The middle Miocene site of Gračanica in Bosnia and Herzegovina, where limnic sediments of the former Lake Bugojno are exposed, yielded remains of a crab. The single specimen represents a freshwater ...brachyuran classified in the open nomenclature as
Potamon
sp. With an age of ~ 15 Ma, the Gračanica specimen is the oldest
Potamon
occurrence from southern Europe. An articulated female individual with preserved pereiopods suggests autochthonous or parautochthonous nature of the specimen. Presence of cuticular disks in the studied specimen confirms that these structures, previously identified in decayed crab specimens in actualistic taphonomic experiments, can be preserved in the fossil record. If found isolated, the disks may confirm the presence of decapods in studied assemblages and can be considered an additional tool for identification of otherwise rare freshwater crab fossils.
Numerous individuals of a ghost shrimp, here described as a new species, Mesostylus pervesleri, are recorded from the lower Maastrichtian Piesting Formation at Muthmannsdorf in Lower Austria. The ...accompanying molluscan fauna comprises bivalves, gastropods and cephalopods that are indicative of a low-energy, shallow-marine environment with normal salinity. The ghost shrimp body fossils are associated with two types of trace fossil; one of these is here interpreted as the remains of a callianassid burrow system, a conclusion supported by the in-situ preservation of body fossils within the burrows. Occasionally more than one individual is preserved in the same burrow structure; specimen orientation suggests that these represent moults. The presumed moults from the same burrow structure apparently do not belong to the same individual, which supports the idea that more animals shared the same burrow system at any time. Gregarious behaviour amongst representatives of the extinct genus Mesostylus is postulated on the basis of this find, and a similar one from the Upper Cretaceous of Germany. The diagnosis of the genus Mesostylus is here emended to include characters of the pleon and telson as documented not only in the new material from Muthmannsdorf but, more importantly, also in the type species, Mesostylus faujasi. The type material of Protocallianassa sarysuensis from the Coniacian of Azerbaijan is reinterpreted as representing the minor chelae of a co-occurring species, Protocallianassa caucasica; together they are here referred to as Mesostylus caucasicus, which brings the number of species belonging to the genus to four.
Decapod crustaceans from the Forcall Formation (Aptian, Lower Cretaceous) of the Oliete Sub-basin (Maestrazgo Basin) are recorded, specimens having been collected from the localities of Josa and Obón ...(Teruel) in the Aragonese branch of the Iberian Cordillera, northeast Spain. The glypheid lobster Atherfieldastacus magnus is by far the commonest species at several stratigraphical levels. Minor components of the decapod crustacean fauna include axiidean shrimps (Aptaxiopsis longimanus gen. et sp. nov., Crosniera forcallensis sp. nov., Meticonaxius gracilis sp. nov., Aptanacalliax enigma gen. et sp. nov.), a glypheidean lobster (Meyeria ornata), a hermit crab (Cretacocalcinus josaensis gen. et sp. nov.) and a brachyuran, Mithracites vectensis Gould, 1859. Meticonaxius gracilis nov. sp. represents the oldest fossil record of this genus to date. Aptanacalliax enigma gen. et sp. nov. and Crosniera forcallensis sp. nov. are considered to be the earliest occurrences of the families Anacalliacidae and Callianideidae, respectively, at this date. The specimens studied document two different modes of preservation, which also have an impact on the diversity of each assemblage. Our collections include specimens preserved within calcareous concretions and those preserved in mudstones. The assemblages studied are considered parautochthonous, i.e., were preserved within or close to their habitat and were entombed by obrution events that accumulated sediment and bioclastic material within an offshore setting.
•Decapod crustaceans from the Aptian of the Oliete Sub-basin (Spain) are described, consisting of eight species.•The assemblage includes glypheid lobsters, axiidean burrowing shrimps, a hermit crab and a brachyuran crab.•New taxa include earliest occurrences of families Anacalliacidae and Callianideidae, and Meticonaxius gen. nov. from Micheleidae.•Two modes of preservation are documented; including material within calcareous concretions, and from mudstones.
The fossil record of Isopoda includes remains of presumed parasites. Among the fossils which have been discussed as potential parasites are those termed as Urda Münster, 1840. Some of these fossils ...have been discussed as possibly related to an extant group of parasites, Gnathiidae Leach, 1814. The type species of Urda – Urda rostrata Münster, 1840 – is herein interpreted as a close relative of the group Gnathiidae, based on the shared occurrence of a number of apomorphic features. This is with Urda punctata (Münster, 1842) herein being interpreted as a junior subjective synonym of U. rostrata. However, not all of the fossils associated with the name Urda can safely be identified as close relatives of Gnathiidae. Moreover, it is unclear whether the extinct species, which can be identified as close relatives of U. rostrata and Gnathiidae form a monophyletic group, as we could not identify an autapomorphy for a natural group Urda. A new species of close relatives of Urda rostrata and Gnathiidae – Urda buechneri n. sp. – is formally described based on µCT image data. Palaega suevica Reiff, 1936 and Palaega kessleri Reiff, 1936 are found to be subjective synonyms and are re-interpreted as Urda suevica n. comb. – a species closely related to U. rostrata. Due to the documented destruction of the holotype, a herein figured fossil specimen is designated as the neotype of Urda suevica. Palaega? stemmerbergensis Malzahn, 1968 is also interpreted as a close representative of U. rostrata and herein treated as Urda stemmerbergensis n. comb. Another already formally described species – Eobooralana rhodanica gen. et comb. nov. – is interpreted as a more distant relative, which is likely to be closer related to other extant species of Isopoda than those within Gnathiidae. For three species there are not enough characters preserved to interpret them as closely related to U. rostrata and Gnathiidae: Urda? liasica Frentzen, 1937 nom. dub. (type material destroyed, description insufficient for proper diagnosis), Urda? moravica Remeš, 1912 and Urda? zelandica Buckeridge and Johns, 1996.
Despite the remarkable diversity and abundance of the modern alpheid shrimps, the fossil record of this group is sparse. However, in defiance of their relatively small size, the fingertips of the ...snapping claws of Alpheus Fabricius, 1798 have a high fossilisation potential and the preserved structures are highly characteristic. Dactylar and pollex fingertips of snapping shrimps have been recorded by several authors from numerous Cenozoic deposits, ranging from late Oligocene (Chattian, 27–28 Ma) to late Pleistocene (Tarantian, 117–126 ka); however, they have not yet been recorded in the Neotropical deposits. The present study aims to describe in detail a series of isolated snapping claw fragments referable to Alpheus from the Miocene Pirabas Formation, Pará, Brazil. In addition, we briefly discuss the palaeoenvironment, fossil preservation and bioturbation potential of alpheid shrimps. A total of 69 alpheid snapping claw fingertips were obtained from the bulk samples collected in the Atalaia and Aricuru outcrops, representing three distinct morphotypes of dactylar fingertip and at least one morphotype of pollex fingertip, indicating that at least three species of Alpheus inhabited the Cenozoic marine tropical palaeoenvironments of the Atlantic coast of South America. In fact, the presence of different fingertip morphotypes suggests that this group was already diversified in the early-middle Miocene in the Neotropical region and elsewhere. We tentatively attributed the morphotypes from the Pirabas Formation to the A. edwardsii species group, as well as to A. formosus and A. floridanus species complexes. The presence of alpheid shrimps in the Pirabas Formation deposits may be linked to the complex ichnofabric network recorded in this formation.
•Alpheid shrimps inhabited the Cenozoic marine Neotropical palaeoenvironments.•Alpheus spp. was already diversified in the Miocene in the tropical America region.•Burrowing activity of alpheid may be linked with the Pirabas Formation ichnofabric.•Snapping claws of Alpheus have a high fossilisation potential.
The enigmatic Mesoprosopon triasinum from the Triassic Hallstatt Limestone of Austria, which was once considered to be either a representative of Brachyura or Cycloidea, is re-interpreted herein as a ...eumalacostracan larva and is the oldest of its type known to date. It shows a mixture of characters that are typical of the zoea stages of certain meiuran ingroups (e.g., Hippidae) or of erichthus-type larvae of stomatopods. Four long spines evidently provided additional buoyancy to counteract the comparatively heavy load of a calcified shield. Additionally, a distinct ventral gape might imply that the animal was able to enrol into a tight ball. Our recognition of specimens of M. triasinum as larval stages, rather than adults, may have a major impact on the re-study of some still poorly known cycloids. In the future, the term “mesoprosopon” may be salvaged as the name of this type of larva.
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•Mesoprosopon triasinum from the Triassic of Austria is redescribed.•Mesoprosopon is re-interpreted to be a larval form of unidentified Eumalacostraca.•Mesoprosopon, once considered a cycloid, is considered the oldest eumalacostracan larva known to date.•More fossil Cycloidea can be re-interpreted in the future as larval forms.
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