Article

A 150-million-year-old crab larva and its implications for the early rise of brachyuran crabs

Springer Nature
Nature Communications
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Abstract

True crabs (Brachyura) are the most successful group of decapod crustaceans. This success is most likely coupled to their life history, including two specialised larval forms, zoea and megalopa. The group is comparably young, starting to diversify only about 100 million years ago (mya), with a dramatic increase in species richness beginning approximately 50 mya. Early evolution of crabs is still very incompletely known. Here, we report a fossil crab larva, 150 mya, documented with up-to-date imaging techniques. It is only the second find of any fossil crab larva, but the first complete one, the first megalopa, and the oldest one (other fossil ca. 110 mya). Despite its age, the new fossil possesses a very modern morphology, being indistinguishable from many extant crab larvae. Hence, modern morphologies must have been present significantly earlier than formerly anticipated. We briefly discuss the impact of this find on our understanding of early crab evolution.

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... True crabs (Brachyura) are the most successful group of decapod crustaceans and dominate almost all habitats, including land, freshwater, estuaries, mangroves, and marine. This success is most likely intertwined with their life history, particularly their reproductive strategies (Haug et al., 2015;Martin et al., 2016;McLay et al., 2011). Reproductive strategies are crucial to the survival of the species (Healy et al., 2019), and they play an important role during crab evolution. ...
... The paraffin-embedded 6 µm sections were cut using a microtome, deparaffinized in xylol, rehydrated in graded alcohol series, and stained with hematoxylin and eosin (HE) (Waiho et al., 2017b;Wu et al., 2020). Images of histological sections were viewed under Zeiss Axioplan 2 upright fluorescent (Haug et al., 2015) microscope (Carl Zeiss, USA). ...
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To enhance comprehension of the destiny of the spermatozoon throughout the reproductive process of mud crab (Scylla paramamosain) is important for achieving large-scale artificial breeding of Scylla. The reproductive systems of sexually mature male and female mud crabs were studied, utilizing the histomorphological method. The spermatozoon traveled from testicular lobules through the seminiferous duct, into the anterior vas deferens (AVD) via the collecting duct. The spermatophore wall formed at the end of the AVD. During copulation, spermatophores stored in the median vas deferens (MVD) were transferred to the seminal receptacle through the posterior vas deferens (PVD), ejaculatory duct, and gonopod, with seminal plasma secreted by both MVD and PVD together. After mating, the sperm plug was formed within the seminal receptacle's ventral zone. At ovary stage III, the spermatophore wall ruptured, and the sperm plug disappeared. Bundled sperm packets congregated into a dense mass, while a few spermatozoa dispersed along the intermediate chamber to the dorsal zone. At ovary stage IV, the dorsal zone also exhibited a dense sperm mass due to increased dispersal. At ovary stage V, merely a modest portion of the dense sperm mass remained in the ventral zone, and the rest dissociated and dispersed within the seminal receptacle. Following ovulation, sperm mass remained in the ventral zone, re-dissociating and re-dispersing once ovarian development reached stage III again. The phased dispersion supply mode of spermatozoa behind multiple ovipositions was unveiled. Furthermore, we observed the ultra-structural changes in the spermatozoon during the process of the capacitation, including operculum widening, actin-containing substance accumulation, and the density of chromatin in the nucleus decreased. As presented herein, the elucidation of the dynamic changes of the spermatozoon, as well as the pattern of spermatozoa supply, contributes significantly to our enhanced comprehension of the reproductive biology of Scylla.
... In all cases, light is one of the most important factors. Several light sources should be arranged around the specimen to avoid shadows, which may hide details or suggest false-positive details (e.g., [26]). To avoid reflections causing strong artefacts and for enhancing colour-contrast, cross-polarised light can be used. ...
... Due to the high flexibility of a custom setup, it can be adapted for many approaches without any manipulation of the specimen and to variable specimen sizes. This is especially important for very rare collection material, as well as fossil specimens ( [26,[29][30][31]). As in principle, not much equipment is needed (Table 1), it is relatively easy to build up transportable setups for, e.g., collection material that cannot be transported. ...
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Cells and tissues form the bewildering diversity of crustacean larval organ systems which are necessary for these organisms to autonomously survive in the plankton. For the developmental biologist, decapod crustaceans provide the fascinating opportunity to analyse how the adult organism unfolds from organ Anlagen compressed into a miniature larva in the sub-millimetre range. This publication is the second part of our survey of methods to study organogenesis in decapod crustacean larvae. In a companion paper, we have already described the techniques for culturing larvae in the laboratory and dissecting and chemically fixing their tissues for histological analyses. Here, we review various classical and more modern imaging techniques suitable for analyses of eidonomy, anatomy, and morphogenetic changes within decapod larval development, and protocols including many tips and tricks for successful research are provided. The methods cover reflected-light-based methods, autofluorescence-based imaging, scanning electron microscopy, usage of specific fluorescence markers, classical histology (paraffin, semithin and ultrathin sectioning combined with light and electron microscopy), X-ray microscopy (µCT), immunohistochemistry and usage of in vivo markers. For each method, we report our personal experience and give estimations of the method’s research possibilities, the effort needed, costs and provide an outlook for future directions of research.
... Paleontology contributes to evodevo by providing information that is only available in fossil organisms (2). Studies of evolutionary development in fossil arthropods, which have dominated faunas from the early Cambrian (∼520 million years ago) to the present, have focused on trilobites (3), "Orsten"-type fossil crustaceans (4)(5)(6), and Mesozoic malacostracan crustaceans (7). Due to their small size and low preservation potential, fossil evidence of the appendages of early developmental stages of arthropods are rare, and known mainly from those with the special "Orsten" type of preservation (8), i.e., with the cuticle secondarily phosphatized, from the mid-Cambrian (500-497 million years ago) (9). ...
... The minute larva of L. illecebrosa resembles the late-stage metanauplius of certain eucrustaceans, especially anostracans (17), other branchiopods, and cephalocarids (14), in several aspects. First, the anterior (post-SGA segments 1-4) and posterior (post-SGA segments [5][6][7][8][9][10][11][12][13][14] portions of the body differ in outline (rounded vs. narrow and elongated; Fig. 3 and Fig. S2). This is not a result of flattening: The outline of soft-bodied fossils is not subject to distortion as they collapse during decay (18) The SGA arthropods are considered either as early representatives of chelicerates (11,12,19,20) (e.g., sea spiders, horseshoe crabs, spiders, scorpions, and mites) or stem lineage representatives of all euarthropods (21) (chelicerates, myriapods, crustaceans, and insects). ...
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Significance Understanding the nature of the Cambrian radiation involves knowing not only the morphologies of adult animals but also their developmental pathways. However, fossil evidence of early larvae is rare. Here we describe a well-preserved 2-mm-long larva of the short-great-appendage arthropod Leanchoilia illecebrosa from the early Cambrian Chengjiang biota. The exceptional 3D preservation has allowed our microcomputed tomography analyses to resolve a series of rudimentary limb Anlagen in the posterior portion of the larva—an arrangement resembling that in late-stage eucrustacean metanauplii. L. illecebrosa is considered as an early representative of either chelicerates or of euarthropods as a whole. Therefore, this discovery provides fossil evidence that posthatching segment addition is a feature rooted in the ancestor of Euarthropoda.
... In fossil contexts soft tissues are rarely preserved. It is therefore not surprising that the number of fossil larvae and juveniles described for brachyurans is still small (Luque et al., 2014(Luque et al., , 2019Haug et al., 2015). Consecutively, little is known about the evolutionary changes in development of brachyurans (Haug et al., 2015). ...
... Due to a lack of suitable material in the literature, only a small number of fossils could be included into this data set. There are also no fossil megalopae included, as to date there is only one fossil crab megalopa (from the Jurassic) described (Haug et al., 2015), which is somewhat puzzling. Therefore, we cannot analyse ontogenetic changes through time yet. ...
... Klingenberg, 1998;McNamara, 1986). Certain adult forms may have already evolved and not yet possessed the highly specialised larvae known from modern forms (Haug, Audo, et al., 2015) or vice versa (Haug, Martin, & Haug, 2015). Hence, although the cube-ecospace could in principle deal better with the polymorphism, the practical application is also quite challenging. ...
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The current biodiversity crisis warrants accurate measuring of biodiversity, often achieved by counting species or higher taxonomic units, with morphological or molecular methods. Alternatively, trait‐centred approaches categorise organisms into distinct ecological roles and then count the number of occupied roles to measure biodiversity. Even combinations of trait‐based and taxonomic approaches are utilised. However, when investigating the theoretical aspects, all these approaches have significant shortcomings, which complicate a reliable biodiversity measurement, that is, the ignorance of polymorphic species, the sensitivity to the initial classification or the knowledge gap concerning the ecology of the organisms. We outline a non‐discrete ecospace approach for which neither pronounced taxonomic expertise nor in‐depth knowledge about the ecology of the organisms is required. A morphospace based on quantitative morphological properties is used as a proxy for an ecospace, thus resulting in a continuous morpho‐ecospace. With this, decision‐making concerning taxonomy or ecology is reduced, as morphology is directly used instead of being first interpreted. Differences usually not considered due to polymorphism or ontogeny can be included in this approach, as well as fossils without species determination. This morpho‐ecospace approach is easily applicable and can be combined with already existing approaches, making it broadly applicable.
... New species of decapod crustaceans are being discovered regularly (see e.g., Garassino & Schweigert 2004;Schweigert 2011;Winkler 2014;Feldmann et al. 2016;Winkler 2021). However, true crabs (brachyurans) are very rare in the Solnhofen-type lithographic limestones of Franconia (Garassino et al. 2005;Haug et al. 2015;Feldmann et al. 2016). In contrast, eleven species of brachyurans have been recorded so far from the Nusplingen Lithographic Limestones in Swabia, which are slightly older than the Solnhofen levels but formed in a similar depositional environment (Dietl & Schweigert 2011;Schweigert 2013). ...
Article
A new species of the primitive crab genus Bucculentum Schweitzer & Feldmann, 2009 is recorded from the Mörnsheim Formation (Upper Jurassic, lower Tithonian, hybonotum ammonite Zone) at Mühlheim, near Solnhofen. The new species is one of the largest members of the genus known to date. It can be distinguished from congeners in particular on the basis of carapace outline, placement of spines and shape of the branchial region and carapace grooves.
... -Trilobites: Krueger 1972Krueger , 2004-Crustaceans: Bachmayer and Mundlos 1968;Hyžný and Hudáčková 2012;Van Bakel et al. 2012;Hyžný et al. 2014a, b;Audo et al. 2014Audo et al. , 2017Haug et al. 2015;Fraaije et al. 2015Fraaije et al. , 2019Nagler et al. 2016;Haug 2016a, 2017;Charbonnier et al. 2017;Keupp and Mahlow 2017;Charbonnier and Audo 2020;Joe Collins, in Donovan and Mellish 2020;Jakobsen et al. 2020;Pazinato et al. 2020;-Insects: Kutscher 1999;Koteja 2000 (see Bechly andWichard 2008;Reich 2008a;Dlussky and Rasnitsyn 2010) ;Hoffeins 2001;Hoffeins and Hoffeins 2003;Hörnig et al. 2014;Gröhn 2015;Van Eldijk et al. 2017;Haug et al. 2018Haug et al. , 2020bFowler 2019;Kirejtshuk 2020;Makarkin and Gröhn 2020;-Sponges: Rhebergen and von Hacht 2000;Rhebergen and Botting 2014; -General faunal assemblages : Ade 1989;Shabica and Hay 1997;-Ferns: Reumer et al. 2020;-Plants in general: Robert Noll, in Lausberg et al. 2003;Uhl et al. 2004;Noll 2006, 2010;Kerp et al. 2007a, b;Knoll 2010;Rößler et al. 2012Rößler et al. , 2014Tavares et al. 2014;Neregato et al. 2015;Gröhn and Kobbert 2017;Van der Ham et al. 2017;Feng et al. 2019;Kelber 2019;-Foraminiferans: Franke 1912, 1925, 1928(see Schroeder 1991; -Ichnofossils: Donovan et al. 2019. ...
... -Trilobites: Krueger 1972Krueger , 2004-Crustaceans: Bachmayer and Mundlos 1968;Hyžný and Hudáčková 2012;Van Bakel et al. 2012;Hyžný et al. 2014a, b;Audo et al. 2014Audo et al. , 2017Haug et al. 2015;Fraaije et al. 2015Fraaije et al. , 2019Nagler et al. 2016;Haug 2016a, 2017;Charbonnier et al. 2017;Keupp and Mahlow 2017;Charbonnier and Audo 2020;Joe Collins, in Donovan and Mellish 2020;Jakobsen et al. 2020;Pazinato et al. 2020;-Insects: Kutscher 1999;Koteja 2000 (see Bechly andWichard 2008;Reich 2008a;Dlussky and Rasnitsyn 2010) ;Hoffeins 2001;Hoffeins and Hoffeins 2003;Hörnig et al. 2014;Gröhn 2015;Van Eldijk et al. 2017;Haug et al. 2018Haug et al. , 2020bFowler 2019;Kirejtshuk 2020;Makarkin and Gröhn 2020;-Sponges: Rhebergen and von Hacht 2000;Rhebergen and Botting 2014; -General faunal assemblages : Ade 1989;Shabica and Hay 1997;-Ferns: Reumer et al. 2020;-Plants in general: Robert Noll, in Lausberg et al. 2003;Uhl et al. 2004;Noll 2006, 2010;Kerp et al. 2007a, b;Knoll 2010;Rößler et al. 2012Rößler et al. , 2014Tavares et al. 2014;Neregato et al. 2015;Gröhn and Kobbert 2017;Van der Ham et al. 2017;Feng et al. 2019;Kelber 2019;-Foraminiferans: Franke 1912, 1925, 1928(see Schroeder 1991; -Ichnofossils: Donovan et al. 2019. ...
... -Trilobites: Krueger 1972Krueger , 2004-Crustaceans: Bachmayer and Mundlos 1968;Hyžný and Hudáčková 2012;Van Bakel et al. 2012;Hyžný et al. 2014a, b;Audo et al. 2014Audo et al. , 2017Haug et al. 2015;Fraaije et al. 2015Fraaije et al. , 2019Nagler et al. 2016;Haug 2016a, 2017;Charbonnier et al. 2017;Keupp and Mahlow 2017;Charbonnier and Audo 2020;Joe Collins, in Donovan and Mellish 2020;Jakobsen et al. 2020;Pazinato et al. 2020;-Insects: Kutscher 1999;Koteja 2000 (see Bechly andWichard 2008;Reich 2008a;Dlussky and Rasnitsyn 2010) ;Hoffeins 2001;Hoffeins and Hoffeins 2003;Hörnig et al. 2014;Gröhn 2015;Van Eldijk et al. 2017;Haug et al. 2018Haug et al. , 2020bFowler 2019;Kirejtshuk 2020;Makarkin and Gröhn 2020;-Sponges: Rhebergen and von Hacht 2000;Rhebergen and Botting 2014; -General faunal assemblages : Ade 1989;Shabica and Hay 1997;-Ferns: Reumer et al. 2020;-Plants in general: Robert Noll, in Lausberg et al. 2003;Uhl et al. 2004;Noll 2006, 2010;Kerp et al. 2007a, b;Knoll 2010;Rößler et al. 2012Rößler et al. , 2014Tavares et al. 2014;Neregato et al. 2015;Gröhn and Kobbert 2017;Van der Ham et al. 2017;Feng et al. 2019;Kelber 2019;-Foraminiferans: Franke 1912, 1925, 1928(see Schroeder 1991; -Ichnofossils: Donovan et al. 2019. ...
... -Trilobites: Krueger 1972Krueger , 2004-Crustaceans: Bachmayer and Mundlos 1968;Hyžný and Hudáčková 2012;Van Bakel et al. 2012;Hyžný et al. 2014a, b;Audo et al. 2014Audo et al. , 2017Haug et al. 2015;Fraaije et al. 2015Fraaije et al. , 2019Nagler et al. 2016;Haug 2016a, 2017;Charbonnier et al. 2017;Keupp and Mahlow 2017;Charbonnier and Audo 2020;Joe Collins, in Donovan and Mellish 2020;Jakobsen et al. 2020;Pazinato et al. 2020;-Insects: Kutscher 1999;Koteja 2000 (see Bechly andWichard 2008;Reich 2008a;Dlussky and Rasnitsyn 2010) ;Hoffeins 2001;Hoffeins and Hoffeins 2003;Hörnig et al. 2014;Gröhn 2015;Van Eldijk et al. 2017;Haug et al. 2018Haug et al. , 2020bFowler 2019;Kirejtshuk 2020;Makarkin and Gröhn 2020;-Sponges: Rhebergen and von Hacht 2000;Rhebergen and Botting 2014; -General faunal assemblages : Ade 1989;Shabica and Hay 1997;-Ferns: Reumer et al. 2020;-Plants in general: Robert Noll, in Lausberg et al. 2003;Uhl et al. 2004;Noll 2006, 2010;Kerp et al. 2007a, b;Knoll 2010;Rößler et al. 2012Rößler et al. , 2014Tavares et al. 2014;Neregato et al. 2015;Gröhn and Kobbert 2017;Van der Ham et al. 2017;Feng et al. 2019;Kelber 2019;-Foraminiferans: Franke 1912, 1925, 1928(see Schroeder 1991; -Ichnofossils: Donovan et al. 2019. ...
Article
Full-text available
The Society of Vertebrate Paleontology (SVP) has recently circulated a letter, dated 21st April, 2020, to more than 300 palaeontological journals, signed by the President, Vice President and a former President of the society (Rayfield et al. 2020). In this letter, significant changes to the common practices in palaeontology are requested. In our present, multi‑authored comment, we aim to demonstrate why these suggestions will not lead to improvement of both practice and ethics of palaeontological research, but conversely, will hamper its development. Despite our disagreement with the contents of the SVP letter, we appreciate the initiative and the opportunity to discuss scientific practices and the underlying ethics. Here, we consider different aspects of the suggestions of the SVP in which we see weaknesses and dangers. Our aim was to collect views from many different fields. The scientific world is, and should be, a pluralistic endeavour. This contribution deals with the aspects concerning amateur palaeontologists/citizen scientists/private collectors. Reference is made to Haug et al. (2020a) for another comment on aspects concerning Myanmar amber.First of all, we reject the notion implied by the SVP letter that studying and describing specimens from private collections represent an unethical behaviour. The question whether privately owned specimens should be considered in scientific studies is a purely scientific question (as long as the specimens were legally obtained by their owner), and thus should be answered on the basis of the scientific problems and merits of such actions.
... -Trilobites: Krueger 1972Krueger , 2004-Crustaceans: Bachmayer and Mundlos 1968;Hyžný and Hudáčková 2012;Van Bakel et al. 2012;Hyžný et al. 2014a, b;Audo et al. 2014Audo et al. , 2017Haug et al. 2015;Fraaije et al. 2015Fraaije et al. , 2019Nagler et al. 2016;Haug 2016a, 2017;Charbonnier et al. 2017;Keupp and Mahlow 2017;Charbonnier and Audo 2020;Joe Collins, in Donovan and Mellish 2020;Jakobsen et al. 2020;Pazinato et al. 2020;-Insects: Kutscher 1999;Koteja 2000 (see Bechly andWichard 2008;Reich 2008a;Dlussky and Rasnitsyn 2010) ;Hoffeins 2001;Hoffeins and Hoffeins 2003;Hörnig et al. 2014;Gröhn 2015;Van Eldijk et al. 2017;Haug et al. 2018Haug et al. , 2020bFowler 2019;Kirejtshuk 2020;Makarkin and Gröhn 2020;-Sponges: Rhebergen and von Hacht 2000;Rhebergen and Botting 2014; -General faunal assemblages : Ade 1989;Shabica and Hay 1997;-Ferns: Reumer et al. 2020;-Plants in general: Robert Noll, in Lausberg et al. 2003;Uhl et al. 2004;Noll 2006, 2010;Kerp et al. 2007a, b;Knoll 2010;Rößler et al. 2012Rößler et al. , 2014Tavares et al. 2014;Neregato et al. 2015;Gröhn and Kobbert 2017;Van der Ham et al. 2017;Feng et al. 2019;Kelber 2019;-Foraminiferans: Franke 1912, 1925, 1928(see Schroeder 1991; -Ichnofossils: Donovan et al. 2019. ...
Article
Full-text available
The Society of Vertebrate Paleontology (SVP) has recently circulated a letter, dated 21st April, 2020, to more than 300 palaeontological journals, signed by the President, Vice President and a former President of the society (Rayfield et al. 2020). In this letter, significant changes to the common practices in palaeontology are requested. In our present, multi-authored comment, we aim to demonstrate why these suggestions will not lead to improvement of both practice and ethics of palaeontological research, but conversely, will hamper its development. Despite our disagreement with the contents of the SVP letter, we appreciate the initiative and the opportunity to discuss scientific practices and the underlying ethics. Here, we consider different aspects of the suggestions of the SVP in which we see weaknesses and dangers. Our aim was to collect views from many different fields. The scientific world is, and should be, a pluralistic endeavour. This contribution deals with the aspects concerning amateur palaeontologists/citizen scientists/private collectors. Reference is made to Haug et al. (2020a) for another comment on aspects concerning Myanmar amber. First of all, we reject the notion implied by the SVP letter that studying and describing specimens from private collections represent an unethical behaviour. The question whether privately owned specimens should be considered in scientific studies is a purely scientific question (as long as the specimens were legally obtained by their owner), and thus should be answered on the basis of the scientific problems and merits of such actions.
... 4. Fossil larvae may provide minimum ages for specific larval types known from the modern fauna (Maisey & De Carvalho, 1995;Kadej & Háva, 2011;Waloszek & Dunlop, 2002;Briggs et al., 2005;Pohl, 2009;Wang & Zhang, 2010;Zhang et al., 2010;Makarkin, Wedmann & Weiterschan, 2012;Haug, Wiethase & Haug, 2015;Haug, Martin & Haug, 2015;Serrano-Sánchez et al., 2016;Néraudeau et al., 2017;Haug, Müller & Haug, 2018;Pérez-De La Fuente et al., 2018). This may well also represent a case of the oldest representative of a lineage, i.e. provide a taxonomic or phylogenetic signal as well. ...
Article
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Larvae, and especially fossil larvae, are challenging to deal with from a purely taxonomic view. Often one cannot determine which species the larvae belong to. Yet, larvae can still contribute to various scientific questions. Especially morphological traits of a fossil larva can be highly informative for reconstructing character evolution. Also the occurrence of specific larval types and larval characters in time and the disappearance of such forms can well be reconstructed also without being able to narrow down the phylogenetic relationship of a larva very far. Here, we report two new beetle larvae preserved in Baltic amber which are identified as representatives of Scraptiidae, based on an enlarged terminal end (‘9th abdomen segment’); this is only the third record of such larvae. In comparison to modern forms, the terminal ends of the two new fossil larvae is even larger in relation to the remaining body than in any known larva. Unfortunately, our knowledge of such larvae in the modern fauna is very limited. Still, one of the two already known fossil larvae of Scraptiidae also has a very long terminal end, but not as long as those of the two new fossils. These three fossil larvae therefore seem to possess a specific morphology not known from the modern fauna. This might either mean that they (1) represent a now extinct larval morphology, a phenomenon well known in other euarthropodan lineages, or that (2) these forms represent a part of the larval phase not known from modern day species as they have not been described yet; such cases occur in closely related lineages. In any case, the fossils expand the known diversity of larval morphologies.
... Yet, for many other types of preservation especially the large forms appear to have a higher chance to be preserved. For malacostracan crustaceans, we have fossils of especially supersized larvae such as those of achelatan lobsters (Polz, 1971;1972;Haug et al., 2011a;, polychelidan lobsters (Haug et al., 2015a; or mantis shrimps (Haug et al., 2008(Haug et al., , 2015b, some of them in thousands of specimens (Polz, 1987;1996), while smaller-sized larvae like those of crabs are very rare (Haug et al., 2015c). It seems therefore common that giant larvae occur as fossils. ...
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The larval phase of metazoans can be interpreted as a discrete post-embryonic period. Larvae have been usually considered to be small, yet some metazoans possess unusually large larvae, or giant larvae. Here, we report a possible case of such a giant larva from the Upper Jurassic Solnhofen Lithographic limestones (150 million years old, southern Germany), most likely representing an immature cirripede crustacean (barnacles and their relatives). The single specimen was documented with up-to-date imaging methods (macro-photography, stereo-photography, fluorescence photography, composite imaging) and compared with modern cirripede larvae. The identification is based on two conspicuous spine-like extensions in the anterior region of the specimen strongly resembling the so-called fronto-lateral horns, structures exclusively known from cirripede nauplius larvae. Notably, at 5 mm in length the specimen is unusually large for a cirripede nauplius. We therefore consider it to be a giant larva and discuss possible ecological and physiological mechanisms leading to the appearance of giant larvae in other lineages. Further findings of fossil larvae and especially nauplii might give new insights into larval evolution and plankton composition in the past.
... However, fossil malacostracan larvae have received much attention during the last decade (Haug et al., 2011. Virtually all the material has been recorded from Lagerstätten with exceptional preservation, including platy limestones from the Jurassic of southern Germany (e.g., the famous Solnhofen Lithographic Limestones), and the Cretaceous of Brazil (Santana/Crato) and Lebanon (Hadjoula/Hakel): 1) Most of the extinct malacostracan larvae have been recorded from the Upper Jurassic Solnhofen Limestones with representatives of Stomatopoda (Haug et al., 2008(Haug et al., , 2009a(Haug et al., , 2009b(Haug et al., , 2010(Haug et al., , 2011(Haug et al., , 2015a and Decapoda, more precisely Polychelida , Achelata (Polz, 1972(Polz, , 1973(Polz, , 1984(Polz, , 1987(Polz, , 1995(Polz, , 1996Haug et al., 2009c and Brachyura (Haug et al., 2015b). ...
Article
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 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 future, the term 'mesoprosopon' may be salvaged as the name of this type of larva.
... Conversely, modern deeper water pelagic crustaceans appear to have smaller eyes resulting in a lower energetic burden, a lower weight, less drag, and eyes being less visible to predators [114,115], a result not studied in fossil decapods thus far. This study shows that fossil decapod crustaceans can be used to study vision and ecology, which has rarely been documented thus far [116,117] given the rare occurrence of fossil decapod eyes with the exception of specimens from Konservat-Lagerstätten [118][119][120][121][122][123][124][125][126]. ...
Article
Background Modern cold-water coral and tropical coral environments harbor a highly diverse and ecologically important macrofauna of crustaceans that face elevated extinction risks due to reef decline. The effect of environmental conditions acting on decapod crustaceans comparing these two habitats is poorly understood today and in deep time. Here, we compare the biodiversity, eye socket height as a proxy for eye size, and body size of decapods in fossil cold-water and tropical reefs that formed prior to human disturbance. Results We show that decapod biodiversity is higher in fossil tropical reefs from The Netherlands, Italy, and Spain compared to that of the exceptionally well-preserved Paleocene (Danian) cold-water reef/mound ecosystem from Faxe (Denmark), where decapod diversity is highest in a more heterogeneous, mixed bryozoan-coral habitat instead of in coral and bryozoan-dominated facies. The relatively low diversity at Faxe was not influenced substantially by the preceding Cretaceous/Paleogene extinction event that is not apparent in the standing diversity of decapods in our analyses, or by sampling, preservation, and/or a latitudinal diversity gradient. Instead, the lower availability of food and fewer hiding places for decapods may explain this low diversity. Furthermore, decapods from Faxe are larger than those from tropical waters for half of the comparisons, which may be caused by a lower number of predators, the delayed maturity, and the increased life span of crustaceans in deeper, colder waters. Finally, deep-water specimens of the benthic crab Caloxanthus from Faxe exhibit a larger eye socket size compared to congeneric specimens from tropical reefs, suggesting that dim light conditions favored the evolution of relatively large eyes. Conclusions The results suggest a strong habitat control on the biodiversity of crustaceans in coral-associated environments and that the diversity difference between deep, cold-water reefs and tropical reefs evolved at least ~63 million years ago. Futhermore, body size and vision in crustaceans evolved in response to environmental conditions in the deep sea. We highlight the usefulness of ancient reefs to study organismal evolution and ecology. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0694-0) contains supplementary material, which is available to authorized users.
... Conversely, modern deeper water pelagic crustaceans appear to have smaller eyes resulting in a lower energetic burden, a lower weight, less drag, and eyes being less visible to predators [114,115], a result not studied in fossil decapods thus far. This study shows that fossil decapod crustaceans can be used to study vision and ecology, which has rarely been documented thus far [116,117] given the rare occurrence of fossil decapod eyes with the exception of specimens from Konservat-Lagerstätten [118][119][120][121][122][123][124][125][126]. ...
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ABSTRACT All Jurassic brachyuran taxa known to date are based solely upon dorsal carapaces, and only a limited number of Early and mid-Cretaceous crabs retain ventral parts. Therefore, all Jurassic taxa and many forms from the first half of the Cretaceous are carapace-based entities. All of them are considered to be “dromiaceans”, podotremes to be precise. The recent discovery of an exceptionally well-preserved male crab from the Upper Cretaceous (lower Cenomanian) of Chiapas (Mexico), Archaeochiapasa mardoqueoi Guinot, Carbot-Chanona & Vega, 2019, at first sight of a podotreme nature, has allowed a detailed de¬scription of its thoracic sternum and pleon, which revealed that it was actually a typical eubrachyuran, in need of a new family, Archaeochiapasidae Guinot, Carbot-Chanona & Vega, 2019. This has brought back to life one of my earlier ideas about the possible non-podotreme nature of certain enigmatic Late Jurassic and Cretaceous Brachyura previously placed in various “dromiacean” (i.e., podotreme) families and superfamilies. My investigations have led the me to formulate the present hypothesis that the extinct families Bucculentidae Schweitzer & Feldmann, 2009 (currently assigned to the Homolodromioidea Al¬cock, 1900), Lecythocaridae Schweitzer & Feldmann, 2009, Glaessneropsidae Schweitzer & Feldmann, 2009, Nodoprosopidae Schweitzer & Feldmann, 2009, and Viaiidae Artal, Van Bakel, Fraaije, Jagt & Klompmaker, 2012 (all four in Glaessneropsoidea Schweitzer & Feldmann, 2009) might, in fact (at least for some of them), be true eubrachyurans (Eubrachyura Saint Laurent, 1980). If correct, these assump¬tions would date the first “true crabs” as Jurassic, contrary to the currently held view that the earliest Eu¬brachyura (heterotremes) did not appear until the Cretaceous, and suggest that the evolutionary history of brachyurans started much earlier. This was unpredictable, at least for palaeontologists, but not so in view of a molecular estimate of decapod phylogeny that recovered the Majoidea Samouelle, 1819 as the oldest brachyuran lineage, with a divergence from other brachyurans from, at least, the Middle Triassic. The basal majoid family Oregoniidae Garth, 1958, which comprises only three extant genera, has several characters in common with Archaeochiapasidae; these leave little doubt about their close relationships. Proposals made here are inevitably based on provisional assumptions, until the characteristics of the ven¬tral parts and pereiopods prove or refute them, either entirely or in part. Our science, which is based on the observation of specimens and then on descriptive, explanatory and, above all, predictive concepts, especially where incomplete fossil animals are concerned, should be conceived as a step forward, rather than an achievement, each of these steps being, sooner or later, replaced by a better one, or considered to be such. That is why all species and the composition of the Jurassic and Early Cretaceous genera and families will need to be checked in light of new perspectives. In contrast to the presumed eubrachyurans (see above), the Tanidromitidae Schweitzer & Feldmann, 2008 and the apparently paraphyletic family Longodromitidae Schweitzer & Feldmann, 2009 are podotremes, within the Dynomeniformia Guinot, Tavares & Castro, 2013. The status and composition of the Goniodromitinae Beurlen, 1932 (in the Dromiidae De Haan, 1833), clearly paraphyletic, are briefly revised, while some genera, such as Distefa¬nia Checchia-Rispoli, 1917, are tentatively assigned to the Sphaerodromiinae Guinot & Tavares, 2003. A table summarises the changes in classification implied by these new proposals and research directions. Some remarks on the new section Callichimaeroida Luque, Feldmann, Vernygora, Schweitzer, Cameron, Kerr, Vega, Duque, Strange, Palmer & Jaramillo, 2019 are provided, as well as on the the putatively callichimaeroid-like family Retrorsichelidae Feldmann, Tshudy & Thomson, 1993.
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All Jurassic brachyuran taxa known to date are based solely upon dorsal carapaces, and only a limited number of Early and mid-Cretaceous crabs retain ventral parts. Therefore, all Jurassic taxa and many forms from the first half of the Cretaceous are carapace-based entities. All of them are considered to be “dromiaceans”, podotremes to be precise. The recent discovery of an exceptionally well-preserved male crab from the Upper Cretaceous (lower Cenomanian) of Chiapas (Mexico), Archaeochiapasa mardoqueoiGuinot, Carbot-Chanona & Vega, 2019, at first sight of a podotreme nature, has allowed a detailed description of its thoracic sternum and pleon, which revealed that it was actually a typical eubrachyuran, in need of a new family, Archaeochiapasidae Guinot, Carbot-Chanona & Vega, 2019. This has brought back to life one of my earlier ideas about the possible non-podotreme nature of certain enigmatic Late Jurassic and Cretaceous Brachyura previously placed in various “dromiacean” (i.e., podotreme) families and superfamilies. My investigations have led the me to formulate the present hypothesis that the extinct families Bucculentidae Schweitzer & Feldmann, 2009 (currently assigned to the Homolodromioidea Alcock, 1900), Lecythocaridae Schweitzer & Feldmann, 2009, Glaessneropsidae Schweitzer & Feldmann, 2009, Nodoprosopidae Schweitzer & Feldmann, 2009, and Viaiidae Artal, Van Bakel, Fraaije, Jagt & Klompmaker, 2012 (all four in Glaessneropsoidea Schweitzer & Feldmann, 2009) might, in fact (at least for some of them), be true eubrachyurans (Eubrachyura Saint Laurent, 1980). If correct, these assumptions would date the first “true crabs” as Jurassic, contrary to the currently held view that the earliest Eubrachyura (heterotremes) did not appear until the Cretaceous, and suggest that the evolutionary history of brachyurans started much earlier. This was unpredictable, at least for palaeontologists, but not so in view of a molecular estimate of decapod phylogeny that recovered the Majoidea Samouelle, 1819 as the oldest brachyuran lineage, with a divergence from other brachyurans from, at least, the Middle Triassic. The basal majoid family Oregoniidae Garth, 1958, which comprises only three extant genera, has several characters in common with Archaeochiapasidae; these leave little doubt about their close relationships. Proposals made here are inevitably based on provisional assumptions, until the characteristics of the ventral parts and pereiopods prove or refute them, either entirely or in part. Our science, which is based on the observation of specimens and then on descriptive, explanatory and, above all, predictive concepts, especially where incomplete fossil animals are concerned, should be conceived as a step forward, rather than an achievement, each of these steps being, sooner or later, replaced by a better one, or considered to be such. That is why all species and the composition of the Jurassic and Early Cretaceous genera and families will need to be checked in light of new perspectives. In contrast to the presumed eubrachyurans (see above), the Tanidromitidae Schweitzer & Feldmann, 2008 and the apparently paraphyletic family Longodromitidae Schweitzer & Feldmann, 2009 are podotremes, within the Dynomeniformia Guinot, Tavares & Castro, 2013. The status and composition of the Goniodromitinae Beurlen, 1932 (in the Dromiidae De Haan, 1833), clearly paraphyletic, are briefly revised, while some genera, such as DistefaniaChecchia-Rispoli, 1917, are tentatively assigned to the Sphaerodromiinae Guinot & Tavares, 2003. A table summarises the changes in classification implied by these new proposals and research directions. Some remarks on the new section Callichimaeroida Luque, Feldmann, Vernygora, Schweitzer, Cameron, Kerr, Vega, Duque, Strange, Palmer & Jaramillo, 2019 are provided, as well as on the the putatively callichimaeroid-like family Retrorsichelidae Feldmann, Tshudy & Thomson, 1993.
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Plankton are aquatic organisms unable to swim against the current, and they include diverse taxa of different phylogenetic origins. The taxonomy, phylogeny and ecology of nine plankton groups are reviewed in this paper, in order to comprehensively understand the latest information and current situation of plankton studies. The order-level classification of dinoflagellates was re-arranged, but the classification system is still not well organized at the family-level. The taxonomy of raphidophytes and dictyochophytes was partly confused, however, molecular studies provided clear categorization between these groups. The diatoms could be identified by observing some important morphological characteristics. Yet, these characteristics are sometimes not observable because of inappropriate specimen treatments, and furthermore, the morphological terms are not enough unified, resulting that the species-level identification is complicated and difficult. Recent studies revealed the cryptic diversity and high abundance of some microalgae, such as haptophytes and prasinophytes. The diversity and ecology of planktonic foraminifers have been clarified, but those of radiolarians and phaeodarians are still wrapped in mystery. The classification needs to be re-arranged especially for collodarians, phaeodarians and acantharians. The phylogeny of copepods has been elucidated, and this group was re-classified into 10 orders. Future studies should clarify their evolutionary process and create useful databases for easier identification. The methods to reveal the larva-adult correspondence are established for decapods, and further clarification of the correspondence is expected. The classification system of chaetognaths has been updated, and the intra-species diversity is also being studied. The species diversity of scyphozoans has not been well clarified especially for deep-sea species, and their classification still involves problems such as cryptic species. The dataset including DNA sequences and different types of images(taken in the field and under the microscope, etc.)should be accumulated for comparing the data from different methods (e.g., direct microscopy, optics-based survey and environmental DNA analysis).
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Full text available at: https://advances.sciencemag.org/content/5/4/eaav3875/tab-pdf. Evolutionary origins of novel forms are often obscure because early and transitional fossils tend to be rare, poorly preserved, or lack proper phylogenetic contexts. We describe a new, exceptionally preserved enigmatic crab from the mid-Cretaceous of Colombia and the United States, whose completeness illuminates the early disparity of the group and the origins of novel forms. Its large and unprotected compound eyes, small fusiform body, and leg-like mouthparts suggest larval trait retention into adulthood via heterochronic development (pedomorphosis), while its large oar-like legs represent the earliest known adaptations in crabs for active swimming. Our phylogenetic analyses, including representatives of all major lineages of fossil and extant crabs, challenge conventional views of their evolution by revealing multiple convergent losses of a typical “crab-like” body plan since the Early SCretaceous.These parallel morphological transformations may be associated with repeated invasions of novel environments, including the pelagic/necto-benthic zone in this pedomorphic chimera crab.
Chapter
Paleo-evo-devo is the discipline studying the developmental biology of fossil organisms and its evolutionary implications. In adopting a paleo-evo-devo approach, fossils have to be understood as once-living organisms, and the developmental patterns of extant organisms have to be comparatively investigated. For some types of fossils, it is comparably easy to investigate ontogeny, as they preserve earlier portions of the process throughout their entire life, for example as growth lines, or as they have been fossilized while bearing offspring inside their bodies. Yet, in most cases the ontogeny of fossil organisms (and also of some extant ones) has to be reconstructed based on plausibility. Major aspects for this approach are increasing differentiation or number of structures as well as continuity in development. Despite the difficulties in reconstructing the ontogenies of fossil organisms, studying fossilized development can provide important insights into the evolution of developmental patterns not available only from the study of extant organisms. Also the workflow in the practical work in paleo-evo-devo is shortly outlined.
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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 lobster Nephrops 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.
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We present new data on two species of stomatopods from the Upper Jurassic Solnhofen Lithographic Limestones of southern Germany. One is a new species, Gigantosculda ehrlichfeckei n. gen. n. sp. It is known from two specimens, probably representing two larval stages. The species is characterised by a larval morphology with a long rostrum, long postero-lateral spines on the head shield, uropods with basipodal spines about twice as long as the telson, and a comparably large size. The second species is the already known species Spinosculda ehrlichi. Here newly observed features of the late larval stages include the mandibles and the maxillipeds 2–5. The comparison of the two species described in this study reveals possible plesiomorphic larval characters in Stomatopoda: 1) a head shield protruding over the thorax, and 2) lanceolate uropodal exopods without moveable spines. It also reveals possible synapomorphies of Gigantosculda n. gen. and Verunipeltata (the group including all modern representatives): 1) comparably large size of later larval stages, and 2) presence of an elongate rostrum and postero-lateral spines on the head shield in the larvae. The descriptions add information to the diversity and ecology of Mesozoic mantis shrimps, as well as to the evolution of stomatopods.
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Recognition of remains of sterna, pleons, and pereiopods of Aulavescus paintenensis n. sp. (Munidopsidae) and Goniodromites serratus BEURLEN, 1929, from the Late Jurassic Solnhofentype lagerstätten in Bavaria, Germany, provides the first description of these structures in Jurassic Munidopsidae and Goniodromitidae. Addition of these morphological characters to Goniodromitidae and cladistic analysis secured the position of the family within Homolodromioidea and Dromiacea. © 2016 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
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Construction excavation within member "B" of the middle Eocene-aged Santiago Formation at Bressi Ranch in the southern part of the City of Carlsbad, California, USA, have produced exceptionally preserved upogebiid fossils. While most fossil upogebiids are only known fragmentarily, the specimens described here are preserved as relatively complete articulated specimens. Preserved structures include: the cephalothoracic shield with a short rostrum, a well-developed cervical groove and anterior coarse tuberculation; the pleon, with a characteristic trapezoidal first tergite and the second tergite representing the largest of the series; the appendages including (fragmentary) maxillipeds two and three, and the five walking limbs; the tail fan with uropods with both sub-triangular rami possessing bulging anterior edges and one (endopod) or two (exopod) keels running in parallel to the anterior bulging edge, the exopod lacking a diaresis, and the telson being sub-rectangular with a median suture. Exceptional minute details preserved are the bases of setae on the uropods and muscles in pleomere six. These muscles show fiber bundles about 80 μm in diameter, and individual fibers about 10 μm in diameter. The specimens were documented with up-to-date imaging techniques, including stereo photography or depth-map-based surface reconstructions. Due to the exceptional preservation, the fossils can be recognized as an upogebiid of the species Upogebia aronae sp. nov. As numerous specimens have been found at that locality, this discovery indicates similarly dense populations as seen in modern fauna.
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Despite the extensive fossil record of higher crabs (Eubrachyura) from Late Cretaceous and Cenozoic rocks worldwide, their Early Cretaceous occurrences are scarce and fragmentary, obscuring our understanding of their early evolution. Until now, representatives of only two families of eubrachyuran-like crabs were known from the Early Cretaceous: Componocancridae and Tepexicarcinidae fam. nov., both monospecific lineages from the Albian (~110–100 Ma) of North and Central America, respectively. The discovery of Telamonocarcinus antiquus sp. nov. (Telamonocarcinidae) from the early Albian of Colombia, South America (~110 Ma), increases to three the number of known Early Cretaceous eubrachyuran-like families. The ages and geographical distributions of the oldest eubrachyuran-like taxa (i.e. Componocancridae, Telamonocarcinidae and Tepexicarcinidae fam. nov.) suggest that the oldest higher true crabs might have originated in the Americas; that they were already morphologically diverse by the late Early Cretaceous; and that their most recent common ancestor must be rooted in the Early Cretaceous, or even the Late Jurassic.
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Larvae represent a specific life phase of an organism and often have very different life habits and morphology than adults. Like in adults, larval traits also most likely evolved gradually. We describe a new larval form, recently discovered in the about 95 million years old Plattenkalks of Hadjoula (Lebanon, Cenomanian, Late Cretaceous). The two known specimens possess larval characteristics and can be ascribed to polychelidan lobsters. They represent the youngest non-ambiguous polychelidan in the fossil record and the single known occurrence of a fossil larval form of a polychelidan lobster. Like their modern counterparts, eryoneicus larvae of Polychelidae, these fossil larvae are relatively large and armed with numerous spines on their shield (carapace) and pleon. They differ from extant eryoneicus larvae by their unusually long rostrum, their stalked eyes with a developed cornea and a shield far less inflated than the balloon-like shield of modern eryoneicus larvae. These fossil larvae demonstrate that the highly specialised morphology of modern polychelid larvae evolved gradually and give important clues in which temporal order these larval specialisations evolved. The specimens are another example of fossils providing crucial insights into the evolution of specialised developmental patterns of modern groups, as previously demonstrated for mantis shrimps, achelate lobsters, or early crustaceans, but also for other animal groups.
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The evolutionary origin of frog crabs (Raninoida) remains puzzling partly due to their astonishing morphological disparity, ranging from broad and heavily ornamented ‘crab-like’ extinct families (necrocarcinids and allies), to elongate and smoother ‘frog-like’ extant ones (raninids and allies). However, an ancient Cretaceous clade (Palaeocorystidae) displays a combination of plesiomorphic and apomorphic traits that might advocate for either evolutionary scenario: from ‘crab-like’ to ‘frog-like’, or vice versa. This lack of agreement is partly fuelled by the scarcity of Early Cretaceous fossils, a time from which the first raninoidans are known. A close re-examination of an Early Cretaceous fossil from the Santana Group of Brazil, Araripecarcinus ferreirai Martins-Neto, 1987, combined with phylogenetic analysis including all main clades of podotreme crabs, reinforces its raninoidan condition, and rejects the initial hypothesis of a Portunoidea affinity. Furthermore, comparisons with other raninoidans support the hypothesis that a more ‘crab-like’ body plan is the plesiomorphic condition for raninoidans, and that the ‘frog-like’ architecture of Palaeocorystidae, and perhaps the Raninoidea as a whole, reflects a derived condition related to a specialized burrowing lifestyle. Phylogenetic analyses are fundamental to evaluate the position of Palaeocorystidae with respect to raninoidean and necrocarcinid-like families, helping to better resolve the Raninoida evolutionary tree of life, and to gain a broader understanding on their relatedness by common ancestry throughout geological time.
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Modern achelate lobsters, slipper and spiny lobsters, have a specific post-embryonic developmental pattern with the following phases: phyllosoma, nisto (slipper lobsters) or puerulus (spiny lobsters), juvenile and adult. The phyllosoma is a peculiar larva, which transforms through a metamorphic moult into another larval form, the nisto or puerulus which largely resembles the juvenile. Unlike the nisto and puerulus, the phyllosoma is characterised by numerous morphological differences to the adult, e.g. a thin head shield, elongate appendages, exopods on these appendages and a special claw. Our reinvestigation of the 85 million years old fossil "Eryoneicus sahelalmae" demonstrates that it represents an unusual type of achelatan lobster larva, characterised by a mixture of phyllosoma and post-phyllosoma characters. We ascribe it to its own genus: Polzicaris nov. gen. We study its significance by comparisons with other cases of Mesozoic fossil larvae also characterised by a mixture of characters. Accordingly, all these larvae are interpreted as ontogenetic intermediates between phyllosoma and post-phyllosoma morphology. Remarkably, most of the larvae show a unique mixture of retained larval and already developed post-larval features. Considering the different-and incompatible-mixture of characters of each of these larvae and their wide geographical and temporal distribution, we interpret all these larvae as belonging to distinct species. The particular character combinations in the different larvae make it currently difficult to reconstruct an evolutionary scenario with a stepwise character acquisition. Yet, it can be concluded that a larger diversity of larval forms and developmental patterns occurred in Mesozoic than in modern faunas.
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We describe new specimens of Mesozoic mantis shrimps (Stomatopoda, Malacostraca) that exhibit morphological and developmental information previously unknown. Specimens assigned to the taxon Sculda exhibit preserved pleopods, thoracopods including all four raptorial limbs as well as details of antennae and antennulae. The pleopods and the antennulae resemble those of the modern mantis shrimps, but the raptorial limbs are not as differentiated as in the modern species. In some specimens, the first raptorial limb (second thoracopod) is not significantly larger than the similar-sized posterior three pairs (as in extant species), but instead these appendages become progressively smaller along the series. In this respect they resemble certain Palaeozoic stomatopods. Another specimen, most likely belonging to another species, has one pair of large anterior raptorial thoracopods, a median-sized pair and two more pairs of small-sized raptorial appendages and, thus, shows a new, previously unknown type of morphology. A single specimen of Pseudosculda laevis also exhibits the size of the raptorial limbs; they are differentiated as in modern species, one large pair and three small pairs. Furthermore, we report additional larval specimens and show also post-larval changes, e.g., of the tail fan. These new data are used to reconsider the phylogeny of Stomatopoda. We still need a strict taxonomical revision of the Mesozoic mantis shrimps, but this first examination already demonstrates the importance of these fossils for understanding mantis shrimp evolution and the interpretation of evolutionary pathways of particular features.
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The complete larval development of Liocarcinus corrugatus is described, based on laboratory-reared material. The species has 5, or occasionally 6, zoeal stages and a megalopal stage. Morphological characters of larvae of L. corrugatus were compared with this and other species of Liocarcinus reported from other regions.
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In this article, I map the currently known brachyuran fossil record on a recent cladograrn of Brachyura, the true crabs. The hypothesis of brachyuran phylogenetic relationships is based on a cladistic analysis of brachyuran foregut characters. With this approach, the following scenario of the evolution of Brachyura is proposed. The representatives of Brachyura that occur earliest in the fossil record (Dromioidea) take the most basal position in the cladogram, followed by Homolidae. These taxa reach their highest species diversity during the Cretaceous, together with Raninidae and Cymonomidae sensu lato. The analysis reveals that the majority of the "higher" crabs (Xanthoidea, Portunidae, Cancridae, and Oxystomata sensu lato) as well as their common ancestor existed already by the end of the Cretaceous. In particular, a constant increase of brachyuran species diversity has been registered from the Eocene to the Miocene. Most taxa of the Brachyura (with the exception of the Carcineretidae) remained unaffected by the events at the Cretaceous-Tertiary-boundary. Hence, the data suggest the events at the K/T-boundary have had a weaker influence on the species diversity of the Brachyura and of the Decapoda in general, than originally presumed: i.e., there was no mass-extinction of crabs.
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The available information on the megalopa stage in podotrematous crabs, that is the Dromioidea, Homoloidea, Raninoidea and Tymoloidea, is reviewed. The morphology of the megalopas tends to support the relationships between these groups indicated by the zoeal stages but does not provide any additional evidence on the unresolved problem of whether or not the dromioids should be considered to be true crabs.
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Eocarcinus praecursor, the putative earliest member of Infraorder Brachyura of Early Jurassic age in Great Britain, cannot be accommodated within that infraorder. Numerous characters are inconsistent with placement within Brachyura, including: a lack of fusion of the epistome with the dorsal carapace; chelipeds on the first and putatively second pereiopods; lack of true orbits; development of large, strong antennae; notches in the carapace to accommodate the antennae; articulating rings on the pleomeres; development of prominent epimeres; and orientation of the chelipeds. Rather, E. praecursor must be referred to its own superfamily and family within Infraorder Anomura.
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Lobopodians, a nonmonophyletic assemblage of worm-shaped soft-bodied animals most closely related to arthropods, show two major morphotypes: long-legged and short-legged forms. The morphotype with stubby, conical legs has a long evolutionary history, from the early Cambrian [1] through the Carboniferous [2, 3], including the living onychophorans and tardigrades [4-6]. Species with tubular lobopods exceeding the body diameter have been reported exclusively from the Cambrian [7-12]; the three-dimensionally preserved Orstenotubulus evamuellerae from the uppermost middle Cambrian "Orsten" (Sweden) is the youngest long-legged lobopodian reported thus far [8]. Here we describe a new long-legged lobopodian, Carbotubulus waloszeki gen. et sp. nov., from Mazon Creek, Illinois, USA (∼296 million years ago) [13]. This first post-Cambrian long-legged lobopodian extends the range of this morphotype by about 200 million years. The three-dimensionally preserved specimen differs significantly from the associated short-legged form Ilyodes inopinata [2], of which we also present new head details. The discovery of a Carboniferous long-legged lobopodian provides a more striking example of the long-term survival of Cambrian morphotypes than, for example, the occurrence of a Burgess Shale-type biota in the Ordovician of Morocco [14] and dampens the effect of any major extinction of taxa at the end of the middle Cambrian [15, 16].
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Knowledge of early, Mesozoic crabs is still rudimentary, mainly due to the poor preservational potential of crustacean decapods. Fossil evidence suggests that the family Prosopidae is ancestral to all other brachyurans, including Podotremata, with a very close phylogenetic relationship to Homolodromiidae, Dromiidae, Homolidae, Latreillidae, Dynomenidae, Xanthidae, Cyclodorippoidea and Calappoidea. Prosopidae is an extinct family, consisting mostly of Mesozoic species, almost exclusively known by their carapaces. This family appeared in the late Early Jurassic (Late Pliensbachian) and disappeared at the end of the Danian. The Early Jurassic (Pliensbachian) oldest crab species, Eocarcinus praecursor Withers, is transitional in many of its observable traits between the macruran Glypheoidea (Middle Triassic Pseudopemphix) and the early brachyuran prosopids, especially the earliest known species, Eoprosopon klugi Förster (Late Pliensbachian). Middle Jurassic prosopids lived in shallow-sea, soft bottom environments. The oldest known prosopid species lived on a silty sea floor, as did the first known crab (late Early Pliensbachian), and their presumed ancestors (Pemphicidae) were probably also shallow water organisms. Middle Jurassic prosopids lived both in shallow warm waters within organic buildups/shelly accumulations, and on silty sea-floors during the Bajocian/Bathonian, as illustrated by a new example from central Poland. Prosopids had an evolutionary climax during the Late Jurassic and were widely distributed in sponge-microbial (Oxfordian) buildups and coral reef (Kimmeridgian–Tithonian) environments of Europe (Pithonoton, Coelopus, Longodromites, Prosopon, Nodoprosopon, Lecythocaris, Glaessneropsis). When biohermal and reef facies retreated at the end of the Jurassic, favourable conditions for prosopid crabs diminished and Cretaceous prosopids are rare and spatially dispersed. Their closely related descendants, the homolodromiids, preferentially inhabited soft muddy bottoms in deeper, colder waters, as is well documented by Cenozoic and Recent occurrences.
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We present different documentation methods tested on fossil specimens from Solnhofen-type lithographic limestones (Upper Jurassic, southern Germany) and from the related deposits from the Upper Cretaceous of Lebanon. One of the principles is composite imaging. This combines image fusion, i.e., coalescing several images of the same area but at different focal planes, resulting in a single image of high depth of field, and image stitching, i.e., combining fused images of several areas to a high reso-lution image of the complete specimen. The basis for the composite images can be normal light images, but most fossils from Solnhofen-type lithographic limestones are autofluorescent under UV light such that UV-fluorescence images can be equally well applied. In this context, we report a new fluorescence type for specimens not showing good UV fluorescence, i.e., those from the Zandt lagerstätte or some from Lebanon. These specimens fluoresce orange when exposed to green light. Specimens from Leb-anon exhibiting green-orange fluorescence have been documented under a confocal laser scanning microscope (cLSM). Fossils showing a relatively high relief can be doc-umented with stereo images; based on these surfaces, 3D models can be produced. A large specimen preserved uncompressed has been documented using a medical X-ray computer tomography scanner. All these methods facilitate the high-resolution docu-mentation of complete specimens (= "virtual specimens"). Specimens from both Soln-hofen-type lithographic limestones and Lebanon have further been examined for their elemental composition using energy dispersive X-ray spectroscopy (EDX). The fossils differ significantly from the surrounding matrix by containing 6–14% phosphorus.
Article
The Solnhofen Limestones represent one of the most important sources for crustacean diversity in the Jurassic and even for their fossil record in the Mesozoic. A brief overview of the history of science since the beginning of 18th century and the circumstances of the fossil recoveries are provided. The fossils come from various localities of slightly different ages (late Kimmeridgian -early Tithonian). Most specimens did not live at their later places of burial, but were swept in as exuviae from more or less distant neighboring environments. These reasons are responsible for the great diversity of genera and species described so far. Three species of caridean shrimps from the Solnhofen Limestones of Eichstiitt and Zandt are newly introduced: Hefriga rogerfrattigianii, He-friga norhertwinkleri, and Harthofia polzi.
Article
A b s t r a c t We report the first undisputable fossil larval stomatopod, as previous records all refer to thylacocephalans. The single specimen has been found in the Upper Jurassic Solnhofen Lithographic Limestones (Bavaria). We docu-mented the specimen using a UV-light microscope, taking over 700 single images. These were summed up to a large compound image adding images in z-axis and in x-y plane. The result is a very high resolution image of high depth of field showing delicate details. The specimen possesses a tri-flagellate antennula and sub-chelate raptorial ap-pendages, identifying it as a stomatopod. Larval characters are a large immobile rostrum and a shield hiding all thoracomeres. The specimen is probably a Sculda sp. and possibly not a S. pennata, but based on the existing data it cannot be verified whether it represents a new species. Key word s: Stomatopoda, fossil larvae, Solnhofen Lithographic Limestones, UV-microscopy. Z u s a m m e n f a s s u n g Wir beschreiben den ersten unstrittigen fossilen Nachweis einer Stomatopoden-Larve, da alle früher so gedeu-teten Funde als Thylacocephala identifiziert wurden. Das Fossil stammt aus den oberjurassischen Solnhofener Plattenkalken (Bayern) und wurde ausführlich mit Hilfe eines UV-Mikroskops dokumentiert. Dabei wurden über 700 Einzelaufnahmen gemacht. Diese wurden zu einem einzigen großen Bild zusammengefügt, wobei sowohl Aufnahmen in Z-Richtung als auch in der X-Y-Ebene verrechnet wurden. Das Endprodukt ist ein hoch auflösendes Gesamtbild hoher Tiefenschärfe, das auch feinste Details zeigt. Das Fossil besitzt eine tri-flagellate Antennula und sub-chelate Raubbeine; beide Merkmale weisen das Fossil als Stomatopoden aus. Eindeutige Larvenmerkmale sind das lange unbewegliche Rostrum sowie die vom Schild überdeckten Thoracomeren. Das Fossil gehört wahrschein-lich zur Gattung Sculda, jedoch vermutlich nicht zur häufigen Art S. pennata. Ob es eine neue Spezies darstellt, ist momentan noch unklar.
Article
Here we present a set of methods for documenting (exo-)morphology by applying autofluorescence imaging. For arthropods, but also for other taxa, autofluorescence imaging combined with composite imaging is a fast documentation method with high-resolution capacities. Compared to conventional micro- and macrophotography, the illumination is much more homogenous, and structures are often better contrasted. Applying different wavelengths to the same object can additionally be used to enhance distinct structures. Autofluorescence imaging can be applied to dried and embedded specimens, but also directly on specimens within their storage liquid. This has an enormous potential for the documentation of rare specimens and especially type specimens without the need of preparation. Also for various fossils, autofluorescence can be used to enhance the contrast between the fossil and the matrix significantly, making even smallest details visible. 'Life-colour' fluorescence especially is identified as a technique with great potential. It provides additional information for which otherwise more complex methods would have to be applied. The complete range of differences and variations between fluorescence macrophotography and different types of fluorescence microscopy techniques are here explored and evaluated in detail. Also future improvements are suggested. In summary, autofluorescence imaging is a powerful, easy and fast-to-apply tool for morphological studies.
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The true crabs, the Brachyura, are generally divided into two major groups: Eubrachyura or 'advanced' crabs, and Podotremata or 'primitive' crabs. The status of Podotremata is one of the most controversial issues in brachyuran systematics. The podotreme crabs, best recognised by the possession of gonopores on the coxae of the pereopods, have variously been regarded as mono-, para- or polyphyletic, or even as non-brachyuran. For the first time, the phylogenetic positions of the podotreme crabs were studied by cladistic analysis of small subunit nuclear ribosomal RNA sequences. Eight of 10 podotreme families were represented along with representatives of 17 eubrachyuran families. Under both maximum parsimony and Bayesian Inference, Podotremata was found to be significantly paraphyletic, comprising three major clades: Dromiacea, Raninoida, and Cyclodorippoida. The most 'basal' is Dromiacea, followed by Raninoida and Cylodorippoida. Notably, Cyclodorippoida was identified as the sister group of the Eubrachyura. Previous hypotheses that the dromiid crab, Hypoconcha, is an anomuran were unsupported, though Dromiidae as presently composed could be paraphyletic. Topologies constrained for podotreme monophyly were found to be significantly worse (P < 0.04) than unconstrained topologies under Templeton and S-H tests. The clear pattern of podotreme paraphyly and robustness of topologies recovered indicates that Podotremata as a formal concept is untenable. Relationships among the eubrachyurans were generally equivocal, though results indicate the majoids or dorippoids were the least derived of the Eubrachyura. A new high level classification of the Brachyura is proposed.
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This year, the 11th International Symposium on Wearable Computers returned to the city where it began: Boston, Massachusetts. ISWC is the premier conference in wearable computing, reporting the latest advances in research and technology. As in previous years, attendees came both from academia and industry, representing a broad spectrum of nationalities and technical interests. The year 2008's program emphasized gesture and activity recognition but also reported on power considerations, augmented reality, evaluation, and new interaction modalities, among other topics.