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Light micrographs showing overviews of Echinoderes juliae sp. nov., holotype, ? (A-B) (NHMD-213666) and paratype, ? (C) (NHMD-213689). A. Dorsal overview. B. Ventral overview. C. Lateral view. Glandular cell outlets type 2 are marked with dashed white circles.
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The bathyal kinorhynch fauna along the Northwest American continental rise is explored, with emphasis on species of Echinoderidae Zelinka, 1894. Seven species of Echinoderes Claparède, 1863 are described as new to science: E. anniae sp. nov., E. dubiosus sp. nov., E. hamiltonorum sp. nov., E. hviidarum sp. nov., E. juliae sp. nov., E. lupherorum sp...
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Citations
... Tergal extensions of segment 11 can vary in both shape and length between species of Echinoderidae. This character is considered diagnostic in some Echinoderes Claparède, 1863, including the Echinoderes spinifurca-group (Landers & Sørensen 2018;Sørensen et al., 2018). Due to the growing importance of this character in the taxonomy of some Echinoderidae, we propose to take its measure from the base of the extension (i.e. ...
Taxonomic studies of Kinorhyncha follow a standardised structure, which is extremely useful in many aspects, such as making it easier to read and compare the different species descriptions. However, the morphological measurements methods, essential for formal description of species, may differ according to the authors. In the present contribution, we propose a standardised method of taking and representing the measurements, with the aim of obtaining comparable and repeatable morphometric results. Additionally, we propose an online repository to make the measurements accessible to all researchers in the same format, facilitating future comparisons and studies. Finally, a glossary that compiles and defines all the measurements that may be included in Kinorhyncha descriptions is presented.
... Five middorsal spines and lateroventral tubes/spines on segments 5 to 9 are shared with 46 congeners (Yamasaki et al., 2020). However, when we combine these characters with the presence of glandular cell outlets type 2 in subdorsal, laterodorsal, midlateral/sublateral and ventrolateral positions on segment 2, we shorten the possibilities to 10 species, i.e., Echinoderes angustus Higgins & Kristensen, 1988, Echinoderes aquilonius Higgins & Kristensen, 1988, Echinoderes beringiensis Adrianov & Maiorova, 2022, Echinoderes cernunnos Sørensen et al., 2012, Echinoderes galadrielae Grzelak and Sørensen, 2022, Echinoderes juliae Sørensen et al., 2018, Echinoderes obtuspinosus Sørensen et al., 2012, Echinoderes pennaki Higgins, 1960, Echinoderes romanoi Landers & Sørensen, 2016, and Echinoderes xalkutaat Cepeda et al., 2019(Higgins 1960Sørensen et al., 2012;Landers & Sørensen 2016;Grzelak & Sørensen 2018;Herranz et al., 2018;Sørensen et al., 2018;Cepeda et al., characteristic long and spiniform tergal extensions, while E. romanoi and E. xalkutaat are (in addition to their lack of gco2 on segment 4) much smaller and show different shapes of tergal extensions (Sørensen et al., 2012;Landers & Sørensen 2016;Cepeda et al., 2019). E. juliae and E. obtuspinosus, although possessing a subdorsal pair of glandular cell outlets type 2 on segment 4, have an extra pair of glands on segment 3 (E. ...
The kinorhynch species Echinoderes remanei (Blake, 1930) is redescribed herein, based on the material housed in the National Museum of Natural History, Smithsonian Institution in Washington D.C as well as specimens collected at several other sites in the Northern Hemisphere. E. remanei is characterized by the presence of middorsal spines on segments 4 to 8 and lateroventral spines on segments 6 to 9; four pairs of glandular cell outlets type 2 on segment 2 (subdorsal, laterodorsal, sublateral, and ventrolateral), and one pair on segment 4 (subdorsal), 5 (midlateral), 8 (sublateral) and 10 (laterodorsal); lateroventral tubes on segment 5; and by sexual dimorphism expressed in lateral terminal spine lengths (in females, the lateral terminal spines are on about half as long as those in males). The study also reveals that the two other species, Echinoderes tubilak Higgins & Kristensen, 1988 and Echinoderes svetlanae Adrianov, 1999 in Adrianov & Malakhov (1999) are conspecific with E. remanei. Therefore, E. tubilak and E. svetlanae are proposed as junior synonyms of E. remanei and are synonymized with E. remanei (Blake, 1930).
... The spine pattern with middorsal spines on segments 6 and 8 is rare among species of Echinoderes, and is shared with only three species, i.e., E. daenerysae, E. hviidarum Sørensen et al., 2018 andE. ultraabyssalis Adrianov &Maiorova, 2019, and an undescribed species, Echinoderes sp. 1, from the Atacama Trench (Grzelak & Sørensen 2018;Sørensen et al. 2018;Adrianov & Maiorova 2019;Grzelak et al. 2021). Furthermore, E. gandalfi sp. ...
... Furthermore, the presence of laterodorsal tubes on segment 9 is also a rather rare feature among echinoderids. This trait has previously been described for only four species, i.e., E. belenae, E. daenerysae, E. hviidarum, E. ultraabyssalis and in the yet undescribed Echinoderes sp. 1 from the Atacama Trench (Pardos et al. 2016b;Grzelak & Sørensen 2018;Sørensen et al. 2018;Adrianov & Maiorova 2019;Grzelak et al. 2021). The latter four cannot in any way be confused with E. frodoi sp. ...
... nov., and E. aragorni sp. nov.) having middorsal spines on segments 4, 6 and 8, but can easily be distinguished from all other congeners by its unique patterns of spines, tubes and glandular cell outlets type 2. The most exclusive feature of E. legolasi is the presence of four pairs of glandular cell outlets type 2 on segment 2. This character is shared only with one other species, i.e., E. anniae described by Sørensen et al. (2018) from the United States west coast. Except for the identical pattern of cuticular structures on segment 2, both species also share the presence of glandular cell outlets type 2 in midlateral/sublateral positions on segments 1 and 8. ...
Limited data are available for the kinorhynch fauna from the Southern Hemisphere, with little or no data from New Zealand. Here, we provide a first comprehensive overview of the diversity of mud dragons, with an emphasis on species of Echinoderes from the continental slope of New Zealand, from a variety of habitats such as slopes, canyons and seamounts located in the Hikurangi Margin region. The study revealed fifteen species of Echinoderes. Of these, ten are described as new to science: E. aragorni sp. nov., E. blazeji sp. nov., E. dalzottoi sp. nov., E. frodoi sp. nov., E. galadrielae sp. nov., E. gandalfi sp. nov., E. landersi sp. nov., E. leduci sp. nov., E. legolasi sp. nov. and E. samwisei sp. nov. Moreover, Echinoderes juliae Sørensen et al., 2018, Echinoderes sp. aff. E. balerioni, Echinoderes sp. aff. E. galadrielae/beringiensis, Echinoderes sp. aff. E. lupherorum and Echinoderes sp. aff. E. unispinosus are reported in the investigated region. The most abundant among all was E. gandalfi sp. nov., but it was found only in canyons. Interestingly, the second most common species was E. juliae that was found at several stations in canyons, seamount and on the slope. This species is one of the deep-sea species originally found on the abyssal plain off Oregon and along the continental rise off California, Northeast Pacific, recorded in polymetallic nodules in the tropical eastern Pacific, and recently found on the abyssal plains off Chile, east of the Atacama Trench. These findings, together with records of Echinoderes sp. aff. E. lupherorum and Echinoderes sp. aff. E. unispinosus indicate that, despite their low dispersal abilities, kinorhynchs, similar to other meiofaunal species, may exhibit a wider distribution pattern than previously assumed. The number of recorded species and numerous new species show that New Zealand sediments not only are inhabited by a diverse kinorhynch fauna, but Echinoderes, the most speciose genus, still holds much to discover.
... Tergal extensions of segment 11 can vary in both shape and length between species of Echinoderidae. This character is considered diagnostic in some Echinoderes Claparède, 1863, including the Echinoderes spinifurca-group (Landers & Sørensen 2018;Sørensen et al., 2018). Due to the growing importance of this character in the taxonomy of some Echinoderidae, we propose to take its measure from the base of the extension (i.e. ...
The formal taxonomic descriptions of the phylum Kinorhyncha were standardized during the 60s in order to ease descriptions and comparison between congeners. Morphometric
measures have turned out to be useful not only in distinguishing between kinorhynch
species, but also explaining their biogeographic distribution; however, the measurement
uptake methods and the structures to be measured have never been standardized. Thus,
different authors uptake slightly different measurements, sometimes giving no-comparable results. We propose a consensus way to take the measurements in order to minimize differences due to observers. Moreover, we updated the structures required for the descriptions of the new species.
... Kinorhynchs are worldwide distributed, usually inhabiting the upper few centimeters of marine and estuarine sediments from littoral zone to the hadal depths up to 9500 m (Adrianov and Maiorova, 2019;Neuhaus, 2013;Sørensen et al., 2018). They have also been found in diverse extreme, deep-sea environments, including stromatolites, polymetallic nodule fields, cold seeps of methane and hydrogen sulfide, mud volcanos (including active ones), hydrothermal vents, bacterial mats, and seamounts and even on an active marine volcano (Adrianov and Maiorova, 2020;Á lvarez-Castillo et al., 2015;Bright et al., 2010;Lampadariou et al., 2013;Mullineaux et al., 2012;Neuhaus, 2013;Olu et al., 1997;Robinson et al., 2004;Sánchez et al., 2019;Sommer et al., 2007;Vanreusel et al., 1997;Yamasaki et al., 2019;Zeppilli et al., 2012). ...
... Current taxonomic contributions have clearly shown the taxonomic significance of these structures, well visible with both with LM and SEM techniques and becoming a standard element in taxonomic descriptions of echinoderids (Sørensen et al., 2020). There are only nine species of Echinoderes with four pairs of glandular cell outlets type 2 on trunk segment 2 and a single pair in sublateral position on trunk segment 8: E. anniae Sørensen et al., 2018;E. angustus Higgins et Kristensen, 1988;E. ...
... nov.) and by the presence of glandular cell outlets type 2 also on the first trunk segment (absent in E. beringiensis sp. nov.) (see Sørensen et al., 2018). Echinoderes cernunnos from the Korean Strait (96 m deep) may be distinguished from E. beringiensis sp. ...
A new species of echinoderid kinorhynch, Echinoderes beringiensis sp. nov., collected from bacterial mats at the deep-sea cold methane seepages area on the Chukchi slope (Bering Sea, NW Pacific), is described using light and scanning electron microscopy. This new representative of the most diverse kinorhynch genus is characterized by its unique arrangement of spines, tubes and glandular cell outlets and cuticular plates composition on trunk segment 11, thus being distinguished from other congeners. Modified glandular cell outlets type 2 are present in subdorsal, laterodorsal, sublateral and ventrolateral positions on trunk segment 2; in midlateral position on trunk segment 5; in sublateral position on trunk segment 8 in males, and in midlateral and sublateral position in female. Acicular spines are present in middorsal position on trunk segments 4–8, and in lateroventral position on trunk segments 6–9. Tubes are present in lateral accessory position on trunk segment 5. Trunk segment 11 has two tergal and two sternal cuticular plates. Echinoderes beringiensis sp. nov. constitutes the first kinorhynch species described from extreme, deep-sea environments of cold methane seepages in the Pacific Ocean, and the second representative of the Kinorhyncha known from the Bering Sea.
... Echinoderes goku sp. nov. shares the presence of three middorsal spines on segments 4, 6 and 8 with 27 other congeners (Table 4; Higgins 1966aHiggins , b, 1967Higgins , 1982Higgins , 1983Higgins , 1985Higgins & Kristensen 1988;Huys & Coomans 1989;Pardos et al. 1998Pardos et al. , 2016aSørensen 2006;Herranz et al. 2014Herranz et al. , 2018Sørensen & Landers 2014;Landers & Sørensen 2016;Grzelak & Sørensen 2018Sørensen et al. 2018;Yamasaki et al. 2018bYamasaki et al. ,c, 2019Cepeda et al. 2019b;Sánchez et al. 2019), however, the new species can be distinguished from all of them by its unique spine/tube pattern: subdorsal tube on segment 2, sublateral to midlateral tube on segments 7 and 9, lateral accessory tube on segment 8, lateroventral spine/tube on segments 5-9 and ventrolateral tube on segment 2. This combination of spines/tubes is not found in any other Echinoderes species (comp. Table 4 and references therein also for characters in addition to spines and tubes). ...
... nov. possess a ventrolateral spine/tube on segment 2, a lateroventral spine/tube on segments 5-9, and a lateral accessory spine/tube on segment 8, which excludes the following species for further consideration: E. anniae Sørensen et al., 2018 (lacking a ventrolateral spine/tube on segment 2 and a lateral accessory spine/tube on segment 8), E. apex Yamasaki et al., 2018b, E. hamiltonorum Sørensen et al., 2018, E. joyceae Landers & Sørensen, 2016, E. multiporus Yamasaki et al., 2018c (all four species lacking a lateral accessory spine/tube on segment 8), E. arlis Higgins, 1966b (lacking a ventrolateral spine/tube on segment 2, a lateroventral spine/tube on segment 5, and a lateral accessory spine/tube on segment 8), E. bermudensis Higgins, 1982 (lacking a lateroventral spine/tube on segment 5 and a lateral accessory spine/tube on segment 8), E. meteorensis Yamasaki et al., 2018b, E. shenlong Sánchez et al., 2019 (both species lacking a ventrolateral spine/tube on segment 2), E. riceae Herranz et al., 2014 (lacking a lateroventral spine/tube on segment 6), E. schwieringae (exhibiting a lateroventral instead of a ventrolateral spine/tube on segment 2 and lacking a lateral accessory spine/tube on segment 8), and E. skipperae Sørensen & Landers, 2014 (lacking a lateroventral spine/tube on segments 6 and 7) ( Table 4). ...
... unispinosus) occurred in both female and male of E. apex and E. unispinosus, a subcuticular conical structure plus a cylindrical cuticular reinforcement at the base of a tube was found in E. meteorensis, a subcuticular cylindrical cuticular reinforcement connected with a tube or not was traced in E. capitatus, E. ferrugineus, and E. pilosus, the latter also with an external cylindrical cuticular sheath, and no subcuticular structure were observed in the remaining species investigated here. More recent and detailed studies about these as well as about other echinoderid species did not report any of these structures (Neuhaus & Blasche 2006;Ostmann et al. 2012;Herranz & Leander 2016;Sørensen et al. 2018Sørensen et al. , 2020Yamasaki et al. 2018bYamasaki et al. , 2018cYamasaki & Dal Zotto 2019;Cepeda et al. 2019a). The specimens of both E. goku sp. ...
Echinoderes goku sp. nov. is described from adult and juvenile specimens in samples collected from the Argentinean continental shelf in March 2019 during the campaign of the Motorsailer "Bernardo Houssay", based on light and scanning electron microscopy studies. Echinoderes goku sp. nov. is differentiated from other species by its unique spine and tube pattern: (1) middorsal spine on segments 4, 6, and 8, (2) spine in lateroventral position on segments 6-9, (3) tube present in subdorsal position on segment 2, sublateral to midlateral position on segments 7 and 9, lateral accessory position on segment 8, lateroventral position on segment 5 and ventrolateral position on segment 2. Additionally, this species (4) lacks type-2 gland cell outlets and female-specific papillae or subcuticular funnel-like structures. (5) The male possesses a sublateral tube on segment 10 with a basal cylindrical reinforcement structure and three penile spines on segment 11, whereas the female lacks penile spines but reveals a lateral terminal accessory spine on segment 11 and on segment 10 lacks a subdorsal tube but possesses instead a sublateral fringe on the surface connected with a subcuticular conical structure and a basal cylindrical reinforcement structure. Among several juvenile specimens, one was captured in the process of moulting from the last juvenile stage to the female. Whereas the last juvenile stage revealed a sublateral tube on segment 10, the moulting female lacked this tube and showed a conical subcuticular structure with a basal cylindrical reinforcement structure instead. A cylindrical reinforcement structure at the base of a tube and a subcuticular conical structure have not been reported before for Kinorhyncha, and 14 selected species of Echinoderidae available for study were screened for these characters in order to get a first idea of their possible taxonomic importance. This article reports about the second species of Echinoderes from Argentinean waters.
... The numerous similarities between Echinoderes sp. and E. charlotteae obviously leaves us with the question whether they should be considered conspecific. For many years species of Echinoderes were all considered to show rather regional and limited distribution patterns, but recent studies have indicated that at least deep-sea species could have much wider, even cross-oceanic, distributions (Sørensen et al., 2018, Yamasaki et al., 2018b, Cepeda et al., 2020, Grzelak et al. 2021). However, we still find conspecifity of Echinoderes sp. and E. charlotteae rather doubtful. ...
... As reported in some recent papers, kinorhynchs are very common and numerous in the abyss and even in the hadal zone (see Neuhaus 2013;Adrianov & Maiorova 2015Sørensen et al. 2018;Yamasaki et al. 2018aYamasaki et al. , 2018bYamasaki et al. , 2018c. Nevertheless, information on the species composition in the deep sea is still very limited. ...
... Some species of Echinoderes are also characterized by very long dagger-like tergal extensions. For instance, E. sylviae Landers & Sørensen, 2018 from the Gulf of Mexico, West Atlantic, and E. lupherorumSørensen et al., 2018 and E. kohni Varney, Funch, Kocot & from the North-East Pacific have tergal extensions about 7 and 8% of TL, respectively (seeSørensen et al. 2018;Varney et al. 2019). In E. higginsiHuys & Coomans, 1989 from the North Sea and E. spinifurcaSørensen et al., 2005 from the Gulf of Mexico these extensions constitute about 11% of TL (seeHuys & Coomans 1989;Sørensen et al. 2005). ...
... Some species of Echinoderes are also characterized by very long dagger-like tergal extensions. For instance, E. sylviae Landers & Sørensen, 2018 from the Gulf of Mexico, West Atlantic, and E. lupherorumSørensen et al., 2018 and E. kohni Varney, Funch, Kocot & from the North-East Pacific have tergal extensions about 7 and 8% of TL, respectively (seeSørensen et al. 2018;Varney et al. 2019). In E. higginsiHuys & Coomans, 1989 from the North Sea and E. spinifurcaSørensen et al., 2005 from the Gulf of Mexico these extensions constitute about 11% of TL (seeHuys & Coomans 1989;Sørensen et al. 2005). ...
A new species of echinoderid kinorhynchs, Echinoderes xiphophorus sp. nov. collected from oxidized brown silt at the deepest depression in the Sea of Japan, North-West Pacific, is described and illustrated using light and electron microscopy. This new representative of the most speciose kinorhynch genus is characterized by the unique set of spines and tubes and can easily be distinguished from most of its congeners. The second trunk segment bears three pairs of tubes in subdorsal, midlateral and ventrolateral position in both sexes; one pair of tubes on trunk segment 5 in lateroventral position and on trunk segment 8 in sublateral position; aciculate lateroventral spines on trunk segments 6–9; aciculate middorsal spines on trunk segments 4, 6, 8. This species is well recognized by very long tergal extensions of the posteriormost segment, some of the longest within the family Echinoderidae. Males of Echinoderes xiphophorus sp. nov. are well distinguished from all the congeners by extremely long sword-like appendages dorsally to three pairs of penile spines. The species constitutes the first deep-sea representative of the Echinoderidae in the Sea of Japan and the deepest representative of the Kinorhyncha in this sea.
... Sánchez et al. (2014a,b) described three additional species, i.e., Mixtophyes abyssalis Sánchez et al. (2014a,b), Cristaphyes nubilis (Sánchez et al., 2014a,b), and Krakenella farinelli (Sánchez et al., 2014a,b), from the Guinea Basin, at depths between 5100-5175 m. The remaining and more recent reports of identified abyssal kinorhynchs are restricted to five areas: (1) abyssal plains, 3100-3300 m, around North Atlantic seamounts, from where Yamasaki et al. (2019) describe Echinoderes kaempfae Yamasaki et al., 2019; (2) the East Mediterranean, 675-4403 m, from where Yamasaki et al. (2018a) describe Echinoderes pterus Yamasaki et al., 2018a,b; (3) abyssal plains, 3351-5766, in the vicinity of the Kuril-Kamchatka Trench, from where Adrianov and Maiorova (2015 describe Cristaphyes abyssorum (Adrianov and Maiorova, 2015), Condyloderes kurilensis Adrianov and Maiorova (2016), Meristoderes okhotensis Adrianov and Maiorova (2018a), and Parasemnoderes intermedius Adrianov and Maiorova (2018b); (4) the abyssal plains, 3250-3853 m, off the Northwest American continental slope, from where Sørensen et al. (2018) describe E. anniae, E. dubiosus, E. hamiltonorum, E. juliae, E. lupherorum, E. hviidarum, E. yamasakii, and Sørensen et al. (2018 report three additional known kinorhynch species, E. cf. unispinosus Yamasaki et al. (2018a,b), Fissuroderes higginsi Neuhaus and Blasche (2006), and C. kurilensis; (5) the Clarion-Clipperton Fracture Zone, 4319-5012 m, in the tropical East Pacific, from where Sánchez et al. (2019) describe Cephalorhyncha polunga, Echinoderes shenlong, and Meristoderes taro. ...
... All specimens were identified to species level, except for the juveniles. Identification of kinorhynchs to species level was based on the relevant taxonomic literature (Herranz et al., 2018;Sørensen et al., 2018;Yamasaki et al., 2018bYamasaki et al., , 2020Adrianov and Maiorova, 2019). ...
... nov. shows a much closer general resemblance with E. bathyalis Yamasaki et al. (2018a,b) and E. dubiosus Sørensen et al. (2018). Both are deep-water species, described from East Atlantic (> 2500 m water depth) and North-Eastern Pacific (> 3500 m water depth), respectively Yamasaki et al., 2018b). ...
Deep-sea trenches are one of the last frontiers for deep-sea exploration and represent a large reservoir of undiscovered biodiversity. This applies in particular to organisms belonging to smaller-size classes, such as meiofauna. Among different meiofauna taxa, kinorhynchs represent a large gap in our knowledge about global marine biodiversity in general, but primarily in extreme deep-sea environments. Out of the more than 300 known mud dragon species, only a single species has ever been described from hadal depths (> 6000 m), i.e., Echinoderes ultraabyssalis from the Kuril-Kamchatka Trench. The results presented in this paper are based on material collected during a research expedition in 2018 investigating the Atacama Trench environment. We provide a first overview and comparison of the diversity and abundance of mud dragons in the Atacama Trench, the adjacent abyssal plain and continental slope off Chile. The study revealed six species of Echinoderes. Of these, Echinoderes mamaqucha sp. nov. is described as a new species and morphological data of three undescribed species are given. Because of the low number of available specimens, we provide only a brief description of these three species and comparison with their morphologically closest congeners, but formal descriptions are not given. Moreover, Echinoderes juliae and Echinoderes pterus were also recovered. Echinoderes juliae was described from the abyssal plain off Oregon and along the continental rise off California, at 2702 to 3679 m depth. Echinoderes pterus is known from the high Arctic, the North Atlantic, and the Mediterranean Sea, and has also been reported to show a wide bathymetric distribution, from 675 to 4403 m. Interestingly, E. mamaqucha sp. nov. dominated at the trench stations and it reached its highest abundance at the deepest station, at 8085 m water depth. The only other single individual that was found in the Atacama Trench was Echinoderes sp.1. The remaining four species were all found at the abyssal and slope stations. The obtained results seem to confirm previous hypotheses about geographic isolation of deep-sea trenches and relatively low connectivity with other habitats, reflected by limited diversity of sediment dwelling fauna, particularly in the deepest parts of trenches.
... The present study, that just started out with a species that needed to be identified, but concluded with a revision of an entire species group and the discovery of two new species, stresses the importance of high quality descriptions and access to type material. NHMD-115257, NHMD- Specimens for scanning electron microscopy (SEM) were transferred to distilled water, and cleaned by blowing bubbles through a solution of water and a small amount of liquid dish washing detergent (see Sørensen et al. 2018 for a more detailed description of the method). After an additional wash in clean distilled water, the specimens were transferred to SEM metal containers that were closed with 60 µm nylon net in each end. ...
... capitatus (Zelinka, 1928) with nearly constant segment width throughout the trunk (Zelinka 1928;Huys & Coomans 1989;Sørensen et al. 2000;Pardos et al. 2016a;Yamasaki & Dal Zotto 2019). We also see species, such as E. anniae Sørensen et al., 2018, with very thin pachycycli, that differ considerably from species with extraordinary strong pachycycli, as seen in E. skipperae Sørensen & Landers 2014(Sørensen & Landers 2014Sørensen et al. 2018). In addition to these differences that on one hand are obvious, but on the other hand difficult to quantify, we see much variation in distribution of glandular cell outlets, patterns in cuticular hair cover, shapes of tergal extensions, etc. ...
... capitatus (Zelinka, 1928) with nearly constant segment width throughout the trunk (Zelinka 1928;Huys & Coomans 1989;Sørensen et al. 2000;Pardos et al. 2016a;Yamasaki & Dal Zotto 2019). We also see species, such as E. anniae Sørensen et al., 2018, with very thin pachycycli, that differ considerably from species with extraordinary strong pachycycli, as seen in E. skipperae Sørensen & Landers 2014(Sørensen & Landers 2014Sørensen et al. 2018). In addition to these differences that on one hand are obvious, but on the other hand difficult to quantify, we see much variation in distribution of glandular cell outlets, patterns in cuticular hair cover, shapes of tergal extensions, etc. ...
Thirteen species of Echinoderes with nearly identical spine/tube patterns, and apparently similar tergal extensions were re-examined and compared. Based on this, redescriptions and/or emended species diagnoses are provided for Echinoderes aureus, E. dujardinii, E. gerardi, E. imperforatus, E. pacificus, E. pilosus, E. sensibilis, E. sublicarum and E. worthingi, and new details about cuticular structures are added for E. kozloffi and E. gizoensis. The new information derived from the redescriptions, and the subsequent comparative studies revealed that: 1) the holotype of Echinoderes lanceolatus is identical with the types of Echinoderes aureus, and E. lanceolatus is thus a junior synonym of E. aureus; other potentially synonymous species that should be addressed further in the future include: E. dujardinii + E. gerardi; E. imperforatus + E. sensibilis, and E. pacificus + E. sublicarum; 2) the paratypes of E. lanceolatus represented a different yet undescribed species, here described as E. songae Sørensen & Chang sp. nov.; 3) a comparison with literature information about E. ehlersi showed that the species is so insufficiently described that a redescription of topotype material is required before the species should be considered for taxonomic comparison; 4) specimens from the Andaman Islands, India, that previously have been reported as Echinoderes cf. ehlersi represent two different undescribed species, of which one is described as E. chandrasekharai Sørensen & Chatterjee sp. nov. and the other is left undescribed due to the limited material available; 5) out of a total of fifteen addressed species, it is proposed that eleven represent a putatively monophyletic group that is named the Echinoderes dujardinii group. The group includes following species: E. dujardinii, E. ehlersi, E. gerardi, E. imperforatus, E. kozloffi, E. sensibilis, E. pacificus, E. sublicarum, E. songae Sørensen & Chang sp. nov., E. chandrasekharai Sørensen & Chatterjee sp. nov., and Echinoderes sp. from the Andaman Islands, and is supported by a similar spine/tube pattern (except for variation regarding the presence of lateral accessory tubes on segment 8); generally short middorsal spines, especially on segments 4 to 6; glandular cell outlets type 1 always present in middorsal positions on segments 1 to 3, and in subdorsal positions on segments 4 to 9; glandular cell outlets type 2 always present in laterodorsal or midlateral positions on segment 8, and sometimes in same positions on segment 9 but never at any other segments or positions; female papillae always present on sternal plates of segments 7 and 8, and occasionally also on segment 6; tergal extensions well-spaced, triangular, gradually tapered cones, and pectinate fringes of sternal extensions are differentiated into seta-like tufts. The comparisons furthermore showed potential taxonomic significance of two echinoderid character traits that previously have been slightly neglected as diagnostic traits, namely the presence and appearance of female papillae, and the dorsal pattern of glandular cell outlets type 1. Female papillae may occur on the sternal plates of segments 6 to 8, but the positions may differ from ventrolateral to ventromedial, and the morphology of the intracuticular substructure also differ at species level. Information about position and morphology of female papillae proved helpful for species recognition, but it might also provide information of phylogenetic importance. Analyses of glandular cell outlet type 1 patterns on the dorsal sides of segments 1 to 9 in species of Echinoderidae, revealed several apparently unique or rare patterns, but also three distinct patterns that applied to larger groups of species. One pattern is the one present in all species of the E. dujardinii group, whereas the other two common patterns included 1) middorsal outlets on segments 1 to 3, and paradorsal outlets on segments 4 to 9 (found in 27 species), and 2) middorsal outlets on segments 1 to 3, 5 and 7, and paradorsal outlets on segments 4, 6 and 8 to 9 (found in 27 species)
