lithographic limestones of southern Germany have long been known for their exceptional preservation of decapod crustaceans (Glaessner, 1965), similar to the Upper Cretaceous of Lebanon (Hakel, Hadjoula) and the still poorly known Callovian strata at La Voulte-sur-Rhône (France). In these non-bioturbated limestones, the decay of decapod skeletons is reduced, so that besides the heavily mineralized chelae and carapace often even delicate structures such as pleopods and antennae are preserved. Recently, new decapod material has been obtained from both scientific and commercial excavations, in part in reopened lithographic limestone quarries.

The Upper Jurassic lithographic limestones of southern Germany have long been known for their exceptional preservation of decapod crustaceans (Glaessner, 1965), similar to the Upper Cretaceous of Lebanon (Hakel, Hadjoula) and the still poorly known Callovian strata at La Voulte-sur-Rhône (France). In these non-bioturbated lime stones, the decay of decapod skeletons is reduced, so that besides the heavily mineralized chelae and carapace often even delicate structures such as pleopods and antennae are preserved. Recently, new decapod material has been obtained from both scientific and commercial excavations, in part in reopened lithographic limestone quarries.

The halecomorph genus Caturus is represented in Solnhofen by the species C. furcatus and the robust form C. giganteus .The anatomy of the skull of C. pachyurus is different form C. furcatus and C. giganteus , but similar to C. bellicianus a species known from Cerin and Solnhofen, originally described as Amblysemius bellicianus . The genus Amblysemius is revived, represented in Solnhofen by the species A. pachyurus and A. bellicianus .