查看更多>>摘要：Lateral arm plates, the spine-bearing plates of the ophiuroid arm skeleton, have long been assumed to display sufficient morphological diversity to be used for species identifications in ophiuroid micropalaeontology. As a consequence, many new brittle-star species have been described on the basis of isolated fossil lateral arm plates. A substantial lack of information on the morphological variability of lateral arm plates in respect of taxon concepts, however, has led to increasing confusion over species limits and excessive extensions of stratigraphic species ranges. In this study, we therefore performed a detailed assessment of the variability of lateral arm plate morphology within and between species in order to test to what extent isolated lateral arm plates can be used for species identifications. To this end, we investigated the morphological variability of lateral arm plates within species according to ontogenetic changes and according to the position of the plates along the arm. Furthermore, we examined the lateral arm plates of 56 Recent species, belonging to 27 genera and 10 families, and systematically assessed their morphology in the light of currently accepted taxon concepts. The results of this study demonstrate that lateral arm plate morphology is in accordance with most family, genus and species limits. Some of the currently accepted taxon concepts, including the affinities between the Ophiacanthidae and Ophiocomidae, however, are challenged by lateral arm plate morphology. Differences in lateral arm plate morphology between taxa are the most conspicuously displayed by adult proximal lateral arm plates, as a consequence of their high degree of differentiation compared to distal or juvenile lateral arm plates. Differences at species level, often pertain to characters which were considered to be within-species variation in previous micropalaeontological works, suggests that species identifications based on isolated fossil lateral arm plates require a much more detailed and carefulmorphological assessment. Some of the species studied herein displayed indistinguishable lateral arm plate morphologies, but belonged to the same genus in all cases. Our study endorses the use of isolated fossil lateral arm plates for taxonomic interpretations in ophiuroid micropalaeontology, including species identifications and the creation of new taxa, providing that descriptions are based on pristinely preserved adult proximal LAPs, described and illustrated using SEM-pictures of both the externaland internal sides of the plate.
SEID MOHAMMAD BAGHER NABAVICHRISTOPHER GLASBYSHETAV YOUSEFIHASAN RAHIMIAN...
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查看更多>>摘要：The species composition and distribution patterns of Nereididae (Annelida: Polychaeta) from the north coast of Gulf of Oman were investigated. Specimens were collected from ten intertidal sites along the Iranian coast, including mangrove, muddy, boulder and rocky, coral and sandy-rocky shore habitats. Eight species of Nereididae were identified: Leonnates decipiens Fauvel, Nereis coutieri Gravier, Neanthes deplanata Mohammad, Perinereis nuntia (Savigny), Perinereis het-erodonta Gravier, Perinereis cultrifera (Grube), Perinereis horstiGravier and Pseudonereis trimaculata Horst. The eight species are redescribed and two Perinereis species, P. heterodonta and P. horsti, currently junior synonyms of P. nuntia and P. vancaurica (Ehlers) respectively, areraised from synonymy. All reported species are new records for the Gulf of Oman, bringing the known total number of species in the family to twelve; P. trimaculata is also a new record for the Arabian Sea-Arabian Gulf region. Nereidid diversity within the region is comparable to other Indo-Pacific coastal regions, and higher than other parts of the world.
查看更多>>摘要：The genus Lysiteles was established by Simon (1895) for the type species Lysiteles catulus from India. At present, it includes 56 species (Platnick 2011) that are mainly found in southern and eastern Asia (Ono 1988). Lysiteles spiders are small thomisids with body length 2.0-4.5 mm, therefore, it is difficult to collect them in the field. Almost 50% of the known species are described from single sex (Tang et al. 2008). A total of 41 species have been described from China, among them 18 species are single sex (Li & Wang 2011; Song & Zhu 1997). Xysticus minimus was described firstly by Schenkel (1953) for a male specimen from southeast of Gansu Province, China. Then Ono (1979) transferred it to the genus Lysiteles. Song and Wang (1991) described a newspecies named Lysiteles xianensis, but Song (1995) synonymized it with Lysiteles minimus (Schenkel 1953). While studying the Lysiteles specimens collected from Liupan Mountains, Ningxia Hui Autonomous Region, China, we found pairs of male and female Lysiteles specimens in the same locality. We identified the male as L. minimus. The female specimens have habitus and markings very similar to the male of L. minimus, and the characters of epigynum conform to the genus Lysiteles. We therefore identified itas the female of L. minimus, and describe it here.
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